Confinement of europium (Eu3+) ions in silica (SiO2) nanospheres yields efficient red-emitting nanophosphors when excited via charge transfer states (as) absorption in UV (393 nm) radiation. This is explained on the basis of modulation of f-f transition due to quantum confinement of rare-earth ion in a nanosize host. It is also evidenced that the short range crystallanity and confinement effects provided by the nanospheres increases the Eu3+ emission intensity by almost ten times at the expense of CTS. Coating of organically modified SiO2 nanospheres resulted in low refractive index layers that are highly useful as cover glazing for solar collectors. (C) 2010 Elsevier B.V. All rights reserved.