Journal articles: 'Nanocrystals - Luminescence'

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Mukhina, Maria V., Vladimir G. Maslov, Ivan V. Korsakov, Finn Purcell Milton, Alexander Loudon, Alexander V. Baranov, Anatoly V. Fedorov, and Yurii K. Gun’ko. "Optically active II-VI semiconductor nanocrystals via chiral phase transfer." MRS Proceedings 1793 (2015): 27–33. http://dx.doi.org/10.1557/opl.2015.652.

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ABSTRACTWe report optically active ensembles of II-VI semiconductor nanocrystals prepared via chiral phase transfer, which is initiated by exchange of the original achiral ligands capping the nanocrystals surfaces for chiral L- and D-cysteine. We used this method to obtain ensembles of CdSe, CdS, ZnS:Mn, and CdSe/ZnS quantum dots and CdSe/CdS quantum rods exhibited Circular Dichroism (CD) and Circularly Polarized Luminescence (CPL) signals. The optically active nanocrystals revealed the CD and CPL bands strongly correlated with absorption and luminescence bands with unique band “pattern” for each material and the nanocrystal shape.

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Korbutyak, D. V. "SURFACE LUMINESCENCE OF A2B6 SEMICONDUCTOR QUANTUM DOTS (REVIEW)." Optoelektronìka ta napìvprovìdnikova tehnìka 56 (December 7, 2021): 27–38. http://dx.doi.org/10.15407/iopt.2021.56.027.

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Semiconductor zero-dimensional nanocrystals – quantum dots (QDs) – have been increasingly used in various fields of opto- and nanoelectronics in recent decades. This is because of the exciton nature of their luminescence, which can be controlled via the well known quantum-dimensional effect. At the same time, at small nanocrystall sizes, the influence of the surface on the optical and structural properties of nanocrystals increases significantly. The presence of broken bonds of surface atoms and point defects – vacancies and interstial atoms – can both weaken the exciton luminescence and create new effective channels of radiant luminescence. In some cases, these surface luminescence becomes dominant, leading to optical spectra broadening up to the quasi-white light. The nature of such localized states often remains unestablished due to the large number of the possible sorts of defects in both of QD and its surrounding. In contrast to exciton luminescence, which can be properly described within effective-mass approximations, the optical properties of defects relay on chemical nature of both defect itsself and its surrounding, what cannot be provided by “hydrogen-type coulomb defect” approximation. Moreover, charge state and related to this lattice relaxation must be taken into account, what requires an application of atomistic approach, such as Density functioal theory (DFT). Therefore, this review is devoted to the study of surface (defect) states and related luminescence, as well as the analysis of possible defects in nanocrystals of semiconductor compounds A2B6 (CdS, CdZnS, ZnS), responsible for luminescence processes, within ab initio approach. The review presents the results of the authors' and literature sources devoted to the study of the luminescent characteristics of ultra-small (<2 nm) QDs.

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Cui, Fang, Tong Jie Yao, Jing Yu, and Ke Ning Sun. "Synthesis and Characterization of Luminescent TiO₂/Polymer Nanocomposites." Advanced Materials Research 873 (December 2013): 492–95. http://dx.doi.org/10.4028/www.scientific.net/amr.873.492.

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Transparent luminescent TiO2/polymer nanocomposites were obtained through the combined use of copolymerization of a novel titanium ion containing monomer with a liquidsolid reaction. The titanium ions are covalently introduced into polymer chains and transformed into TiO2 nanocrystals directly in the solid-state polymer matrices. That allows the generation of high-quality anatase TiO2 nanocrystals with a narrow size distribution in the polymer matrices. The luminescence of the TiO2 nanocrystals is dominated by band-edge luminescence at room temperature.

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Valiev, Damir, Rufina Kharisova, Anastasiia Babkina, Ksenia Zyryanova, Natalia Kuzmenko, Yevgeniy Sgibnev, Artem Shelaev, and Alexander V. Baryshev. "Highly Luminescent Rb-Doped Cs4PbBr6 Nanocrystals in Borogermanate Glass." Photonics 10, no. 7 (June 26, 2023): 729. http://dx.doi.org/10.3390/photonics10070729.

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For the first time, the synthesis, luminescent and structural properties of stable perovskite-type (Cs1−xRbx)4PbBr6 (R = Cs, Rb) nanocrystals are shown. In the absence of rubidium, Cs4PbBr6 and CsPbBr3 perovskite crystals precipitate in the ZnO–Na2O–B2O3–GeO2 glass matrix. With ascending rubidium content, the precipitation of (Cs,Rb)4PbBr6 nanocrystals is replaced by the Rb4PbBr6 nanocrystals nucleation. Nucleated nanocrystals exhibit an intense green luminescence. With an increase of the rubidium content, the luminescence maximum shifts to the blue region, the luminescence quantum yield increases from 28 to 51%, and the average decay time increases from 2 to 8 ns. Several assumptions have been made about the nature of the green luminescence of perovskite-like Cs4PbBr6 and (Cs,Rb)4PbBr6 crystals in glasses. It is concluded that the most probable cause is the impurity inclusions of CsPbBr3 and (Cs,Rb)PbBr3 crystals.

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Shvalagin, Vitaliy, Galyna Grodziuk, Olha Sarapulova, Misha Kurmach, Vasyl Granchak, and Valentyn Sherstiuk. "Influence of Nanosized Silicon Oxide on the Luminescent Properties of ZnO Nanoparticles." Journal of Nanotechnology 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/2708638.

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For practical use of nanosized zinc oxide as the phosphor its luminescence quantum yields should be maximized. The aim of this work was to enhance luminescent properties of ZnO nanoparticles and obtain high-luminescent ZnO/SiO2composites using simpler approaches to colloidal synthesis. The luminescence intensity of zinc oxide nanoparticles was increased about 3 times by addition of silica nanocrystals to the source solutions during the synthesis of ZnO nanoparticles. Then the quantum yield of luminescence of the obtained ZnO/SiO2composites is more than 30%. Such an impact of silica is suggested to be caused by the distribution of ZnO nanocrystals on the surface of silica, which reduces the probability of separation of photogenerated charges between the zinc oxide nanoparticles of different sizes, and as a consequence, there is a significant increase of the luminescence intensity of ZnO nanoparticles. This way of increasing nano-ZnO luminescence intensity facilitates its use in a variety of devices, including optical ultraviolet and visible screens, luminescent markers, antibacterial coatings, luminescent solar concentrators, luminescent inks for security printing, and food packaging with abilities of informing consumers about the quality and safety of the packaged product.

