Percolation in networks of aligned SWNTs formed with laminar flow deposition

Macroscopic networks of highly aligned SWNTs have been fabricated at room temperature by laminar flow deposition from aqueous suspensions. This deposition method allows the growth of a macroscopic two dimensional SWNT network through successive deposition cycles. AFM image analysis showed that each deposition cycle puts down a reproducible density of SWNTs, with the final density being directly proportional to the number of deposition cycles for a given solution. The macroscopic electronic behavior of these networks was characterized by DC conductance measurements taken after each deposition cycle. This showed that these networks could be described by two dimensional percolation models throughout the growth process.     

Disposable biosensor based on Au nanoparticles-modified CdS nanorod arrays for detection cytochrome c

A novel disposable biosensor is developed based on gold nanoparticles modified CdS nanorod arrays. The ordered CdS nanorod arrays firstly have been synthesized by a simple hydrothermal method. Then, the CdS nanorod arrays are modified by gold nanoparticles, which are directly fabricated into an electrode for detection of cytochrome c (Cyc) in solution without any pretreatment. The modified CdS nanorod arrays biosensor with the immense surface area and high electrical conductivity shows a good sensitivity and linear range. This method may be used to construct other electrochemical biosensors using aligned nanorod/nanowire films.     

利用水溶性聚合物PVP作稳定剂合成CdS、CdSe半导体纳米晶体

以水溶性聚合物聚乙烯基吡咯烷酮(PVP)作分散剂,在水相溶液中制备CdS/PVP纳米粒子.通过控制水溶液体系的pH值或者分散剂含量,实现了纳米粒子从球形到棒状的转变;同时探讨了Cd/S比值变化对纳米粒子结构的影响.利用原子力显微镜(AFM)表征CdS/PVP纳米体系的形貌,并进一步利用透射电镜(TEM)、红外光谱(FT-IR)和粉末X-射线衍射(XRD)等对其结构进行了分析和研究.     

Synthesis of CdS and alloyed CdMnS nanocrystals using aqueous foams

Certain surfactant-stabilized aqueous foams provide a potentially efficient and simple chemical route for the synthesis of various nanomaterials with controllable structure, size, and shape. In the present work, a one-step process for the synthesis of CdS and Cd1-xMn(x)S (0 < x < 10) nanocrystals has been described. Aqueous CdCl2 and the aerosol-OT solutions are homogeneously mixed together and thereafter, nitrogen is bubbled through this solution to produce stable aqueous foam. After drainage of the foam, the freestanding dry foam consisting of cadmium cations electrostatically complexed with the anionic aerosol-OT molecules at the liquid-gas interface is treated with H2S vapor. The foam turns yellowish-orange and collapses, in the process yielding CdS nanoclusters of variable morphology. This morphology variation is appropriately attributed to growth of the CdS as well as alloyed Cd1-xMn(x)S nanoparticles in different regions of the foam contributing to the varying topological structure. Optical absorption spectra of both CdS and Cd1-xMn(x)S nanoparticles clearly show a well-defined exciton absorption feature around 450 nm due to quantum confinement effects. The interesting band edge emission characteristics of these AOT-capped CdS and Cd1-xMn(x)S nanoparticles produced in the foam are discussed with respect to their size and shape. Particular interest in the present novel aqueous foam approach arises due to the fact that the cubic zincblende CdS and alloyed Cd1-xMn(x)S nanocrystals could easily be obtained even under ambient experimental conditions itself.     

聚乙烯吡咯烷酮硫脲修饰CdS纳米粒子的制备

用硫脲为表面修饰剂,并用PVP(聚乙烯吡咯烷酮)为稳定剂在乙醇水溶液中合成了粒径分布均匀、性能稳定、有机物修饰的CdS纳米颗粒.重点分析了硫脲的引入对CdS纳米粒子晶体结构、粒径分布、紫外可见吸收光谱、红外光谱、光致荧光光谱(PL)的影响.发现硫脲修饰使得CdS纳米粒子的粒径更小,粒径分布更加均匀,并且有效地抑止了PVP对CdS荧光淬灭,在PL光谱上观察到了CdS的带隙发光.     

