PH-dependent electron transfer from re-bipyridyl complexes to metal oxide nanocr

2019-10-06 02:27:39

pH edge ET dependent Prime

责任者: She, Chunxing;Anderson, Neil A.;Guo, Jianchang;Liu, Fang;Goh, Wan-Hee;Chen, Dai-Tao;Mohler, Debra L.;Tian, Zhong-Qun;Hupp, Joseph T.;Lian, Tianquan 单位: Department of Chemistry, Northwestern University, Evanston, IL 60208, United States 来源出处: Journal of Physical Chemistry B,2005,109(41):19345-19355 摘要: Photoinduced interfacial electron transfer (ET) from molecular adsorbates to semiconductor nanoparticles has been a subject of intense recent interest. Unlike intramolecular ET, the existence of a quasicontinuum of electronic states in the solid leads to a dependence of ET rate on the density of accepting states in the semiconductor, which varies with the position of the adsorbate excited-state oxidation potential relative to the conduction band edge. For metal oxide semiconductors, their conduction band edge position varies with the pH of the solution, leading to pH-dependent interfacial ET rates in these materials. In this work we examine this dependence in Re(LP)(CO) 3Cl (or ReC1P) [LP = 2,2 prime -bipyridine-4,4 prime -bis- CH2PO(OH)2] and Re-(LA)(CO)3Cl (or ReC1A) [LA = 2,2 prime -bipyridine-4,4 prime -bis-CH2COOH] sensitized TiO2 and ReC1P sensitized SnO2 nanocrystalline thin films using femtosecond transient IR spectroscopy. ET rates are measured as a function of pH by monitoring the CO stretching modes of the adsorbates and mid-IR absorption of the injected electrons. The injection rate to TiO 2 was found to decrease by 1000-fold from pH 0-9, while it reduced by only a factor of a few to SnO2 over a similar pH range. Comparison with the theoretical predictions based on Marcus theory of nonadiabatic interfacial ET suggests that the observed pH-dependent ET rate can be qualitatively accounted for by considering the change of density of electron-accepting states caused by the pH-dependent conduction band edge position. © 2005 American Chemical Society. 关键词: Nanostructured materials;Thin films;Complexation;Electron transitions;pH effects;Adsorbents;MOS devices;Electron transfer (ET);Conduction bands;Band edge;Electronic states