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Wang, Shanshan, Zhangkun Liu, Yuxiu Zou, Xiaofang Lai, Ding Ding, Long Chen, Liqin Zhang, Yuan Wu, Zhuo Chen, and Weihong Tan. "Elucidating the cellular uptake mechanism of aptamer-functionalized graphene-isolated-Au-nanocrystals with dual-modal imaging." Analyst 141, no. 11 (2016): 3337–42. http://dx.doi.org/10.1039/c6an00483k.

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Bendre, B. S., and Shailaja Mahamuni. "Luminescence in ZnO Quantum Particles." Journal of Materials Research 19, no. 3 (March 2004): 737–40. http://dx.doi.org/10.1557/jmr.2004.19.3.737.

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Wet-chemical and electrochemical routes were used to synthesize zinc oxide nanoparticles showing peculiar luminescent properties. ZnO-I are the nanoparticles that show only band gap ultraviolet (UV) emission, whereas ZnO-II type nanoparticles show the defect green luminescence along with the UV emission. Photoluminescence excitation (PLE) spectra of ZnO-I nanocrystals exhibit a single feature located at about 368 nm whereas ZnO-II nanocrystals show two features in PLE: a prominent feature at about 368 nm which is size dependent and a hump at 325 nm. These results are discussed in detail in view of the luminescence behavior in ZnO quantum particles.

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Pan, Er, Gongxun Bai, Yutao Peng, Liang Chen, and Shiqing Xu. "Promoting luminescence of Yb/Er codoped ferroelectric composite by polarization engineering for optoelectronic applications." Nanophotonics 8, no. 12 (September 17, 2019): 2215–23. http://dx.doi.org/10.1515/nanoph-2019-0230.

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AbstractFerroelectric oxide nanocrystals, in combination with the robust coupling of an electric field with crystal structure symmetry, makes such systems agreeable to field-induced crystal structural transformation. The luminescent properties of rare earth ions are sensitive to the symmetry of the surrounding crystal field. The luminescence tuning of rare earth ions is an important assignment in the research of luminescent materials. However, the current conditional feasibility and reversibility in the exploration of luminescence modification remain major challenges. In this article, the luminescence modulation of rare earth ions has been developed in Yb3+/Er3+ codoped ferroelectrics glass ceramics containing Bi4Ti3O12 nanocrystals through an electric field. The inclusion of nanocrystals in the glass matrix greatly enhances the electrical resistance. Both upconversion and near-infrared emissions of rare earth ions are effectively enhanced more than twice via polarization engineering. The electric field regulates the photonic properties of rare earth ions with excellent reversibility and nonvolatility in ferroelectrics. The effective modification by electric field provides a new scheme for optical storage and optoelectronic devices.

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LI, JUN, KUI ZHAO, RUOKUN JIA, YANMEI LIU, YUBAI BAI, and TIEJIN LI. "USING EMISSION QUENCHING TO STUDY THE INTERACTION BETWEEN ZnO NANOCRYSTALS AND ORGANIC LIGANDS." International Journal of Nanoscience 01, no. 05n06 (October 2002): 743–47. http://dx.doi.org/10.1142/s0219581x02000991.

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Colloidal ZnO nanocrystals with strong green luminescence were prepared. When ZnO nanocrystals were modified with different organic ligands, the emission quenching was measured and used to study the interaction between ZnO nanocrystal and organic ligands. Efficiency of emission quenching relates to the chemical structures of the ligands, and metal-thiolate bond was formed between nanocrystals and thiol ligands. The relative strength of the binding and the surface concentration of the adsorbed species could be determined using this method.

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Kataoka, Takuya, Shigeaki Abe, and Motohiro Tagaya. "Synthesis of Europium(III) Complex-Based Hydroxyapatite Nanocrystals for Biolabeling Applications." Key Engineering Materials 782 (October 2018): 41–46. http://dx.doi.org/10.4028/www.scientific.net/kem.782.41.

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We synthesized the inorganic/organic hybrid nanocrystal (EHA) by hydroxyapatite (HA) nanocrystal growth under the existence of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (EuTH) complex. Then, folic acid derivative (FA-NHS: folate N-hydroxysuccinimidyl ester) as the targeting ligand for the HeLa cancer cells was immobilized on the EHA by the mediation of 3-aminopropyltriethoxysilane (APTES) and methyltriethoxysilane (MTES). When the FA-NHS molecular occupancy ratio on the EHA surface is around 3 to 5 %, the strong luminescence from the f-f transition of the Eu3+ ion and luminescence associated with energy transfer between the EuTH-FA monomer near 518 nm were observed. Moreover, the dispersibility in phosphate buffer saline was confirmed with immobilizing the positively-charged FA-NHS. The affinity and non-cytotoxicity between the nanocrystals and HeLa cancer cells were confirmed for 3 days. The red luminescence from the cells could be observed by fluorescence microscopy and the luminescence spectra.

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Meng, Yong-Jun, Hong Li, Jian-Wei Tang, and Xue-Wen Chen. "Modulation of upconversion luminescence spectrum of single rare-earth-doped upconversion nanocrystal based on plasmonic nanocavity." Acta Physica Sinica 71, no. 2 (2022): 027801. http://dx.doi.org/10.7498/aps.71.20211438.

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Plasmonic nanocavities can effectively modulate the upconversion luminescence properties of lanthanide doped upconversion nanocrystals (UCNCs), which not only enhances the luminescence intensity, but also modifies the luminescence spectrum. However, currently reported studies of upconversion luminescence spectrum modulation by using nanocavities are mainly based on ensemble experiments. Compared with ensemble experiments, single-particle experiments facilitate the comparative studies for the same upconversion nanocrystal and therefore the influence of inhomogeneity in ensemble samples can be avoided. Here in this work, we couple a single particle of Yb<sup>3+</sup>/Tm<sup>3+</sup> co-doped nanocrystal with a plasmonic nanocavity composed of a single gold nanorod by using the in-situ nano-manipulation technique based on an atomic force microscope. Experimentally, we compare the upconversion luminescence spectra, upconversion luminescence lifetimes and excitation-power dependent upconversion luminescence intensities of the same single nanocrystal before and after coupling with the single gold nanorod. The experimental measurements are consistent with the theoretical calculations from rate equations combined with electromagnetic simulations. The results indicate that the plasmaonic nanocavity modulated nanocrystal upconversion luminescence spectrum is the combined result of three effects: the excitation field enhancement effect, the Purcell effect and the change of radiation efficiency.

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Knowles, Kathryn E., Troy B. Kilburn, Dane G. Alzate, Stephen McDowall, and Daniel R. Gamelin. "Bright CuInS2/CdS nanocrystal phosphors for high-gain full-spectrum luminescent solar concentrators." Chemical Communications 51, no. 44 (2015): 9129–32. http://dx.doi.org/10.1039/c5cc02007g.

