Observation of pH-dependent back-electron-transfer dynamics in alizarin/TiO2 adsorbates: importance of trap states

The Journal of Physical Chemistry. B
Victor V MatylitskyJosef Wachtveitl

Abstract

The dependence of the interfacial electron transfer in alizarin-sensitized TiO2 nanoparticles on the sample pH has been examined via transient absorbance spectroscopy in the visible spectral region (443-763 nm). Excitation of the alizarin/TiO2 system with visible pump pulses (lambdaexc = 500 nm) leads to a very fast electron injection (tauinj < 100 fs) over a wide pH range. Back electron transfer shows complicated multiphasic kinetics and strongly depends on the acidity of the solution. The strong dependence of back-electron-transfer dynamics on the ambient pH value is explained by a Nernstian-type change in the semiconductor band energy. Indeed, a variation of pH values over 7 units leads to a approximately 0.42 eV change of the conduction band edge position (i.e., the nominal free energy of the electron in the electrode). Assuming a pH-independent redox potential of the dye, this change was sufficient to push the system to a condition where direct photoinitiated electron injection to intraband gap surface states could be investigated. The existence of an electron-transfer pathway via surface trap states is supported by the similarity of the observed back-electron-transfer kinetics of alizarin/TiO2 at pH 9 and alizarin/ZrO2 re...Continue Reading

References

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Citations

Jan 14, 2009·Journal of the American Chemical Society·Yuanmin WangH Peter Lu
Jun 6, 2009·Journal of the American Chemical Society·Yuanmin WangH Peter Lu
Dec 20, 2012·The Journal of Chemical Physics·Jingrui LiMichael Thoss
Jan 13, 2009·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Lars DworakJosef Wachtveitl
May 21, 2010·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Victor V MatylitskyJosef Wachtveitl
Aug 19, 2015·The Journal of Physical Chemistry Letters·Run LongOleg V Prezhdo
Apr 5, 2017·The Journal of Physical Chemistry. B·Myungsam JenYoonsoo Pang
Mar 15, 2015·Journal of Physics. Condensed Matter : an Institute of Physics Journal·Jingrui LiMichael Thoss
Jan 14, 2011·Physical Chemistry Chemical Physics : PCCP·Marcin ZiółekAbderrazzak Douhal
Aug 7, 2014·Dalton Transactions : an International Journal of Inorganic Chemistry·Tanmay BanerjeeHirendra Nath Ghosh
Jan 21, 2021·Langmuir : the ACS Journal of Surfaces and Colloids·Michel P de HaanHan Zuilhof
Feb 20, 2008·Accounts of Chemical Research·Oleg V PrezhdoVictor V Prezhdo
Dec 8, 2010·The Journal of Physical Chemistry. B·Zi LiGang Lu
Jun 29, 2021·The Journal of Physical Chemistry. C, Nanomaterials and Interfaces·Jennifer L PeperJames M Mayer
Jun 21, 2007·Journal of the American Chemical Society·Walter R DuncanOleg V Prezhdo

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