Articles de revues : « Colloidal NC »

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Pashchenko, G. A. « PHOTOLUMINESCENCE OF NANOCRYSTALLINE CdTe, INTRODUCED INTO POROUS SILICON ». Optoelektronìka ta napìvprovìdnikova tehnìka 56 (7 décembre 2021) : 123–28. http://dx.doi.org/10.15407/iopt.2021.56.123.

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A method of colloidal synthesis of monodisperse nanocrystals (NC) with high stability, narrow bands of photoluminescence (PL) and high quantum yield has been developed. The process of colloidal synthesis took place at room temperature and for the passivation of NC used a variety of surfactants. The surface of NC CdTe was modified by introducing them into a matrix, organic or crystalline. In our case, the matrix was porous Silicon (PS), that is a composite structure was formed on the basis of the matrix and NC semiconductor. Nanocomposite structures of PS – NC CdTe were obtained by introducing colloidal solutions of NC CdTe into the solid matrix of PS and subsequent processing at a certain temperature regime. The photoluminescent properties of a composite system in which the matrix is microcrystalline PS and the second component is NC CdTe deposited from a colloidal solution of NC CdTe have been studied. The peculiarity of this system is that both components have PL of different intensities.The large difference in PL intensities and different positions of the radiation bands allowed, comparing the PL spectra of the colloidal solution of NC CdTe, PS and NC CdTe – PS at different stages of introduction of CdTe nanoparticles into the porous Silicon surface, to identify the interaction and mutual influence of the two constituent materials. The main disadvantages of the method are its relative novelty, which leads to the need for empirical selection of some parameters of the synthesis. The planned change of properties of PS and colloidal solutions of NC CdTe by variation of technological methods of synthesis and processing methods will allow to control the physical properties of this composite system and use it to develop new principles of design and creation of new generation sensor devices.

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Ha, Don-Hyung. « (Invited) Building Nanostructured Film from Colloidal Nanocrystals through Electrophoretic Deposition ». ECS Meeting Abstracts MA2022-02, n^o 20 (9 octobre 2022) : 901. http://dx.doi.org/10.1149/ma2022-0220901mtgabs.

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Over the last few decades, a tremendous research effort has been dedicated to realizing colloidal nanocrystals (NCs) as useful devices. Contrary to the well-established synthesis of colloidal NCs, the fabrication method to transfer the NCs to a nanostructured film has not studied well, despite the importance of using NCs as integrated devices. Especially, an advanced fabrication technique is crucial for further improving device performance along with the fine colloidal synthesis and NC device applications. As an advanced technique, electrophoretic deposition (EPD) can be introduced to mitigate the limitations of traditional tools, such as spin-coating, drop-casting, and spray coating, by creating desirable NC thin films from colloidal solutions using an electric field. We found several key controllable parameters such as solvent, surfactant ligand, and voltage, to tune the NC film’s morphology as well as the mechanism of the NC deposition. To clearly understand the mechanism of the deposition, in-situ technique was also developed by utilizing a light scattering method, which can provide the real time tracking analysis.

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HIMMI, MUSTAPHA, et LAILA MOHAMMADI. « EXTENSIVE STUDY OF INTERACTION FORCE BETWEEN SPHERICAL COLLOIDS AND STAR POLYMERS ». International Journal of Modern Physics B 26, n^o 17 (21 juin 2012) : 1250105. http://dx.doi.org/10.1142/s0217979212501056.

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We consider a system consisting of very small colloidal particles clothed each by f end-grafted flexible polymer chains we regarded as star polymers, and hard spherical colloidal particles in a good solvent. Our main objective is to determine the expression of the interaction force between a spherical colloid and a star polymer as a function of distance between them. We limit ourselves to the case where the star polymer is smaller than the colloid. In the first part, the system is dissolved in a melt of short linear chains of polymerization degree P<N, where N denotes the polymerization degree of grafted chains. To compute the expected force, we consider two regimes: (1) high-grafting density [Formula: see text] and (2) small-grafting density (f < f*). For (f > f*), we show that the expression of the expected force coincides exactly with that of the case of a small molecular weight solvent. For (f < f*), we show that there is a change in behavior. In the second part, we assume that the lengths of the f grafted chains were randomly distributed and there is talk of a polydisperse star polymer. We show that the computation of the expected force depends on the relative values of the polymerization degree of longest grafted chain, N, when it is compared to the typical one Nc ~ f1/(α-1). Here α is the polydispersity exponent. We distinguish two regimes depending on whether N < Nc or N > Nc. For the regime with N < Nc, and comparing the expression of the force obtained for the monodisperse case, we can say that the polydispersity of grafted chains induce a drastic change of the force expression. For the regime with N > Nc, we found the existence of two distance-ranges. For small distances, the effective force expression is identical to that relative to the above case (N < Nc). But for high distances, the effective force expression is similar to the monodisperse case.

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González-Rubio, Guillermo, Holger Hilbert, Rose Rosenberg, Bing Ni, Lisa Fuhrer et Helmut Cölfen. « Simple Determination of Gold Nanocrystal Dimensions by Analytical Ultracentrifugation via Surface Ligand-Solvent Density Matching ». Nanomaterials 11, n^o 6 (28 mai 2021) : 1427. http://dx.doi.org/10.3390/nano11061427.

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Analytical ultracentrifugation (AUC) is a powerful technique to observe colloidal nanocrystals (NCs) directly in solution and obtain critical information about their physical-chemical properties. Nevertheless, a more comprehensive implementation of AUC for the characterisation of such a class of crystalline colloids has been traditionally impaired by the requirement of having a priori knowledge of the complex, multilayered structure formed by NC in solution. This includes the nature (density and mass) of the surface ligands (SLs) that provide NC colloidal stability and the shell of solvent molecules formed on it. Herein, we propose a methodology to determine the NCs size by using SLs with a density equal to that of the solvent. Thereby, the buoyancy force of the SL shell is neutral, and the density of the NCs is sufficient a priori knowledge to calculate their related mass and size distributions. The simplicity and reliability of the method are evaluated with cetyltrimethylammonium bromide (CTAB) stabilized spherical gold NCs (AuNCs) of dimensions ranging from 1 to 17 nm. The proposed method has great potential to be transferred to any non-crystalline and crystalline colloids of different nature and composition, which have a density that is equal to the bulk and can be stabilized by SLs having a density that matches that of the solvent.

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Kapush, О. A., I. O. Mazarchuk, L. І. Trіshchuk, V. Y. Morozovska, S. D. Boruk, S. I. Budzulyak, D. V. Korbutyak, B. N. Kulchitsky, O. G. Kosinov et R. G. Abaszade. « Influence of the nature of the dispersion medium on the optical properties of CdTe nanocrystals during sedimentation deposition ». Chernivtsi University Scientific Herald. Chemistry, n^o 819 (2019) : 7–11. http://dx.doi.org/10.31861/chem-2019-819-01.

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The physicochemical properties of low-dimensional structures based on CdTe obtained are investigated by the method of colloidal synthesis. The analysis of the optical absorption spectra and the luminescence intensity of the CdTe colloidal NCs showed that the nature of the dispersion medium significantly affects their optical properties. The optical absorption spectra of the CdTe NK fractions obtained by dissolving the flocs in deionized water and in deionized water with the addition of NaOH have been shown to have the same character. However, the addition of NaOH results in a shift of the absorption maximum by 8-12 nm into the longwave region. This suggested that the addition of NaOH to the colloidal solution of NK CdTe during sedimentation deposition leads to the aggregation of cadmium telluride particles. The addition of NaOH results in the quenching of photoluminescence. It can be assumed that during the sedimentation deposition there is a leaching of THC to a critical concentration, therefore, due to insufficient stabilization of the surface of the NC CdTe, a rapid aggregation of particles occurs and a loss of sedimentation stability of the solution is observed, which causes the PL quenching. The analysis of the optical absorption and photoluminescence spectra of the fractions of the colloidal solution of NC CdTe obtained by using DMF as a dispersion medium during the sedimentation deposition leads to the conclusion that the nature of the dispersion medium significantly affects the optical properties of CdTe NC. The maxima of the OP spectra corresponding to the first exciton transition of all fractions are shifted to the longwave region and change their shape compared to the corresponding spectra for the aqueous fractions. In this case, the PL intensity of the first and second fractions of CdTe NC in DMF is approximately 100 ppm. exceeds the PL intensity of the aqueous fractions, which can be explained by the fact that DMF, unlike deionized water, does not wash out THC from the surface of the CdTe NC.

