An ultrasensitive photoelectrochemical sensor with layer-by-layer assembly of chiral multifarene[3,2,1] and g-C3N4 quantum dots for enantiorecognition towards thyroxine

With a facile preparation for graphitic carbon nitride quantum dots (g-C3N4 QDs), an ultrasensitive photoelectrochemical (PEC) sensor was developed with the supramolecular affinity of chiral multifarene[3,2,1] (CMF) to a hormone drug, thyroxine (T4), for efficient identification of thyroxine enantiomers. In the principle that g-C3N4 QDs was employed to achieve the photocurrent response and the macrocyclic compound served as the supramolecular enantiorecognition for thyroxine, the photoelectrochemical electrode was constructed by layer-by-layer assembly of g-C3N4 QDs and CMF on the surface of ITO (ITO-g-C3N4-CMF QDs). The proposed PEC sensor produced the limits of detection low to 67 pM towards L-T4 and 85 pM towards D-T4 in a concentration range from 0.1 nM to 10 nM, which was superior to the values in pioneering reports with colorimetric or electrochemical methods. With good stability, reproducibility, repeatability anti-interference ability, and acceptable recoveries, the proposed PEC sensor was employed for quantitative determination of L/D-T4 in water, human serum and commercial tablet.