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Hashim, Zeina. "Semiconducting polymer nanospheres : organic alternatives to inorganic quantum dots?" Thesis, King's College London (University of London), 2013. https://kclpure.kcl.ac.uk/portal/en/theses/semiconducting-polymer-nanospheres(c39fdbe6-f281-4472-94aa-d8e44f834b2e).html.
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Semiconducting polymer nanospheres are organic conjugated polymer nanoparticles which are synthesized from benign materials and exhibit excellent fluorescence properties. The nanoparticles are generally larger than inorganic quantum dots with a relatively broad size distribution. Quantum dots, on the other hand, which have extensively been developed and synthesized with precise and narrow distributions of a few nanometers in dimensions, are now being widely investigated as bio-imaging agents, despite the rising concerns about their toxic compositions. Therefore, advances in the synthesis of the organic nanoparticles and investigations into their suitability as alternatives to quantum dots need to be explored. The ‘size problem’ of semiconducting polymer nanospheres – polymer particles are significantly larger than quantum dots – was first tackled in this work. With modifications to the miniemulsion-evaporation synthesis method, narrowly distributed quantum dot-sized nanoparticles with diameters as small as 2 nm were synthesized. These organic nanoparticles which were capped/entwined with poly(ethylene) glycol (PEG), a Food and Drug Administration (FDA) approved surfactant, were found to conserve most of the optical properties of their constituent polymers, and are therefore expected to be useful in bio-imaging applications similar to their larger counterparts. A second nanoparticle system with a dual-modality was then prepared; semiconducting polymer nanospheres capped/entwined with three amphiphilic lipids one of which was gadolinium – diethylene triamine pentacetate, a Magnetic Resonance Imaging (MRI) active ligand. These bimodal nanoparticles also maintained their optical properties, were readily taken up by two cell lines, were distinguishable from the auto-fluorescence of animal tissue, and were found to be MRI-active as revealed by their MRI relaxivity measurements. Finally, the optimized organic nanoparticles and similarly coated quantum dots were investigated for their potential to interact with human blood components, a physiological system which may be very relevant for semiconducting polymer nanospheres used as medical diagnostic agents. The preliminary ex-vivo studies performed revealed that similarly coated organic nanoparticles and quantum dots did not induce platelet aggregation or alter aggregation behaviour in response to a physiological agonist. Further, no evidence of platelet activation, neutrophil activation or increases in platelet-monocyte adhesion was observed. This implied that introduction of the nanoparticles to the blood stream at the concentrations tested may not elicit acute pro-inflammatory effects or alter normal coagulation pathways, although further rigorous evaluation in this area is still required. Fluorescence imaging showed that the organic nanoparticles were taken up by different blood cells and also showed some evidence of adhesion to their surfaces, a property which might find an application in the future. Ultimately, more short-term and long-term safety studies (in-vitro, ex-vitro, and in-vivo) must be conducted before deriving any further conclusions.
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Yang, Mingrui. "Energy Transport in Colloidal Inorganic Nanocrystals." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1616824530811137.
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Waggett, Jonathan. "The study of inorganic semiconductor quantum dots for solar cell applications." Thesis, University of Bristol, 2005. http://hdl.handle.net/1983/916bf29c-07eb-4601-be30-534e81635c1b.
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Garner, Brett William. "Multifunctional Organic-Inorganic Hybrid Nanophotonic Devices." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc6108/.
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The emergence of optical applications, such as lasers, fiber optics, and semiconductor based sources and detectors, has created a drive for smaller and more specialized devices. Nanophotonics is an emerging field of study that encompasses the disciplines of physics, engineering, chemistry, biology, applied sciences and biomedical technology. In particular, nanophotonics explores optical processes on a nanoscale. This dissertation presents nanophotonic applications that incorporate various forms of the organic polymer N-isopropylacrylamide (NIPA) with inorganic semiconductors. This includes the material characterization of NIPA, with such techniques as ellipsometry and dynamic light scattering. Two devices were constructed incorporating the NIPA hydrogel with semiconductors. The first device comprises a PNIPAM-CdTe hybrid material. The PNIPAM is a means for the control of distances between CdTe quantum dots encapsulated within the hydrogel. Controlling the distance between the quantum dots allows for the control of resonant energy transfer between neighboring quantum dots. Whereby, providing a means for controlling the temperature dependent red-shifts in photoluminescent peaks and FWHM. Further, enhancement of photoluminescent due to increased scattering in the medium is shown as a function of temperature. The second device incorporates NIPA into a 2D photonic crystal patterned on GaAs. The refractive index change of the NIPA hydrogel as it undergoes its phase change creates a controllable mechanism for adjusting the transmittance of light frequencies through a linear defect in a photonic crystal. The NIPA infiltrated photonic crystal shows greater shifts in the bandwidth per ºC than any liquid crystal methods. This dissertation demonstrates the versatile uses of hydrogel, as a means of control in nanophotonic devices, and will likely lead to development of other hybrid applications. The development of smaller light based applications will facilitate the need to augment the devices with control mechanism and will play an increasing important role in the future.
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Royo, Romero Luis. "Optoelectronic Characteristics of Inorganic Nanocrystals and Their Solids." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1555422820907262.
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Khozaee, Zahra. "Studies on organic/inorganic nanocomposites of lead sulphide quantum dots in solution- processed phthalocyanine films." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8500.
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A unique organic/inorganic nanocomposite of lead sulphide (PbS) quantum dots (QDs) embedded in substituted metal-free phthalocyanine (C6H2Pc) has been prepared by a simple and low-cost method. The preparation procedure consists of exposure of a thin spun film of non-peripherally octa-hexyl lead phthalocyanine to hydrogen sulphide atmosphere. The formation of the PbS QDs has been verified using X-ray diffraction and transmission electron microscopy techniques. From the transmission electron microscopic measurements, the average size of the PbS QDs is found to be 4.5 nm, which is smaller than the exciton Bohr radius. Independent Xray diffraction and optical absorption studies provide supportive evidence for the size of QDs. Quantum confinement gives rise to a clear blue shift in the absorption spectrum with respect to the bulk PbS. The QDs band gap has been estimated to be 1.95 eV from Tauc's law and the frontier energy levels of the PbS QDs has been derived. About two orders of magnitude increase in ohmic conductivity, from 6.0×10−12 for C6H2Pc to 3.1×10−10 for the nanocomposite, is observed by steady-state electrical measurements in sandwich structure between indium tin oxide and aluminium. Temperature-dependence of the electrical conduction is studied aimed to calculate the activation energy and determine the type of conductivity. The incorporation of the PbS QDs decreases the activation energy by about 0.5 eV at temperatures higher than 240 K. It is found that the Poole-Frenkel mechanism is in good consistency with the superlinear electrical behaviour of the nanocomposite. The frequency response of alternating current (AC) conduction is found to obey the universal power-law. The cryogenic study of AC conduction reveals that the correlated barrier hopping (CBH) model closely fits to the experimental data at temperatures below 240 K. The parameters obtained by fitting the CBH model point out that the hopping process cannot take place directly between neighbouring PbS QDs but involves the localised states within the matrix.
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Dabbousi, Bashir O. (Bashir Osama). "Fabrication and characterization of hybrid organic/inorganic electroluminescent devices based on cadmium selenide nanocrystallites (quantum dots)." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10434.
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Lystrom, Levi Aaron. "Influence of Organic and Inorganic Passivation on the Photophysics of Cadmium Chalcogenide and Lead Chalcogenide Quantum Dots." Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/31926.
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Quantum dots (QDs) are promising materials for photovoltaic (PV) and light-emitting diode (LED) applications due to their unique properties: photostability, size-tunable absorptivity, and narrow line-width emission. These properties are tailored by surface passivations by ligands. However, ligands used in the synthesis of colloidal QDs need to be exchanged with ligands designed for specific applications. The mechanism behind ligand exchange is not well understood. Density functional theory (DFT) is utilized to gain fundamental understanding of ligand exchange (LE) and the resulting effect on the photophysics of QDs. Experimental studies show that phenyldithiocarbamates (PTCs) derivatives can improve the photocurrent of QD-based PVs. Our calculations show that the PTC undergoes decomposition on the CdSe QD surface. Decomposed products of PTCs strongly interact with the surface of QDs, which could cause unforeseen challenges during the implementation of these functionalized QDs in PVs. Secondly, we studied the mechanism of photoluminescence (PL) enhancement by hydride treatment. In experiments, the PL increases by 55 times, but the mechanism is unclear. We found that hydride can interact with surface Se2- producing H2Se gas and passivate surface Cd2+. These interactions result in optically active QDs. Thiol derivatives can also improve PL when LE results in low surface coverage of thiols. The PL is quenched if LE is performed at high concentrations and acidic environments. DFT simulations reveal three scenarios for the thiol interacts with QDs: coordination of thiol, networking between surface and/or other ligands, or thiolate formation. It is the last scenario that was found to be responsible for PL quenching. Lastly, PbS(e)/CdS(e) core/shell QDs are investigated to obtain relaxation rates of electron and hole cooling via interactions with phonons. The band structure of the core/shell QDs facilitates carrier multiplication (CM), a process that generates multiple charge carrier pairs per one absorbed photon. It is thought that CM is facilitated because there are interface associated states that reduce carrier cooling. Non-Adiabatic Molecular Dynamics (NAMD) simulations show that this hypothesis is correct and PbSe/CdSe carrier cooling is about two times slower compared to PbS/CdS due to weaker coupling to optical phonons.
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Esteves, Richard J. "The Dawn of New Quantum Dots: Synthesis and Characterization of Ge1-xSnx Nanocrystals for Tunable Bandgaps." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4637.
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Ge1-xSnx alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge1-xSnx thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in lattice constants. Moreover, little is known about the chemical factors that govern the growth of Ge1-xSnx nanoalloys and the effects of quantum confinement on structure and optical properties. A synthesis has been developed to produce phase pure Ge1-xSnx nanoalloys which provides control over both size and composition. Three sets of Ge1-xSnx nanocrystals have been studied, 15–23 nm, 3.4–4.6 nm and 1.5–2.5 nm with Sn compositions from x = 0.000–0.279. Synthetic parameters were explored to control the nucleation and growth as well as the factors that have led to the elimination of undesired metallic impurities. The structural analysis of all nanocrystals suggests the diamond cubic structure typically reported for Ge1-xSnx thin films and nanocrystalline alloys. As-synthesized Ge1-xSnx nanoalloys exhibit high thermal stability and moderate resistance against sintering up to 400–500 °C and are devoid of crystalline and amorphous elemental Sn impurities.
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Haverinen, H. (Hanna). "Inkjet-printed quantum dot hybrid light-emitting devices—towards display applications." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514261275.
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Abstract
This thesis presents a novel method for fabricating quantum dot light-emitting devices (QDLEDs) based on colloidal inorganic light-emitting nanoparticles incorporated into an organic semiconductor matrix. CdSe core/ZnS shell nanoparticles were inkjet-printed in air and sandwiched between organic hole and electron transport layers to produce efficient photon-emissive media. The light-emitting devices fabricated here were tested as individual devices and integrated into a display setting, thus endorsing the capability of this method as a manufacturing approach for full-colour high-definition displays.
By choosing inkjet printing as a deposition method for quantum dots, several problems currently inevitable with alternative methods are addressed. First, inkjet printing promises simple patterning due to its drop-on-demand concept, thus overruling a need for complicated and laborious patterning methods. Secondly, manufacturing costs can be reduced significantly by introducing this prudent fabrication step for very expensive nanoparticles.
Since there are no prior demonstrations of inkjet printing of electroluminescent quantum dot devices in the literature, this work dives into the basics of inkjet printing of low-viscosity, relatively highly volatile quantum dot inks: piezo driver requirements, jetting parameters, fluid dynamics in the cartridge and on the surface, nanoparticle assembly in a wet droplet and packing of dots on the surface are main concerns in the experimental part. Device performance is likewise discussed and plays an important role in this thesis. Several compositional QDLED structures are described. In addition, different pixel geometries are discussed. The last part of this dissertation deals with the principles of QDLED displays and their basic components: RGB pixels and organic thin-film transistor (OTFT) drivers. Work related to transistors is intertwined with QDLED work; ideas for surface treatments that enhance nanoparticle packing are carried over from self-assembled monolayer (SAM) studies in the OTFT field. Moreover, all the work done in this thesis project was consolidated by one method, atomic force microscopy (AFM), which is discussed throughout the entire thesis.
