核-壳结构的ZnS:Cu/ZnS纳米粒子的制备及发光性质研究

制备了核-壳结构的ZnS:Cu/ZnS纳米粒子以及普通的没有壳的Cu2 掺杂的ZnS纳米粒子,研究了ZnS无机壳层对ZnS:Cu纳米粒子发光性质的影响.透射电子显微镜、激发光谱和发射光谱的研究表明,后加入的Zn2 离子在已经形成的ZnS核表面生长,形成ZnS壳层;而适当厚度的ZnS壳层可以钝化粒子表面,减少无辐射复合中心的数目,抑制表面态对发光的不利影响,提高ZnS:Cu纳米粒子中Cu2 离子在450 nm左右的发光强度.     

Huygens optical elements and Yagi—Uda nanoantennas based on dielectric nanoparticles

A new class of optical nanoantennas based on dielectric nanoparticles has been proposed and their main characteristics have been analyzed. It has been shown that one dielectric nanoparticle can have the properties of a Huygens element in the optical wavelength range. A Yagi-Uda nanoantenna based on dielectric nano-particles has been studied analytically and numerically.     

Optical and energy-loss spectra of ZnS from ab initio molecular dynamics simulation: Temperature effect

First-principles molecular dynamics simulation has been performed so as to investigate the optical and energy-loss spectra of ZnS. Features such as dielectric function, density of states, reflectivity, refractive index and energy-loss function have been studied. Furthermore, the influence of temperature on the optical properties of interest is reported and discussed.     

ZnS结构相变、电子结构和光学性质的研究

运用第一性原理平面波赝势和广义梯度近似方法, 对闪锌矿结构(ZB)和氯化钠结构(RS) ZnS的状态方程及其在高压下的相变进行计算研究, 分析相变点附近的电子态密度、能带结构和光学性质的变化机理. 结果表明: 通过状态方程得到ZB相到RS相的相变压强值为18.1 GPa, 而利用焓相等原理得到的相变压强值为18.0 GPa; 在结构相变过程中, sp³轨道杂化现象并未消失, RS相ZnS的金属性明显增强; 与ZB相ZnS相比, RS相ZnS的介电常数主峰明显增强, 并向低能方向出现了明显偏移, 使得介电峰向低能方向拓展, 在低能区电子跃迁大大增强. 关键词： 硫化锌 相变 电子结构 光学性质     

Phase diagrams of La1?xCaxMnO3 in double exchange model with added antiferromagnetic and Jahn-Teller interaction

Within the effective mass approximation we theoretically studied the electronic properties of CdSe/ZnS and ZnS/CdSe core-shell quantum dots surrounded by wide-gap dielectric materials. The finite element method is used to obtain the lowest impurity levels and the carrier spatial distribution within the dot. We found that in these zero-dimensional semiconductor structures the electron energy is sensitively dependent on the dielectric constants of the embedding and on the heterostructure geometry. The influence of polarization charges on the binding energy of hydrogenic impurities off-center located is also investigated. The results suggest that in dielectrically modulated nanodots the donor energy can be tuned to a large extent by the structure design, the impurity position and a proper choice of the dielectric media.     

Omni-directional reflection bands in one-dimensional plasma dielectric photonic crystals

In this paper the omni-directional reflection bands in one-dimensional plasma photonic crystal (PPC) have been studied theoretically. We present the study of plasma photonic crystal, having alternate regions of plasma?dielectric (Al₂O₃ or ZnS). Reflectances from this periodic multilayered structure in TE- and TM-modes are calculated for different angles of incidence in microwave region for omni-directional reflection bands. The reflectance is obtained by solving a Maxwell's equation using a translational matrix method. In addition to this, we have also studied the effect of variation of plasma width as well as plasma density on the reflection properties of plasma dielectric photonic crystal in TE- and TM-modes. The study of reflectance bands of such plasma photonic crystals shows that it can be used as omni-directional reflector.     

Ti和Al共掺杂ZnS的电子结构和光学性质

基于密度泛函理论的第一性原理研究Ti和Al单掺杂和(Ti,Al)共掺杂ZnS的能带结构、电子态密度分布、介电函数、光学吸收系数,分析了掺杂后电子结构与光学性质的变化.计算结果表明:掺杂后禁带中引入了新的杂质能级,费米能级进入导带.掺杂改变了ZnS晶体的导电特性,使它表现出金属特性,导电性能增强;与纯净ZnS相比,Ti单掺杂和(Ti,Al)共掺杂ZnS的吸收边均出现明显的红移,且在1.79eV左右出现了一个新峰;而Al单掺杂ZnS的吸收边则发生明显的蓝移,且不产生新的吸收峰.     

