Surface interactions between Y 2O 3 nanocrystals and organic molecules—an experimental and quantum-chemical study

Abstract

The surface interactions between Y 2O 3 nanocrystals and the organic molecules formic acid, diethylene glycol (DEG), and tetramethoxy silane (TMOS), have been studied experimentally and by quantum chemical calculations with the intent to elucidate the chemisorption characteristics such as adsorbate vibrational spectra and adsorption structures. Nanocrystal synthesis was performed by a colloidal method based on polyols and by a rapid combustion method. The products were experimentally characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). In the quantum chemical calculations, the B3LYP hybrid density functional ab initio method was used to study the chemisorption of formic acid, DEG and TMOS at the surface of Y 12O 18 clusters. From a comparison of calculated and experimental vibrational spectra, the binding mode for formic acid on Y 2O 3 was inferred to be of bridge or bidentate type. The XPS and FT-IR experiments showed that DEG is chemisorbed on the particle surface. The experimental IR spectra of DEG chemisorbed on Y 2O 3 were consistent with an adsorption mode where the hydroxyl groups are deprotonated according to the quantum-chemical computations. The adsorption energy is of the order of 370 kJ mol −1 for formic acid, 550 kJ mol −1 for DEG, and 60 kJ mol −1 for TMOS, according to the quantum chemical calculations.