Synthesis, optical, structural and thermal characterization of Mn doped ZnS nanoparticles using reverse micelle method

Mn²⁺­doped ZnS nanoparticles have been prepared through the reverse micelles method using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) as a surfactant. The prepared particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectrometer (FT-IR), UV-vis spectrometry, photoluminescence (PL), electron spin resonance (ESR) and thermogravimetry-differential scanning calorimetry (TG-DSC).     

Optical properties of annealed Mn-doped ZnS nanoparticles

Cysteine stabilized ZnS and Mn²⁺-doped ZnS nanoparticles were synthesized by a wet chemical route. Using the ZnS:Mn²⁺ nanoparticles as seeds, silica-coated ZnS (ZnS@Si) and ZnS:Mn²⁺ (ZnS:Mn²⁺@Si) nanocomposites were formed in water by hydrolysis and condensation of tetramethoxyorthosilicate (TMOS). The influence of annealing in air, formier gas, and argon at 200-1000 °C on the chemical stability of ZnS@Si and ZnS:Mn²⁺@Si nanoparticles with and without silica shell was examined. Silica-coated nanoparticles showed an improved thermal stability over uncoated particles, which underwent a thermal combustion at 400 °C. The emission of the ZnS@Si and ZnS:Mn²⁺@Si passed through a minimum in photoluminescence intensity when annealed at 600 °C. Upon annealing at higher temperatures, ZnS@Si conserved the typical emission centered at 450 nm (blue). ZnS:Mn²⁺@Si yielded different high intensity emissions when heated to 800 °C depending on the gas employed. Emissions due to the Mn²⁺ at 530 nm (green; Zn₂SiO₄:Mn²⁺), 580 nm (orange; ZnS:Mn²⁺@Si), and 630 nm (red; ZnS:Mn²⁺@Si) were obtained. Therefore, with a single starting product a set of different colors was produced by adjusting the atmosphere wherein the powder is heated.     

Synthesis, characterization and optical properties of water-soluble ZnS:Mn nanoparticles

ZnS nanoparticles with Mn²⁺ doping (0.5-20%) have been prepared through a simple chemical method, namely the chemical precipitation method. The structure of the nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-vis spectrometer. The size of the particles is found to be 3-5 nm range. Photoluminescence spectra were recorded for undoped ZnS nanoparticles using an excitation wavelength of 320 nm, exhibiting an emission peak centered at around 445 nm. However, from the Mn²⁺-doped samples, a yellow-orange emission from the Mn²⁺⁴T₁-⁶A₁ transition is observed along with the blue emission. The prepared Mn²⁺-doped sample shows efficient emission of yellow-orange light with the peak emission 580 nm with the blue emission suppressed. The maximum PL intensity is observed only at the excitation energy of 3.88 eV (320 nm). Increase in stabilizing time up to 48 h in de-ionized water yields the enhancement of emission intensity of doped (4% Mn²⁺) ZnS. The correlation made through the concentration of Mn²⁺ versus PL intensity resulted in opposite trend (mirror image) of blue and yellow emissions.     

Synthesis and optical properties of Cr doped ZnS nanoparticles capped by 2-mercaptoethanol

Nanoparticles of Zn_1−xCr_xS (x=0.00, 0.005, 0.01, 0.02 and 0.03) were prepared by a chemical co-precipitation reaction from homogenous solutions of zinc and chromium salts. These nanoparticles were sterically stabilized using 2-mercaptoethanol. Here a study of the effect of Cr doping on structural, morphological and optical properties of nanoparticles was undertaken. Elemental analysis, morphological, structural and optical properties have been investigated by energy dispersive analysis of X-rays (EDAX), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy .EDAX measurements confirmed the presence of Cr in the ZnS lattice. XRD showed that ZnS:Cr nanoparticles crystallized in zincblende structure with preferential orientation along (1 1 1) plane. The average sizes of the nanoparticles lay in the range of 3-6 nm and lattice parameters were in the range of 5.2-5.4 Å. Lattice contraction was observed with an increase of Cr concentration. The particle size and lattice parameters obtained from TEM and SAED images were in agreement with the XRD results. The absorption edge shifted to lower wavelengths with an increase in Cr concentration as per UV-Vis spectroscopy. The band gap energy values were in the range of 3.85-4.05 eV. This blueshift is attributed to the quantum confinement effect.     

