Ti O2纳米管阵列基底退火温度对CdSe/Ti O2异质结薄膜光电化学性能的影响

通过电化学沉积法以TiO2纳米管阵列(TNTs)为基底制备CdSe/TiO2异质结薄膜。研究TiO2纳米管阵列基底不同退火温度(200,350,450,600℃)对CdSe/TiO2异质结薄膜光电化学性能的影响。采用SEM,XRD,UV-Vis,电化学测试等方法对样品的微观形貌、晶体结构、光电化学性能等进行表征。结果表明:立方晶型的CdSe纳米颗粒均匀沉积在TiO2纳米管阵列管口及管壁上。TiO2纳米管阵列未经退火及退火温度为200℃时,为无定型态,在TiO2纳米管阵列上沉积的CdSe纳米颗粒数量少,尺寸小,异质结薄膜光电性能较差,光电流几乎为零。随着退火温度升高到350℃,TiO2纳米管阵列基底开始向锐钛矿转变;且沉积在TiO2纳米管上的CdSe颗粒增多,尺寸增大,光电化学性能提高。退火温度为450℃时光电流值达到最大,为4.05mA/cm^2。当退火温度达到600℃时,TiO2纳米管有金红石相出现,CdSe颗粒变小,数量减少,光电化学性能下降。     

TiO2/CuInS2复合纳米棒阵列的制备及其光电性能

采用两步溶剂热法在氧化氟锡(FTO)导电玻璃基底上制备了CuInS2敏化TiO2纳米棒阵列复合薄膜光阳极.利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了复合阵列薄膜的晶体结构和表面形貌,同时采用紫外可见吸收分光光度计(UV-Vis)及光电流电压(I-V)曲线研究了CuInS2敏化TiO2纳米阵列薄膜的光学及光电化学性质.研究结果表明,TiO2纳米棒阵列薄膜被CuInS2敏化后在可见光区的吸收有明显的增强.在模拟太阳光照射下(100 mW/cm2),利用这种复合薄膜作为光阳极组装的量子点敏化太阳能电池的开路电压为0.29 V,短路电流密度为0.15 mA/cm2,具有一定的光电转换能力.     

氮掺杂SrTiO3/TiO2纳米棒异质结的制备及光催化活性

通过水热反应和直接浸渍法在FTO导电玻璃上制备得到了高度有序的氮掺杂SrTiO3/TiO2纳米棒异质结阵列(N-STO/TNR),利用扫描电子显微镜(SEM),X射线衍射(XRD)和X射线光电子能谱(XPS)对其表面形貌,晶体结构和元素价态进行了分析。同时,采用荧光光谱(FL)、紫外可见漫反射光谱(UV-DRS),电化学阻抗谱(EIS)和莫特肖特基(MS)对异质结的光电性能进行了测试。最后以甲基橙为模拟污染物,考察了异质结材料在可见光下的光催化活性。结果表明,SrTiO3/TiO2异质结构能有效的分离光生载流子,同时N元素的掺杂将异质结的光谱响应范围扩展到可见光区,得益于半导体复合和能级修饰策略的协同增强效应,N-STO/TNR展现出优异的光电性能,N-STO/TNR的光催化效率是未改性的TNR样品的5.7倍。     

CdS_xSe_(1-x)包覆TiO_2纳米棒壳核结构的制备及其在杂化太阳电池的应用

采用水热法在掺氟的SnO2透明导电玻璃(FTO)基底上制备了金红石型的TiO2纳米棒阵列;然后采用电化学方法在TiO2纳米棒阵列上沉积不同厚度的CdSxSe1-x纳米晶,形成了CdSxSe1-x纳米晶包覆TiO2纳米棒的CdSxSe1-x/TiO2壳核结构;利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)、紫外-可见漫反射吸收光谱(UV-Vis DRS)等对其形貌、结构组成等进行了分析和表征,结合循环伏安法及其吸收光谱确定了CdSxSe1-x纳米晶的能级位置。最后以P3HT/CdSxSe1-x/TiO2复合薄膜材料为光活性层组装成固态纳米结构杂化太阳电池,研究了CdSxSe1-x壳层厚度对该电池光电转换性能的影响,结果表明转换效率最高可达到0.68%。     

Bi_4Ti_3O_(12)/TiO_2异质结的制备及其光催化性能

用静电纺丝和水热法制备了Bi4Ti3O12/TiO2异质结,用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对Bi4Ti3O12/TiO2异质结和TiO2纳米棒的形貌及晶体结构进行了表征和分析。其紫外可见漫反射光谱(UV-vis DRS)表明,相比于纯TiO2纳米棒,Bi4Ti3O12/TiO2异质结的吸收带边有明显的红移,禁带宽度也有减小,说明Bi4Ti3O12/TiO2异质结的形成有利于提高样品对可见光的吸收。从光致发光图谱(PL)可见,Bi4Ti3O12/TiO2异质结在440 nm的发射峰强度明显减弱,说明Bi4Ti3O12/TiO2之间的异质结结构有效抑制了光生电子和空穴的复合。对甲基橙的紫外光催化降解结果表明,这种异质结在紫外光辐射下表现出更高的光催化活性,随着异质结浓度的增加其光催化性能明显提高。     

