Characterization of chemically synthesized CdS nanoparticles

II-VI semiconductor nanoparticles are presently of great interest for their practical applications such as zero-dimensional quantum confined materials and for their applications in optoelectronics and photonics. The optical properties get modified dramatically due to the confinement of charge carriers within the nanoparticles. Similar to the effects of charge carriers on optical properties, confinement of optical and acoustic phonons leads to interesting changes in the phonon spectra. In the present work, we have synthesized nanoparticles of CdS using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The UV-visible absorption, photoluminescence and Raman spectra of the sample are recorded and discussed briefly     

Synthesis of High Quality CdS Nanorods by Solvothermal Process and their Photoluminescence

Large-scale cadmium sulfide (CdS) nanorods with high quality were successfully synthesized by solvothermal method using ethylenediamine (en) aqueous as solvent. The as-obtained product was investigated by X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM), ultraviolet–visible (UV–Vis) spectrum and photoluminescence (PL) spectrum. The length and width of the CdS nanorods were in the range of 1–2 μm, 30–40 nm, respectively. XRD analysis revealed that the crystal structure of the product was hexagonal phase. Photoluminescence measurement showed that the nanobelts have two main emission bands around 470 and 560 nm, which should come from the higher-level transition and the intrinsic transition, respectively.     

Growth Behavior of CdS Nanoparticles Embedded in Polymer and Sol-Gel Silica Matrices: Relationship with Surface-State Related Luminescence

Chemical techniques were employed to synthesize CdS nanoparticles embedded in polymer (PEG 300) and sol-gel silica matrices. Systematic growth of particles (radius 3–9 nm) was obtained by adjusting post-deposition annealing temperature and time to examine the dependence of surface-state–related luminescence on particle size. Photoluminescence (PL) peak energy showed a linear dependence with a gentle slope in the weak confinement region and a steep slope in the strong confinement region, the divergence being observed near the excitonic Bohr radius for CdS. The empirical relation proposed for the weak confinement region could be used for estimating chemically prepared CdS nanoparticle size with a high degree of reliability from PL peak energy.     

CdS纳米粒子的自组装单分子膜制备研究

利用疏基乙酸与草酸的混合自组装单分子膜成功制备了粒径分布均匀的CdS纳米粒子，并用SEM，XRD，XPS，PL对样品进行了表征。SEM表明形成在自组装单分子膜表面上的CdS纳米粒子的平均粒径约为45nm。XPS表明在自组装单分子膜表面形成了CdS纳米粒子。PL谱表明CdS纳米粒子在675nm有一峰值波长，我们认为这一发光是由表面缺陷造成的。     

Functionalized Magnetite Nanoparticles—Synthesis,Properties, and Bio-Applications

Nanotechnology has generated tremendous hopes in recent years toward the design of advanced functional materials, especially in the bio-medical field. Nano-sized-materials such as magnetite nanoparticles display indeed fascinating physico-chemical properties that, if tuned properly, can be exploited to design new bio-diagnostic and therapeutic strategies as well as innovative biotechnology methodologies. Owing to their biocompatibility and excellent magnetic properties, magnetite nanocrystals have been the object of a tremendous amount of research in the last decade and numerous (bio)applications have been reported. Importantly, advances in the synthesis of magnetite nanoparticles enable excellent control over their size, shape, and composition. Despite these remarkable progresses, many issues remain to be overcome for these nanotechnology products to revolution the medical practice. The fine control and application of colloidal nanostructures such as magnetite nanoparticles in complex biological systems remains especially challenging. This article attempts to review the current status of magnetite nanoparticles preparation and use, with a special emphasis on bio-medical applications, but also to outline the promises and challenges associated to this emerging technology.     

