Writing with light on titania: Rewritable UV-sensitive surfaces made from doped TiO2 nanocrystals

Researchers have succeeded in creating a coating that can be written on using UV light and the writing can be erased using oxygen. Changes to rewritable paper could help reduce paper waste. The material is made from three non-toxic components and is produced in a single synthesis step.

The team at the University of California, Riverside focused on titania, a light-sensitive, rewritable system. When TiO 2 is irradiated with UV light, it becomes dark due to charge separation and reduction of titanium atoms. Oxygen in the air oxidizes titanium and causes a return to transparency, which is why the color change is not permanent.

The researchers focused on sustaining the change for a long time. They decorated the crystals with diethylene glycol, a non-toxic substance, after using nitrogen as a dopant. The substance added to synthesis as a solvent played a crucial role in the color change, as it scavenged excess electron holes and delayed reoxidation.

The coating formed when applied to glass or paper, it could be written on using UV light. 30 seconds of illumination with a light source at a wavelength of less than 400 nm was all it took to produce the writing. The team emphasized that lamps in the power range of LEDs were sufficient to produce a high level of contrast on the material.

Two light-writing methods were explored by the team. They used a photomask to illuminate the paper or glass. They used a laser pen to write. Both options gave a high-contrast pattern that was stable for many hours and could either be erased by heating or faded because of oxidation. Extending the life of the printing is possible by covering the film surface with a protective layer of a non-toxic polymer, which reduces its exposure to oxygen.

The reusability of the system produced by Yin and his team is the main advantage. The study showed that up to 50 writeerase cycles could be completed. This means that the technology could be applied in a number of fields, for example, daily transport tickets, information boards, data storage, or sensor technology. The simple production method, using common, non-toxic starting materials, and the high degree of compatibility with other materials are highlighted by the authors.

More information: Rashed Aleisa et al, Rapid High‐Contrast Photoreversible Coloration of Surface‐Functionalized N‐Doped TiO 2 Nanocrystals for Rewritable Light‐Printing, Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202203700 Citation: Writing with light on titania: Rewritable UV-sensitive surfaces made from doped TiO2 nanocrystals (2022, May 30) retrieved 30 May 2022 from https://phys.org/news/2022-05-titania-rewritable-uv-sensitive-surfaces-doped.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.