Synthesis and photoluminescence of water-soluble Mn-doped ZnS quantum dots

The water-soluble Mn²⁺-doped ZnS quantum dots (Mn:ZnS d-dots) were synthesized by using thioglycolic acid (TGA) as stabilizer in aqueous solutions in air, and characterized by X-ray powder diffraction (XRD), UV-vis absorption spectra and photoluminescence (PL) emission spectroscopy. The sizes of Mn:ZnS d-dots were determined to be about 2 nm using XRD measurements and the UV-vis absorption spectra. It was found that the Mn²⁺⁴T₁ → ⁶A₁ emission intensity of Mn:ZnS d-dots significantly increased with the increase of Mn²⁺ concentration, and showed a maximum when Mn²⁺ doping content was 1.5%. If Mn²⁺ concentration continued to increase, namely more than 1.5%, the Mn²⁺⁴T₁ → ⁶A₁ emission intensity would decrease. In addition, the effects of TGA/(Zn + Mn) molar ratio on PL were investigated. It was found that the peak intensity ratio of Mn²⁺⁴T₁ → ⁶A₁ emission to defect-states emission showed a maximum when the TGA/(Zn + Mn) molar ratio was equal to 1.8.     

Synthesis and characterization of Mn<Superscript>2+</Superscript>-doped ZnS nanoparticles

Mn²⁺-doped ZnS nanoparticles were prepared by chemical arrested precipitation method. The samples were heated at 300, 500, 700 and 900°C. The average particle size was determined from the X-ray line broadening. Samples were characterized by XRD, FTIR and UV. The composition was verified by EDAX spectrum. The hexagonal structure of the sample was identified. The size of the particles increased as the annealing temperature was increased. The crystallite size varied from 5 nm to 34 nm as the calcination temperature increased. At around 700°C, ZnS is converted into ZnO phase due to oxidation. The emission peak of the sample is observed at 300 nm resulting in blue emission. The solid state theory based on the delocalized electron and hole within the confined volume can explain the blue-shifted optical absorption spectra. UV-VIS spectro-photometric measurement shows an indirect allowed band gap of 3.65 eV.      

Synthesis and characterization of Cu doped ZnS nanoparticles using TOPO and SHMP as capping agents

Undoped and Cu²⁺ doped (0.2-0.8%) ZnS nanoparticles have been synthesized through chemical precipitation method. Tri-n-octylphosphine oxide (TOPO) and sodium hexametaphosphate (SHMP) were used as capping agents. The synthesized nanoparticles have been analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), UV-vis spectrometer, photoluminescence (PL) and thermo gravimetric-differential scanning calorimetry (TG-DTA) analysis. The size of the particles is found to be 4-6 nm range. Photoluminescence spectra were recorded for ZnS:Cu²⁺ under the excitation wavelength of 320 nm. The prepared Cu²⁺-doped sample shows efficient PL emission in 470-525 nm region. The capped ZnS:Cu emission intensity is enhanced than the uncapped particles. The doping ions were identified by electron spin resonance (ESR) spectrometer. The phase changes were observed in different temperatures.     

