Construction Of Carbonized Silk Materials Based Nanozymes And Their Applications

Silk,as green biomass with large-scale cultivation,has been widely used as substrates,templates,packaging materials,and precursors of carbon materials because of its excellent physical and chemical properties.However,silk is rarely reported to be functionalized and used in the biocatalytic field.On the other hand,anozymes,nanomaterials that can mimic the biocatalytic activities of natural enzymes,have attracted much attention from scientific researchers and have been used in many fields,including medical diagnosis and treatment,pollution management,and sensors.Among these,carbon materials have been reported as a large class of nanomaterials-based artificial enzymes.In light of that,in this paper,we demonstrate for the first time that N-rich carbonized silk fibroin materials(CSF)obtained through a simple hightemperature carbonization process can serve as efficient peroxidase and oxidase mimics.The effects of carbonization temperature on the enzyme-like activities of carbonized silk fibroin and its activity controllability were further explored.The main conclusions are summarized as follow:1.Silk fibroin has abundant β-sheets,β crystals and amino acid structures,so silk fibroin can be transformed into carbon materials with graphene-like structure through simple high-temperature carbonization.This process change the inactive silk fibroin into multifunctional and active materials,which have excellent photothermal conversion efficiency,as well as excellent peroxidaselike activity and oxidase-like activity.2.The carbonization temperature shows great influence on the enzyme activity of the obtained carbonized silk fibroin.On the one hand,only high-temperature carbonization can trigger such enzyme-like activities from inert SF.On the other hand,the adjustment of the carbonization temperature will turn to the change of the samples’ enzyme-like activity.After carbonization at low temperatures,the as-prepared CSF is still in-active.However,once the carbonization temperature rises to 700℃,the carbonized silk fibroin can be activated.And the enzyme-like activities(including oxidase activity and peroxide Enzyme activity)of carbonized silk fibroin gradually increase with the carbonization temperature rising from 700℃ to 1000℃.Besides,CSF carbonized at the heating rate of 2℃ min-1 exhibits the best enzyme-like activities.3.According to the analysis of the structure and activity,we infer that the unexpected activation of catalytic activities was mainly ascribed to higher carbonization degree,increasing content of N-doping,and the appearance of turbostratic carbon with the change of graphene layers’ stacking structure at high temperatures.4.Based on the excellent photothermal conversion efficiency of carbonized silk fibroin,we can realize the remote regulation of the enzyme-like activities of carbonized silk fibroin using near-infrared radiation.The controllable increase of the biocatalytic activities by regulating the time of near-infrared radiation.