Preparation And Properties Of Multifunctional Composites Based On Polymer/Graphene Assembled Structure

Polymer-based and graphene-based composite materials have attracted more and more attention due to their excellent performance in catalysis,sensing,energy storage and conversion,and biological therapy.Nowadays,most of the research is still to prepare polymer-based or graphene-based composite materials by directly compounding polymers or graphene with inorganic materials and biological materials.In the process of the preparation,there are still unfavorable factors such as large influence from the synthetic environment,harsh synthetic conditions,and secondary pollution to the environment.Therefore,how to prepare multifunctional polymer-based or graphene-based nanomaterials by a simple and facile method is a significant subject.With the development of layer-by-layer(LbL)assembly technology,researchers have been able to use this technology to produce self-assembled nanostructures with high stability,transformable substrates,diverse polymer types.It can be used as a green element in the preparation of polymers or graphene-based nanomaterials.Herein,the reduced graphene oxide(rGO)was used as the assembled template,and a series of polymer-graphene nano-assembled film was prepared via LbL assembly technology.Then,the assembled film was used as template and reducing agent,and more functional polymer-graphene-based nanocomposite structures was prepared in situ.The specific research contents are as follows:(1)Using rGO as substrate,the highly stable rGO/(PEI/PAA)_n multilayer was obtained by alternating assembly of polyethyleneimine(PEI)and polyacrylic acid(PAA)via electrostatic LbL assembly.The bifunctionalized fluffy copper nanoparticles were prepared by in-situ reduction using the rGO/(PEI/PAA)_n multilayer as template and reducing agent.The nanoparticles can fully convert 4-nitrophenol to 4-aminophenol in 8 min,and have Raman signal enhancement with an enhancement factor of 1.84×10~5(calculated with rhodamine 6G as probe molecule).Therefore,the reactants and products in the catalytic reaction can be detected in situ,and the dual function of the catalytic-real-time signal monitoring is realized.(2)We propose a simple method for the facile preparation of spherical cluster-shaped enzyme-containing microparticles.By assembling the rGO/(PEI/PAA)_n multilayer assembled film in the presence of Tween 80 with a biomacromolecule such as an enzyme,spherical or cluster-like particles can be formed.The method is applicable to the preparation of various enzyme-containing microparticles,such as superoxide dismutase,catalase,carbonic anhydrase,hemoglobin,lipase,enhanced green fluorescent protein and the like.The enzyme microparticles also have the function of reversibly regulating the activity of the enzyme by infrared laser(IR).In addition,a cascade reaction network of multi-enzyme microparticles was constructed by simultaneously loading a plurality of enzymes in the microparticles.(3)Polylysine(PLL)and polyaspartic acid(PASP)were alternately assembled on the rGO substrate by electrostatic LbL assembly to obtain a rGO/(PLL/PASP)_n multilayer.Then,the multi-crack large-size single crystal gold micro-sheet was prepared in situ by using the assembled film as a barrier agent and a reducing agent.And realized three functions of Surface Enhanced Raman Scattering(SERS),Surface Enhanced Infrared Absorption(SEIRA),and photothermal conversion on a gold micro-sheet.(4)A nano drug delivery system that is pH-responsive and photoresponsive was prepared by electrostatic assembly of rGO/(PLL/PASP)_n multilayer and doxorubicin(DOX).The drug nanocomposite can be disassembled under acidic conditions to release DOX.In addition,the unassembled PLL can further destroy the cell membrane,making DOX molecules more accessible to cancer cells and killing cancer cells.IR irradiation can promote the release of DOX molecules from the drug nanocomposite and induce in situ photothermal conversion of rGO to further kill cancer cells.(5)Polyethylene glycol(PEG)and PAA were used as assembled materials,which were assembled on the rGO surface alternately to obtain a rGO/(PEG/PAA)_n multilayer via hydrogen bond LbL assembly technology.The rGO/(PEG/PAA)_n multilayer was hydrogen-bonded with DOX to prepare a hydrogen-bonded nanomedicine system with pH response.The drug nanoparticles have good morphology and can overcome the Enhanced Permeation Retention(EPR)effect of the tumor.By adjusting the pH of the microenvironment,cancer cells can be efficiently killed,and the cancer cell survival rate can be reduced to 38.7%compared with the same dose of pure DOX(cell viability is 82.3%).