Recognition of the Enzymatically Active and Inhibitive Oxygenous Groups on WO 3- x Quantum Dots by Chemical Deactivation and Density Functional Theory Calculations.

The design and construction of efficient nanozymes are vital for bio/chemo-sensing applications, while the systematic catalytic mechanism study is the prerequisite. Tungsten oxide (WO 3- x ) quantum dots (QDs), an alternative to conventional heavy metal-containing semiconductor QDs, possess peroxidase-like activity but limited catalytic efficiency. Therefore, the functions of the typical oxygenous groups in determining the enzymatic activity of the WO 3- x QDs by target-specifically shielding the carboxyl (-COOH), hydroxyl (-OH), or carbonyl (-C═O) groups, respectively, using a chemical titration method. The results show that the -C═O groups could accelerate the nanozymatic catalysis kinetically, while the -OH ones were the catalytically inhibitive sites, which were further corroborated by the density functional theory (DFT) computations. The application potential of the WO 3- x derivatives with an enhanced catalytic ability was verified via the colorimetric cholesterol sensing. The proposed method based on the benzoic anhydride (BA)-modified WO 3- x QDs with deactivated -OH groups showed a wider linear range and higher sensitivity than those based on the unmodified ones.