Synthesis and characterization of the water-soluble silica-coated ZnS:Mn nanoparticles as fluorescent sensor for Cu ions

Silica-coated ZnS:Mn nanoparticles were synthesized by coating hydrophobic ZnS:Mn nanoparticles with silica shell through microemulsion. The core–shell structural nanoparticles were confirmed by X-ray diffraction (XRD) patterns, high-resolution transmission electron microscope (HRTEM) images and energy dispersive spectroscopy (EDS) measurements. Results show that each core–shell nanoparticle contains single ZnS:Mn nanoparticle within monodisperse silica nanospheres (40 nm). Photoluminescence (PL) spectroscopy and UV–vis spectrum were used to investigate the optical properties of the nanoparticles. Compared to uncoated ZnS:Mn nanoparticles, the silica-coated ZnS:Mn nanoparticles have the improved PL intensity as well as good photostability. The obtained silica-coated ZnS:Mn nanoparticles are water-soluble and have fluorescence sensitivity to Cu²⁺ ions. Quenching of fluorescence intensity of the silica-coated nanoparticles allows the detection of Cu²⁺ concentrations as low as 7.3 × 10⁻⁹ mol L⁻¹, thus affording a very sensitive detection system for this chemical species. The possible quenching mechanism is discussed.     

Studies on ZnS Nanoparticles Prepared in Aqueous Sodium Dodecylsulphate (SDS) Micellar Medium

ZnS, a large band gap material, is useful in electro-luminescence and optoelectronic devices. We herein report a method for preparation of nanosized ZnS particles in micellar medium of anionic surfactant sodium dodecylsulphate. The optical properties of the prepared ZnS nanoparticles have been studied by absorption and fluorescence methods. Electron microscopic characterization has evidenced triangular particles, an uncommon observation in the synthesis of nanomaterials. PVC membrane containing nano ZnS dispersions has been prepared and its response as Zn²⁺ ion-selective membrane has been reported.__________From Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 494–499.Original English Text Copyright © 2005 by Debolina Mitra, Indranil Chakraborty, Satya P. Moulik.The text was submitted by the authors in English.     

Understanding the role of surfactants on the preparation of ZnS nanocrystals

We have synthesized surface modified ZnS nanoparticles of size 2-3 nm using non-ionic surfactant-stabilized reverse emulsions. The non-ionic surfactants in the Span series, i.e. sorbitan monolaurate (Span 20) and sorbitan monooleate (Span 80) of hydrophilic-lipophilic balance (HLB) values of 8.6 and 4.3, respectively, have been used for the stabilization of emulsions. The role of these surfactants in controlling the size and properties of the ZnS nanoparticles has been discussed. The triethylamine (TEA) has been proved to be the effective surface modifying (capping) agent for the preparation of free-standing ZnS nanoparticles. The Span 20 with the higher HLB value of 8.6 has been found to be highly suitable in synthesizing TEA-capped ZnS nanoparticles of smaller size and higher photophysical characteristics compared to that of the Span 80 of lower HLB value of 4.3. A mechanism for the formation of TEA-capped ZnS nanoparticles from the surfactant-stabilized reverse emulsions has been proposed.     

Influence of cobalt concentration on structural and optical properties of ZnS quantum dots

ZnS and Co-doped ZnS nanoparticles have been prepared by simple chemical precipitation method. Zinc acetate, sodium sulfide, and cobalt nitrate have been used as precursors for the preparation of Co-doped ZnS quantum dots. The X-ray diffraction results revealed that the undoped and Co-doped ZnS quantum dots exhibit hexagonal structure. The average grain size of quantum dot was found to lie in the range of 2.6–3.8 nm. The surface morphology has been studied using scanning electron microscope. The compositional analysis results confirm the presence of Co, Zn and S in the sample. The optical properties of undoped and Co-doped ZnS quantum dots have been studied using absorption spectra. TEM results show that undoped and Co-doped ZnS nanoparticles exhibit a uniform size distribution with average size of 2.5–3.4 nm.     

