ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450–750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.     

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.     

Synthesis of Bi/Sr doped zinc sulphide by spray pyrolysis technique: Effects of doping tempertures on solar cell application

With the aim of determining the best synthesizing substrate temperature that will improve the optical properties of Bi/Sr doped ZnS thin film, spray coated Bi/Sr doped ZnS thin films were deposited at a varying glass substrate temperature of 200 °C–350 °C using an interval of 50 °C. A constant volume of 40 ml of precursor solution was created by adding 10 ml of each of the following solutions: 0.045 M solution of zinc acetate dihydrate C4H6O4Zn.2H2, 0.1 M solution of thioacetamide CH3CSNH2, 0.02 M solution of bismuth nitrate Bi(NO3)3.5H2O, and 0.07 M solution of Strontium hydroxide Sr(OH).₂. UV–Visible Spectrophotometry, scanning electron microscope (SEM), EDX, X-ray diffraction (XRD), photoluminescence, and Fourier transform infrared (FTIR) were all used to investigate the samples. 53.84 and 193.26% increment in carrier concentration and mobility, a 36.36% and 17.77% reduction in resistivity, and a band gap were obtained at a doping temperature of 300 °C. An open-circuit voltage (Voc) of 0.30 V and a power conversion efficiency of 0.58% were achieved. It was established that a doping temperature of 300 °C on Bi/Sr doped ZnS thin films can be used to lower the band gap of ZnS for solar cell applications.     

XRD and AFM studies of ZnS thin films produced by electrodeposition method

The structure and morphology of ZnS thin films were investigated. ZnS thin films have been grown on an indium tin oxide glass substrate by electrodeposition method using zinc chloride and sodium thiosulfate solutions at room temperature. The X-ray diffraction patterns confirm the presence of ZnS thin films. From the AFM images, grain size decreases as the cathodic potential becomes more negative (from ?1.1 to ?1.3 V) at various deposition periods. Comparison between all the samples reveals that the intensity of the peaks increased, indicating better crystalline phase for the films deposited at ?1.1 V. These films show homogeneous and uniform distribution according to AFM images. On the other hand, XRD analysis shows that the number of ZnS peaks increased as deposition time was increased from 15 to 30 min at ?1.1 V. The AFM images show thicker films to be formed at ?1.1 V indicating more favourable condition for the formation of ZnS thin films.     

Preparation and characterization of nanocomposite ZnO–Ag thin film containing nano-sized Ag particles: influence of preheating,annealing temperature and silver content on characteristics

Nanocomposite ZnO–Ag thin film containing nano-sized Ag particles have been grown on glass substrate by spin-coating technique using zinc acetate dihydrate as starting precursor in 2-propanol as solvent and monoethanolamine as stabilizer. Silver nanoparticles were added in the ZnO sol using silver nitrate dissolved in ethanol-acetonitrile. Their structural, electrical, crystalline size and optical properties were investigated as a function of preheating, annealing temperature and silver content. The results indicated that the crystalline phase was increased with increase of annealing temperature up to 550 °C at optimum preheating temperature of 275 °C. Thermal gravimetric differential thermal analysis results indicated that the decomposition of pure ZnO and nanocomposite ZnO–Ag precursors occurred at 225 and 234 °C, respectively with formation of ZnO wurtzite crystals. The scanning electron microscopy and atomic force microscopy revealed that the surface structure (the porosity and grain size) of the ZnO–Ag thin film (the film thickness is about 379 nm) was changed compared to pure ZnO thin film. The result of transmission electron microscopy showed that Ag particles were about 5 nm and ZnO particles 58 nm with uniform silver nanoclusters. Optical absorption results indicated that optical absorption of ZnO–Ag thin films decreased with increase of annealing temperature. Nanocomposite ZnO–Ag thin films with [Ag] = 0.068 M and [Ag] = 0.110 M showed an intense absorption band, whose maximum signals appear at 430 nm which is not present in pure ZnO thin films. The result of X-ray photoelectron spectroscopy revealed that the binding energy of Ag 3d_5/2 for ZnO–Ag shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between Ag and ZnO.     

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.     

