Patent ID: 7060240

Claim:
Nanocomposite materials that are fully glassy, black in color, and photoluminescent in red visible light region and/or in infrared region at ambient temperature produced by a sol-gel process comprising: preparing an aqueous or hydroalcoholic mixture containing a silicon alkoxide, an additional component A, and an acidic catalyst, wherein the molar ratio between water molecules and silicon atoms is equal to or higher than 4; causing the mixture to gel thereby obtaining a wet gel; causing said wet gel to dry; and densifing the thus obtained dry gel by means of a thermal treatment having a maximum temperature from 1200° C. to 1400° C.; where the additional component A is a dialkyldialkoxysilane, R 2 —Si—(OR′) 2 , or an alkyltrialkoxysilane, R—Si—(OR′) 3 , wherein R and R′ radicals are not aromatic; and in the range from 300° C. to 800° C. the thermal treatment is carried out under an atmosphere made up of pure HCl or a mixture containing at least 5% by volume of HCl in an inert gas, said atmosphere being anhydrous and not containing oxygen.