新型Ba_2ZnS_3∶Cu荧光粉的合成及其发光性能

采用双坩埚嵌套高温固相法在950℃下成功地合成了Ba2ZnS3∶Cu荧光粉,探讨了工艺条件和Cu掺杂量对样品发光亮度的影响,用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和荧光分光光度计分别对其结构、形貌和发光性能进行了表征。结果表明:样品具有单一的Ba2ZnS3晶相结构;与Ba2ZnS3基质不同,该荧光粉的激发光谱在近紫外区存在一个从275～350nm的宽激发带,归因于Cu发光中心的吸收;该荧光粉在近紫外光激发下发出明亮的黄光,发射中心波长位于560nm处,是一种良好的黄光材料。     

ZnS/PS复合体系的白光发射

用电化学方法制备了一定孔隙率的多孔硅(PS)样品,然后用脉冲激光沉积(PLD)法以多孔硅为衬底生长一层ZnS薄膜.ZnS的带隙较宽,对可见光是透明的,用适当波长的光激发,PS发射的橙红光可以透过ZnS薄膜,与ZnS的蓝绿光相叠加,得到了可见光区较宽的光致发光带,呈现较强的白光发射.用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnS薄膜的结构性质.结果表明,沉积的ZnS薄膜结晶质量较差,薄膜表面起伏不平,这是由于衬底PS的表面不平整所致.     

ZnS/PS复合体系的白光发射

用电化学方法制备了一定孔隙率的多孔硅(PS)样品,然后用脉冲激光沉积(PLD)法以多孔硅为衬底生长一层ZnS薄膜.ZnS的带隙较宽,对可见光是透明的,用适当波长的光激发,PS发射的橙红光可以透过ZnS薄膜,与ZnS的蓝绿光相叠加,得到了可见光区较宽的光致发光带,呈现较强的白光发射.用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnS薄膜的结构性质.结果表明,沉积的ZnS薄膜结晶质量较差,薄膜表面起伏不平,这是由于衬底PS的表面不平整所致.     

多孔氧化铝模板制备ZnS:Mn纳米晶及其形成机制

采用二次阳极氧化法制备了多孔氧化铝(AAO)模板.利用此AAO模板,采用电化学沉积的方法制备了ZnS:Mn纳米晶.对AAO模板进行了扫描电子显微镜(SEM)测试.结果显示,AAO模板孔洞分布均匀,孔径基本一致.对ZnS:Mn纳米晶进行了SEM测试和荧光光谱(PL)测试,SEM测试结果表明,在AAO模板上沉积了一层ZnS:Mn纳米晶,PL谱结果显示Mn离子成功地掺杂进ZnS.从电负性角度讨论了ZnS:Mn纳米晶的形成机制.     

基于ZnS:Mn~(2+)量子点电致发光器件的制备

以多磷酸钠为分散剂,采用水相共沉淀法制备了Mn2+掺杂的ZnS量子点,通过X射线衍射(XRD)谱、高分辨透射电子显微镜(HRTEM)图像、紫外-可见吸收光谱和光致发光(PL)谱等表征了ZnS:Mn2+量子点的结构、形貌和发光性能;通过对比在空气中干燥前后样品的PL谱,进一步证明了441 nm的峰是属于与硫空位相关的发射。同时,将处理后的样品分散到氯仿中,制备了单层的电致发光(EL)器件,在12 V直流电压的驱动下,在597 nm的位置观测到了Mn2+相关的特征发射。     

ZnS纳米颗粒的制备及其特性研究

用水热法制备了球形纳米ZnS粉体,讨论了反应物摩尔配比、生长时间和反应温度对ZnS纳米晶粒的形貌和尺寸的影响.通过XRD,TEM表征了Zns纳米粉体物相结构和表面形貌.用紫外-可见吸收光谱研究了样品.     

