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1.
A. E. Raevskaya A. L. Stroyuk S. Ya. Kuchmii 《Theoretical and Experimental Chemistry》2006,42(2):113-118
A study was carried out on the features of formation of stable aqueous colloidal solutions containing CdSe nanoparticles stabilized
by sodium polyphosphate resulting from a reaction between cadmium chloride and sodium selenosulfate. The major parameters
determining the size of the CdSe nanoparticles are the reaction medium temperature and the ratio of the starting reagent concentrations.
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Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 102–106, March–April, 2006. 相似文献
2.
Aneeta Kharkwal Shailesh N. Sharma S. Chand A. K. Singh 《Colloid and polymer science》2012,290(1):49-61
In this work, zinc oxide (ZnO) nanoparticles (size <10 nm) were formed via precipitation in ethanolic solution. The zinc acetate
and lithium hydroxide solutions in ethanol were mixed at 273 K temperatures under vigorous stirring. To study the effect of
quantum dot (QD) coverage, we have prepared a colloidal suspension of capped CdSe QDs (size ~5 nm) by chemical route and anchored
them to a nanoporous ZnO layer either by direct adsorption or through linker. Here a bifunctional molecule (mercaptopropionic
acid, MPA, and thioglycolic acid, TGA) was previously adsorbed on the ZnO surface, which acted as a molecular cable. From
TEM/SEM studies, it was observed that direct adsorption of CdSe QDs onto ZnO surface was not efficient. However, the bifunctional
linker molecules particularly MPA facilitates binding of CdSe QDs to ZnO; and consequently, interparticle electron transfer
is thus facilitated. The use of MPA linker despite of its long carbon chain also aids in the quenching of photoluminescence
of CdSe on addition of ZnO in a more systematic manner indicating efficient charge transfer from CdSe into ZnO as compared
with the without linker and with linker TGA case, respectively. Due to higher PL quenching and reduction in lifetime values,
higher values of Stern–Volmer quenching constants were thus obtained for CdSe–ZnO composites with MPA as compared with TGA
linker and without linker case, respectively. Nonlinear Stern–Volmer plots as observed for samples without linker case indicated
heterogeneous quenching due to insufficient binding between CdSe QDs and ZnO. By means of spectroscopic (PL, UV–VIS, FTIR)
and microscopic (TEM, SEM) techniques, we have demonstrated linker-dependent photosensitization mechanism of ZnO layers with
CdSe QDs. Our data thus illustrate that interfacial-electron transfer kinetics in QD–linker–ZnO assemblies are almost independent
of the length of alkyl-containing molecular linkers. 相似文献
3.
Himani Sharma Shailesh N. Sharma Gurmeet Singh Sonnada Math Shivaprasad 《Colloid and polymer science》2007,285(11):1213-1227
In this work, the role of conducting [poly (p-phenylinevinylene) (PPV)] and nonconducting (polystyrene) polymers on the properties
of their respective composites with CdSe quantum dots of varied sizes has been investigated. The emission and structural properties
of polymer–CdSe composites are found to be dependent on the crystallite size and morphology of CdSe nanocrystallites. Smaller
CdSe quantum dots (size, ∼5 nm) ensures efficient charge transfer process across polymer–CdSe interface as evident by almost
complete quenching of photoluminescence (PL) emission as compared to larger CdSe quantum dots (size, ∼7 nm). Presence of residual
trioctylphosphine (TOP)/ tri-n-octylphosphine-oxide (TOPO) species and agglomeration of particles act as a hindrance for quenching of emission and hence
charge transfer for larger CdSe nanocrystallites. Emission studies indicated an increased conjugation length for PPV polymers
in different solvents (toluene, pyridine) and in solid state. Nonconducting polymer polystyrene shows charge transfer across
polymer–CdSe interface as well. However, polystyrene polymer has a shorter chain length, which ensures maximum coverage on
the surface of CdSe nanocrystallites and provides better photostability to CdSe QDs within the polymer matrix as compared
to that for PPV–CdSe nanocomposites. 相似文献
4.
