Journal articles: 'Nanocrystals'

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Ichiyanagi, Kouhei, Hiroshi Sekiguchi, Tokushi Sato, Shunsuke Nozawa, Ayana Tomita, Manabu Hoshino, Shin-ichi Adachi, and Yuji C. Sasaki. "Cooling dynamics of self-assembled monolayer coating for integrated gold nanocrystals on a glass substrate." Journal of Synchrotron Radiation 22, no. 1 (January 1, 2015): 29–33. http://dx.doi.org/10.1107/s1600577514019730.

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Picosecond time-resolved X-ray diffraction has been used to study the nanoscale thermal transportation dynamics of bare gold nanocrystals and thiol-based self-assembled monolayer (SAM)-coated integrated gold nanocrystals on a SiO2glass substrate. A temporal lattice expansion of 0.30–0.33% was observed in the bare and SAM-coated nanocrystals on the glass substrate; the thermal energy inside the gold nanocrystals was transported to the contacted substrate through the gold–SiO2interface. The interfacial thermal conductivity between the single-layered gold nanocrystal film and the SiO2substrate is estimated to be 45 MW m−2 K−1from the decay of the Au 111 peak shift, which was linearly dependent on the transient temperature. For the SAM-coated gold nanocrystals, the thermal dissipation was faster than that of the bare gold nanocrystal film. The thermal flow from the nanocrystals to the SAM-coated molecules promotes heat dissipation from the laser-heated SAM-coated gold nanocrystals. The thermal transportation of the laser-heated SAM-coated gold nanocrystal film was analyzed using the bidirectional thermal dissipation model.

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Maksimova, G. M., and V. A. Burdov. "Universality of the Förster’s model for resonant exciton transfer in ensembles of nanocrystals." Journal of Chemical Physics 156, no. 16 (April 28, 2022): 164301. http://dx.doi.org/10.1063/5.0085355.

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For nanocrystals in a strong quantum confinement regime, it has been confirmed analytically that resonant exciton transfer proceeds in full accordance with the Förster mechanism. This means that the virtual exciton transitions between the nanocrystals of close sizes are governed only by the dipole–dipole interaction of nanocrystals even in very dense ensembles, while the contributions of all other higher-order multipoles are negligibly small. Based on a simple isotropic model of the envelope function approximation and neglecting the electron–hole interaction inside each nanocrystal, we have computed the rate of the resonant exciton transfer between two nanocrystals. Using the obtained result, we have estimated, for some arbitrarily chosen nanocrystal, the total rate of the exciton non-radiative annihilation caused by the possibility of its resonant virtual transitions into all other nanocrystals of the ensemble. The total rate dependence on the nanocrystal size is determined only by the size distribution function of nanocrystals in the ensemble.

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Cheng, Zhongyao, Yumei Lian, Zul Kamal, Xin Ma, Jianjun Chen, Xinbo Zhou, Jing Su, and Mingfeng Qiu. "Nanocrystals Technology for Pharmaceutical Science." Current Pharmaceutical Design 24, no. 21 (October 15, 2018): 2497–507. http://dx.doi.org/10.2174/1381612824666180518082420.

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Background: Nanocrystals technology is a promising method for improving the dissolution rate and enhancing the bioavailability of poorly soluble drugs. In recent years, it has been developing rapidly and applied to drug research and engineering. Nanocrystal drugs can be formulated into various dosage forms. Objective: This review mainly focused on the nanocrystals technology and its application in pharmaceutical science. Firstly, different preparation methods of nanocrystal technology and the characterization of nanocrystal drugs are briefly described. Secondly, the application of nanocrystals technology in pharmaceutical science is mainly discussed followed by the introduction of sustained release formulations. Then, the scaling up process, marketed nanocrystal drug products and regulatory aspects about nanodrugs are summarized. Finally, the specific challenges and opportunities of nanocrystals technology for pharmaceutical science are summarized and discussed. Conclusion: This review will provide a comprehensive guide for scientists and engineers in the field of pharmaceutical science and biochemical engineering.

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Shen, Hao, Huabao Shang, Yuhan Gao, Deren Yang, and Dongsheng Li. "Efficient Sensitized Photoluminescence from Erbium Chloride Silicate via Interparticle Energy Transfer." Materials 15, no. 3 (January 30, 2022): 1093. http://dx.doi.org/10.3390/ma15031093.

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In this study, we prepare Erbium compound nanocrystals and Si nanocrystal (Si NC) co-embedded silica film by the sol-gel method. Dual phases of Si and Er chloride silicate (ECS) nanocrystals were coprecipitated within amorphous silica. Effective sensitized emission of Er chloride silicate nanocrystals was realized via interparticle energy transfer between silicon nanocrystal and Er chloride silicate nanocrystals. The influence of density and the distribution of sensitizers and Er compounds on interparticle energy transfer efficiency was discussed. The interparticle energy transfer between the semiconductor and erbium compound nanocrystals offers some important insights into the realization of efficient light emission for silicon-based integrated photonics.

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Basa, P., G. Molnár, L. Dobos, B. Pécz, L. Tóth, A. L. Tóth, A. A. Koós, L. Dózsa, Á. Nemcsics, and Zs J. Horváth. "Formation of Ge Nanocrystals in SiO2 by Electron Beam Evaporation." Journal of Nanoscience and Nanotechnology 8, no. 2 (February 1, 2008): 818–22. http://dx.doi.org/10.1166/jnn.2008.a122.

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Ge nanocrystals were formed by electron beam evaporation on SiO2 covered Si substrates. The size and distribution of the nanocrystals were studied by atomic force microscopy, scanning electron microscopy and cross-sectional transmission electron microscopy. Dependencies of the nanocrystal size, of the nanocrystal surface coverage, and sheet resistance obtained by van der Pauw method of the Ge layer have been found on the evaporation time. The suggested growth mechanism for the formation of nanocrystals is the Volmer-Weber type. The sheet resistance exhibited a power dependence on the nanocrystal size.

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Mohammadrezaee, Mohammad, Naser Hatefi-Kargan, and Ahmadreza Daraei. "Enhancing crystal quality and optical properties of GaN nanocrystals by tuning pH of the synthesis solution." Zeitschrift für Naturforschung A 75, no. 6 (May 26, 2020): 551–56. http://dx.doi.org/10.1515/zna-2019-0378.

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AbstractGallium nitride nanocrystals as a wide bandgap semiconductor material for optoelectronic applications can be synthesized using chemical methods. In this research using co-precipitation and nitridation processes gallium nitride nanocrystals have been synthesized, and by tuning pH of the synthesis solution at the co-precipitation step, crystal quality and optical property of the resultant gallium nitride nanocrystals have been enhanced. Gallium nitride nanocrystal samples were synthesized using solutions with pH values of 2.1, 4.8, 7.8, and 9.0, and then nitridation at 950 °C under the flow of ammonia gas. The synthesized nanocrystal samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and photoluminescence techniques. The XRD data show that the nanocrystals have hexagonal wurtzite crystal structure, and using Scherer’s equation the sizes of the synthesized nanocrystals are 23.6, 26.6, 19.7, and 10.4 nm for the samples synthesized using the solutions with pH values of 2.1, 4.8, 7.8, and 9.0 respectively. The sizes of the nanocrystals obtained from SEM images are larger than the values obtained using Scherer’s equation, due to the aggregation of nanocrystals. EDX spectra show that pH of the synthesis solution affects the elemental stoichiometry of the gallium nitride nanocrystals. We obtained better stoichiometry for the nanocrystal sample synthesized using solution with the pH of 4.8. Photoluminescence spectra show that for this sample the emission intensity is higher than the others.

