Adhesion of Colloidal SiO(2) Particles on ZnS-Type Phosphor Surfaces

The interaction between colloidal SiO(2) particles and the surface of ZnS-type phosphors has been studied. The green emitting phosphor ZnS:Cu,Al,Au applied in color television tubes was chosen as a model compound. After the surface of the phosphor particles (d(50)=5.0 μm) was treated in different manners like washing with H(2)O, HCl, or H(2)O(2) as well as precoating with colloidal ZnO particles (d(50)=81 nm), colloidal SiO(2) particles (d(50)=207 nm) were added. Thereafter, the amount of adhered SiO(2) was investigated based on SEM and ESCA analysis. By ESA measurements the surface charge of the colloids and the differently treated ZnS materials was investigated. Based on the experimental results it can be concluded that colloidal SiO(2) particles adhere sufficiently only if ZnO is present on the ZnS surface. The SiO(2) particles are located on top of the ZnO. Finally, the attractive interactions in the system ZnS-ZnO-SiO(2) are discussed in more detail. Copyright 2000 Academic Press.     

Cu／ZnO催化剂上逆向水煤气变换反应反应机理的Monte Carlo模拟

采用Ｍｏｎｔｅ Ｃａｒｌｏ方法模拟了ＣＯ２在Ｕ／ＺｎＯ催化剂上的解离反应，发现在ＣＯ２的解离过程中只有ＣＯ生成；若用Ｈ２对生成的表面吸附氧进行还原，所生成的Ｈ２Ｏ量与前期生成的ＣＯ量相同，说明在Ｃｕ／ＺｎＯ上ＣＯ２和Ｈ２之间发生了化学计量的氧化还原反应，即逆向水煤气反应可能以表面氧化还原反应机理进行。     

Synthesis and spectroscopic investigations of Cu- and Pb-doped colloidal ZnS nanocrystals

A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy.     

Effect of plasmochemical modification on electro-optical and surface properties of zinc sulfide electroluminescent phosphors

Method for improving the brightness of photo- and electroluminescence from ZnS:Cu and ZnS:Cu, Al phosphors by their treatment in a low-temperature gas-discharge plasma was developed. The relationship between the luminescence brightness and spectra and surface properties of the phosphors was studied. The mechanism of processes that occur on the surface and in the bulk of phosphor particles during their bombardment with plasma ions was determined.     

ZnO或K_2O助剂对Cu/SiO_2-Al_2O_3催化剂上丙三醇和苯胺气相催化合成3-甲基吲哚反应的促进作用

研究了ZnO或K2O助剂对Cu/SiO2-Al2O3上丙三醇和苯胺气相催化合成3-甲基吲哚反应的促进作用,采用X射线衍射、透射电子显微镜、H2程序升温还原、NH3程序升温脱附以及热重-差热分析等技术对催化剂进行了表征.结果表明,适量ZnO或K2O的加入可明显提高催化剂的活性、选择性和稳定性,其中以ZnO的促进作用更强.ZnO不仅能增强活性组分Cu与SiO2-Al2O3载体之间的相互作用、提高Cu在载体表面的分散度,而且可有效抑制反应过程中Cu粒子的烧结;而K2O的加入却降低了Cu分散度,但也对反应过程中Cu粒子的烧结有所抑制.ZnO或K2O的加入均不同程度地增加了Cu/SiO2-Al2O3催化剂的弱酸中心数量,从而促进3-甲基吲哚的生成.     

