Solvatochromism of a D205 indoline dye at the interface of a small TiO₂-anatase nanoparticle in acetonitrile: a combined molecular dynamics simulation and DFT calculation study

ABSTRACT

A combined molecular dynamics (MD) simulation and density functional theory (DFT) calculations were used to investigate the effect of the acetonitrile (ACN) solution on the absorption and the charge transfer in a D205 indoline dye at the interface of a TiO₂ nanoparticle. DFT calculations were carried out to estimate the equilibrium geometry of a small Ti₃₀O₆₂H₄-anatase nanoparticle and to derive interaction parameters for bidentate binding of a D205 dye to TiO₂. A series of the D205 dye configurations anchored to Ti₃₀O₆₂H₄ were generated from the MD simulations and used as input for the time-dependent DFT (TD-DFT) calculations. We found that the immersion of the D205-Ti₃₀O₆₂H₄ composite system into the polar ACN environment results in conformational changes of the dye moiety, which are accompanied by the solvatochromic redshift of its long-wavelength absorption band up to 1900 cm^-1. Our results show that the HOMO and LUMO energy level alignment of the dye and the nanoparticle suggests a favourable driving force for charge transfer from the dye to TiO₂. The MD/TD-DFT-estimated solvatochromic shift for the D205 dye at the TiO₂/ACN interface is in good agreement with the experiment, showing that such computational approach enables reliable predictions of optical properties of other dye-TiO₂ composites in solution.

KEYWORDS:

• TiO₂
• anatase
• D205 dye
• solvatochromic shift
• MD simulation

Acknowledgment

A.K. and O.N.K acknowledge Grant № 0119U002532 of the Ministry of Education and Science of Ukraine. This work was performed using computational facility ‘Dell PowerEdge 740 with Graphic Accelerator Modules NVIDIA Tesla V100 16GB GPU’ of the Center of Collective Use of Scientific Equipment ‘Laboratory of Micro- and Nanosystems, Advanced Materials and Technologies’ of V. N. Karazin Kharkiv National University and the Ministry of Education and Science of Ukraine. A.I. and F-A.M. acknowledge the Agence Nationale de la Recherche (ANR-19-CE05-0009-01 ‘Ultrafast Photoinduced Processes of Organic Dyes in Ionic Liquid/Molecular Solvent Mixtures Designed for Dye Solar Cells’) for financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Agence Nationale de la Recherche [Grant number ANR-19-CE05-0009-01] and the Ministry of Education and Science of Ukraine [Grant number 0119U002532].