Umesh Kumar Kusum Kumari Shailesh N. Sharma Mahesh Kumar V. D. Vankar Rita Kakkar Vikram Kumar 《Colloid and polymer science》2010,288(8):841-849
In this work, tri-octyl phosphine/tri-octyl phosphine oxide (TOPO)-capped cadmium selenide (CdSe) quantum dots (QDs) of varied
sizes (5–9 nm), prepared by varying the input Cd:Se precursor ratio using chemical route, were dispersed in conducting polymer
matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT). By
using a binary solvent mixture (pyridine–chloroform), homogeneous dispersion of CdSe nanocrystals in polymers (MEH-PPV, P3HT)
could be realized. The properties of the resulting dispersions could be tailored by the composition and concentration of QDs
in polymer. The emission and structural properties of polymer–CdSe nanocomposites are found to be dependent on the crystallite
size and morphology of CdSe nanocrystallites. An effective quenching of photoluminescence emission in the polymer nanocomposite
was observed for smaller CdSe quantum dots (size ∼6 nm) as compared to larger CdSe quantum dots (size ∼9 nm), thus ensuring
efficient charge transfer process across the polymer–CdSe interface in the former case. The incomplete quenching, particularly
for MEH-PPV:CdSe nanocomposites, could be as a result of insufficient coverage of polymers on the surface of CdSe nanocrystallites,
mainly due to phase segregation for TOPO-stripped CdSe nanocrystallites. The superior morphology and optical properties of
polymer nanocomposite (P3HT:CdSe QDs) could play a pivotal role for the realization of effective charge separation and transport
in hybrid solar cells. 相似文献
5.
A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe 总被引:1,自引:0,他引:1
In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO2-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as
the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead
of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO2 composite nanoparticles with a SiO2 surface coating. Our results showed that CdSe/ZnS/SiO2 composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive
characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that
the method had higher sensitivity and could count bacteria in 3 × 102 CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence
peak intensity (Y) and the total bacterial count (X) was established in the range of 3 × 102–107 CFU/mL using the equation Y = 374.82X − 938.27 (R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the
conventional plate count method, and the standard deviation was satisfactory. 相似文献
6.
S. K. Arya Tanvi Vats Shailesh N. Sharma Kulvir Singh A. K. Narula 《Journal of Thermal Analysis and Calorimetry》2012,107(2):555-560
In this study, we have studied the stability of TiO2–CdSe nanocomposites in which the individual moieties are linked using a bifunctional linker (mercaptopropionic acid). Nanoparticles
of TiO2 and CdSe are synthesized by sol–gel and one pot methods. The equimolar amount of the above particles is utilized to prepare
nanocomposites with and without linker. These samples are characterized for their structural, thermal, and optical properties
using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG), Fourier transform infra-red
spectroscopy (FTIR), and UV–Vis spectroscopy. The average particle size of TiO2 and CdSe are 16 and 23 nm, respectively. The addition of a bifunctional linker shows remarkable effect on the properties
of TiO2–CdSe nanocomposites. 相似文献
7.
8.
水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用 总被引:4,自引:0,他引:4
用巯基乙酸(TGA)作为稳定剂,合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明,核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下,将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现,两种量子点均对BSA的荧光产生较强的静态猝灭作用;而BSA对两种量子点的荧光则具有显著的荧光增敏作用,存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。 相似文献
9.
D.A. Hummel I.L. Torriani A.F. Craievich N. Fox de la Rosa A.Y. Ramos O. Lyon 《Journal of Sol-Gel Science and Technology》1997,8(1-3):285-291
Small-angle X-ray scattering (SAXS) experiments were carried out to characterize the structure of the composite formed by
CdSe nanocrystals embedded in a popous silica matrix (silica xerogels containing Cd with formamide addition and ultrasound
treatment). SAXS results from samples before Se diffusion indicate the presence of heterogeneities with a bimodal size distribution
which was associated to the existence of mesopores (pores of several hundred Å) immersed in a nanoporous matrix (characteristic
pore radii of 20–30 Å). The diffusion of Se induces the nucleation and growth of CdSe nanocrystals. The average size of the
nanocrystals increases with Cd content. Higher Se doses promote the formation of larger nanocrystals (radius of gyration of
∼30 to 50 Å). Anomalous scattering results confirm the existence of Se aggregation associated with CdSe nanocrystal formation
and suggest that only partial segregation of Cd and Se occurs. 相似文献
10.