Fabrication of titania nanocoatings on ZnS-type phosphors using the titanium diethanolamine as the precursor in an aqueous solution

The titania nanocoatings on ZnS: Ag, Cl phosphors were successfully obtained by the sol–gel process in an aqueous solution using the titanium diethanolamine complex as the precursor. The titanium diethanolamine complex was prepared with diethanolamine (DEA) and titanium butoxide at the temperature of 120 °C. The nanocoatings synthesized by this technique were uniform and continuous with a thickness of about 10–15 nm, and the photoluminescent (PL) spectra showed that no other luminescent center was introduced. The titania coatings with an appropriate thickness were expected to prevent the degradation of ZnS phosphors in field emission displays (FEDs).     

Synthesis and photoluminescence of ZnS macrolattice

ZnS macrolattice has been synthesized by an ultrasonication-assisted method. It is a face-centred cubic stucture with a lattice constant of about 5.4 nm. Each basis in one unit cell composes of about 1,400 atoms. The d-spacing of the macrolattice is about 10 times to that of ordinary sphalerite crystalline. The new structure can be confirmed by small angle X-ray diffraction, high-resolve TEM and selected area electron diffraction. The emission spectrum of the ZnS macrolattice consists of two main peaks at about 333 and 349 nm, respectively under 236 nm excitation. However, it consists of only one main peak at about 438 nm under 370 nm excitation and only one main peak at about 530 nm under 473 nm excitation. The near band transition about 349 nm demonstrates that the valence band composed of P-type function on the S atom splits to two bands. The conduct band has also split because of many peaks in the excitation spectra. In addition, some defect energy levels must appear in the band gap because blue and green emissions are observed.     

Crack initiation and evolution in vulcanized natural rubber under high temperature fatigue

The nanoscaled crack initiation and evolution of natural rubber under high temperature (85 °C) and small strain amplitude (strain maximum α = 1) fatigue condition were investigated. It was shown by scanning electron microscopy (SEM) images that cracks and cavities with dimensions in nanoscale in the NR matrix appear during the high temperature fatigue. FTIR study indicated that thermal oxidation effect leads to the crosslinking structure destruction. According to the combined analysis of SEM, energy-dispersive X-ray (EDX) spectrometer and small angle X-ray scattering investigations, it was deduced that the destruction of crosslinking structure mainly locates in the vicinity of the ZnS particles with a diameter of 20.2 nm. The ZnS particles are generated as a byproduct in the vulcanization process. Further, the real-time SAXS analysis revealed that the cracks are primarily initiated at relative higher strains (0.7<α < 1) in the region of ZnS aggregations and larger cavities are derived from the enlargement of the cracks.     

ZnS:Mn2+/聚苯乙烯核壳及ZnS:Mn2+中空球的制备和光谱性质

ZnS:Mn2+ polystyrene (PS) core-shell structures and ZnS:Mn2+ hollow spheres were prepared by a sonoehemical deposition approach. Transmission electron micrograph (TEM) studies show that the PS surface is covered by a thin shell consisted of ZnS: Mn2+ nanoparticles with an average size of 9 nm. ZnS: Mn2+ hollow spheres were obtained by heating the core-shell particles in air at 500 ℃ to drive off PS. The photoluminescence spectrum for the emission band of Mn2+ peaked at 540 nm, and a 45 nm blue shift compared to that of corresponding bulk sample, was discussed based on the Mn-O octahedral distortion induced by shell structure.     

Investigation of Structural,Optical and Antibacterial Activity of ZnS Nanoparticles

Zinc sulfide (ZnS) nanoparticles have been successfully prepared by sol–gel precipitation method. The successful formation of cubic structure is ensured by XRD analysis and Debye Scherrer’s equation is used to determine the crystallite size which was found to be 36 nm for ZnS sample annealed at 200 °C. Surface morphology was studied using HRSEM as well as HRTEM and lattice parameters of the samples were obtained from SAED pattern which was found to have close resemblance to values attained from XRD pattern. Further elemental mapping of ZnS nanoparticles is confirmed by EDX studies. Further Kubelka Munk function was employed to estimate the band gap value which was seen lying within 3.58 to 3.64 eV. Further the antibacterial activity of ZnS is investigated and it is found to be an antibacterial agent of Escherichia coli and staphylococcus aurous, further it can be employed as an antimicrobial agent for prohibiting implant linked infections.