Synthesis and Optical Properties of Anisotropic Metal Nanoparticles

In this paper we overview our recent studies of anisotropic noble metal (e.g. gold and silver) nanoparticles, in which a combination of theory and experiment has been used to elucidate the extinction spectra of the particles, as well as information related to their surface enhanced Raman spectroscopy. We used wet-chemical methods to generate several structurally well-defined nanostructures other than solid spheres, including silver nanodisks and triangular nanoprisms, and gold nanoshells and multipods. When solid spheres are transformed into one of these shapes, the surface plasmon resonances in these particles are strongly affected, typically red-shifting and even splitting into distinctive dipole and quadrupole plasmon modes. In parallel, we have developed computational electrodynamics methods based on the discrete dipole approximation (DDA) method to determine the origins of these intriguing optical features. This has resulted in considerable insight concerning the variation of plasmon wavelength with nanoparticle size, shape and dielectric environment, as well as the use of these particles for optical sensing applications.     

Phase transition of CdS in the presence of ethylenediamine and formation of hollow CdS submicron particles with needle-like structure

Solid submicron particles, composed of amorphous, hexagonal and cubic phase CdS, were synthesized in water–ethylenediamine solution by precipitating Cd²⁺ ions with S^2? ions, which were generated from the radiolytic reduction of Na₂S₂O₃. In addition, the effects of the absorbed dose on the crystallization process of CdS were investigated in detail. Moreover, hollow CdS submicron particles with needle-like structure could be obtained from the solid CdS submicron particles probably through a hollowing process based on Ostwald ripening and the phase transition of CdS from amorphous to crystalline. In the above processes, ethylenediamine played an important role.     

Thiol-Functionalized Palladium Nanoparticles Networks: Synthesis,Characterization, and Room Temperature (Toxic) Vapor Detection

The preparation of three different functionalized palladium nanoparticles (PdNPs) systems for room temperature BTX (benzene, toluene, p-xylene) sensing detection and their morphostructural characterization is described. PdNPs are prepared through a two-phase water/toluene wet chemical reduction method in the presence of bifunctional organic thiols as stabilizing agents suitable for the formation of covalently linked PdNPs networks: p-terphenyl-4,4″-dithiol (PdNPs-TR), biphenyl-4,4′-dithiol (PdNPs-BP), or with 9,9-didodecyl-2,7-bis(acetylthio)fluorene (PdNPs-FL). Comparing the hydrodynamic diameter values, TR and BP ligands help to obtain networks consisting of spherical NPs of about 2 nm, in which each bifunctional ligand act as a bridge between PdNPs. In contrast, PdNPs-FL show a population centered at <2R_H> = 45 ± 5 nm. To perform preliminary gas sensing measurements, PdNPs networks are cast deposited on interdigitated electrodes to study their resistive response toward volatile organic compounds (VOCs) such as benzene (0–5%), toluene (0–1.7%), and p-xylene (0–0.4%) (BTX) and common interfering gases (H₂S, NH₃, SO₂, and relative humidity, RH). PdNPs-FL show enhanced response to BTX with an appreciable response also toward H₂S and RH. PdNPs-TR exhibit a better ability to discriminate benzene gas with a negligible response after H₂S exposure. Moreover, all the PdNPs systems show little to no response to NH₃ and SO₂ gases, offering an interesting perspective in practical sensing applications.     

油溶性Ag纳米微粒的制备及表征

以双十八烷氧基二硫代磷酸吡啶盐为修饰剂 ,以单宁酸为还原剂 ,在水醇混合溶剂中合成了表面修饰的Ag纳米微粒 ,采用X射线粉末衍射仪、透射电子显微镜、傅立叶变换红外光谱仪、热分析仪等对其进行了结构表征 ,在四球摩擦试验机上测试了其抗磨性能 .结果表明 ,表面修饰的Ag纳米微粒粒径分布均匀 ,平均粒径约为15nm ,无团聚现象 ,可溶于液体石蜡等有机溶剂 ,作为润滑油添加剂 ,具有良好的抗磨作用 ,可显著提高基础油的承载力 .     

