In-situ growth of CuI/Porphyrin-based graphdiyne (PDY) p-n heterojunction for high-performance cathodic photoelectrochemical sensing

Cathodic photoelectrochemical (PEC) bioanalysis has been attracting great interest due to its excellent antiinterference capability. As a p-type wide energy band gap semiconductor, CuI is regarded as an ideal material for the construction of photocathodes, while its poor stability and narrow light absorption range limit its application as a photoelectrode in PEC sensing. Herein, we report a simple in-situ growth strategy to synthesize CuI/Porphyrin-based graphdiyne (PDY) p-n heterojunction as a photocathode. CuI crystals were firstly deposited on the ITO glass surface via the electrochemical deposition, and CuI could catalyze the in-situ Glaser coupling reaction of 5,10,15,20-tetra(4-ethynylphenyl) porphyrin (TEPP), allowing the growth of PDY film on the CuI crystal surface and forming the p-n heterojunction photocathode. The as-prepared PDY film plays a crucial role in the significant enhancement of PEC performance because of its intense light absorption, and the formation of CuI/PDY p-n heterojunction can efficiently promote the transportation of photogenerated carriers between CuI and PDY thanks to the excellent electrical conductivity and high carrier mobility of highly pi-conjugated PDY. After the growth of PDY, the photocurrent response of PDY/CuI/ITO is almost seven folds higher compared to that of CuI/ITO. Owing to the selective Cu-S bond interaction between L-cysteine (L-Cys) and Cu+, a PEC sensor for the L-Cys determination is developed with a broad linear range from 0.05 to 1.2 mu M and a limit of detection (LOD) of 0.03 mu M.