Visible light absorption of TiO2 nanoparticles surface-modified with vitamin B6: A comparative experimental and DFT study

Abstract

Surface modification of titanium dioxide nanoparticles (TiO 2 NPs) with the biologically active molecule pyridoxine hydrochloride (vitamin B 6) was found to alter the optical properties. Microstructural characterization involving transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis revealed that the anatase TiO 2 NPs had a narrow size distribution with an average diameter of 45 Å. The absorption onset of the surface-modified TiO 2 samples was red-shifted by about 0.4 eV compared to the unmodified particles. The mode of binding between vitamin B 6 and the surface Ti atoms was investigated by Fourier transform infrared spectroscopy (FTIR). From the Benesi-Hildebrand plot, the stability constant of the surface complex was found to be of the order 10 2 M-1. The experimental findings were supported by detailed quantum chemical calculations based on the density functional theory (DFT). Agreement was found between the experimentally measured absorption spectra of the TiO 2 NPs surface-modified with vitamin B 6 and the theoretically calculated electronic excitation spectra of the corresponding model system.

Interfacial Charge Transfer Transitions in Colloidal TiO2 Nanoparticles Functionalized with Salicylic acid and 5-Aminosalicylic acid: A Comparative Photoelectron Spectroscopy and DFT Study

“…For example, the most studied photocatalyst TiO 2 has a band gap of 3.2 eV and, therefore, absorbs less than 5% of the available solar light, allowing only UV photons to produce electron–hole pairs and stimulate redox processes on the catalyst surface. During the last decade, extensive research has shown that interfacial charge transfer (ICT) complex formation between inorganic semiconductors, anatase TiO 2 , in particular, and small colorless aromatic compounds leads to the appearance of the absorption in the more practical, visible or near-infrared spectral range. − Direct electron transfer across the organic–inorganic interfaces has new potential applications in different areas such as photocatalysis, ,, photovoltaics, ,− ,− , and sensing of small colorless biomolecules including drugs. ,, Moreover, proper functionalization can increase the sorption capacity and selectivity of sorbents toward heavy metal ions, while the presence of bioactive molecules on the particles’ surfaces decreases their toxicity. , …”