In-Situ Growth and Oxidation of Cu Nanoparticles on Rutile TiO 2 (110)

Copper (oxide) nanoparticles on TiO2 substrates are of interest for various applications, ranging from waste cleaning to photocatalytic virus inactivation. We studied the growth and oxidation of Cu nanoparticles (NPs) on single crystalline rutile TiO2(110) using X-ray grazing incidence diffraction and small angle scattering (GIXRD, GISAXS) and X-ray photoelectron spectroscopy (XPS) methods, complemented by scanning Auger electron microscopy (SAM) and scanning electron microscopy (SEM). Cu NPs were grown via physical vapor deposition under ultrahigh vacuum (UHV) conditions at different temperatures. We found that higher growth temperatures result in not only larger NPs but also different NP epitaxy. The particle’s shape and size were studied with SAM, SEM, GIXRD, and GISAXS, revealing homogeneous size distributions and oxidation states across the whole surface. It was found that the particles either fully oxidize to a mixture of CuO and Cu2O or form core–shell particles with a metallic Cu core and an oxide shell after oxidation at 1 bar O2 and exposure to ambient (atmospheric) conditions. With the exception of minor amounts of Cu2O(111), all of the other oxides are amorphous. Testing the long-term stability of the NPs revealed that their oxidation state at different oxidation times (beyond the initial oxidation) did not change, confirming the stability of the NPs under ambient conditions.