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Chandran, Bevita K., Sjoerd A. Veldhuis, Xin Yu Chin, Annalisa Bruno, Natalia Yantara, Xiaodong Chen et Subodh Mhaisalkar. « Precursor non-stoichiometry to enable improved CH3NH3PbBr3 nanocrystal LED performance ». Physical Chemistry Chemical Physics 20, n^o 8 (2018) : 5918–25. http://dx.doi.org/10.1039/c7cp07827g.

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Tamborra, M., M. Striccoli, M. L. Curri et A. Agostiano. « Hybrid Nanocomposites Based on Luminescent Colloidal Nanocrystals in Poly(methyl methacrylate) : Spectroscopical and Morphological Studies ». Journal of Nanoscience and Nanotechnology 8, n^o 2 (1 février 2008) : 628–34. http://dx.doi.org/10.1166/jnn.2008.a088.

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We report on preparation process and optical characterization of a nanocomposite material obtained dispersing colloidal semiconductor nanocrystals (NCs), namely CdS and CdSe@ZnS core–shell system in poly(methyl methacrylate) (PMMA). Such method allows a large flexibility on nanocrystal materials and on the choice of the polymer characteristics. Nanocomposite thin films were extensively investigated by means optical and morphological techniques. The effects on NC composition, concentration, size, and surface chemistry on the spectroscopical and structural behaviour of the nanocomposite properties were studied. The NC size dependent optical properties of the nanocomposites are mainly accounted by the NC composition and size, while the morphology of the films is explained on the base of the NC surface characteristics and their concentration in the nanocomposites.

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Kim, Ki-Joong, Richard P. Oleksak, Changqing Pan, Michael W. Knapp, Peter B. Kreider, Gregory S. Herman et Chih-Hung Chang. « Continuous synthesis of colloidal chalcopyrite copper indium diselenide nanocrystal inks ». RSC Adv. 4, n^o 32 (2014) : 16418–24. http://dx.doi.org/10.1039/c4ra01582g.

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A continuous synthetic method in a micro-tubular reactor is introduced for synthesizing mono-disperse and solution-stable chalcopyrite colloidal copper indium diselenide nanocrystal (CuInSe₂ NC) inks with potential scalability.

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Bastola, Ebin, Khagendra P. Bhandari, Anthony J. Matthews, Niraj Shrestha et Randy J. Ellingson. « Elemental anion thermal injection synthesis of nanocrystalline marcasite iron dichalcogenide FeSe2 and FeTe2 ». RSC Advances 6, n^o 74 (2016) : 69708–14. http://dx.doi.org/10.1039/c6ra06351a.

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We report a hot-injection colloidal method for the synthesis of nanocrystalline (NC) iron diselenide (FeSe₂), and iron ditelluride (FeTe₂) derived from iron(ii) bromide as the iron (Fe) precursor.

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Fullington, Barney G., Jim K. Park et Byung J. Kim. « Waste minimization and nitrocellulose fines removal at an ammunition plant ». Water Science and Technology 34, n^o 10 (1 novembre 1996) : 121–26. http://dx.doi.org/10.2166/wst.1996.0247.

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The Radford Army Ammunition Plant (RAAP) produces nitrocellulose (NC) as a major ingredient in tank and artillery ammunition propellant. Through the process of NC production, wastewater is generated which contains large quantities of NC in the micron and sub-micron size range. These suspended and colloidal particles are collectively called NC fines. Under the impetus of a proposed Ammunition Procurement and Supply Agency suspended solids effluent limit of 25 mg/l and a greater emphasis on pollution prevention, significant research has been conducted into the areas of waste minimization and NC fine removal at the RAAP. One aspect of the current research involved a field study at the RAAP. The purpose of the field study was to inspect and discuss the entire NC production process with the operators, foremen, and NC production supervisor. With the information collected at the RAAP, it was possible to propose several waste minimization schemes and NC fines removal alternatives. From existing data, it was calculated that the proposed pollution prevention ideas could save the RAAP approximately $1,500,000 annually.

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Asadov, S. M. « Kinetic Monte Carlo simulation of the growth of CdSe nanocrystals ». BULLETIN of the L.N. Gumilyov Eurasian National University. Chemistry. Geography. Ecology Series 134, n^o 1 (2021) : 7–23. http://dx.doi.org/10.32523/2616-6771-2021-134-1-7-23.

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This article is devoted to modeling the kinetics of colloidal crystallization of cadmium selenide (CdSe) nanoparticles (NPs). The kinetic equation is modified, considering the contributions of the reaction rate constants of individual stages. It includes the reaction rate constants, thermodynamic and calculated parameters, and physical properties. There is used modified kinetic model based on the crystallization equation. There are considered the contributions of adsorption, desorption, and migration of nucleated particles at different times. Modified model assumes that, upon crystallization of NPs CdSe, monomer units depend on the frequency of attachment and detachment transitions of the monomer–CdSe complex. In this case, the transformation of the precursor into a monomer, the formation of an effective monomer and nucleation pass into the growth stage of (NC CdSe) nanocrystals with a seeded mass. In the process, the resulting nanocluster will continue to grow due to early maturation, aging, and subsequent growth into larger NC CdSe. The Kinetic Monte Carlo method (KMC) is used to approximate the model of the nucleation–growth of NC considering different contributions to the reaction rate constants. The modified model with the use of KMC allows to describe the dependences of the kinetic rate constants on the average radius of nanoparticles as a function of time, concentration, and distribution of NC CdSe at a given time. There are described conditions for the formation of NPs CdSe with an evolutionary distribution function of NC CdSe in size space. The results of modeling the kinetics of colloidal crystallization of CdSe can be used to control nucleation rate and growth of NPs CdSe, as well as similar systems in the formation of high-quality NC.

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Budzulyak, S. I., V. M. Yermakov, O. A. Kapush, D. V. Korbutyak, V. М. Tomashyk, Z. F. Tomashyk, L. I. Trishchuk, S. D. Boruk et L. A. Demchyna. « Photoluminescent Properties of CdTe Nanocrystals in Colloidal Solutions and Polymer Films ». Фізика і хімія твердого тіла 17, n^o 1 (15 mars 2016) : 60–64. http://dx.doi.org/10.15330/pcss.17.1.60-64.

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Using stabilizers and promoters we have obtained colloidal CdTe nanocrystals (NCs) in aqueous solutions. Incorporation of the CdTe NCs into polymer films has been fulfilled subsequently. It is shown that the use of vinyl acetate-acrylate copolymer as the matrix material for CdTe NC incorporation from colloidal solutions allows to get stable and nontoxic nanoheterogeneous film structures, which are characterized by satisfactory values of the photoluminescence quantum yield. Photoluminescence characteristics of the studied materials have been analyzed.

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Yun, Hongseok, et Taejong Paik. « Colloidal Self-Assembly of Inorganic Nanocrystals into Superlattice Thin-Films and Multiscale Nanostructures ». Nanomaterials 9, n^o 9 (1 septembre 2019) : 1243. http://dx.doi.org/10.3390/nano9091243.

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The self-assembly of colloidal inorganic nanocrystals (NCs) offers tremendous potential for the design of solution-processed multi-functional inorganic thin-films or nanostructures. To date, the self-assembly of various inorganic NCs, such as plasmonic metal, metal oxide, quantum dots, magnetics, and dielectrics, are reported to form single, binary, and even ternary superlattices with long-range orientational and positional order over a large area. In addition, the controlled coupling between NC building blocks in the highly ordered superlattices gives rise to novel collective properties, providing unique optical, magnetic, electronic, and catalytic properties. In this review, we introduce the self-assembly of inorganic NCs and the experimental process to form single and multicomponent superlattices, and we also describe the fabrication of multiscale NC superlattices with anisotropic NC building blocks, thin-film patterning, and the supracrystal formation of superlattice structures.

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Vittorio, M., F. Pisanello, L. Martiradonna, A. Qualtieri, T. Stomeo, A. Bramati et R. Cingolani. « Recent advances on single photon sources based on single colloidal nanocrystals ». Opto-Electronics Review 18, n^o 1 (1 janvier 2010) : 1–9. http://dx.doi.org/10.2478/s11772-009-0026-7.