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Experimental and computational analyses demonstrate that CuInS₂/CdS nanocrystals with large solar absorption, high quantum yields, and only moderate luminescence reabsorption excel as phosphors for full-spectrum luminescent solar concentrators.

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Уролов, Ш. З., Р. Р. Жалолов, З. Ш. Шаймарданов, М. А. Маматкосимов, А. Абдурахманов, and С. С. Курбанов. "Влияние термической обработки и солнечной радиации на оптические характеристики наноструктур оксида цинка." Журнал технической физики 127, no. 12 (2019): 999. http://dx.doi.org/10.21883/os.2019.12.48699.139-19.

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Emission properties of ZnO nanorods and nanocrystals after high-temperature annealing in air and irradiation with high-intensity solar radiation have been studied. As-synthesized nanorods and nanocrystals under UV radiation exhibit a luminescence with maxima at around 380-384 and 560-570 nm. In both nanostructures, after heat treatment and irradiation with high-intensity solar radiation, an increase in the intensities of the short-wavelength luminescence bands is observed. In addition, after heat treatment and irradiation, in nanorods the long-wavelength luminescence band vanishes, while a new band at 520 nm appears in the luminescence spectrum of the nanocrystals. Irradiation with solar radiation has a greater effect on the emission properties of nanorods than nanocrystals and it is possible, caused by predominantly radiation heating (annealing) of nanorods than nanocrystals.

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Pankratov, V., Larisa Grigorjeva, Donats Millers, Tadeusz Chudoba, Robert Fedyk, and Witold Łojkowski. "Time-Resolved Luminescence Characteristics of Cerium Doped YAG Nanocrystals." Solid State Phenomena 128 (October 2007): 173–78. http://dx.doi.org/10.4028/www.scientific.net/ssp.128.173.

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Time-resolved luminescence characteristics have been studied for cerium doped YAG nanopowders (NP) and nanostructured ceramics (NC). The results obtained have been compared to the luminescence characteristics for the well studied YAG:Ce3+ single crystal (SC). It was detected that the luminescence decay kinetics of Ce3+ related emission in nanocrystals can be closely approximated by two exponents, whereas a single exponential decay was observed in the single crystal. It was also found that the luminescence decay time and light yield of Ce3+ emission are strongly dependent on the cerium concentration and an unusual concentration quenching of Ce3+ emission was observed in YAG nanocrystals. The origin of the differences of luminescence characteristics for cerium doped nanocrystals and SC are discussed. It is suggested that there are special Ce3+ sites which are closely related to the surface states and that they have a strong influence on the luminescence properties of cerium doped YAG nanocrystals.

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Muh’d, Ibrahim Bagudo, Zainal A. Talib, Zulkarnain Zainal, and Josephine Ying Chi Liew. "Pinned Luminescence Emission and Absorbance Band from Ultrasmall Ball-Milled Cd0.3Zn0.7Se Nanocrystals." Journal of Nanomaterials 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/2083819.

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We report the pinned absorbance and emission spectra of Cd0.3Zn0.7Se nanocrystals synthesized via mechanical alloying. The first emission peaks of Cd0.3Zn0.7Se nanocrystals milled for 5 and 10 h are observed at 3.36 eV, while the absorbance spectra of those milled for 10 and 20 h are observed at 4.47 eV. The emission peaks of nanocrystals milled for 5, 10, and 20 h have broad emissions centered at 2.90, 2.88, and 2.92 eV, respectively. Transmission electron microscopy histogram shows that each nanocrystal size distribution has a single population maxima of <2 nm. In addition, the center of each size distribution shifts toward the ultrasmall particles upon continuous milling. Particle sizes (d) of 0.73 nm are calculated from the first excitonic peaks of the pinned absorbance bands through the semiempirical sizing equation. The continuous reduction in particle sizes increases the surface-to-volume ratios of the nanocrystals. This increase eventually results in an increase in the surface states that translate into low photoluminescence intensity of pinned emission.

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Zi, Lu, Dan Zhang, and Gejihu De. "Facile Synthesis of Yb3+- and Er3+-Codoped LiGdF4 Colloidal Nanocrystals with High-Quality Upconversion Luminescence." Journal of Nanomaterials 2019 (May 16, 2019): 1–9. http://dx.doi.org/10.1155/2019/3928526.

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Herein, we synthesized high-quality colloidal nanocrystals of Yb3+/Er3+-codoped LiGdF4 with intense green emission by using a facile route and turning the associated reaction parameters. Moreover, we probed the effects of reaction conditions on nanocrystal properties (crystal structure, morphology, and luminescence) and gained valuable mechanistic insights into nucleation and growth processes. Sample purity was found to depend on LiOH·H2O concentration, reaction temperature, and time, which allowed us to manipulate sample purity and thus obtain species ranging from mixtures of LiGdF4:Yb3+/Er3+ with GdF3 to pure tetragonal-phase LiGdF4:Yb3+/Er3+. Investigation of upconversion luminescence properties and the luminescence lifetime of as-prepared samples revealed that LiGdF4 is a promising host material for realizing the desired upconversion luminescence.

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Secu, Corina, Cristina Bartha, Elena Matei, Cristian Radu, and Mihail Secu. "Structural and Optical Characterization of Silica Nanospheres Embedded with Monodisperse CeO2-Eu3+ Nanocrystals." Magnetochemistry 8, no. 2 (February 4, 2022): 22. http://dx.doi.org/10.3390/magnetochemistry8020022.

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Luminescent nanocrystals embedded into silica microspheres were shown to be useful for silica labeling for biological applications, ensuring mechanical and chemical stability, nontoxicity, biocompatibility and optical properties. We used sol–gel technology to prepare silica nanospheres embedded with fluorescent and magnetic Eu3+(1 mol%)-doped CeO2 nanocrystals. The X-ray diffraction pattern analysis and transmission electron microscopy investigations showed CeO2:Eu3+(1 mol%) nanocrystals of about 9 nm size and Ce3+ ions substitution by the Eu3+ ions; the nanocrystals dispersed inside the nanosized silica spheres of about 400 nm diameters. The photoluminescence spectra recorded under UV-light excitation showed Eu3+ ions luminescence peaks (5D0-7FJ, J = 0–4) accompanied by a weaker 425 nm luminescence due to the silica matrix; the quantum yield was 0.14. The weak hysteresis loop and magnetization curves recorded up to 20,000 Oe showed dominantly paramagnetic behavior associated with the silica matrix; a slight opening of the hysteresis loop to a very small magnetic field (about 0.005 Oe) was due to the presence of the two rare earth ions. The photonic crystal properties of SiO2-CeO2:Eu3+(1 mol%) silica nanospheres deposited as films on quartz plates were revealed by the two weak attenuation peaks at 420 and 500 nm and were associated with the reflection from different planes. The SiO2-CeO2:Eu3+(1 mol%) nanospheres are attractive potential candidates for photonics-related applications or for multifunctional bio-labels by combining the luminescence and magnetic properties of the nanocrystals.

