硫和银共掺杂介孔TiO2的制备、表征及其对染料的光催化降解活性

以P123为模板,以钛酸四正丁酯、硝酸银和硫脲为原料采用模板法制备了一系列硫和银共掺杂介孔TiO₂光催化材料．利用SEM、XRD、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征．以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能．结果表明,用模板法制备的共掺杂介孔TiO₂光催化材料在紫外和可见光条件下较纯介孔TiO₂和单掺杂介孔TiO₂对甲基橙溶液具有更好的光催化降解效果, 且硫和银的掺杂量及样品焙烧温度显著影响该材料的催化性能．当硫掺杂量为2mol%和银掺杂量为1mol%,在500 oC 焙烧2 h所得光催化材料的催化性能最佳,4 h即可使甲基橙的降解率达98.8%,重复使用4次仍可使甲基橙的降解率保持在87.5%以上     

Ce掺杂CrSi2电子结构和光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法,对未掺杂及Ce掺杂CrSi2的电子结构和光学性质进行理论计算。计算结果表明,未掺杂CrSi2是间接带隙半导体,其禁带宽度为0.392 eV,掺杂Ce元素,仍然是间接半导体,带隙宽度下降为0.031eV。未掺杂CrSi2在费米能级附近主要由Cr-5d、Si-3p态贡献。Ce掺杂后在费米能级附近主要由Cr-5d轨道,Ce-4f轨道,C-2p,Si-3p轨道贡献,掺杂后电导率提高。未掺杂CrSi2有两个介电峰,掺杂后,只有一个介电峰。未掺杂CrSi2,在能量为6.008处吸收系数达到最大值,掺杂后在能量为5.009eV处,吸收系数达到最大值。     

掺杂钨丝的再结晶组织特征

本工作利用透射电子显微镜研究了两种丝径不同的掺杂钨丝的再结晶组织特征,0.4mm的钨丝在2100℃退火状态下呈现不均匀再结晶,而1.25mm的钨丝却强烈地反映出钾泡阻碍晶界迁移和对位错的钉扎作用。作者指出:在研究0.4mm以下掺杂钨丝的再结晶行为时,钾泡的分布状态固然重要,但还应着重研究深度拉拔在纤维组织和织构方面对延缓再结晶过程的作用。对这个问题的深入研究,有利于寻求合理的工艺参数。     

Determination of doping effects on Si and GaAs bulk samples properties by photothermal investigations

The knowledge of doping effects on optical and thermal properties of semiconductors is crucial for the development of opto-electronic compounds. The purpose of this work is to investigate these effects by mirage effect technique and spectroscopic ellipsometry SE.

The near gap optical spectra are obtained from photothermal signal for differently doped Si and GaAs bulk samples. However, the above bandgap absorption is determined from SE. These spectra show that absorption in the near IR increases with dopant density and also the bandgap shifts toward low energies. This behavior is due to free carrier absorption which could be obtained by subtracting phonon-assisted absorption from the measured spectrum. This carrier absorption is related to the dopant density through a semi-empirical model.

We have also used the photothermal signal phase to measure the influence of doping on thermal diffusivity.     

非磁性/磁性掺杂剂对SnO2体系的性能调控

本文通过第一性原理计算在GGA + U 框架下系统地研究了非磁性掺杂剂(Li)和磁性掺杂剂(V)以及相应的点缺陷(VO/VSn)掺杂SnO2基稀磁半导体(DMS)的稳定性、电子结构、键合性质、磁性以及光学性质. 计算得到的形成能结果表明, V元素单掺杂体系比Li元素单掺杂体系更稳定. 其中, VO存在的掺杂体系稳定性更高, 而VSn对掺杂体系的稳定性不利. 磁性分析表明, Li掺杂体系的磁矩大于V掺杂体系的磁矩. 当有点缺陷存在时, VSn的加入显著提高了掺杂体系的磁性, 而VO对非磁性金属元素/磁性金属元素掺杂体系的磁性影响不同：当VO存在于Li掺杂体系时, Li原子周围的O原子自旋极化减少, 因此导致磁矩降低;当V掺杂体系中有VO存在, 磁性不仅来源于V原子的自旋极化, 同时来源于VO周围的O原子的自旋极化,因此磁矩增大. 结合电子结构分析可知, Li掺杂体系的磁性是由O-p和Li-p轨道之间的双交换作用产生的, V掺杂体系的磁性是由O-p和V-d轨道之间的双交换作用产生的. 键合分析发现VO的存在可以提高两种金属掺杂体系键(Li-O和V-O)的共价性. 在可见光区域内, Sn15LiO32和Sn15VO32具有较高的光学透明度. 以上这些结果为非磁性金属元素(Li)和磁性金属元素(V)及相应的点缺陷(VO/VSn)掺杂SnO2在自旋电子器件中的应用提供了新的思路.     

掺杂的有机薄膜电致发光

用DCM染料和香豆素染料掺杂,成功地实现了有机薄膜电致发光颜色的改变,得到了从蓝绿到红色的发光,同时提高了器件的发光亮度,用不同区域掺杂方法,分析讨论了电致发光的机理,探讨了激子的产生区域和复合区域。     

Synthesis of metal-doped tio2 nanotubes and their catalytic performance for low-temperature co oxidation

Summary Gold-, gold and copper-doped TiO₂ nanotubes (Au/TiO₂ NTs, Au-Cu/TiO₂ NTs) are prepared by impregnation-reduction method. The doped nanotubes are characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their catalytic performance for CO oxidation is also examined     

掺铁TiO2纳米微粒的制备及光催化活性

采用溶胶-凝胶法制备了不同掺铁量的TiO2光催化剂,运用TG-DTA,XRD,SEM,DRS和测定光电导等方法对催化剂进行了表征.以高压汞灯为光源,罗丹明B为目标降解物,对其光催化活性进行了研究.实验结果表明,掺铁的TiO2比纯TiO2具有更好的催化活性.其原因:掺杂的铁作为受主捕获电子,使TiO2的n型半导体降低了光电导,控制了空穴和电子复合;同时掺杂的Fe3 可能形成杂质能级,由于掺杂能级处于禁带之中,使较长波长的光子也能被吸收,从而扩展吸收光谱的范围,增强了对可见光的吸收.     

Studies on hydrothermal synthesis of photolumniscent rare earth (Eu3+ & Tb3+) doped NG@FeMoO4 for enhanced visible light photodegradation of methylene blue dye

FeMoO₄ nanorods and their rare earth (Eu³⁺ and Tb³⁺) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO₄ and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO₄ nanorods.     

Bridgman growth of Bi4Si3O12 scintillation crystals and doped effects on radiation resistance

Ce, Nd and Eu doped BSO crystals 20×20× 100mm³ in size have been gown by vertical Bridgman method, and the doped effects on radiation resistance of BSO have also been studied for the first time. Nd and Eu dopns were found to improve the radiation resistance of BSO. However, Cc and Nd dopings degrade the light output of BSO except that Eu doping has almost no effect on it. Therefore, Eu may be the most promising dopant candidate for improving the scintillation properties of BSO crystal.