ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively.     

Phase transition between sphalerite and wurtzite in ZnS optical ceramic materials

The phase transition behavior of zinc sulfide (ZnS) ceramics consolidated via pressureless and hot press sintering has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses. Two types of ZnS powders with different particle sizes and morphologies were employed to study the influence of microstructural features of starting powders on the ZnS phase transition behaviors. The present work has revealed that during sintering of ZnS ceramics, the phase transition behavior varies based on the starting powder particle size and magnitude of the applied pressure. It has been demonstrated that smaller particle sizes lead to an increased degree of “early” phase transformation from sphalerite to wurtzite at 1000 °C. Additionally, the application of uniaxial pressure during sintering can lead to a reverse phase transition from wurtzite to sphalerite while simultaneously inducing twinning, resulting in improved optical transmittance and mechanical hardness.     

Fabrication and Optical Behaviors of Core–Shell ZnS Nanostructures

Novel core–shell nanostructures comprised of cubic sphalerite and hexagonal wurtzite ZnS have been synthesized at 150°C by a simple hydrothermal method. The results of HR-TEM and SAED investigation reveal that the cores of hexagonal wurtzite ZnS (ca. 200 nm in average diameter) are encapsulated by a shell of cubic sphalerite ZnS. The FE-SEM image of the nanomaterials shows a surface tightly packed with nanoparticles (<10 nm in size). The optical properties of the fabricated material have been studied in terms of ultraviolet–visible absorption and photoluminescence. Furthermore, a possible mechanism for the fabrication of the core–shell nanostructures has been presented.     

超声辅助均匀沉淀法由前躯体ZnS制备ZnO纳米颗粒及其表征

前躯体ZnS在超声辅助60℃的低温条件下,采用醋酸锌为锌源、硫代乙酰胺为硫源来制备,然后采用在空气中热处理前躯体ZnS的方法制备了直径约为20~40 nm的ZnO纳米颗粒。所得产物分别采用红外光谱(FTIR)、热重-差热分析(TGA-DTA)、X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)、电子能谱(EDS)和荧光光谱(PL)进行表征。实验结果表明,所得产物ZnO为六方纤锌矿结构,且结晶性很好,并且随着超声时间的延长其粒径有所降低。室温PL光谱表明,样品在400~550 nm内有3个较强的荧光发射峰。     

巯基乙酸修饰ZnS纳米颗粒的水相合成及表征

以巯基乙酸(HSCH2COOH, RSH)为表面修饰剂,采用水相合成法制备了表面修饰巯基乙酸的ZnS纳米颗粒. 采用透射电子显微镜、粒度分布、X射线衍射和红外光谱等对ZnS纳米颗粒进行了表征,并对ZnS纳米粒子的制备条件进行了详细的考察. 结果表明,水相合成法的最佳制备条件为：反应pH值8.0, Zn2+:S2-:RSH(摩尔浓度比)为1:1.34:2. 在最佳条件下可制备粒径小(11 nm)且粒度分布窄、分散性好的ZnS纳米粒子,其晶体属面心立方b-闪锌矿结构.     

Synthesis,structural and optical properties of ZnS,CdS and HgS nanoparticles from dithiocarbamato single molecule precursors

Dithiocarbamate complexes of Zn(II), Cd(II) and Hg(II) were synthesize and characterized by elemental analysis, thermogravimetric analysis, UV–Vis, FTIR, ¹H- and ¹³C-NMR spectroscopy. The complexes were thermolyzed at 180°C to prepare HDA-capped ZnS, CdS and HgS nanoparticles. The optical properties of the nanoparticles showed absorptions that are blue shifted with respect to the bulk and narrow emissions. The ZnS nanoparticles are in the cubic phase with average crystallite sizes of 3–5 nm. The CdS nanoparticles consist of a mixture of cubic and hexagonal phases with particle sizes of 8–22 nm, while the HgS nanoparticles are in the cubic phase with average crystallite sizes of 7–14 nm.     