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Ferraioli, L., M. Wang, G. Pucker, D. Navarro-Urrios, N. Daldosso, C. Kompocholis, and L. Pavesi. "Photoluminescence of Silicon Nanocrystals in Silicon Oxide." Journal of Nanomaterials 2007 (2007): 1–5. http://dx.doi.org/10.1155/2007/43491.

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Recent results on the photoluminescence properties of silicon nanocrystals embedded in silicon oxide are reviewed and discussed. The attention is focused on Si nanocrystals produced by high-temperature annealing of silicon rich oxide layers deposited by plasma-enhanced chemical vapor deposition. The influence of deposition parameters and layer thickness is analyzed in detail. The nanocrystal size can be roughly controlled by means of Si content and annealing temperature and time. Unfortunately, a technique for independently fine tuning the emission efficiency and the size is still lacking; thus, only middle size nanocrystals have high emission efficiency. Interestingly, the layer thickness affects the nucleation and growth kinetics so changing the luminescence efficiency.

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Wuister, Sander F., Floris van Driel, and Andries Meijerink. "Luminescence of CdTe nanocrystals." Journal of Luminescence 102-103 (May 2003): 327–32. http://dx.doi.org/10.1016/s0022-2313(02)00520-3.

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Carl, Frederike, Leonie Birk, Bettina Grauel, Monica Pons, Christian Würth, Ute Resch-Genger, and Markus Haase. "LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals." Nano Research 14, no. 3 (October 16, 2020): 797–806. http://dx.doi.org/10.1007/s12274-020-3116-y.

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AbstractWe developed a procedure to prepare luminescent LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF4:Yb (Yb:YLF) and LiYF4:Yb,Er (Yb,Er:YLF) with identical doping concentrations. As the luminescence decay times of Yb3+ and Er3+ are known to be very sensitive to the presence of quenchers, the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell interfaces. This improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based synthesis. First, the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF4 shell material. Second, anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH− in the crystal lattice, known to quench the emission of Yb3+ ions. Excitation power density (P)-dependent absolute measurements of the upconversion luminescence quantum yield (ΦUC) of LiYF4:Yb,Er/LiYF4 core/shell particles reveal a maximum value of 1.25% at P of 180 Wcm−2. Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes, these ΦUC values are the highest reported so far for LiYF4:18%Yb,2%Er/LiYF4 nanocrystals without additional dopants. Further improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF4 nanocrystals.

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Deng, Yuan, Yicheng Zeng, Wanying Gu, Pan Huang, Geyu Jin, Fangze Liu, Jing Wei, and Hongbo Li. "Colloidal Synthesis and Ultraviolet Luminescence of Rb2AgI3 Nanocrystals." Crystals 13, no. 7 (July 16, 2023): 1110. http://dx.doi.org/10.3390/cryst13071110.

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Semiconductor nanocrystals (NCs) hold immense potential as luminescent materials for various optoelectronic applications. While significant progress has been made in developing NCs with outstanding optical properties in the visible range, their counterparts emitting in the ultraviolet (UV) spectrum are less developed. Rb2AgI3 is a promising UV-emitting material due to its large band gap and high stability. However, the optical properties of low-dimensional Rb2AgI3 NCs are yet to be thoroughly explored. Here, we synthesized Rb2AgI3 NCs via a hot injection method and investigated their properties. Remarkably, these NCs exhibit UV luminescence at 302 nm owing to self-trapped excitons. The wide-bandgap nature of Rb2AgI3 NCs, combined with their intrinsic UV luminescence, offers considerable potential for applications in UV photonic nanodevices. Our findings contribute to the understanding of Rb2AgI3 NCs and pave the way for exploiting their unique properties in advanced optoelectronic systems.

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Nitsuk, Yu A., O. V. Karaush, Ya I. Lepikh, Yu F. Vaksman, and G. V. Korenkova. "LUMINESCENCE OF COLLOIDAL CdSe:Cu NANOCRYSTALS." Sensor Electronics and Microsystem Technologies 19, no. 4 (January 23, 2023): 23–29. http://dx.doi.org/10.18524/1815-7459.2022.4.271202.

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The luminescence of Colloidal CdSe:Cu nanocrystals was studied. It is shown that copper doping does not lead to a noticeable change in the size of nanocrystallites. The change in the band gap width can be explained by the inter- impurity Coulomb interaction. It is shown that copper doping leads to quenching of exciton luminescence of CdSe. It is established that the long-wave luminescence of CdSe:Cu is caused by transitions within the donor- acceptor pairs, which include intrinsic and impurity Cu defects.

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CHAN, M. Y., and P. S. LEE. "FABRICATION OF SILICON NANOCRYSTALS AND ITS ROOM TEMPERATURE LUMINESCENCE EFFECTS." International Journal of Nanoscience 05, no. 04n05 (August 2006): 565–70. http://dx.doi.org/10.1142/s0219581x06004802.

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Silicon ( Si ) nanocrystals have been considered a good candidate for flash memory device and nanophotonic applications. The fabrication of nanocrystal memory is to form uniform, small size and high density quantum dots. In this study, nanometer-scale silicon quantum dots have been fabricated on ultrathin silicon oxide layer using amorphous silicon (a- Si ) deposition followed by various annealing treatments. The a- Si layers were crystallized using furnace annealing, laser annealing and rapid thermal annealing (RTA). After annealing to form nanometer-sized crystallites, silicon wet etch was carried out to isolate the nanocrystals. The size, uniformity and density of the nanocrystals were successfully controlled by different annealing treatments. The mean dot height and mean dot diameter is 1–5 nm and 2–5 nm, respectively. Lateral growth of the silicon dots was further controlled by systemic variations of the annealing conditions. It is found that the annealed a- Si films exhibit room temperature visible photoluminescence (PL) resulting from the formation of nanometer-sized crystallites. Selective wet etch and Secco-etch treatment increased the PL efficiency that is useful for nanophotonics applications. The feasibility of quantum dot formation using ultra thin amorphous Si films is demonstrated in this work.

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Ницук, Ю. А., М. И. Киосе, Ю. Ф. Ваксман, В. А. Смынтына, and И. Р. Яцунский. "Оптические свойства нанокристаллов CdS, легированных цинком и медью." Физика и техника полупроводников 53, no. 3 (2019): 381. http://dx.doi.org/10.21883/ftp.2019.03.47291.8982.