Interlevel transitions in core–shell nanodots with dielectric environment

The interlevels absorption in spherical CdSe/ZnS and ZnS/CdSe core–shell nanodots is theoretically investigated taking into account the dielectric environment effect. By considering the joint action of the quantum confinement and polarization charges, the influence of the nanosystem geometry upon the energy spectrum and oscillator strength associated to interlevel transitions is studied. We found that: (1) the low dielectric constant environments significantly blueshift the energy levels; (2) the transition matrix elements and oscillator strengths considerably vary with the core–shell radius ratio; (3) the peak position of the interlevels optical absorption is greatly affected by changing of the shell thickness, but for some geometries the absorption spectrum also becomes sensitive to the environment dielectric properties. The possibility of tuning the resonant energies by using the combined effect of the spatial confinement and dielectric mismatch between the dot and the surrounding medium can be useful in the optoelectronic devices applications.     

ZnS/PVA nanocomposites for nonlinear optical applications

We have found a correlation between ZnS nanocomposite nonlinear optical features and technological processing using electrolytic method. In the earlier researches this factor was neglected. However, it may open a new stage for operation by photovoltaic features of the well known semiconductors within a wide range of magnitudes. The titled nanostructured zinc sulfide (ZnS) was synthesized by electrolytic method. The obtained ZnS nano-crystallites possessed nano-particles sizes varying within 1.6 nm…1.8 nm. The titled samples were analyzed by XRD, HR-TEM, STEM, and nonlinear optical methods such as photo-induced two-photon absorption (TPA) and second harmonic generation (SHG). For this reason the nano-powders were embedded into the photopolymer poly(vinyl) alcohol (PVA) matrices. Role of aggregation in the mentioned properties is discussed. Possible origin of the such correlations are discussed.     

Photostability and Photoinduced Processes in CuInS2/ZnS Quantum Dots and Their Hybrid Structures with Multilayer Graphene Nanoribbons

Optics and Spectroscopy - The photostability of the luminescent properties of CuInS2/ZnS quantum dots (CIS/ZnS QDs) as a monolayer on a dielectric substrate and as part of a hybrid structure with...     

COIL用变形反射镜介质反射膜

 报道COIL激光用变形反射镜的介质反射多层膜实验。在真空镀膜机内制备了膜系Sub/Ag(SiO₂/HfO₂)⁴/air和Sub/Ag(YbF₃/ZnS)³/air, 反射率分别为99.90%和99.87%。在经历109次循环后变形镜物理特性无变化。研究了COIL激光辐射下热畸变和损伤特性。分别在功率密度为1.52kW/cm²和1.18kW/cm²的COIL激光辐照下,这两种膜系的变形镜波前变化为0.37l 和0.54l 。因此对于变形镜1kW/cm²激光功率密度是安全可靠的。     

Zinc sulfide nanoparticles: Spectral properties and photocatalytic activity in metals reduction reactions

Formation of zinc sulfide nanocrystals in aqueous solutions of various polymers has been studied. Spectral properties of ZnS nanoparticles have been investigated, the structure of the long-wave edge of the fundamental absorption band of ZnS nanocrystals has been analyzed. It has been shown that the variation of the synthesis conditions (stabilizer nature and concentration, solution viscosity, ZnS concentration, etc.) allows tailoring of the ZnS nanocrystals size in the range of 3–10 nm. Photochemical processes in colloidal ZnS solutions, containing zinc chloride and sodium sulfite, have been investigated. It has been found that the irradiation of such solutions results in the reduction of Zn(II), the rate of this reaction growing at a decrease in the size of ZnS nanoparticles. Kinetics of photocatalytic Zn(II) reduction has been studied. It has been concluded that two-electron reduction of adsorbed Zn(II) species is the rate-determining stage of this reaction. Photocatalytic activity of ZnS nanoparticles in KAu(CN)₂ reduction in aqueous solutions has been discovered. Spectral characteristics and kinetics of ZnS/Au⁰ nanocomposite formation have been studied. It has been shown that the photoreduction of gold(I) complex is the equilibrium reaction due to the reverse oxidation of gold nanoparticles by ZnS valence band holes.     

ZnS／PS异质结的光学和电学性质

用脉冲激光沉积（PLD）的方法在多孔硅衬底上沉积了ZnS薄膜,并在室温下研究了ZnS／PS异质结的结构、光学和电学性质。X射线衍射仪（XRD）测量结果表明．制备的ZnS薄膜在28．5°附近有一较强的衍射峰,对应于β-ZnS（111）晶向,说明薄膜沿该方向高度择优取向生长。ZnS／PS复合体系的光致发光谱表明,ZnS的发光与PS的发光叠加在一起,在可见光区形成一个450-700nm较宽的光致发光谱带。呈现较强的白光发射。对ZnS／PS异质结I-V,特性曲线的测量结果表明,异质结呈现出与普通二极管相似的整流特性。在正向偏置下,电流密度较大．电压降较低;在反向偏置下,电流密度接近于零。异质结的理想因子的值为77。     

Mn2+, Pb2+共掺杂ZnS纳米材料制备及光致发光

采用聚乙烯基吡咯烷酮(PVP)为表面包覆剂,在室温大气条件下的水溶液中制备了ZnS:Mn,Pb纳米晶。讨论了Mn²⁺和Pb²⁺掺杂量对ZnS纳米发光材料光致发光强度的影响,确定了Mn²⁺和Pb²⁺掺杂量相对于Zn²⁺的最佳的量的比,并对其发光机理进行了初步的探讨。     