Synthesis and photoluminescence properties of Sm-doped CaWO4 nanoparticles

The Sm³⁺-doped CaWO₄ nanoparticles were synthesized by hydrothermal method. The room temperature photoluminescence (PL) spectra of Sm³⁺-doped CaWO₄ nanoparticles doped with different Sm³⁺ concentrations under 405 nm excitation have been investigated. The PL spectra showed four strong emission peaks at 460, 571, 609, and 653 nm. The first emission peak at 460 nm could be due to a structural defect of the lattice, an oxygen-deficient WO₃ complex. The other three emissions at 571, 609, and 653 nm were due to the f-f forbidden transitions of the 4f electrons of Sm³⁺, corresponding to ⁴G_5/2→⁶H_5/2 (571 nm), ⁶H_7/2 (609 nm), and ⁶H_9/2 (653 nm), respectively. In addition, the optimum Sm³⁺ concentration in CaWO₄ nanoparticles for optical emission was determined to be 1.0%. The Sm³⁺⁴G_5/2→⁶H_7/2 (609 nm) emission intensity of Sm³⁺-doped CaWO₄ nanoparticles significantly increased with the increase of Sm³⁺ concentration, and showed a maximum when Sm³⁺ doping content was 1.0%. If Sm³⁺ concentration continued to increase, namely more than 1.0%, the Sm³⁺⁴G_5/2→⁶H_7/2 emission intensity would decrease. The present materials might be a promising phosphor for white-light LED applications.     

Synthesis and characterization of Ce doped silica (SiO2) nanoparticles

A series of silica doped with different mol percentages of Ce³⁺ concentration was synthesized using a sol-gel method to determine the dependence of photoluminescence wavelengths and intensity on the concentrations of the dopants. Sol-gel glasses are porous networks that have been densified through chemical processing and heat treatment. Rare-earths (REs) are insoluble in silica; due to this insolubility RE ions in silicate glasses enter as network modifiers and compete for non-bridging oxygen in order to complete their coordination. The morphological, structural, thermal and optical properties of the phosphors were characterized by X-ray diffraction, scanning electron microscopy, UV-vis absorption, photoluminescence, thermogravimetric analyses and differential scanning calorimeter. Silica (SiO₂) gel containing Ce³⁺ ions was sputter coated with Au (gold) in order to monitor surface morphology of the samples. The highest emission intensity was found for the sample with a composition of 0.5 mol% Ce³⁺. Cerium doped silica glasses had broad blue emission corresponding to the ²D_3/2-²F_J transition at 448 nm but exhibited apparent concentration quenching above concentrations of 0.5 mol% Ce³⁺.     

Preparation and photoluminescent properties of Ni-doped ZrO2 fibers

Ni²⁺-doped ZrO₂ precursor fibers were prepared via sol-gel technique by dry-spinning method and then heat-treated at different temperatures. The surface of the fibers is smooth with uniform diameter and no cracks have been observed by scanning electron microscopy (SEM). The emission intensity reaches a maximum value at 1 mol% Ni²⁺ because of the concentration quenching. The photoluminescence (PL) relative intensity is apparently intensifying with increasing temperature before 700 °C due to the crystallinity of the ZrO₂ lattice improvement. The PL results show that the typical emission center is at 510 nm excited at 315 nm.     

Studies on the spin Hamiltonian parameters for Mn2+ in the ZnS nanocrystals and bulks

The spin Hamiltonian parameters (zero-field splitting D, g factors and hyperfine structure constants) are theoretically studied for Mn²⁺ in the ZnS nanocrystals and bulks from the perturbation formulae of these quantities for trigonal and cubic tetrahedral 3d⁵ clusters, respectively. The trigonal Mn²⁺ centre in the ZnS nanocrystals is attributed to the impurity–ligand bond angle related to the C₃ axis about 0.39° larger than that (≈109.47°) of an ideal tetrahedron. Almost the same g factors and hyperfine structure constants for the nanocrystals and bulks can be ascribed to similar crystal-field environments (i.e. comparable cubic field parameters Dq), nearly the same covalency (i.e. the equal covalency factors N) and the Mn²⁺ 3d–3s orbital admixture (i.e. the identical core polarisation constants κ) in both systems. The ligand orbital and spin–orbit coupling contributions are found to be important and should be included in the electron paramagnetic resonance analysis in view of significant covalency.     