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AbstractCadmium-sulfide nanocrystals are produced by the colloidal method. Doping with zinc and copper is conducted during nanocrystal growth. The optical absorption and photoluminescence spectra are studied. The maximum concentration of the optically active copper impurity is determined from a shift of the fundamental absorption edge to lower energies. It is shown that the long-wavelength luminescence of CdS and CdS:Zn nanocrystals is defined by optical transitions at donor–acceptor pairs. In CdS:Cu nanocrystals, optical absorption and photoluminescence in the visible spectral region are defined by recombination transitions involving the ground state of $${\text{Cu}}_{{{\text{Zn}}}}^{{2 + }}$$ ions. The infrared absorption and photoluminescence of CdS:Cu quantum dots are defined by intracenter transitions within $${\text{Cu}}_{{{\text{Zn}}}}^{{2 + }}$$ ions.

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Seminko, Vladyslav, Pavel Maksimchuk, Iryna Bespalova, and Yuri Malyukin. "Different Roles of Ce3+ Optical Centers in Oxyorthosilicate Nanocrystals at X-ray and UV Excitation." Crystals 9, no. 2 (February 21, 2019): 114. http://dx.doi.org/10.3390/cryst9020114.

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Luminescence properties of Lu2SiO5:Ce3+ and Y2SiO5:Ce3+ nanocrystals were studied using photo- and X-ray luminescence techniques. The crystal structure of Re2SiO5 nanocrystals (P21/c space group) differs from the crystal structure of Re2SiO5 bulk crystals (C2/c space group) with 9- and 7-oxygen-coordinated cation positions instead of 6- and 7-coordinated ones observed for Re2SiO5 bulk crystals. Two optical centers (Ce1 and Ce2) were observed for Re2SiO5:Ce3+ nanocrystals originating from cerium ions substituting 9- and 7-oxygen-coordinated cation sites. Preferential substitution of larger cation sites by cerium ions leads to higher photoluminescence intensity of Ce1 centers, however, Ce2 centers are the main centers for electron-hole recombination, so only Ce2 band is observed in X-ray luminescence spectra. The features of oxygen coordination of Ce1 and Ce2 centers and high content of oxygen vacancies in Re2SiO5:Ce3+ nanocrystals can provide preferential trapping of electrons near Ce2 centers, and therefore, the dominant role of Ce2 band in X-ray luminescence spectra.

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Sharma, Kanupriya, Praveen Kumar, and Gaurav Verma. "Effect of nanocrystals concentration on optical and luminescent properties of PVK:ZnSe nanocomposites." Materials Science-Poland 36, no. 3 (September 1, 2018): 494–500. http://dx.doi.org/10.2478/msp-2018-0063.

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AbstractThis work presents a systematic study of the effect of ZnSe nanocrystals (NCs) concentration on the optical and luminescent properties of poly N-vinylcarbazole (PVK) polymer nanocomposites. The ZnSe nanocrystals were synthesized by a simple coprecipitation chemical route, while PVK:ZnSe nanocomposite films were fabricated using the spin coating technique. The samples were characterized by XRD, TEM, SEM, UV-Vis and fluorescence techniques. The X-ray diffraction and TEM studies confirmed the particle size, microstructure and spherical shape of the synthesized nanocrystals. The ZnSe nanocrystals in PVK caused a decrease in optical gap with increasing concentration of nanocrystals. The emission spectra exhibited augmentation in intensity up to 70 wt.% of nanoparticles while further addition resulted in a decrease in luminescence. The structure-property relationships obtained for the present system are important for developing low cost illumination devices.

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Lu, Kailei, Yingxin Yi, Li Xu, Xianhao Sun, Lu Liu, and Hanyang Li. "Temperature-Independent Lifetime and Thermometer Operated in a Biological Window of Upconverting NaErF4 Nanocrystals." Nanomaterials 10, no. 1 (December 20, 2019): 24. http://dx.doi.org/10.3390/nano10010024.

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Lifetime of lanthanide luminescence basically decreases with increasing the ambient temperature. In this work, we developed NaErF4 core–shell nanocrystals with compensation of the lifetime variation with temperature. Upconversion lifetime of various emissions remains substantially unchanged as increasing the ambient temperature, upon 980/1530 nm excitation. The concentrated dopants, leading to extremely strong interactions between them, are responsible for the unique temperature-independent lifetime. Besides, upconversion mechanisms of NaErF4 core-only and core–shell nanocrystals under 980 and 1530 nm excitations were comparatively investigated. On the basis of luminescent ratiometric method, we demonstrated the optical thermometry using non-thermally coupled 4F9/2 and 4I9/2 emissions upon 1530 nm excitation, favoring the temperature monitoring in vivo due to both excitation and emissions fall in the biological window. The formed NaErF4 core–shell nanocrystals with ultra-small particle size, highly efficient upconversion luminescence, unique temperature-independent lifetimes, and thermometry operated in a biological window, are versatile in applications such as anti-counterfeiting, time-domain manipulation, and biological thermal probes.

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Millers, Donats, Larisa Grigorjeva, Witold Łojkowski, and A. Opalińska. "Luminescence of ZrO₂ Nanocrystals." Solid State Phenomena 106 (September 2005): 103–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.106.103.

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The luminescence of nanocrystalline tetragonal and cubic ZrO2 has been investigated. The tetragonal undoped ZrO2 revealed two luminescence bands, at ~2.0 eV and 2.7 eV , but only one band at ~2.7 eV was observed from cubic ZrO2. This luminescence was shown to be intrinsic. The regular zirconium-oxygen complex excited state is suggested as being responsible for intrinsic luminescence.

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Xu, Lili, Man Wang, Qing Chen, Jiajia Yang, Wubin Zheng, Guanglei Lv, Zewei Quan, and Chunxia Li. "Rare Earth Hydroxide as a Precursor for Controlled Fabrication of Uniform β-NaYF4 Nanoparticles: A Novel, Low Cost, and Facile Method." Molecules 24, no. 2 (January 19, 2019): 357. http://dx.doi.org/10.3390/molecules24020357.

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In recent years, rare earth doped upconversion nanocrystals have been widely used in different fields owing to their unique merits. Although rare earth chlorides and trifluoroacetates are commonly used precursors for the synthesis of nanocrystals, they have certain disadvantages. For example, rare earth chlorides are expensive and rare earth trifluoroacetates produce toxic gases during the reaction. To overcome these drawbacks, we use the less expensive rare earth hydroxide as a precursor to synthesize β-NaYF4 nanoparticles with multiform shapes and sizes. Small-sized nanocrystals (15 nm) can be obtained by precisely controlling the synthesis conditions. Compared with the previous methods, the current method is more facile and has lower cost. In addition, the defects of the nanocrystal surface are reduced through constructing core–shell structures, resulting in enhanced upconversion luminescence intensity.