Optical and Structural Properties of Doped ZnS Nanoparticles Produced by the Sol-Gel Method

Optical and structural properties of Mn2+-doped ZnS nanoparticles in an organic matrix are experimentally and theoretically studied. The nanoparticles, which were produced by the sol-gel method, are nearly monodisperse with a diameter of approximately 3 nm and show the characteristic orange-red luminescence of Mn2+ centers in a crystalline ZnS matrix. The absorption spectrum of the embedded ZnS nanoparticles is slightly blue shifted and broadened compared to the reference system containing ZnS microparticles. This blue shift is caused by quantum size effects, whereas the broadening is due to defects such as lattice distortions, and vacancies, which are probably located close to the surface in the case of small particles. With increasing temperature the absorption spectra shift to the red and are broadened due to thermal activated diffusion of ions close to the surface. In contrast, the spectral feature of the emission spectra via the Mn2+ center is nearly unchanged compared to the ZnS microparticles. Furthermore, the quantum efficiency is increased and the decay time of the electron-hole pairs is shortened to the nanosecond regime because of the enhanced probability of the electron-hole pairs to see the Mn2+ center. Therefore, the only effect of doping of ZnS nanoparticles with Mn2+ center is the suppression of the relaxation of electron-hole pairs via surface defects generating a highly efficient and fast relaxation of the electron-hole pairs via the Mn2+ center.     

水溶性的CdSe/ZnS纳米微粒的合成及表征

用L-半胱氨酸(Cys)作为稳定剂，合成了水溶性的CdSe/ZnS核壳结构的半导体纳米微粒。吸收光谱和荧光光谱表明，CdSe/ZnS纳米微粒比单一的CdSe纳米粒子具有更优异的发光特性。透射电子显微镜（TEM）、ED和XPS表征了CdSe/ZnS纳米微粒的结构、分散性及形貌。红外光谱证实半胱氨酸分子中的硫原子和氧原子参加了与纳米粒子表面的金属离子的配位作用。     

Synthesis of ZnS nanoparticles from pyridine adducts of zinc(II) dithiocarbamates

Zn(thqdtc)₂, Zn(thqdtc)₂(py) and Zn(thiqdtc)₂(py) (where thqdtc = 1,2,3,4-tetrahydroquinolinecarbodithioate, thiqdtc = 1,2,3,4-tetrahydroisoquinolinecarbodithioate and py = pyridine) have been used as single source precursors for the synthesis of ZnS nanoparticles. The formation of ZnS nanoparticles was achieved by thermal decomposition of the complex under heating in presence of triethylenetetraamine. Transmission electron microscopy, energy dispersive X-ray analysis (EDAX) and powder X-ray diffraction studies were carried out to study the structure and morphology of the nanoparticles. The optical properties of the ZnS nanoparticles were studied by UV–visible and fluorescence emission spectral studies. UV–visible absorption spectral studies indicate a blue shift in the absorption maxima due to the quantum size effect. A single crystal X-ray analysis was carried out for a precursor [Zn(thqdtc)₂].     

Stability and optical properties of dispersions of CdS,ZnS, and Ag<Subscript>2</Subscript>S nanoparticles synthesized in microemulsion

CdS, ZnS, and Ag₂S nanoparticles have been synthesized in microemulsion. The synthesis of nanoparticles depend on the composition of the reaction medium and on the proportions of the precursors. The phase diagram for sedimentation stable dispersion of the nanoparticles synthesized in microemulsion has been determined. The region of the stable nanoparticle dispersion is much smaller than the region of the inverse microemulsion in the n-heptane-AOT-H₂O system. The UV-vis absorption and photoluminescence spectra of the CdS, ZnS, and Ag₂S nanoparticles have been investigated. The size of the nanoparticles increases with an increase in droplet size in the microemulsion, and this shifts the exciton peaks.     

纳米ZnS在KGM-AE高分子模板中的可控制备与光限幅性能研究

设计了一种新的乙酸酐改性魔芋葡苷聚糖(KGM-AE)作为高分子模板，通过调节模板剂的改性度、模板剂溶液浓度以及Zn²⁺离子浓度，探讨了ZnS纳米粒子形成的机理，制备出了大小及形貌可控的纳米ZnS。利用IR、ICP-AES、XRD、TEM等对ZnS结构进行了表征，并测定了纳米ZnS光限幅性能，结果显示纳米ZnS溶液均呈现出明显的光限幅性能。     

Nearly monodispersed ZnS nanospheres: Synthesis and optical properties

ZnS nanoparticles of diameters of 3–4 nm were self-assembled to form dense nanospheres of sizes 100 nm by a colloidal precipitation method using PVP as the stabilizing agent. Studies indicated that the ZnS nanoparticles maintained their individual properties inside the nanospheres. Optical absorption spectra of the samples demonstrated the effect of quantum confinement in the ZnS nanocrystals. Room temperature photoluminescence measurements showed a sharp UV emission at 370 nm, attributed to sulfur vacancies.     

