“…6,7 Over the last few years, multiple new analytical methods have been developed for OTC detection, including electrochemical (EC) methods, 8 photoelectrochemical (PEC) methods, 9 surface-enhanced Raman scattering (SERS), 10 fluorometry (FL), 11 and colorimetry (CL). 12 Among them, colorimetry has received considerable attention due to its advantages of rapidity, easy handling, low cost, and naked-eye readout. 13 Nevertheless, the relatively low sensitivity restricts its application in trace OTC detection.…”