Wheel-shaped molybdenum(v) cobalt-phosphate cluster as a highly sensitive bifunctional photoelectrochemical sensor for the trace determination of Cr(vi) and tetracycline

Abstract

Developing highly sensitive detection technology for trace heavy metal and antibiotic pollutants in water systems is vital to ensure environmental safety and human health. Here, one wheel-shaped {Co₁₆Mo₁₆P₂₄} cluster-based framework was hydrothermally synthesized with the formula {[Co(H₂O)₆][Co₁₂(BBTZ)₆][(Mo₂O₄)₈(HPO₄)₂₂(PO₄)₂Co₄(H₂O)₈]}·45H₂O (1) (BBTZ = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), which was employed as a bifunctional photoelectrochemical sensor for the determination of trace Cr(VI) and tetracycline (TC). In crystal 1, wheel-shaped {Co₁₆Mo₁₆P₂₄} clusters with a diameter of 19.4 Å act as six-connected nodes to coordinate with BBTZ ligands, extending into a robust three-dimensional framework with a pcu topology. Crystal 1 possesses wide light absorption and excellent redox properties, which displayed remarkable bifunctional photoelectrochemical response towards the Cr(VI) reduction and TC oxidation. The detection limit (LOD) of hybrid 1 for Cr(VI) is 24.62 nM and the sensitivity for Cr(VI) determination is 216.76 μA μM⁻¹. Similarly, hybrid 1 exhibits a high sensitivity of 315.94 μA μM⁻¹ and a low LOD of 33.45 nM for TC detection. These parameters are far superior to the standards set by the WHO and the EU. Importantly, sensor 1 possesses high anti-interference ability and performs well in real lake water and milk samples. This work provides some guidance for the development of promising crystalline photoelectrochemical sensors for practical environmental monitoring.