共查询到20条相似文献,搜索用时 31 毫秒
1.
During CdSe nanocrystal growth, loss of surface capping molecules occurs leading to a decrease of photoluminescence (PL) quantum yield. In general, aliphatic capping molecules are applied to passivate the surface of CdSe nanocrystals to modulate the optical properties of the CdSe. In this work, two kinds of alkylamine (n-butylamine (n-BA) and n-hexylamine (n-HA)) and oleic acid (OA) were used to modify the surfaces of the CdSe nanocrystals. From the PL spectra and quantum yield analyses, we observed that the PL emission peak positions of the modified CdSe nanocrystals have blue shifted for all three capping molecules. However, the PL quantum yield of the CdSe nanocrystals increased after introduction of the alkylamine molecules, but decreased with oleic acid. The detailed mechanism was not clear until now. In this study, a density function theory (DFT) simulation was employed to demonstrate binding energy and charge analyses of CdSe with n-BA, n-HA and OA. By comparing the binding energy of the bare CdSe nanocrystals to that of the CdSe with the capping molecules, it was shown that n-BA and n-HA as capping molecules help to increase the charge on Se and decrease it on cadmium of the CdSe. 相似文献
2.
3.
Yu Zhang Quanqin Dai Xinbi Li Qingzhou Cui Zhiyong Gu Bo Zou Yiding Wang William W Yu 《Nanoscale research letters》2010,5(8):1279-1283
PbSe/CdSe core/shell nanocrystals with quantum yield of 70% were obtained by the “successive ion layer adsorption and reaction”
technology in solution. The thickness of the CdSe shell was exactly controlled. A series of spectral red shifts with the CdSe
shell growth were observed, which was attributed to the combined effect of the surface polarization and the expansion of carriers’
wavefunctions. The stability of PbSe nanocrystals was tremendously improved with CdSe shells. 相似文献
4.
The growth of CdSe quantum dots on a single wall carbon nanotubes template without organic solvent and surfactant 总被引:1,自引:0,他引:1
A conventional synthesis of Cadmium selenide (CdSe) quantum dots (QDs) usually employs toxic organic solvents, and the synthesized CdSe QDs must be modified for dispersion in an aqueous solution. This modification often limits the application of CdSe QDs in biomedical fields. In this study, a simple method was developed to synthesize CdSe QDs on single wall carbon nanotubes (SWCNTs) employing the SWCNTs as a template to prevent the aggregation of the CdSe QDs in an aqueous solution without the addition of any organic reagent.Our newly developed synthetic procedure included the formation of SWCNTs with carboxyl groups (SWCNT-COOHs) followed by mixing these with the precursors of Cd and Se to obtain SWCNT-CdSe QDs. The resulting SWCNT-CdSe QDs were analyzed using spectrophotometry, transmission electron microscopy (TEM) and X-ray diffraction (XRD).Results showed that CdSe nanocrystals with a zinc blend structure could be synthesized on the SWCNT-COOHs. The average crystal size of the synthesized CdSe QDs was approximately 3 nm. The blue-shift of CdSe QDs powerfully emitted light at 550 nm as compared to the bulk CdSe at 730 nm. These CdSe QDs were synthesized in an aqueous environment without using toxic surfactants and are expected to have great potential as bio-labeling contrast agents in the future. 相似文献
5.
CdS/CdSe核壳结构半导体纳米晶结构及光谱特性 总被引:1,自引:0,他引:1
采用共沉淀法在水相中将CdS外延生长于CdSe半导体纳米晶(CdSe NCs)表面,制备了结晶形态较好的CdSc/CdS核壳结构半导体纳米晶(CdSe/CdS C/S NCs),并改善了CdSe NCs的荧光性能.通过X射线衍射,透射电镜和选区电子衍射分析证明了核壳结构的形成,并通过紫外可见光吸收光谱和荧光光谱分析证明了核壳结构对CdSe NCs荧光性能的改善.此外,实验结果表明:控制CdSe核合成中Cd前驱体溶液pH值能获得粒径分布较窄的CdSe/CdS C/S NCs;采用不同浓度比的Cd和Se前驱体溶液可以有效调节核壳结构半导体纳米晶的粒径;选择合适的CdSe与CdS摩尔比及壳层中Cd与S摩尔比能改善CdSe/CdS C/S NCs的荧光性能. 相似文献
6.