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Natrayan, L., P. V. Arul Kumar, S. Kaliappan, S. Sekar, Pravin P. Patil, R. Jayashri, and E. S. Esakki Raj. "Analysis of Incorporation of Ion-Bombarded Nickel Ions with Silicon Nanocrystals for Microphotonic Devices." Journal of Nanomaterials 2022 (August 16, 2022): 1–7. http://dx.doi.org/10.1155/2022/5438084.

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Nanotechnology is playing a greater role in biomedical engineering. Microphotonic technology is on another side, having faster growth with more requirements. The nanocrystals are a part of nanotechnology which uses silicon for manufacturing. These silicon nanocrystals have the optical property mostly used in microphotonic devices. Silicon nanocrystals are of biocompatibility with less toxicity. Therefore, the advancement in the silicon nanocrystal helps develop more microphotonic devices for biological purposes. One critical factor of silicon nanocrystal is the surface defects or surface imperfections. Surface passivation is the method employed for rectifying this disadvantage of silicon nanocrystal. Another major thing is that silicon nanocrystals are size dependent. So proper variation on the surface is required for yielding high performance of the nanocrystal. After characterizing the surface of the silicon nanocrystal, ion bombardment can occur. Nickel is a lustrous white chemical element which is less reactive when it is of a smaller size. So ion bombardment of nickel ion on the surface of the silicon nanocrystal can be done to improvise the performance of the microphotonic devices. Nearly there is an excess of 20 a.u. of photoluminescence intensity yielded. The relative fluorescence is also increased by 150 a.u. This research work enhanced the silicon nanocrystal using ion bombardment of nickel ion, which increased energy traps resulting in more intensities.

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Kotian, Vinith, Marina Koland, and Srinivas Mutalik. "Nanocrystal-Based Topical Gels for Improving Wound Healing Efficacy of Curcumin." Crystals 12, no. 11 (November 3, 2022): 1565. http://dx.doi.org/10.3390/cryst12111565.

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Topical curcumin shows poor local availability because of its low aqueous solubility and inadequate tissue absorption. Curcumin nanocrystals were prepared by sonoprecipitation followed by lyophilization to improve surface area and solubility. The formulation was optimized by the Design of Experiment (DoE) approach. The nanocrystals were characterized for particle size, zeta potential, polydispersity index, scanning electron microscopy (SEM), powder x-ray diffraction (PXRD), practical yield and in vitro drug release studies. The nanocrystal-incorporated gel was evaluated for drug content, ex vivo permeation, in vivo skin irritation, and in vivo wound healing activity. Time of sonication and amplitude influenced the optimization of curcumin nanocrystals, but the effect of stabilizer concentrations was not significant beyond 0.5% w/w. SEM images of curcumin nanocrystals revealed irregular and plate-shaped particles with rough surfaces. PXRD patterns of curcumin nanocrystals showed low crystallinity compared to unprocessed curcumin powder. An in vitro drug release study demonstrated significant improvement in the percentage cumulative drug release in the form of nanocrystals compared to the unprocessed curcumin, and the release profile exhibited first-order kinetics. Curcumin nanocrystal gel showed 93.86% drug content and was free of skin irritation potential. Excision wound healing activity in albino rats showed that the curcumin nanocrystal gel exhibited significantly faster wound contraction than curcumin powder-incorporated gel.

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Wang, Yu, Xinxing Peng, Alex Abelson, Penghao Xiao, Caroline Qian, Lei Yu, Colin Ophus, et al. "Dynamic deformability of individual PbSe nanocrystals during superlattice phase transitions." Science Advances 5, no. 6 (June 2019): eaaw5623. http://dx.doi.org/10.1126/sciadv.aaw5623.

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The behavior of individual nanocrystals during superlattice phase transitions can profoundly affect the structural perfection and electronic properties of the resulting superlattices. However, details of nanocrystal morphological changes during superlattice phase transitions are largely unknown due to the lack of direct observation. Here, we report the dynamic deformability of PbSe semiconductor nanocrystals during superlattice phase transitions that are driven by ligand displacement. Real-time high-resolution imaging with liquid-phase transmission electron microscopy reveals that following ligand removal, the individual PbSe nanocrystals experience drastic directional shape deformation when the spacing between nanocrystals reaches 2 to 4 nm. The deformation can be completely recovered when two nanocrystals move apart or it can be retained when they attach. The large deformation, which is responsible for the structural defects in the epitaxially fused nanocrystal superlattice, may arise from internanocrystal dipole–dipole interactions.

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Liu, Jie, Rui Zhang, Meiyu Ci, Shuying Sui, and Ping Zhu. "Sodium alginate/cellulose nanocrystal fibers with enhanced mechanical strength prepared by wet spinning." Journal of Engineered Fibers and Fabrics 14 (January 2019): 155892501984755. http://dx.doi.org/10.1177/1558925019847553.

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Sodium alginate/cellulose nanocrystal fibers were prepared using a wet spinning method to enhance the mechanical strength of sodium alginate fibers. Cellulose nanocrystals were prepared by sulfuric acid hydrolysis method. The particle diameter size was measured, and the morphology of cellulose nanocrystals was characterized by transmission electron microscopy and scanning electron microscopy. The structure and mechanical properties of sodium alginate/cellulose nanocrystal fibers were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and mechanical strength testing. The incorporation of cellulose nanocrystals significantly improved the strength of alginate fibers because of the uniform distribution of cellulose nanocrystals in the alginate matrix. The tensile strength and elongation at break of the alginate fibers increased from 1.54 to 2.05 cN/dtex and from 8.29% to 15.05% with increasing cellulose nanocrystals content from 0 to 2 wt%, respectively.

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ONODERA, T., M. YOSHIDA, S. OKAZOE, S. FUJITA, H. KASAI, S. OKADA, H. OIKAWA, and H. NAKANISHI. "AC ELECTRIC-FIELD-INDUCED ORIENTATION OF POLAR ORGANIC NANOCRYSTAL IN DISPERSE SYSTEM." International Journal of Nanoscience 01, no. 05n06 (October 2002): 737–41. http://dx.doi.org/10.1142/s0219581x0200098x.

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Monodispersed DAST nanocrystals have almost been successfully fabricated by means of the inverse reprecipitation method. By employing AC electric field, high electric field of above ca. 1.0 kVcm -1 could be applied to polar DAST nanocrystals dispersed in decahydronaphthalene, so as to avoid electrophoresis of nanocrystals under DC electric field. The response of DAST nanocrystal dispersion to applied AC electric field was analyzed phenomenologically by fitting Langevin function, which provided a large permanent dipole moment of DAST nanocrystal. In addition, we have succeeded in in situ observation of AC electric-field-induced orientational motion of DAST crystals by using an optical microscope. The present DAST nanocrystal dispersion system will be expected as an optical device like display monitor.

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Fan, Mingxue, Sicong Geng, Yang Liu, Jing Wang, Yiting Wang, Jian Zhong, Zhiqiang Yan, and Lei Yu. "Nanocrystal Technology as a Strategy to Improve Drug Bioavailability and Antitumor Efficacy for the Cancer Treatment." Current Pharmaceutical Design 24, no. 21 (October 15, 2018): 2416–24. http://dx.doi.org/10.2174/1381612824666180515154109.

