~(147)Pm激发的ZnS∶Cu,Cl发光粉的研究

以高纯ZnS粉末为基质,采用高温转相、扩散,以及表面涂敷工艺,制得了147Pm激发的ZnS∶Cu,Cl发光粉。分析了ZnS∶Cu,Cl的晶体结构,测量了ZnS∶Cu,Cl的激发光谱、发射光谱、发光亮度。其晶体结构主要是六方纤锌矿型结构,激发光谱峰值波长为341nm,发射光谱峰值波长为513nm,初始发光亮度达到312mcd/m2。由激发光谱的峰值波长341nm推算得到六方ZnS晶体的禁带宽度为3.64eV。分析了147Pm激发的ZnS∶Cu,Cl发光粉的发光寿命,其发光寿命达到5年以上。还探讨了该放射性发光粉的发光机理。147Pm激发的ZnS∶Cu,Cl的稳定发光,实际上是激发过程与复合过程的准平衡。ZnS∶Cu,Cl的绿色发光来源于深施主-深受主对的复合发射。实验结果的分析表明,ZnS∶Cu,Cl中深施主-深受主之间的能级间隔约为2.42eV。     

水热法制备ZnS:Cu,Tm超细X射线发光粉

研究了水热法合成的ZnS: Cu,Tm超细X射线发光粉及其光致发光(PL)和X射线激发发光(X-ray excited luminescence,XEL)光谱特性.200 ℃水热处理12 h直接合成样品的纳米晶粒径约15 nm,尺寸分布窄,分散性好,具有纯立方相的类球形结构.氩气保护下900 ℃退火1 h后的样品存在一定的团聚,但团聚后尺寸为200—600 nm,为超细X射线发光粉,此时样品为纯六方相的类球形为主的结构.所有样品的PL和XEL光谱均为宽带谱.水热法直接合成样品的XEL强度最强时,样品的Cu/Zn,Tm/Cu比值分别为3×10^-4和2.在此比值条件下,900 ℃退火1 h样品的XEL发光最强,此时其两个峰值分别位于453,525 nm.发光强度增强的同时粒径很小,对提高成像系统分辨率非常有意义.通过比较PL光谱与XEL光谱特性,讨论了PL和XEL光谱的发光机理和其不同的激发机理. 关键词： ZnS:Cu Tm 水热法 X射线激发发光     

水热法合成ZnS:Au,Cu超细X射线发光粉

报道了水热法合成的高强度ZnS:Au,Cu超细X射线发光粉及其光致发光(PL)和X射线激发发光(XEL)的光谱特性.200℃水热处理12 h直接合成样品的纳米晶粒约15 nm,尺寸分布窄,分散性好,具有纯立方相的类球形结构.氩气保护下1000℃焙烧1 h后的样品存在一定的团聚,但团聚后尺寸为1～2μm,为超细X射线发光粉,此时样品为纯六角相的类球形为主的结构.所有样品的PL和XEL光谱均为宽带谱,水热法直接合成样品的XEL强度最强时,样品的Cu/Zn,Au/Cu比值分别为3×10-5和2.在此比值条件下,1000℃焙烧1h样品的XEL发光最强,此时其2个峰值分别位于445和513 nm,且与未焙烧前相比强度增强了10倍左右.另外通过比较PL光谱与XEL光谱特性,讨论了PL和XEL光谱的发光机理和其不同的激发机制.     