Chlorinated styrene butadiene rubber/ zinc sulfide: novel nanocomposites with unique properties- structural,flame retardant,transport and dielectric properties

Chlorinated styrene butadiene rubber (Cl-SBR)/ zinc sulfide (ZnS) nanocomposites were prepared by a simple two-roll mill mixing technique. The interaction between the ZnS nanoparticles and Cl-SBR was assessed using Fourier transform infrared (FTIR) and UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The dielectric constant, oil resistance, flame retardancy and the transport properties of nanocomposites with aromatic hydrocarbons were also analyzed with special attention to the loading of nanoparticles. The spectroscopic studies revealed the existence of a strong interfacial interaction between rubber chain and ZnS nanoparticles. TEM analysis showed the attachment of ZnS nanoparticles in the chlorinated SBR having nanosize region. SEM and XRD showed the uniform arrangement of nanoparticles in the elastomeric network. The presence of ZnS nanoparticles in the rubber matrix was confirmed through EDX spectroscopy. The thermal stability, flame retardancy and oil resistance properties of the nanocomposites were significantly enhanced by the addition of nanoparticles. Composite with 7 phr loading showed the maximum dielectric constant and beyond this loading, the dielectric property decreased due to the agglomeration of nanoparticles. Transport behavior of nanocomposites in benzene, toluene and xylene were analyzed in the temperature range of 27 to 70 °C. Swelling parameters such as rate constant, sorption, diffusion, and permeation coefficient were estimated. The mechanism of transport of the aromatic solvents in the filled Cl-SBR was found to be following anomalous mode. Temperature dependence of diffusion was used to study the activation parameters of the prepared samples.     

Structural and electrical properties of ZnO:Ag core-shell nanoparticles synthesized by a polymer precursor method

Monodispersed core-shell type ZnO:Ag nanoparticles were synthesized by a polymer precursor method and their structural and electrical properties were reported in detail. The synthesis technique involves a sol-gel type chemical reaction between aqueous solutions of poly-vinyl alcohol (PVA), sucrose and Zn²⁺ salt. The Zn²⁺-PVA-sucrose polymer precursor powders so obtained after the reaction was further explored for the synthesis of ZnO:Ag nanoparticles. The key part of the work lies in the use of polymer coated ZnO nanoparticles as templates to obtain the ZnO core-Ag shell type nanostructures. Structural and spectroscopic analyses of the derived samples were performed with X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the ZnO:Ag nanoparticles consist of distinct peaks corresponding to the hexagonal wurtzite type (space group P63mc) crystal structure of ZnO along with the typical peaks of face centered cubic crystal structure of metallic silver. EDS and XPS analyses confirmed the chemical composition and surface structure of the core-shell nanoparticles. Microstructural analysis revealed the monodispersed platelet shaped ZnO nanoparticles with a thin layer of Ag coating on the surface. UV–visible diffuse reflectance studies revealed the effects of Ag coating on the optical properties of the samples. Detail analysis of the dielectric properties of the samples were performed as a function of frequency (1 Hz to 10 MHz) and temperature (300–528 K) to investigate the electrical conduction mechanism in the samples.     

Chemical synthesis,compositional, morphological,structural, optical and magnetic properties of Zn1−xDyxS nanoparticles

Zn_1−xDy_xS (x=0, 0.02 and 0.04) nanoparticles (NPs) were synthesized by chemical refluxing technique at 100 °C. The prepared samples were analyzed by studying their compositional, morphological, structural, optical and magnetic properties. EDS analysis confirmed the presence of zinc, dysprosium and sulfur in the samples in near stoichiometric ratio. The X-ray diffraction patterns do not show any Dy related peaks for the as-synthesized ZnS nanoparticles. The average diameter of the particles confirmed by TEM studies, was in the range 2–4 nm. Raman studies revealed that all the samples are single phase and exhibit cubic structure. From DRS studies, the band-gap was found to be in the range of 3.85–3.70 eV. All the doped ZnS nanoparticles exhibit ferromagnetic behavior with the Curie temperature higher than room temperature and the magnetic properties of doped ZnS nanoparticles depend on the concentration of Dy ions.     

Antimicrobial and electrical properties of ce- and ni-doped zns nanoparticles obtained by a sonochemical method

In this work, cerium- and nickel-codoped ZnS nanoparticles were obtained by a sonochemical method for 20 min. The nanoparticles were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and microscopy electronic transmission (MET). The electrical properties are estimated through I-V curves and the antimicrobial activity was analyzed against E. coli (gram-negative) and S. aureus (gram-positive) bacteria using the diffusion disk methodology. The diffractograms indicate the obtaining of cubic structure ZnS for the pure sample, whereas the doped samples present the cubic and hexagonal structures of the ZnS. The bandgap reduced from 3.60 to 3.52 eV, for pure and codoped samples. I-V curves indicate an increase in resistivity with doping, being more evident for samples containing cerium. Antimicrobial activity increased as doping occurred, where the codoped sample showed the best results. Even for the low amount of dopant (1 mol%), the antimicrobial activity can be increased by about 50% for the codoped sample, compared to the pure ZnS. Thus, it is known that the doping of ZnS with cerium and nickel provides the stabilization of the hexagonal metastable phase, which acts to restrict electronic mobility and, consequently, improves the antimicrobial response of the material.     

