Journal article

Monitoring N719 Dye Configurations on (1 × n)-Reconstructed Anatase (100) by Means of STM: Reversible Configurational Changes upon Illumination

We report exptl. results concerning the STM imaging of cis-bis (isothiocyanate)-bis-(2,2'-bipyridyl-4,4'dicarboxylate)ruthenium(II)bis(tetrabutylammonium) dye (known as N719) adsorbed on a single crystal of anatase TiO2(100). The cleaning pretreatment, by sputtering and annealing, of TiO2(100) yields a reproducible (1 × n) surface reconstruction. Previous to dye deposition, TiO2 was covered with one monolayer of 4-tert-butylpyridine (4-TBP) in ultrahigh vacuum (UHV) in order to protect the surface against air contamination. N719 was subsequently deposited by dipping the crystal into the dye soln. 4-TBP was removed partially in the soln. and totally by heating the sample to around 285-300 °C in UHV. The images of the deposited 4-TBP on TiO2(100) revealed a complete surface coverage showing three modes of adsorption on TiO2. The relatively uncomplicated desorption of 4-TBP enables the accommodation and chemisorption of most N719 mols. directly onto the TiO2 surface. The STM imaging of N719 was affected, in a reversible way, by illumination, because the quality of the image changed after a few hours in the dark or under illumination conditions. The results presented herein are discussed in terms of changes in mol. configurations and in open circuit potentials.


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