Methylene blue sensitized photoelectrochemical biosensor with 3,4,9,10-Perylene tetracarboxylic acid film as photoelectric material for highly sensitive Pb^sup 2+^ detection

It is of great significance to explore reliable and sensitive methods for the trace detection of lead ions (Pb2+), which may cause serious adverse effect to human health. Herein, we proposed a methylene blue (MB) sensitized signal-on photoelectrochemical (PEC) biosensor with 3,4,9,10-perylene tetracarboxylic acid (PTCA) film as photoelectric material for highly sensitive Pb2+ detection. First, PTCA was modified on the electrode surface, manifesting wonderful film-forming property and acquiring a satisfactory initial PEC signal. Afterward, Pb2+-dependent DNAzyme modified on electrode was cleaved by target Pb2+, followed by hybridizing MB assembled 3D DNA networks with the exposed Pb2+ catalytic strand. Significantly, in the presence of sensitizer MB, the PEC signal of PTCA was extraordinarily increased and the designed biosensor performed a high sensitivity with a detection limit down to 0.03 pM. Therefore, with enzyme-free assembly of MB embedded 3D DNA networks, this dye-sensitized strategy exhibited effective and uncomplicated amplification technology for Pb2+ detection.