Portable hydrogel test kit integrated dual-emission coordination polymer nanocomposite for on-site detection of organophosphate pesticides

It is of great significance to on-site detection of organophosphate pesticides (OPs) for pollution monitoring and poisoning estimation. Herein, we developed a portable hydrogel test kit for on-site detection of OPs, which is based on the integration of agarose hydrogel with dual-emission coordination polymers (CPs) nanocomposite comprised of Ru(bpy)32+ and zinc (II)-based CPs (ZnCPs) loaded with thioflavin T (ThT). Different from Ru(bpy)32+ with stable fluorescence in acidic environment, ThT@ZnCPs is highly sensitive to H+, which destroys the structure of ZnCPs as a host and quenches ThT@ZnCPs fluorescence. The distinct fluorescence behaviors of Ru(bpy)32+ and ThT@ZnCPs in acidic environment enable the hydrogel test kit to exhibit ratiometric fluorescence responses to acetylcholinesterase (AChE), which hydrolyzes acetylcholine to acetic acid and provides H+. On this basis, combining the inhibition effect of OPs to AChE activity, a ratiometric fluorescence method for OPs detection was established with the hydrogel test kit, and satisfactory results have been achieved in buffered aqueous solutions and apple juice samples. Attractively, by employing smartphone as a signal readout, on-site quantitation of OPs was accomplished with the features of easy to use, portability and low cost, demonstrating a great promising for point-of-care testing in food safety monitoring.