TAGRA 2025

Nanomaterials based on WO3-x have emerged as highly promising materials due to their unique chemical and physical structures. The intentional introduction of oxygen vacancies in these nanostructures significantly enhances their optical and electronic properties. For instance, they are used in the fabrication of optical and gas sensors, smart windows with photochromic capabilities, and photocatalytic systems for converting carbon dioxide into clean fuels [1-3].
Hexavalent chromium (Cr(VI)) is a highly toxic heavy metal ion widely used in industries such as stainless steel, automotive parts, and leather production. Its release into the environment poses severe risks, as it can contaminate groundwater and accumulate in aquatic organisms like fish, eventually entering the human body through consumption. Excessive intake of Cr(VI) is associated with serious health hazards, prompting strict regulatory limits in wastewater and food safety standards [4]. There is an urgent need for simple, rapid, and sensitive detection techniques.
Based on the research presented, this study successfully developed a simple and effective colorimetric method for the precise determination of Cr(VI). The method is based on the direct reaction of Cr(VI) with WO3-x nanoparticles synthesized via a UVA irradiation method. Under UVA light irradiation in a hydrochloric acid solution containing choline chloride, WO3-x nanoparticles (blue color) were produced. The intensity of the color, which decreased proportionally with the concentration of Cr(VI), was monitored spectrophotometrically. The proposed method demonstrated a wide linear range for Cr(VI) quantification from 1 to 30 µM, making it suitable for detecting trace levels of Cr(VI) with limit of detection equal to 0.22 µM. The method exhibited excellent selectivity for Cr(VI) over other potential interfering ions. The practical applicability of this colorimetric sensor was validated by successfully determining Cr(VI) concentrations in various real water samples, including tap water, river water, and lake water.