Effect of Zr doping and aging on optical and photocatalytic properties of ZnS nanopowder

A facile single step chemical method is reported for the synthesis of Zr doped ZnS nanopowder and its photocatalytic performance has been studied. The average crystallite size of the synthesized powder estimated from X-ray diffraction (XRD) is nearly 1.1 nm. Transmission electron microscopy (TEM) study shows that nanoparticles are agglomerated having a particle size of nearly 10 nm. The optical band gap of ZnS and Zr-doped ZnS, estimated with the help of UV–visible spectroscopy, is 3.7 and 2.9 eV, respectively. Photoluminescence (PL) spectroscopy indicated the role of lattice defects (vacancy, interstitial defects) on optical emission characteristics of doped ZnS samples. The photocatalytic activity of synthesized samples has also been investigated by degrading methylene blue (MB) dye under UV–visible illumination. The degradation quenching has been observed beyond 0.4 mol% doping of Zr in ZnS with maximum efficiency i.e. 80% in 4 h. Thereafter, the effect of aging is monitored for 1.5 months in which the modified emission properties of defect sites modulated the photocatalytic performance of Zr-doped ZnS sample. Further, with the help of various spectroscopic techniques (absorbance, PL and XPS), a mechanism for the photodegradation of MB dye by using Zr-doped ZnS nanopowder has been proposed.     

Effect of sphalerite to wurtzite crystallographic transformation on microstructure, optical and mechanical properties of zinc sulphide ceramics

Zinc sulphide (ZnS) ceramics synthesized by chemical vapour deposition (CVD) were subjected to post CVD thermal treatments at 850 and 1050 °C in inert atmosphere under pressureless conditions. The samples were found to undergo cubic (sphalerite) to hexagonal (wurtzite) crystallographic transformation at around 1020 °C as confirmed by dilatometric and X-ray diffraction studies. The paper reports the effect of transformation in terms of structure - both crystallography and microstructure. Further, the effects of this transformation on the optical and mechanical properties are also analyzed. The increase in grain size was found to be beneficial for the IR transmission of sphalerite (cubic) phase while, the presence of wurtzite (hexagonal) was found to reduce the transmission significantly. A detailed evaluation of the nature and characteristics of the fracture revealed that the ZnS ceramics failed predominantly by low energy, quasi - cleavage fracture. It was also confirmed that the mechanical properties of this material vary with the extent (area fraction) of quasi - cleavage facets.     

Colloidal Synthesis of ZnS,CdS and Zn x Cd1−x S Nanoparticles from Zinc and Cadmium Thiobiuret Complexes

ZnS, CdS and Zn _x Cd_1?x S nanoparticles were synthesised from the thermolysis of 1,1,5,5-tetra-iso-propyl-4-thiobiuret complexes of Zn and/or Cd in oleylamine. The influence of the different reaction parameters (precursor concentration, growth temperature, reaction time and injection solvent/capping agent combination) on the size, morphology and optical properties of the produced nanoparticles were studied. ZnS nanoparticles with size smaller than 4.3 nm had the cubic phase whereas the particles with size larger than 4.3 nm had a hexagonal crystal structure as suggested by the selected area electron diffraction. Transmission electron microscopy showed the formation of spherical ZnS nanoparticles in addition to few ZnS nanorods only at growth temperature of 280 °C. Powder X-Ray diffraction (p-XRD) showed that the obtained CdS nanoparticles were cubic under all reaction conditions except when dodecanethiol was used as an injection solvent which produced hexagonal CdS. The change in the crystal structure of the CdS nanoparticles was accompanied with a change in morphology from spherical to triangular. Cubic Zn _x Cd_1?x S nanoparticles were obtained under all reaction conditions. Lattice spacing of the Zn _x Cd_1?x S nanoparticles showed a very good agreement with Vegard’s law. The optical properties of the Zn _x Cd_1?x S nanoparticles were highly dependent on the ZnS to CdS precursor ratio and the solvents/capping agent combinations. This in detail study on the relationship of solvent systems (capping agents), thermolysis temperatures, time of reactions and precursors will help in understanding to control the morphology, size of the crystallites and phase of the materials.     