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Background and Objective: Nanocrystal technology is an effective approach which can increase the dissolution rate of poorly water-soluble drugs by raising their saturation solubility, thus improving the drug bioavailability. With the development of nanocrystals, its preparation approaches have gradually matured, which can be generally divided into Bottom-up, Top-down and Combinative technologies. Methods: A systematic literature review in the field of nanocrystal technology for the cancer treatment was scanned and collected data was detailedly analyzed and summarized. Results: Over the past decade, several anticancer drug nanocrystals have been explored and evaluated in preclinical studies and clinical trials. This review mainly covers the utilizations of the nanocrystal technology in enhancing the saturation solubility of anticancer drugs associated with the increased bioavailability and anticancer efficacy. Preparation methods and characterizations of nanocrystals are also introduced in brief. In addition, one critical step in the formation of drug nanocrystals is selecting suitable stabilizers for the system. Many types of research are heading towards the role of the stabilizers in the final nanocrystals formulation. So we summed up several commonly used stabilizers in order to give a reference to the further study. At last, we discussed some considerations raised by the application of nanocrystal drugs for cancer treatment. Conclusion: This review is likely to enable a detailed insight on nanocrystal technology as a strategy to improve drug bioavailability and antitumor efficacy for the cancer treatment and be of particular interest to pharmaceutical industry.

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Saez Cabezas, Camila A., Gary K. Ong, Ryan B. Jadrich, Beth A. Lindquist, Ankit Agrawal, Thomas M. Truskett, and Delia J. Milliron. "Gelation of plasmonic metal oxide nanocrystals by polymer-induced depletion attractions." Proceedings of the National Academy of Sciences 115, no. 36 (August 20, 2018): 8925–30. http://dx.doi.org/10.1073/pnas.1806927115.

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Gelation of colloidal nanocrystals emerged as a strategy to preserve inherent nanoscale properties in multiscale architectures. However, available gelation methods to directly form self-supported nanocrystal networks struggle to reliably control nanoscale optical phenomena such as photoluminescence and localized surface plasmon resonance (LSPR) across nanocrystal systems due to processing variabilities. Here, we report on an alternative gelation method based on physical internanocrystal interactions: short-range depletion attractions balanced by long-range electrostatic repulsions. The latter are established by removing the native organic ligands that passivate tin-doped indium oxide (ITO) nanocrystals while the former are introduced by mixing with small PEG chains. As we incorporate increasing concentrations of PEG, we observe a reentrant phase behavior featuring two favorable gelation windows; the first arises from bridging effects while the second is attributed to depletion attractions according to phase behavior predicted by our unified theoretical model. Our assembled nanocrystals remain discrete within the gel network, based on X-ray scattering and high-resolution transmission electron microscopy. The infrared optical response of the gels is reflective of both the nanocrystal building blocks and the network architecture, being characteristic of ITO nanocrystals’ LSPR with coupling interactions between neighboring nanocrystals.

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Zhigunov, D. M., A. A. Popov, Yu M. Chesnokov, A. L. Vasiliev, A. M. Lebedev, I. A. Subbotin, S. N. Yakunin, O. A. Shalygina, and I. A. Kamenskikh. "Near-IR Emitting Si Nanocrystals Fabricated by Thermal Annealing of SiNx/Si3N4 Multilayers." Applied Sciences 9, no. 22 (November 6, 2019): 4725. http://dx.doi.org/10.3390/app9224725.

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Silicon nanocrystals in silicon nitride matrix are fabricated by thermal annealing of SiNx/Si3N4 multilayered thin films, and characterized by transmission electron microscopy, X-ray reflectivity and diffraction analysis, photoluminescence and X-ray photoelectron spectroscopy techniques. Si nanocrystals with a mean size of about 4 nm are obtained, and their properties are studied as a function of SiNx layer thickness (1.6–2 nm) and annealing temperature (900–1250 °C). The effect of coalescence of adjacent nanocrystals throughout the Si3N4 barrier layers is observed, which results in formation of distinct ellipsoidal-shaped nanocrystals. Complete intermixing of multilayered film accompanied by an increase of nanocrystal mean size for annealing temperature as high as 1250 °C is shown. Near-IR photoluminescence with the peak at around 1.3–1.4 eV is detected and associated with quantum confined excitons in Si nanocrystals: Photoluminescence maximum is red shifted upon an increase of nanocrystal mean size, while the measured decay time is of order of microsecond. The position of photoluminescence peak as compared to the one for Si nanocrystals in SiO2 matrix is discussed.

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Svrcek, Vladimir. "(Invited) Atmospheric Plasmas Synthesized Nanocrystals with Quantum Confinement and Quantum Hybrids in Photovoltaics." ECS Meeting Abstracts MA2022-02, no. 19 (October 9, 2022): 889. http://dx.doi.org/10.1149/ma2022-0219889mtgabs.

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Nanocrystals share lot of advantages of organics namely scalable and controlled synthesis, an ability to be processed in solution while additionally retaining the broadband absorption and superior transport properties of traditional photovoltaic semiconductors. Nanocrystal solar cells have the potential to considerably increase the maximum attainable thermodynamic conversion efficiency (> 50%). Nanocrystal solution-processed can be used in solar cell structure not only as an absorber but also as electron and hole transport layer where the HOMO and LUMO levels can be efficiently controlled by size and/or plasma induced surface engineering directly in colloidal solution. Solution-processed and surface engineered nanocrystals with quantum confinement can be then further used to fabricate new class of quantum hybrids when blended for instance with polymers or perovskites and serves as absorbing and/or e-h transporting material. In this presentation, we overview the atmospheric plasma-based approaches to synthesis and surface engineering of nanocrystals with quantum confinement. We will compare surface engineering by fs laser processing in liquid solutions and synthesis of nanocrystals with strong quantum confinement by atmospheric plasmas. Moreover, to understand the thermal stability of nanocrystals observed experimentally, we calculate the cohesive and the formation energies of nanocrystals by means of first-principle calculations. Finally, we overview our recent progress in integration of surface engineered nanocrystal as a quantum hybrids incorporated within perovskites solar cells.

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Lin, Weyde M. M., Maksym Yarema, Mengxia Liu, Edward Sargent, and Vanessa Wood. "Nanocrystal Quantum Dot Devices: How the Lead Sulfide (PbS) System Teaches Us the Importance of Surfaces." CHIMIA International Journal for Chemistry 75, no. 5 (May 28, 2021): 398–413. http://dx.doi.org/10.2533/chimia.2021.398.

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Semiconducting thin films made from nanocrystals hold potential as composite hybrid materials with new functionalities. With nanocrystal syntheses, composition can be controlled at the sub-nanometer level, and, by tuning size, shape, and surface termination of the nanocrystals as well as their packing, it is possible to select the electronic, phononic, and photonic properties of the resulting thin films. While the ability to tune the properties of a semiconductor from the atomistic- to macro-scale using solution-based techniques presents unique opportunities, it also introduces challenges for process control and reproducibility. In this review, we use the example of well-studied lead sulfide (PbS) nanocrystals and describe the key advances in nanocrystal synthesis and thin-film fabrication that have enabled improvement in performance of photovoltaic devices. While research moves forward with novel nanocrystal materials, it is important to consider what decades of work on PbS nanocrystals has taught us and how we can apply these learnings to realize the full potential of nanocrystal solids as highly flexible materials systems for functional semiconductor thin-film devices. One key lesson is the importance of controlling and manipulating surfaces.

