Polylysine-modified MXene nanosheets with highly loaded glucose oxidase as cascade nanoreactor for glucose decomposition and electrochemical sensing

Two-dimensional (2D) nanoreactors with cascade catalytic activity for glucose oxidation and hydrogen peroxide decomposition are prepared via immobilizing glucose oxidase (GOx) on Ti 3 C 2 MXene nanosheets. Amino-rich polypeptide, poly- l -lysine (PLL), is applied to modify the ultra-thin Ti 3 C 2 MXene nanosheets with a compatible surface for GOx immobilization. The PLL-modified Ti 3 C 2 nanosheets possess a positively charged surface and show an excellent GOx loading capacity as high as 50 wt% of the Ti 3 C 2 nanosheets. The physically adsorbed enzymes are then cross-linked with the amine groups in the PLL chains to form a robust GOx-PLL network covered on the MXene nanosheets. The GOx-conjugated Ti 3 C 2 -PLL (Ti 3 C 2 -PLL-GOx) nanosheets showed superior enzymatic activities than the activities of GOx immobilized on an inert porous silica substrate, largely because that the Ti 3 C 2 nanosheets can catalyze the decomposition of the toxic intermediate H 2 O 2 generated from the glucose oxidation. Given the excellent electrical conductivity of Ti 3 C 2 MXene, the Ti 3 C 2 -PLL-GOx nanosheets are further deposited on glassy carbon electrode to construct a high-performance biosensor with a glucose detection limit of 2.6 μM.