添加表面活性剂两步沉淀法制备甲醇催化剂

采用添加表面活性剂两步沉淀法制备了具有高表面铜相对浓度的超细甲醇合成催化剂。以组成为H2/CO/CO2/N2=66/27/3/4(体积比）的原料气对催化剂进行了活性评价。结果表明,该催化剂比传统并流沉淀法制备的铜基催化剂活性提高47.9%,比两步沉淀法和添加表面活性剂并流沉淀法制备的铜基催化剂活性分别提高9.3%和16.8%。利用SEM、XRD及XPS方法对催化剂的结构、形貌和表面金属组成进行了表征。     

Thermal degradation of acetate-intercalated hydroxy double and layered hydroxy salts

Two hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA) and zinc nickel hydroxy acetate (ZNA), and an analogous layered compound, zinc hydroxy acetate (ZHA), have been prepared by a coprecipitation method. The thermal degradation of these materials was characterized via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and TGA coupled with Fourier transform infrared spectroscopy of gas-phase products, TGA-FTIR. Loss of physisorbed and interlayer H2O was observed between 50 and 150 degrees C for all compounds. Acetic acid, acetone, water, and CO2 were released at high temperatures with relative acetone yields found to be dependent on precursor identity, with very little formed from ZCA compared with ZHA and ZNA. Combined FTIR and XRD analysis of solid residues extracted at different points in the heating profile suggests that ketonization occurs via dissociative adsorption of acetic acid on ZnO surfaces. Nanometer-sized ZnO particles were formed from ZHA, showing slight preferential growth in the ZnO (002) lattice direction, while the presence of a second metal, Ni or Cu, served to retard ZnO crystallite growth at temperatures below 600 degrees C and eliminate preferential growth. ZCA leads to the formation of reduced copper species (metallic copper and Cu2O) when heated to 250 degrees C.     

Cu/ZnO and Cu/ZrO2 interactions studied by contact angle measurement with TEM

A technique of contact angle measurement was applied to the nano-scale oxide-supported metal particles. For Cu supported on ZnO and ZrO2 the angles were found to increase and the work of adhesion to decrease with increasing particle size. Such a trend is interpreted as an effect of negative contact line tension of 2.1 x 10(-9) J m(-1) and 1.0 x 10(-9) J m(-1) in the Cu/ZnO and Cu/ZrO2 system, correspondingly. For the small-sized Cu particles the apparent work of adhesion on ZnO support is higher than that on ZrO2.     

为什么水在金属表面的吸附构型是倾斜的——水在铜、铝表面吸附的量子化学计算

用量子化学从头算方法,分别以原子簇Cu5、Al4、Al10模拟Cu(100)和Al(111)表面,在不同基组水平上,计算了水在两种金属表面上倾斜吸附的势能面,结果表明：当计算基组中不含氧原子的d轨道时,得到水分子在金属表面垂直吸附的构型,这与实验结果不符;当水中氧原子加极化函数时,水分子倾斜吸附时能量较低,得到与实验相符的吸附构型。这说明水中氧原子d轨道在计算中起着关键作用,在成键过程中有着重要影响。     

Particle and surface characterization of a natural illite and study of its copper retention

Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2.     

Luminescence properties of Cu-activated BaZnOS phosphor

Cu-activated BaZnOS was studied for the first time as a novel and efficient blue-emitting phosphor. Under the excitation of UV radiation, the phosphor can efficiently give a blue emission centered at 430 nm, corresponding to the transition from conduction band edge to the excited state of Cu²⁺ in the BaZnOS host. The maximum emission intensity occurs at 0.08 mol% of the Cu doping content for both photoluminescence (PL) and X-ray excited luminescence. The optimized blue-emitting BaZnOS:Cu phosphor has a larger PL intensity than the well-known green-emitting ZnO:Cu and blue-emitting ZnS:Cu phosphors. The excellent luminescence properties are tightly related to the appropriate direct band gap and the unique crystal structure of BaZnOS host. These results strongly indicate that the Cu-activated BaZnOS is a potential material used as a new high-brightness blue phosphor for UV light-emitting diode and display devices.     

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℃。     

Study of the Interaction Products of Some N- and O-Containing Compounds with Highly Dispersed Copper(II) Hydroxide

Composition and structure of the surface compounds formed after interaction between Cu(OH)2 supported on aerosil and bpy, py, PhOH, and H2O2 are studied. The EXAFS and electron spectroscopy methods show the main part of copper ions to remain in a hydroxide surrounding, whose structure does not change practically and does not depend on the nature of the extra ligands used. The colloidal Cu(OH)2 stabilized by starch is found to reveal the same properties as the supported one, but differs by greater sizes of hydroxide particles. Copyright 1999 Academic Press.     

