Pt nanoclusters embedded in doped g-C3N4-x nanosheets to generate tandem nanozymes for glucose colorimetric biosensing

• GOx- and POD-mimicking nanozymes for glucose colorimetric biosensing was developed. • A novel POD-mimicking nanozyme was designed by Pt NCs embedding in defective AKCN. • The unique tandem nanozyme-based biosensor exhibits high sensitivity and specificity. • The enzyme-free biosensor also performs well in cost, stability and simplicity. • The defective AKCN framework brings a new way for advanced polymeric nanozyme design. Typically, smaller noble metal nanoparticles exhibit a greater number of active sites for catalysis; however, their preparation and dispersion stability present significant challenges for nanozyme catalysis in biosensing. In this study, we report defect-assisted Pt nanoclusters (NCs) embedded within KOH/KCl co-doped g-C 3 N 4-x nanosheets (referred to as AKCN, glucose oxidase nanozyme) as a novel peroxidase-mimicking nanozyme (Pt/AKCN) for highly selective and enzyme-free colorimetric glucose biosensing. The Pt NCs were selectively introduced into the defective AKCN containing numerous nitrogen vacancies (NVs) through a facile impregnation-chemical reduction method to obtain Pt/AKCN. Benefiting from the defect-assisted growth of ultrafine Pt NCs with high active surface areas and the Schottky junction formed between Pt NCs and AKCN, Pt/AKCN demonstrates significantly enhanced peroxidase-mimicking activity compared to AKCN in darkness and can be employed for H 2 O 2 colorimetric detection utilizing TMB as a chromogenic substrate. Coupled with the photoenzymatic properties of glucose oxidase-mimicking AKCN under visible light irradiation, Pt/AKCN also facilitates selective glucose colorimetric detection without interference from other sugars. The well-designed tandem nanozyme-based glucose colorimetric sensor exhibits a strong linear relationship over the range of 0.5 to 500 mmol L −1 , with a detection limit of 0.17 mmol L −1 , meeting the requirements for urine glucose detection in diabetic patients. This work reveals an innovative strategy for preparing ultrafine Pt NCs on defective g-C 3 N 4-x supports while highlighting the design potential of polymeric nanozymes with enhanced catalytic performance.