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Prevost, Richard M. III. "Design and Fabrication of Nanostructures for the Enhancement of Photovoltaic Devices." ScholarWorks@UNO, 2017. http://scholarworks.uno.edu/td/2353.
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In 2012 the net world electricity generation was 21.56 trillion kilowatt hours. Photovoltaics only accounted for only 0.1 trillion kilowatt hours, less than 1 % of the total power. Recently there has been a push to convert more energy production to renewable sources. In recent years a great deal of interest has been shown for dye sensitized solar cells. These devices use inexpensive materials and have reported efficiencies approaching 12% in the lab. Here methods have been studied to improve upon these, and other, devices. Different approaches for the addition of gold nanoparticles to TiO2 films were studied. These additions acted as plasmonic and light scattering enhancements to reported dye sensitized devices. These nanoparticle enhancements generated a 10% efficiency in device performance for dye sensitized devices. Quantum dot (QD) sensitized solar cells were prepared by successive ionic layer adsorption and reaction (SILAR) synthesis of QDs in mesoporous films as well as the chemical attachment of colloidal quantum dots using 3-mercaptopropionic acid (3-MPA). Methods of synthesizing a copper sulfide (Cu2S) counter electrode were investigated to improve the device performance. By using a mesoporous film of indium tin oxide nanoparticles as a substrate for SILAR growth of Cu2S catalyst, an increase in device performance was seen over that of devices using platinum. These devices did suffer from construction drawbacks. This lead to the development of 3D nanostructures for use in Schottky photovoltaics. These high surface area devices were designed to overcome the recombination problems of thin film Schottky devices. The need to deposit a transparent top electrode limited the success of these devices, but did lead to the development of highly ordered metal nanotube arrays. To further explore these nanostructures depleted heterojunction devices were produced. Along with these devices a new approach to depositing lead sulfide quantum dots was developed. This electrophoretic deposition technique uses an applied electric field to deposit nanoparticles onto a substrate. This creates the possibility for a low waste method for depositing nanocrystals onto nanostructured substrates.
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Burriss, Daniel. "INTERACTIONS OF COMPOUNDS CONTAINING GROUP 12 AND 16 ELEMENTS." UKnowledge, 2017. https://uknowledge.uky.edu/chemistry_etds/89.
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The focus of this dissertation is on the interactions of compounds containing group 12 and 16 elements. This work is presented in three major parts. First, the interaction of the synthetic dithiol N,N’-bis(2-mercaptoethyl)isophthalamide), abbreviated BDTH2, with selenite. Second, the interaction of cysteine with Cd(II) and the biologically relevant Cd-Cysteine crystal structure. Third, the green synthesis of CdSe quantum dots (QDs).
The interaction of BDTH2 with selenite is different from the interactions with other metals and metalloids previously studied. Under ambient conditions, BDTH2 is oxidized to the disulfide, BDT(S-S), while selenite is reduced to elemental selenium. However, under carefully controlled conditions, the reaction of BDTH2 with selenite produces a mixture of BDT(S-S) and the covalently bound Se(II) species, BDT(S-Se-S). While the mixture could not be separated, experimental 77Se NMR combined with computational analysis confirmed the presence of BDT(S-Se-S).
The interaction of the amino acid cysteine with Cd(II) was studied as a means to sequester, and potentially recycle, Cd(II) from bulk CdS waste. Single crystals of Cd(Cys)Cl·H2O were grown, and the crystal structure determined. Surprisingly, this is only the second structure to be determined by X-ray crystallography of a compound containing the Cd-Cysteine unit. Not only does this structure have biological relevance, but it also corrects a structure proposed in 1965.
Using the knowledge gained from studying the interaction of BDTH2 with selenite, a green synthesis of water-soluble CdSe QDs by the reaction of selenite with Cd(Cys)Cl·H2O in water at room temperature was developed. This green method for the synthesis of CdSe QDs was extended to ZnSe and HgSe QDs. The mechanism of CdSe formation was investigated using Cd(II) combined with various thiols.
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Albero, Sancho Josep. "Photo-induced charge transfer reactions in quantum dot based solar cells." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/81717.
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En esta tesis doctoral se han estudiado procesos fundamentales de reacciones de transferencia de carga en películas mesoporosas de dióxido de titanio sensitivizado con puntos cuánticos, en películas finas de mezclas polímero:puntos cuánticos y en dispositivos completos de mezclas del polímero PCPDTBT y puntos cuánticos de CdSe en operaciones de trabajo reales.
Los resultados obtenidos permiten abordar la fabricación de dispositivos fotovoltaicos con un conocimiento de los procesos de recombinación que limitan la eficiencia de las celdas más amplio. Y por tanto, se demuestra la posibilidad de fabricar celdas solares basadas en puntos cuánticos con eficiencias iguales o superiores a los dispositivos fotovoltaicos orgánicos.The fundamental processes of the charge transfer reactions between titania dioxide mesoporous films and quantum dots, in blend films of the semiconductor polymer P3HT and CdSe quantum dots and in complete devices fabricated with the polymer PDPCTBT and CdSe quantum dots in working conditions have been studied in this doctoral thesis. The obtained results allow the fabrication of photovoltaic devices with a deeper and wider knowledge of the recombination processes that limit the device efficiency. Therefore, it is demonstrated the possibility of fabrication of quantum dot based solar cells with efficiencies similar or higher than the organic photovoltaic devices.
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Jacobsson, T. Jesper. "Synthesis and characterisation of ZnO nanoparticles.An experimental investigation of some of their size dependent quantum effects." Thesis, Uppsala University, Department of Materials Chemistry, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121715.
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ZnO nanoparticles in the size range 2.5–7 nm have been synthesised by a wet chemical method where ZnO particles were grown in basic zinc acetate solution. The optical band gap increases when the size of the particles decreases. An empirical relation between the optical band gap given from absorption measurements, and particle size given from XRD measurements has been developed and compared to other similar relations found in the literature.
Time resolved UV-Vis spectroscopy has been used to follow the growth of particles in situ in solution. The data show that the growth mechanism not can be described by a simple Oswald ripening approach and nor by an exclusive agglomeration of smaller clusters into larger particles. The growth mechanism is more likely a combination of the proposed reaction themes. The data also reveal that particle formation do not demand a heating step for formation of the commonly assumed initial cluster Zn4O(CH3COO)6.
Steady state fluorescence has been studied as a function of particle size during growth in solution. These measurements confirm what is found in the literature in that the visible fluorescence is shifted to longer wavelengths and loses in intensity as the particles grow. Some picosecond spectroscopy has also been done where the UV fluorescence has been investigated. From these measurements it is apparent that the lifetime of the fluorescence increases with particle size.
The phonon spectrum of ZnO has been studied with Raman spectroscopy for a number of different particle sizes. From these measurements it is clear that there is a strong quenching of the phonons due to confinement for the small particles, and the only clearly observed vibration is one at 436 cm-1 which intensity strongly increases with particle size.
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Tallapally, Venkatesham. "Colloidal Synthesis and Photophysical Characterization of Group IV Alloy and Group IV-V Semiconductors: Ge1-xSnx and Sn-P Quantum Dots." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5568.
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Nanomaterials, typically less than 100 nm size in any direction have gained noteworthy interest from scientific community owing to their significantly different and often improved physical properties compared to their bulk counterparts. Semiconductor nanoparticles (NPs) are of great interest to study their tunable optical properties, primarily as a function of size and shape. Accordingly, there has been a lot of attention paid to synthesize discrete semiconducting nanoparticles, of where Group III-V and II-VI materials have been studied extensively. In contrast, Group IV and Group IV-V based nanocrystals as earth abundant and less-non-toxic semiconductors have not been studied thoroughly. From the class of Group IV, Ge1-xSnx alloys are prime candidates for the fabrication of Si-compatible applications in the field of electronic and photonic devices, transistors, and charge storage devices. In addition, Ge1-xSnx alloys are potentials candidates for bio-sensing applications as alternative to toxic materials. Tin phosphides, a class of Group IV-V materials with their promising applications in thermoelectric, photocatalytic, and charge storage devices. However, both aforementioned semiconductors have not been studied thoroughly for their full potential in visible (Vis) to near infrared (NIR) optoelectronic applications. In this dissertation research, we have successfully developed unique synthetic strategies to produce Ge1-xSnx alloy quantum dots (QDs) and tin phosphide (Sn3P4, SnP, and Sn4P3) nanoparticles with tunable physical properties and crystal structures for potential applications in IR technologies.
Low-cost, less-non-toxic, and abundantly-produced Ge1-xSnx alloys are an interesting class of narrow energy-gap semiconductors that received noteworthy interest in optical technologies. Admixing of α-Sn into Ge results in an indirect-to-direct bandgap crossover significantly improving light absorption and emission relative to indirect-gap Ge. However, the narrow energy-gaps reported for bulk Ge1-xSnx alloys have become a major impediment for their widespread application in optoelectronics. Herein, we report the first colloidal synthesis of Ge1-xSnx alloy quantum dots (QDs) with narrow size dispersity (3.3±0.5 – 5.9±0.8 nm), wide range of Sn compositions (0–20.6%), and composition-tunable energy-gaps and near infrared (IR) photoluminescence (PL). The structural analysis of alloy QDs indicates linear expansion of cubic Ge lattice with increasing Sn, suggesting the formation of strain-free nanoalloys. The successful incorporation of α-Sn into crystalline Ge has been confirmed by electron microscopy, which suggests the homogeneous solid solution behavior of QDs. The quantum confinement effects have resulted in energy gaps that are significantly blue-shifted from bulk Ge for Ge1-xSnx alloy QDs with composition-tunable absorption onsets (1.72–0.84 eV for x=1.5–20.6%) and PL peaks (1.62–1.31 eV for x=1.5–5.6%). Time-resolved PL (TRPL) spectroscopy revealed microsecond and nanosecond timescale decays at 15 K and 295 K, respectively owing to radiative recombination of dark and bright excitons as well as the interplay of surface traps and core electronic states. Realization of low-to-non-toxic and silicon-compatible Ge1-xSnx QDs with composition-tunable near IR PL allows the unprecedented expansion of direct-gap Group IV semiconductors to a wide range of biomedical and advanced technological studies.
Tin phosphides are a class of materials that received noteworthy interest in photocatalysis, charge storage and thermoelectric devices. Dual stable oxidation states of tin (Sn2+ and Sn4+) enable tin phosphides to exhibit different stoichiometries and crystal phases. However, the synthesis of such nanostructures with control over morphology and crystal structure has proven a challenging task. Herein, we report the first colloidal synthesis of size, shape, and phase controlled, narrowly disperse rhombohedral Sn4P3, hexagonal SnP, and amorphous tin phosphide nanoparticles (NPs) displaying tunable morphologies and size dependent physical properties. The control over NP morphology and crystal phase was achieved by tuning the nucleation/growth temperature, molar ratio of Sn/P, and incorporation of additional coordinating solvents (alkylphosphines). The absorption spectra of smaller NPs exhibit size-dependent blue shifts in energy gaps (0.88–1.38 eV) compared to the theoretical value of bulk Sn3P4 (0.83 eV), consistent with quantum confinement effects. The amorphous NPs adopt rhombohedral Sn4P3 and hexagonal SnP crystal structures at 180 and 250 °C, respectively. Structural and surface analysis indicates consistent bond energies for phosphorus across different crystal phases, whereas the rhombohedral Sn4P3 NPs demonstrate Sn oxidation states distinctive from those of the hexagonal and amorphous NPs owing to complex chemical structure. All phases exhibit N(1s) and ʋ(N-H) energies suggestive of alkylamine surface functionalization and are devoid of tetragonal Sn impurities.
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Liyanage, Geethika Kaushalya. "Infrared Emitting PbS Nanocrystals through Matrix Encapsulation." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1403953924.
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Wood, Vanessa Claire. "All inorganic colloidal quantum dot LEDs." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40882.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 85-89).