水热法合成ZnS∶Au,Cu超细X射线发光粉

报道了水热法合成的高强度ZnS∶Au,Cu超细X射线发光粉及其光致发光(PL)和X射线激发发光(XEL)的光谱特性。200℃水热处理12h直接合成样品的纳米晶粒约15nm,尺寸分布窄,分散性好,具有纯立方相的类球形结构。氩气保护下1000℃焙烧1h后的样品存在一定的团聚,但团聚后尺寸为1～2μm,为超细X射线发光粉,此时样品为纯六角相的类球形为主的结构。所有样品的PL和XEL光谱均为宽带谱,水热法直接合成样品的XEL强度最强时,样品的Cu/Zn,Au/Cu比值分别为3×10-5和2。在此比值条件下,1000℃焙烧1h样品的XEL发光最强,此时其2个峰值分别位于445和513nm,且与未焙烧前相比强度增强了10倍左右。另外通过比较PL光谱与XEL光谱特性,讨论了PL和XEL光谱的发光机理和其不同的激发机制。     

ACEL ZnS：Cu发光体内的Cu+迁移与发光的老化

众所周知,Cu对ZnS粉末ACEL是不可或缺和不可替代的。因此维持Cu和它的存在形式在ZnS晶粒中的稳定对ACEL的老化致关重要。Cu⁺在ZnS中具有很高的热扩散率,500℃时热扩散系数已达10^-9cm²/s,是各种杂质中热扩散最强的杂质。900℃时几分钟内即可使7~10μm的ZnS晶粒完全激活。Cu_xS具有很强的离子导电特性,在电场作用下表现出很强的Cu⁺迁移特性。由于Cu_xS具有很高的电导率,可视为导体,因此在外电场中ZnS晶粒内的Cu_xS导电线处于等电位状态。与Cu_xS导电线电位不同的所有等位面不能与Cu_xS相交叉而发生扭曲。由于电流的流动方向必须与等位面垂直,所以导致流过ZnS晶粒的大部分电流被汇集到Cu_xS导线上,并且在导电线上的电流密度分布呈两端弱、中间强的状态。因此在电场作用下Cu_xS导电线及其周边可能达到很高温度。如上所述,Cu⁺迁移是必然的,以此可以很好地解释Fischer所观察到的发光线对的老化现象。     

变色的ZnS：Mn/SrS：Ce/ZnS：Mn薄膜电致发光的研究

利用ZnS:Mn/SrS:Ce/ZnS:Mn多层结构,得到了一种可变颜色的薄膜电致发光器件。研究了这一器件的发射光谱随电压和频率的变化,并讨论了随电压的增加,发射光谱中蓝带和黄带的不同增长的原因,以及在不同电压下,发射光谱中蓝带和黄带随频率变化的不同趋势的原因。观察到随驱动频率的增加,发射光谱出现黄-蓝色位移。     

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。     

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.     

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。     

水热合成ZnS:Cu,Al纳米晶体及其全色发射光谱特性

报道了水热法(200℃)直接合成的ZnS:Cu,Al纳米晶及其发光特性.ZnS:Cu,Al纳米晶粒径约15 nm,尺寸分布窄,分散性好,具有纯立方相的类球形结构.借助X射线能谱法(EDX)和原子吸收光谱仪,研究了样品中S,Zn和Cu的含量并详细研究了光致发光(PL)光谱的特性.结果证明存在大量Zn空缺,Cu离子经过水热处理后已掺入到ZnS基体中.PL光谱特性为:样品的激发谱为宽带谱,337 nm激发时样品发出很强的绿光,370～420 nm之间任意波长激发时,发射谱均为宽带谱,且它们基本重合.表明此材料作为近紫外(370～410 nm)发光二极管((n)-UV(370～410 nm)LED)用荧光粉及全色荧光粉具有很大的应用潜力.样品在375 nm激发下全色宽带发射谱是460,510和576 nm带光谱的高斯叠加.当Cu/Zn,Cu/Al和S/Zn分别为3×10-4,2和3.0时,于室内照明条件下肉眼可观察到白色发光.     