负载型Cu/Al2O3和Cu/ZnO催化剂上CO2加氢的原位FTIR及准原位XPS/HS-LEIS研究

铜基催化剂是工业合成甲醇中常用的催化剂,其主要包含Cu,ZnO,Al2O3三种组分,研究各组分在催化合成甲醇过程中的本质作用及其相互间的协同作用不仅是一个催化基础科学问题,同时对于设计和合成新型高性能的铜基催化剂也有重要指导作用.以往的研究主要针对Cu和ZnO二元组分,关于Al2O3的作用很少有报道,主要观点认为Al2...     

Synthetic architectures of TiO2/H2Ti5O11.H2O, ZnO/H2Ti5O11.H2O, ZnO/TiO2/H2Ti5O11.H2O, and ZnO/TiO2 nanocomposites

Although synthetic investigations of inorganic nanomaterials had been carried out extensively over the past decade, few of them have been devoted to fabrication of complex nanostructures that comprise multicomponents/phases (i.e., composite nanobuilding blocks), especially in the area of structural/morphological architecture. In this work, nanobelts of a protonated pentatitanate (H(2)Ti(5)O(11).H(2)O) were synthesized hydrothermally for the first time. Two technologically important transition-metal-oxides TiO(2) and ZnO were then grown respectively or sequentially onto the surface of the as-prepared nanobelts in aqueous mediums. With a main emphasis on organizational manipulation, the present investigation examines general issues of morphological complexity, synthetic interconvertibility, and material combinability related to fabrication of inorganic nanocomposites. Using this model material system, we demonstrate that complex binary and tertiary composite building blocks of TiO(2)/H(2)Ti(5)O(11).H(2)O, ZnO/H(2)Ti(5)O(11).H(2)O, ZnO/TiO(2)/H(2)Ti(5)O(11).H(2)O, and ZnO/TiO(2) can be architected stepwise in solution. Structural features of these nanocomposites have also been addressed.     

Preparation, microstructure characterization and catalytic performance of Cu/ZnO and ZnO/Cu composite nanoparticles for liquid phase methanol synthesis

Stearate@Cu/ZnO nanocomposite particles with molar ratios of ZnO?∶?Cu = 2 and 5 are synthesized by reduction of the metal-organic Cu precursor [Cu{(OCH(CH(3))CH(2)N(CH(3))(2))}(2)] in the presence of stearate@ZnO nanoparticles. In the case of ZnO?∶?Cu = 5, high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) combined with electron-energy-loss-spectroscopy (EELS) as well as attenuated total reflection Fourier transform infrared (ATR-IR) spectroscopy are used to localize the small amount of Cu deposited on the surface of 3-5 nm sized stearate@ZnO particles. For ZnO?∶?Cu = 2, the microstructure of the nanocomposites after catalytic activity testing is characterized by HAADF-STEM techniques. This reveals the construction of large Cu nanoparticles (20-50 nm) decorated by small ZnO nanoparticles (3-5 nm). The catalytic activity of both composites for the synthesis of methanol from syn gas is evaluated.     

ZnO/Cu2O异质结中深能级表面光伏特性

采用恒电压沉积法在导电玻璃(FTO)上制备了具有三棱柱金字塔状的ZnO/Cu2O异质结薄膜. 利用场发射扫描电镜(FESEM)与X射线衍射仪(XRD)对薄膜的微观形貌和晶体结构进行了表征. 利用表面光电压谱(SPS)、场诱导表面光电压谱(FISPS)和相位谱(PS)研究了单一Cu2O与ZnO/Cu2O异质结薄膜的表面光伏性质. 结果表明, 与单一Cu2O薄膜相比, ZnO/Cu2O异质结薄膜的光伏响应范围拓展到了600~800 nm. 根据SPS, FISPS和PS的作用原理, 拓展部分的光伏响应归因于ZnO/Cu2O异质结中Cu2O层的深能级跃迁, 该跃迁在ZnO-Cu2O界面电场(方向由ZnO指向Cu2O)的作用下得到加强, 同时深能级跃迁产生的电子-空穴对在ZnO-Cu2O界面电场的作用下得到了有效分离和传输.     

