Enzyme Activity Regulation And Application Of Noble Metal-based Nanomaterials

Nanozymes have received a great deal of attentions inmultidisciplinary fields because of their advantages over natural enzymes(such as high cost,low stability and difficulty in storage)and promising applications.To date,more than 1000nanomaterials have been reported,including metal oxides,metals,metal sulfides,carbon nanostructures and their combinations,which can mimic enzymes and are considered as potential alternatives to artificial enzymes in clinical diagnosis and disease treatment.Among them,metal based nanostructures have attracted wide attentions due to their advanced synthetic methods,defined and controllable structures,easy surface modification,and potential applications in antibacterial and wound healing.However,because noble metals are expensive and difficult to use on a large scale,how to adjust the enzyme-like activity of precious metal-based nanomaterials and improve the utilization efficiency of materials is an urgent matter to be solved.In this paper,focusing on how to adjust the enzyme-like activity and material utilization of precious metal-based nanomaterials,a series of hybrid nanostructure materials based on noble metals are constructed for the characterization of enzyme-like catalytic performance,and their reaction principles and application scope have been preliminary exploration.The main contents of the research are as follows:(1)The PtRu nano-alloys with different components were prepared by controlling the precursors and using the co-reduction method.We demonstrate that PtRu NPs possess multiple enzyme-like activities(e.g.peroxidase,oxidase,ferroxidase,catalase and SOD)and 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical scavenging activity.The PtRu bimetallic nanozymes therefore show pro-oxidant and anti-oxidant functions.It was found that the enzyme-like activities of PtRu NPs is highly dependent on the Pt/Ru molar ratio and has a similar trend in the order of activity:Pt₉₀Ru₁₀>Pt₇₅Ru₂₅>Pt>Pt₄₀Ru₆₀,indicating the proper alloying Ptwith Ru can enhance both pro-and anti-oxidant capability.By employing the ferroxidase-like activity and catalase-like activity,we verified the application of PtRu nanozymes in the detection of Fe²⁺ions,and tried for the first time to protect Monascus pigments(MPs)from hydrogen peroxide oxidation.(2)The combination of semiconductor and metal nanocomponents represents an effective way for design of photocatalysts with high efficiency.It is expected that this strategy can be applied to design photo-regulated nanozymes.To prove this concept,BiOBr/PtRu hybrid nanostructures have been fabricated by depositing PtRu nanoparticles on BiOBr nanosheets through a templating co-reduction method.The formation of BiOBr/PtRu hybrid nanostructures was confirmed by TEM,XRD and XPS.BiOBr/PtRu hybrid nanostructures exhibited excellent enzyme-like activities(peroxidase,oxidase,ferroxidase)as well as the ability to scavenge DPPH free radicals.When exposed to light irradiation(?>420 nm),it was found that BiOBr/PtRu hybrid nanostructures not only exhibit improved photocatalytic degradation,but also exhibit enhanced peroxidase-and oxidase-like activity.Due to the photocatalytic effect and the higher charge separation and utilization efficiency caused by heterojunctions,a light-enhanced enzyme-like activity mechanism was proposed.(3)The antibacterial application of nanozyme relies on high catalytic efficiency and advanced functions.Plasmon stimulation represents an appealing way to modulate the enzyme-like function that respond to near infrared(NIR)light,but the utilization efficiency of plasma excitation remained relatively low.Herein,by selective deposition of a ceria nanozyme on the ends of Aunanorods,we prepared a dumbbell-shaped Au@CeO₂ hybrid nanozyme with strong surface plasmon resonance(SPR)absorption in NIR range.This spatially separated structure can simultaneously harvest the plasmon-induced hot carriers and thermal effect,thus results in significantly enhanced peroxidase-like activity of Au@CeO₂ hybrid nanostructures upon 808 nm laser.Using ultrafast time-resolved transient absorption and the in situ irradiation XPS technique,we disclosed the transfer behavior of plasmon-induced hot electrons from Auto CeO₂ and leading to the change of Ce³⁺/Ce⁴⁺ratio,which was proposed as the dominant contribution for the enhanced peroxidase-like activity.Benefiting from the plasmon-enhanced peroxidase-like activity,Au@CeO₂ hybrid nanostructures exhibit efficient broad-spectrum antibacterial activity under NIR irradiation.These results indicate a spatio-temporal way to optimize enzyme-like activity through efficient use of plasmon resonance will be of great value for enriching the design and application of nanozymes.