金纳米粒子的电化学合成及光谱表征

采用电化学方法合成各种形状的金纳米粒子,生成的金纳米粒子形貌与施加电流有关,通过匀速递增电流电解的方法,可制备得到哑铃形,球形以及棒状金纳米粒子,采用恒电流电解方法主要获得球形及哑铃形纳米粒子。利用透射电镜、紫外-可见光谱及拉曼光谱对金纳米粒子进行相关表征。紫外-可见光谱研究发现金纳米棒出现位于近红外区间的吸收峰(985 nm),由此推测棒的长径比约为6。以结晶紫为探针分子,研究了金纳米粒子的表面增强拉曼光谱(SERS)效应,并分析得出其平躺的吸附模式。根据形貌表征的结果推断了纳米粒子的生长机理。     

Synthesis and characterization of CdS/PVA nanocomposite films

A series CdS/PVA nanocomposite films with different amount of Cd salt have been prepared by means of the in situ synthesis method via the reaction of Cd²⁺-dispersed poly vinyl-alcohol (PVA) with H₂S. The as-prepared films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption, photoluminescence (PL) spectra, Fourier transform infrared spectroscope (FTIR) and thermogravimetric analysis (TGA). The XRD results indicated the formation of CdS nanoparticles with hexagonal phase in the PVA matrix. The primary FTIR spectra of CdS/PVA nanocomposite in different processing stages have been discussed. The vibrational absorption peak of CdS bond at 405 cm⁻¹ was observed, which further testified the generation of CdS nanoparticles. The TGA results showed incorporation of CdS nanoparticles significantly altered the thermal properties of PVA matrix. The photoluminescence and UV-vis spectroscopy revealed that the CdS/PVA films showed quantum confinement effect.     

室温合成硫化银纳米粒子及其X射线光电子能谱表征

在常温常压下制备了硫化银纳米粒子,选用廉价的氧化银和硫粉为原料,采用多聚甲醛为还原剂,并在乙二胺体系中完成了反应。所得产物用X射线光电子能谱、X射线粉末衍射和透射电镜进行了表征。X射线粉末衍射表明：产物为单斜相的硫化银;透射电子显微镜表明：产物为直径约为100nm的棒状纳米粒子,其对应的电子衍射斑点可以指标成(120)和(303),说明产物的结晶较好;X射线光电子能谱分析表明：产物中Ag属 1价而S属-2价,它们的原子个数比为Ag：S=1：0．453。对比实验表明：多聚甲醛和无水乙二胺都起了很关键的作用;多聚甲醛起了多重作用,它既是溶剂,又是中和剂,用以除去反应的副产物多个点-甲酸,从而加速了反应的进行。     

Poly(allylamine) Stabilized Iron Oxide Magnetic Nanoparticles

This paper describes a new method for the dispersing and surface-functionalization of metal oxide magnetic nanoparticles (10 nm) with poly(allylamine) (PAA). In this approach, Fe₃O₄ nanoparticles, prepared with diethanolamine (DEA) as the surface capping agent in diethyleneglycol (DEG) and methanol, are ligand exchanged with PAA. This method allows the dispersing of magnetic nanoparticles into individual or small clusters of 2–5 nanoparticles in aqueous solutions. The resulting nanoparticles are water soluble and stable for months. The PAA stabilized Fe₃O₄ nanoparticles are characterized by TEM, TGA, and FT-IR. The PAA-coated Fe₃O₄ nanoparticles will allow further chemical tailoring and engineering of their surfaces for biomedical applications.     

Colloidal Flower‐Shaped Iron Oxide Nanoparticles: Synthesis Strategies and Coatings

The assembly of magnetic cores into regular structures may notably influence the properties displayed by a magnetic colloid. Here, key synthesis parameters driving the self‐assembly process capable of organizing colloidal magnetic cores into highly regular and reproducible multi‐core nanoparticles are determined. In addition, a self‐consistent picture that explains the collective magnetic properties exhibited by these complex assemblies is achieved through structural, colloidal, and magnetic means. For this purpose, different strategies to obtain flower‐shaped iron oxide assemblies in the size range 25–100 nm are examined. The routes are based on the partial oxidation of Fe(OH)₂, polyol‐mediated synthesis or the reduction of iron acetylacetonate. The nanoparticles are functionalized either with dextran, citric acid, or alternatively embedded in polystyrene and their long‐term stability is assessed. The core size is measured, calculated, and modeled using both structural and magnetic means, while the Debye model and multi‐core extended model are used to study interparticle interactions. This is the first step toward standardized protocols of synthesis and characterization of flower‐shaped nanoparticles.     