水溶性的CdSe/CdS/ZnS量子点的合成及表征

用L-半胱氨酸盐(Cys)作为稳定剂,合成了水溶性的双壳结构的CdSe/CdS/ZnS半导体量子点。吸收光谱和荧光光谱结果表明,双壳结构的CdSe/CdS/ZnS纳米微粒比单一的CdSe核纳米粒子和单核壳结构的CdSe/CdS纳米粒子具有更优异的发光特性。用透射电子显微镜(TEM)、ED、XRD、XPS和FTIR等方法对CdSe核和双壳层的CdSe/CdS/ZnS纳米微粒的结构、分散性及形貌分别进行了表征。     

ZnS纳米粒子的固相合成及其光学性能

将不同的添加剂引入到低温固相反应中，快速合成了不同尺寸的ZnS纳米粒子。利用TEM表征了产物形貌，利用XRD研究了不同的添加剂、同一添加剂下不同的反应温度、不同反应时间对纳米粒子尺寸的影响。结果表明，不同的添加剂对粒子的尺寸影响较大，其中，十二烷基胺以其特殊的反应方式在较高温度下获得了较小的纳米粒子。另外，在PEG400存在条件下，反应温度和反应时间对粒子尺寸均有一定的影响。同时，对不同条件下所得产物的紫外-可见光吸收性能也进行了测试。     

Synthesis of nanosize metallic and alloyed particles in ordered phases

Functionalized reverse micelles have been used to synthesize Copper and Cobalt nanoparticles differing by their size and shape. They can be also used to synthesize Fe–Cu alloy (at 30% Fe) and composite (at 70% Fe) particles. In the case of Fe–Cu system, the magnetic properties are presented.     

基于ZnS纳米粒子的有机凝胶荧光薄膜的制备及其传感性能

本文首先采用油水界面法制备发光纳米ZnS粒子,再通过物理混合法,将其分散在溶有小分子胶凝剂的有机溶液中,流延于玻璃基质表面,得到ZnS荧光薄膜。实验结果表明,ZnS纳米粒子的平均粒径大小约为200 nm,具有立方晶型结构,并且在杂化薄膜中具有良好的分散性;胶凝剂形成的网络结构对ZnS纳米粒子具有良好的限域效应,表现为稳定的发光性能;气敏实验表明,该杂化膜对挥发性有机单胺和二胺具有灵敏的选择性传感作用;且其灵敏度随着杂化薄膜中ZnS担载量的增大逐渐提高;可逆性实验表明该薄膜对乙二胺蒸汽具有良好的可逆响应性。     

Quantum Size Effects in the Photonics of Semiconductor Nanoparticles

The appearance of quantum size effects in ultradisperse semiconductors, their quantitative analysis, and their effect on the absorption of light and on the photophysical (vibrational relaxation of photogenerated “hot” charge carriers, band-band and “defect” luminescence) and certain primary photochemical processes (the accumulation of excess negative charge by the semiconductor nanoparticles, interphase electron transfer, etc.) are discussed.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 67–87, March–April, 2005.     

Zur Bestimmung des Chloridgehalts von Zinksulfidluminophoren

Zusammenfassung Zur Bestimmung chloridischer Verunreinigungen in Zinksulfidluminophoren wird eine potentiometrische Titrationsmethode vorgeschlagen. Verluste bei der Auflösung der Proben werden durch die Verwendung einer geschlossenen Apparatur vermieden. Die untere Erfassungsgrenze liegt bei etwa 10^–5 g Cl/g ZnS. Die Chloridgehalte von ZnS-Luminophoren, welche mit chloridischen Mineralisatoren hergestellt wurden, ergaben sich zu 10^–5 bis 2,5 · 10^–4 g Cl/g ZnS. Eine Diskussion der Ergebnisse ist an anderer Stelle vorgesehen.

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Summary A potentiometric method is proposed for the determination of impurities of chloride in ZnS phosphors. Any losses during the dissolution of the samples have been avoided by use of a closed apparatus. The lower limit of detection is 10 ppm Cl with a sample size of 1 g. ZnS phosphors prepared with chloride fluxes contain between 10 and 250 ppm Cl per 1 g ZnS. A discussion of the results will appear in another paper.

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Dem Leiter des Bereiches Luminescenzforschung, Herrn Dr. H. Ortmann, danke ich für die Förderung dieser Arbeit.     