核/壳结构ZnS:Mn/ZnS量子点光发射增强研究

利用水溶性前驱体材料在水性介质中制备了ZnS:Mn和ZnS:Mn/ZnS核/壳结构量子点(QDs,quantum dots),并用X射线衍射(XRD)、光致发光(PL)对ZnS:Mn和ZnS:Mn/ZnS核/壳结构QDs的结构和发光性能进行研究.ZnS:Mn和ZnS:Mn/ZnS QDs XRD谱与标准谱吻合,根据De...     

多种ZnO纳米结构和ZnO/ZnS核壳结构的制备

以Zn(NO3)2.6H2O和CO(NH2)2为原料,采用均匀沉淀法,制备出了棒状、花状、球状纳米氧化锌(ZnO)。将ZnO微球体分散在Na2S溶液中,通过离子替代法,成功制备了ZnO/ZnS核壳结构。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)等测试手段对ZnO纳米结构和ZnO/ZnS核壳结构的晶体结构和表面形貌进行了表征,初步探讨了纳米ZnO和ZnO/ZnS核壳结构的生长机理。根据测试结果得知,ZnO纳米棒呈现六方纤锌矿结构,随着Zn2+浓度逐渐增加,ZnO纳米结构形貌由单分散的棒状聚集成花状,最后演变成球形。ZnO/ZnS复合结构为内核ZnO,外面包覆一层ZnS的核壳结构。所有的纳米ZnO均具有相似的发光特点,ZnO/ZnS核壳结构的发光性能有了很大的改善。     

铜过量对CuxAlO2(1≤x≤1.06)电学性能的影响

采用溶胶.凝胶法制备了铜铁矿结构CuxAlO2陶瓷体材.当1≤x＜1.04时,样品为纯铜铁矿相,当x≥1.04时,样品中出现了微弱的CuO相.样品Cu1.04AlO2的室温电导率比名义组分CuAlO2大了近一个数量级.研究表明,替位式缺陷CuAl(Cu2 离子取代Al3 离子)是导致电导增加的主要受主缺陷机制,Cu过量CuxAlO2的分子式可更准确地表示为Cu(Al1-yCuy)O2.     

铜过量对CuxAlO2(1≤x≤1.06)电学性能的影响

采用溶胶.凝胶法制备了铜铁矿结构CuxAlO2陶瓷体材.当1≤x＜1.04时,样品为纯铜铁矿相,当x≥1.04时,样品中出现了微弱的CuO相.样品Cu1.04AlO2的室温电导率比名义组分CuAlO2大了近一个数量级.研究表明,替位式缺陷CuAl(Cu2+离子取代Al3+离子)是导致电导增加的主要受主缺陷机制,Cu过量CuxAlO2的分子式可更准确地表示为Cu(Al1-yCuy)O2.     

Synthesis and photoluminescence properties of Mn-doped ZnS nanobelts

Mn-doped ZnS nanobelts have been prepared through a thermal evaporation method at 1100℃. The synthesized nanobelts are characterized with X-ray diffraction （XRD）, scanning electron microscopy （SEM）, selected area electron diffraction （SAED）, high-resolution transmission electron microscopy （HRTEM）, and photoluminescence （PL） spectroscopy. The results show that the nanobelts have an uniform single-crystal hexagonal wurtzite structure and grow along [0001 ] direction. Room-temperature photoluminescence reveals that the intrinsic PL of the nanobelts disappears and a new PL peak of the Mn-doped ZnS nanobelts emerges at 575 nm.     