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AbstractSingle colloidal quantum dots (QDs) are increasingly exploited as triggered sources of single photons. This review reports on recent results on single photon sources (SPS) based on colloidal quantum dots, whose size, shape and optical properties can be finely tuned by wet chemistry approach. First, we address the optical properties of different colloidal nanocrystals, such as dots, rods and dot in rods and their use as single photon sources will be discussed. Then, we describe different techniques for isolation and positioning single QDs, a major issue for fabrication of single photon sources, and various approaches for the embedding single nanocrystals inside microcavities. The insertion of single colloidal QDs in quantum confined optical systems allows one to improve their overall optical properties and performances in terms of efficiency, directionality, life time, and polarization control. Finally, electrical pumping of colloidal nanocrystals light emitting devices and of NC-based single photon sources is reviewed.

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She, Xing-jin, Qiang Zhang, Cai-Feng Wang et Su Chen. « New insights into the phosphine-free synthesis of ultrasmall Cu2−xSe nanocrystals at the liquid–liquid interface ». RSC Advances 5, n^o 110 (2015) : 90705–11. http://dx.doi.org/10.1039/c5ra18313h.

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A liquid–liquid interfacial strategy to prepare ultra small (<5 nm) colloidal Cu₂₋xSe NCs with blue-fluorescence, noncaustic and environmentally friendly NH₄SCN replaces the long-chain organic ligands for fabrication of NC-sensitized solar.

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Dzhagan, Volodymyr, Oleksandr Selyshchev, Serhiy Kondratenko, Nazar Mazur, Yevhenii Havryliuk, Oleksandra Raievska, Oleksandr Stroyuk et Dietrich R. T. Zahn. « Copper-Content Dependent Structural and Electrical Properties of CZTS Films Formed by “Green” Colloidal Nanocrystals ». Electronic Materials 3, n^o 1 (20 mars 2022) : 136–53. http://dx.doi.org/10.3390/electronicmat3010013.

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Thin films of colloidal CZTS nanocrystals (NCs) synthesized using a “green” approach in water with a variation of the copper-to-tin ratio are investigated by Raman scattering, mid-infrared (molecular vibrations) and near-infrared (free carrier) absorption, X-ray photoemission spectroscopy (XPS), electrical conductivity, and conductive atomic force microscopy (cAFM). We determined the effect of the actual Cu content on the phonon spectra, electrical conductivity, and spectral parameters of the plasmon band. An increase in the electrical conductivity of the NC films upon annealing at 220 °C is explained by three factors: formation of a CuxS nanophase at the CZTS NC surface, partial removal of ligands, and improved structural perfection. The presence of the CuxS phase is concluded to be the determinant factor for the CZTS NC film conductivity. CuxS can be reliably detected based on the analysis of the modified Auger parameter of copper, derived from XPS data and corroborated by Raman spectroscopy data. Partial removal of the ligand is concluded from the agreement of the core-level XPS and vibrational IR spectra. The degree of lattice perfection can be conveniently assessed from the Raman data as well. Further important information derived from a combination of photoelectron and optical data is the work function, ionization potential, and electron affinity of the NC films.

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Xie, Minghong, Wenxiao Gong, Lei Kong, Yang Liu, Yang Mi, Heng Guo et Sheng-Nian Luo. « Solution-processed whispering-gallery-mode microsphere lasers based on colloidal CsPbBr₃ perovskite nanocrystals ». Nanotechnology 33, n^o 11 (23 décembre 2021) : 115204. http://dx.doi.org/10.1088/1361-6528/ac4131.

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Abstract Perovskite nanocrystals (NCs) have emerged as attractive gain materials for solution-processed microlasers. Despite the recent surge of reports in this field, it is still challenging to develop low-cost perovskite NC-based microlasers with high performance. Herein, we demonstrate low-threshold, spectrally tunable lasing from ensembles of CsPbBr3 NCs deposited on silica microspheres. Multiple whispering-gallery-mode lasing is achieved from individual NC/microspheres with a low threshold of ∼3.1 μJ cm−2 and cavity quality factor of ∼1193. Through time-resolved photoluminescence measurements, electron–hole plasma recombination is elucidated as the lasing mechanism. By tuning the microsphere diameter, the desirable single-mode lasing is successfully achieved. Remarkably, the CsPbBr3 NCs display durable room-temperature lasing under ∼107 shots of pulsed laser excitation, substantially exceeding the stability of conventional colloidal NCs. These CsPbBr3 NC-based microlasers can be potentially useful in photonic applications.

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Gutiérrez-Lazos, Claudio Davet, Mauricio Ortega-López, Manuel A. Pérez-Guzmán, A. Mauricio Espinoza-Rivas, Francisco Solís-Pomar, Rebeca Ortega-Amaya, L. Gerardo Silva-Vidaurri, Virginia C. Castro-Peña et Eduardo Pérez-Tijerina. « Optical and structural characterization of oleic acid-stabilized CdTe nanocrystals for solution thin film processing ». Beilstein Journal of Nanotechnology 5 (20 juin 2014) : 881–86. http://dx.doi.org/10.3762/bjnano.5.100.

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This work presents results of the optical and structural characterization of oleic acid-stabilized cadmium telluride nanocrystals (CdTe-NC) synthesized by an organometallic route. After being cleaned, the CdTe-NC were dispersed in toluene to obtain an ink-like dispersion, which was drop-cast on glass substrate to deposit a thin film. The CdTe-NC colloidal dispersion as well as the CdTe drop-cast thin films were characterized with regard to the optical and structural properties. TEM analysis indicates that the CdTe-NC have a nearly spherical shape (3.5 nm as mean size). Electron diffraction and XRD diffraction analyses indicated the bulk-CdTe face-centered cubic structure for CdTe-NC. An additional diffraction line corresponding to the octahedral Cd3P2 was also detected as a secondary phase, which probably originates by reacting free cadmium ions with trioctylphosphine (the tellurium reducing agent). The Raman spectrum exhibits two broad bands centered at 141.6 and 162.3 cm−1, which could be associated to the TO and LO modes of cubic CdTe nanocrystals, respectively. Additional peaks located in the 222 to 324 cm−1 range, agree fairly well with the wavenumbers reported for TO modes of octahedral Cd3P2.

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Luo, Kaiying, Wanhua Wu, Sihang Xie, Yasi Jiang, Shengzu Liao et Donghuan Qin. « Building Solar Cells from Nanocrystal Inks ». Applied Sciences 9, n^o 9 (8 mai 2019) : 1885. http://dx.doi.org/10.3390/app9091885.

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The use of solution-processed photovoltaics is a low cost, low material-consuming way to harvest abundant solar energy. Organic semiconductors based on perovskite or colloidal quantum dot photovoltaics have been well developed in recent years; however, stability is still an important issue for these photovoltaic devices. By combining solution processing, chemical treatment, and sintering technology, compact and efficient CdTe nanocrystal (NC) solar cells can be fabricated with high stability by optimizing the architecture of devices. Here, we review the progress on solution-processed CdTe NC-based photovoltaics. We focus particularly on NC materials and the design of devices that provide a good p–n junction quality, a graded bandgap for extending the spectrum response, and interface engineering to decrease carrier recombination. We summarize the progress in this field and give some insight into device processing, including element doping, new hole transport material application, and the design of new devices.

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Adachi, Yasuhisa, Azusa Kobayashi et Motoyoshi Kobayashi. « Structure of Colloidal Flocs in relation to the Dynamic Properties of Unstable Suspension ». International Journal of Polymer Science 2012 (2012) : 1–14. http://dx.doi.org/10.1155/2012/574878.

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Dynamic behaviors of unstable colloidal dispersions are reviewed in terms of floc formation. Geometrical structure of flocs in terms of chemical conditions and formation mechanics is a key to predict macroscopic transportation properties. The rate of sedimentation and rheological properties can be described with the help of fractal dimension (D) that is the function of the number of contacts between clusters (Nc). It is also well known that the application of water soluble polymers and polyelectrolytes, which are usually used as a conditioner or flocculants in colloidal dispersions, critically affects the process of flocculation. The resulted floc structure is also influenced by the application of polymer. In order to reveal the roles of the polymers, the elementary rate process of polymer reaching to colloidal interface and subsequent reconformation process into more stable adsorption state are needed to be analyzed. The properties of permeable flocs and adsorbed polymer (polyelectrolyte) layers formed on the colloidal surfaces remain to be worked out in relation to inhomogeneous porous structure and electrokinetics in the future.

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Qiao, Fen. « Semiconductor Nanocrystals for Photovoltaic Devices ». Materials Science Forum 852 (avril 2016) : 935–38. http://dx.doi.org/10.4028/www.scientific.net/msf.852.935.

