Tb~(3+):ZnO/ZnS荧光粉的结构与发光性能

采用溶胶凝胶-沉淀法制备掺杂Tb~(3+)的ZnO/ZnS绿色荧光粉。通过XRD与IR手段对所制备的绿色荧光粉的结构进行分析。XRD测试结果表明,荧光粉主要以ZnO和ZnS形式存在,其中ZnO属于六方相结构(No.74-0534)、 ZnS属于三角晶结构(No.89-2427)。TEM显示荧光粉呈无规则块状,S的含量为1.85%(原子分数)。IR测试结果表明:绿色荧光粉主要含有Zn-S键、 Zn-O键,其相应吸收峰的位置随退火温度的升高而发生变化。利用激发谱图和发射谱图的分析,探讨荧光粉的发光性能及发光机制。荧光粉制备的最佳退火温度为800℃, Tb~(3+)以磁偶极跃迁为主(~5D_4→~7F_5);掺入ZnS可形成新的能带结构且增大复合几率,从而提高了荧光粉的发光性能,即ZnO/ZnS:Tb~(3+)荧光粉的发光性能强于ZnO:Tb~(3+)荧光粉的发光性能。     

CaSiO3∶Pb,Mn荧光粉的ZnO∶Al包覆研究

以Zn(NO3)2•6H2O和AlCl3•6H2O为原料, 借助CO(NH2)2的水解反应, 采用化学均相共沉淀方法和热处理工艺, 在自制CaSiO3∶Pb, Mn红色荧光粉表面包覆ZnO∶Al, 形成透明导电层. 运用数字万用表和自制测量盒对粉体的电阻率进行测量, 比较了包覆率n(Zn)/n(Ca)、n(Al)/n(Zn), 热处理温度和热处理时间对粉体电阻率的影响; 优化出包覆条件和热处理条件: n(Zn)/n(Ca)=10%, n(Al)/n(Zn)=5%, 75 ℃水解1.5 h, 500 ℃热处理45 min. 对包覆样品进行了室温光致荧光(PL)测量, X射线衍射(XRD)结构分析和透射电子显微镜(TEM)形貌观察. 结果显示, 当n(Zn)/n(Ca)=10%时, 在CaSiO3∶Pb, Mn荧光粉表面形成了连续的ZnO∶Al敷膜, 荧光粉的电阻率明显降低, 并且保持了良好的光致发光性质.     

TiO2对ZnO/ZnS:Eu3+荧光粉发光性能的影响

采用溶胶-凝胶-沉淀法制备ZnO/ZnS/2TiO2:Eu3+荧光粉,并采用X射线衍射(XRD)、红外光谱(IR)、透射电镜(TEM)以及荧光光谱技术对其结构、组成、形貌和发光性能进行表征,探讨其发光机理。结果显示,ZnO/ZnS/2TiO2:Eu3+荧光粉的结构在温度高于600℃时趋于稳定状态,呈不规则结构,由ZnO、TiO2和ZnS构成。IR谱图表明,Ti-O-Ti桥氧键网络结构有利于Eu3+之间的能量传递。荧光光谱分析表明,引入TiO2使Eu3+光谱选律禁阻解除,提高了ZnO/ZnS/2TiO2:Eu3+荧光粉的发光性能,且当nZn(NO3)2:nTiO2=1:2时荧光粉的发光性能最好,612 nm处的5D0→7F2电偶极跃迁为最强发射峰,最佳退火温度为600℃。     

K2GeF6:Mn荧光粉的化学共沉淀合成、结构测定与发光性能研究——介绍一个研究型综合实验

介绍一个大学化学研究型综合实验——K2GeF6:Mn荧光粉的化学共沉淀合成、结构测定与发光性能研究。本实验结合氧化还原与化学共沉淀法制备K2GeF6:Mn荧光粉,借助XRD和SEM对粉体进行结构表征,并利用荧光光谱仪测试分析其发光性能,探究激活剂含量和反应温度对粉体结构与性能的影响,获得可应用于商业白光LED的红色荧光粉。通过该实验的设计与实施,使学生在掌握基本实验技能的同时,能够结合基础理论知识解释实验原理、分析实验现象,并进一步提升学生的科学研究思维和综合运用知识的能力。     