Gary Hodes 《Israel journal of chemistry》1993,33(1):95-106
This paper is a review of our work on nanocrystalline semiconductor films which exhibit pronounced size quantization effects in three dimensions, manifested by large blue-shifts in their optical absorption spectra. The films are prepared by either chemical solution deposition (CdSe and PbSe) or by electrodeposition from nonaqueous electrolytes (CdSe and CdS). Except for PbSe, where the nanocrystals are surrounded by a matrix, the films are comprised of aggregated nanocrystals. Crystal size (typically from <4 nm to >6 nm), and therefore absorption spectra, can be controlled by deposition temperature, illumination during deposition (for chemically deposited films), solution composition, and post annealing. The crystal size dependence of chemically-deposited films on experimental parameters (temperature, illumination, reactant concentrations) is discussed. CdSe nanocrystals were epitaxially electrodeposited on single-crystal Au. The nanocrystal distribution (isolated or aggregated) could be controlled by deposition current and temperature. All these films exhibit photoelectrochemical behavior but no corresponding solid state photovoltaic behavior. A model is proposed based on electron/hole separation by kinetic differences in charge injection into an electrolyte rather than by a built-in space charge layer in the semiconductor. The films can behave as both ‘n’ - or ‘p’-type, with respect to direction of photocurrent flow, by changes in the semiconductor surface properties and/or the electrolyte, in agreement with this model. 相似文献
7.
Younghun Sung Jaehoon Lim Jai Hyun Koh Byoung Koun Min Jeffrey Pyun Kookheon Char 《Korean Journal of Chemical Engineering》2016,33(8):2287-2290
Pt-decorated CdSe tetrapods with different arm lengths were tested for the photocatalytic hydrogen generation reaction. Well-defined CdSe tetrapods with controlled wurtzite arm lengths were synthesized by the continuous precursor injection (CPI) approach. Pt nanocrystals with an extremely small size of ~1 nm were directly decorated on the overall surfaces of CdSe tetrapods. Ligand-exchanged Pt-decorated CdSe tetrapods with different arm lengths were employed as photocatalysts for photocatalytic hydrogen generation reaction in the presence of hole scavengers. Pt-decorated CdSe tetrapods with shorter arm length showed the highest photocatalytic efficiency, which is due to higher probability of charge separation. 相似文献
8.
ZnO/CdSe core-shell nanorod array films were synthesized via a two-step method. ZnO nanorod array films were first grown on a TCO substrate, and then CdSe nanocrystals were deposited on the nanorods to form core-shell structured films. The resulting films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. Especially, dark-field images and transmission electron diffraction of the TEM were used to study the morphology and the chemical nanostructure of the ZnO/CdSe core-shell nanorods in detail. We investigated the photovoltaic performance of the resulting ZnO/CdSe core-shell nanorod array films as solar cell photoanodes. Parameters, such as the length of the ZnO nanorods, the shell phase structure and the deposition time of the CdSe nanocrystals were found to affect the photovoltaic performance of the solar cell. This study provides a facile method to prepare nanocomposite photoanodes of solar cells, and gives some insight about the fundamental mechanisms that improve the performance. 相似文献
9.
