The preparation of wavelength-specific Bragg mirrors was realized by an effective and reproducible spin-coating approach using colloidal suspensions of functionalized mesoporous silica nanoparticles and titania sols. Due to the small particle size and the resulting low surface roughness, the formation of multilayers was possible without transmitting defects on the surface with every following coating step. The Bragg reflectors show sensitivity toward specific relative pressures of organic vapors such as toluene, giving rise to optically encoded adsorption properties as a function of solvent pressure and, thus, to optical adsorption isotherms.