Photothermal Waveguide-Directed Microreactor for Enhanced Copper Ion Detection from Quantum Dots

Currently, the frontier of nanomaterials has been an extraordinary way for biological and chemical analysis. Using quantum dots (QDs) has served as a promising strategy for copper ion sensing. Various microreactors have been utilized to enhance the sensitivity and stability and shorten the detection time. By integrating a photothermal waveguide into a microfluidic platform, we have developed a photothermal microreactor for enhanced copper ion detection. Temperature gradient, intense vaper microbubbles, vortex, and microdroplets can be simultaneously generated due to the enhanced photothermal effect of graphene oxide and the evanescent field of microfiber. Due to the cooperation of gathering QDs by vortex fields, enlarging surface area on account of droplets, and accelerating molecular motion based on increasing temperature, this system can achieve highly enhanced detection of copper ions in a small sample volume of 2 μL within 5 min, where the detection limit is 3 orders of magnitudes lower than that of the original method. Such a photothermal microreactor is pollution-free and cost-effective with high efficiency and hypotoxicity, being highly potential as a powerful micro-sensing strategy for environmental monitoring as well as chemical analysis.