A novel surface modification scheme for ITO nanocrystals by acetylene: a combined experimental and DFT study

Many applications of Sn-doped indium oxide (ITO) films in organic electronics require appropriate surface modifications of ITO nanocrystals with small organic molecules, such as silanes, phosophonic acids and carboxylic acids, to improve interfacial contacts and charge transfer. Here, we propose a new surface modification strategy via adsorption of acetylene molecules on an oxygen-terminated ITO(100) surface using a slab crystalline model to represent the nanocrystal surface. The adsorption was first studied using density functional theory. It was found that the chemisorption of C2H2 on two types of surface oxygen dimers is highly exothermic with the calculated adsorption energies of 3.80 eV and 5.19 eV, respectively. Electron population analysis reveals the origin of the strong interaction between the adsorbate and the ITO(100) surface. Experimental studies on the synthesized ITO nanocrystals using X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy confirm the predicted strong adsorption of C2H2 on ITO surfaces.