Photoswitching-Induced Frequency-Locked Donor–Acceptor Fluorescence Double Modulations Identify the Target Analyte in Complex Environments

Precisely identifying biological targets and accurately extracting their relatively weak signals from complicated physiological environments represent daunting challenges in biological detection and biomedical diagnosis. Fluorescence techniques have become the method of choice and offer minimally invasive and ultrasensitive detections, thus, providing a wealth of information regarding the biological mechanisms in living systems. Despite fluorescence analysis has advanced remarkably, conventional detections still encounter considerable limitations. This stems from the fact that the fluorescence intensity signal (I) is sensitive and liable to numerous external factors including temperature, light source, medium characteristics, and dye concentration. The interferences exasperatingly undermine the precision of measurements, and frequently render the signal undetectable. For example, fluorescence from single-molecule emitters can be measured on glass substrates under optimum conditions, but single-molecule ev...