Nano-scale minerals in-situ supporting CeO2 nanoparticles for off-on colorimetric detection of L-penicillamine and Cu2+ ion.

Realizing the high value-added utilization of cheap minerals in environmental catalysis has important practical significance. Herein, four nano-scale minerals, namely halloysite (Hal) nanotubes, palygorskite (Pal) nanorods, and montmorillonite (Mon) and hydrotalcite (LDH) nanosheets, were selected for in-situ supporting CeO2 nanoparticles (NPs) by a facile one-pot hydrothermal method. Among various nanocomposites (NCs), CeO2/Pal behaves the highest peroxidase-like activity, attributing to larger surface area for uniformly dispersing CeO2 NPs and more exposed active oxygen vacancy (Ovac) defects. A novel off-on colorimetric strategy was constructed for detecting toxic L-penicillamine (LPA) and Cu2+ ion with limit of detections (LODs) of 8.37 and 9.80 μM, respectively. Density functional theory (DFT) calculations show that the Ovac defect on CeO2(111) surface can catalyze the heterolytic cleavage of H2O2 into H2O and oxygen radical (•O), instead of being two hydroxyl radicals (•OH) on clean surface. It can also act as trapping site for O2 and H2O adsorption, improving the oxygen affinity and hydrophilicity of CeO2/Pal. This study provides a feasible strategy for designing mineral-based nanozymes and an insight into the possible catalytic mechanism.