Water-soluble CdSe nanoparticles were synthesized using AOT (sodium bis(2-ethylehexyl)-sulfosuccinate) as stabilizer, cadmium acetate and Na2SeSO3 as precursors in aqueous phase. The influence of some key factors, such as reaction time, temperature, concentration and molar ratio of precursors on the optical properties of CdSe nanoparticles was systematically investigated through UV-Vis and PL spectra. Powder X-ray diffraction (XRD) was used to characterize the crystalline structure of synthesized CdSe nanoparticles. As-prepared CdSe nanoparticles exhibit an apparent quantum confinement effect and typical hexagonal wurtzite structures. Finally, the optimal experimental conditions were obtained. 相似文献
11.
Zou S Hong R Emrick T Walker GC 《Langmuir : the ACS journal of surfaces and colloids》2007,23(4):1612-1614
Hierarchical, high-density, ordered patterns were fabricated on Si substrates by self-assembly of CdSe nanoparticles within approximately 20-nm-thick diblock copolymer films in a controlled manner. Surface-modified CdSe nanoparticles formed well-defined structures within microphase-separated polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) domains. Trioctylphosphine oxide (TOPO)-coated CdSe nanoparticles were incorporated into PS domains and polyethylene glycol-coated CdSe nanoparticles were located primarily in the P2VP domains. Nearly close-packed CdSe nanoparticles were clearly identified within the highly ordered patterns on Si substrates by scanning electron microscopy (SEM). Contact angle measurements together with SEM results indicate that TOPO-CdSe nanoparticles were partially placed at the air/copolymer interface. 相似文献
12.
Shu Chen Chen Guo Guo-Hua Hu Hui-Zhou Liu Xiang-Feng Liang Jing Wang Jun-He Ma Lily Zheng 《Colloid and polymer science》2007,285(14):1543-1552
Dissipative particle dynamics (DPD) was used to simulate the formation and stabilization of gold nanoparticles in poly(ethylene
oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymer micelles. Primary gold clusters that were
experimentally observed in the early stage of gold nanoparticle formation were modeled as gold bead in DPD simulation. It
showed that gold beads were wrapped by the block copolymer and aggregated into spherical particles inside the micelles and
forming stable Pluronic–gold colloids with two-layer structures. Increasing Pluronic concentration, molecular weight, and
PPO block length led to the formation of more uniform and more stable gold nanoparticles. Density profiles of water beads
suggested that the micelles, especially the hydrophobicity of the micellar cores, played an important role in stabilizing
gold nanoparticles. Dynamic process indicated that the formation of gold nanoparticles was controlled by the competition between
aggregation of primary gold clusters and the stabilization by micelles of block copolymers.. The DPD simulation results of
gold–copolymer–water system agree well with previous experiments, while more structure information on microscopic level could
be provided. 相似文献
13.
The interaction of water-soluble CdSe quantum dots (QDs) with gold (Au) nanoparticles was investigated by ultraviolet visible absorption spectroscopy. The results showed that the aggregation of Au nanoparticles was induced by CdSe QDs. The influences of factors such as the size of Au nanoparticles, acidity, buffer concentration and the concentration ratio of the CdSe QDs to Au nanoparticles were each investigated. The comparison of two different particle sizes (16 and 25 nm) of Au nanoparticles that interact with CdSe QDs in the solution showed that the aggregation of small Au nanoparticles (16 nm) is easier than that of big Au nanoparticles (25 nm). At pH 7.0 phosphate buffer solution (0.02 M), the optimal molar ratio of CdSe:Au is about 3100:1 according to calculations. 相似文献
14.
Zhi-juan Zhang Chun-xia Wang Yong Wang Shu-hua Niu Chang-gui Liu De-gang Fu 《化学物理学报(中文版)》2007,20(6):796-800
"?Fluorescence spectra of naked gold nanoparticles, triphenylphosphine stabled gold nanoparticles, and 3-mercaptopropionic acid substituted gold nanoparticles were studied. It was found that fluorescence intensities of gold nanoparticles were highly sensitive to surface molecules. The fluorescence quenching effect of these gold nanoparticles on CdSe nanoparticles was also investigated. This quenching effect was related to the overlap degree between the absorption spectra of gold nanoparticles and the emission spectrum of CdSe nanoparticles, and was surface-dependent as well. " 相似文献
15.