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Sekar, Sankar, and Sejoon Lee. "Derivation of Luminescent Mesoporous Silicon Nanocrystals from Biomass Rice Husks by Facile Magnesiothermic Reduction." Nanomaterials 11, no. 3 (March 1, 2021): 613. http://dx.doi.org/10.3390/nano11030613.

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High-quality silicon (Si) nanocrystals that simultaneously had superior mesoporous and luminescent characteristics were derived from sticky, red, and brown rice husks via the facile and cost-effective magnesiothermic reduction method. The Si nanocrystals were confirmed to comprise an aggregated morphology with spherical nanocrystals (e.g., average sizes of 15–50 nm). Due to the surface functional groups formed at the nanocrystalline Si surfaces, the Si nanocrystals clearly exhibited multiple luminescence peaks in visible-wavelength regions (i.e., blue, green, and yellow light). Among the synthesized Si nanocrystals, additionally, the brown rice husk (BRH)-derived Si nanocrystals showed to have a strong UV absorption and a high porosity (i.e., large specific surface area: 265.6 m2/g, small average pore diameter: 1.91 nm, and large total pore volume: 0.5389 cm3/g). These are indicative of the excellent optical and textural characteristics of the BRH-derived Si nanocrystals, compared to previously reported biomass-derived Si nanocrystals. The results suggest that the biomass BRH-derived Si nanocrystals hold great potential as an active source material for optoelectronic devices as well as a highly efficient catalyst or photocatalyst for energy conversion devices.

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Nirmal, Manoj, and Louis Brus. "Luminescence Photophysics in Semiconductor Nanocrystals." Accounts of Chemical Research 32, no. 5 (May 1999): 407–14. http://dx.doi.org/10.1021/ar9700320.

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32

Wang, Guofeng, Qing Peng, and Yadong Li. "Luminescence Tuning of Upconversion Nanocrystals." Chemistry - A European Journal 16, no. 16 (March 22, 2010): 4923–31. http://dx.doi.org/10.1002/chem.200903099.

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33

Grigorjeva, Larisa, Donats Millers, Witold Łojkowski, and Tomas Strachowski. "Luminescence and FTIR Spectroscopy of ZnO Nanocrystals." Materials Science Forum 514-516 (May 2006): 1230–34. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.1230.

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Time-resolved luminescence and Furje Transformation Infrared (FTIR) absorption spectroscopy for ZnO nanocrystals prepared under different chemical reactions using microwave driven hydrothermal process was studied. OH- group stretching vibration frequency is considerably different in nanocrystals studied and in single ZnO crystal. It is shown that fractions of chemicals used in synthesis process could be found in nanopowders. Luminescence at ~2.0 eV (due to defect states in ZnO crystals and nanopowders) was suppressed in nanopowders obtained by urea method.

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34

Liang, Zhanguo, Jun Mu, Lei Han, and Hongquan Yu. "Microbe-Assisted Synthesis and Luminescence Properties of Monodispersed Tb3+-Doped ZnS Nanocrystals." Journal of Nanomaterials 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/519303.

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Tb3+-doped zinc sulfide (ZnS:Tb3+) nanocrystals were synthesized by spray precipitation with sulfate-reducing bacterial (SRB) culture at room temperature. The morphology of the SRB and ZnS:Tb3+nanocrystals was examined by scanning electron microscopy, and the ZnS:Tb3+nanocrystals were characterized by X-ray diffractometry and photoluminescence (PL) spectroscopy. The PL mechanism of ZnS:Tb3+nanocrystals was further analyzed, and the effects of Tb3+ion concentration on the luminescence properties of ZnS:Tb3+nanocrystals were studied. ZnS:Tb3+nanocrystals showed a sphalerite phase, and the prepared ZnS:Tb3+nanocrystals had high luminescence intensity under excitation at 369 nm. The main peak position of the absorption spectra positively blueshifted with increasing concentrations of Tb3+dopant. Based on the strength of the peak of the excitation and emission spectra, we inferred that the optimum concentration of the Tb3+dopant is 5 mol%. Four main emission peaks were obtained under excitation at 369 nm:489 nm (5D4→7F6), 545 nm (5D4→7F5), 594 nm (5D4→7F4), and 625 nm (5D4→7F3). Our findings suggest that nanocrystals have potential applications in photoelectronic devices and biomarkers.

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Zhang, Yuqin, Shi He, Honghong Yao, Hao Zuo, Shuang Liu, Chao Yang, and Guoying Feng. "Size Effect of Electrical and Optical Properties in Cr2+:ZnSe Nanowires." Nanomaterials 13, no. 2 (January 16, 2023): 369. http://dx.doi.org/10.3390/nano13020369.

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Previous studies have shown that the nano-crystallization process has an appreciable impact on the luminescence properties of nanocrystals, which determines their defect state composition, size and morphology. This project aims to explore the influence of nanocrystal size on the electrical and optical properties of Cr2+:ZnSe nanowires. A first-principles study of Cr2+:ZnSe nanowires with different sizes was carried out at 0 K in the density functional framework. The Cr2+ ion was found to prefer to reside at the surface of ZnSe nanowires. As the size of the nanocrystals decreased, a considerable short-wave-length shift in the absorption of the vis-near infrared wavelength was observed. A quantum mechanism for the wavelength tunability was discussed.

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Babkina, A. N., K. S. Zyryanova, Y. B. Egorova, A. S. Kulagina, R. R. Gavrilov, and A. A. Monogarova. "Investigation of spectral properties of potassium-aluminum-borate glass with CuCl - CuBr nanocrystals." Journal of Physics: Conference Series 2103, no. 1 (November 1, 2021): 012172. http://dx.doi.org/10.1088/1742-6596/2103/1/012172.

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Abstract Heat treatment conditions effect on the characteristics of exciton absorption and luminescence of CuCl and CuBr nanocrystals in potassium-aluminaborate glass is studied. The size effect of the band edge absorption and luminescence energy is confirmed. The simultaneous presence of copper halide nanocrystals and free monovalent copper ions in the glass matrix is shown. Possible conditions for the formation of mixed CuCl-CuBr crystals are considered.

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37

Liu, Li-wei, Si-yi Hu, Ying Pan, Jia-qi Zhang, Yue-shu Feng, and Xi-he Zhang. "Optimizing the synthesis of CdS/ZnS core/shell semiconductor nanocrystals for bioimaging applications." Beilstein Journal of Nanotechnology 5 (June 27, 2014): 919–26. http://dx.doi.org/10.3762/bjnano.5.105.

