Preparation and optical properties of silver nanoparticles in R-phycoerythrin,a protein matrix

Ag⁺ chemisorption by R-phycoerythrin in an aqueous solution is shown to lead to the formation of silver nanoparticles, without the need for a reductant of Ag⁺. According to electron-microscopic results, most of the nanoparticles are elongated, (3 ± 0.5) × (6 ± 2) nm in dimensions. Also present are cubic Ag crystallites 22.5 nm in size (standard deviation of ±5.9 nm) and aggregates 53 × 48 nm in dimensions (standard deviation of ±8.8 × 8 nm). The absorption spectrum of the Ag nanoparticles in R-phycoerythrin is typical of small nanoparticles. Their fluorescence spectrum shows peaks of individual nanoparticles (450 nm) and fractal aggregates (630 and 670 nm). The fluorescence intensity of the Ag nanoparticles and their aggregates is an order of magnitude higher in comparison with other matrices.     

Effect of CdS nanoparticles on the properties of a protein matrix

The effect of CdS nanoparticles on the properties of a protein matrix, R-phycoerythrin, has been studied using absorption and fluorescence spectroscopy techniques, atomic force microscopy, confocal fluorescence microscopy, and analytical ultracentrifugation. The results demonstrate that CdS nanoparticles distort the native state of R-phycoerythrin, as evidenced by the reduction in absorption, partial fluorescence quenching, the reduction in fluorescence lifetime from 2.9 to 1.9 ns in solution and the increase to 3.3 ns upon adsorption on glass, and the influence of CdS nanoparticles on the sedimentation coefficient distribution of R-phycoerythrin. We conclude that a CdS nanoparticle synthesized inside an R-phycoerythrin molecule influences the chromophore—chromophore interaction and stabilizes the hexamer form of the protein.     

Synthesis and properties of CdS nanoparticles in a polyethylene matrix

Nanocomposites of cadmium sulfide and high-pressure polyethylene have been synthesized. The mechanism of the thermal decomposition of thiourea complexes during the synthesis of cadmium sulfide nanoparticles has been investigated. The nanoparticle size, composition, and structure of the nanocomposites have been determined by x-ray diffraction, transmission electron microscopy, IR spectroscopy, and EXAFS spectroscopy, and the thermal decomposition of the nanomaterials has been studied.     

Nanomaterials based on CdS nanoparticles in polyethylene matrix

The synthesis of CdS nanoparticles stabilized in the bulk of a polyethylene matrix is described. The size of synthesized nanoparticles is determined by means of transmission electron microscopy. The composition of nanoparticles is defined by X-ray phase analysis. It is shown that the variation of the process-dependent parameters during synthesis of nanoparticles in a polymer + oil solution melt results in the formation of CdS nanoparticles with average sizes of 4.9, 5.4, and 6.2 nm with a reasonably narrow size distribution and well-formed structure. The optical properties of synthesized nanomaterials are investigated. The investigation of Raman scattering reveals softening of the LO-phonon mode with decreasing CdS nanoparticle size. A broad high-energy band of photoluminescence connected with the exciton annihilation in conditions of size quantization is detected.     

CdS nanoparticles grown in a polymer matrix by chemical bath deposition

Nanocrystallites of CdS have been grown by chemical bath deposition within the pores of poly(vinyl alcohol) (PVA) on glass and Si substrates. The CdS-PVA composite films are transparent in the visible region. XRD and TEM diffraction patterns confirmed the nanocrystalline CdS phase formation. TEM study of the film revealed the manifestation of nano CdS phase formation and the average particles size was varied in the range 5-12 nm. UV-vis spectrophotometric measurement showed high transparency (nearly 80% in the wavelength range 550-900 nm) of the films with a direct allowed band gap lying in the range 2.64-3.25 eV. Particle sizes have also been calculated from the shift of band gap with respect to that of bulk value and were found to be in the range 3.3-6.44 nm. The high dielectric constant (lies in the range 120-250 at high frequency) of PVA/CdS nanocomposite compared to that of pure PVA (-28) has been observed. The dielectric constant decreases with increase of dispersibility of the CdS nanoparticles within PVA. The nanocrystalline PVA/CdS thin films have also showed field emission properties with a turn-on field of approximately 6.6 V/microm, whereas only PVA thin film and bulk CdS on PVA have shown no field emission.     

Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix

Photoluminescence properties of polyvinyl pyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles embedded in polyvinyl alcohol matrix (PVA) are reported. The PVP-CdS nanoparticles are prepared by non-aqueous method wherein cadmium nitrate is used as the cadmium source and hydrogen sulphide as the sulphur source. The synthesized nanoparticles are dispersed in polyvinyl alcohol (PVA) matrix and cast as self-standing flexible (PVP-CdS)-PVA films. The nanocomposites are characterized by optical absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdS particles with average size ∼3-5 nm. Thermal studies, carried out to observe the changes in PVA matrix due to the incorporation of PVP-CdS nanoparticles show strong interaction between the polymer matrix and nanoparticles. The photoluminescence emission spectra of the nanocomposites show two peaks, at 502 and 636 nm, which are attributed to the band edge and surface defects respectively, of CdS nanoparticles. Effective surface capping with optimum concentration of polyvinyl pyrrolidone leads to the quenching of surface defect-related emission.     

