V₆O₁₃ Nanobelts for Simultaneous Detection of Cd(II) and Pb(II) in Water

V6O13 nanobelts with good crystallinity and distinct facets were prepared by a facile one-pot hydrothermal method and were first found to possess the peroxidase-mimicking activity. A simple colorimetric sensor using V6O13 nanobelts as catalyst was established for detecting Cd(II) and Pb(II) simultaneously in actual water samples. It was confirmed that V6O13 nanobelts could generate hydroxyl radicals (·OH) from H2O2 to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to produce a blue product. Heavy metals such as Cd(II) or Pb(II) could inhibit the peroxidase-mimicking activity of V6O13 nanobelts, making the sensing solution light blue or even colorless. The catalytic reaction of V6O13 nanobelts was exhibited to be a ping-pong mechanism, and the effect of heavy metals on V6O13 nanobelts was consistent with noncompetitive inhibition. The absorbance variation of a colorimetric sensor is relevant to the amount of heavy metals, which enabled us to easily discriminate whether Cd(II) or Pb(II) exceeded the maximum permissible quantity within 20 min. The limit of detection (LOD) of the constructed colorimetric sensor was determined to be 1.89 μg·L–1 for Cd(II) and 2.11 μg·L–1 for Pb(II). The colorimetric sensor showed distinguished selectivity for other competitive metal ions and was validated for detecting heavy metals in several types of actual water samples.