16.
Jeremy Mallet Ibrahima Kante Patrick Fricoteaux Michaël Molinari Michel Troyon 《Journal of Solid State Electrochemistry》2012,16(3):1041-1047
Cadmium selenite (CdSe) nanowires have been electrodeposited by potentiostatic method using polycarbonate membranes as template.
For the same potential value, the pH modification of the solution or the temperature variation of the substrate leads to drastic
differences of the CdSe composition. A meticulous study of the influence of both temperature and pH value on the stoichiometry
of electrodeposited CdSe nanowires has been done and several combinations of temperature/pH leading to the 50–50 CdSe composition
have been found. The as-electrodeposited CdSe nanowires under these specific conditions reveal a good crystallinity with a
<111> preferred growth orientation exhibiting a luminescence band in the visible range corresponding to the CdSe gap. 相似文献
17.
Hui Zhang FengKai Hu Quan Zhou WenZhi Zhang 《Journal of Dispersion Science and Technology》2013,34(7):1132-1135
The optical properties of 2 mixing types of CdS‐CdSe nanoparticles (i.e., coprecipitated CdS‐CdSe nanoparticles, CdS‐coated CdSe (CdSe/CdS)) were studied. Results indicated that the co‐precipitated nanoparticles kept the similar optical properties of both CdS and CdSe's, while the CdS/CdSe core‐shell structure showed totally different optical properties from the simple components. We paid special attention to the core/shell structure, as the core‐shell structure showed a better passivating effect. Therefore, the XRD and TEM were tested on the core‐shell structure. XRD results showed that the diffraction patterns of core‐shell structure were roughly the same as their simple components. And the TEM indicated the core‐shell structure had a uniform dispersion in the solution. 相似文献
18.
19.
Cadmium hydroxide-deposited cadmium selenide nanoparticles were prepared by the addition of cadmium sulfate solution to cadmium selenide nanoparticles in a weak alkaline solution at room temperature. The photoluminescence measurements displayed that the luminescence intensity was greatly increased by the addition of cadmium ions due to the formation of cadmium hydroxide on the surfaces of the cadmium selenide nanoparticles. Then, CdSe/Cd(OH)2/SiO2 nanocomposite particles were synthesized using 3-mercatopropyl trimethoxysilane by Stöber method. After the formation of CdSe/Cd(OH)2/SiO2 nanocomposite particles, the emission ability was mostly stabilized. Additionally, the stabilization of the composite particles against dilution with the physiological saline was checked. The results showed that the photoluminescence stability was promoted after the deposition of silica on the surfaces of the CdSe/Cd(OH)2 nanoparticles. Comparison of the stability of CdSe/SiO2 nanoparticles with that of CdSe/Cd(OH)2/SiO2 ones showed that Cd(OH)2 shell could enhance the photoluminescence effectively. 相似文献
20.
Chao-Ching Chang Pei-Huan Chen Chih-Ming Chang 《Journal of Sol-Gel Science and Technology》2008,47(3):268-273
In this study, acrylic polymer–nanogold nanocomposites and their cast films were prepared from an acrylic copolymer and 3-mercaptopropyltrimethoxysilane
(MPS) stabilized gold nanoparticles by a sol–gel reaction. The acrylic copolymer was synthesized from methyl methacrylate
(MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). The Si–OMe groups of MPS on the surface of gold nanoparticles (MPS–Au)
provided the further reaction with the same groups of MSMA, hence the covalent bonds between polymers and MPS–Au nanoparticles
were formed. FE-SEM images show MPS–Au nanoparticles are dispersed well in the prepared nanocomposites, and no large aggregation
is occurred. TGA results indicate that the decomposed temperatures (Td) of low Au-content (0.1 wt.%) nanocomposites are higher than these of the acrylic copolymer and high Au-content (1.0 wt.%)
nanocomposites. The temperature of maximum decomposed rate (Tp) of each prepared nanocomposite is higher than that of the acrylic copolymer. The hardness of the cast film increases with
increasing the Au content. The results show the improved thermal stability and application potentials of the prepared acrylic
polymer–nanogold nanocomposites. 相似文献