The Institute of Chemistry and Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
Small. 2015 Jan 27;11(4):462-71. doi: 10.1002/smll.201402262. Epub 2014 Sep 10.
Hybrid semiconductor-metal nanoparticles are interesting materials for use as photocatalysts due to their tunable properties and chemical processibility. Their function in the evolution of hydrogen in photocatalytic water splitting is the subject of intense current investigation. Here, the effects of the surface coatings on the photocatalytic function are studied, with Au-tipped CdS nanorods as a model hybrid nanoparticle system. Kinetic measurements of the hydrogen evolution rate following photocatalytic water reduction are performed on similar nanoparticles but with different surface coatings, including various types of thiolated alkyl ligands and different polymer coatings. The apparent hydrogen evolution quantum yields are found to strongly depend on the surface coating. The lowest yields are observed for thiolated alkyl ligands. Intermediate values are obtained with L-glutathione and poly(styrene-co-maleic anhydride) polymer coatings. The highest efficiency is obtained for polyethylenimine (PEI) polymer coating. These pronounced differences in the photocatalytic efficiencies are correlated with ultrafast transient absorption spectroscopy measurements, which show a faster bleach recovery for the PEI-coated hybrid nanoparticles, consistent with faster and more efficient charge separation. These differences are primarily attributed to the effects of surface passivation by the different coatings affecting the surface trapping of charge carriers that compete with effective charge separation required for the photocatalysis. Further support of this assignment is provided from steady-state emission and time-resolved spectral measurements, performed on related strongly fluorescing CdSe/CdS nanorods. The control and understanding of the effect of the surface coating of the hybrid nanosystems on the photocatalytic processes is of importance for the potential application of hybrid nanoparticles as photocatalysts.
杂化半导体-金属纳米粒子由于其可调的性质和化学可加工性，是作为光催化剂的有趣材料。它们在光催化水分解中氢的演化中的作用是当前研究的热点。在这里，研究了表面涂层对光催化功能的影响，以 Au 封端的 CdS 纳米棒作为模型杂化纳米粒子系统。在具有不同表面涂层的类似纳米粒子上进行了光催化水还原后氢析出率的动力学测量，包括各种类型的巯基烷基配体和不同的聚合物涂层。发现表观氢析出量子产率强烈依赖于表面涂层。巯基烷基配体的产率最低。L-谷胱甘肽和聚（苯乙烯-co-马来酸酐）聚合物涂层的产率中等。使用聚乙烯亚胺（PEI）聚合物涂层的产率最高。这些在光催化效率上的明显差异与超快瞬态吸收光谱测量相关联，该测量表明 PEI 涂层的杂化纳米粒子的漂白恢复更快，与更快速和更有效的电荷分离一致。这些差异主要归因于不同涂层的表面钝化效应对表面载流子的捕获的影响，这与光催化所需的有效电荷分离竞争。相关强荧光 CdSe/CdS 纳米棒的稳态发射和时间分辨光谱测量进一步支持了这一分配。控制和理解杂化纳米系统表面涂层对光催化过程的影响对于作为光催化剂的杂化纳米粒子的潜在应用具有重要意义。