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Recently, photovoltaic devices based on colloidal semiconductor nanocrystals (NCs) have attracted a great interest due to their flexible synthesis with tunable band gaps and shape-dependent optical and electronic properties. However, the surface of NCs typically presents long chain with electrically insulating organic ligands, which hinder the device applications for NCs. So the major challenge of NCs for photovoltaic devices application is to decrease the inter NC space and the height of the tunnel barriers among NCs, therefore increase the transport properties of NCs. In this article, recent development of colloidal semiconductor NCs and possible routes for improving transport properties of colloidal NCs were reviewed. Among those methods, the thermal annealing approach provides a simple and cost-effective way to fabricate superlattice and to decrease the inter-space among NCs, which may be used for the preparation of other nanocrystalline superstructure and functional devices.

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Ouma, Immaculate L. A., Paul Mushonga et Martin O. Onani. « Effects of Reaction Parameters on the Growth and Optical Properties of PbSe Nanocrystals ». Journal of Nano Research 34 (juillet 2015) : 79–89. http://dx.doi.org/10.4028/www.scientific.net/jnanor.34.79.

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Colloidal syntheses of PbSe nanocrystals (NCs) have been widely investigated and the properties of nanocrystals have been shown to vary with reaction conditions, time, concentration and chemistry of reagents as well as the surfactants used. In this work the effects of reaction temperature, solvents, ligand purity, lead and selenium sources on the optical and structural properties of PbSe nanocrystals were investigated. PbSe NCs synthesized at 90 °C were observed to be spherical and had a narrower size distribution as compared to those synthesized at higher temperatures. 1-octadecene, trioctylphosphine and oleylamine were investigated as solvents for NC synthesis with the non-coordinating solvent octadecene showing the fastest growth rate with medium sized NCs. The coordinating solvents trioctylphosphine and oleylamine produced larger and smaller NCs respectively; this could be attributed to solvent interference during NC nucleation and growth phases. Oleate ligands were used during these syntheses and the ligand purity was not observed to have a significant effect on the NC optical and structural properties. The selenium precursor used affected the NC size and their optical properties while the lead source influenced both the NC shape and size. Lead acetate produced cubic NCs which were larger than the spherical NCs obtained when lead oxide was used.

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Azhniuk, Yu M., V. V. Lopushansky, A. V. Gomonnai, B. V. Lopushanska, A. E. Raevskaya, V. M. Dzhagan, O. L. Stroyuk et D. R. T. Zahn. « Long-Term Stability of Optical Properties of Colloidal CdSe Nanocrystals in Polymer Matrices ». International Journal of Nanoscience 18, n^o 03n04 (juin 2019) : 1940052. http://dx.doi.org/10.1142/s0219581x19400520.

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Properties of CdSe nanocrystals (NCs) fabricated in aqueous solutions at relatively mild conditions in the presence of gelatine and stabilized in polymer (gelatine, gelatine + polyvinylpyrrolidone, polyvinyl alcohol) matrices are characterized by Raman, optical absorption and photoluminescence spectroscopies. The effect of heating of the reaction mixture on the average NC size is discussed.

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Dzhagan, Volodymyr, Oleksandr Stroyuk, Oleksandra Raievska, Oksana Isaieva, Olga Kapush, Oleksandr Selyshchev, Volodymyr Yukhymchuk, Mykhailo Valakh et Dietrich R. T. Zahn. « Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices ». Nanomaterials 10, n^o 12 (21 décembre 2020) : 2565. http://dx.doi.org/10.3390/nano10122565.

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The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging. Here, we report on the manifestations of photo-induced enhancement of photoluminescence (PL) of aqueous colloidal NCs embedded in water-soluble polymers. Based on the comparison of results obtained on bare and core/shell NCs, NCs of different compounds (CdSe, CdTe, ZnO) as well as different embedding polymers, we conclude on the most probable mechanism of the photoenhancement for these sorts of systems. Contrary to photoenhancement observed earlier as a result of surface photocorrosion, we do not observe any change in peak position and width of the excitonic PL. Therefore, we suggest that the saturation of trap states by accumulated photo-excited charges plays a key role in the observed enhancement of the radiative recombination. This suggestion is supported by the unique temperature dependence of the trap PL band as well as by power-dependent PL measurement.

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Zhou, Jigang, Xingtai Zhou, Xuhui Sun, Michael Murphy, Franziskus Heigl, Tsun-Kong Sham et Zhifeng Ding. « Electronic structures of CdSe nanocrystals — An X-ray absorption near-edge structure (XANES) investigation ». Canadian Journal of Chemistry 85, n^o 10 (1 octobre 2007) : 756–60. http://dx.doi.org/10.1139/v07-080.

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CdSe nanocrystals (NCs), capped with trioctylphosphine oxide and 1-octadecanamine, have been synthesized with colloidal methods. Both UV–vis absorption and photoluminescence spectra show that the prepared nanostructures exhibit a quantum confinement effect. X-ray absorption near–edge structure (XANES) at Se K-edge recorded in fluorescence yield mode have been carried out on these NCs, with different size and capping ligands to gain insight into how their electronic structures are affected by the NC size and chemical properties of the ligands. The results indicate that XANES are sensitive to both the NC size and the nature of the capping ligands. The whiteline intensity in XANES spectra can be related to the photoluminescence properties of these NCs.Key words: CdSe nanocrystals, capping ligands, X-ray absorption near-edge structure, UV–vis spectroscopy, photoluminescence.

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Wang, Jin Liang, Feng Wei, Guang Gang Qu et Zhi Qiang Shen. « Study of Colloidal Gold Strip in Detecting the Antibody of Porcine Epidemic Diarrhea ». Advanced Materials Research 647 (janvier 2013) : 538–42. http://dx.doi.org/10.4028/www.scientific.net/amr.647.538.

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Porcine Epidemic Diarrhea Virus (PEDV) infection has caused huge economic losses, but no serological method is available for batch detection of field samples. The aim of the study was to develop a method for large-batch detection of PEDV infection. Colloidal gold-labeled staphylococcal protein A (SPA) was sprayed on glass fibers to prepare a conjugate pad. The recombinant N protein of PEDV was blotted on the test line of the nitrocellulose (NC) membrane, and pig IgG was streaked on the control line of the NC membrane. The immunochromatographic strip was used for detection of antibodies against PEDV. The results showed that the strip test was simple and the results could be determined within 10 min with naked eyes. The test strip was highly specific for pig serum against PEDV and no cross-reaction was observed. The test strip had close similarity with ELISA. Storage at room temperature for 6 months did not affect the specificity and sensitivity obviously. A total of 320 clinical pig sera were detected by both ELISA and the developed test strip, and the coincidence was 96.3 %. Therefore, the developed immunochromatographic strip is specific, sensitive, stable, fast and simple, and it is suitable for on-site detection of antibodies against PEDV.

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Liang, Huamin, Fengming Zou, Liyi Fu, Qingwang Liu, Beilei Wang, Xiaofei Liang, Jing Liu et Qingsong Liu. « PEG-Bottlebrush Stabilizer-Based Worm-like Nanocrystal Micelles with Long-Circulating and Controlled Release for Delivery of a BCR-ABL Inhibitor against Chronic Myeloid Leukemia (CML) ». Pharmaceutics 14, n^o 8 (10 août 2022) : 1662. http://dx.doi.org/10.3390/pharmaceutics14081662.

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Drug nanocrystals, one of most common drug delivery systems, enable the delivery of poorly water-soluble drugs with high drug loading and enhanced dissolution. The rapid clearance and uncontrolled drug release of drug nanocrystals limit their delivery efficiency and clinical application. Herein, an amphiphilic co-polymer, poly oligo(ethylene glycol) methacrylate-b-poly(styrene–co-4-formylphenyl methacrylate) (POEGMA-b-P (St-co-FPMA), PPP), characterized by a hydrophilic part with bottlebrush-like oligo(ethylene glycol) methacrylate (OEGMA) side chains, was synthesized as stabilizers to fabricate a high-drug-loading nanocrystal micelle (053-PPP NC micelle) using the chronic myeloid leukemia (CML) drug candidate N-(2-methyl-5-(3-(trifluoromethyl)benzamido)phenyl)-4-(methylamino)pyrimidine-5-carboxamide (CHMFL-ABL-053 or 053) as a model drug. The 053-PPP NC micelle was characterized and subjected to in vitro and in vivo studies. It featured a worm-like shape of small size, high drug loading (~50%), high colloidal stability, and controlled release in vitro. The presence of the 053-PPP NC micelle resulted in a long-circulation property and a much higher AUC. The 053-PPP NC micelle induced higher accumulation in the tumor tissues under multiple continuous administration. For in vivo efficacy, the 053-PPP NC micelle with a longer dosing interval (96 h), beneficial for improving patient adherence, demonstrated superiority to the 053-F127 NC. The proposed stabilizer PPP and the 053-PPP NC micelle with high drug loading enables drug delivery with long circulation and controlled release of drugs. It is also promising for the development of more efficient nanocrystal-based intravenous injection formulations for poorly water-soluble drugs. It might also offer new possibilities for potential clinical application of the CML candidate drug 053.