Ti/SnO2+Sb2O3/Fe-PbO2电极电催化性能研究

制备了Ti/SnO2+Sb2O3/Fe-PbO2阳极,采用SEM、XRD和ICP对电极的表面形貌和组成进行了表征.为了考察电极的电催化活性,以苯酚为目标污染物,进行了电催化降解实验.研究结果表明Ti/SnO2+Sb2O3/Fe-PbO2电极电催化降解苯酚模拟废水的最佳工艺条件为:电流密度10mA/cm2、支持电解质Na2SO4浓度0.05 mol/L、温度25℃.在25℃时苯酚的电催化氧化降解反应遵循一级反应动力学规律,并且苯酚的电催化氧化主要是·OH参与的间接氧化,反应过程中电极表面产生的羟基自由基对苯酚的氧化去除起着主要作用.     

氨氮在SnO2-C/Ti电极上的氧化

采用溶胶.凝胶法制备SnO2胶体,以Vulcan XC-72炭黑为载体,合成了SnO2-C(SnO2质量分数20%)电催化剂,利用X射线粉末衍射和扫描电子显微镜对其进行了物相和表面形貌分析.结果表明,VulcanXC-72所负载的SnO2为金红石相,粒径约100 nm.循环伏安法(CV)和阻抗测试(EIS)显示,在氨氮氧化过程中,Vulcan XC-72炭黑作为电催化剂载体,可以提高电催化剂的活性,氨的氧化峰电流从8×10-3 mA上升至1.5×10-2mA;Sb的掺杂有利于提高催化剂活性;电极表面存在膜电阻,膜的组成随施加电位的变化而变化.研究表明.强碱条件下更有利于氨氮的降解.     

Sno2+Sb203中间层的制备条件对Ti/SnO2+Sb2O3/PbO2阳极性能的影响

研究了聚合前驱体制备的SnO2+Sb2O3中间层的焙烧温度、锑含量对Ti/SnO2+Sb2O3/PbO2阳极性能的影响. 用XRD、ESEM和探针法对锡锑中进行了表征,应用阳极寿命快速检测法测定了Ti/SnO2+Sb2O3/PbO2电极在1.0 mol/L H2SO4溶液中的寿命,并用极化曲线和电荷容量表征了锡锑中间层对钛基PbO2阳极性能的影响. 实验结果表明,聚合前驱体制备中间层的焙烧温度和锑含量对Ti/SnO2+Sb2O3/PbO2电极的寿命和性能有显著的影响. 在锡锑中间层的制备温度为500 ℃、n(Sn):n(Sb)=9:1时,制得的Ti/SnO2+Sb2O3/PbO2电极用阳极寿命快速检测法测得的电极寿命达30h,具有良好的稳定性.     

Mn:ZnSe/ZnS核-壳结构纳米晶的无膦法制备和光学性质

以溶于十八烯的Se作为Se前驱体,在无膦条件下制备得到了具有较高量子产率的Mn:ZnSe纳米晶.为了进一步提高纳米晶的稳定性和发光强度,运用外延生长的方法进行ZnS壳层包覆并得到了具有核-壳结构的Mn:ZnSe/ZnS纳米晶.X射线衍射、透射电子显微镜及吸收和荧光光谱测试结果表明,该方法合成的Mn:ZnSe纳米晶以及核-壳结构Mn:ZnSe/ZnS纳米晶均为闪锌矿结构,具有良好的单分散性,包覆ZnS外壳层后量子产率可达到60%以上.此外,对ZnS壳层厚度和Mn2+的掺杂量对Mn:ZnSe/ZnS纳米晶发光强度的影响及发光机制也进行了初步讨论.     

