Application Of Enzyme-loaded Janus Particles In Pickering Emulsion Tandem Catalytic System

Pickering emulsions are widely used in various fields because of the advantages of low emulsifier usage,low cost and easy recovery and separation.In catalytic reactions Pickering emulsion systems can increase the mutual contact area between two phases of substances and improve the reaction rate.Among the materials used to stabilize Pickering emulsions,Janus particles have a unique structure that provides higher desorption energy at the oil-water interface,resulting in stable Pickering emulsions,meanwhile,the surface modification of Janus particles allows them to act as both emulsifier and catalyst to build Pickering emulsion catalytic system.One-pot tandem reaction has good application prospects due to the advantages of easy operation,no need to separate intermediate substances and green energy saving.Enzymes are often used as a green catalyst in important biological and chemical fields,however,the free enzyme can be inactivated under conditions such as high temperature or the presence of organic solvents,thus affecting its c atalytic activity and stability,so natural enzymes can be replaced in catalytic reaction systems by solid-loaded enzymes or by using nano-enzyme materials,however,the Pickering emulsion tandem catalytic reaction system for enzyme-loaded Janus particles has not been reported yet.Due to the unique structure of Janus particles,two enzymatic materials can be immobilized on both ends for tandem catalytic reactions.In this paper,gold nanomaterials are used to replace peroxidase enzymes in contact with organic solvents to reduce the environmental impact on their performance.The sequestering different enzymes to both ends of the Janus pellet both increases the rate of enzyme sequestration and provides a relatively concentrated space for tandem reactions to occur,short ening the diffusion barrier and thus promoting the overall reaction rate,the Pickering emulsion system is also constructed to increase the contact area between the two phase s and improve the reaction rate.The specific results of the study are as follows:（1）Preparation of composite Janus particles Si O2@PDVB/PS-PILs-Au and its catalytic application.Firstly,the snowman-shaped Si O2@PDVB/PS Janus particles were used as carriers,and the polymerizable ionic liquid monomer 1-vinyl-3-butylimidazole hexafluorophosphate was modified on the particle surface using the residual double bond at the PDVB end,The Si O2@PDVB/PS-PILs-Au loaded Au nanoparticles were subsequently reduced in situ by anion exchange with chloroauric acid and the addition of sodium borohydride.Their morphology and structure were analyzed by SEM,TEM,FITR,and XRD characterization.The morphology of the Janus particles before and after the modification was maintained。The catalytic and emulsifying properties of Si O2@PDVB/PS-PILs-Au Janus particles were used to construct the Pickering emulsion catalytic system,and the catalytic performance of the system was investigated using catalytic degradation of methyl orange and catalytic reduction of 4-nitrophenol reactions as probes.The results showed that the best catalytic effect was achieved when the catalytic degradation of methyl orange was carried out at 40μL of H₂O₂ and 15 mg of Janus particles,and the Pickering emulsion system of Si O2@PDVB/PS-PILs-Au Janus particles and H2O2 exhibited higher degradation rate of 95.33%at 6 h compared with the H2O2 system alone,the Janus particles system,and the aqueous phase system.The catalyst could be recovered by simple centrifugation,and the recovered particles maintained good catalytic performance after 5 cycles.When Janus particles was 6 mg,4-nitrophenol could be completely reduced in 12 min,meanwhile,the catalytic reaction rate was higher and the catalytic effect was better compared with the aqueous phase system.（2）Preparation of enzyme-loaded Janus particles GOx-Si O2@PDVB/PS-Au and its tandem catalytic application.Firstly,Si O2@PDVB/PS-PILs-Au Janus particles were used as carriers,and the amino-functionalized Janus particles were obtained by surface modification on the end of silica using 3-aminopropyltriethoxysilane,and finally the glucose oxidase was modified on Janus particles by schiff base reaction using the coupling effect of glutaraldehyde to obtain Janus particles GOx-Si O2@PDVB/PS-Au.The morphology and structure were analyzed by SEM,TEM,zeta potential,EDS and other characterization methods,the morphology of the Janus particles before and after the modification was maintained.A series of different Janus particles were obtained by adjusting the content of HAu Cl4 solution and the content of glucose oxidase during the preparation process,and the emulsification performance of Pickering emulsion of these particles was investigated.The catalytic performance of GOx-Si O2@PDVB/PS-Au Janus particles was subsequently investigated by implementing a one-pot tandem catalytic reaction using methyl orange and glucose as reaction substrates,and the effect of the emulsion system on their catalytic reaction.The results showed that the best emulsification effect of Janus particles prepared when HAu Cl4 solution was added at10 m L and GOx was added at a concentration of 1 mg/m L.The catalytic effect of the Pickering emulsion system based on GOx-Si O2@PDVB/PS-Au Janus particles stabilization was significantly better than that of simply dispersing the particles in the aqueous phase system.The catalytic performance of GOx-Si O2@PDVB/PS Janus particles was also significantly improved compared to the pristine Si O2@PDVB/PS particles,functionalized Si O2@PDVB/PS-PILs-Au and GOx-Si O2@PDVB/PS particles at one end.In the Pickering emulsion system of 3 mg Janus particles,the degradation rate reached 95.67%in 2 h.The highest degradation rate reached 98.56%when the amount of particles was increased to 12 mg.The catalytic reaction rate was higher and the catalytic effect was better compared with the aqueous phase system.