This thesis presents the first colloidal quantum dot light emitting devices (QD-LEDs) with metal oxide charge transport layers. Colloidally synthesized quantum dots (QDs) have shown promise as the active material in optoelectronic devices because of their tunable, narrow band emission. To date, the most efficient QD-LEDs involve a monolayer of closely packed QDs sandwiched between organic charge transport layers. However, these organic materials are subject to degradation due to atmospheric oxygen and water vapor. In contrast, metal-oxide films used in this work are chemically and morphologically stable in air and can withstand numerous organic solvents, which increases the flexibility of device processing. Furthermore, they can sustain higher carrier injection rates needed to realize an electrically pumped colloidal QD laser. This thesis details the characterization techniques, such as Atomic Force Microscopy, photoluminescence spectroscopy, Hall Effect measurements, X-Ray Diffraction, and Ultraviolet Photoelectron Spectroscopy, used to design efficient QD-LEDs. It reviews the steps used to optimize device performance and obtain a transparent device architecture with external quantum efficiency of 0.15% and a peak luminance of 7000 Cd/m2. This manifests a 100-fold improvement in efficiency over any previously reported all inorganic QD-LED structure.
by Vanessa Claire Wood.
S.M.
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Kniprath, Rolf. "Layer-by-layer self-assembled active electrodes for hybrid photovoltaic cells." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15853.
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Organische Solarzellen bieten die Aussicht auf eine ökologische und zugleich ökonomische Energiequelle. Nachteile des Konzepts liegen in der z.T. geringen Stabilität der für Absorption und Ladungstransport verwendeten Moleküle und einer unvollständigen Ausnutzung des Sonnenspektrums. Zur Verbesserung beider Merkmale werden in dieser Arbeit einzelne organische Bestandteile durch anorganische Materialien mit hoher Stabilität und breiten Absorptionsbanden ersetzt. Insbesondere werden als Absorber kolloidale Quantenpunkte (QP) verwendet, denen aufgrund nicht-linearer und durch Größeneffekte steuerbarer optischer Eigenschaften in der Photovoltaik der dritten Generation großes Interesse gilt. Dazu werden dünne anorganisch-organische Filme mit einem Verfahren hergestellt, das auf Wechselwirkungen zwischen Partikeln in Lösung und geladenen Oberflächen beruht (electrostatic layer-by-layer self-assembly). TiO2-Nanokristalle als Elektronenleiter, kolloidale CdTe- und CdSe-QP als Absorber und konjugierte Polymere als Lochleiter werden in die Filme integriert und diese als aktive Schichten in photovoltaischen Zellen verwendet. Die Struktur der Filme wird zunächst mittels AFM, SEM, XPS sowie durch eine Beladung mit organischen Farbstoffen untersucht. Sie weisen Porosität auf einer Skala von Nanometern sowie eine kontrollierbare Dicke und Mikrostruktur auf. Darauf aufbauend werden durch weitere lösungsbasierte Prozessschritte photovoltaische Zellen gefertigt und Zusammenhänge zwischen Struktur und Zellenleistung elektronisch und spektroskopisch untersucht. Einflussfaktoren der Zelleffizienz wie die Ladungsträgererzeugung und interne Widerstände können so bestimmt und die Effizienz von CdSe-QP als Sensibilisatoren nachgewiesen werden. Die Arbeit demonstriert die Eignung der gewählten Methoden und Zelldesigns zur Herstellung von photovoltaischen Zellen und eröffnet neue Ansätze für die Entwicklung und Fertigung insbesondere auf QP basierender Zellen.Organic solar cells offer the prospect of a both ecological and economical energy source. Drawbacks of the concept are low stabilities of the molecules used for absorption and charge transport and an incomplete utilization of the solar spectrum. In order to improve both these characteristics, individual organic components are replaced by inorganic materials with a high stability and broad absorption bands in this work. In particular, colloidal quantum dots (QDs) are used as absorbers, the non-linear and size controllable optical properties of which are attracting great interest in third generation photovoltaics. For this application, inorganic/organic thin films are produced with a method based on interactions between particles in solution and charged surfaces (electrostatic layer-by-layer self-assembly). TiO2-nanocrystals as electron conductors, colloidal CdTe- and CdSe-QDs as absorbers and conjugated polymers as hole conductors are integrated into the films, which are used as active layers in photovoltaic cells. The structure of the films is investigated by AFM, SEM, XPS and by loading the films with organic dye molecules. The films show porosity on a nanometer scale as well as a controllable thickness and microstructure. Complemented by further solution based processing steps, photovoltaic cells are manufactured and correlations between the structure and performance of the cells are investigated both electronically and spectroscopically. Individual factors that determine the cell efficiency, such as carrier generation and internal resistances, are determined and the efficiency of CdSe-QDs as sensitizers is demonstrated. This work proves the suitability of the chosen methods and cell designs for manufacturing photovoltaic cells and opens up new approaches for the development and manufacture of in particular QD-based solar cells.
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Bhat, Jerome C. "Electroluminescent hybrid organic/inorganic quantum dot devices." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298766.
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La, Rosa Marcello <1989>. "Development of Luminescent Semiconductor Nanocrystals (Quantum Dots) for Photoinduced Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/8059/1/LaRosa_Marcello_Tesi.pdf.
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This thesis focuses on the development of luminescent semiconductor nanocrystals quantum dots (QDs) for photoinduced applications. QDs are promising nanomaterials with size-dependent optical properties and are attractive for applications in several fields.
However, QDs are commonly hydrophobic and many interesting applications require their compatibility with water or at least with a polar environment, meaning a post-synthetic treatment is required to confer a different solubility.
During these studies, a new method for transferring QDs from an apolar solvent to another one polar has been successfully developed, by exploiting lipoic acid, as a versatile surface capping agent. Moreover lipoic acid is a chiral molecule so a possible induced dichroism effect, which has been investigated, as well as its dependence on the size of nanocrystals.
A major aim of this research was the development of QDs exhibiting reversible electronic energy transfer (REET). Such a process is a bidirectional energy transfer between the photoexcited QDs and suitable chromophoric units attached on their surface, where the most important consequence is the elongation of the luminescence lifetime of the QD. Strong experimental evidence for REET and accompanying modifications of the photophysical properties has been obtained. Such a process to our knowledge has never been observed in QD-based systems.
Finally, a novel protocol for depositing charged QDs on a locally polarized glassy substrate has been developed in collaboration with Dr. Marc Dussauze of the University of Bordeaux.
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Morselli, Giacomo <1994>. "Synthesis and electronic properties of luminescent silicon nanocrystals and copper indium sulphide quantum dots." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10175/1/Thesis_Morselli%20G.pdf.
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In the last decades, nanomaterials, and in particular semiconducting nanoparticles (or quantum dots), have gained increasing attention due to their controllable optical properties and potential applications.
Silicon nanoparticles (also called silicon nanocrystals, SiNCs) have been extensively studied in the last years, due to their physical and chemical properties which render them a valid alternative to conventional quantum dots. During my PhD studies I have planned new synthetical routes to obtain SiNCs functionalised with molecules which could ameliorate the properties of the nanoparticle. However, this was certainly challenging, because SiNCs are very susceptible to many reagents and conditions that are often used in organic synthesis. They can be irreversibly quenched in the presence of alkalis, they can be damaged in the presence of oxidants, they can modify their optical properties in the presence of many nitrogen-containing compounds, metal complexes or simple organic molecules. If their surface is not well-passivated, the oxygen can introduce defect states, or they can aggregate and precipitate in several solvents.
Therefore, I was able to functionalise SiNCs with different ligands: chromophores, amines, carboxylic acids, poly(ethylene)glycol, even ameliorating functionalisation strategies that already existed.
This thesis will collect the experimental procedures used to synthesize silicon nanocrystals, the strategies adopted to functionalise effectively the nanoparticle with different types of organic molecules, and the characterisation of their surface, physical properties and luminescence (mostly photogenerated, but also electrochemigenerated).
I also spent a period of 7 months in Leeds (UK), where I managed to learn how to synthesize other cadmium-free quantum dots made of copper, indium and sulphur (CIS QDs). During my last year of PhD, I focused on their functionalisation by ligand exchange techniques, yielding the first example of light-harvesting antenna based on those quantum dots. Part of this thesis is dedicated to them.
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ANUSIT, KAEWPRAJAK. "Improvement of Photovoltaic Properties of Solar Cells with Organic and Inorganic Films Prepared by Meniscuc Coating Technique." Kyoto University, 2019. http://hdl.handle.net/2433/242322.
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Panagiotopoulou, Maria. "Organic-inorganic composite materials for specific recognition and optical detection of environmental, food and biomedical analytes." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2315/document.
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Cette thèse décrit l'état de l'art des sondes et nanoparticules fluorescents traditionnels utilisés en imagerie de fluorescence ainsi que le développement de nouveaux nanomatériaux à base de polymère à empreinte moléculaire, aussi dénommé ‘anticorps plastique’, pour le ciblage et la bioimagerie. En biologie et en médecine, il y a un besoin constant de diagnostiquer diverses maladies pour leur éventuel traitement et prévention. Une distribution anormale et un taux élévé de glycosylation (e.g. acides hyaluronique et sialique) à la surface ou dans les cellules sont indicateurs d’une infection ou d’un cancer. Généralement, l’imagerie par fluorescence permet de visualiser, localiser et quantifier les biomarqueurs de pathologie mais à l’heure actuelle, il n’existe pas d’outil analytique fiable pour cibler spécifiquement les molécules de glycosylation car les anticorps et les lectines vendus dans le commerce ont une faible affinité et sélectivité vis-à-vis de ces cibles. Dans ce contexte, les polymères à empreintes moléculaires (MIPs) pourraient apporter une solution. Les MIPs sont des récepteurs synthétiques possédant des affinités et sélectivités comparables à ceux des anticorps, mais exhibant une stabilité physique, thermique et chimique bien plus accrue. De plus, leur fabrication est peu coûteuse et ne nécessite pas de tuer des animaux comme pour l’obtention des anticorps biologiques. Dans cette thèse, nous avons optimisé et synthétisé des MIPs biocompatibles pour leur utilisation en bioimagerie afin de détecter et quantifier l’acide hyaluronique et l’acide sialique sur les cellules et les tissus de peau humaine. L’acide glucuronique, une composante de l’acide hyaluronique et l’acide N-acétylneuraminique, l’acide sialique le plus commun, ont été utilisés comme molécules ‘patron’, générant des MIPs très sélectifs envers leur cible en milieu aqueux. Deux types de nanoparticules de MIPs fluorescents ont été synthétisés: (1) en incorporant un colorant rhodamine polymérisable dans la solution de pré-polymérisation et (2) en encapsulant des boîtes quantiques InP/ZnS générant ainsi des MIPs de type cœur-coquille. Pour cela, nous avons adopté une stratégie innovante qui consiste à synthétiser les coquilles de MIPs directement autour des boîtes quantiques en utilisant l’énergie de l’onde fluorescente émise par l’excitation des points quantiques, pour initier la polymérisation. Un protocole d'immunocoloration standard a ensuite été optimisé afin d’imager des kératinocytes humains fixés et vivants ainsi que des tissus de peau, par microscopie à épifluorescence et confocale. Les résultats étaient similaires à ceux obtenus par la méthode de référence utilisant une protéine biotinylée reconnaissant l'acide hyaluronique. L'imagerie multiplex en combinant deux MIPs couplés à deux couleurs de boîtes quantiques et l’imagerie des cellules cancéreuses ont également été démontrées. Bien que les MIPs n’étaient pas cytotoxiques aux concentrations utilisées pour la bioimagerie, la toxicité des différentes composantes du MIP pourrait être un frein à leur utilisation dans le domaine biomédical. Afin de rendre ces MIPs plus ‘inoffensifs’, nous avons supprimé l’amorceur de polymérisation, une molécule considérée comme toxique. Les MIPs ont été synthétisés en employant des monomères qui s’auto-initient sous l’effet de l’UV ou de la chaleur. La spécificité et la sélectivité des MIPs obtenus étaient similaires à ceux préparés avec des amorceurs. En conclusion, cette thèse décrit la première utilisation des MIPs comme anticorps synthétique pour la bioimagerie de fluorescence. Ce travail ouvre la voie à de nouvelles applications en détection, diagnostique et thérapie par des MIPsThis thesis describes the state of the art in nanomaterials-based targeted bioimaging and introduces molecularly imprinted polymers, also termed ‘plastic antibodies’ as novel biorecognition agents for labeling and imaging of cells and tissues. In fundamental biology and medical diagnostics, there is a constant need to localize and quantify specific molecular targets. Abnormal glycosylation levels or distributions of hyaluronan or sialic acids on cells are indicators of infection or malignancy. In general, bioimaging with fluorescent probes enables the localization and qualitative or quantitative determination of these pathological biomarkers. However, no reliable tools for the recognition of glycosylation sites on proteins exist, because the commercially available antibodies or lectins have poor affinity and selectivity for these targets. In this context, tailor-made molecularly imprinted polymers (MIPs) are promising synthetic receptor materials since they present a series of advantages over their natural counterparts such as the ease and low cost of preparation and their physical and chemical stability. Thus, MIPs could provide a robust and specific imaging tool for revealing the location/distribution, time of appearance and structure of glycosylation sites on/in cells, which would lead to a better insight of the tremendously diverse biological processes in which these molecules are involved. Herein, we describe the synthesis of water-compatible MIPs for the molecular imaging of hyaluronan and sialylation sites on cells and tissues. Since molecular imprinting of entire biomacromolecules like oligosaccharides is challenging, we opted for what is commonly called the ‘epitope approach’, which was inspired by nature. The monosaccharides, glucuronic acid and N-acetylneuraminic acid were imprinted, and the resulting MIPs were able to bind these molecules when present and accessible on the terminal unit of hyaluronan and sialylation sites. Fluorescent MIPs were synthesized as rhodamine-labeled nanoparticles and as MIP-coated InP/ZnS core-shell quantum dot (QD) particles. For the coating of the QDs, a novel versatile solubilization and functionalization strategy was proposed, which consists of creating polymer shells directly on QDs by photopolymerization using the particles as individual internal light sources. A standard immunostaining protocol was then successfully adapted for the application of the fluorescently labeled MIPs to image fixed and living human keratinocytes and skin tissues, by epifluorescence and confocal fluorescence microscopy. The results were comparable to those obtained with a reference method where staining was done with a biotinylated hyaluronic acid binding protein. Multiplexed and cancer cell imaging were also performed, demonstrating the potential of molecularly imprinted polymers as a versatile biolabeling and bioimaging tool. Although the MIPs were not cytotoxic at the concentrations used for bioimaging, in order to render them generally applicable in biomedicine, where toxicity of the polymerization precursors is a matter of concern, we suppressed the initiator, a toxic chemical. Initiator-free MIPs were thus synthesized by using monomers that can self-initiate under UV irradiation or heat. The specificity and selectivity of the obtained MIPs were as good as the ones prepared with initiators. In conclusion, we have demonstrated for the first time the great potential of MIPs as synthetic antibody mimics for bioimaging. The possibility to associate other functionalities such as QDs and additionally attach drugs to the same material appears rather straightforward due to the synthetic polymeric nature of MIPs, which paves the way to new potential applications in theranostics
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Hagelin, Alexander. "ZnO nanoparticles : synthesis of Ga-doped ZnO, oxygen gas sensing and quantum chemical investigation." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-64730.