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Fu, Hongbing, Debao Xiao, Ruimin Xie, Xuehai Ji, and Jian-Nian Yao. "Formation of the charge-transfer exciton in 1,3,5-triphenyl-2-pyrazoline nanocrystals." Canadian Journal of Chemistry 81, no. 1 (January 1, 2003): 7–13. http://dx.doi.org/10.1139/v02-193.

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A series of 1,3,5-triphenyl-2-pyrazoline (TPP) nanocrystals were prepared by the reprecipitation method. The electronic transitions of TPP nanocrystals have been studied using both absorption and fluorescence spectra. An absorption feature at about 400 nm gradually appeared with increasing nanocrystal size. This feature resulted from the formation of the charge-transfer (CT) exciton in nanocrystals. It was also supported by the longer decay time of the nanocrystal emission from CT compared with that of the solution emission from S1 at 298 K. On the other hand, the different behavior of the molecular ππ* and nπ* transitions originates from the different overlapping modes of the pyrazoline π orbital and n-electron orbital, according to the molecular model calculations. The nanocrystal emission from both the S1 and CT states was found at 77 K; moreover, the emission intensity redistributed from S1 to CT with increasing nanocrystal size. In contrast, at 298 K, only the emission from the CT states was observed, since the thermal fluctuation easily relaxes the excited electrons into CT states through vibration. Key words: reprecipitation method, organic nanocrystals, charge-transfer exciton, size-dependent property.

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Liu, Xiaowang, Renren Deng, Yuhai Zhang, Yu Wang, Hongjin Chang, Ling Huang, and Xiaogang Liu. "Probing the nature of upconversion nanocrystals: instrumentation matters." Chemical Society Reviews 44, no. 6 (2015): 1479–508. http://dx.doi.org/10.1039/c4cs00356j.

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Understanding upconversion nanocrystals: this review intends to summarize instrumental matters related to the characterization of upconversion nanocrystals from surface structures to intrinsic properties to ultimate challenges in nanocrystal analysis at single-particle levels.

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Yang, Tung-Han, Shan Zhou, Kyle D. Gilroy, Legna Figueroa-Cosme, Yi-Hsien Lee, Jenn-Ming Wu, and Younan Xia. "Autocatalytic surface reduction and its role in controlling seed-mediated growth of colloidal metal nanocrystals." Proceedings of the National Academy of Sciences 114, no. 52 (December 11, 2017): 13619–24. http://dx.doi.org/10.1073/pnas.1713907114.

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The growth of colloidal metal nanocrystals typically involves an autocatalytic process, in which the salt precursor adsorbs onto the surface of a growing nanocrystal, followed by chemical reduction to atoms for their incorporation into the nanocrystal. Despite its universal role in the synthesis of colloidal nanocrystals, it is still poorly understood and controlled in terms of kinetics. Through the use of well-defined nanocrystals as seeds, including those with different types of facets, sizes, and internal twin structure, here we quantitatively analyze the kinetics of autocatalytic surface reduction in an effort to control the evolution of nanocrystals into predictable shapes. Our kinetic measurements demonstrate that the activation energy barrier to autocatalytic surface reduction is highly dependent on both the type of facet and the presence of twin boundary, corresponding to distinctive growth patterns and products. Interestingly, the autocatalytic process is effective not only in eliminating homogeneous nucleation but also in activating and sustaining the growth of octahedral nanocrystals. This work represents a major step forward toward achieving a quantitative understanding and control of the autocatalytic process involved in the synthesis of colloidal metal nanocrystals.

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Harfenist, S. A., Z. L. Wang, M. M. Alvarez, I. Vezmar, and R. L. Whetten. "FCC Superlattice Packing of Faceted Silver Nanocrystals." Microscopy and Microanalysis 3, S2 (August 1997): 403–4. http://dx.doi.org/10.1017/s1431927600008904.

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The ordering of size selected nanocrystaline particles into large, well ordered supercrystals has been under recent study. Here we describe the ordering of silver nanocrystals, of core diameter ca. 4.5nm, passivated with alkythiolate self-assembled monolayers. The faceted nanocrystals are found to size selectively condense into ordered supercrystals with edge lengths on the order of 0.1 to 0.5 microns. Further, evidence has been found in High Resolution TEM micrographs of packed monolayers of these same nanocrystals implying an orientational ordering of the silver nanocrystals’ atomic lattices within and co-aligning with the supercrystal’s “superlattice”. A three dimensional model using a truncated octahedron for the nanocrystal core morphology is constructed from this evidence into an FCC superlattice which fits the remaining experimental observations.Micrographs of the same region of a nanocrystal Ag supercrystal (NCASX) are shown in figure 1 under differing defocus conditions.

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Komarov, Fadey, Altynay Togambayeva, Ludmila Vlasukova, Irina Parkhomenko, Oleg Milchanin, Maksim Makhavikov, and Murat Tolkynay. "Ion-Beam Synthesis of InSb Nanocrystals in Si Matrix." Advanced Materials Research 679 (April 2013): 9–13. http://dx.doi.org/10.4028/www.scientific.net/amr.679.9.

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The results of structural and optical investigation of crystalline Si with embedded InSb nanocrystals are reported. These nanocrystals were synthesized in silicon matrix by means of high-fluence “hot” implantation of Sb and In ions followed by thermal treatment. TEM gives an evidence of nanocrystal formation in implanted and annealed samples as well as an existence of microtwins and dislocation-type defects and substantial residual mechanical strains. We have identified nanocrystals as InSb from RS data. Mechanical strains in “silicon – InSb nanocrystals” system have been evaluated, too.

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Kim, Na-Ri, Kyung-Kwang Joo, and Hyun-Gi Lee. "Investigating the Potential of Perovskite Nanocrystal-Doped Liquid Scintillator: A Feasibility Study." Sensors 23, no. 23 (November 29, 2023): 9490. http://dx.doi.org/10.3390/s23239490.

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Liquid scintillators are extensively employed as targets in neutrino experiments and in medical radiography. Perovskite nanocrystals are recognized for their tunable emission spectra and high photoluminescence quantum yields. In this study, we investigated the feasibility of using perovskites as an alternative to fluor, a substance that shifts the wavelengths. The liquid scintillator candidates were synthesized by doping perovskite nanocrystals with emission wavelengths of 450, 480, and 510 nm into fluor PPO with varying nanocrystal concentrations in a toluene solvent. The several properties of the perovskite nanocrystal-doped liquid scintillator were measured and compared with those of a secondary wavelength shifter, bis-MSB. The emission spectra of the perovskite nanocrystal-doped liquid scintillator exhibited a distinct monochromatic wavelength, indicating energy transfer from PPO to the perovskite nanocrystals. Using a 60Co radioactive source setup with two photomultiplier tubes (PMTs), the light yields, pulse shape, and wavelength shifts of the scintillation events were measured. The light yields were evaluated based on the observed Compton edges from γ-rays, and compared across the synthesized samples. A decrease (or increase) in area-normalized PMT pulse height was observed at higher perovskite nanocrystal (or PPO) concentrations. The results demonstrated the sufficient potential of perovskite nanocrystals as an alternative to traditional wavelength shifters in a liquid scintillator.

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Zhang, Xun, Long Li, Xiang Gao, Hui Zhang, Jing Gao, Yimeng Du, Xiaowu Huang, and Aiping Zheng. "In Vitro Evaluation of Quercetin Nanocrystals with Different Particle Sizes." Journal of Nanoscience and Nanotechnology 20, no. 10 (October 1, 2020): 6469–74. http://dx.doi.org/10.1166/jnn.2020.18580.