Cu+浓度对ZnS:Cu电致发光材料热释光曲线的影响

以ZnS为基质材料,分别掺入0．05％,0．10％,0．15％,0．20％,0．25％浓度的Cu^＋作为激活剂,制得5个ZnS：Cu电致发光材料样品。通过对样品材料热释光曲线的分析和电致发光亮度的测量,得出结论：当Cu^＋的浓度含量过高,虽然发光中心数目增加,但热释光曲线的强度降低。当Cu^＋掺入浓度为0．15％时,ZnS：Cu电致发光材料的热释光曲线峰值最大,发光亮度最高。     

Thermoluminescence characteristics of inorganically and organically capped ZnS:Cu nanophosphors

ZnS:Cu nanophosphors were prepared by wet chemical methods and characterized by X-ray diffraction (XRD). The typical morphologies of the nanophosphors were investigated by scanning electron microscopy (SEM). The thermoluminescence (TL) properties of inorganically and organically passivated ZnS:Cu nanophosphors were investigated after γ-irradiation using a ⁶⁰Co source at room temperature. The TL glow curve of capped ZnS:Cu showed variation in TL peak and intensity as the capping agent was changed. Amongst the synthesized samples the TL glow curve of SiO₂ capped ZnS:Cu showed the highest TL intensity. It has been found that TL response of SiO₂ capped ZnS:Cu is linear in the range 10-550 Gy. A discussion of the obtained results is also presented.     

Optical Behavior of ZnS:Cu Microcrystals Embedded in Porous Silica Gels

Emission and excitation spectra of ZnS:Cu microcrystals trapped in porous silica xerogels are presented. This system is characterized by intense, long-lived green emission at room temperature. It was observed that this emission was greatly reduced after compressing the xerogel samples.     

Preparation of luminescent ZnS:Cu nanoparticles for the functionalization of transparent acrylate polymers

Highly luminescent ZnS:Cu nanoparticles were synthesized in a coprecipitation route using aqueous salt solutions and thiopropionic acid as stabilizer. The method yields a stable, transparent particle dispersion in water and allows for a good control over particle size in the range of 3-10 nm as determined by dynamic light scattering, small angle X-ray scattering and transmission electron microscopy. Strong luminescence of the nanoparticles was observed under UV-excitation and emission colors could be adjusted in the range of blue to green by varying the Cu-doping concentration. The phase transfer of the ZnS:Cu nanoparticles into non-polar solvents using octylamine was used for a hydrophobic surface functionalization. The hydrophobic particles were used for the fabrication of transparent bulk nanocomposites via in situ-polymerization of dispersions in laurylacrylate. A high transparency of the composite materials, and the luminescence of the ZnS:Cu nanoparticles is retained during the phase transfer and the polymerization process allowing for the integration of a new luminescent functionality into the polymer material.     

Luminescence of nanocrystalline ZnS:Cu

Temperature dependent luminescence and luminescence lifetime measurements are reported for nanocrystalline ZnS:Cu²⁺ particles. Based on the variation of the emission wavelength as a function of particle size (between 3.1 and 7.4 nm) and the low quenching temperature (T_q=135 K), the green emission band is assigned to recombination of an electron in a shallow trap and Cu²⁺. The reduction in lifetime of the green emission (from 20 μs at 4 K to 0.5 μs at 300 K) follows the temperature quenching of the emission. In addition to the green luminescence, a red emission band, previously only reported for bulk ZnS:Cu²⁺, is observed. The red emission is assigned to recombination of a deeply trapped electron and Cu²⁺. The lifetime of the red emission is longer (about 40 μs at 4 K) and the quenching temperature is higher.     

Synthesis, structural and optical characterization of nanocrystalline ZnS:Cu embedded in silica matrix

The synthesis of Cu doped ZnS nanoparticles inside the pore of an inorganic silica gel matrix is presented. The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). X-ray diffraction pattern reveals the crystalline wurtzite phase of ZnS. The existence of silica gel in modeling morphologies of the nanoparticles was characterized using Fourier transform infrared (FTIR) spectrometer. Thickness of the silica shell was also calculated. UV- absorption spectrum shows the appearance of an absorption peak at 273 nm which confirms the blue shift as compared to that of bulk ZnS. The photoluminescence (PL) emission spectrum of the sample showed a broad band in the range 465-510 nm due to the transition from the conduction band edge of ZnS nanocrystals to the acceptor like t₂ state of Cu.