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Doped ZnO nanoparticles were synthesized by three different methods – electrochemical deposition under oxidizing conditions (EDOC) , combustion method and wet chemical synthesis – for investigating the oxygen gas sensing response. Ga-doped ZnO was mostly synthesized but also In-doped ZnO was made. The samples were analyzed by XRD, SEM, EDX and TEM. Gas response curves are given alongside with Langmuir fitted curves and data for pure ZnO and Ga-doped ZnO. DFT quantum chemical investigation of cluster models ZnO nanoparticles were performed to evaluate defect effects and oxygen and nitrogen dioxide reactions with the ZnO surface. Defects were investigated by DOS and HOMO-LUMO plots , and are oxygen vacancy, zinc vacancy, zinc interstitial and gallium doping by replacing zinc with gallium. Oxygen and nitrogen dioxide reactions were investigated by computing Mulliken charges, bond lengths, DOS spectra and HOMO-LUMO plots.
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Favaro, Marco. "A rational approach to the optimization of efficient electrocatalysts for the next generation Fuel Cells." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3424667.
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The PhD project has been performed in the Surfaces and Catalysts group active in the Department of Chemical Sciences, within the frame of the grant “A rational approach to the optimization of efficient electrocatalysts for the next generation Fuel Cells”, funded by CARIPARO foundation. The project has been focused on the preparation and characterization of new carbon-based materials for applications in Polymer Electrolyte Membrane Fuel Cells (PEMFCs), also known as oxygen-hydrogen FCs. The preparation of the materials has been performed using different techniques, depending on the type of the target material and on the possible applications that these materials can offer. With reference to the studied model systems (Highly Oriented Pyrolytic Graphite (HOPG) and Glassy Carbon (GC)), the introduction of doping heteroatoms has been performed by ion implantation, while the study of new chemical functionalities has been allowed by the use of Wet Chemistry techniques, in particular derived from the electrochemical synthesis.
The deposition of thin films or nanoparticles (metal or oxides of transition metals) on the ion-modified materials has been carried out in-situ by using advanced techniques under Ultra High Vacuum conditions (UHV), such as Physical Vapor Deposition (PVD). Within the study of the model systems, PVD was chosen because of its ability to provide an atomic scale control of the metal deposition. In a second time, conventional deposition techniques such as chemical or electrochemical reduction of suitable metal precursors have been performed, in a synergistic combination between Surface Science and Electrochemistry-derived techniques.
The characterization of these materials has been performed using the facilities of the Surface Science group, such as the X-ray and Ultraviolet Photoelectron Spectroscopy (XPS - UPS), Scanning Tunneling and Atomic Force Microscopy (STM - AFM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Low Energy Electron Diffraction (LEED). To get a deeper insight in the chemistry/structure/properties of the prepared systems, synchrotron light-based techniques such as HR-XPS, NEXAFS, ARPES, ResPES and PEEM have been extensively used. The study of the electro-catalytic activity has been performed using conventional Electrochemistry techniques, in particular Cyclic and Linear Sweep Voltammetry (CV - LSV), as well as electro-dynamic techniques such as Rotating Disk Electrode (RDE). Finally, in order to support the experimental data or to bring their understanding at a deeper level, simulations using Density Functional Theory (DFT) have been performed in collaboration with the group coordinated by Prof. Cristiana Di Valentin (University of Milano Bicocca). During the course of the doctorate, several collaborations have been pursued with other research groups operating in the Department of Chemical Sciences or abroad, such as the "Interfaces and Energy Conversion E19" research unit, Technical University of Munich (TUM, Germany), coordinated by Profs. O. Schneider and J. Kunze-Liebhäuser.Il progetto di dottorato nasce all’interno del gruppo di ricerca di Superfici e Catalizzatori operante nel dipartimento di Scienze Chimiche, nell’ambito della borsa a titolo vincolato “Un approccio razionale alla ottimizzazione di elettrocatalizzatori efficienti per le celle a combustibile di nuova generazione”, finanziata da fondazione CARIPARO. Le tematica è stata focalizzata sulla preparazione e caratterizzazione di nuovi materiali a base di carbonio utilizzabili per applicazioni in celle a combustibile di tipo PEMFCs (Polymer Electrolyte Membrane Fuel Cells) ad ossigeno-idrogeno. La preparazione dei materiali è avvenuta facendo uso di differenti tecniche, in relazione al tipo di materiale oggetto di studio ed alle applicazioni che tali materiali possono offrire. Con riferimento allo studio dei sistemi modello (grafite pirolitica altamente orientata, HOPG, e carbonio vetroso, GC), il drogaggio degli stessi mediante l’introduzione di eteroatomi (in particolare azoto) è avvenuto ricorrendo alla tecnica dell’impiantazione ionica, mentre lo studio di nuove funzionalità chimiche è stato permesso dall’utilizzo di tecniche di Wet Chemistry, in particolare mutuate dalla sintesi elettrochimica. La deposizione di film sottili o di nanoparticelle (metalliche o a base di ossidi di metalli di transizione) su tali materiali modificati è stata effettuata facendo uso di tecniche avanzate come la deposizione fisica da fase vapore (PVD) in condizioni controllate di Ultra Alto Vuoto (UHV), in grado di offrire un controllo su scala atomica della deposizione di tali film. Sono state utilizzate anche tecniche di deposizione tradizionali quali la riduzione chimica o elettrochimica di opportuni precursori metallici: l‘utilizzazione di una siffatta combinazione sinergica tra tali differenti tecniche di preparazione ha permesso di ottenere materiali caratterizzati da strutture e proprietà peculiari. La caratterizzazione di tali materiali è svolta utilizzando le facilities del gruppo di Scienza delle Superfici, come la spettroscopia di fotoelettroni (XPS) o della banda di valenza (UPS), la microscopia ad effetto tunnel o a forza atomica (STM - AFM), la microscopia elettronica e la dispersione energetica dei raggi X indotta dagli elettroni (SEM-EDX), la diffrazione di elettroni lenti (LEED). Allo scopo di caratterizzare maggiormente in dettaglio la struttura e le proprietà chimiche dei materiali preparati sono state usate estensivamente le tecniche di indagine offerte dalla luce di sincrotrone (HR-XPS, NEXAFS, ARPES, ResPES, PEEM), mentre lo studio della reattività catalitica si basa su tecniche derivate dall’analisi elettrochimica, in particolare la voltammetria ciclica ed a scansione lineare del potenziale applicato, nonchè tecniche elettro-dinamiche come la voltammetria su elettrodo rotante. Infine, allo scopo di supportare i dati sperimentali o portare la comprensione delle proprietà dei materiali ad un livello più profondo, simulazioni mediante teoria del funzionale densità (DFT) sono state adottate per un approccio critico allo studio dei materiali preparati (in collaborazione con il gruppo coordinato dalla prof. Cristiana Di Valentin, Università di Milano Bicocca). Durante il corso del dottorato, diverse collaborazioni sono state perseguite con gruppi interni al Dipartimento di Scienze Chimiche o anche Esteri, come l’unità di ricerca “Interfaces and Energy Conversion E19”, dell’università tecnica di Monaco di Baviera (TUM, Technische Universität München, Germania), coordinata dai proff. O. Schneider e J. Kunze-Liebhäuser.
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CHEN, YI-HUI, and 陳沂暉. "Study on photoluminescence of inorganic perovskite quantum dots." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/e6y67d.
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碩士明志科技大學
電子工程系碩士班
107
Quantum dots (QDs) have attracted intensive studies in recent years, due to their unique optical properties. Compared to II-VI QDs, all-inorganic perovskite CsPbX3 (X = Cl, Br, I) QDs exhibit outstanding optical properties, such as higher stability, narrow band emissions, tunable color properties and high device efficiency. In this thesis, CsPb(Br1-xIx)3 perovskite QD with different compositions (x = 0, 0.33, 0.5, 0.67, and 1) were prepared and the temperature-dependent photoluminescence (PL) were carried out in the temperature range from 10 to 300 K. At 10K, the PL emission peaks locate in the wavelength range from 505 to 675 nm as x increases from 0 to 1. To investigate the thermal behaviors of peak energy, full width at half maximum, and intensity of the PL spectra measured from our samples, the carrier emission mechanism, electron-phonon scattering, electron-phonon interaction and thermal expansion effect on the band-gap are discussed. The analysis can serve as a reference for designing perovskite-based optoelectronic devices.
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Tang, An-Cih, and 湯安慈. "All-Inorganic Perovskite Quantum Dots for Light-Emitting Diodes." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/92c5k8.
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碩士國立臺灣大學
化學研究所
105
White light-emitting diodes (LEDs) is widely used as backlighting components in the modern liquid-crystal display (LCD). For high-quality backlight, color saturation and color gamut are the key indicators, which affect the color performance display devices. Perovskite CsPbBr3 quantum dots (QDs) are regarded as the most promising narrow-band green-emitting material for wide-color-gamut backlight displays because of their high photoluminescence quantum yield (PLQY) and the narrow-band emission with a full width at half maximum (FWHM) of ∼20 nm. Despite their growing popularity, CsPbBr3 QDs have several shortcomings such as the existence of surface trap states, poor thermal and aqueous stability, and the solution QDs are unsuitable for direct use in on-chip white LEDs. Here, a three-step treatment of perovskite CsPbBr3 QDs toward high brightness and stable narrow-band green emission was investigated. After the treatment, a robust and stable narrow-band perovskite mesoporous-CsPbBr3/SDDA@ PMMA powder was obtained. The powder exhibited several advantages, including high absolute PLQY of 63%, improved thermal stability, and water resistance. A white LED used in backlight display was successfully fabricated with color coordinates of (0.271, 0.232) that passed through RGB color filters with an NTSC value of 102%. Moreover, CsPbBr3 perovskite QDs are potential emitters for QLED electroluminescent displays. However, balancing their performance and their environmentally friendly property is challenging. To achieve such balance, we demonstrated an easy hot-injection method to synthesize Cs(Pb1-xSnx)Br3 QDs by partially replacing the toxic Pb2+ with the highly stable Sn4+. Meanwhile, the absolute PLQY of Cs(Pb0.67Sn0.33)Br3 QDs increased from 45% to 83% compared with CsPbBr3. Based on a femtosecond transient absorption, time-resolved PL, and single-dot spectroscopies, we conclude that the PLQY enhancement is due to the reduction of trion formation in perovskite QDs with Sn4+ substitution. This trion-formation suppression by Sn4+ substitution consequently increased the performance of QLED devices based on these highly luminescent Cs(Pb0.67Sn0.33)Br3 QDs, exhibiting a central emission wavelength of 517 nm, a current efficiency of 11.63 cd/A, and an external quantum efficiency of 4.13%, which to date are the highest values among the reported Sn-based perovskite QLED devices.