Growth of the oxidized nickel nanoparticles on a DNA template in aqueous solution

Oxidized nickel nanoparticles ranging from 2 to 3 nm have been grown on a DNA template. The synthesized products have been characterized by AFM and XPS. The results showed that uniformly oxidized nickel nanoparticles can be grown and assembled on a DNA template. These assembled small NiO nanostructures may have some potential application as catalysts, magnetic materials or electrochromic films. Theoretically, this synthetic method can be applied to fabricate other metals on a DNA template.     

Facile control of DNA-templated inorganic nanoshell size

We elaborated a facile method to control the size of CdS nanoshells obtained by DNA assisted "double templating" approach. By changing the concentration of NaCl in solution to vary the extent of DNA electrostatic deposition on cationic silica beads, we succeeded to control the density of DNA adsorbed on the beads, and further the density of CdS material grown on DNA. Further dissolution of the silica core triggers shrinking of CdS shell to a different extent depending on the CdS shell density and results in formation of CdS nanoshells of different sizes from ca. 100 nm to ca. 400 nm. Therefore, the main advantage of the proposed method is that it can be used to synthesize hollow nanoshells of various sizes, from ca. 25% to ca. 75% size of the primary template (silica bead), by using only one single primary template.     

应用DNA模版自组装CdS纳米线

近年来,由于具有双螺旋补偿结构,DNA分子作为智能模版被广泛应用于设计棒状或管状类的纳米结构.本文报道了应用DNA双螺旋模版将CdS纳米粒子自组装为CdS纳米线.制备的CdS纳米线由几根纳米线紧密缠绕在一起,也呈螺旋形结构,该结构在无机材料中是很少见的.该结构形成的主要原因归功于CdS纳米粒子和DNA分子间的强烈静电互作用,由于含自由基的CdS纳米粒子带负电荷,而氨基的DNA核酸根带正电荷.研究结果表明应用DNA模版制备纳米线是一种简便、高效的技术和方法.同时,DNA模版法也为从底上制备纳米级的材料和物体提供了广阔的空间.     

水溶性Cu∶CdTe/CdS核壳量子点的合成、表征及细胞毒性检测

采用水相法合成了Cu掺杂CdTe量子点,并用CdS壳层进行包覆,得到了Cu∶CdTe/CdS核壳结构量子点。采用荧光发射光谱(FL)、紫外可见吸收光谱(UV-Vis)、透射电镜(TEM)以及能谱仪(EDS)等手段对CdTe量子点和Cu∶CdTe/CdS核壳量子点进行了表征。研究了不同Cu掺杂浓度、CdS壳层生长时间以及Cd/硫脲物质的量比对Cu∶CdTe掺杂量子点光学性能的影响,并采用人成骨肉瘤细胞(MG-63细胞)对样品做了细胞毒性分析。研究结果表明:通过掺杂和包壳的步骤,合成的Cu∶CdTe/CdS核壳量子点在CdTe量子点的基础上实现了荧光发射红移,荧光强度提高,以及细胞毒性降低。     

Tailoring silver nanoparticle construction using dendrimer templated silica networks

We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles.     

Study on the binding of procaine hydrochloride to DNA/DNA bases and the effect of CdS nanoparticles on the binding behavior

The interaction between procaine hydrochloride and DNA/DNA bases in the absence and presence of cadmium sulfide (CdS) nanoparticles has been explored in this study by using differential pulse voltammetry, atomic force microscopy (AFM) and so on, which illustrates the different binding behaviors of procaine hydrochloride with different DNA bases. The results clearly indicate that the binding of purines to procaine hydrochloride is stronger than that of pyrimidines and the binding affinity is in the order of G > A > T > C. In addition, it was observed that the presence of CdS nanoparticles could remarkably enhance the probing sensitivity for the interaction between procaine hydrochloride and DNA/DNA bases. Furthermore, AFM study illustrates that procaine hydrochloride can bind to some specific sites of DNA chains, which indicates that procaine hydrochloride may interact with some special sequences of DNA.     

