Benzimidazole derivative vs. different phases of TiO2-physico-chemical approach

• TiO2 (R) enhances the fluorescence.
• TiO2 (A), TiO2 (H), TiO2 (P25) phases quenches the fluorescence.
• BPBI is adsorbed on surface of the nanoparticle.

1-Benzyl-2-phenyl-1H-benzo[d]imidazole (BPBI) has been synthesized by simple steps and characterized by spectral studies. Absorption and fluorescence spectral studies have been employed to investigate the interaction of BPBI with the anatase, hombikat, P25 and rutile phases of TiO2. The emission of the BPBI is efficiently quenched by anatase, hombikat and P25 TiO2 nanoparticles owing to charge injection from the excited singlet state of BPBI to the conduction band of the TiO2 nanoparticles. Surprisingly, rutile phase enhances the fluorescence which is likely due to lowering of LUMO and HOMO levels of the ligand on ducking of the benzimidazole moiety of the BPBI molecule into the void space of rutile TiO2. Electron injection from photoexcited BPBI to the TiO2 conduction band (S∗ → S+ + e−CB) is likely to enhance the fluorescence.

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