钕改性钛基SnO2/Sb电催化电极的制备及表征

为改善钛基SnO2／Sb电极的电催化性能,采用浸渍法制备了Nd改性钛基SnO2／Sb电极。以活性艳红X-3B为目标有机物,考察电极的电催化性能,对制备温度和Nd掺杂量进行了研究,确定了适宜的制备条件为：热处理温度550℃,Nd掺杂量1.0％。采用SEN,EDS,XRD及XPS等分析方法对所制备电极的表面形貌、元素组成及结构进行分析,发现掺杂Nd可使SnO2粒径变小,有利于电极电催化性能的改善,同时Nd元素的引入可使杂质元素sb,Nd在电极表面涂层富集。Nd改性钛基SnO2／Sb电极表面主要是四方相金红石结构的SnO2晶体,掺杂的sb和Nd分别以Sb^5＋和Nd^3＋的形式存在。电极动电位扫描测试结果表明,Nd改性钛基SnO2／Sb电极具有较高的阳极析氧电位,有利于有机物的阳极氧化降解。     

SnO2的制备及催化臭氧氧化活性

采用沉淀法制备了SnO2催化剂,以SnO2催化臭氧氧化降解糖蜜酒精废水脱色为探针反应,对催化剂的活性进行了评价.采用X射线衍射、红外光谱及热分析(TG-DSC)等技术对催化剂进行表征,研究了沉淀剂及焙烧温度等制备参数对SnO2催化臭氧氧化活性的影响.结果表明,SnO2催化剂对臭氧氧化降解糖蜜酒精废水脱色具有较高的催化活性,反应60 min后,糖蜜酒精废水的脱色率从单独臭氧氧化的43.04%提高到60.24%.沉淀剂对SnO2催化剂的活性影响很大,其中以氨水为沉淀剂制备的SnO2催化剂去羟基化反应程度高,所制得的催化剂活性最大.催化剂适宜的焙烧温度为723 K.SnO2吸附吡啶的红外光谱表明,催化剂表面存在L酸中心.臭氧在SnO2表面吸附的红外光谱表明,通过臭氧的末端氧原子与表面羟基及L酸中心成键,生成的活性氧可氧化降解糖蜜酒精废水.     

Effect of nanoscaled SnO2 coating on ZnS:Mn phosphors under electron irradiation

The luminescence properties of SnO₂-coated ZnS:Mn phosphors are investigated. In the case of photoluminescence, emission intensities show little change when SnO₂ is coated on the surface of ZnS:Mn, while in the case of cathodoluminescence (CL), emission intensities vary depending on excitation energies. In order to determine the luminescence behaviors, surface analyses of the phosphors were performed. Auger electron spectroscopy showed that the width of the SnO₂ layer on the ZnS:Mn phosphor was saturated at approximately 120 nm. Also, X-ray photoelectron spectroscopy indicated that the SnO₂ layers are well formed and saturated when the molar ratios of Sn/Zn are larger than 0.005. These results suggest that the changes in the CL emissions can be attributed to a lowering of the junction barrier.     

Poly(MAA-Mn) for Triple-Layer Structure Synthesis of ZnS/ZnS:Mn/SiO2 Phosphors

Methacrylic acid (MAA) was used as a manganese carrier to prepare ZnS/MAA-Mn particles, and ZnS/ZnS:Mn phosphors were formed from ZnS/MAA-Mn by ion substitution through heat treatment. After silica coating on surface by chemical precipitation method with tetraethyl orthosilicate (TEOS), ZnS/ZnS:Mn/SiO₂ phosphors were prepared successfully as a new core/shell structure compound. The thickness of layers was controlled by adjusting concentrations of manganese (II) acetate (Mn(CH₃COO)₂) and TEOS. Structure, morphology, and composition of prepared phosphors were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Photoluminescence (PL) properties of ZnS with different Mn²⁺ content were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of silica coating and Mn²⁺ activator doping. As a result, the structure of two layers could be observed, and optimum composition of ZnS/ZnS:Mn/SiO₂ structure was also obtained.     

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.     