     

dl‐Aspartic Acid‐Mediated Hydrothermal Synthesis of β‐ZnS Microspheres and Their Optical Properties

ZnS hollow microspheres were synthesized by a dl ‐aspartic acid mediated hydrothermal route. dl ‐aspartic acid plays an important role as crystal growth soft template, which regulates the release of Zn²⁺ ions for the formation of ZnS hollow spheres. The formation of these hollow spheres was mainly attributed to an Ostwald ripening process. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), UV/Vis spectroscopy (UV), and photoluminescence (PL). The shells of the microspheres were composed of ZnS quantum dots (QDs) with the average size of 2.31 nm. The average microspheres diameter is 0.5–3.5 μm. The shell thickness of the hollow sphere is ≈?300 nm. The optical bandgap energy increased significantly compared to the bulk ZnS material due to the strong quantum confinement effect. Two strong emissions at ≈?425 nm and ≈?472 nm in the photoluminescence (PL) spectrum of ZnS hollow microspheres indicate strong quantum confinement because of the presence of QDs.     

Water-soluble silica-overcoated CdS:Mn/ZnS semiconductor quantum dots

Highly luminescent and photostable CdS:Mn/ZnS core/shell quantum dots are not water soluble because of their hydrophobicity. To create water-soluble quantum dots by an appropriate surface functionalization, CdS:Mn/ZnS quantum dots synthesized in a water-in-oil (W/O) microemulsion system (reverse micelles) were consecutively overcoated with a very thin silica layer ( approximately 2.5 nm thick) within the same reverse micellar system. The water droplet serves as a nanosized reactor for the controlled hydrolysis and condensation of a silica precursor, tetraethyl orthosilicate (TEOS), using an ammonium hydroxide (NH4OH) catalyst. Structural characterizations with transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) indicate that the silica-quantum dot nanocomposites consist of a layered structure. Owing to the amorphous, porous nature of a silica layer, the optical and photophysical properties of silica-overcoated CdS:Mn/ZnS quantum dots are found to remain close to those of uncoated counterparts.     

ssDNA-QDs/GO multicolor fluorescence system for synchronous screening of hepatitis virus DNA

Viral hepatitis is a common infectious disease caused by five viruses (hepatitis virus A, B, C, D, and E). Given the diversity of hepatitis virus, rapid screening and accurate typing of viral hepatitis are the prerequisites for hepatitis therapy. Here, a multicolor fluorescence system was constructed by combining with the multi-color fluorescence properties of CdSe/ZnS quantum dots (QDs, emission wavelengths: 525 nm, 585 nm and 632 nm) and the broad-spectrum fluorescence quenching performance of GO. Taking advantage of the specific recognition of ssDNA modified CdSe/ZnS QDs to target hepatitis virus DNA, the constructed system could effectively distinguish hepatitis A virus DNA (HAV-DNA), hepatitis B virus DNA (HBV-DNA), and hepatitis C virus DNA (HCV-DNA) in a homogeneous solution. Based on the different adsorption property of GO for ssDNA and dsDNA, the fluorescence Forster resonance energy transfer (FRET) process between ssDNA modified QDs and GO could be regulated. The fluorescence signal of the constructed system presented a sensitive response to HAV-DNA, HBV-DNA, and HCV-DNA content in the range of 1.0–192 nM, 8.0–192 nM, and 1.0–128 nM, respectively. The limit of detection for HAV-DNA, HBV-DNA, and HCV-DNA is 0.46 nM, 1.53 nM, and 0.58 nM. The constructed system can be used to screen hepatitis virus DNA in real samples, which provides an alternative strategy for rapid screening and diagnosis of viral hepatitis.     

Optical constants,dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

BiVO₄ thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO₄ target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO₄ target material was prepared through solid-state reaction method by heating Bi₂O₃ and V₂O₅ mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV–Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO₄ thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO₄ thin films have been investigated in detail. Dielectric properties of the BiVO₄ thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO₄ thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO₄.     

Correlation between structural and optical properties of TiO<Subscript>2</Subscript>:ZnO thin films prepared by sol–gel method

We have studied structural and optical properties of thin films of TiO₂, doped with 5% ZnO and deposited on glass substrate (by the sol–gel method). Dip-coated thin films have been examined at different annealing temperatures (350–450 °C) and for various layer thicknesses (89–289 nm). Refractive index, porosity and energy band gap were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.97–2.44, the porosity is in the range of 0.07–0.46 and the energy band gap is in the range of 3.32–3.43. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO₂, doped with 5% ZnO, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 20.23 nm grains). However, the undoped TiO₂ exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range of 8.61–29.48 nm.     