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Boshernitsan, V. I., V. A. Smyntyna, V. M. Skobeeva et N. V. Malushin. « Synthesis of CdS Nanocrystalsin the Gelatin Matrix with Different рН Values and their Optical Properties ». Фізика і хімія твердого тіла 16, n^o 4 (15 décembre 2015) : 692–94. http://dx.doi.org/10.15330/pcss.16.4.692-694.

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We have investigated the influence of solution pH on the formation of nanocrystals and their size in the process of synthesis. We have analyzed the optical absorption spectra and luminescence of colloidal solutions of NC CdS.Nanocrystals of cadmiumsulphide were obtained by sol-gel technology in gelatin solution which has different pH values (6 ÷ 10). A decrease was observed in the average size of the nanocrystals from 8 till 3.5 nm while reducing pH from 10 to 6. There has been established the dependence of the contour of luminescence spectra from pH values.

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Sayevich, Vladimir, Chris Guhrenz et Nikolai Gaponik. « All-Inorganic and Hybrid Capping of Nanocrystals as Key to Their Application-Relevant Processing ». MRS Advances 3, n^o 47-48 (2018) : 2923–30. http://dx.doi.org/10.1557/adv.2018.445.

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AbstractThe design of the surface chemistry of colloidal semiconductor nanocrystals (NCs) presents a powerful synthetic approach that allows to tune the optical and electronic properties of the particles in independent and precisely desired manner, to provide chemical and colloidal stability in diverse media, and, finally, to control their targeted applicability ranging from catalysis, medicine to advanced electronic devices. In this article, we summarize the successful functionalization of colloidal NCs with specifically chosen ligands using a novel ligand-exchange strategy. To transform diverse colloidal NCs into a competitive class of solution-processed semiconductors for electronic applications, we replaced the pristine, insulating ligands with tiny inorganic and hybrid inorganic/organic species. The surface modification with inorganic ions modulates the charge carrier density in NC units and guarantees enhanced interparticle interactions. The subsequent functionalization of the all-inorganic-capped NCs with organic molecules leads to the formation of hybrid inorganic/organic-capped NCs. For example, the introduction of short amine molecules enables to preserve the optical and electronic characteristics of their all-inorganic counterparts, while extending the solubility range and improving the ability to form long-range ordered 2D and 3D superstructures. Moreover, these short amines can be further used as convenient axillary co-ligands facilitating the surface functionalization of all-inorganic NCs with other biocompatible molecules, such as polyethylene glycol (PEG). This opens further perspectives for NCs not only in optoelectronic but also in biological and medical applications.

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Rozhkov, K. I., E. Y. Yagudaeva, S. V. Sizova, M. A. Lazov, E. V. Smirnova, V. P. Zubov et A. A. Ischenko. « Characterization of iron-doped crystalline silicon nanoparticles and their modification with citrate anions for in vivo applications ». Fine Chemical Technologies 16, n^o 5 (28 novembre 2021) : 414–25. http://dx.doi.org/10.32362/2410-6593-2021-16-5-414-425.

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Objectives. This paper presents data on the development and study of the structural properties of iron-doped crystalline silicon (nc-Si/SiOx/Fe) nanoparticles obtained using the plasma-chemical method for application in magnetic resonance imaging diagnostics and treatment of oncological diseases. This work aimed to use a variety of analytical methods to study the structural properties of nc-Si/SiOx/Fe and their colloidal stabilization with citrate anions for in vivo applications.Methods. Silicon nanoparticles obtained via the plasma-chemical synthesis method were characterized by laser spark emission spectroscopy, atomic emission spectroscopy, Fouriertransform infrared spectroscopy, and X-ray photoelectron spectroscopy. The hydrodynamic diameter of the nanoparticles was estimated using dynamic light scattering. The toxicity of the nanoparticles was investigated using a colorimetric MTT test for the cell metabolic activity. Elemental iron with different Fe/Si atomic ratios was added to the feedstock during loading.Results. The particles were shown to have a large silicon core covered by a relatively thin layer of intermediate oxides (interface) and an amorphous oxide shell, which is silicon oxide with different oxidation states SiOx (0 ≤ x ≤ 2). The samples had an iron content of 0.8–1.8 at %. Colloidal solutions of the nanoparticles stabilized by citrate anions were obtained and characterized. According to the analysis of the cytotoxicity of the modified nanosilicon particles using monoclonal K562 human erythroleukemia cells, no toxicity was found for cells in culture at particle concentrations of up to 5 µg/mL.Conclusions. Since the obtained modified particles are nontoxic, they can be used in in vivo theranostic applications.

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Zingale, Elide, Angela Bonaccorso, Claudia Carbone, Teresa Musumeci et Rosario Pignatello. « Drug Nanocrystals : Focus on Brain Delivery from Therapeutic to Diagnostic Applications ». Pharmaceutics 14, n^o 4 (23 mars 2022) : 691. http://dx.doi.org/10.3390/pharmaceutics14040691.

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The development of new drugs is often hindered by low solubility in water, a problem common to nearly 90% of natural and/or synthetic molecules in the discovery pipeline. Nanocrystalline drug technology involves the reduction in the bulk particle size down to the nanosize range, thus modifying its physico-chemical properties with beneficial effects on drug bioavailability. Nanocrystals (NCs) are carrier-free drug particles surrounded by a stabilizer and suspended in an aqueous medium. Due to high drug loading, NCs maintain a potent therapeutic concentration to produce desirable pharmacological action, particularly useful in the treatment of central nervous system (CNS) diseases. In addition to the therapeutic purpose, NC technology can be applied for diagnostic scope. This review aims to provide an overview of NC application by different administration routes, especially focusing on brain targeting, and with a particular attention to therapeutic and diagnostic fields. NC therapeutic applications are analyzed for the most common CNS pathologies (i.e., Parkinson’s disease, psychosis, Alzheimer’s disease, etc.). Recently, a growing interest has emerged from the use of colloidal fluorescent NCs for brain diagnostics. Therefore, the use of NCs in the imaging of brain vessels and tumor cells is also discussed. Finally, the clinical effectiveness of NCs is leading to an increasing number of FDA-approved products, among which the NCs approved for neurological disorders have increased.

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Giancane, Gabriele, Chiara Ingrosso, M. Lucia Curri, Angela Agostiano et Ludovico Valli. « Tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine thin films : deposition, characterization and application ». Journal of Porphyrins and Phthalocyanines 14, n^o 08 (août 2010) : 741–51. http://dx.doi.org/10.1142/s1088424610002604.

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Thin films of pure tetrakis-(isopropoxy-carbonyl)-copper-phthalocyanine (TIPCuPc) , a novel functionalized phthalocyanine, and its hybrid junctions with colloidal rod-like TiO2 nanocrystals (NCs) were deposited in order to elucidate their properties and application in piezoelectric chemical sensors. The strong tendency of the phthalocyanine to assembly was confirmed at the air/water interface by advanced Brewster Angle Microscopy (BAM) and UV-vis reflection spectroscopy techniques. In particular, H-type aggregates, in situ and at the air/water interface, self-associate in aligned 3D bulky domains. The characteristics of the molecule and of the assemblies were studied in the solid state by means of UV-vis spectroscopy, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and Atomic Force Microscopy (AFM). These studies prompted investigation of the operating conditions to process the bare TIPCuPc and related TiO2 NC-based hybrid junctions as sensing active layers for phenol pollutants integrated in a Quartz Crystal Microbalance (QCM). Interestingly, the preferentially oriented phthalocyanine LB-film undergoes chemical interactions with the NC film, which enhances the sensitivity of the QCM sensor.

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Huang, Chibao, Shuai Kang, Fuxun Yu et Zairong Wei. « The Synthesis of a Two-Photon Fluorescence Labelling Probe and its Immunochromatographic Strip for Rapid Diagnosis of COVID-19 ». Australian Journal of Chemistry 74, n^o 7 (2021) : 522. http://dx.doi.org/10.1071/ch20344.