水溶性量子点制备条件的优化及表面修饰

以L-半胱氨酸为稳定剂在水溶液中合成CdSe纳米粒子,研究了水浴时间、水浴温度、不同L-半胱氨酸/Cd/Se比例、pH值等因素对其荧光光谱的影响,确定了最佳的合成方案.用CdS对其表面进行修饰,采用透射电镜、X射线衍射、光谱法等表征了Cdse/CdS核壳结构颗粒的形成,结果表明该纳米粒子发光强度明显高于单一的CdSe量子点,光谱峰位置有所红移;合成条件会显著影响CASe/CAS核壳结构量子点的荧光性能.     

Optical and structural properties of chemically deposited CdS thin films on polyethylene naphthalate substrates

CdS thin films were deposited on polyethylene naphthalate substrates by means of the chemical bath deposition technique in an ammonia-free cadmium-sodium citrate system. Three sets of CdS films were grown in precursor solutions with different contents of Cd and thiourea maintaining constant the concentration ratios [Cd]/[thiourea] and [Cd]/[sodium citrate] at 0.2 and 0.1 M/M, respectively. The concentrations of cadmium in the reaction solutions were 0.01, 7.5 × 10⁻³ and 6.8 × 10⁻³ M, respectively. The three sets of CdS films were homogeneous, hard, specularly reflecting, yellowish and adhered very well to the plastic substrates, quite similar to those deposited on glass substrates. The structural and optical properties of the CdS films were determined from X-ray diffraction, optical transmission and reflection spectroscopy and atomic force microscopy measurements. We found that the properties of the films depend on both the amount of Cd in the growth solutions and on the deposition time. The increasing of Cd concentration in the reaction solution yield to thicker CdS films with smaller grain size, shorter lattice constant, and higher energy band gap. The energy band gap of the CdS films varied in the range 2.42-2.54 eV depending on the precursor solution. The properties of the films were analyzed in terms of the growth mechanisms during the chemical deposition of CdS layers.     

Ecotoxicological studies of CdS nanoparticles on photosynthetic microorganisms

The potential ecotoxicity of nanosized cadmium sulfide (CdS), synthesized by the polyol process, was investigated using common Anabaena flos-aquae cyanobacteria and Euglena gracilis euglenoid microalgae. The photosynthetic activities of these microorganisms, after addition of free Cd2+ ions and CdS nanoparticles, varied with the presence of tri-n-octylphosphine oxide (TOPO) used to protect surface particle to avoid toxicity and also to control particle size and shape during the synthesis. The nanoparticle concentration was varied from 10(-3) to 5 x 10(-4) M. It was observed that the cadmium concentration, the addition of TOPO protective agent and the particle dissolution process in the culture medium play an important role during the ecotoxicological tests. Viability tests were followed by PAM fluorimetry. Cd2+ ions were very toxic for Anabaena flos aquae. The same behavior was observed after contact with CdS and CdS-TOPO nanoparticles. However, for Euglena gracilis, the photosynthetic activity was stable for more than 1 month in the presence of Cd2+ ions. Moreover, it was observed that the toxicity varies with the concentration of CdS and CdS-TOPO nanoparticles, both kind of nanoparticles are toxic for this microorganism. Transmission electron microscopy (TEM) analyses of microorganisms ultrathin sections showed that polysaccharides produced by Anabaena flos-aquae, after contact with CdS and CdS-TOPO nanoparticles, protect the microalgae against particle internalization. Only some particles were observed inside the cells. Moreover, the nanoparticle internalization was observed after contact with all nanoparticles in the presence of Euglena gracilis by endocytosis. All nanoparticles are inside vesicles formed by the cells.     

