A Zero-Power, Low-Cost Ultraviolet-C Colorimetric Sensor Using a Gallium Oxide and Reduced Graphene Oxide Hybrid via Photoelectrochemical Reactions

Abstract

A zero-power, low-cost ultraviolet (UV)-C colorimetric sensor is demonstrated using a gallium oxide and reduced graphene oxide (rGO) hybrid via photoelectrochemical reactions. A wide bandgap semiconductor (WBS) such as gallium oxide with an energy bandgap of 4.9 eV generates electron-hole pairs (EHPs) when exposed under a mercury lamp emitting 254 nm. While the conventional UVC sensors employing WBS convert the generated EHPs into an electrical signal via a solid-state junction device (SSD), our newly proposed UVC sensory system works by converting EHPs into an electrochemical reaction. The electrochemical reaction causes the degradation of a cationic thiazine redox dye, methylene blue (MB) and thereby spontaneously changes its color. As more rGO was hybridized with the gallium oxide, MB degradation was effectively expedited. Thus, the level of MB degradation under UVC can be evaluated as a UVC indicator. Unlike conventional SSD-based UVC sensors, our responsive colorimetric sensor can be applied where needed inexpensively and zero power.

Graphene Templated DNA Arrays and Biotin-Streptavidin Sensitive Bio-Transistors Patterned by Dynamic Self-Assembly of Polymeric Films Confined within a Roll-on-Plate Geometry

“…The exfoliated GO solution and the GO/AuNPs composite were synthesized by our previously reported method via the modified hydrothermal method [ 30 ]. In a typical procedure, 5 mL GO aqueous solution (2 mg mL −1 ), 0.250 mL of an aqueous 0.01 M solution of gold chloride trihydrate (HAuCl 4 ·3H 2 O, Sigma Aldrich, St. Louis, MO, USA) was added to 7.5 mL of a 0.10 M Hexadecyl-trimethylammonium bromide (CTAB, Sigma Aldrich, St. Louis, MO, USA) solution.…”

Recent Advances and a Roadmap to Wearable UV Sensor Technologies

“…Notably, typical bandgap energies of most of the available semiconductors are within UVA region, and thus they can be excited by all UV radiation. Conversely, only a few semiconductors have a bandgap in the UVC region, thus allowing selective detection of UVC 49. Although it is relatively less common for a semiconductor to have a bandgap in the UVB region, the bandgap energy can be potentially tuned by creating metal–semiconductor or semiconductor–semiconductor junctions or through appropriate doping strategies 19a,20,50…”

Fast-Response Colorimetric UVC Sensor Made of a Ga2O3 Photocatalyst with a Hole Scavenger

“…Recently, colorimetric UVC sensors made of gallium oxide (Ga 2 O 3 ) with an energy bandgap of about 4.9 eV have drawn increasing attention due to their low cost, simplicity, and ability to easily quantify an accumulated dose [ 9 , 10 , 11 , 12 , 13 ]. Although TiO 2 (3.2 eV) and ZnO (3.4 eV) could be considered for photoelectrochemical reactions under UVC radiation, Ga 2 O 3 (4.9 eV) showed a much better UVC sensitivity compared to TiO 2 and ZnO [ 13 ]. These colorimetric UVC sensors are preferred for medical- and health-related products because the accumulated dose of UVC radiation can be visualized via a color change and thus is easily perceptible without expensive external equipment.…”