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A two-photon fluorescence labelling probe (LP) was synthesised, and LP-Ag was obtained by LP labelling the N-protein antigen (Ag) of COVID-19. LP-Ag was made into an immunochromatographic strip. When a blood sample was added to the sample hole of the test card, it would move forward along the nitrocellulose (NC) film. If the sample contained IgM, the IgM bound to LP-Ag and formed an M line with the coated mouse anti-human IgM antibody, giving a positive response to the presence of IgM of COVID-19. The sensitivity, specificity, and accuracy of the immunochromatographic strip based on the LP was compared with those of the nucleic acid detection method and the colloidal gold method, proving it to be much simpler than the nucleic acid detection method, which can greatly shorten the detection period, and to be much more stable than the colloidal gold method, which can overcome uncertainty. LP-Ag can be used to image lung tissue with COVID-19 by two-photon fluorescence microscopy (TFM).

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Zhao, Xiaoyu, Wei Xu, Xiuxia Tang, Jiahong Wen et Yaxin Wang. « Design of Ag/TiO2/Ag Composite Nano-Array Structure with Adjustable SERS-Activity ». Materials 15, n^o 20 (19 octobre 2022) : 7311. http://dx.doi.org/10.3390/ma15207311.

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How to fabricate large area controllable surface-enhanced Raman scattering (SERS) active nanostructure substrates has always been one of the important issues in the development of nanostructure devices. In this paper, nano-etching technology and magnetron sputtering technology are combined to prepare nanostructure substrate with evolvable structure, and Ag/TiO2/Ag composites are introduced into the evolvable composite structure. The activity of SERS is further enhanced by the combination of TiO2 and Ag and the electron transfer characteristics of TiO2 itself. Deposition, plasma etching, and transfer are carried out on self-assembled 200 nm polystyrene (PS) colloidal sphere arrays. Due to the shadow effect between colloidal spheres and the size of metal particles introduced by deposition, a series of Ag/TiO2/Ag nanostructure arrays with adjustable nanostructure substrates such as nano-cap (NC), nano cap-star (NCS), and nano particle-disk (NPD) can be obtained. These nanoarrays with rough surfaces and different evolutionary structures can uninterruptedly regulate optical plasmon resonance and reconstruct SERS hotspots over a large range, which has potential application value in surface science, chemical detection, nanometer photonics, and so on.

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Khalili, Adrien, Mariarosa Cavallo, Tung Huu Dang, Corentin Dabard, Huichen Zhang, Erwan Bossavit, Claire Abadie et al. « Mid-wave infrared sensitized InGaAs using intraband transition in doped colloidal II–VI nanocrystals ». Journal of Chemical Physics 158, n^o 9 (7 mars 2023) : 094702. http://dx.doi.org/10.1063/5.0141328.

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Narrow bandgap nanocrystals (NCs) are now used as infrared light absorbers, making them competitors to epitaxially grown semiconductors. However, these two types of materials could benefit from one another. While bulk materials are more effective in transporting carriers and give a high degree of doping tunability, NCs offer a larger spectral tunability without lattice-matching constraints. Here, we investigate the potential of sensitizing InGaAs in the mid-wave infrared throughout the intraband transition of self-doped HgSe NCs. Our device geometry enables the design of a photodiode remaining mostly unreported for intraband-absorbing NCs. Finally, this strategy allows for more effective cooling and preserves the detectivity above 108 Jones up to 200 K, making it closer to cryo-free operation for mid-infrared NC-based sensors.

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Yun, Hongseok. « (Invited, Digital Presentation) Understanding the Self-Assembly of Polymer-Grafted Nanocrystals ». ECS Meeting Abstracts MA2022-02, n^o 20 (9 octobre 2022) : 903. http://dx.doi.org/10.1149/ma2022-0220903mtgabs.

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Combination of inorganic nanocrystals (NCs) and polymeric materials is promising for the design of novel functional materials due to their complementary properties. For the preparation of such hybrid nanomaterials with tailored functionalities, it is important to precisely control their nanostructures since material properties of NCs strongly depend not only on the morphology of each NC building block, but also their assembled packing symmetries. In this talk, I will present precise control of polystyrene-grafted Au NC (Au@PS) superlattice symmetry, which shows non-conventional assembly behavior compared to short alkyl chain-coated NCs. Au@PS NCs were synthesized by ligand exchange using thiol-terminated PS with various molecular weights (M n). The Au@PS particles were self-assembled through liquid-air interface self-assembly process. Transmission electron microscopy images and grazing incidence small-angle X-ray scattering data indicated long-range ordered Au@PS superlattices. In particular, symmetry transitions from hexagonal close packing (hcp) to body centered cubic (bcc) symmetry were found as M n of PS increases or diameter of NCs decreases. We tried to understand the structural transitions by proposing “effective softness” model, which considers concentrated polymer brushes around NC surface as part of “hard core.” Finally, I will show how these polymer-grafted NCs can be self-assembled with block copolymers for the development of colloidal hybrid particles with stimuli-responsive photoluminescence behavior, which have great potential for the applications in smart material systems.

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Smyntyna, V. A., V. M. Skobeeva, K. A. Verheles et M. V. Malushin. « Influence of Organic Molecules on the Luminescent Properties of Composites Based on CdS Quantum Dots ». Фізика і хімія твердого тіла 18, n^o 4 (27 décembre 2017) : 426–30. http://dx.doi.org/10.15330/pcss.18.4.430.

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The influence of methylene blue (MB) and acridine yellow (AY) dyes on the spectra of luminescence of CdS with quantum dots (QD) dye composites is investigated. It is shown that the luminescence spectrum of the heterosystem of nanocrystals (NC) CdS – the dye depends on the absorption region of it. The spectrum of the luminescence of the quantum dots is shifted to the red region by the introduction into the colloidal solution of the MB dye and in a case of the insertion of AY the spectrum is shifted into the blue region. The obtained results are explained in a point of view of the transferring the energy from the CdS quantum dots to the dyes by the Forster mechanism.

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Quiñones-Galván, J. G., K. Y. Sillas-Montaño, L. P. Rivera, J. S. Arias-Cerón, A. Pérez-Centeno, M. A. Santana-Aranda, A. Chávez-Chávez, E. Campos-González, K. Rodríguez Rosales et F. de Moure-Flores. « Incorporation of colloidal Si nanoparticles into chemical bath solutions to synthesize nc-Si/CdS nanocomposite thin films ». Materials Chemistry and Physics 270 (septembre 2021) : 124845. http://dx.doi.org/10.1016/j.matchemphys.2021.124845.

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Dzhagan, V., O. Kapush, S. Budzulyak, N. Mazur, E. Gavryliuk, A. Litvinchuk, S. Kondratenko, V. Yukhymchuk et M. Valakh. « Colloidal Cu2ZnSnS4-based and Ag-doped Nanocrystals : Synthesis and Raman Spectroscopy Study ». Physics and Chemistry of Solid State 22, n^o 2 (8 mai 2021) : 260–68. http://dx.doi.org/10.15330/pcss.22.2.260-268.

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Cu2ZnSnS4 (CZTS) is one of the promising materials for absorber layers of new-generation thin film solar cells. Various synthetic routes of materials preparation and structural characterization have been explored so far. Further tuning of the CZTS properties is realized via partial substitution of the cations. Here we have used an affordable and scalable method of synthesizing colloidal CZTS nanocrystals (NC) in an aqueous solution. Variation of the synthesis parameters, in particular pH of the solution, was employed to improve the crystallinity of the NCs. Furthermore, CZTS NCs with partial substitution of Cu for Ag were also successfully synthesized. Raman spectroscopy was employed as a prime tool of structural characterization of the NCs obtained, along with optical absorption spectroscopy and ab initio DFT lattice dynamics calculations. An experimentally observed slight upward shift of the main phonon Raman peak upon increase of the Ag content in (AgxCu1-x)2ZnSnS4 NCs is in agreement with the trend predicted by DFT calculation. No pure Ag2ZnSnS4 NCs could be formed, indicating a critical role of Cu in forming the kesterite structure NCs under given synthesis conditions in an aqueous medium.

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Mikami, Kazuki, Yuta Kido, Yuji Akaishi, Armando Quitain et Tetsuya Kida. « Synthesis of Cu2O/CuO Nanocrystals and Their Application to H2S Sensing ». Sensors 19, n^o 1 (8 janvier 2019) : 211. http://dx.doi.org/10.3390/s19010211.

