Smooth and nonswelling spherical silica particles with a diameter of 100 nm and an aminopropyl coating are soluble in water at pH 11, coagulate quickly at pH 3, and redissolve at pH 9. Electron microscopy as well as visible spectra of covalently attached porphyrins indicate the aggregation state of the particles. Long-chain α, ω-dicarboxylic acids with a terminal oligoethyleneglycol (OEG)-amide group were attached in a second self-assembly ...
