Abstract

The present research focuses on the comparative investigation ofthe acid base surfaceproperties (the isoelectric point, pH(iep) and point of zero charge, pH(pzc)) ofone-dimensionalTiO2nanomaterials. Different one-dimensional TiO2 nanomaterials, nanotubes (NTs) and nanowires (NWs) were prepared by an alkaline hydrothermal synthesis procedure. The structural propertiesofthe synthesized TiO2nanomaterials were investigated with high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The NWs and NTs were characterized using Raman and Fourier transform infrared (FT-IR) spectroscopy as well as Brunauer Emmett Teller (BET) measurements. Surfaceproperties, i.e. pH(iep) and pH(pzc) of NWs and NTs were determined from electrokinetic measurements, potentiometric mass and electrolyte titrations. The relative acidity for the NWs is found to be in the interval 3 < pH(iep) < 4 in comparison with the NTs, with 4 < pH(iep) < 6. The observed differences in the relative acidity are correlated with differences in crystal structure ofthe studied nanomaterials and their resulting morphology. In addition, our results reveal a strong electrolyte effect on the characteristic points, pH(iep) and pH(pzc), especially the higher cation affinity for both TiO2nanomaterials surfaces that has a significant effect on the pH ofthe system. Application ofthe multisite complexation (MUSIC) model yields a satisfactory description ofthe electrokinetic data and can explain observed salt effect.