Smartphone-Integrated Fluorescent Ratiometric Sensor Employing a Copper Nanocluster/Carbon Dot−Polyvinyl Alcohol Hydrogel for On-Site Visual Detection of Histamine

Abstract Biogenic amines (BAs), especially histamine, are important indicators for assessing the quality and edibility of aquatic products. Rapid detection of histamine is of great significance for food safety. Herein, a smartphone-integrated fluorescence sensor based on Cu NCs/CDs and a Cu NCs/CDs-PVA hydrogel sensor was designed for histamine ratiometric detection and on-site monitoring of the shrimp spoilage process. The self-assembled induced luminescence of copper nanoclusters (Cu NCs), first prepared with 3,5-bis(trifluoromethyl)benzenethiol (TFBT) as a ligand, was used for the sensitive detection of histamine by the interaction between the metal and the imidazole group. The fluorescence emission peak of CDs could be used as a reference peak because it has no overlap with the emission of Cu NCs. The fluorescence peak of CDs hardly changed, and the fluorescence of Cu NCs decreased with the addition of histamine, which enabled histamine fluorescence ratiometric detection. This method exhibits an excellent linear relationship between the fluorescence intensity ratio (F437/F605) and histamine concentrations ranging from 40−120 μM, with a detection limit of 0.37 μM. Furthermore, Cu NCs/CDs were introduced into the hydrogel recognition system, and the Cu NCs/CDs-PVA hydrogel was utilized for histamine determination and on-site monitoring of shrimp spoilage. The as-prepared hydrogel sensor offers a convenient method for on-site monitoring of food safety.