ZnO/ZnS core-shell composites for low-temperature-processed perovskite solar cells

Electron transport layers(ETLs)in perovskite solar cells(PSCs)are a key factor to determine the photovoltaic performance.Herein,we demonstrate preparation of Zn O/ZnS core-shell composites through directly synthesizing ZnS on the ZnO nanoparticles in solution.We confirmed the formation of ZnO/ZnS core-shell composites by the uses of X-ray diffraction patterns and the Fourier transform infrared spectroscopy.ZnO/ZnS composites exhibit much homogeneous surface morphology as compared with the bare Zn O as revealed in the scanning electronic microscopy.Moreover,the upper shift of conduction band level upon composition of the Zn O/Zn S film results in a better alignment of energy level,which facilitates cascade charge extraction and thus improves the current density of perovskite solar cell.The shift of conduction band also improves the voltage of the PSCs.The photoluminescence(PL)spectroscopies measured in both steady and transient states were carried out to characterize the charge extraction at the interface between CH_3NH_3PbI_3and the electron transport layers of either ZnO or ZnO/ZnS composite.The ZnO/ZnS composite can more efficiently quench the PL signal of perovskite absorber than bare Zn O resulting in enhanced photocurrent generation in PSCs.     

MAA修饰ZnO量子点及其发光特性

以ZnAc2·2H2O为原料,在乙醇中通过70℃回流4h,得到ZnO前驱物,与LiOH·H2O反应,制备出ZnO.采用巯基乙酸(mercaptoacetic acid,MAA)对所合成的ZnO进行表面修饰,修饰后的产物经SEM和XRD表征,证明获得了物相单一、近似球状、粒径为4.6nm的ZnO量子点.借助紫外-可见和荧光分析,研究了MAA对该量子点的修饰效果,探讨了设置条件下ZnO的发光机理和性质.发现该实验体系之所以产生荧光表面缺陷发射峰消失和激子发射峰明显增加的光学现象,是因为MAA有效地覆盖了ZnO的表面缺陷,并稳定包裹住ZnO粒子.同时还研究了MAA加量、温度、电解质对修饰产物发光性能的影响,发现经MAA修饰后的ZnO量子点具有较强的荧光发光性能、良好的长期陈放稳定性,以及一定的抗电解质影响能力.研究结果对ZnO量子点应用于生物分析具有重要参考价值.     

Regenerable Fe-Mn-ZnO/SiO2 sorbents for room temperature removal of H2S from fuel reformates: performance, active sites, Operando studies

Fe- and Mn-promoted H(2)S sorbents Fe(x)-Mn(y)-Zn(1-x-y)O/SiO(2) (x, y = 0, 0.025) for desulfurization of model fuel reformates at room temperature were prepared, tested and characterized. Sulfur uptake capacity at 25 °C significantly exceeds that of both commercial unsupported ZnO sorbents and un-promoted supported ZnO/SiO(2) sorbents. Sulfur capacity and breakthrough characteristics remain satisfactory after multiple (～10) cycles of adsorption/regeneration, with regeneration performed by a simple and robust heating in air. XRD shows that both "calcined" and "spent" sorbents contain nano-dispersed ZnO, and XPS confirms conversion of ZnO to ZnS. "Calcined" sorbent contains Fe(3+) and Mn(3+) that are reduced to Mn(2+) upon reaction with H(2)S, but not with H(2). Operando ESR is used for the first time to study dynamics of reduction of Mn(3+) promoter sites simultaneously with measuring sulfidation dynamics of the Fe(x)-Mn(y)-Zn(1-x-y)O/SiO(2) sorbent. Fe cations are believed to occupy the surface of supported ZnO nanocrystallites, while Mn cations are distributed within ZnO.