Investigation of structural,optical and photoluminescence properties of non-essential amino acid capped zinc sulfide nanoparticles for optoelectronic applications

The objective of the study is to synthesize Zinc Sulphide nanoparticles (ZnS) with different amino acid capping agents in aqueous solution by a simple and cost effective facile chemical co precipitation method and analyze their optoelectronic features. Bio compatibility with less toxic amino acids such as l-Glutamic acid, l-Alanine and l-Asparagine were used as capping agents. These amino acids are from Non-essential amino acid group and its capping behavior suitable for semiconducting nanoparticles like ZnS. The role of non essential amino acids were to stabilize the nanoparticle against agglomeration and also to provide chemical passivation that leads to a significant influence on the improved structural, optical and photoluminescence properties of ZnS nanoparticles. The detailed structural analysis of Zinc Sulphide nano particles revealed by X-ray diffraction method (XRD). From this analysis observed the formation of Cubic ZnS nanoparticles with an average crystallite size in the range of 2.08–2.22 nm.The morphology of the nano particles studied by Field emission scanning electron microscope (FESEM). Particle size examined by Dynamic Light scattering studies (DLS) and which revealed that particle size ranges are below 50 nm. The functional groups of nanoparticles were identified by Fourier transform Infrared spectroscopy (FT-IR) studies. Photoluminescence studies attributed that the considerable emission bands. The UV–Vis analysis disclosed the optical band gap range from 3.77 eV to 3.95 eV.     

Preparation, characterization and application of pyrene-loaded methoxy poly(ethylene glycol)–poly(lactic acid) copolymer nanoparticles

Pyrene-loaded biodegradable polymer nanoparticles were prepared by incorporating pyrene into the polymer nanoparticles formulated from amphiphilic diblock copolymer, methoxy poly(ethylene glycol)–poly(lactic acid) (MePEG–PLA). Their morphological structure and physical properties were characterized by nuclear magnetic resonance (NMR), dynamic light scattering, fluorescence spectroscopy, transmission electronic microscopy and zeta potential measurements. Further, MePEG–PLA nanoparticles containing pyrene as fluorescent marker were administered intranasally to rats, and the distribution of nanoparticles in the nasal mucosa and the olfactory bulb were visualized by fluorescence microscopy. NMR results confirmed that MePEG–PLA copolymer can form nanoparticles in water, and hydrophilic PEG chains were located on the surface of the nanoparticles. The particle size, zeta potential and pyrene loading efficiency of MePEG–PLA nanoparticles were dependent on the PLA block content in the copolymer. Following nasal administration, the absorption of nanoparticles across the epithelium was rapid, with fluorescence observed in the olfactory bulb at 5 min, and a higher level of fluorescence persisted in the olfactory mucosa than that in the respiratory mucosa. These results show that pyrene could serve as a useful fluorescence probe for incorporation into polymer nanoparticles to study tissue distribution and MePEG–PLA nanoparticles might have a great potential as carriers of hydrophobic drugs.     

Synthesis of nanocrystalline zinc sulfide in a non-aqueous system by gamma-irradiation

Summary Gamma-irradiation has been applied to synthesize nanocrystalline ZnS with average size of 38 nm in a non-aqueous system at room temperature by utilizing homogeneous release of S^2- ions from the decomposition of carbon disulfide under γ-irradiation. The structure, morphology, size and optical properties have been studied by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectrometer (UV-visible). The product containing zinc ions and the sulfur source has been characterized as β-ZnS, sphalerite phase, with spherical morphology and with a diameter average size of about 38 nm.The possible mechanism of formation of the product is suggested in accord with the experiment.     

Synthesis of CdS, ZnS and Ag2S nanoparticles stabilized by sodium bis(2-ethylhexyl)sulfosuccinate and polyoxyethylenesorbitan monooleate in aqueous medium

The effect of synthesis conditions (molar ratio between precursors, concentration of surfactants, synthesis temperature) on the size of CdS, ZnS and Ag₂S nanoparticles (NPs) stabilized by sodium bis(2-ethylhexyl)succinate and polyoxyethylenesorbitan monooleate was studied. It was established that stabilization by polyoxyethylenesorbitan results in formation of smaller NPs (～8 nm) as compared to that in the presence of sodium bis(2-ethylhexyl)sulfosuccinate (14–60 nm), which is due to the difference between the adsorption rates of these surfactants onto the surface of synthesized NPs. The resulting aqueous dispersions of CdS, ZnS and Ag₂S NPs exhibit long-term stability to sedimentation. The nanoparticle size increases insignificantly with temperature increasing to 65–70°C and rises abruptly at higher temperatures. The increase in the ratio between concentrations of precursors (sulfide and metal ions) also results in an increase in NP size, allowing one to synthesize nanoparticles of prescribed sizes. The optical properties of the resulting nanoparticles were studied. The positions of the exciton peaks and the luminescence intensity peaks of the dispersions of synthesized CdS and ZnS NPs were determined.