We present a comparative density functional tight binding study of an organic molecule attachment to TiO
2 via a carboxylic group, with the example of acetic acid. For the first time, binding to low-energy surfaces of crystalline anatase (101), rutile (110) and (B)-TiO
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We present a comparative density functional tight binding study of an organic molecule attachment to TiO
2 via a carboxylic group, with the example of acetic acid. For the first time, binding to low-energy surfaces of crystalline anatase (101), rutile (110) and (B)-TiO
2 (001), as well as to the surface of amorphous (
a-) TiO
2 is compared with the same computational setup. On all surfaces, bidentate configurations are identified as providing the strongest adsorption energy,
Eads = −1.93, −2.49 and −1.09 eV for anatase, rutile and (B)-TiO
2, respectively. For monodentate configurations, the strongest
Eads = −1.06, −1.11 and −0.86 eV for anatase, rutile and (B)-TiO
2, respectively. Multiple monodentate and bidentate configurations are identified on
a-TiO
2 with a distribution of adsorption energies and with the lowest energy configuration having stronger bonding than that of the crystalline counterparts, with
Eads up to −4.92 eV for bidentate and −1.83 eV for monodentate adsorption. Amorphous TiO
2 can therefore be used to achieve strong anchoring of organic molecules, such as dyes, that bind via a -COOH group. While the presence of the surface leads to a contraction of the band gap
vs. the bulk, molecular adsorption caused no appreciable effect on the band structure around the gap in any of the systems.
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