Synthesis and photoluminescent properties of ZnS:Cd nanoparticles and their phase-transferred nanocomposite with polyvinylpyrrolidone

ZnS:Cd nanoparticles were synthesized in a reverse micelle system by controlling reaction factors with mercaptoacetic acid (MPA) as a surfactant and N,N-dimethylformamide as an oil phase. X-ray diffraction pattern shows that the ZnS:Cd nanoparticles exhibit a cubic structure and its mean size is calculated around 4 nm. With different molar ratios of Zn²⁺/S^2?, the relative intensity of the emission peaks at 400 and 556 nm changes dramatically due to the more sulfur vacancies which resulted from the imbalance of Zn²⁺ and S²⁺ ions. Furthermore, hydrophobic phase-transferred ZnS:Cd nanoparticles were obtained using octylamine, and a highly luminescent phase-transferred ZnS:Cd/polyvinylpyrrolidone (PVP) nanocomposite was prepared by blending the phase-transferred ZnS:Cd with PVP. Infrared absorption suggests that octylamine has been successfully connected with the MPA-coated ZnS:Cd nanoparticles. Unlike the MPA-coated ZnS:Cd which has a very strong emission at 556 nm, the phase-transferred ZnS:Cd has a strong emission at 435 nm, which is ascribed to surface passivation and electron redistribution. In addition, luminescent intensity enhancement was observed for the phase-transferred ZnS:Cd/PVP nanocomposites with various Cd²⁺ doping concentrations.     

Cationic Substitution Sites in Mn2+-doped ZnS Nanoparticles

Mn²⁺-doped ZnS nanoparticles of average size 2.5±0.3 nm have been studied and characterized in the dopant concentration range 0.1–0.3% using XRD, EPR, XPS and photoluminescence methods. The experimental results obtained from these studies indicate that the doping of Mn²⁺ occurs primarily at the T _d sites at low dopant concentration, causing the⁴T₁(G) → ⁶A₁(S) transition to take place in the host lattice; the observed decrease in the intensity of photoluminescence at high dopant concentration is due to the setting in of the strong Mn²⁺–Mn²⁺ interaction arising from cluster formation at the highly distorted sites near the particle surface.An erratum to this article can be found at     

Third-order nonlinear optical properties of thin sputtered gold films

Au films of thickness ranging between 5 and 52 nm were prepared by sputtering on quartz substrates and their third-order nonlinear optical response was investigated by Optical Kerr effect (OKE) and Z-scan techniques using 532 nm, 35 ps laser pulses. All prepared films were characterized by XRD, AFM and UV-VIS-NIR spectrophotometry while their third-order susceptibility χ⁽³⁾ was measured and found to be of the order of 10⁻⁹ esu. The real and imaginary parts of the third-order susceptibility were found in very good agreement with experimental results and theoretical predictions reported by Smith et al. [D.D. Smith, Y. Yoon, R.W. Boyd, Y.K. Cambell, L.A. Baker, R.M. Crooks, M. George, J. Appl. Phys. 86 (1999) 6200].     

Mechanoluminescence and thermoluminescence of Mn doped ZnS nanocrystals

This paper reports the synthesis of ZnS:Mn nanocrystals by the chemical route in which mercaptoethanol was used as the capping agent. The particle size of such nanocrystals was measured using XRD and TEM patterns and was found to be in between 3and 5 nm. It was found that the peak position of TL glow curve and the TL intensity of ZnS:Mn nanoparticles increases as the particle size is decreased. The isothermal decay technique is used to determine the trap-depth. The stability of the charge carriers in the traps increase with the decrease in size of the nanoparticles. The higher stability may be attributed to the higher surface/volume ratio and also to the increase in the trap-depth with decreasing particle size. When a ZnS:Mn nanocrystal is deformed the peak intensity I_m increases linearly with the increasing height of the load. After I_m, initially the ML intensity decreases at a fast rate, and later on it decreases at a slow rate. The ML in ZnS:Mn nanocrystals can be understood on the basis of the piezoelectrically induced electron detrapping model.     