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Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu2O and CuO using a hot-soap method, and applied them to H2S sensing. Cu2O NCs were synthesized by simply heating a copper precursor in oleylamine in the presence of diol at 160 °C under an Ar flow. X-ray diffractometry (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) results indicated the formation of monodispersed Cu2O NCs having approximately 5 nm in crystallite size and 12 nm in colloidal size. The conversion of the Cu2O NCs to CuO NCs was undertaken by straightforward air oxidation at room temperature, as confirmed by XRD and UV-vis analyses. A thin film Cu2O NC sensor fabricated by spin coating showed responses to H2S in dilute concentrations (1–8 ppm) at 50–150 °C, but the stability was poor because of the formation of metallic Cu2S in a H2S atmosphere. We found that Pd loading improved the stability of the sensor response. The Pd-loaded Cu2O NC sensor exhibited reproducible responses to H2S at 200 °C. Based on the gas sensing mechanism, it is suggested that Pd loading facilitates the reaction of adsorbed oxygen with H2S and suppresses the irreversible formation of Cu2S.

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Toma, Maria, Oleksandr Selyshchev, Yevhenii Havryliuk, Aurel Pop et Dietrich R. T. Zahn. « Optical and Structural Characteristics of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution ». Photochem 2, n^o 3 (2 juillet 2022) : 515–27. http://dx.doi.org/10.3390/photochem2030036.

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ZnO nanocrystals doped with Nd, Gd, and Er were synthesized using a soft chemical process in ambient atmosphere. Pseudospherical and hexagonal nanocrystals (NC) of the wurtzite phase with a mean size of (7.4 ± 1.7) nm were obtained. The presence of rare earth (RE) dopants was confirmed by X-ray fluorescence (XRF) spectroscopy. The ZnO nanocrystals exhibited simultaneously narrow excitonic- and broad trap/surface-related photoluminescence (PL), both of which were affected by doping with RE atoms. Doping reduced the total PL intensity, suppressing the excitonic emission by a greater extent than the broad band PL. Also, doping resulted in a blue shift of the trap/surface-related emission, while the energy of the excitonic peak remained unchanged. Resonant Raman spectra additionally confirmed the wurtzite phase of ZnO NCs and revealed a shift of the A1-LO mode towards lower frequency upon doping that could be caused by the mass effect of RE atoms, point defects, and increases in charge carrier concentration. Fitting of the spectra with Voigt profiles showed better results with two surface optical (SO) phonon modes that were previously theoretically predicted for the wurtzite ZnO phase. The influence of RE doping on PL and Raman spectra can be explained by the incorporation of RE ions into the ZnO nanostructures, where the dopants act as non-radiative defects.

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SAEED, Sohail, et Rizwan HUSSAIN. « Deposition and characterization of Cu$_{9}$S$_{5}$ nanocrystals from unsymmetrical [(Hex)(Me)NC(S)NC(O)C$_{6}$H$_{3}$(NO$_{2})_{2}$-3,5]$_{2}$Cu(II) and [(Et)(Bu)NC(S)NC(O)C$_{6}$H$_{4}$-4-NO$_{2}$]$_{2}$Cu(II) complexes by colloidal thermolysis method ». TURKISH JOURNAL OF CHEMISTRY 38 (2014) : 413–22. http://dx.doi.org/10.3906/kim-1305-47.

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Stolyarchuk, I. D., R. Wojnarowska - Nowak, J. Polit, E. Sheregii, S. Nowak et M. Romerowicz - Misielak. « CdTe Quantum Dots and Their Bioconjugate with Human Serum Albumin for Fluorescence Imaging ». Фізика і хімія твердого тіла 18, n^o 2 (27 juin 2017) : 166–72. http://dx.doi.org/10.15330/pcss.18.2.166-172.

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The interaction between CdTe quantum dots (QDs) with human serum albumin (HSA) and human cell culture was studied by optical spectroscopy technique. Performed research explored the interaction between the CdTe QDs and HSA, and fluorescence imaging efficiency of the QD-HSA bioconjugates in comparison with colloidal QDs. The secondary structure of the HSA is similar to the native form, which suggests a biocompatibility of prepared bionanocomplex. The CdTe QD-HSA bionanoconjugate shows chemical stability in phosphate-buffered saline (PBS) under ambient conditions, furthermore, it is stable in the cytoplasm and suitable for cell labeling, tracking, and other bioimaging applications. The CdTe QDs located in an osteosarcoma cancer cells show a high luminescence intensity. The light emission of the CdTe QDs connected with albumin is less than the pure QDs, but it is still satisfactory, and additionally it is stable and has long photoluminescence lifetime. It suggests, that the CdTe NC-HSA bionanocomplex can be used as a fluorescent probe for cell labeling, tracking, and other bioimaging applications.

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Jiang, Xiaomei, Richard D. Schaller, Sergey B. Lee, Jeffrey M. Pietryga, Victor I. Klimov et Anvar A. Zakhidov. « PbSe nanocrystal/conducting polymer solar cells with an infrared response to 2 micron ». Journal of Materials Research 22, n^o 8 (août 2007) : 2204–10. http://dx.doi.org/10.1557/jmr.2007.0289.

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We investigated the photovoltaic response of nanocomposites made of colloidal, infrared-sensitive, PbSe nanocrystals (NCs) of various sizes and conjugated polymers of either regioregular poly (3-hexylthiophene) (RR-P3HT) or poly- (2-methoxy-5-(2-ethylhexoxy)-1,4-phenylene vinylene) (MEH-PPV). The conduction and valence energy levels of PbSe NCs were determined by cyclic voltammetry and revealed type II heterojunction alignment with respect to energy levels in RR-P3HT for smaller NC sizes. Devices composed of NCs and RR-P3HT show good diode characteristics and sizable photovoltaic response in a spectral range from the ultraviolet to the infrared. Using these materials, we have observed photovoltaic response at wavelengths as far to the infrared as 2 μm (0.6 eV), which is desirable due to potential benefits of carrier multiplication (or multi-exciton generation) from a single junction photovoltaic. Under reverse bias, the devices also exhibit good photodiode responses over the same spectral region.

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Havryliuk, Yevhenii, Volodymyr Dzhagan, Anatolii Karnaukhov, Oleksandr Selyshchev, Julia Hann et Dietrich R. T. Zahn. « Raman Spectroscopy and Thermoelectric Characterization of Composite Thin Films of Cu2ZnSnS4 Nanocrystals Embedded in a Conductive Polymer PEDOT:PSS ». Nanomaterials 13, n^o 1 (22 décembre 2022) : 41. http://dx.doi.org/10.3390/nano13010041.

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Cu2ZnSnS4 (CZTS) is an intensively studied potential solar cell absorber and a promising thermoelectric (TE) material. In the form of colloidal nanocrystals (NCs), it is very convenient to form thin films on various substrates. Here, we investigate composites of CZTS NCs with PEDOT:PSS, a widely used photovoltaics polymer. We focus on the investigation of the structural stability of both NCs and polymers in composite thin films with different NC-to-polymer ratios. We studied both pristine films and those subjected to flash lamp annealing (FLA) or laser irradiation with various power densities. Raman spectroscopy was used as the main characterization technique because the vibrational modes of CZTS NCs and the polymer can be acquired in one spectrum and thus allow the properties of both parts of the composite to be monitored simultaneously. We found that CZTS NCs and PEDOT:PSS mutually influence each other in the composite. The thermoelectric properties of PEDOT:PSS/CZTS composite films were found to be higher compared to the films consisting of bare materials, and they can be further improved by adding DMSO. However, the presence of NCs in the polymer deteriorates its structural stability when subjected to FLA or laser treatment.

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Busi, Kumar Babu, Subhalaxmi Das, Mathangi Palanivel, Krishna Kanta Ghosh, Balázs Gulyás, Parasuraman Padmanabhan et Sabyasachi Chakrabortty. « Surface Ligand Influences the Cu Nanoclusters as a Dual Sensing Optical Probe for Localized pH Environment and Fluoride Ion ». Nanomaterials 13, n^o 3 (28 janvier 2023) : 529. http://dx.doi.org/10.3390/nano13030529.