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Chen, Shih-Hsuan, and 陳世軒. "Synthesis of All Inorganic Lead Halide Perovskit Quantum Dots." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3n4tk8.
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碩士國立臺灣科技大學
化學工程系
106
In this study, all inorganic cesium lead bromide (CsPbBr3) perovskite quantum dots (QDs) were synthesized via room temperature process. The properties of CsPbBr3 QDs were analyzed by structural and optical measurement. From analysis results, we can know that the size distribution of room temperature prepared CsPbBr3 QDs is very uniform and the quantum yield (QY) can achieve 91.8 %. In addition, the composition emission wavelengths of perovskite QDs can adjust by anion exchange process. The emission wavelengths can cover the whole visible region. The stability of red emission QDs made by anion exchange process can be effectively improved by using acetone as precipitant. Besides, the stability of red emission QDs with 650 nm is superior to the red emission QDs with 670 nm. For storage issue, the stability of red emission QDs suspended in octane is better than that in toluene. We also studied the influence of ligand on the surfaces of QDs and observed that the emission quenching of red emission QDs can effectively reduce with low residual oleylamine on the surfaces of QDs. After 50 days, the QY can maintain 60% of the original value. For the massive production, we tried two kinds of methods, batch process and continuous flow process, to synthesize CsPbBr3 QDs. The QY of CsPbBr3 QDs synthesize by batch process would reduce to 66.9% due to non-uniformly stirring. However, the size distribution of CsPbBr3 QDs was uniform when continuous flow process was employed and the QY of CsPbBr3 QDs could achieve 83.9% when the flow rate was set as 1.6 mL/min. To improve the stability of CsPbBr3 QDs furthermore for using in white light converter layer, silicon oxide (SiOx) layer was formed as matrix to cover CsPbBr3 QDs by using tetramethyl orthosilicate (TMOS) under relative humidity of 65% and room temperature. SiOx covered CsPbBr3 QDs could be suspended in water to emission light without serious degradation.
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Magalhães, Débora Vale. "Synthesis of Inorganic Halide Perovskite Quantum Dots for Photoluminescence Applications." Master's thesis, 2018. http://hdl.handle.net/10362/56425.
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Metal halide perovskite crystal structures have emerged as an attractive class of optoelectronic materials due to their excellent optical absorption and emission properties. Restricting the physi-cal dimension of the crystallite to the nanometer scale revealed quantum-confinement effects sim-ilar to those presented by traditional chalcogenide quantum dots. The synthetized inorganic per-ovskite quantum dots (IPQD) were characterized by spectroscopic measurements (absorption and photoluminescence emission spectra). Two synthesis methods were studied (supersaturation re-crystallization (SR) and hot-injection method (HI)) and the latter was chosen to be employed for the remaining work stages, due to observed better properties. The final goal was to obtain IPQDs doped with metals, focusing in Cd2+. The obtained samples of bromide-based perovskite doped with CdI2 exhibit more defined emission peaks with smaller full width at medium height (FWHM) and the samples appear to show improved stability when compared with blank CsPbBr3. The smaller FWHM was also observed for the CsPbI3 doped with CdI2. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was performed for samples with 10 mol% and 30 mol% of CdI2, where it was verified that 2.6 % and 8.23 % of the doping was introduced in the final compound, respectively. Note that the latter value was significantly better than those reported in literature (about 2% of the initial amount). The observed optical properties and empirically im-proved stability make these nanocrystals promising materials in several optoelectronic applica-tions, namely LEDs, solar cells, lasers, among others.
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Jia-HengDai and 戴嘉恆. "All-inorganic perovskite quantum dots doped cholesteric liquid crystal laser." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/rg2d8a.
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碩士國立成功大學
光電科學與工程學系
106
This work demonstrated for the first time an highly efficient all-inorganic perovskite quantum dots doped CLC (AIPQD-CLC) laser. The AIPQD material as an efficient optical gain medium in the optical resonator of the CLC planar texture can be obtained by pre-underdoing a low-cost solvothermal process.. Experimental results show that the AIPQD lattice structure corresponds to the black orthorhombic phase of CsSnI3 perovskite. The ge value and linewidth of the lasing signal from the AIPQD-CLC laser measured are around 1.8 and 0.21 nm, respectively. The aggregation of the AIPQDs in the CLC may significantly decrease the lasing performance. In second part, the position of the bandedge can be changed by changing the composition ratio of the chiral and LC such that the lasing wavelength of the AIPQD-CLC laser can be tuned. Experimental results show that both the absorption and photoluminescence (PL) of the QDs may competitively influence the lasing threshold. Additionally, the energy threshold of the AIPQD-CLC laser can be as low as 1.86 μJ/pulse. Including the lasing threshold, ge value and linewidth, the performances of the AIPQD-CLC laser are nearly comparable with those based on traditional dye-doped CLC lasers. In third part, the thermal, AC and DC electrical tuning features of the AIPQD-CLC laser were demonstarted. The AIPQD-CLC laser exhibited a high potential to become a new class of candidates for photonic applications, particularly in multi-tunable light-emitting devices.
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Tsai, Hsin-Yu, and 蔡欣妤. "All-Inorganic Perovskite Quantum Dots for Organic Light-Emitting Diodes." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/wj8eqf.
Full textAbstract:
碩士國立臺灣大學
化學研究所
106
White light-emitting diodes (LEDs) is widely used as backlighting components in the modern liquid-crystal display (LCD). For high-quality backlight, color saturation and color gamut are the key indicators, which affect the color performance display devices. Perovskite CsPbBr3 quantum dots (QDs) are regarded as the most promising narrow-band green-emitting material for wide-color-gamut backlight displays because of their high photoluminescence quantum yield (PLQY) and the narrow-band emission with a full width at half maximum (FWHM) of ∼20 nm. Despite their growing popularity, CsPbBr3 QDs have several shortcomings such as the existence of surface trap states, poor thermal and aqueous stability, and the solution QDs are unsuitable for direct use in on-chip white LEDs. Here, the surface treatment of perovskite CsPbBr3 QDs with thiocyanate salts (SCN-) toward high brightness and stable narrow-band green emission was investigated. After the treatment, a high quantum yield and stable narrow-band perovskite CsPbX3-SCN was obtained. The product exhibited several advantages, including high absolute PLQY of 94%, enhaced photoluminescence intensity, and air stability. Moreover, CsPbBr3-SCN perovskite QDs are potential emitters for QLED electroluminescent displays. However, balancing their performance and their environmentally friendly property is challenging. To achieve such balance, we demonstrated an easy hot-injection method to synthesize Cs(Pb1-xSnx)Br3 QDs by partially replacing the toxic Pb2+ with the highly stable Sn4+. Meanwhile, the absolute PLQY of Cs(Pb0.67Sn0.33)Br3 QDs increased from 45% to 83% compared with CsPbBr3. Based on a femtosecond transient absorption, time-resolved PL, and single-dot spectroscopies, we conclude that the PLQY enhancement is due to the reduction of trion formation in perovskite QDs with Sn4+ substitution. Moreover, the CsPbBr3-SCN solution that surface treatment with thiocyanate salt increased the performance of QLED devices based on these highly luminescent cesium lead halide perovsike QDs, exhibiting a central emission wavelength of 516 nm, a current efficiency of 4.2 cd/A, and an external quantum efficiency of 1.4% which is the higher values among the CsPbBr3 perovskite QLED devices.
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Paikaray, Sonali. "A Simple Hydrothermal Synthesis of Luminescent Carbon Quantum Dots from Different Molecular Precursors." Thesis, 2013. http://ethesis.nitrkl.ac.in/4627/1/411CY2027.pdf.
Full textAbstract:
In this work,highly photoluminescent C-dots have been synthesised from different precursors such as sucrose, ascorbic acid, citric acid and their combinations under similar conditions to that of recently reported synthesis of C-dots from orange juice.The synthesized carbon nanoparticles have been characterized by XRD, FTIR, UV, and fluorescence measurements. The fluorescence quantum yields of carbon dots synthesized from different precursors have been compared to verify the suitability of C-dots for different applications. We have also thoroughly investigated the effect of excitation wavelength, pH, and electrolyte concentration on luminescent properties.
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Campos, Michael Paul. "The Synthesis and Surface Chemistry of Colloidal Quantum Dots." Thesis, 2017. https://doi.org/10.7916/D86H4VZG.
Full textAbstract:
Colloidal semiconductor nanocrystals, also known as quantum dots, are an extraordinary class of material, combining many of the most attractive properties of semiconductors with the practicality of solution chemistry. As such, they lie at a unique interface between inorganic chemistry, organic chemistry, solid-state physics, and colloidal chemistry. The rapid advance in knowledge of quantum dots over the past 30 years has largely been driven by interest in their fundamental physical properties and their broad applicability to challenges in nanoscience. However, much less attention has been paid to the chemistry underlying these features. In this dissertation, we discuss the state of nanocrystal chemistry and new insights we have unlocked by taking a bottom-up, chemistry-based approach to nanocrystal synthesis. We will cover these in a case-by-case fashion in the context of four chapters.
Chapter 1 covers our CdTe nanocrystal synthesis surface chemistry studies with an eye toward CdTe photovoltaic technology, in which the role of CdTe surfaces is poorly understood. CdTe nanocrystals are traditionally a difficult material to synthesize, particularly with well-defined surface chemistry. In order to enable quantitative surface studies, we looked upstream and re-evaluated CdTe synthesis from the ground up. We identified a CdTe precursor largely overlooked since 1990, cadmium bis(phenyltellurolate) (Cd(TePh)2), and harnessed its excellent reactivity toward a synthesis of CdTe nanocrystals solely bound by cadmium carboxylate (Cd(O2CR)2) ligands. We then use this well-defined material to show that Cd(O2CR)2 ligands bind less tightly to CdTe nanocrystals than CdSe nanocrystals. This finding holds promise for the development of photovoltaics from colloidal CdTe feedstocks.
Chapter 2 covers a tunable library of substituted thiourea precursors to metal sulfide nanocrystals. Controlling the size of nanocrystals produced in a given reaction is paramount to their use in opto-electronic devices, but the most widely used technique to control size is prematurely arresting crystal growth. We introduce a library of thiourea precursors whose organic substituents tune the rate of precursor conversion, which dictates the number of nanocrystals formed and the final nanocrystal size following complete precursor conversion. We use PbS as a model system to 1) demonstrate the concept of kinetically controlled nanocrystal size, 2) quantify substituent trends, and 3) optimize multigram scale syntheses. We then expand the thiourea methodology to a broad range of materials and nanocrystal morphologies. This work represents a paradigm shift that will greatly accelerate the pace of progress in nanocrystal science as it transitions from academia to a multibillion-dollar industry.
Chapter 3 covers an analogously tunable library of substituted selenourea precursors, but focuses on the synthesis of PbSe nanocrystals. PbSe nanocrystal synthesis is notoriously low-yielding and poorly tunable, but the remarkable properties of PbSe nanocrystals in photovoltaics and electrical transport have driven interest in the material for decades. We develop a library of N,N,N’-trisubstituted selenourea precursors and leverage their fine conversion rate tunability to synthesize PbSe nanocrystals of many sizes in quantitative yields. Interestingly, the nanocrystals produced in this reaction are demonstrably less polydisperse than literature samples, exhibiting absorption linewidths approaching the single-particle limit. We quantify this narrowness using a transient absorption spectroscopy technique called spectral hole burning.