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As one of the most prospective delivery systems of insoluble drugs, nanocrystal has attracted more and more attention from pharmaceutical researchers. Nanoparticles with prominent different particle diameters were obtained to solve the problem of solubility and evaluate the positive effects of quercetin in vitro. The newly prepared nanocrystals were investigated by several methods including dynamic light scattering (DLS) and transmission electron microscopy (TEM). The particle sizes of the quercetin nanocrystals A (quercetin/NCs-A), quercetin nanocrystals B (quercetin/NCs-B) and quercetin nanocrystals C (quercetin/NCs-C) were 3.089±0.162 μm, 677.2±9.7 nm and 169.8± 0.3 nm respectively. The crystalline state of quercetin was detected by X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) analyses and no change was observed after the process of reducing sizes. An accelerated quercetin dissolution rate was achieved through the nanocrystal technique. In conclusion, nanocrystals could significantly increase the equilibrium solubility of quercetin In Vitro. In addition, the particle size also had an important effect on the dissolution behavior of quercetin.

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Chen, Zhongjian, Wei Wu, and Yi Lu. "What is the future for nanocrystal-based drug-delivery systems?" Therapeutic Delivery 11, no. 4 (April 2020): 225–29. http://dx.doi.org/10.4155/tde-2020-0016.

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Nanocrystals are used as a drug-delivery platform for poorly water-soluble drugs and have had commercial success in oral drug delivery. We assert that the future of this technique is with cancer treatment and in the development of parenteral preparations. Advances in techniques for uniform and high-quality nanocrystals as well as deciphering the in vivo fate of nanocrystals are critical. The bottom-up technique allows for better control of particle properties, while the hybrid nanocrystal technique provides a novel approach to explore the in vivo fate of nanocrystals. Breakthroughs in these two techniques to further the development of nanocrystals are also discussed.

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Gutiérrez-Lazos, C. D., M. Ortega-López, E. Rosendo-Andrés, Y. Matsumoto-Kuwabara, V. Sánchez-Reséndiz, J. Morales-Corona, R. Olayo-González, E. Barrera-Calva, and T. Díaz-Becerril. "Highly Luminescent CdTe Nanocrystals Synthesized in Aqueous Solution and Self-Assembled on Polyelectrolyte Multilayers." Materials Science Forum 636-637 (January 2010): 374–79. http://dx.doi.org/10.4028/www.scientific.net/msf.636-637.374.

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CdTe nanocrystals have been synthesized in aqueous solution at 92oC under open-air conditions. During the reaction, aliquots of the samples were taken at different growth times and used to obtain their UV-Vis absorbance and photoluminescence spectra in order to estimate the nanocrystal size. The absorption peaks are located around 459 nm for 1 h, 478 nm for 2 h, 491 nm for 4 h, 532 nm for 7 h and 610 nm for 94 h of growth time. The mean nanocrystal size for these samples is 2 nm, 2.2 nm, 2.3 nm, 2.6 nm and 3.4 nm, respectively, according to the theoretical calculations of 1s1/2 – 1s3/2 excitonic transition. Finally, CdTe nanocrystals were assembled using layer-by-layer technique on glass substrates, using PDDA as cationic polyelectrolyte and negatively charged CdTe nanocrystals. The Raman spectroscopy shows that CdTe nanocrystals preserve the nanoparticle properties after being assembled.

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Dey, Pijush Ch, Sumit Sarkar, and Ratan Das. "X-ray diffraction study of the elastic properties of jagged spherical CdS nanocrystals." Materials Science-Poland 38, no. 2 (June 1, 2020): 271–78. http://dx.doi.org/10.2478/msp-2020-0032.

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AbstractIn this work, jagged spherical CdS nanocrystals have been synthesized by chemical method to study their elastic properties. The synthesized CdS nanocrystal has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The transmission electron microscope images show that the average size of the nanocrystal is 100 nm approximately. X-ray diffraction (XRD) study confirms that the CdS nanocrystals are in cubic zinc blende structure. The size calculated from the XRD is consistent with the average size obtained from the TEM analysis. The XRD data have been analyzed to study the elastic properties of the jagged spherical CdS nanocrystals, such as intrinsic strain, stress and energy density, using WilliamsonHall plot method. Williamson-Hall method and size-strain plot (SSP) have been used to study the individual effect of crystalline size and lattice strain on the peak broadening of the jagged spherical CdS nanocrystals. Size-strain plot (SSP) and root mean square (RMS) strain further confirm the results obtained from W-H plots.

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Yin, J. S., and Z. L. Wang. "Self-Assembled Cobalt Oxide Nanocrystals with Tetrahedral Shape." Microscopy and Microanalysis 4, S2 (July 1998): 736–37. http://dx.doi.org/10.1017/s1431927600023801.

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Nanocrystal materials are an emerging research field of chemistry, physics and materials science. The size and shape specificity of nanocrystals suggests them as building blocks for constructing selfassembly passivated nanocrystals superlattices (NCS's) or nanocrystals arrays (NCA) [1-6]. In this paper, NCAs of CoO with controlled tetrahedral shape are reported and their structural stability is examined by in-situ TEM.Cobalt oxide nanocrystals were synthesized by chemical decomposition of Co2(CO)8 in toluene under oxygen atmosphere, as given in detail elsewhere [1].Sodium bis(2-ethylhexyl) sulfosuccinate (Na(AOT)) was added as a surface active agent, forming an ordered monolayer passivation (called the thiolate) over the nanocrystal surface. The particle size was controlled by adjusting the wt.% ratio between the precursor and Na(AOT). The as-prepared solution contained Co, CoO and possibly C03O4 nanoparticles, and pure CoO nanoparticles were separated by applying a small magnetic field, which is generated by a horseshoe permanent magnet in vertical direction.

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Feng, Anni, Jiankang Cao, Junying Wei, Feng Chang, Yang Yang, and Zongyuan Xiao. "Facile Synthesis of Silver Nanoparticles with High Antibacterial Activity." Materials 11, no. 12 (December 8, 2018): 2498. http://dx.doi.org/10.3390/ma11122498.

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We report on a reverse microemulsion method for the synthesis of silver nanocrystals and examine their antibacterial activities. As the molar ratio of water to sodium bis(2-ethylhexyl) sulfosuccinate (AOT) increases to 25, a morphology transition from a sphere-like nanocrystal to a wire-like one was observed. For both the gram-negative and gram-positive bacteria, the wire-like silver nanocrystal showed higher antibacterial activities. We conclude that the morphology of silver nanocrystals dominates their antibacterial activity.

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Choi, Seong Jae, Dong Kee Yi, Jae-Young Choi, Jong-Bong Park, In-Yong Song, Eunjoo Jang, Joo In Lee, et al. "Spatial Control of Quantum Sized Nanocrystal Arrays onto Silicon Wafers." Journal of Nanoscience and Nanotechnology 7, no. 12 (December 1, 2007): 4285–93. http://dx.doi.org/10.1166/jnn.2007.884.

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Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates. We present both metal (Pd) and semiconductor (CdSe) nanocrystals arrayed in monolayer onto trenched silicon wafers (4 inch diameter) using a facile electrostatic adsorption scheme. In particular, CdSe nanocrystal arrays in the trench well showed superior luminescent efficiency compared to those onto the protruded trench flat, due to the densely arrayed CdSe nanocrystals in the vertical direction. Furthermore, the surface coverage controllability was investigated using a 2D silicon substrate. Our approach can be applied to generate highly efficient displays, memory chips and integrated sensing devices.

