A simple, facile and sensitive photoelectrochemical (PEC) bioassay protocol for metronidazole (MNZ) detection in common oral medicine samples has been proposed under visible-light irradiation, where novel hierarchical coral-like g-C 3 N 4 nanoarchitectures (cg-C 3 N 4 ) have been first explored as PEC sensing platform. Featured with the unique nanostructures (e.g., interlaced porous network architecture, and open boundaries), the as-formed cg-C 3 N 4 nanoarchitectures not only efficiently inhibit the recombination of photogenerated electron-hol...