Pengfei Hu Dianzeng Jia Yali Cao Yudai Huang Lang Liu Jianmin Luo 《Nanoscale research letters》2009,4(5):437-443
With air-stable and generic reagents, CdSe nanocrystals with tunable morphologies were prepared by controlling the temperature
in the solution reaction route. Thereinto, the lower reaction temperature facilitates the anisotropic growth of crystals to
obtain high-yield CdSe ring- and tribulus-shaped nanocrystals with many branches on their surfaces. The photoluminescence
properties are sensitive to the nature of particle and its surface. The products synthesized at room temperature, whose surfaces
have many branches, show higher blue shift and narrower emission linewidths (FWHM) of photoluminescence than that of samples
prepared at higher temperature, whose surfaces have no branches. Microstructural studies revealed that the products formed
through self-assembly of primary crystallites. Nanorings formed through the nonlinear attachment of primary crystallites,
and the branches on the surfaces grew by linear attachment at room temperature. And the structure of tribulus-shaped nanoparticle
was realized via two steps of aggregation, i.e., random and linear oriented aggregation. Along with the elevation of temperature,
the branches on nanocrystal surfaces shortened gradually because of the weakened linear attachment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Although nanocrystals have several advantages of tunable bandgap and high carrier mobility, it is still challenging to achieve high‐performance polymer: nanocrystals hybrid solar cells (HSC) due to the complicated surface problem. Many efforts have been devoted to replace the long alkyl chain on the surface of nanocrystals to improve the charge transfer and transport. Herein, we modified the alkyl chain in poly[2,6–(4,4‐bis (2‐ethylhexyl)?4H‐cyclopenta[2,1‐b;3,4‐b′]‐dithiophene)‐alt ‐4,7–(2,1,3‐benzothiadiazole)] (PCPDTBT) by phosphate ester. Due to its strong affinity to CdSe nanocrystals, the resulting polymers can spontaneously exchange the long chain ligands in one‐step process. With the improved morphology of polymer: CdSe blended film, a power conversion efficiency (PCE) of 3.12% was achieved for hybrid solar cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45003. 相似文献
11.
12.
13.
A simple hard template method has been developed to prepare uniform matchstick-like PbS nanocrystals. The approach combines functionalization of the mesoporous walls and channel surface with thioether groups, adsorption of Pb2+, and heating in an N2 atmosphere at high temperature. The structure, morphology and composition of the nanocrystals have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The optical properties of the matchstick-like PbS nanocrystals have been systematically investigated by Raman spectroscopy, UV-visible absorption spectroscopy (UV-vis), and photoluminescence spectroscopy (PL). These results demonstrate that these matchstick-like PbS nanocrystals are single crystals and possess novel optical properties, suggesting that they may have many potential applications. A large blue shift is observed in the photoluminescence spectrum, and this clearly shows the quantum size effects of the matchstick-like PbS . Furthermore, a growth mechanism of the PbS heteronanostructure is proposed. 相似文献
14.
《Ceramics International》2022,48(8):11209-11214
transparent chalcogenide glass ceramics (ChGCs) based on a binary germanium-sulfur (Ge–S, GS) chalcogenide system were synthesized by heat treatment method. Compared with the precursor glass, the GS ChGCs embedded with GeS2 nanocrystals have the same infrared transparency, but smaller optical bandgap energy and higher mechanical strength. Z-scan measurements show that third-order optical nonlinearity in the GS ChGCs was remarkably enhanced, and this material would be suitable for applications in optical limiting. 相似文献
15.
16.
Synthesis and Characterization of Cadmium Selenide Nanorods Via Surfactant-Assisted Hydrothermal Method 总被引:1,自引:0,他引:1
Single-crystal CdSe nanorods ([001] orientation) with diameters in the range of 40–60 nm and aspect ratios of 5–8 were successfully synthesized at 180°C for 10 h through a facile surfactant-assisted hydrothermal method, using Na2 SeO3 as a high-quality soluble selenium source. The products were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and ultraviolet–vis spectra analysis. It was found that the surfactant (cetyltrimethyl ammonium bromide) played a vital role in the process. Through varying the concentrations of surfactant, the morphologies changed from dendrite-like nanostructure to nanorods, short nanorods, and nanoparticles. The possible mechanism for the growth of CdSe nanocrystals was also discussed. 相似文献
17.