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A. Hussein, Ahmed, and Hasanain Sh. Mahmood. "Preparation and Evaluation of Cefixime Nanocrystals." Iraqi Journal of Pharmaceutical Sciences ( P-ISSN 1683 - 3597 E-ISSN 2521 - 3512) 23, no. 2 (March 27, 2017): 1–12. http://dx.doi.org/10.31351/vol23iss2pp1-12.

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Drug nanocrystals are nanoscopic crystals of the parent compound with dimensions less than 1 Âµm. A decrease in particle size will lead to an increase in effective surface area in the diffusion layer, which, in turn, increases the drug dissolution rate. Drug nanocrystals are one of the most important strategies to enhance the oral bioavailability of hydrophobic drugs. Cefixime is the first member of what is generally termed the third generation orally active cephalosporins. These third generation cephalosporins are distinct from the older Î²-lactam antibiotics in their intensive antibacterial activity against a wide range of gram-negative bacteria. The aim of this study is to prepare nanocrystals of cefixime as a capsules dosage form in order to increase its oral dissolution rate and bioavailability. The cefixime nanocrystals were prepared by solvent/antisolvent precipitation method. Certain amount of drug was dissolved in water miscible solvent (methanol used in this study), then this solution was injected (at certain speed) into water containing stabilizer. Upon injection, precipitation of cefixime nanocrystal will occur immediately; this precipitate is sonicated at 37 ËšC for 30 min. then lyophilized. Powder of nanocrystal was obtained and filled into capsules. The physicochemical interaction between drug and addatives was studied using FTIR, DSC, Results show that the best formula of cefixime nanocrystals prepared by dissolving 20mg/ml of cefixime in methanol, then 5ml was injected at 60ml/hr rate to a 50ml PVP solution as stabilizer in concentration 0.05%, then lyophilized to obtain the cefixime nanocrystal powder. The resulted mean particle size was 9-11 nm and the dissolution rate was significantly higher than that of the raw cefixime powder (p>0.05). Keywords: Cefixime trihydrate, Nanocrystals, Anti-solvent precipitation, PVP, HPMC, Poloxamer 188.

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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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Zhan, Li, Qi Wei, Geng Yanxia, Xu Junzheng, and Wu Wangsuo. "Biodistribution of60Co–Co/Graphitic-Shell NanocrystalsIn Vivo." Journal of Nanomaterials 2011 (2011): 1–5. http://dx.doi.org/10.1155/2011/842613.

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The magnetic nano-materials, Co/graphitic carbon- (GC-) shell nanocrystals, were madeviachemicalvapour deposition (CVD) method, and their biodistribution and excretion in mice were studied by using postintravenously (i.v.) injecting with60Co–Co/GC nanocrystals. The results showed that about 5% of Co was embedded into graphitic carbon to form multilayer Co/GC nanocrystals and the size of the particle was ~20 nm, the thickness of the nanocrystal cover layer was ~4 nm, and the core size of Co was ~14 nm. Most of the nanocrystals were accumulated in lung, liver, and spleen after 6, 12, 18, and 24 h afteri.v.with60Co–Co/GC nanocrystals. The nanoparticles were cleared rapidly from blood and closed to lower level in 10 min after injection. The60Co–Co/GC nanocrystals were eliminated slowly from body in 24 h after injection, ~6.09% of60Co–Co/GC nanocrystals were excreted by urine, ~1.85% by feces in 24 h, and the total excretion was less than 10%.

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Gao, Yukun, and PG Yin. "Synthesis of cubic CdSe nanocrystals and their spectral properties." Nanomaterials and Nanotechnology 7 (January 1, 2017): 184798041770174. http://dx.doi.org/10.1177/1847980417701747.

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The cadmium selenide nanocrystals are prepared by colloidal chemistry under mild conditions. X-ray diffraction and high-resolution transmission electron microscopy measurements indicate that as-prepared cadmium selenide nanocrystals are zinc blende cubic structure. We carry out an analysis of quantum size effect in the Raman spectra of cadmium selenide nanocrystals performed by utilizing the chemical bond theory of Raman peak shift developed recently. It is revealed that the shifts of Raman peaks in cadmium selenide nanocrystals result from the overlapping of the quantum effect shifts and surface effect shifts. The sizes of the as-prepared cadmium selenide nanocrystals obtained by employing the Raman peak shift theory are in good agreement with the nanocrystal sizes determined by high-resolution transmission electron microscopy.

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Della Gaspera, Enrico, Noel W. Duffy, Joel van Embden, Lynne Waddington, Laure Bourgeois, Jacek J. Jasieniak, and Anthony S. R. Chesman. "Plasmonic Ge-doped ZnO nanocrystals." Chemical Communications 51, no. 62 (2015): 12369–72. http://dx.doi.org/10.1039/c5cc02429c.

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Barzegar, Sedigheh, Mahmood Karimi Abdolmaleki, William B. Connick, and Ghodratollah Absalan. "Enhancing Vapochromic Properties of Platinum(II) Terpyridine Chloride Hexaflouro Phosphate in Terms of Sensitivity through Nanocrystalization for Fluorometric Detection of Acetonitrile Vapors." Crystals 14, no. 4 (April 5, 2024): 347. http://dx.doi.org/10.3390/cryst14040347.

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The vapochromic properties of [Pt(tpy)Cl](PF6) crystals in the presence of acetonitrile and its effect on the crystal structure as well as the fluorescence spectrum of this complex have already been studied in the past. We synthesized nanocrystals of this compound for the first time, and discussed different parameters and methods that affect nanocrystal structure modulation. The study demonstrates the vapochromic properties of the nanocrystals toward acetonitrile vapor by investigating the morphology and fluorescence spectra of the nanocrystals. Vapochromic studies were conducted on [Pt(tpy)Cl](PF6) nanocrystals for five cycles of absorption and desorption of acetonitrile, demonstrating shorter response times compared to regular bulk crystals.

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Bandari, Vineeth Kumar, Lakshmi Varadharajan, Longqian Xu, Abdur Rehman Jalil, Mirunalini Devarajulu, Pablo F. Siles, Feng Zhu, and Oliver G. Schmidt. "Charge transport in organic nanocrystal diodes based on rolled-up robust nanomembrane contacts." Beilstein Journal of Nanotechnology 8 (June 19, 2017): 1277–82. http://dx.doi.org/10.3762/bjnano.8.129.

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The investigation of charge transport in organic nanocrystals is essential to understand nanoscale physical properties of organic systems and the development of novel organic nanodevices. In this work, we fabricate organic nanocrystal diodes contacted by rolled-up robust nanomembranes. The organic nanocrystals consist of vanadyl phthalocyanine and copper hexadecafluorophthalocyanine heterojunctions. The temperature dependent charge transport through organic nanocrystals was investigated to reveal the transport properties of ohmic and space-charge-limited current under different conditions, for instance, temperature and bias.

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Wang, Li, Hong Fang Sun, Hui Hua Zhou, and Jing Zhu. "Self-Assembly Growth and Size Control of Silver Nanocrystals for Nonvolatile Memory Applications." Materials Science Forum 610-613 (January 2009): 585–90. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.585.

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A film with a single-layer of size controlled silver nanocrystals embedded in silicon dioxide (SiO2) dielectric film by magnetic sputtering has been fabricated for nonvolatile memory applications. The effects of sputtering power, deposition time and substrate temperature on Ag nanocrystals formation were investigated. Transmission electron microscopy (TEM) images showed the as-prepared Ag nanocrystals had high uniformity in their size and distribution. The relationship between Ag nanocrystal size, density and electron storage capability as well as date retention time has been discussed.