Effects of annealing temperature on some structural and optical properties of ZnO nanoparticles prepared by a modified sol-gel combustion method

Plate-shaped zinc oxide nanoparticles (ZnO-NPs) were successfully synthesized by a modified sol-gel combustion method. Zinc acetate, pure water and isopropanol were used as the starting materials. Acetic acid, diethanolamine and nitric acid were used as the polymerization agent, complexing agent and fuel, respectively. The precursors were formed by mixing aqueous solutions of zinc acetate, acetic acid and diethanolamine. Nitric acid was used to dry the produced gel. The resulting xerogel was annealed at 600 °C, 650 °C and 750 °C for 1 h. The synthesized ZnO-NPs were characterized by X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA) and high-magnification transmission electron microscopy (TEM). The XRD results revealed that the samples produced were crystalline with a hexagonal wurtzite phase. The TEM results showed single-crystal ZnO-NPs with nearly hexagonal plate shapes. The optical properties of the ZnO-NPs were studied by UV-visible and Fourier-transform infrared spectroscopy (FTIR). The UV-vis absorption spectra of the ZnO-NPs indicated absorption peaks in the UV region, which were attributed to the band gap of the ZnO-NPs. The results of the FTIR and UV-vis studies showed that the optical properties of the ZnO-NPs depended on the annealing temperature.     

Enhanced optical properties of ZnS–rGO nanocomposites for ultraviolet detection applications

In this research, fabrication and characterization of ultraviolet (UV) detectors based on zinc sulfide–reduced graphene oxide (rGO) nanocomposite with the focus on the wurtzite structure of zinc sulfide was carried out. The nanoparticles of ZnS were synthesized using chemical deposition method and annealed at 500?°C under flow of argon. X-ray diffraction pattern showed that ZnS with the wurtzite phase was formed at 500?°C. Here, rGO as a unique material with similar properties to graphene such as high electron transport was used in order to improve the optical properties of ZnS. For this purpose, rGO was added to ZnS with three different weight percentages of 5, 10 and 15. Scanning electron microscopy showed that ZnS nanoparticles were well placed in rGO sheets. The UV–visible spectra of the synthesized composites showed that with increasing rGO in composite, light absorption is increased. Photoluminescence (PL) spectra also showed that with increasing the percentage of rGO the generation of electron-hole in composite was increased and PL peak was enhanced. The effect of elevated generation of electron-hole pairs was apparent in optoelectrical properties of fabricated UV detectors based on the sample with higher concentration of rGO in composite. For this sample, the response time was decreased to 310 ms, and the sensitivity to UV irradiation was increased by 7.7 times.     

Evaluation of diffusion mechanism and structural characterizations of ZnS compound during chemical reaction of Zn and S in liquid phase

The present study investigates the diffusion mechanism, morphology and structural characteristics of crystalline zinc sulfide (ZnS) during the reactive diffusion process. The samples with nominal composition of Zn₅₀S₅₀ were prepared via capsulation of high purity of zinc and sulfur followed by the annealing process at various reaction temperatures. The prepared samples were characterized using X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. The structural measurements confirm the formation of zinc sulfide with wurtzite structure during the annealing process at 550°C. The wurtzite allotrope of ZnS is not stable at a high annealing temperature and is transformed to cubic zinc-blende structure. During the annealing process, a continuous layer of ZnS compound forms at the Zn/S interface. Both Zn and S diffuse into the formed ZnS layer and the growth of that occurs mainly toward the Zn side. Under this condition, Kirkendall voids form and accumulate near the ZnS/S interface.     

Effect of Cationic Surfactant Head Groups on Synthesis, Growth and Agglomeration Behavior of ZnS Nanoparticles

Colloidal nanodispersions of ZnS have been prepared using aqueous micellar solution of two cationic surfactants of trimethylammonium/pyridinium series with different head groups i.e., cetyltrimethylammonium chloride (CTAC) and cetyltrimethylpyridinium chloride (CPyC). The role of these surfactants in controlling size, agglomeration behavior and photophysical properties of ZnS nanoparticles has been discussed. UV–visible spectroscopy has been carried out for determination of optical band gap and size of ZnS nanoparticles. Transmission electron microscopy and dynamic light scattering were used to measure sizes and size distribution of ZnS nanoparticles. Powder X-ray analysis (Powder XRD) reveals the cubic structure of nanocrystallite in powdered sample. The photoluminescence emission band exhibits red shift for ZnS nanoparticles in CTAC compared to those in CPyC. The aggregation behavior in two surfactants has been compared using turbidity measurements after redispersing the nanoparticles in water. In situ evolution and growth of ZnS nanoparticles in two different surfactants have been compared through time-dependent absorption behavior and UV irradiation studies. Electrical conductivity measurements reveal that CPyC micelles better stabilize the nanoparticles than that of CTAC.     

