Blue-Green Emitting Cationic Thiazole Surfactants-Based Paper Devices for Highly Sensitive and Selective Fluorescence Detection of Chromium Oxyanions in Wastewater

•Blue and green emissive cationic thiazole sensors were constructed.•The sensors were successfully applied in real samples with acceptable results.•Portable and low-cost paper is used to visually detect as low as 5 nM of Cr(IV).•The feasibility of using a smartphone to determine Cr(VI) has been established.