ZnO纳米棒水热法制备及其发光特性研究

采用氢氧化钾(KOH)和二水醋酸锌(Zn(CH3COO)2.2H2O)配制不同浓度的反应溶液,反应过程中加入表面活性剂聚乙二醇(HO(CH2CH2O)13H),在80℃水热反应条件下制备出了优异的ZnO纳米材料。采用扫描电镜(SEM)、X射线衍射(XRD)、荧光光谱仪等测试方法研究了样品的成分、表面形貌和微结构。SEM研究结果显示:样品沿c轴择优生长,径粒分布均匀,长径比高,为六方纤锌矿结构的ZnO纳米棒和菊花状ZnO纳米棒。光致发光谱性能分析显示样品在392 nm附近具有很强的紫外光发射能力,随着反应物浓度的增加,紫外峰发生约3 nm的蓝移,同时,样品还在绿光535 nm附近有较弱的光致发光现象。以上结果表明所制备的ZnO纳米材料具有优异的紫外光发射能力。     

Green synthesis of yellow emitting PMMA–CdSe/ZnS quantum dots nanophosphors

We herein report the fabrication of highly fluorescent yellow emitting nanophosphors using CdSe/ZnS quantum dots (QDs) dispersed in polymethyl methacrylate (PMMA). The QDs were synthesised via a simple, non-phosphine and one pot synthetic method in the absence of an inert atmosphere. The as-prepared nanocrystallites were characterised by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) and photoluminescence spectroscopy, energy-dispersive spectroscopy (EDS), Raman spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM) microscopy. Optical analysis confirmed that the as-synthesised CdSe/ZnS QDs were of high quality with sharp absorption peaks, bright luminescence, narrow emission width and high PL quantum yield (up to 74%). The electron microscope images showed that the QDs are small and spherical in shape with narrow size distributions while the HRTEM micrograph confirmed the high crystallinity of the material. The Raman analysis of the QDs revealed the formation of core–shell structure and the energy dispersive spectroscopy confirmed the presence of the corresponding elements (i.e., Cd, Se, Zn and S). The dispersion of the core–shell QDs in PMMA matrix led to the red-shifting of the emission position from 393 nm in the neat PMMA to 592 nm in the nanocomposite. The fabricated highly fluorescent yellow emitting PMMA–CdSe/ZnS core–shell QDs polymer nanocomposite film display excellent optical properties without loss of luminescence. Furthermore, the as-synthesised organic soluble CdSe/ZnS QDs were successfully converted into highly water soluble QDs after ligand exchange with mercaptoundecanoic acid (MUA) without the loss of their emission properties. The simplicity of the method and the quality of the as-synthesised nanocomposite make it a promising material for the large scale fabrication of diverse optical devices.     

Absence of photocatalytic activity in the presence of the photoluminescence property of Mn–ZnS nanoparticles prepared by a facile wet chemical method at room temperature

Mn-doped ZnS nanoparticles (NPs) were prepared with dopants at various concentrations using a facile, simple and inexpensive wet chemical method at room temperature. The physicochemical properties of NPs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV–vis) and photoluminescence (PL). XRD analysis confirmed formation of ZnS with zinc blende structure and average crystallite size of about 2 nm. TEM analysis revealed formation of hyperfine NPs with rather good uniformity. The room temperature photoluminescence (PL) spectrum of ZnS:Mn²⁺ exhibited an orange-red emission around 600 nm. The maximum PL intensity was observed for 7.5% Mn doped ZnS. The photocatalytic performance of ZnS:Mn²⁺ was successfully demonstrated for degradation of three different model dyes (i.e. Rhodimine B (Rh. B), Bromocresol Green (BCG) and Bromochlorophenol Blue (BCB)). The results revealed that not only was there a remarkable difference in photocatalytic performance of Mn doped ZnS for all three different dyes at different dopant concentrations but also photocatalytic activity was decreased by Mn doping.     