核/壳结构ZnS : Mn/CdS纳米粒子的制备及发光

利用溶剂热法制备了Mn离子掺杂的ZnS纳米粒子(ZnS : Mn),利用沉淀法对ZnS ∶ Mn纳米粒子进行了不同厚度的CdS无机壳层包覆。采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)及光致发光(PL)光谱等手段对样品进行了表征。TEM显示粒子为球形,直径大约在14~18 nm之间。由XRD结果可以看出CdS壳层的形成过程受到了ZnS ∶ Mn核的影响,导致其结晶较差。XRD和XPS测量证明了ZnS : Mn/CdS的核壳结构。随着CdS壳层的增厚,样品的发光强度呈现一直减弱的现象。     

Synthesis and Optical Characterization of CdS Nanowires by Chemical Process

Cadmium sulfide (CdS) nanostructured materials were synthesized by a wet chemical route without using any capping agent. X-ray diffraction pattern showed the typical interplanar spacings corresponding to the cubic phase of CdS. Transmission electron microscopy studies showed the nanowires formation with length in the range 0.1–1.5 μm and the diameter 25–30 nm. UV–visible optical spectroscopy study was carried out to determine the bandgap of the nanostructured CdS thin films and it showed blue shift with respect to the bulk value. Variation of band gap energies with annealing temperature was also studied in detail. Room temperature photoluminescence of the nano-CdS films was measured and the spectrum showed a broad band centered at ~567 nm, which originated from trap states existing in the forbidden energy gap.     

Synthesis and Characterization of ZnO Nanoparticles and Their Natural Rubber Composites

Abstract

Nanoparticles of zinc oxide were synthesized by a solution combustion method. The average size of these particles was analyzed by using X-ray diffraction. Composites of natural rubber and the ZnO nanoparticles were prepared by a latex blending method. The matrix phase was cured by using the crosslinking agent, pentane-1,5-diylidenediamine. Effects of crosslinking and incorporation of nanoparticles on the tensile and solvent transport properties of the natural rubber were studied in detail. The nature of the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was observed from the tensile studies that the addition of the curing agent and the ZnO nanoparticles increased the stability considerably. Incorporation of the nanoparticles also considerably increased the solvent resistance of the cured natural rubber. We suggest the addition of ZnO nanoparticles at a low loading level provided better properties compared to other reinforcements, such as carbon black and nano-clay.     

小尺寸铕(Ⅲ)配合物荧光纳米颗粒的制备

利用再沉淀法分别制备出了小尺寸(~10nm)纯相和杂相的Eu³⁺配合物荧光纳米颗粒。所制备的纯相的荧光纳米颗粒在水溶液中容易聚集,并且荧光猝灭严重。相比较而言,掺有适量疏水性硅烷的杂相纳米颗粒则具有较强的荧光、均匀的尺寸和良好的分散性。硅烷在碱性环境下(pH=9)迅速地水解,而后在纳米微粒的表面形成二氧化硅薄层。亲水的二氧化硅薄层消除了Eu³⁺配合物纳米颗粒间的疏水相互作用,进而防止了纳米颗粒的聚集,从而导致了杂相荧光纳米颗粒发光性能的提高。     

Quenched Emission of Fluorescence by Ligand Functionalized Gold Nanoparticles

A fluorescence-based detection scheme that uses ligand functionalized gold nanoparticles is proposed. The transduction scheme is based on the strong quenching of the fluorescence emission exerted by metallic surfaces on fluorophores positioned in their immediate vicinity (< 5 nm). Binding of fluorophore-labeled anti-biotin to biotinylated gold nanoparticles resulted in decreased fluorescence emission intensity. Subsequent competitive dissociation of labeled anti-biotin with D-biotin resulted in increased fluorescence emission intensity. These interactions occurred by means of specific molecular recognition because when the binding sites of anti-biotin were saturated with D-biotin prior to interaction with the gold nanoparticles; changes in the fluorescence emission intensity were not observed.