A smartphone-assisted dual-mode sensor for synchronous detection of Microcystin-LR in environmental water via Temperature–Multicolour dual signals

Background The direct reading of a signal is one of the essential requirements for field testing. However, quantitative analysis based on a single signal is prone to false positives and false negatives, compromising monitoring reliability. Therefore, there is an urgent need for a method that can enhance the reliability of detection achieved through simple quantitative signal readings. In this work, a temperature–multicolour dual-mode sensor was fabricated based on the localized surface plasmon resonance and photothermal effects of gold nanorods (Au NRs) to enable synchronous dual-signal detection of microcystin-LR (MC-LR) in environmental water. Results The proposed sensor offers the advantages of sensitive, synchronous, and simple dual-signal reading with the aid of a smartphone equipped with an infrared temperature probe. Both the temperature signal (ΔT) and the multicolour signal (R/G) exhibit strong linear correlations with the concentration of MC-LR. To evaluate the sensor's environmental monitoring performance, environmental water samples from different areas were analysed. Compared with the commercial enzyme-linked immunosorbent assay method, the proposed sensor achieved a lower limit of detection and produced comparable results using only signal readings obtained with a smartphone equipped with an infrared temperature probe, without the need for additional professional equipment. Moreover, excellent recoveries were obtained in the detection of spiked environmental water samples. Significance Two independent signals can be used to validate each other, thereby improving the reliability of detection. Therefore, the proposed smartphone-assisted temperature–multicolour dual-mode sensor shows strong potential for point-of-care testing, particularly in water quality monitoring.