A portable photocatalysis-based, smartphone-assisted colorimetric device for on-site Cr(VI) detection

On-site detection of Cr(VI) is highly desirable due to its potential threat to ecological environment and human health. Herein, a portable photocatalysis-based, smartphone-assisted colorimetric device, which integrated a UV light torch, a sample chamber and a smartphone, was developed by 3D printing technology for on-site Cr(VI) detection. A sensing membrane was prepared by incorporating chromogenic substrate (XTT), photocatalyst (CACN), silica gel, polyvinyl alcohol (PVA) into polyester fiber membrane. Under the irradiation of UV light, XTT was catalytically reduced into orange formazan by CACN. In the presence of Cr(VI), Cr(VI) was also reduced by competing with XTT to capture the photoelectrons, leading to the fading of orange color. After taking photo by a smartphone, the RGB values of the sensing membrane were obtained by a color picking APP. The portable colorimetric device achieved a limit of detection for Cr(VI) as low as 0.59 μmol L −1 . Finally, the portable colorimetric device was applied for on-site detection of Cr(VI) in real environmental samples and chromium-containing wastewater samples. This work not only provides a portable detection device for on-site Cr(VI) detection in the environment but also extends the photocatalysis for sensing application.