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In this study, we report on CdS/ZnS nanocrystals as a luminescence probe for bioimaging applications. CdS nanocrystals capped with a ZnS shell had enhanced luminescence intensity, stronger stability and exhibited a longer lifetime compared to uncapped CdS. The CdS/ZnS nanocrystals were stabilized in Pluronic F127 block copolymer micelles, offering an optically and colloidally stable contrast agents for in vitro and in vivo imaging. Photostability test exhibited that the ZnS protective shell not only enhances the brightness of the QDs but also improves their stability in a biological environment. An in-vivo imaging study showed that F127-CdS/ZnS micelles had strong luminescence. These results suggest that these nanoparticles have significant advantages for bioimaging applications and may offer a new direction for the early detection of cancer in humans.

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Romano, Francesco, Sara Angeloni, Giacomo Morselli, Raffaello Mazzaro, Vittorio Morandi, Jennifer R. Shell, Xu Cao, Brian W. Pogue, and Paola Ceroni. "Water-soluble silicon nanocrystals as NIR luminescent probes for time-gated biomedical imaging." Nanoscale 12, no. 14 (2020): 7921–26. http://dx.doi.org/10.1039/d0nr00814a.

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In vivo studies demonstrated tumor accumulation of luminescent SiNCs, 48 hours clearance and a 3-fold improvement of signal-to-noise ratio in time-gated imaging compared to steady-state acquisition, demonstrating their potentiality for luminescence guided surgery.

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39

Singh, Prashant K., Prashant K. Sharma, Manvendra Kumar, Ranu Dutta, Shanthy Sundaram, and Avinash C. Pandey. "Retracted Article: Red luminescent manganese-doped zinc sulphide nanocrystals and their antibacterial study." Journal of Materials Chemistry B 2, no. 5 (2014): 522–28. http://dx.doi.org/10.1039/c3tb21363c.

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40

Alexander, Dinu, Kukku Thomas, Monu Joy, P. R. Biju, N. V. Unnikrishnan, and Cyriac Joseph. "Structural and spectroscopic investigations on the quenching free luminescence of europium oxalate nanocrystals." Acta Crystallographica Section C Structural Chemistry 75, no. 5 (April 29, 2019): 589–97. http://dx.doi.org/10.1107/s2053229619005059.

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The structural features leading to the intense quenching free luminescence exhibited by europium oxalate nanocrystals, poly[[hexaaquatri-μ2-oxalato-dieuropium] 4.34-hydrate], {[Eu2(C2O4)3(H2O)6]·4.34H2O} n , is the focal point of this report. Europium oxalate nanocrystals were synthesized by a simple microwave-assisted co-precipitation method. Powder X-ray diffraction analysis revealed the monoclinic structure of the nanocrystals and the phase purity. The morphology and particle size were examined by transmission electron microscopy (TEM) analysis. Luminescence measurements on a series of samples of La2–x Eu x (C2O4)3·10H2O, with x varying in the range 0.1 to 2, established the quenching free nature exhibited by the europium oxalate nanocrystals. A single-crystal structure analysis was carried out and the quenching free luminescence is explained on the basis of the crystal structure. A detailed photoluminescence characterization was carried out using excitation and emission studies, decay analysis, and CIE coordinate and colour purity evaluation. The various spectroscopic parameters were evaluated by Judd–Ofelt theoretical analysis and the results are discussed on the basis of the crystal structure analysis.

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41

Zhou, Jigang, Xingtai Zhou, Ruying Li, Xueliang Sun, Zhifeng Ding, Jeffrey Cutler, and Tsun-Kong Sham. "Electronic structure and luminescence center of blue luminescent carbon nanocrystals." Chemical Physics Letters 474, no. 4-6 (June 2009): 320–24. http://dx.doi.org/10.1016/j.cplett.2009.04.075.

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42

Grevtseva I.G., Ovchinnikov O.V., Smirnov M.S., Kondratenko T.S., Derepko V.N., Hussein A.M.Kh., Egorov N.E., and Vozgorkova E.A. "Photostability of luminescence of Ag-=SUB=-2-=/SUB=-S quantum dots and Ag-=SUB=-2-=/SUB=-S/SiO-=SUB=-2-=/SUB=- core/shell structures." Optics and Spectroscopy 130, no. 12 (2022): 1634. http://dx.doi.org/10.21883/eos.2022.12.55254.4106-22.

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The paper presents regularities that demonstrate the effect of passivating ligands formation of thioglycolic acid and L-cysteine (TGA, L-Cys) and dielectric shells (SiO2) on Ag2S nanocrystals interface on the photostability of their IR luminescence. Using FTIR absorption spectroscopy, the interaction manifestations of passivating ligands molecules of TGA and L-Cys with Ag2S nanocrystals, as well as the formation of SiO2 shell due to the process of replacing organic ligands with a silica ligand (MPTMS) ("ligand exchange"), were found. In the case of replacing TGA with MPTMS, an increase in the luminescence quantum yield of Ag2S quantum dots (QDs) and its resistance to long-term exposure to exciting radiation was found. In the case of replacing L-Cys with MPTMS, the formation of a fragmentary SiO2/L-Cys shell on Ag2S nanocrystals was observed due to the partial replacement of L-Cys with MPTMS, which contributes to the reverse photodegradation of KT Ag2S luminescence of as a result of SiO2/L-Cys shell photodestruction. Keywords: photoluminescence, luminescence photostability, quantum yield, quantum dot, core/shell structures, FTIR spectroscopy.

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43

Mao, Huibing, Ling Du, Ye Chen, Bo Li, Rong Huang, and Jiqing Wang. "Luminescence Emission Mediated by Surface Plasmon in the Semiconductor Quantum Dots." Nano 10, no. 01 (January 2015): 1550009. http://dx.doi.org/10.1142/s1793292015500095.

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The luminescence of the hybrid CdSe / ZnS QDs– Ag nanocrystals has a weak blue shift in comparison with the luminescence of the pure quantum dots (QDs). The luminescence of the CdSe / ZnS QDs only has a single exponential decay process, and the decay rates are almost same for different emission wavelengths. The luminescence of the hybrid CdSe / ZnS QDs– Ag nanocrystals structure has two decay processes: The first is a fast decay process, and then there is a slow decay process with nearly the same decay rate of the pure QDs. The fast decay process is due to the surface plasmon coupling and the coupling rate depends on the energy difference between the confined exciton in the QDs and the resonance energy of the Ag plasmon.

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Marciniak, L., W. Strek, Y. Guyot, and D. Hreniak. "Synthesis and luminescent properties of La1−xNdxP5O14 nanocrystals." Phys. Chem. Chem. Phys. 16, no. 33 (2014): 18004–9. http://dx.doi.org/10.1039/c4cp02265c.

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The impact of dopant concentration on spectroscopic properties of La_1−xNd_xP₅O₁₂ nanocrystals: the luminescence decay profiles – (a); emission spectra – (b); and luminescence branching ratios – (c).

