Preparation of water-based indium tin oxide sol solution for near-IR reflective film

Indium tin oxide (ITO) nanoparticles with In/Sn = 9:1 (at.%) were synthesized by chemical coprecipitation method in an aqueous solution. The coprecipitate prepared at room temperature showed the crystal structure of indium oxide in X-ray diffraction when it was annealed at the temperature above 300 degrees C under air atmosphere. Reduction process was accomplished to improve the electrical property of ITO powder and it changed powder color from yellow to dark green. Green ITO powder with particle sizes in the range of 15-30 nm was well dispersed by an addition of polyvinylpyrrolidone in an aqueous solution. The dispersibility of ITO sol solution was detected with xi-potential analyzer. Near-IR reflective film was prepared by spin coating method using ITO sol solution. Transmission electron microsopy (TEM) and energy dispersive X-ray spectrometer (EDS) were used to characterize morphology and composition of ITO nanoparticles. Near-IR (NIR) spectrometer was used to determine reflectance on the surface of ITO film in the NIR-radiation region.