FTIR SPECTROSCOPIC INVESTIGATION OF CO-PRECIPITATED ZNO–TIO₂ NANOCOMPOSITES: VIBRATIONAL FEATURES, METAL–OXYGEN BONDING, AND INTERPRETIVE LIMITATIONS

Abstract

Zinc oxide (ZnO) and titanium dioxide (TiO₂) are common inorganic UV-filter ingredients, and composites holding both oxides have been investigated for their potential optical and surface properties. A co-precipitated ZnO–TiO₂ sample S1 is prepared using 6.813 g ZnCl₂, 1.000 g pre-formed TiO₂ and 8.000 g of NaOH and its Fourier-transform infrared (FTIR) transmittance spectrum is examined. The sample was dried but was not calcined. The spectra were taken between 4000 and 650 cm -1.  No well-resolved sample-related absorption bands were observed above approximately 1000 cm⁻¹. Features near 3900–3500 cm⁻¹ and 1750–1400 cm⁻¹, and also one near 2360 cm⁻¹, were interpreted as being due to water-vapour and CO₂ in the atmosphere. Transmittance values were significantly reduced < ~1000 cm-1 with a low limit of detection of ~50% at the lowest transmittance measured. This is in line with the high absorption values obtained in the metal–oxygen related vibration, and the absorption minimum was not resolved, nor were the contribution of the metal–O and the oxygen–H vibrations resolved individually. The contriutions of hydroxyl, adsorbed-water, and carbonate species were neither confirmed nor ruled out. The absorption at low wavenumbers is then tentatively interpreted in the available spectrum, with the need for further measurements to determine the phase composition and surface chemistry of the material.