Phys.org May 30, 2022
Nanocrystalline TiO2, a semiconductor, darkens when irradiated with ultraviolet (UV) light due to charge separation and reduction of titanium atoms. The color change is not permanent because oxygen in the air re-oxidizes the titanium and causes a return to transparency. To sustain the color change for a longer period researchers at UC Riverside used nitrogen as a dopant and decorated the crystals with a common non-toxic substance diethylene glycol which played a crucial role in the color change. Using light-writing methods they produced patterns or printed text by illuminating the paper or glass substrate through a photomask and freehand writing using a laser pen.Both options gave a high-contrast pattern that was stable for many hours and could either be erased by heating or faded slowly because of oxidation. The life of the printing could be extended by reducing its exposure to oxygen. The study demonstrated that up to 50 write–erase cycles could be completed without any notable loss of contrast. According to the researchers the technology could be applied in several fields where reusable/rewritable surfaces are required, data storage, and sensor technology…read more. TECHNICAL ARTICLEÂ
Surface-functionalized N-doped TiO2 nanocrystals are synthesized with controllable TiIII stability… Credit: Angewandte Chemie International Edition (2022).Â