Structural characterization of CdS nanoparticles grown in polystyrene matrix by thermolytic synthesis

Cadmium sulfide nanoparticles embedded in a polystyrene matrix (CdS/PS) were successfully prepared by in situ thermolysis of a cadmium thiolate precursor dispersed in the polymer. The heat-induced formation of cadmium sulfide was studied by thermogravimetric analysis and differential thermal analysis, while the chemistry of the reaction forming the CdS/PS compound was investigated by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The CdS nanocrystals are single crystals of cubic phase (zincblende structure) of spherical shape. The average diameter of the nanocrystals embedded in the polystyrene matrix achieved by our synthesis process is as small as 2.5 ± 0.5 nm. Room temperature UV–VIS absorption spectra exhibit a shoulder at 412 nm that is consistent with the presence of CdS nanocrystals of ∅ ≈ 2 nm. The role of the polymer on the nanoparticle growth was also discussed.     

CdS nanoparticles in polymer matrices

This paper examines the mechanisms of metal sulfide formation with the participation of metal complexes with thiourea. We have synthesized cadmium sulfide nanoparticles using carbon-chain polymers as stabilizers and investigated the effect of the polymer matrix on the properties of the nanoparticles.     

A solid state nuclear magnetic resonance study on the thermolytic synthesis of CdS nanoparticles in a polystyrene matrix

We report on the optimization of the thermolytic synthesis of cadmium sulfide (CdS) nanoparticles in a polystyrene (PS) matrix. The annealing conditions were tuned on the basis of the indications coming from solid state ¹¹³Cd and ¹³C Nuclear Magnetic Resonance (NMR) experiments. ¹¹³Cd NMR provided direct evidence of CdS nanoparticles formation. Semi-quantitative ¹³C NMR experiments demonstrated that good quality samples are obtained by heating up precursor/polystyrene films to 270 °C in vacuum. X-ray diffraction (XRD) and wide angle X-ray scattering (WAXS) experiments revealed structural details of CdS nanoparticles, their average size ranging from 1 to more than 7 nm as a function of the annealing conditions.     

Formation of CdS nanoparticles by gas-diffusion method in sol–gel derived ureasilicate matrix

CdS nanoparticles (NPs) were prepared by exposing a hybrid ureasilicate gel containing cadmium (II) ions to H₂S gas at room temperature. Additional component (tetraethoxysilane) was introduced during the synthesis in order to improve the mechanical properties of the host matrix. The obtained material was subsequently subjected to an annealing treatment under an argon atmosphere at temperatures that varied from 43 to 102 °C. The size of the embedded NPs increased with thermal annealing. The optical absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM) measurements confirmed the formation of CdS nanoparticles (NPs) exhibiting quantum confinement effect.     

Optical properties of silver nanoparticles in R-phycoerythrin nanochannels in aqueous solutions and films

The optical properties of Ag⁰ nanoparticles in R-phycoerythrin nanochannels have been studied in liquid and solid phases by confocal fluorescence microscopy, absorption spectroscopy, and fluorescence spectroscopy. The optical properties of the Ag⁰ nanoparticles are shown to depend on their phase state at the levels of an individual nanoparticle and many nanoparticles. UV irradiation has different effects on Ag⁰ nanoparticles in deionized water and in thin films on glass.     

Effect of heat-treatment on CdS and CdS/ZnS nanoparticles

Mono-dispersed and spherical cadmium sulfide (CdS) nanoparticles and cadmium sulfide/zinc sulfide (CdS/ZnS) nanoparticles, 4–5 nm in diameter, were synthesized in a heptane-AOT-water microemulsion system. The heat treatment of CdS and CdS/ZnS nanoparticles was annealed at 570 °C under the air atmosphere. The heat-treated nanoparticles were of variable large sizes and had enhanced crystallinity. UV–Vis spectra of heat-treated CdS and CdS/ZnS nanoparticles revealed a flat shape similar to that of bulk CdS compounds. The difference between the PL emission bands of organic-coated nanoparticles and heat-treated nanoparticles was small. The PL emission energy of heat-treated nanoparticles was improved by about 2–3 times compared with that of organic-coated nanoparticles.     

Fluorescent CdS nanoparticles for cell imaging

Fluorescent cadmium sulfide nanoparticles stabilized by an organic shell based on ethylenediaminetetraacetic acid have been prepared by chemical condensation in an aqueous solution. The nanoparticle concentration in aqueous solutions has been optimized and it has been shown that such hybrid nanoparticles can be used to image cell cultures and explore the cell structure. Not only the nanoparticle concentration but also the incubation time of the nanoparticle solution with the cell culture are essential for observing structural details.     