Patterned self-assembly of gold nanoparticles on chemical templates fabricated by soft UV nanoimprint lithography

Chemical templates for the patterned immobilization of gold nanoparticles were fabricated by soft UV nanoimprint lithography. The template structures were fabricated by means of the consecutively performed process steps of nanoimprint lithography, reactive ion etching, chemical functionalization with amino groups, and lift-off of imprint resist. These chemical templates were used for the defined assembly of 20 nm diameter citrate stabilized gold nanoparticles from aqueous solution. By reducing the ionic strength of the solution, one- and zero-dimensional particle assemblies were generated on sub-100-nm template structures. By this means, the pattern resolution predefined by the lithography process could be easily enhanced by dilution of the nanoparticle solution.     

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.     

甲醇介质中溶剂热合成六方CdS中空纳米球

以甲醇为溶剂, 硝酸镉和硫脲为原料, 通过溶剂热法合成了CdS中空纳米球, 采用TEM、EDS和XRD对样品形貌和结构进行了表征. TEM与EDS分析显示产物主要为洋葱状CdS中空纳米球, 外径为5～17nm, 空腔直径为3～14nm. XRD分析结果表明,CdS中空纳米球为六方纤锌矿结构. 并初步考察了醇类溶剂对形成CdS纳米结构的影响. 结果表明,当以无水乙醇或正戊醇为溶剂时,产物分别为CdS颗粒团簇或CdS纳米颗粒组装的微球,说明甲醇对中空结构的形成起了重要作用. 以甲醇作溶剂时, 中空纳米球的形成可能是CdS纳米片层高压下卷曲形成的.      

Controlled Preparation and Formation Mechanism of Hydroxyapatite Nanoparticles under Different Hydrothermal Conditions

Hydroxyapatite(HAP) nanoparticles with uniform morphologies and controllable size were synthesized successfully by molecular template hydrothermal approach.The organic alcohols including ethanol,glycol,glycerol and butanol were used as templates to regulate the nucleation and crystal growth.The synthesized powders were characterized by X-ray diffraction,Fourier infrared spectrum and transmission electron microscopy.The results showed that the obtained HAP particles were uniform rod-like crystals,and the template molecular structures had significant effect on the morphology and size of HAP particles.The template molecules with longer hydrophobic groups resulted in longer particle length and larger aspect ratio.Compared with the concentration of template molecules,the template molecular structure showed larger influence on controlling the HAP morphology and size.Furthermore,the formation mechanism of these rod-like HAP particles prepared by alkyl alcohol templates was discussed.Moreover,hydrothermal treatment temperature and time could be also used for controlled preparation of HAP nanoparticles.     

Self-assembly and alignment of semiconductor nanoparticles on cellulose nanocrystals

The synthesis of cadmium sulfide (CdS), zinc sulfide (ZnS), and lead sulfide (PbS) nanoparticle chains on cellulose nanocrystal (CNC) templates can be accomplished by the reaction of the precursor salts. The use of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was critical for the synthesis of well-defined semiconductor nanoparticle chains on the surface of the CNCs. The semiconductor nanoparticle particle size and packing density on CNC surface could be controlled by the variation of the precursor concentration and the pH of the salt solution.     

Fabrication and characterization of ordered macroporous semiconductors CdS by colloidal crystal template

The synthesis and characterization of a highly ordered macroporous CdS with regular arrays of spherical pores comparable to optical wavelengths are discussed. The sample has been successfully fabricated using colloidal crystal of poly (styrene-acrylic) (PSA) spheres as templates. The pore size is tunable in the range of 100-400 nm based on the size of PSA spheres. Transmission electron microscope (TEM) and scanning electron microscope (SEM) show that the exactly three-dimensional structure of the template has been imprinted in the final materials. XRD pattern indicates that the walls of the macroporous material are composed of 4 nm CdS nanoparticles making the absorption spectrum shift blue. The sample was also characterized by Raman spectroscopy and photo luminescent spectra (PL).