核壳型ZnS∶Cu/ZnS量子点的制备及发光性质

本文采用水相合成方法制备了ZnS∶Cu量子点并进行了ZnS壳层修饰,研究了壳层厚度对ZnS∶Cu量子点光学性质的影响,采用TEM、XRD、PL、PLE和UV-Vis等测试方法对其进行了表征。实验结果表明,合成的ZnS∶Cu/ZnS量子点为立方闪锌矿,尺寸分布均匀呈球形,分散性良好,经过壳层修饰平均粒径由2 nm增加到3.2 nm。随着ZnS壳与ZnS核量的比的增加,量子点的PLE激发峰位置和UV-Vis吸收谱线出现红移,也说明了量子点的尺寸增大,证明ZnS在ZnS∶Cu量子点的表面生长,形成了核壳结构的ZnS∶Cu/ZnS量子点。随着壳层增厚,量子点与铜离子发光中心相关的发射峰强度先增大后减小,当壳核比n_s/n_c=2.5时,发光强度达到最大。     

Switching mechanism due to the spontaneous emission cancellation in photonic band gap materials doped with nano-particles

We have investigated the switching mechanism due to the spontaneous emission cancellation in a photonic band gap (PBG) material doped with an ensemble of four-level nano-particles. The effect of the dipole–dipole interaction has also been studied. The linear susceptibility has been calculated in the mean field theory. Numerical simulations for the imaginary susceptibility are performed for a PBG material which is made from periodic dielectric spheres. It is predicted that the system can be switched between the absorbing state and the non-absorbing state by changing the resonance energy within the energy bands of the photonic band gap material.     

Ga掺杂ZnS的电子结构和光学性质

本文基于第一性原理平面波赝势（PWP）和广义梯度近似（GGA）方法,对ZnS闪锌矿结构掺入杂质Ga体系进行结构优化处理. 计算了该体系下ZnS材料的电子结构和光学性质. 详细分析了其平衡晶格常数、能带结构、电子态密度分布和光学性质．结果表明：由于杂质Ga的引入,ZnS体系体积略有膨胀,并在在费米面附近出现了深施主能级,单纯的通过Ga掺杂来实现低阻ｎ型ZnS材料较为困难;由于杂质能级的引入,整个介电峰向低能方向偏移,电子在可见光区的跃迁显著增强．     

Ga掺杂ZnS的电子结构和光学性质简

本文基于第一性原理平面波赝势(PWP)和广义梯度近似(GGA)方法,对ZnS闪锌矿结构掺入杂质Ga体系进行结构优化处理.计算了该体系下ZnS材料的电子结构和光学性质.详细分析了其平衡晶格常数、能带结构、电子态密度分布和光学性质.结果表明:由于杂质Ga的引入,ZnS体系体积略有膨胀,并在费米面附近出现了深施主能级,单纯的通过Ga掺杂来实现低阻n型ZnS材料较为困难;由于杂质能级的引入,整个介电峰向低能方向偏移,电子在可见光区的跃迁显著增强.     

Polarized emission of doped ZnS crystals

Polarization of light emitted in various spectral ranges was studied in two single crystals ZnS:Cu, Cl and ZnS:Ag, Cu, Al. The G-Cu, B-Cu and a small amount of S-A centers have been identified in the ZnS:Cu, Cl crystal by the spectral and polarization methods. The B-Ag band was found in the spectrum of the ZnS:Ag, Cu, Al crystal and its polarization properties investigated. This emission appears to be always polarized perpendicular to the [111]_c axis of the stacking faults independently of the polarization of the exciting light. The symmetry of the B-Ag center is not lower than that of the host lattice. Analogy with G-Cu centers suggests a model for the B-Ag center in which the polarization comes from the symmetry properties of the Ag²⁺ orbitals in the trigonal field of stacking faults.     

Field emission from ZnS nanorods synthesized by radio frequency magnetron sputtering technique

The field emission property of zinc sulphides nanorods synthesized in the thin film form on Si substrates has been studied. It is seen that ZnS nanorod thin films showed good field emission properties with a low-macroscopic turn-on field (2.9-6.3 V/μm). ZnS nanorods were synthesized by using radio frequency magnetron sputtering of a polycrystalline prefabricated ZnS target at a relatively higher pressure (10⁻¹ mbar) and at a lower substrate temperature (233-273 K) without using any catalyst. Transmission electron microscopic image showed the formation of ZnS nanorods with high aspect ratio (>60). The field emission data were analysed using Fowler-Nordhiem theory and the nearly straight-line nature of the F-N plots confirmed cold field emission of electrons. It was also found that the turn-on field decreased with the decrease of nanorod's diameters. The optical properties of the ZnS nanorods were also studied. From the measurements of transmittance of the films deposited on glass substrates, the direct allowed bandgap values have been calculated and they were in the range 3.83-4.03 eV. The thickness of the films was ∼600 nm.