Synthesis and characterization of CdS nanoparticles

In the present work a chemical reduction method is followed to grow CdS nanoparticles at room temperature with varying the amount of reducing agent sodiumborohydride. The dispersed samples in ethanol are characterized using electron diffraction techniques. Simultaneously optical absorption, photoluminescence and longtime photorelaxation of these samples are studied at room temperature. An increase in band gap is observed in each case as compared to bulk CdS. Also particle size decreases with increased amount of reducing agent. Simultaneously long time relaxation increases with decrease of stoichiometric ratio of reducing agent. An attempt is made to correlate the structural, optical, electrical and opto-electrical properties.     

CdS纳米颗粒的合成方法研究及比较

CdS纳米颗粒在太阳能转化、非线性光学、光电子化学电池和光催化等方面具有广泛的应用,因此其合成方法的研究近年来受到人们的青睐.按照反应物的状态,将纳米硫化镉的制备方法分为固相法、液相法和气相法.本文详细介绍了各种制备方法,分析比较了它们的优点和缺点.     

CdS/CdSSe quantum dots in glass matrix

The compositions containing 55 and 60% of silica have been formulated for preparation of glass filters having sharp cut-off at 475 and 575 nm. To achieve cut-off at these wavelengths, the glasses have been doped with CdS/CdSSe and melted at 1200–1300°C. The glass samples were transparent and pale yellow in colour due to presence of CdS/CdSSe tiny nano crystal (Q-dots). In situ growth of CdS/CdSSe nano crystals imparts the yellow/orange/red colour to these glasses. Optical study shows that as prepared glasses have optical cut-off in the range 350–370 nm. The linear crystal growth of CdS/CdSSe in glasses exhibits red shift in optical cut-off. The optical filter having cut-off at 475 nm can be prepared by doping CdS and cut-off filter of wavelength 575 nm by CdSSe. The TEM results show that the CdS/CdSSe nano crystals (Q-dots) ranging from 2–5 nm are uniformly distributed into the glass matrix.     

Facile microwave-combustion synthesis of wurtzite CdS nanoparticles

In this study we first report microwave-combustion synthesis of faceted CdS nanoparticles by using cadmium thiocyanate complex as a single source precursor. This is the first example of a metal-thiocyanate (M-SCN) complex being used as a source for metal sulfides (M-S) preparation in a microwave-combustion process. The synthesized CdS was characterized using X-ray diffraction (XRD), field mission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The by-product assisted combustion synthesis yields CdS nanoparticles with the mixtures of octahedral geometries, hexagonal, and triangle plate morphologies and the sizes were found to be 100 nm to 5 microm. The XRD patterns imply the formation of well crystallized wurtzite CdS. The influence of cadmium and sulfur precursors and microwave irradiation time on the morphology of CdS nanoparticle was also investigated. The cadmium and sulfur precursors strongly influenced the CdS morphology and increasing the microwave irradiation time and intensity has no effect on the CdS morphology. In addition, a plausible mechanism of CdS nanoparticle formation has been proposed in this research.     

CdS半导体纳米粒子合成与表征

以羟基化SBS为模板,乙酸镉、硫化钠为反应前驱物,利用盐诱导方式在四氢呋喃-甲醇-水体系中制备得到CdS纳米粒子。通过紫外-可见吸收光谱、荧光光谱及透射电子显微镜对CdS纳米粒子的光学性质及形貌进行了表征。结果表明,利用嵌段聚合物的两亲性质,可以得到稳定的具有明显量子尺寸效应的CdS半导体纳米粒子,透射电子显微镜结果表明所得到的CdS半导体纳米粒子具有冠状复合胶束结构。     

Synthesis,characterization and optical properties of CdS nanoparticles confined in SBA-15

A novel and dexterous in situ method is introduced to load CdS nanocrystals into SBA-15, which uses the acid–base reaction of mercaptoacetic acid with 3-aminopropyltriethoxysilane, the modifier of internal surface of mesoporous materials to facilitate loading of sulfur precursor, followed by adsorption of Cd²⁺ and calcination at 300 °C in N₂ atmosphere for 2 h. XRD, N₂ adsorption–desorption isotherms, HRTEM, EDS, FT-IR, UV–vis absorption spectrum and PL spectrum were used to characterize the composite material. It was found that the CdS nanocrystals were confined in the channel of SBA-15 with an average size of 6 nm. The mesoporous silica-supported CdS composites showed a room temperature photoluminescence property.     

Synthesis and characterization of CdS nanoparticles in polystyrene microfibers

We described the synthesis of hybrid fibers composed of cadmium sulfide (CdS) nanoparticles and polystyrene (PS) by an in-situ reaction method. Scanning electron microscopic (SEM) studies showed that the hybrid samples have a fiber-like morphology. Transmission electron microscopic (TEM) studies showed that CdS nanoparticles were embedded in PS fibers with a diameter from 10 to 20 nm. Fourier-transform infrared (FTIR), UV–vis spectrum and X-ray photoelectron spectra (XPS) were used to characterize the structure of the composite fibers. X-ray diffraction (XRD) results showed that a hexagonal CdS phase was obtained in the PS fibers.