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Functional metal nanomaterials, especially in the nanocluster (NC) size regime, with strong fluorescence, aqueous colloidal stability, and low toxicity, necessitate their application potential in biology and environmental science. Here, we successfully report a simple cost-effective method for red-/green-color-emitting protein/amino-acid-mediated Cu NCs in an aqueous medium. As-synthesized Cu NCs were characterized through UV-Vis absorption spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence, dynamic light scattering, zeta potential, transmission electron microscopy and X-ray photoelectron spectroscopy. The optical properties of both Cu NCs responded linearly to the variation in pH in the neutral and alkaline ranges, and a robust pH reversible nature (between pH 7 and 11) was observed that could be extended to rapid, localized pH sensor development. However, a contrasting pH response nature between protein–Cu NCs and amino acid–Cu NCs was recorded. The alteration in protein secondary structure and strong binding nature of the surfactants were suggested to explain this behavior. Furthermore, we investigated their use as an efficient optical probe for fluoride ion detection. The limit of detection for protein–Cu NCs is 6.74 µM, whereas the limit of detection for amino acid–Cu NCs is 4.67 µM. Thus, it is anticipated that ultrasmall Cu NCs will exhibit promise in biological and environmental sensing applications.

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Choi, Mi, et Cheong-Soo Hwang. « Applications of the Water-Dispersible L-Cysteine-Capped ZnS:Mn Nanocrystals as a Selective Photosensor and an Efficient Photocatalyst ». Journal of Nanoscience and Nanotechnology 21, n^o 8 (1 août 2021) : 4484–91. http://dx.doi.org/10.1166/jnn.2021.19423.

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In this study, the ZnS:Mn nanocrystals (NCs) were prepared by capping the NC surface with a conventional amino acid, L-cysteine (Cys) molecules, at an acidic (pH 5) aqueous solution. The optical and physical characterizations of the ZnS:Mn-Cys-pH5 NCs were performed using various spectroscopic methods. For instance, the UV-visible and PL spectra of the ZnS:Mn-Cys-pH5 NCs showed broad peaks at 296 and 586 nm, respectively. The obtained HR-TEM image of the ZnS:Mn- Cys-pH5 NCs product showed spherical particle images with an average size of 6.15 nm in the solid state. In addition, measured surface charge of the colloidal ZnS:Mn-Cys-pH5 NCs using a zeta-PSA spectroscopy was −57.9 mV even at the acidic preparation condition. Therefore, the ZnS:Mn-Cys-pH5 NCs were applied as a photosensor to detect specific transition metal cations. As a result, the ZnS:Mn-Cys-pH5 NCs showed exclusive luminescence quenching effect for Fe(II) ions, which suggested that the ZnS:Mn-Cys-pH5 NCs can be applied as a photo-chemical sensor for Fe2+ ion detection in a practical water sample. The sensing ion selectivity of the ZnS:Mn-Cys-pH5 NCs was completely different comparing to ZnS:Mn NCs surface capped with other amino acids at the same condition. In addition, the catalytic activity of the ZnS:Mn-Cys-pH5 NCs was studied in the degradation reaction of an organic dye (methylene blue) molecule under UV light irradiation.

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Choi, Mi, et Cheong-Soo Hwang. « Differential Photosensor Activities for the L-Cysteine and L-Serine Capped ZnS:Mn Nanocrystals in the Detection of Divalent Transition Metal Ions in Aqueous Solution ». Journal of Nanoscience and Nanotechnology 20, n^o 11 (1 novembre 2020) : 6723–31. http://dx.doi.org/10.1166/jnn.2020.18799.

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Colloidal ZnS:Mn nanocrystals (NCs) were synthesized in water by capping the NC surface with conventional amino acids: L-cysteine (Cys) and L-serine (Ser) molecules, which have very similar structures but different terminal functional groups. The optical properties were investigated by using UV-Visible and photoluminescence (PL) spectroscopy. The PL spectra for both ZnS:Mn-Cys and ZnS:Mn-Ser NCs showed broad emission peaks at 590 nm. The measured average particle size from the high-resolution transmission electron microscopy (HR-TEM) images were 4.38 nm (ZnS:Mn-Cys) and 5.57 nm (ZnS:Mn-Ser), which were also supported by Debye-Scherrer calculations. In addition, the surface charge of the NCs in aqueous solutions were measured using zeta-particle size analyzer spectroscopy, which showed formation of negatively charged surface for the ZnS:Mn-Cys (−43.93 mV) and ZnS:Mn-Ser (−8.21 mV) NCs in water. In this present study those negatively charged NCs were applied as photosensors for the detection of specific divalent transition metal cations in aqueous solution at the same condition. Consequently, the ZnS:Mn-Cys and ZnS:Mn-Ser NCs showed totally different photosensor activities upon the addition of first-row divalent transition metal ions. The former NCs showed luminescence quenching for most added metal ions except for Zn (II) ions; whereas the latter NCs showed exclusive quenching effect for Cu (II) ions at the same conditions. These results suggested that those NCs can be applied as Zn2+ and Cu2+ ion sensors in water.

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Zeevi, Gilad, Joanna Dehnel, Adam K. Budniak, Yana Milyutin, Guy Ankonina, Hossam Haick, Efrat Lifshitz et Yuval E. Yaish. « Dynamics of light-induced charge transfer between carbon nanotube and CdSe/CdS core/shell nanocrystals ». Nano Futures 6, n^o 1 (20 janvier 2022) : 015001. http://dx.doi.org/10.1088/2399-1984/ac3ccc.

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Abstract The integration of semiconducting colloidal nanocrystals (NCs) with carbon nanotubes (CNTs) in a single device presents a unique platform that combines optical flexibility with high charge carrying capability. These qualities are desirable in many applications such as photovoltaic cells, photocatalysis, and light sensors. Here, we present hybrid devices that incorporate various CdSe/CdS core/shell NCs, such as seeded quantum dots and asymmetric seeded nanorods (a-sNRs), with a single-wall CNT in a field-effect transistor geometry. We used electrical measurements to probe a light-induced charge transfer (LICT) between the CdSe/CdS NCs and the CNT. We investigate the effect of gate voltage on the LICT magnitude and temporal characteristics. Surprisingly, the measured photo-response depends on the gate voltage, and we observe both electrons and holes transfer from the a-sNRs to the CNT. Furthermore, a comparison between LICT measurements on different devices with different CNTs and NC types reveals that the charge transfer time is directly proportional to the shell-thickness around the CdSe core and inversely correlated with the NCs size. The recovery of the charge trapped inside the CdSe/CdS NCs is characterized by two distinct fast and slow relaxation times, which depend on the NCs size and CNT type. Although, the charge relaxation time is similar between the symmetric QDs and the asymmetric sNRs, the overall percentage of the remaining charge in the QDs is significantly larger than in the sNRs. Understanding both gate voltage and NCs size effect on the LICT processes can optimize the performance of optoelectronic devices.

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Bastola, Ebin, Kamala Khanal Subedi, Khagendra P. Bhandari et Randy J. Ellingson. « Solution-processed Nanocrystal Based Thin Films as Hole Transport Materials in Cadmium Telluride Photovoltaics ». MRS Advances 3, n^o 41 (2018) : 2441–47. http://dx.doi.org/10.1557/adv.2018.349.

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ABSTRACTThe cadmium telluride (CdTe) photovoltaic (PV) comprise an efficient and cost-effective technology for harvesting solar energy. However, device efficiency remains limited in part by low-open circuit voltage (VOC) and fill factor (FF) due to inefficient transport of photo-generated charge carriers. Given the deep valence band of CdTe, the use of copper/gold (Cu/Au) as a back contact serves primarily to narrow the width of the inherent Schottky junction evident in CdTe solar cells (in our laboratory, Cu/Au has been used as a standard back contact). For efficient transport of carriers to and into the back contact, a hole transport layer (HTL) is desired with valence band edge comparable to that of CdTe (∼ -5.9 eV). Here, we report solution-processed nanocrystal (NCs) based thin films as HTLs in CdTe solar cells. The earth abundant materials we discuss include iron pyrite (FeS2), nickel-alloyed iron pyrite (NixFe1-xS2), zinc copper sulfide (ZnxCu1-xS) nanocomposites, and perovskite-based films. The FeS2 and NixFe1-xS2 NCs are synthesized by a hot-injection route, and thin films are fabricated by drop-casting, and spin-coating techniques using colloidal NCs. ZnxCu1-xS thin films are fabricated by chemical bath deposition. These NC-based thin films are applied and studied as the HTLs in CdTe devices. On using these materials, the device performance can be increased up to 10% compared to the standard Cu/Au back contact. Here, we discuss the benefits, challenges, and opportunities for these back contact materials in CdTe photovoltaics.

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