Silica-coated titania nanoparticles are important in sunscreens, UV filters and optical nanocomposites. The surface characteristics (extent of coverage, texture and thickness) of in situ SiO₂-coated, mostly rutiletitania nanoparticles made in one step by flame spray pyrolysis (FSP) were compared to FSP-made mixed (co-oxidized) SiO₂/TiO₂ ones by transmission electron microscopy (TEM), Raman, FT-IR spectroscopy, electrophoretic mobility and isopropanol chemisorption followed by mass spectroscopy. Increasing the silica content shifted the isoelectric point (IEP) toward that of pure silica for externally mixed SiO₂ and TiO₂, co-oxidized SiO₂/TiO₂ and low SiO₂ content (<10 wt%) silica-coated TiO₂nanoparticles. At higher SiO₂ contents, SiO₂-coated titania exhibited negative ζ potentials at all pH values (and thus no IEP) indicating hermetic or complete coverage of the TiO₂ surface by SiO₂ as was confirmed by isopropanol chemisorption. Co-oxidized particles containing segregated TiO₂ and SiO₂ domains exhibited Si–O–Ti and Si–O–Si bonds of higher IR intensity than hermetically-coated TiO₂. The latter exhibited a peak at 1225 cm⁻¹ attributed to Si–O–Si asymmetric vibrations in contrast to the former.