金红石TiO_2纳米棒阵列的生长机理及在染料敏化太阳电池中的应用

用水热法制备了金红石TiO2纳米棒阵列光阳极,并对样品进行XRD、SEM和HRTEM表征分析。文中研究了不同水热条件对金红石TiO2纳米棒阵列的生长形貌影响,详细探讨了其水热生长机理。结果表明:金红石纳米棒的直径和长度随着水热体系能量增加而增加;添加剂对金红石纳米棒的水热生长影响较大;在金红石TiO2纳米棒阵列光阳极水热生长过程中,会同导电玻璃衬底之间形成致密层,该致密层对DSSCs的光电转换性能影响较严重。将制备的金红石TiO2纳米棒阵列光阳极应用于DSSCs中,在AM 1.5 100 mW/cm2(air-mass 1.5,AM 1.5意为光线通过大气的实际距离为大气垂直厚度的1.5倍)标准条件下,测得1.81%的光电转换效率。     

CuO/TiO_2异质多孔纳米结构的制备及其光催化性能

以Cu(OH)_2纳米棒阵列为前驱体,钛酸四丁酯为钛源,采用外向包覆合成法,利用Cu(OH)_2自身热分解产生的微量水分子与负载在其表面的钛酸四丁酯缓慢反应,制备了CuO/TiO_2异质多孔纳米结构,并研究了产物对罗丹明B(RhB)的光催化降解性能。结果表明,得到的产物薄膜为直径2~4μm的微孔组成的多孔纳米结构,微孔的孔壁由直径500nm左右的纳米棒组装而成。产物CuO/TiO_2异质多孔纳米结构比纯TiO_2纳米结构对RhB有更好的光催化降解性能,这主要是由两方面的原因引起的:一方面,CuO/TiO_2异质多孔纳米结构具有更好的吸附性能和更大的比表面积;另一方面,产物CuO/TiO_2为异质复合纳米结构,异质结的存在能有效地降低光生电子空穴对的复合,从而提高产物的光催化降解效果。     

氧化锌纳米棒形貌对ZnO/Cu2O异质结太阳能电池光伏性能的影响

采用电化学沉积法制备了ZnO纳米棒,首先讨论了电化学沉积参数对氧化锌(ZnO)纳米棒形貌的影响,并对不同长度ZnO纳米棒的光吸收和反射等性质进行了研究.实验发现沉积时间是影响纳米棒长度、直径的重要因素,ZnO纳米棒的微观形貌对其光学性质有重要影响.然后以氧化锌纳米棒为n型材料,以氧化亚铜为p型材料,通过电化学沉积法构筑了ZnO/Cu2O异质结太阳能电池,并测试了其光伏性能,研究表明增长纳米棒阵列的长度使得开路电压、短路电流密度及光电转换效率等性能得到提升.最后,综合分析了氧化锌纳米棒形貌与所组装电池的性能之间的关系,发现调控氧化锌纳米棒的形貌是提高ZnO/Cu2O异质结太阳能电池光伏性能的有效途径.     

CuMnO2/TiO2复合光催化剂增效催化降解亚甲基蓝

首次利用旋涂法将CuMnO_2纳米晶负载于TiO_2纳米棒阵列薄膜上,制备出光催化性能增强的CuMnO_2/TiO_2复合光催化剂,并考察了样品对亚甲基蓝(MB)的光催化降解性能。研究结果表明,CuMnO_2纳米晶和TiO_2纳米棒之间形成p-n异质结结构,能够有效促进电子和空穴的分离,使得CuMnO_2/TiO_2复合光催化剂具有更高的光催化性能。采用浓度为0.25 g/L的CuMnO_2悬浮液制得的CuMnO_2/TiO_2复合材料的光催化降解效率最高,其光催化效率和表观速率分别为88%和0.298 6 h~(-1),较纯TiO_2提高约26%和80%。     

TiO2/SrTiO3光子晶体薄膜的制备及光电催化性能

以单分散聚苯乙烯(PS)微球在FTO导电玻璃表面自组装形成的蛋白石(Opal)结构为模板,使用溶胶-凝胶法进行TiO2前驱体的填充,退火后制备出反蛋白石结构的TiO2光子晶体薄膜。进一步通过水热反应将部分TiO2反应生成SrTiO3从而形成TiO2/SrTiO3异质结。通过多种手段技术表征了所制备材料和结构的晶型,形貌及其光电化学性能。研究结果表明,SrTiO3的负载量和晶粒大小可以通过水热反应时间调控。在经过0.5h的水热反应后,SrTiO3的负载量为9.6%,TiO2/SrTiO3薄膜保持了原有的光子晶体结构,且光电流增大了82%。TiO2/SrTiO3异质结构的形成能有效地促进光生载流子的分离,提高光电催化性能。     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.