A method of making a coated article is described comprising providing an inorganic substrate and coating the substrate with a coating composition. The coating composition comprises a plurality of siloxane nanoparticles dispersed in an organic solvent. A portion of the nanoparticles comprise the reaction product of a first alkoxy silane compound having a first organofunctional group and a second organofunctional group of a second compound and the reaction between the first and second organofunctional groups form an organic linking group. The method further comprises drying the coating composition and heating the coated substrate to volatilize the organic linking groups thereby forming a porous surface layer on the inorganic substrate. In another embodiment an article is described comprising an inorganic substrate, such as glass, and a porous inorganic (e.g. silica) surface layer having an average pore size of less than 30 nm. Also described are coating compositions and methods of making a nanoparticle coating compositions.