The surface composition and dispersion of Ti species were further determined by XPS. Two fractions of Ti species detected at the surface can be distinguished from Ti 2p3/2 peak deconvolution (Fig. ). Considering that the binding energy (BE) values of ca. 460.0 eV and 458.5 eV are assigned to the fractions of Ti incorporated in the SiO2 matrix (Ti-O-Si) and Ti present as the nanodomains (Ti-O-Ti), respectively , the percentages of total Ti and silica-incorporated Ti species at the surface can be quantified (Table ). Notably, the measured surface Ti % and Ti-O-Si % contents (XPS) vs. the nominal Ti loadings show a linear relationship up to 16% Ti loading (Fig. ). Similarly, a linear relationship with a slope of 1 can be found between the bulk Ti% measured from ICP-AES and the nominal Ti%, demonstrating an excellent quantitative control of the bulk composition in Ti-SiO2 materials prepared by aerosol method. Besides, the surface Ti concentration is close to the bulk content,