A Ligand Exchange Route to Highly Luminescent Surface‐Functionalized ZnS Nanoparticles and Their Transparent Polymer Nanocomposites

A facile ligand exchange approach for surface‐functionalized ZnS nanoparticles (NPs) with 5‐(2‐methacryloylethyloxymethyl)‐8‐quinolinol (MQ) is described. The MQ–ZnS NPs, with a cubic crystal structure, have the same diameter as ZnS NPs without MQ about 3.0 nm. The MQ–ZnS NPs exhibit strong fluorescence emission at about 500 nm and a high photoluminescence (PL) quantum yield (QY), up to 40%, with a decreasing ratio of MQ to ZnS NPs. The PL decay study reveals that the lifetimes of the different MQ–ZnS NPs with a single exponential decay are in the nanosecond time domain for emission at about 500 nm, which is obviously different from that of ZnS NPs with a biexponential decay for defect‐state emission at 420 nm. The functionalized MQ–ZnS NPs are successfully incorporated into the polymer matrix by in situ bulk polymerization to fabricate transparent bulk nanocomposites with good thermal stability and processability. Transmission electron microscopy results show that the NPs are uniformly dispersed in the polymer matrix without aggregation. The good PL properties of MQ–ZnS NPs are preserved in the bulk nanocomposites. It is observed that the nanocomposites have red‐shifted excitation and emission wavelengths compared with those of both the polymer matrix and MQ–ZnS NPs, possibly because of the cooperative interaction between MQ–ZnS NPs and the polymer matrix with blue emission.     

Optical and electrical properties of copper-incorporated ZnS films applicable as solar cell absorbers

Un-doped and Cu-doped ZnS (ZnS:Cu) thin films were synthesized by Successive Ion Layer Absorption and Reaction (SILAR) method. The UV-visible absorption studies have been used to calculate the band gap values of the fabricated ZnS:Cu thin films. It was observed that by increasing the concentration of Cu²⁺ ions, the Fermi level moves toward the edge of the valence band of ZnS. Photoluminescence spectra of un-doped and Cu-doped ZnS thin films was recorded under 355 nm. The emission spectrum of samples has a blue emission band at 436 nm. The peak positions of the luminescence showed a red shift as the Cu²⁺ ion concentration was increased, which indicates that the acceptor level (of Cu²⁺) is getting close to the valence band of ZnS.     

退火温度对ZnS/PS薄膜的晶体结构和光电性质的影响

用脉冲激光沉积法(PLD)在多孔硅(PS)衬底上生长ZnS薄膜,分别在300℃、400℃和500℃下真空退火。用X射线衍射(XRD)和扫描电子显微镜(SEM)研究了退火对ZnS薄膜的晶体结构和表面形貌的影响,并测量了ZnS/PS复合体系的光致发光(PL)谱和异质结的I-V特性曲线。研究表明,ZnS薄膜仅在28.5°附近存在着(111)方向的高度取向生长,由此判断薄膜是单晶立方结构的-βZnS。随着退火温度的升高,-βZnS的(111)衍射峰强度逐渐增大,且ZnS薄膜表面变得更加均匀致密,说明高温退火可以有效地促进晶粒的结合并改善结晶质量。ZnS/PS复合体系的PL谱中,随着退火温度升高,ZnS薄膜的自激活发光强度增大,而PS的发光强度减小,说明退火处理更有利于ZnS薄膜的发光。根据三基色叠加的原理,ZnS的蓝、绿光与PS的红光相叠加,ZnS/PS体系可以发射出较强的白光。但过高的退火温度会影响整个ZnS/PS体系的白光发射。ZnS/PS异质结的I-V特性曲线呈现出整流特性,且随着退火温度的升高其正向电流增加。     

竹叶状ZnS纳米带的生成与表征

通过无催化物理热蒸发ZnS粉末的方法成功地制备了一种新颖的竹叶状ZnS纳米带。X射线衍射分析和扫描电镜透射电子显微镜,用来对ZnS生长物进行表征,检测显示,所制得的竹叶状纳米带的厚度50～100nm,度宽500～600nm,长度数十微米。透射电镜和选区电子衍射花样表明,制备的纳米带是单晶六角纤锌矿结构。样品的光学性能显示在424nm处有一个强烈的蓝光发射,这种发射是由于氧空位和其他表面态造成的。同时对纳米带的生长机制作了论述。