ZnS∶Co半导体量子点的制备及其光电化学性质

采用低温水热技术,分别以柠檬酸(CA)和巯基丙酸(MPA)为稳定剂,在70℃的水相中合成了单分散的,粒子尺寸约为4 nm的ZnS∶Co半导体量子点.研究了稳定剂、Co2+掺杂剂及其掺杂量对掺杂量子点发光性能和结构的影响.XRD结果表明,Co2+离子主要掺杂在量子点表面,对主体ZnS晶格没有影响.当采用MPA为稳定剂,掺杂量为5%(摩尔分数)时,掺杂量子点的荧光发射强度最高;而同样掺杂量下采用CA为稳定剂时,量子点的荧光发射强度有所下降.循环伏安研究显示,与空白ZnS量子点相比,Co2+离子的掺杂在ZnS的禁带中形成杂质能级,相应地,ZnS∶Co量子点的吸收边发生红移.与未掺杂ZnS量子点相比,掺杂量子点具有较少的表面非辐射复合中心,因而荧光发射强度显著提高.     

Facile synthesis of highly luminescent Mn-doped ZnS nanocrystals

Manganese-doped zinc sulfide quantum dots (Mn:ZnS d-dots) with high optical quality, pure dopant emission of 55-65% photoluminescence quantum yield, were synthesized in octadecene media with generic starting materials, namely, zinc (manganese) carboxylic acid salts, S powder, and dodecanethiol (DDT) based on a "nucleation doping" strategy. The optical properties and structure of the obtained Mn:ZnS d-dots have been characterized by UV-vis, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The resulting nearly monodisperse d-dots were found to be of spherical shape with a zinc-blende crystal structure. The influences of various experimental variables, including the reaction temperature for the MnS core nanocluster and ZnS host material, the amount of octadecene (ODE)-S, DDT, as well as Zn/Mn ratio have been systematically investigated. The use of DDT as capping ligand ensured the reproducible access to a stable small-sized MnS core. This paves the way for reproducibly obtaining highly luminescent d-dots. Programmed overcoating temperature for growth of ZnS shell was employed to realize balanced diffusion of the Mn ions in the d-dots.     

Synthesis and characterization of high-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) luminescent nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.     

硫化锌与硫化锌/氧化锌异质结纳米线的化学气相沉积法制备与表征

介绍一种利用石墨还原快速制备大量硫化锌纳米线的方法,并分别合成了超晶格型、双轴型、核/壳型的硫化锌/氧化锌异质结纳米线。所合成的硫化锌纳米线存在六方纤锌矿和立方闪锌矿两种晶型,纳米线长度达几十微米,直径在20-50 nm,直径均匀且产量很高。在具有双轴型的硫化锌/氧化锌异质结中,首次发现具有超结构特征的氧化锌。HRTEM分析表明,硫化锌/氧化锌超晶格异质结界面为ZB-ZnS(111)∥ZnO(0001),而核/壳型异质结界面为W-ZnS(0001)∥ZnO(0001),这三个晶面分别为各自晶体的极性面,即所合成的硫化锌/氧化锌异质结中极性面相互平行。对ZnS 和ZnS/ZnO 异质结的生长机制进行了探讨,并对硫化锌纳米线与硫化锌/氧化锌异质结的光学性质进行了分析。     

柔性透明自支撑氧化锡锑电纺纳米纤维膜的制备与表征

以四氯化锡和三氯化锑为前驱体,通过静电纺丝技术制备了柔性透明的自支撑氧化锡锑(ATO)纳米纤维膜.研究结果表明,该柔性ATO纤维膜具有四方相金红石晶体结构,且呈无规的纤维网状分布.当前驱体煅烧温度分别为520℃和700℃时,纤维的平均直径为200和150 nm;组成纤维的颗粒的平均粒径为10和19 nm;可见光透过率为72%和80%;电阻率为5.23和2.20Ω·cm.该自支撑ATO纳米纤维膜还显示出优异的柔韧性,在弯曲500次后其电阻率基本不变.     

(Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties

(Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.