Titanium dioxide nanoparticles modified by salicylic acid and arginine: Structure, surface properties and photocatalytic decomposition of p-nitrophenol

In this study, titanium dioxide (TiO ₂ ) nanoparticles were surface-modified with salicylic acid (SA) and arginine (Arg) using an environmentally friendly and convenient method, and the bonding structure, surface properties and degradation efficiency of p-nitrophenol (PNP) were investigated. X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), water contact angle (WCA) measurements, ζ-potentiometric analysis, UV/visible diffuse reflectance spectroscopy (UV-vis DRS), and thermogravimetric analysis (TGA) were performed to evaluate the modification effect. The degradation rates were determined by high-performance liquid chromatography (HPLC). The results show that bidentate or bridging bonds are most likely formed between SA/Arg and TiO ₂ surface. Surface modification with SA, Arg, or both can improve the lipophilic properties and decrease the zeta potential, and also result in a red shift of the absorption wavelength. TiO ₂ nanoparticles modified by Arg or both SA and Arg show a large specific surface area and pore volume. Further, degradation experiments under visible light show that Arg modification is most efficient. This simple and versatile synthetic method to produce TiO ₂ nanoparticles surface-modified with various organic capping agents can be used for novel multifunctional photocatalysts as required for various applications in energy saving and environmental protection.