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Xiong, Zichang, Himashi P. Andaraarachchi, Jacob T. Held, Rick W. Dorn, Yong-Jin Jeong, Aaron Rossini, and Uwe R. Kortshagen. "Inductively Coupled Nonthermal Plasma Synthesis of Size-Controlled γ-Al2O3 Nanocrystals." Nanomaterials 13, no. 10 (May 12, 2023): 1627. http://dx.doi.org/10.3390/nano13101627.

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Gamma alumina (γ-Al2O3) is widely used as a catalyst and catalytic support due to its high specific surface area and porosity. However, synthesis of γ-Al2O3 nanocrystals is often a complicated process requiring high temperatures or additional post-synthetic steps. Here, we report a single-step synthesis of size-controlled and monodisperse, facetted γ-Al2O3 nanocrystals in an inductively coupled nonthermal plasma reactor using trimethylaluminum and oxygen as precursors. Under optimized conditions, we observed phase-pure, cuboctahedral γ-Al2O3 nanocrystals with defined surface facets. Nuclear magnetic resonance studies revealed that nanocrystal surfaces are populated with AlO6, AlO5 and AlO4 units with clusters of hydroxyl groups. Nanocrystal size tuning was achieved by varying the total reactor pressure yielding particles as small as 3.5 nm, below the predicted thermodynamic stability limit for γ-Al2O3.

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Tsybeskov, Leonid. "(Invited, Digital Presentation) Photoluminescence in PbS Nanocrystal Thin Films: Manifestation of Energy Transfer." ECS Meeting Abstracts MA2022-01, no. 20 (July 7, 2022): 1105. http://dx.doi.org/10.1149/ma2022-01201105mtgabs.

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It is widely accepted that photoluminescence (PL) properties of colloidal nanocrystals, specifically PbS, are mainly determined by their composition, size, and shape. In this work, we demonstrated that in densely packed PbS nanocrystal films, low-temperature donor-to-acceptor energy transfer is mainly responsible for the PL spectra narrowing and shift toward longer wavelengths. At elevated temperatures, back energy transfer seems to be responsible for an unusual PL intensity temperature dependence and spectra modifications. A reduction of the PbS nanocrystal density, i.e., an increase of a distance separating the nanocrystals, dramatically reduces the effect, and the PL spectra are entirely governed by the nanocrystal size and size distribution.

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Sun, Lin, Hong Xiang, Canfeng Ge, Xingxu Chen, Qian Zhang, Yanzhuo Zhang, and Xiaoqing Miao. "A Nanocrystals-Based Topical Drug Delivery System with Improved Dermal Penetration and Enhanced Treatment of Skin Diseases." Journal of Biomedical Nanotechnology 17, no. 12 (December 1, 2021): 2319–37. http://dx.doi.org/10.1166/jbn.2021.3202.

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Topical drug delivery methods are important in the treatment of skin diseases. Drug nanocrystals, which are nanometersized particles of active pharmaceutical ingredients, offer efficient topical delivery with high stability, high drug loading capacity, steady dissolution, and sustained drug release profiles. The use of nanocrystals for the topical delivery of skin disease therapies is currently being evaluated; this review focuses on how nanocrystals facilitate active pharmaceutical ingredient transport across skin barriers, exploring the underlying transportation mechanisms of the nanocrystals and active pharmaceutical ingredient molecules to the dermal and epidermal skin cells. In topical delivery, previous skin treatments, choice of excipients and vehicles, and penetration enhancement strategies critically influence the topical delivery of drug nanocrystals. Various research and applications of drug nanocrystals in skin disease therapy are highlighted in this review, and intellectual property protection for drug nanocrystal formulations, clinical trial data, and products with commercial potential are also discussed.

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Paul Alivisatos, A., Hoduk Cho, and Jungwon Park. "Spiers Memorial Lecture : New tools for observing the growth and assembly of colloidal inorganic nanocrystals." Faraday Discussions 181 (2015): 15–18. http://dx.doi.org/10.1039/c5fd90056e.

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We present two examples of the use of liquid cells to study colloidal inorganic nanocrystals using in situ transmission electron microscopy. The first uses a liquid cell to quantify the interaction potential between pairs of colloidal nanocrystals, and the second demonstrates direct imaging of nanocrystal growth and structure in the liquid cell.

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YıImaz, D. E., C. Bulutay, and T. Çagın. "Atomistic Structure Simulation of Silicon Nanocrystals Driven with Suboxide Penalty Energies." Journal of Nanoscience and Nanotechnology 8, no. 2 (February 1, 2008): 635–39. http://dx.doi.org/10.1166/jnn.2008.a117.

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The structural control of silicon nanocrystals embedded in amorphous oxide is currently an important technological problem. In this work, an approach is presented to simulate the structural behavior of silicon nanocrystals embedded in amorphous oxide matrix based on simple valence force fields as described by Keating-type potentials. After generating an amorphous silicon-rich-oxide, its evolution towards an embedded nanocrystal is driven by the oxygen diffusion process implemented in the form of a Metropolis algorithm based on the suboxide penalty energies. However, it is observed that such an approach cannot satisfactorily reproduce the shape of annealed nanocrystals. As a remedy, the asphericity and surface-to-volume minimization constraints are imposed. With the aid of such a multilevel approach, realistic-sized silicon nanocrystals can be simulated. Prediction for the nanocrystal size at a chosen oxygen molar fraction matches reasonably well with the experimental data when the interface region is also accounted. The necessity for additional shape constraints suggests the use of more involved force fields including long-range forces as well as accommodating different chemical environments such as the double bonds.

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He, Yizhou, Liyifei Xu, Cheng Yang, Xiaowei Guo, and Shaorong Li. "Design and Numerical Investigation of a Lead-Free Inorganic Layered Double Perovskite Cs4CuSb2Cl12 Nanocrystal Solar Cell by SCAPS-1D." Nanomaterials 11, no. 9 (September 7, 2021): 2321. http://dx.doi.org/10.3390/nano11092321.

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In the last decade, perovskite solar cells have made a quantum leap in performance with the efficiency increasing from 3.8% to 25%. However, commercial perovskite solar cells have faced a major impediment due to toxicity and stability issues. Therefore, lead-free inorganic perovskites have been investigated in order to find substitute perovskites which can provide a high efficiency similar to lead-based perovskites. In recent studies, as a kind of lead-free inorganic perovskite material, Cs4CuSb2Cl12 has been demonstrated to possess impressive photoelectric properties and excellent environmental stability. Moreover, Cs4CuSb2Cl12 nanocrystals have smaller effective photo-generated carrier masses than bulk Cs4CuSb2Cl12, which provides excellent carrier mobility. To date, there have been no reports about Cs4CuSb2Cl12 nanocrystals used for making solar cells. To explore the potential of Cs4CuSb2Cl12 nanocrystal solar cells, we propose a lead-free perovskite solar cell with the configuration of FTO/ETL/Cs4CuSb2Cl12 nanocrystals/HTL/Au using a solar cell capacitance simulator. Moreover, we numerically investigate the factors that affect the performance of the Cs4CuSb2Cl12 nanocrystal solar cell with the aim of enhancing its performance. By selecting the appropriate hole transport material, electron transport material, thickness of the absorber layer, doping density, defect density in the absorber, interface defect density, and working temperature point, we predict that the Cs4CuSb2Cl12 nanocrystal solar cell with the FTO/TiO2/Cs4CuSb2Cl12 nanocrystals/Cu2O/Au structure can attain a power conversion efficiency of 23.07% at 300 K. Our analysis indicates that Cs4CuSb2Cl12 nanocrystals have great potential as an absorbing layer towards highly efficient lead-free all-inorganic perovskite solar cells.

