A dual mode photoelectrochemical sensor for nitrobenzene and L-cysteine based on 3D flower-like CuSnS@SnS double interfacial heterojunction photoelectrode.

In this work, 3D hierarchical CuSnS@SnS flower assembled from nanopetals with sandwich-like CuSnS-SnS-CuSnS double interfacial heterojunction was successfully designed and synthesized on fluoride doped tin oxide (FTO) for photoelectrochemical (PEC) sensor by in situ electrodeposition p-type CuSnS nanoparticles on both inner and outer surfaces of n-type SnS nanopetals. The unique double interfacial heterojunction simultaneously combines 3D flower-like architectures to drastically increase the light trapping and absorption in visible-near infrared range (Vis-NIR), and dramatically inhibites the charge carrier recombination, which is crucial for boosting the PEC activity. Benefitting from the shape and compositional merits, the CuSnS@SnS heterojunction possess dual-mode signal by controlling the electrodeposition time to manipulate the composition ratio of CuSnS and SnS. The CuSnS@SnS/FTO electrode not only exhibits excellent photoeletro-reduction capacity for ultra-sensitive sensing trace persistent organic pollutant (nitrobenzene, NB), but also presents photoeletro-oxidization activity for high selective detection of L-cysteine (L-Cys) without any auxiliary enzyme under the light illumination. Dual mode sensor displayed superb performance for the detection of NB/L-Cys, showing a wide linear range from 100 pM to 300 μM/10 nM to 100 μM and a low detection limit (3S/N) of 68 pM/8.5 nM, respectively. Such a tunable double interfacial heterojunction design opened up new avenue for constructing multifunction PEC sensing platform.