without an abrasive pad followed by washing the surface with water another example is based on using a 1 1 mixture of ethanol and acetone to remove organic impurities followed by washing the surface with water in some instances an additional optional step of chemically treating the surface with concentrated nitric acid sulfuric acid or piranha solution a 1 1 mixture of 96 sulfuric acid and 30 h 2 o 2 hydrogen peroxide may be done to make the surface suitable for bonding to the deposited sol typically this step would be performed prior to the last step of rinsing the surface with water in one embodiment the substrate may be placed in piranha solution for 20 minutes followed by soaking in deionized water for 5 minutes the substrate may then be transferred to another container holding fresh deionized water and soaked for another 5 minutes finally the substrate may be rinsed with deionized water and air dried the substrate may be alternatively or additionally prepared by physical treatment in the physical treatment case for one embodiment the surface may be simply cleaned with a solvent and the mechanical action of a cleaning brush or pad optionally a surfactant or detergent can be added to the solvent after which the substrate is rinsed with water and air dried in another embodiment the surface may be first cleaned with water followed by addition of powdered abrasive particles such as ceria titania zirconia alumina aluminum silicate silica magnesium hydroxide aluminum hydroxide particles silicon nitride silicon carbide or combinations thereof onto the surface of the substrate to form a slurry or paste on the surface the abrasive media can be in the form a powder or.