CuO薄膜的三阶非线性光学特性研究

采用脉冲激光沉积技术在Si(100)和熔石英基片上制备了单相的CuO薄膜.通过X射线衍射仪,拉曼光谱仪,场发射扫描电镜和紫外可见光光度计对薄膜的结构,表面形貌和光学性质进行了表征. 场发射扫描电镜结果表明CuO薄膜中晶粒排列致密且分布均匀,其尺寸约为45nm.结合飞秒激光(800nm,50fs)和Z扫描方法测量了薄膜的三阶非线性光学特性,结果表明CuO薄膜具有超快的非线性光学响应且非线性折射率和非线性吸收系数均为负值,其大小分别为-3.96×10^-17 m^{2< 关键词： CuO薄膜 Z-扫描')" href="#">Z-扫描 三阶光学非线性}     

Synthesis and investigation of nonlinear optical properties of semiconductor ZnS nanoparticles

ZnS nanoparticles were prepared by a simple chemical method and using PVP (poly vinylpyrrolidone) as capping agent. The sample was characterized by UV-vis spectrophotometer, X-ray diffraction (XRD) and Z-scan technique. XRD pattern showed that the ZnS nanoparticles had zinc blende structure with an average size of about 2.18 nm. The value of band gap of these nanoparticles was measured to be 4.20 eV. The nonlinear optical properties of ZnS nanoparticles in aqueous solution were studied by Z-scan technique using CW He-Ne laser at 632.8 nm. The nonlinear absorption coefficient (β) was estimated to be as high as 3.2×10⁻³ cm/W and the nonlinear refractive index (n₂) was in order of 10⁻⁸ cm²/W. The sign of the nonlinear refractive index obtained negative that indicated this material exhibits self-defocusing optical nonlinearity.     

Synthesis of Mn-doped ZnS architectures in ternary solution and their optical properties

Mn-doped ZnS sea urchin-like architectures were fabricated by a one-pot solvothermal route in a ternary solution made of ethylenediamine, ethanolamine and distilled water. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was demonstrated that the as-prepared sea urchin-like architectures with diameter of 0.5-1.5 μm were composed of nanorods, possessing a wurtzite structures. The preferred growth orientation of nanorods was found to be the [0 0 2] direction. The PL spectra of the Mn-doped ZnS sea urchin-like architectures show a strong orange emission at 587 nm, indicating the successful doping of Mn²⁺ ions into ZnS host. Ethanolamine played the role of oriented-assembly agent in the formation of sea urchin-like architectures. A possible growth mechanism was proposed to explain the formation of sea urchin-like architectures.     

Mg2+掺杂Zn2SiO4:Mn2+的溶胶-凝胶法合成及真空紫外发光特性研究

采用溶胶-凝胶法（sol-gel method）于不同气氛条件下成功合成了Zn_1.92-xMg_xSiO₄:0.08Mn²⁺（0≤x≤0.12）系列粉末样品.利用X射线衍射(XRD)、光致发光(PL)谱等分析手段对Zn_1.92-xMg_xSiO₄:0.08Mn²⁺系列     

Synthesis, characterization and optical spectroscopy of Eu doped titanate nanotubes

The synthesis of Eu³⁺ doped titania nanotubes was carried out via a hydrothermal method. X-ray diffraction and transmission electron microscope analyses showed that the nanotubes were formed by rolling multilayered titania structure with a length of up to 100 nm. The Eu³⁺-doped nanotubes exhibited strong emission lines associated with the ⁵D₀→⁷F_J (with J from 1 to 4) transition of Eu³⁺ and the differences between the luminescence properties of the precursor powders and the nanotubes were studied at low temperature.