Chapter 4 covers our efforts to dig deeper into nanocrystal nucleation and growth and use that new knowledge to develop luminescent downconverters ready for on-chip integration into LED lighting. By studying early time points in PbS and PbSe nanocrystal synthesis, we estimate solute concentrations, nucleation thresholds, and nanocrystal growth rates. In particular, we find that metal selenides and sulfides have very different nucleation and growth behavior, as well as that PbS nucleation is a surprisingly slow process. The lessons learned from these fundamental experiments have enabled us to rapidly develop red-emitting CdS/CdSe/CdS “spherical quantum well” emitters whose photoluminescence quantum yields are 90 – 95%.
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Resetco, Cristina. "Homo and Hetero-assembly of Inorganic Nanoparticles." Thesis, 2012. http://hdl.handle.net/1807/32619.
Full textAbstract:
This thesis describes the synthesis and assembly of metal and semiconductor nanoparticles (NPs). The two research topics include i) hetero-assembly of metal and semiconductor NPs, ii) effect of ionic strength on homo-assembly of gold nanorods (GNRs). First, we present hetero-assembly of GNRs and semiconductor quantum dots (QDs) in a chain using biotin-streptavidin interaction. We synthesized alloyed CdTeSe QDs and modified them with mercaptoundecanoic acid to render them water-soluble and to attach streptavidin. We synthesized GNRs by a seed-mediated method and selectively modified the ends with biotin. Hetero-assembly of QDs and GNRs depended on the size, ligands, and ratio of QDs and GNRs. Second, we controlled the rate of homo-assembly of GNRs by varying the ionic strength of the DMF/water solution. The solubility of polystyrene on the ends of GNRs depended on the ionic strength of the solution, which correlated with the rate of assembly of GNRs into chains.
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Yu, Chung-Ping, and 俞中平. "Study on Optical Property and Reliability of Inorganic Perovskite Quantum Dots LED." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/k9bpfz.
Full textAbstract:
碩士國立交通大學
光電系統研究所
107
In this thesis, all inorganic halide perovskite quantum dots and light-emitter diodes are used to verify excitation wavelength, encapsulate difference, concentration ratio and the addition of high scattering material Zirconium dioxide in order to optimize the inorganic perovskite quantum dots hybrid light-emitter diode. The quantum dots were coated in silicon dioxide by hydrolysis method to separate the contact between external moisture and oxygen to cause self-aggregation or degradation of quantum dots. We use perovskite quantum dots coated in silica encapsulated on light-emitter diode with polydimethylsiloxane(PDMS). Pumping the quantum dots with higher energy photon from LED chips. Continuously long-term lighting the PQD analysis the change of spectrum and the reliability of the devices is tested by multiple conditions.
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Gopal, Ashwini. "Multicolor colloidal quantum dot based inorganic light emitting diode on silicon : design, fabrication and biomedical applications." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2209.
Full textAbstract:
Controlled patterning of light emitting diodes on semiconductors enables a vast variety of applications such as structured illumination, large-area flexible displays, integrated optoelectronic systems and micro-total analysis systems for real time biomedical screening. We have demonstrated a series of techniques of creating quantum-based (QD) patterned inorganic light emitting devices at room temperature on silicon (Si) substrate. In particular:
(I) A combination of QDs self-assembly and microcontact printing techniques were developed to form the light emission monolayer. We expand the self-assembly method with the traditional Langmuir-Schaeffer technique to rapidly deposit monolayers of core: shell quantum dots on flat substrates. A uniform film of QDs self-assembled on water was transferred using hydrophobic polydimethylsiloxane stamps with various nano/micro-scale patterns, and was subsequently stamped. A metal oxide electron transport layer was co-sputtered onto the QDs. The structure was completed by an e-beam evaporating thin metal cathode. Multicolor light emission was observed on application of voltage across the device.
(II) We also demonstrate the photolithographic patterning capability of a metal cathode for top emitting QDLEDs on Si substrates. Lithographic patterning technique enables site-controlled patterning and controlled feature size of the electrode with greater accuracy. The stability of inorganic silicon materials and metal oxide based diode structure offers excellent advantages to the device, with no significant damage observed during the patterning and etching steps. Efficient electrical excitation of QDs was demonstrated by both the methods described above.
The technique was translated to create localized QD-based light sources for two applications: (1) Three-dimensional scanning probe tip structures for near field imaging. Combined topographic and optical images were acquired using this new class of “self-illuminating” probe in commercial NSOM. The emission wavelength can be tuned through quantum-size effect of QDs. (2) Multispectral excitation sources integrated with microfluidic channels for tumor cell analyses. We were able to detect the variation of sub-cellular features, such as the nucleus-to-cytoplasm ratio, to quantify the absorption at different wavelength upon the near-field illumination of individual tumor cells towards the determination of cancer developmental stage.text
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Lin, Shin-Ying, and 林欣穎. "Synthesis, Characterization and Applications of All-Inorganic Perovskite Light-emitting Semiconducting Quantum Dots." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/49993841785862631578.
Full textAbstract:
碩士國立臺灣大學
化學研究所
104
The thrust of my master thesis is on the synthesis of zero-dimension all-inorganic perovskite quantum dots(CsPbX3, X = Cl, Br, I) nanomaterials by colloidal solution methodas luminescent materials for light emitting diode(LED)backlight display applications. In this study, we tuned halogen composition ratio and investigated particle size and band gap difference to explain the spectral shift. We expect to find a correlation of the spectral shift and therefore establish a general explain. We also controlled the Br/I ratio of CsPb(Br1-xIx)3 and analyzed their different optical properties. First, the 01C2 experiment station at the Synchrotron Radiation Research Center and Bruker D2 Phaser were used to measure X-ray powder diffraction patterns. We employed field emission electron microscopy to analyze the morphology of cubic quantum dots, and by turning the halogen composition corresponding with lattice spacing maintains regularity. We used Tauc plot to calculate the difference of band gap energy as shown by the spectral shift which we found to be caused by the different ratios of Br and I and not because of their particle size difference. Furthermore, we focused on this all-inorganic perovskite-type quantum dot which was applied for the first time for white light emitting diodes. With varying proportions of blue, green and red QD’s, a narrow, white light-emitting material was produced. Further, mesoporous silica particle loaded with perovskite-type quantum dots was also investigated to resolve problems ofion-exchange during LED packaging and thus, effectively enhance the material''s thermal and light stability. These novel nanocomposite perovskite-type quantum dots were successfully applied for LED devices.
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Fu, Huai-Kuang, and 傅懷廣. "The Study of Organic-Inorganic Clay and Quantum Dots Nanocomposites on Physical Properties." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/32220963794264167942.
Full textAbstract:
博士國立交通大學
應用化學系所
97
Polymer nanocomposites are commonly defined as the combination of a polymer matrix and additives that have at least one dimension in nanometer range. The additives can be one-dimensional (example include nanotubes and fibers), two- dimensional (which include layered minerals like clay), or three-dimensional (include spherical particles and quantum dots). Nanoscale-filled polymeric systems offer the prospect of greatly improving many of the properties of the polymer matrix. The dissertation was focused on four major subjects: the study of the inorganic additives of polymer nanocomposites on physical properties. 1.Studies on Thermal Properties of PS Nanocomposites for the Effect of Intercalated Agent with Side Groups Polystyrene layered silicate nanocomposites were prepared from three new organically modified clays by emulsion polymerization method. These nanocomposites were exfoliated up to 3 wt % content of pristine clay relative to the amount of polystyrene (PS). The intercalated agents, C20, C20-4VB, and C20-POSS intercalated into the galleries result in improved compatibility between hydrophobic polymer and hydrophilic clay and facilitate the well dispersion of exfolicated clay in the polymer matrix. Results from X-ray diffraction, TEM and Fourier transform infrared spectroscopy indicate that these intercalated agents are indeed intercalated into the clay galleries successfully and these clay platelets are exfoliated in resultant nanocomposites. Thermal analyses of polystyrene-layered silicate nanocomposites compared with virgin PS indicate that the onset degradation temperature ca. 25 °C increased and the maximum reduction in coefficient of thermal expansion (CTE) is ca. 40 % for the C20-POSS/clay nanocomposite. In addition, the glass transition temperatures of all these nanocomposites are higher than the virgin PS. 2.Properties Enhancement of PS Nanocomposites through the POSS surfactants The polyhedral oligomeric silisesquioxnae (POSS)-clay hybrids of polystyrene are prepared by two organically modified clays using POSS-NH2 and C20-POSS as intercalated agents. X-ray diffraction (XRD) studies show that the formation of these POSS/clay/PS nanocomposites in all cases with the disappearance of the peaks corresponding to the basal spacing of MMT. Transmission electronic spectroscopy (TEM) was used to investigate the morphology of these nanocomposites and indicates that these nanocomposites are comprised of a random dispersion of exfoliated throughout the PS matrix. Incorporation of these exfoliated clay platelets into the PS matrix led to effectively increase in glass transition temperature (Tg), thermal decomposition temperature (Td) and the maximum reduction in coefficient of thermal expansion (CTE) is ca. 40 % for the C20-POSS/clay nanocomposite. 3.Effect of the organically modified Nanoclay on Low-Surface-Energy Materials of Polybenzoxazine Novel low surface free energy materials of polybenzoxazine/organically modified silicate nanocomposites have been prepared and characterized. The CPC (cetylpyridinium chloride)/clay10%/Poly(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) (PP-a) possesses an extremently low surface free energy (12.7 mJ/m2) after 4 hrs curing at 200 ℃, even lower than that of poly(tetrafluoroethylene) (22.0 mJ/m2) calculated on the basis of the three-liguid geometric method. X-ray photoelectron spectroscopy (XPS) shows higher silicon content on the surface of nanocomposites than average composition, implying that the clay is more preferentially enriched on the outermost layer. In addition, the glass transition temperature (Tg) of the polybenzoxazine (PP-a) in the nanocomposite is 22.6 ℃ higher and its thermal decomposition temperature is also higher than the pure PP-a. This finding provides a simple way to prepare lower surface energy and high thermal stability material. 4.Preparation of the Stimuli-Responsive ZnS/PNIPAM Hollow Spheres Novel quantum dots ZnS/poly(N-isopropylacrylamide) (PNIPAM) hybrid hollow spheres were obtained by localizing free radical polymerization of NIPAM and crosslinker (MBA) at the peripheral of PCL nanoparticles, followed by biodegradation of PCL with an enzyme of the Lipase PS. The formation of ZnS/PNIPAM hollow spherical structures and the thermo-sensitive reversible properties were systematically investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The ZnS/PNIPAM hollow spheres possess the photoluminescence properties and a swelling and de-swelling at about 32 oC, which agrees well with the slight red-shift in photoluminescence spectra.
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Hui-CiYan and 顏慧慈. "Investigation of Color Conversion microcavity Organic Light-Emitting Diodes with Inorganic Quantum Dots." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/13609230519604159751.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
100
In this study, the color conversion organic light-emitting diodes (OLEDs) were fabricated by using the blue-green OLEDs and red emitting CdSe/ZnS core/shell quantum dots (QDs). The basic structure of the OLEDs was composed by indium tin oxide (ITO)/ N,N′-Di-[(1-naphthyl)-N,N′-diphenyl]-1,1′ biphenyl)-4,4′-diamine (NPB)/ 2-methyl-9,10- di(2-napthyl)anthracene:p-bis(p-N,N-diphenyl-aminostyryl)benzene (MADN:DSA-Ph)/ tris-(8-hydroxyquinoline)aluminum (Alq3)/ lithium fluoride (LiF)/ aluminum (Al). All of the devices were deposited on glass substrates. NPB, MADN:DSA-Ph, Alq3, LiF, and Al were used as the hole transporting layer, emitting layer, electron transporting layer, electron injection layer and cathode, respectively. To improve the light emitting efficiency of our blue-green emitting devices, the microcavity OLEDs consist of the semi-transparent silver (Ag) thin film as the bottom mirror and Al film as the top mirror was fabricated. Besides, the molybdenum trioxide (MoO3) thin film could be well-deposited on the Ag film by thermal evaporation, result in the enhancement of light emitting efficiency and decreaseing the turn on voltage for microcavity OLEDs. Finally, the QD-PMMA composite film was wiped on the backside of the glass substrates to be used as the color conversion layer. The red emitting QDs were successfully excited by blue-green light emitting devices and the pure white organic light-emitting diodes (WOLEDs) were achieved by introducing the intensity adjustment of the three-band spectra. Both WOLEDs showed high color stability, despite the increase of the operation current. WOLEDs with microcavity structures also exhibited higher light efficiency. Nevertheless, the pure white light wasn’t easily obtained. The luminous efficiency and luminance was 1.93 cd/A and 9904 cd/m2 at 6 mA, respectively, which was enhanced by 42.9 % and 64 % in comparison with that of 1.35 cd/A and 6047cd/m2 for WOLEDs based on basic structures, respectively. The CIE coordinates were (0.306, 0.323), and the correlated color temperature (CCT) was 6910.
