A new Z-scheme heterostructure of 3D zinnia flower-like ZnIn2S4/Au/In2S3 rod derived from In-MOF for sensitive Cr6+assay based on redox process-induced photocurrent alteration

Hexavalent chromium (Cr6+), as one heavy metal ion contamination, poses the serious threat to environment safety and human health deriving from its toxicity and pathogenicity. Here, a new Z-scheme heterostructure comprising three-dimensional (3D) zinnia flower-like ZnIn2S4, Au particles, and In2S3 rod derived from MIL-68 (In) was synthesized through layer-by-layer assembly approach. The resulting Z-scheme heterostructure (labeled as ZnIn2S4/Au/In2S3) demonstrated exceptional optoelectronic feature. The Au particles acted as an electronic shift medium between 3D zinnia flower-like ZnIn2S4 and In2S3 rod, promoting the efficient transfer of photo-excited carriers, thus mitigating their recombination. More significantly, the hole consuming agent ascorbic acid (AA) further enhanced electron-hole separation. Consequently, Z-scheme heterostructure of ZnIn2S4/Au/In2S3 could yield a notably high initial photocurrent signal. Leveraging the redox process between Cr6+ and AA, which led to the decreased content of AA and photocurrent alteration, a sensitive and facile photoelectrochemical (PEC) sensor for Cr6+ assay was designed. Without the requirement for immobilization of biological probe on the sensing interface, this PEC sensor was characterized by the simplified fabrication steps and reduced investment costs. The results revealed a linear detection range spanning from 0.01 to 500 mu M with a detection limit of 0.48 nM, enabling it highly suitable for precise detection of Cr6+ in food and environmental water samples. This technique opened up possibilities for progressions in PEC sensing for heavy metal ion pollutants.