Nguyen Tam Nguyen Truong Matthew Lowell Monroe Umme Farva Timothy James Anderson Chinho Park 《Korean Journal of Chemical Engineering》2011,28(7):1625-1631
Bulk hetero-junction solar cells with CdSe nanoparticles-P3HT (poly 3-hexyl thiophene) composite active layer were fabricated, and the control of morphological feature of the nanoparticle-polymer
composite thin films was investigated. A binary solvent composed of a primary solvent with intermediate polarity and a secondary
solvent with high polarity was found to be effective in controlling the dispersion of the CdSe nanocrystals in the P3HT matrix, and the modification of the nanocrystal surface by liquid-liquid extraction process was found to be effective in
achieving the desired composite film morphology. Surface roughness of the active layer was optimized for various loadings
of CdSe nanoparticles and could be reproducibly controlled to less than 10 nm. 相似文献
18.
Petchsang N Shapoval L Vietmeyer F Yu Y Hodak JH Tang IM Kosel TH Kuno M 《Nanoscale》2011,3(8):3145-3151
High quality ZnSe nanowires (NWs) and complementary ZnSe/CdSe core/shell species have been synthesized using a recently developed solution-liquid-solid (SLS) growth technique. In particular, bismuth salts as opposed to pre-synthesized Bi or Au/Bi nanoparticles have been used to grow NWs at low temperatures in solution. Resulting wires are characterized using transmission electron microscopy and possess mean ensemble diameters between 15 and 28 nm with accompanying lengths ranging from 4-10 μm. Subsequent solution-based overcoating chemistry results in ZnSe wires covered with CdSe nanocrystals. By varying the shell's growth time, different thicknesses can be obtained and range from 8 to 21 nm. More interestingly, the mean constituent CdSe nanocrystal diameter can be varied and results in size-dependent shell emission spectra. 相似文献
19.
以六方相CdS纳米线为前驱物,在不同浓度的Na2SeSO3水溶液中,采用水热合成法制备了负载量可控的CdSe沉积的CdS纳米线复合材料。采用XRD、SEM、TEM、UV-vis、PL和FTIR对该复合材料的物相、组成、形貌及光学性能进行了详细表征。结果表明,CdSe呈纤锌矿型六方相结构的纳米层形态沉积在CdS表面,其负载量受Na2SeSO3水溶液浓度、反应温度和反应时间控制;与CdS纳米线相比,纳米复合材料的可见光吸收范围明显扩大,覆盖了可见光的大部分区域,而其中的CdS纳米线荧光因CdSe的存在出现猝灭现象,同样,也未观察到CdSe的荧光。该文详细讨论了相关的光学性质以及纳米复合物的反应机理。 相似文献
20.
《Polymer Composites》2017,38(4):749-758
It is valuable to understand the way the wettability is affected by the solid and the liquid surface free energies. For this study, transparent films of CdSe/ZnS/PVC nanocomposites have been prepared and characterized by FTIR and contact angle measurements. Moreover, the presence of polar interactions at the liquid/polymer interfaces, which show a proportionality to the polar components of the liquid surface energy for pure polyvinyl chloride (PVC) and all CdSe/ZnS/PVC nanocomposites, is also studied. By using the surface polarizability hypothesis, there is possibility to obtain the dispersion component of surface‐free energies of pure PVC and also its nanocomposites from the contact angles measurement of only polar liquids. This approximately is coincident with that published data for pure PVC obtained from both polar and nonpolar liquids' contact angles. In addition to this, the absorption spectra and the photoluminescence illustrate clearly the effect of CdSe/ZnS quantum dots on their host matrix. The calculated values of the optical parameters, such as energy gap and Urbach energy, illustrate an inverse proportionality between them. POLYM. COMPOS., 38:749–758, 2017. © 2015 Society of Plastics Engineers 相似文献