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Yang, Tingyu, Jinglei Qin, Jinling Zhang, Lanying Guo, Mu Yang, Xi Wu, Mei You, and Hongshang Peng. "Recent Progresses in NIR-II Luminescent Bio/Chemo Sensors Based on Lanthanide Nanocrystals." Chemosensors 10, no. 6 (May 30, 2022): 206. http://dx.doi.org/10.3390/chemosensors10060206.

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Fluorescent bio/chemosensors are widely used in the field of biological research and medical diagnosis, with the advantages of non-invasiveness, high sensitivity, and good selectivity. In particular, luminescent bio/chemosensors, based on lanthanide nanocrystals (LnNCs) with a second near-infrared (NIR-II) emission, have attracted much attention, owing to greater penetration depth, aside from the merits of narrow emission band, abundant emission lines, and long lifetimes. In this review, NIR-II LnNCs-based bio/chemo sensors are summarized from the perspectives of the mechanisms of NIR-II luminescence, synthesis method of LnNCs, strategy of luminescence enhancement, sensing mechanism, and targeted bio/chemo category. Finally, the problems that exist in present LnNCs-based bio/chemosensors are discussed, and the future development trend is prospected.

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Komarov, F., L. Vlasukova, O. Milchanin, A. Mudryi, J. Zuk, K. Pyszniak, and M. Kulik. "Nanocrystal- and Dislocation-Related Luminescence in Si Matrix with InAs Nanocrystals." Acta Physica Polonica A 120, no. 1 (July 2011): 204–7. http://dx.doi.org/10.12693/aphyspola.120.204.

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47

Oda, M., M. Y. Shen, and T. Goto. "High Density Exciton Dynamics of CuBr Nanocrystals Embedded in PMMA." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3912–15. http://dx.doi.org/10.1142/s0217979201008986.

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When CuBr nanocrystals (NCs) embedded in poly methyl methacrylate are strongly excited, there appears a new luminescence band at the low energy side of exciton luminescence peak. The luminescence band is associated with biexcitons in the CuBr NCs. As the excitation intensity increases, the biexciton luminescence band shows obvious broadening, while the exciton band does not. Interaction among more than three excitons may cause this broadening effect. Optical gain has also been found by pump-probe measurement around the biexciton luminescence band at 77K. The decay time of the optical gain 15ps coincides with that of the biexciton luminescence band, which means that the lifetime of the biexciton is 15ps.

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48

Braddock, Isabel H. B., Maya Al Sid Cheikh, Joydip Ghosh, Roma E. Mulholland, Joseph G. O’Neill, Vlad Stolojan, Carol Crean, Stephen J. Sweeney, and Paul J. Sellin. "Formamidinium Lead Halide Perovskite Nanocomposite Scintillators." Nanomaterials 12, no. 13 (June 22, 2022): 2141. http://dx.doi.org/10.3390/nano12132141.

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While there is great demand for effective, affordable radiation detectors in various applications, many commonly used scintillators have major drawbacks. Conventional inorganic scintillators have a fixed emission wavelength and require expensive, high-temperature synthesis; plastic scintillators, while fast, inexpensive, and robust, have low atomic numbers, limiting their X-ray stopping power. Formamidinium lead halide perovskite nanocrystals show promise as scintillators due to their high X-ray attenuation coefficient and bright luminescence. Here, we used a room-temperature, solution-growth method to produce mixed-halide FAPbX3 (X = Cl, Br) nanocrystals with emission wavelengths that can be varied between 403 and 531 nm via adjustments to the halide ratio. The substitution of bromine for increasing amounts of chlorine resulted in violet emission with faster lifetimes, while larger proportions of bromine resulted in green emission with increased luminescence intensity. By loading FAPbBr3 nanocrystals into a PVT-based plastic scintillator matrix, we produced 1 mm-thick nanocomposite scintillators, which have brighter luminescence than the PVT-based plastic scintillator alone. While nanocomposites such as these are often opaque due to optical scattering from aggregates of the nanoparticles, we used a surface modification technique to improve transmission through the composites. A composite of FAPbBr3 nanocrystals encapsulated in inert PMMA produced even stronger luminescence, with intensity 3.8× greater than a comparative FAPbBr3/plastic scintillator composite. However, the luminescence decay time of the FAPbBr3/PMMA composite was more than 3× slower than that of the FAPbBr3/plastic scintillator composite. We also demonstrate the potential of these lead halide perovskite nanocomposite scintillators for low-cost X-ray imaging applications.

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Гревцева, И. Г., О. В. Овчинников, М. С. Смирнов, Т. С. Кондратенко, В. Н. Дерепко, А. М. Х. Хуссейн, Н. Е. Егоров, and E. A. Возгорькова. "Фотостабильность люминесценции квантовых точек Ag-=SUB=-2-=/SUB=-S и структур ядро/оболочка Ag-=SUB=-2-=/SUB=-S/SiO-=SUB=-2-=/SUB=-." Оптика и спектроскопия 130, no. 12 (2022): 1910. http://dx.doi.org/10.21883/os.2022.12.54100.4106-22.

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The paper presents regularities that demonstrate the effect of passivating ligands formation of thioglycolic acid and L-cysteine (TGA, L-Cys) and dielectric shells (SiO2) on Ag2S nanocrystals interface on the photostability of their IR luminescence. Using FTIR absorption spectroscopy, the interaction manifestations of passivating ligands molecules of TGA and L-Cys with Ag2S nanocrystals, as well as the formation of SiO2 shell due to the process of replacing organic ligands with a silica ligand (MPTMS) ("ligand exchange"), were found. In the case of replacing TGA with MPTMS, an increase in the luminescence quantum yield of Ag2S quantum dots (QDs) and its resistance to long-term exposure to exciting radiation was found. In the case of replacing L-Cys with MPTMS, the formation of a fragmentary SiO2/L-Cys shell on Ag2S nanocrystals was observed due to the partial replacement of L-Cys with MPTMS, which contributes to the reverse photodegradation of Ag2S QDs luminescence of as a result of SiO2/L-Cys shell photodestruction.

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Lobnik, Aleksandra, Špela Korent Urek, and Matejka Turel. "Quantum Dots Based Optical Sensors." Defect and Diffusion Forum 326-328 (April 2012): 682–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.682.

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Luminescent sensors are chemical systems that can deliver information on the presence of selected analytes through the variations in their luminescence emission. With the advent of luminescent nanoparticles several new applications in the field of chemical sensing were explored. Among them, quantum dots (QD) represent inorganic semiconductor nanocrystals that are advantageous over conventional organic dyes from many different points of view. In this short review, the optical detection of various analytes using QD-based probes/sensors is presented and significant sensors characteristics are discussed. The biosensing approaches are not included in this article.

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Journal articles on the topic 'Nanocrystals - Luminescence'

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