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Dong, Cong. "The Silver Ion and Nanocrystalline Pattern in the Glass Substrate, the Electric Field-Induced Thermal Transfer and Ink Absorption Layer Structure and Printing Performance." Advances in Materials Science and Engineering 2022 (August 11, 2022): 1–10. http://dx.doi.org/10.1155/2022/4272294.

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People’s research on nanocrystals is getting more in-depth with the development of science and technology, and the patterned arrangement of nanocrystals can greatly improve the performance of our equipment in related fields, allowing people to control the patterning of nanocrystals. Research on thermal transfer is also increasing. Glass materials doped with patterned metal nanocrystals have great application potential, and the search for a simple and efficient patterned preparation method has attracted great attention of many researchers. Using the directional induced migration effect of the high temperature and high voltage DC electric field, combined with the subsequent heat treatment process, the distribution of silver nanocrystals corresponding to the surface silver film pattern can be formed in the silicate glass substrate, to realize the electric field-induced thermal transfer of the nanocrystal pattern print. This article aims to study the patterned thermal transfer of silver ions and nanocrystals on the glass substrate by applying an electric field to induce and analyze the ink absorption layer structure and printing performance. On this basis, an electron beam-induced thermal transfer method and Maxwell’s equation are proposed to investigate and calculate the structure of the ink absorption layer. The experimental structure shows that using this method increases the success rate of the preparation of silver ions and nanocrystal patterns on the glass substrate by 30%, which improves the ink absorption layer and printing performance to different degrees.

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Harfenist, S. A., Z. L. Wang, T. G. Schaaff, and R. L. Whettent. "A BCC Superlattice of Passivated Gold Nanocrystals." Microscopy and Microanalysis 4, S2 (July 1998): 716–17. http://dx.doi.org/10.1017/s1431927600023709.

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A recent development in the study of nanocrystalline materials has been the self-assembly of passivated nanometer scale building blocks into larger, well ordered structures reaching the micron scale. Nanocrystal supercrystals (NCS) have been observed in metallic, semiconductor, and magnetic materials. In most cases the nanocrystals (NXs) are encapsulated in some inert medium that effectively protects the nanocrystal core and its unique electronic and optical properties. Here we describe the self-assembly of gold nanocrystals (∼4.5 nm core diameter), passivated with hexanethiol self-assembled-monolayers into ordered regions exhibiting a body-centered-cubic (bcc) superstructure. Transmission Electron Microscopy (TEM) imaging and Electron Diffraction (ED) experiments were used to characterize the NCSs and their resulting superstructures.A large agglomeration of NCSs can be seen in figure 1. One can clearly see regions of periodicity within the nanocrystal aggregation.

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Dâna, Aykutlu, Imran Akca, Atilla Aydinli, Rasit Turan, and Terje G. Finstad. "A Figure of Merit for Optimization of Nanocrystal Flash Memory Design." Journal of Nanoscience and Nanotechnology 8, no. 2 (February 1, 2008): 510–17. http://dx.doi.org/10.1166/jnn.2008.a156.

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Nanocrystals can be used as storage media for carriers in flash memories. The performance of a nanocrystal flash memory depends critically on the choice of nanocrystal size and density as well as on the choice of tunnel dielectric properties. The performance of a nanocrystal memory device can be expressed in terms of write/erase speed, carrier retention time and cycling durability. We present a model that describes the charge/discharge dynamics of nanocrystal flash memories and calculate the effect of nanocrystal, gate, tunnel dielectric and substrate properties on device performance. The model assumes charge storage in quantized energy levels of nanocrystals. Effect of temperature is included implicitly in the model through perturbation of the substrate minority carrier concentration and Fermi level. Because a large number of variables affect these performance measures, in order to compare various designs, a figure of merit that measures the device performance in terms of design parameters is defined as a function of write/erase/discharge times which are calculated using the theoretical model. The effects of nanocrystal size and density, gate work function, substrate doping, control and tunnel dielectric properties and device geometry on the device performance are evaluated through the figure of merit. Experimental data showing agreement of the theoretical model with the measurement results are presented for devices that has PECVD grown germanium nanocrystals as the storage media.

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Liu, Lin, Xiaogang Yang, Houyong Yu, Chao Ma, and Juming Yao. "Biomimicking the structure of silk fibers via cellulose nanocrystal as β-sheet crystallite." RSC Adv. 4, no. 27 (2014): 14304–13. http://dx.doi.org/10.1039/c4ra01284d.

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Biomimic silk fibers with refined crystalline structure were produced via incorporating cellulose nanocrystals into silk fibroin matrix to mimic the β-sheet crystallites in natural silk. The fibers exhibit excellent thermal and mechanical properties, attributed to the strong hydrogen bonding interactions between cellulose nanocrystals and silk fibroin as well as cellulose nanocrystal-induced ordered structure.

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Maksimchuk, P. O., A. A. Masalov, V. V. Seminko, O. G. Viagin, V. K. Klochkov, and Yu V. Malyukin. "Abnormal Low Linewidth Temperature Broadening Observed for YVO4:Eu Nanocrystals." Ukrainian Journal of Physics 57, no. 2 (February 15, 2012): 193. http://dx.doi.org/10.15407/ujpe57.2.193.

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Since the temperature broadening of spectral lines is determined by the phonon scattering by impurity centers, a modification of the phonon spectrum can affect the temperature broadening suppression. So, by controlling the nanocrystal size, the effect of "cluster freezing", namely, the abnormal temperature broadening of weak spectral lines up to room temperature, can be achieved. The spectral lines of impurity ions in YVO4:Eu3+ nanocrystals remain abnormally narrow (10 cm–1) even at room temperature, whereas, for the bulk crystals, the average linewidth at room temperature is 70 cm–1. This narrowness of spectral lines can be clearly explained by the manifestation of the phonon spectrum depletion in nanocrystals. The temperature dependences of linewidths obtained for nanocrystals with various sizes exhibit the strong dependence of the spectral line width on the sizes of a nanocrystal and differ from those for a bulk crystal.

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Ding, Yong Ling, Hua Dong Sun, Kang Ning Sun, and Fu Tian Liu. "Water-Based Route to Synthesis of High-Quality UV-Blue Photoluminescing ZnSe/ZnS Core/Shell Quantum Dots and their Physicochemical Characterization." Key Engineering Materials 680 (February 2016): 553–57. http://dx.doi.org/10.4028/www.scientific.net/kem.680.553.

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Epitaxially overgrowing a semiconductor material with higher bandgap around the QDs has proven to be a crucial approach for improving the PL efficiency and stability of nanocrystals. In this paper, a ZnS shell was deposited around ZnSe nanocrystal cores via a noninjection approach in aqueous media. The deposition procedure conducted at 100°C in a reaction flask in the presence of the shell precursor compounds, together with the crude ZnSe nanocrystal cores and the thiol ligand glutathione. The influences of various experimental variables, including the reaction time, amount of thiourea, as well as pH value, on the growth rate and luminescent properties of the obtained core/shell nanocrystals have been systematically investigated. In comparison with the original ZnSe nanocrystals, the PL efficiency of the obtained ZnSe/ZnS core/shell nanostructures can be improved significantly with a QY up to 62.8%.

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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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Journal articles on the topic 'Nanocrystals'

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