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Lin, Hung-Ju, and 林宏儒. "Study and applications of hybrid organic/ inorganic semiconductor quantum dots in thin films." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/67947611770527042033.
Full textAbstract:
博士國立中央大學
光電科學與工程學系
102
Semiconductor quantum dots have attracted a lot of attention for their potential application in many fields such as optoelectronics and biology. In this study, we investigated the optical properties of hybrid nanocomposited thin films made of PMMA polymer containing different concentrations of core-shell CdSe/ZnS quantum dots. Both the absorption and luminescence spectra can be well explained by taking into account quantum mechanisms. From the luminescence spectral evidence of the coupling effect between quantum dots has been observed. With a pump laser emitting at 514 nm the luminescence spectrum centered at 560 nm strongly changes with time. In addition, it is necessary to control the luminescent light spatial distribution where the application is concerned. Therefore we proposed structural films with a bi-periodic grating by nanoimprint technique using an engraved silicon mold. The characterizations of the imprinted structure show good quality. We also showed, by a numerical calculation, that the local field is resonant in the periodic structure and that the emission diagram can be controlled in the far field.
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Tsai, Tsan-Hung, and 蔡璨鴻. "Synthesis of All Inorganic Lead Halide Perovskite Quantum Dots by Micro-fluidic channel." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/tg6wqd.
Full textAbstract:
碩士國立臺灣科技大學
化學工程系
107
Recently, all inorganic cesium lead halide (CsPbX3, X=Cl, Br, I) quantum dots (QDs) could achieve high photoluminescence quantum yield (PL QY), which were synthesized by batch type process in room temperature. However, PL QY of inorganic cesium lead halide quantum dots synthesized by massive batch type process is low. Therefore, micro fluidic channel chip design was employed for massive production of high PL QY CsPbBr3 QDs. According to analysis results, we could know that PL QY of CsPbBr3 QDs synthesized via micro fluidic channel chip is higher than that via massive batch type process. In addition, red emission CsPb(Br/I)3 QDs with high PL QY could also be prepared by micro fluidic channel chips with anion exchange process. In this study, PL QY of CsPbBr3 QDs and CsPb(Br/I)3 QDs synthesized by micro fluidic channel chips could achieve 85% and 64%, respectively. However, the production rate for CsPbX3 QDs synthesized by micro fluidic channel chip is low. Therefore, water post treatment was employed to improve the production rate for CsPbX3 QDs. In addition, the improvement of CsPbX3 QDs stability was also studied. Inorganic silica (SiO2) shells were employed to enclose on the outer surfaces of CsPbX3 QDs as barrier layer for avoiding the influence of humidity and oxygen. In the next, CsPbBr3/SiO2 and [CsPb(Br/I)3]/SiO2 powders were blended together to mix with poly (methyl methacrylate) (PMMA) as light convert layer. Combing the light convert layer with blue indium gallium nitride (InGaN) light emitting diode (LED) chip with 460 nm, a white light could be obtained. The characteristics of white light emission were luminous efficiency=39 lmW 1, luminance=2973 cdm 2, color temperature=4800 K under 2.5 V. The reproducibility of white light emitting is good and the color gamut could achieve 119% NTSC standard.
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Cho, Yu-Yun, and 卓佑芸. "Innovative Structure on Inorganic Perovskite Quantum Dots LED with High Thermal Conductivity Materials." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/6tgt9j.
Full textAbstract:
碩士國立交通大學
光電系統研究所
108
In this article, to realize the thermal impact on the quantum dots, we use inorganic halide perovskite quantum dots coated in silicon dioxide mixed with polydimethylsiloxane (PDMS). The goals of silica and PDMS are isolated from the environment. In addition, the mixture will be added with high thermal conductivity material Boron nitride which has hexagonal crystal structure. Adding high thermal conductivity materials is aimed to reduce the thermal effect. Then, we utilize two structures with the above sample on the standard 5070 package which has the ultra-violet light emitting diode chip at the bottom. The heat transfer is complicated, so we employ two structures in the experiments to understand which is better for package to reduce thermal impact. In the end, we also show the storage of inorganic perovskite quantum dots film monitored in three conditions. The film is that we glue the powder of quantum dots with PDMS evenly on the glass. The above experiments are all monitored as aging time to realize the change of spectrum and reliability.
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Das, Rahul Kumar. "Luminescent Heteroatom doped Carbon Quantum Dots for Sensing and Drug Delivery Applications." Thesis, 2019. http://ethesis.nitrkl.ac.in/10041/1/2019_PhD_RDas_513CY6080_Luminescent.pdf.
Full textAbstract:
The present dissertation entitled, “Luminescent Heteroatom doped Carbon Quantum Dots for Sensing and Drug Delivery Applications” is an embodiment of the investigations aimed at developing simple inexpensive synthetic methodologies for producing heteroatom doped carbon quantum dots pertinent for sensing and biomedical application. The diagnostic and therapeutic applications of these multifunctional nanomaterials have been studied in vitro. The thesis has been divided into seven chapters.
Hydrophilic boronic acid modified nitrogen sulphur doped carbon quantum dots (BNSCQD) have been prepared following a cost effective hydrothermal approach. The co-doping is aimed to improve the luminescence as well as targeting affinity of the CQD. Due to intense fluorescence property, appreciable photostability, boronic acid functionality and low cytotoxicity the carbon quantum dots (CQD) have been utilised in sensing glucosamine and cancer cell receptor Sialyl Lewisa (SLa). This method is highly sensitive and selective for visual detection of glucosamine sensing using a paper based sensor strip. Furthermore, integration of dopamine with BNSCQD (BNSCQD-Dopa) sets a platform for development of a fluorescence turn-on nanoprobe for fluoride detection in real samples. Due to boron’s affinity towards fluorine, the system was very selective towards fluoride when compared with other anions with a detection limit 0.7 pM. The practical ultrasensitive utility of the sensor is well demonstrated in human serum samples and also extended for fluoride detection in cellular environment. Further, the BNSCQD has been integrated with gadolinium iron oxide and mesoporous silica to construct a theranostic nanoparticle where BNSCQD imparts multiple functions such as simultaneous pH-sensitive gate opening, leading to control drug release, optical imaging, and receptor targeted internalization of the theranostic particle. The drug release experiment under variable pH and in the presence of competitive binding ligand SLa clearly shows the excellent responsiveness of the BNSCQD capped MSN hybrid system toward dual stimuli. Because of reasonably good r1 r2 relaxivities of the magnetic core and excellent fluorescence property of the doped carbon quantum dot, the hybrid can be utilized to monitor the therapeutic response through MRI and/or fluorescence imaging. Nitrogen doped mesoporous hollow carbon nanospheres (NCQD-HCS) have been prepared by inert calcination of polymer synthesized using pyrrole, aniline and Triton X-100 as molecular precursors. Here a direct synthetic approach is followed to yield high surface area carbon spheres with fluorescence property. An optimization of both surface area and photoluminescence is achieved by tuning temperature of calcination. The highest PL quantum yield of 14.6% is recorded, which is suitable for confocal imaging of cells. The fluorescence property of these spheres is attributed to the embedded nitrogen doped carbon quantum dots (NCQD) in carbon matrix. The photothermal property of NCQD-HCS has been investigated under 980 nm NIR irradiation. Cell killing efficacy of hollow spheres by photothermal ablation effect is evaluated in FaDu cells (oral cancer) as a modal cell line. Similarly, the upconversion property of carbon spheres is explored for light responsive drug release of gemcitabine. A highly biocompatible click chemistry based gating system is designed to restrict the premature release of drug molecules from porous nanospheres. The utilization of upconverted radiation by substituted nitrobenzyl linker, initiating its cleavage followed by drug release under periodic irradiation (980 nm laser) intervals has been tested in vitro. These fluorescent multifunctional nanoparticles provide a platform for combinatorial therapy of oral cancer.
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Coleman, Brian. "Synthesis, characterization and amphiphilic self-assembly of inorganic nanoparticles functionalized with polymer brushes of variable composition and chain length." Thesis, 2016. http://hdl.handle.net/1828/7244.
Full textAbstract:
The synthesis, characterization and amphiphilic self-assembly of polymer brush functionalized nanoparticles (PBNPs) using a block copolymer template is described herein. To study the effect of polymer brush composition on self-assembly, four samples were created using a mixture of PS-b-PAA (polystyrene-block-polyacrylic acid) and PMMA-b-PAA (poly(methyl methacrylate)-block-polyacrylic acid) diblock copolymers to create PBNPs with a CdS quantum dot (QD) core and different ratios of PS and PMMA in the coronal brush. Static light scattering showed that despite differences in brush composition, the PBNPs formed nanoparticles of similar aggregation number and chain density but showed evidence of asymmetric structure in a common solvent for both blocks at higher PS contents. After subsequent hydrolysis of the hydrophobic PMMA to hydrophilic poly(methacrylic acid) (PMAA), these amphiphilic particles were then self-assembled in THF/H2O solution in which it was determined that increasing the hydrophobic content of the brush composition, the initial nanoparticle concentration (c0) or the added salt content (RNaCl), would cause the assembly of low curvature assemblies. Compilation of this data allowed for the construction of phase diagrams for PBNP systems based on brush composition and c0 at different salt contents. Lastly, PS-b-PAA-b-PMMA triblock copolymers with variable PMMA chain length were assembled into PBNPs around a CdS QD core using a block copolymer template approach. Light scattering showed these particles also had similar aggregation number and chain density despite the difference in PMMA chain length. After hydrolysis of PMMA to PMAA these particles were then self-assembled in THF/H2O mixtures to determine the role of PMAA block length on the produced morphological structures. The resulting assemblies suggest that chain length played a minimal role in their self-assemblyGraduate
2018-09-15
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Bennett, Ellie. "Synthetic and Analytical Advancements for Zinc Sulfide Containing Quantum Dots." Thesis, 2021. https://doi.org/10.7916/d8-pg23-8v73.
Full textAbstract:
Colloidal semiconductor nanocrystals exist at the interface of inorganic chemistry, solid-state physics, and materials applications. The highly tunable and size-dependent properties position them as prime candidates for advancing a range of technologies, including improving efficiency in solid-state lighting devices and high color-purity displays. To be successful in these endeavors, quantum dots require excellent optical properties, such as bright emission. Optimization of a zinc sulfide coating is widely regarded as a key requirement to achieving these necessary performances. Even so, zinc sulfide nanocrystal chemistry remains underdeveloped.
This dissertation addresses these shortcomings and provides comprehensive synthetic and analytical tools to harness the potential of zinc sulfide containing nanocrystals. Chapter 1 introduces semiconductor nanocrystals, also referred to as quantum dots, and begins with a description of the size-dependent optical properties. Factors that lead to poorer emission properties, such as undercoordinated surface atoms are discussed. Methods to alleviate these issues, including controlling the surface coordination environment, and design and growth of heterostructures are introduced. Lastly, synthetic approaches and nanocrystal formation mechanisms are described.
Chapter 2 covers the synthesis and size-dependent optical properties of zinc sulfide nanocrystals. We find that commonly used solvents in nanocrystal reactions lead to the formation of polymeric byproducts that are challenging to purify away, and thus design the zinc sulfide synthesis such that these can be avoided. Leveraging a library of rate tunable thioureas the final nanocrystal size can be carefully controlled. The reactions follow a thermally activated growth process, with larger zinc sulfide nanocrystals accessible at higher temperatures. Most relevantly for later chapters, the surface coordination environment is highly important; bulkier zinc carboxylate ligands that cannot achieve high surface coverages result in higher growth rates. These results represent the most tunable size controls reported for zinc sulfide nanocrystals.
