Invisible 2D image formation with Antimony tin oxide

Abstract

Since most conventional materials use ultraviolet light to read information, fading of the surrounding pigment is inevitable, and invisible materials that use near-infrared light have been proposed. A class of transparent conductive oxide (TCO) has plasma frequencies, ωp of <3 eV. The SPRs for TCO are phenomenologically the same as those observed in the noble metals, despite TCO have lower charge carrier densities (n ≈ 1021 electrons/cm3) than typical metals (n ≈ 1023 electrons/cm3). The ATO nanoparticles were characterized by field emission scanning electron microscope, Vis-NIR spectroscopy, dynamic light scattering. Results indicated that ATO with 10 at. % Sb doping is optimal, with which had lower transmittance in visible region but higher absorption in near-infrared region than 6 at. %. On the other hand, this report searched for the best combination of ATO components and paper substrate color for anti-counterfeiting application.