3-巯基丙酸修饰的CdSe/ZnS量子点的合成及测定牛血清白蛋白的研究

以3-巯基丙酸作为修饰剂,在水溶液中合成了稳定的CdSe/ZnS量子点(QDs),透射电镜观察所合成量子点的形貌近似球形,粒径约为25 nm.吸收光谱与荧光光谱的研究表明,CdSe QDs在410 nm处有最大吸收峰,而CdSe/ZnS QDs的最大吸收峰在470 nm处,CdSe/ZnS QDs的荧光强度是CdSe QDs的11倍.考察了缓冲溶液的体积、pH值、反应温度、反应时间对体系荧光的影响.在最佳实验条件下,体系的荧光强度与BSA的浓度呈线性关系,线性响应范围为0.746×10-7～4.48×10-7 mol/L,检出限为3.846×10-10 mol/L.并且CdSe/ZnS QDs荧光强度基本保持稳定,可达两个多月.该方法应用于合成样品的测定,结果满意.     

Effect of Deposition Temperature on Structural and Optical Properties of Chemically Sprayed ZnS Thin Films

Zinc sulfide (ZnS) thin films have been successfully deposited via spray pyrolysis using an aqueous solution of thiourea and zinc acetate onto glass substrate. The effect of varying substrate temperature (150, 200,250 and 300 °C) on structure and optical properties is presented. The films have been characterized by X- ray diffraction (XRD), UV-Vis-NIR spectrometry, photoluminescence (PL) spectroscopy and field emission scanning electron microscopy (FESEM). All the deposited ZnS films exhibit a cubic structure, while crystallinity and morphology are found to depend on spray temperature. PL analysis indicates the presence of violet and green emissions arising from Zn and S vacancies. The value of bandgap of ZnS films is found to decrease slightly with increasing substrate temperature; varying in the range 3.52–3.25 eV, most probably associated with the formation of Zn(S,O) solid solution.     

The effect of different gas atmospheres on the structure,morphology and photoluminescence properties of pulsed laser deposited Y3(Al,Ga)5O12:Ce3+ nano thin films

Luminescent properties of Y₃(Al,Ga)₅O₁₂:Ce³⁺ phosphor powder and thin films were obtained. The phosphor powder was used as target material for Pulsed Laser Deposition (PLD) of the thin films in the presence of different background gases. Excitation peaks for the powder were obtained at 439, 349, 225 and 189 nm and emission peaks at 512 and 565 nm. X-ray diffraction indicated that better crystallization took place for films deposited in a 20 mTorr O₂ atmosphere. Atomic force microscope revealed an RMS value of 0.7 nm, 2.5 nm and 4.8 nm for the films deposited in vacuum, O₂ and Ar atmospheres, respectively. The highest PL intensity was observed for films deposited in the O₂ atmosphere. A slight shift in the wavelength of the PL spectra was obtained for the thin films due to a change in the crystal field. The thickness of the films varied from 120 nm to 270 nm with films deposited in vacuum having the thin layer and those in Ar having the thick layer. The stoichiometry of the powder was maintained in the film during the deposition as confirmed by Rutherford backscattering spectroscopy.     

ZnS nanoparticles capped with watermelon rind extract and their potential application in dye degradation

We report fabrication of stable ZnS nanoparticles (NPs) using a green chemistry concept with watermelon rind extract as capping and stabilizing agent. The cubic structure of the NPs was evidenced by X-ray powder diffraction analysis and electron diffraction studies. Dynamic light scattering and high-resolution transmission electron microscopy studies revealed that the average size of the ZnS NPs was <12 nm. The bandgap of the ZnS nanocrystals was found to be 3.42 eV using ultraviolet–visible (UV–Vis) spectroscopy studies. The energy-dispersive X-ray spectrum of the fabricated ZnS NPs confirmed the elemental Zn and S signals without peaks from any impurities. The biomolecular capping of the ZnS NPs was analyzed using Fourier-transform infrared spectroscopy. An illustrative stabilization mechanism for the ZnS NPs is given using citrulline, a major phytochemical in watermelon rind extract. The obtained ZnS NPs showed good photocatalytic activity towards methylene blue dye degradation.