Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, California 95064, USA.
ACS Appl Mater Interfaces. 2009 Sep;1(9):2060-5. doi: 10.1021/am900425v.
Au-TiO2 snowman-like heterodimer nanoparticles were prepared by a surface sol-gel process based on gold Janus nanoparticles whose surface-protecting monolayers consisted of a hemisphere of hydrophobic 1-hexanethiolates and the other of hydrophilic 2-(2-mercaptoethoxy)ethanol. Transmission electron microscopic measurements showed that the resulting TiO2 nanoparticles (diameter 6 nm) exhibited well-defined lattice fringes that were consistent with the (101) diffraction planes of anatase TiO2. The heterodimer nanoparticles displayed apparent photoluminescence that was ascribed to electronic transitions involving trap states of TiO2 particles, and the photocatalytic activity was manifested by the oxidative conversion of methanol into formaldehyde, which was detected quantitatively by the Nash method. The enhanced photocatalytic performance, as compared to that of the TiO2 nanoparticles alone, was ascribed to the charge separation of photogenerated electrons and holes at the Au-TiO2 interface that was facilitated by the close proximity of the gold nanoparticles. These results suggested that (i) there were at least two possible pathways for photogenerated electrons at the TiO2 conduction band, decay to the trap states and transfer to the gold nanoparticles, and (ii) energy/electron transfer from the trap states to gold nanoparticles was less efficient. In essence, this study showed that the snowman-like heterodimers might be exploited as a homogeneous photocatalytic system for the preparation of functional molecules and materials.
Au-TiO2 雪人状杂化二聚体纳米粒子是通过基于金 Janus 纳米粒子的表面溶胶-凝胶过程制备的，其表面保护单层由疏水性 1-己硫醇的半球和亲水性 2-(2-巯基乙氧基)乙醇的半球组成。透射电子显微镜测量表明，所得 TiO2 纳米粒子（直径 6nm）表现出明确的晶格条纹，与锐钛矿 TiO2 的（101）衍射平面一致。杂化二聚体纳米粒子显示出明显的光致发光，归因于涉及 TiO2 颗粒陷阱态的电子跃迁，光催化活性表现为甲醇氧化转化为甲醛，通过 Nash 法定量检测到。与单独的 TiO2 纳米粒子相比，增强的光催化性能归因于 Au-TiO2 界面处光生电子和空穴的电荷分离，这是由金纳米粒子的近距离促进的。这些结果表明：（i）在 TiO2 导带中，光生电子至少有两种可能的途径，衰减到陷阱态并转移到金纳米粒子，（ii）从陷阱态到金纳米粒子的能量/电子转移效率较低。本质上，这项研究表明，雪人状杂化二聚体可用作制备功能分子和材料的均相光催化体系。
