Non-noble metal plasmonic enhanced photoelectrochemical sensing of chlorpyrifos based on 1D TiO2-x/3D nitrogen-doped graphene hydrogel heterostructure.

Low-cost and resource-rich non-noble metal plasmonic materials have attracted tremendous attention as potential substitutes for plasmonic noble metals. Herein, 3D nitrogen-doped graphene hydrogels (NGH) decorated with Ti3+ self-doped 1D rod-shaped titanium dioxide nanorods (TiO2-x NR), 10-25 nm in size, were prepared by a facile one-step method. It was found that the as-fabricated TiO2-x NR/NGH showed a synergistic effect, displaying enhanced photoelectrochemical (PEC) activity by controlling the nanoscale architecture and improving the electronic properties, while also producing abundant oxygen vacancies, which extended the light harvesting and suppressed the recombination of electron-hole pairs induced by the non-noble metal surface plasmon resonance (SPR) effect. In particular, the transient-state photocurrent intensity of the TiO2-x NR/NGH composites was 5.1 times as high as that of pure TiO2. Therefore, the TiO2-x NR/NGH composites could serve as a substrate material for PEC sensing, providing a good basis for selective and sensitive detection of chlorpyrifos. Under optimal conditions, the constructed PEC sensor was found to have several advantages including a broad linear range (0.05 ng/mL-0.5 μg/mL), low detection limit (0.017 ng/mL), and considerable stability, demonstrating that the sensor may offer a promising route in the field of environmental analysis.