XPS and UV–vis studies of Ga-doped zinc oxide nanoparticles synthesized by gelatin based sol-gel approach

Undoped and gallium-doped ZnO nanoparticles, (ZnO NPs) (Zn_1−xGa_xO, x=0.0, 0.03, 0.06, 0.09, 0.12, 0.15), were synthesized by a gelatin-based, sol–gel method. Structural and morphological studies of the resulting products were carried out via X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The XRD results revealed that the sample products were crystalline with a hexagonal wurtzite phase. Furthermore, the TEM images indicated ZnO NPs having approximately spherical shapes, with their particle size distributed over the nanometer range. The XRD and TEM results also showed a decrease in crystallite and particle sizes of NPs from x=0.0 to 0.15. The size-strain plot (SSP) method was employed to study the individual contributions of crystallite sizes and lattice strain to the peak broadening of the undoped and doped ZnO NPs. The effect of doping on the optical band-gap and crystalline quality was also investigated, using ultraviolet-visible (UV–vis), X-ray photoluminescence (XPS), and spectroscopies of the pure and doped ZnO NPs. It was observed that the band-gap and O-vacancies of the doped ZnO NPs were red-shifted in comparison with those of the undoped ZnO NPs in UV–vis and XPS results.     

Micro-/nanostructure evolution of C/SiFeO(N,C) polymer-derived ceramic papers pyrolyzed in a reactive ammonia atmosphere

SiFeO(N,C)-based ceramic papers were prepared via a one-pot synthesis approach by dip-coating a cellulose-based paper template with a polymeric perhydropolysilazane precursor modified with iron(III)acetylacetonate. The preceramic composites were subsequently pyrolyzed in ammonia atmosphere at 500, 700, and 1000°C, respectively, and the characteristics of the three resulting ceramic papers were comparatively investigated. Scanning electron microscopy revealed that in each sample, the morphology of the template is successfully transferred on the ceramic system, with the cellulose-derived fibers being converted to elemental carbon encased by a SiFeO(N,C) coating. Electron transparent cross-sectional samples for transmission electron microscopy (TEM) were prepared from the ceramic papers, employing a standard ultramicrotomy slice cutting procedure, allowing for a detailed characterization of their in situ generated micro-/nanostructure as well as occurring crystalline phases. TEM imaging and diffraction revealed that depending on pyrolysis temperature a different microstructure with a distinct phase assemblage is generated in the polymer-derived ceramic papers. Crystallization from the polymer precursor starts with the precipitation of wüstite (Fe_(1-x)O) nanoparticles at 700°C inside the ceramic coating and secondary ε-Fe_xN at the fiber-coating interface. Upon pyrolysis at 1000°C however, the sample primarily accommodates metallic α-iron nanocrystals that impart ferromagnetic characteristics to the ceramic paper. The results show that the template-assisted polymer-derived ceramic route is a feasible approach in the production of complex ceramic compounds with fibrous paper-like morphology. By adjusting the pyrolysis temperature, microstructure and phase composition of the ceramic paper can be conveniently tailored to the needs of its respective application.     

Synthesis and Luminescence Properties of Core/Shell ZnS:Mn/ZnO Nanoparticles

In this paper the influence of ZnO shell thickness on the luminescence properties of Mn-doped ZnS nanoparticles is studied. Transmission electron microscopy (TEM) images showed that the average diameter of ZnS:Mn nanoparticles is around 14 nm. The formation of ZnO shells on the surface of ZnS:Mn nanoparticles was confirmed by X-ray diffraction (XRD) patterns, high-resolution TEM (HRTEM) images, and X-ray photoelectron spectroscopy (XPS) measurements. A strong increase followed by a gradual decline was observed in the room temperature photoluminescence (PL) spectra with the thickening of the ZnO shell. The photoluminescence excitation (PLE) spectra exhibited a blue shift in ZnO-coated ZnS:Mn nanoparticles compared with the uncoated ones. It is shown that the PL enhancement and the blue shift of optimum excitation wavelength are led by the ZnO-induced surface passivation and compressive stress on the ZnS:Mn cores.