Chapter 3 uses high resolution electron microscopy techniques to study the shape (morphology) of zinc sulfide nanocrystals, synthesized using the methods developed in the second chapter. Irregular, anisotropic growth is commonly seen in zinc sulfide shell growth and is attributed to core/shell interfacial strain. We find that this growth also occurs in the binary zinc sulfide system. Synthetic conditions favoring fast growth result in unselective, isotropic growth of spherical zinc sulfide. Conversely, slower conditions can lead to irregular, anisotropic shapes. The shape is also highly dependent on the coordination environment during growth. Small, sterically unencumbered ligands stabilize specific crystal facets, leading to selective, anisotropic growth. These findings are translated to shelling procedures in Chapter 6, and further emphasize the need to understand and characterize zinc sulfide surfaces.
Chapter 4 establishes an empirical relationship between the band gap energy of a zinc sulfide nanocrystal and its diameter. The literature reports a wide spread of diameters for a given energy, meaning zinc sulfide sizes could not previously be easily calculated from their optical properties. Leveraging the size- and shape-control discussed in Chapters 2 and 3, we assess the utility of a range of nanocrystal characterization techniques for accurately sizing quantum confined zinc sulfide. Using electron microscopy and X-ray scattering methods we present an updated energy-size (“sizing curve”) relationship for zinc sulfide. These results represent the most comprehensive zinc sulfide nanocrystal sizing study and enable the rapid size characterization of zinc sulfide from its absorbance spectrum. This provided crucial insight into the reaction progressions described in Chapter 2.
Chapter 5 covers our endeavors to characterize and quantify the zinc sulfide nanocrystal surface chemistry, which we believe is imperative to improving shelling procedures and optical properties in zinc sulfide heterostructures. With no published extinction coefficient, the surface coverages of zinc sulfide cannot be obtained. Using the size- and shape-controlled syntheses, in conjunction with optical absorption spectroscopy and elemental analysis, we calculate extinction coefficients for a range of zinc sulfide nanocrystal sizes. The size-dependence is well described by a power law, and this represents the first reported extinction coefficient for zinc sulfide. Using this, we report the first surface coverages of zinc sulfide nanocrystals and assess the binding affinity of zinc carboxylates to the surface by monitoring their displacement by L-type ligands.
Chapter 6 widens the zinc sulfide synthetic methods developed in earlier chapters to deposit zinc sulfide shells onto blue-emitting II-VI and red-emitting III-V nanocrystals. The reaction shows versatility, shelling nanocrystals over a wide range of temperatures. We demonstrate morphology control over the zinc shell by altering the deposition kinetics and coordination environment. Usually, thick, homogenous shells are desired by the nanocrystal field. However, by correlating the shell morphology to its optical properties, we see that the anisotropic shells generally achieve higher photoluminescence quantum yields (PLQYs). We also report progress towards cadmium-free quantum dot downconverters for use in solid-state lighting applications. Among other things, the photoluminescence intensity evolution throughout the shelling procedure is highly dependent on the initial surface termination of the nanocrystal core. Application of surface treatments allows brighter zinc sulfide shelled III-V heterostructures to be accessed.
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Ying-ChihChen and 陳應誌. "Investigation of Inorganic Quantum Dots in Light-Emitting Diodes and Nonvolatile Organic Memory Elements." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20046002711054135721.
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Chang, Ching-Chieh, and 張景傑. "Microwave-assisted Solvothermal Synthesis and Luminescence of All-Inorganic Perovskite Quantum Dots and Their Derivatives." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/pju38w.
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碩士國立交通大學
應用化學系碩博士班
106
The required working voltage of WLED is small, and its brightness is high. There is no harmful mercury in WLED. In recent years, the related products have been vigorously promoted to replace the traditional incandescent lamps to achieve the effect of saving energy. Compared to tradition phosphors, luminescent QDs have high PLQY, narrow emission and tunable emissions ranging in the UV to Vis spectral range. As a result, tradition phosphors have been slowly replaced by QDs. The thrust of my master thesis is on the synthesis of zero–dimension PQDs (CsPbX3, X = Cl, Br, I) nanomaterials by microwave-assisted solvothermal method for WLED applications. Most of the PQDs with the best optoelectronic properties are synthesized by toxic lead-containing quantum dots. Hence, my study focuses on divalent cation doped colloidal CsPb1−xMxBr3 PQDs (M = Sn, Mn) featuring partial cation exchange. Finally, WLED is fabricated by using the as-prepared green and red-emitting CsPbX3 QDs as color conversion materials on 450 nm blue LED chip.
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Mu, Zuze. "Synthesis, photostability and photocatalytic properties of water-suspended cadmium selenide and cadmium selenide/cadmium sulfide quantum dots." Thesis, 2005. http://hdl.handle.net/1911/17807.
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Photocatalysis offers exciting opportunities in the development of a renewable energy source and environmentally-friendly chemical processes. Previous studies focused on titanium dioxide and non-oxide semiconductor nanoparticles (quantum dots), such as CdS, ZnS, MoS2 for photocatalytic breakdown of organic molecules. Catalytic performance has been limited by materials issues, e.g. low quantum yields and photocorrosion. CdSe quantum dots are a model semiconductor nanoparticle material with great potential in luminescence application, but they have not been studied for photocatalysis. In this study, the synthesis of the water-suspended CdSe and CdSe/CdS quantum dots was thoroughly studied. The CdSe and CdSe/CdS core/shell quantum dots were found to photocatalyze the degradation of 4-nitrophenol in water upon the UV-vis irradiation. Quantum efficiencies were low. The pH of the suspending fluid was found to be important in controlling colloidal stability, chemical stability, and reaction during irradiation.
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Yang, Chung-He, and 楊衷核. "Fabrication of High-Efficiency Nano-OLED devices based on Inorganic Quantum Dots and Sol-Gel Process." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/97117255087847032723.
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博士國立交通大學
應用化學系所
95
The goal of this study is aimed to improve the performance of the light emitting diodes by introducing inorganic quantum dots and sol-gel process. In the first part, a new series of sulfide-containing polyfluorene homopolymers and copolymers (PFS, PF1, PF3 and PF4) comprised of aryl bromide and bronic ester moieties were synthesized by Ni(0)-mediated Yamamoto coupling and palladium-catalyzed Suzuki polymerizations. Three other polyfluorenes (PF2, PF5 and PFC6) without sulfur atom in the alkyl side chains were also synthesized by a similar method for comparison purpose. These fluorene-based polymers were characterized using FT-IR spectroscopy, elemental analysis, DSC, TGA, photoluminescence (PL) spectroscopy. The synthesized polymers PFS, PF1-PF3 emit blue light at around 440-468 nm, while copolymers PF4 and PF5 emit green light at 540 nm. In the annealing experiments, these polymer films show better stability against thermal-oxidation than polymer PFC6. Sulfide-containing polymers show not only good electroluminescent color stability, but their EL spectra also remain unchanged at high driving voltage. A double-layer electroluminescent device with the configuration of ITO/PEDOT/PF1/CsF/Al exhibited a stable sky-blue emission with CIE (0.21, 0.23) at 10 V, which showed a maximum brightness of 2991 cd/m2 at 8 V (75 mA/cm2) and a maximum efficiency of 1.36 cd/A. Finally, by ligand exchange process, the sulfur element could form coordination bonding with quantum dots, and PLED devices using these new QDs-containing organic/inorganic hybrid materials as light emitting layers exhibited superior or comparable EL performance compared to those without quantum dots. Organic semi-conductors show efficient electroluminescence which has led to their commercialization in LEDs. However, they have been marred by the thorniest problem of solid-state quenching. In the second part, we report the synthesis and characterization of two fluorene-based blue amphiphilic emitters containing triphenylamine or anthracene side groups. The formation of the hybrid meso-structured nanocomposites by sol-gel co-assembly with tetraethyl ortho-silicate was demonstrated, and the molecular interactions within the mesophases were studied. The blue light luminescent films made of fluorene-based amphiphile/silica co-assembled nanocomposite have been successfully prepared with enhanced emission. Different kinds of light emitting devices based on these nanocomposites showed improved efficiencies several times higher than the corresponding pristine chromophores. Furthermore, we report the synthesis and characterization of cyclometalated iridium complex which emits sky-blue light. The hybrid meso-structured nanocomposites by sol-gel co-assembly with tetraethyl ortho-silicate and the molecular interactions within the mesophases were also demonstrated. Electroluminescent devices were fabricated using carbazole-based precursor and iridium complex act as host/guest system through co-assembled sol-gel process. Light emitting devices based on these nanocomposites showed improved efficiencies several times higher than similar chromophore elaborated in the literature. The demonstration of nano-sized chromophoric amphiphiles/silica architecture may offer an easier strategy for fabricating high-efficiency phosphorescent OLEDs.
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Greenberg, Matthew William. "Formation Mechanism of Monodisperse Colloidal Semiconductor Quantum Dots: A Study of Nanoscale Nucleation and Growth." Thesis, 2020. https://doi.org/10.7916/d8-gcwz-ak10.
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Since the fortuitous discovery of the existence of quantum size effects on the band structure of colloidal semiconductor nanocrystals, the development of synthetic methods that can form nanoscale crystalline materials of controllable size, shape, and composition has blossomed as an empirical scientific achievement. The fact that the term “recipe” is commonly used within the context of describing these synthetic methods is indicative of the experimentally driven nature of the field. In this respect, the highly attractive photophysical properties of semiconductor nanocrystals—as cheap wavelength tunable and high quantum yield absorbers and emitters of light for various applications in lighting, biological imaging, solar cells, and photocatalysis—has driven much of the interest in these materials. Nevertheless, a more rigorously predictive first-principles-grounded understanding of how the basic processes of nanocrystal formation (nucleation and growth) lead to the formation of semiconductor nanocrystals of desired size and size dispersity remains an elusive practical and fundamental goal in materials chemistry. In this thesis, we describe efforts to directly study these dynamic nucleation and growth processes for lead chalcogenide nanoparticles, in many cases in-situ, using a mixture of X-ray scattering and UV-Vis/NIR spectroscopy.
The lack of a rigorously predictive and verified mechanism for nanocrystal formation in solution for many material systems of practical interest is due both to the inherent kinetic complexity of these reactions, as well as the spectroscopic challenge of finding in-situ probes that can reliably monitor nanoscale crystal growth. In particular, required are direct time-resolved structural probes of metastable inorganic amorphous and crystalline intermediates formed under the high temperature inert conditions of nanocrystal synthesis. It is, at the very least, highly challenging to apply many of the standard spectroscopic tools of mechanistic inorganic and organic chemistry such as ¹H NMR spectroscopy, IR vibrational spectroscopy, and mass spectrometry to this task. A notable counterexample is, of course, UV-vis/NIR absorbance and emission spectroscopies, which are of great value to the studies described herein. Nevertheless, to address this relative dearth of conventional spectroscopic probes, here we explore the use of X-ray Total Scattering real space Pair Distribution Function (PDF) analysis and Small Angle X-ray Scattering (SAXS) techniques to directly probe the crystallization process in-situ. Time-resolved measurements of the small angle reciprocal space scattering data allow mapping of the time evolution of the colloidal size and concentration of the crystals during synthesis, while the Fourier transform of scattering data over a wide range of reciprocal space provides direct insight into the local structure. Through this approach, we compare direct observations of these nucleation and growth processes to the widely cited theoretical models of these processes (Classical Nucleation Theory and LaMer “Burst Nucleation”) and find a number of stark differences between these widely cited theories and our experiments.
The first two chapters cover the results of these 𝘪𝘯-𝘴𝘪𝘵𝘶 diffraction studies. Chapter 1 focuses on small angle X-ray scattering data collection and modeling. Chapter 2 focuses upon lead sulfide and lead selenide real space PDF analysis of local structural evolution during synthesis. Finally, Chapter 3 discusses a project in which we examine the origins of emergent semiconducting electronic structure in an increasing size series of atomically precise oligomers of [Ru₆C(CO)₁₆]²⁻ bridged by Hg²⁺ and Cd²⁺ atoms. Using an atomically well-defined series of molecules that bridge the small molecule and nanoscale size regimes, we discuss the factors that give rise to controllable semiconductor electronic structure upon assembly into extended periodic structures in solution. In all these projects, we seek to highlight the value of applying concepts of molecular inorganic chemistry—ligand binding models, relative bond strengths, in addition to kinetics and thermodynamics—to explain our observations regarding nanocrystal nucleation and growth. Consideration of the chemistry of nanocrystal formation processes provides a valuable compliment to the physics-based classical models of nucleation and growth that do not explicitly consider the system specific molecular structure and bonding.