Unusual hexa-nuclear cadmium cluster functionalized phosphomolybdate as effective photoelectrochemical sensor for trace Cr(VI) detection

Photo-assisted electrochemical technique provides a promising approach towards carcinogen chromium(VI) detection, which requires reasonable catalyst design. Herein, an unusual hexa-nuclear cadmium cluster functionalized reductive phosphomolybdate hybrid as photo-electrochemical sensor was designed and synthesized with formula of {[Cd(H2O)2]2[Cd(btmbp)]2}{Cd(P4Mo6O31H7)2}·20H2O (1) (btmbp= 4,4′-bis((1H-1,2,4-triazol-1-yl)methyl)biphenyl), in which the photoactive hexa-nuclear {Cd6} clusters cooperated with reductive phosphomolybdate [P4Mo6O31]12− endow the material with wide light absorption and remarkable redox activity, thus achieving efficient photo-assisted electrochemical Cr(VI) detection performance. Under visible-light assistance, the detection limit (LOD) and sensitivity of Cr(VI) is 4.17 nmol/L (0.225 ppb) and 226.32 µA L/µmol, which is apparently superior to the performance without photo-assistance (6.25 nmol/L and 106.95 µA L/µmol) and far satisfies the demands of world health organization (WHO) for potable water (50 ppb). Moreover, compound 1 showed prominent Cr(VI) detection performance in practical water samples together with remarkable anti-interference capacity and good electrochemical durability. This work provides an important guidance for designing efficient polyoxometalate-based crystalline sensors for Cr(VI) detection.