Preparation And Application Of Novel Janus-like Graphene Oxide

Janus nanoparticles are a kind of nanoparticles with asymmetric structure gradually developed in the past decade.Their asymmetric structures endow them with anisotropy in spatial structure and physical and chemical properties,showing excellent properties that isotropic materials do not performance.They are superior to ordinary nanomaterials in the fields of semiconductors,catalysis and biomedicine.Graphene,as a kind of two-dimensional carbon nanomaterials rising in recent years,has excellent optoelectronic properties and a wide application prospect in the fields of materials,energy and biomedicine.To obtain Janus graphene nanosheet with different functional modifications,the traditional method of preparing Janus graphene nanosheets are to chemically modify the opposite side of the sheet.In this paper,a new type of Janus graphene oxide nanosheet with different oxidation degrees along the plane direction of the sheet was prepared by simple ultrasonic treatment of edge-oxidized graphite.The surface asymmetric chemical structure of the novel Janus graphene oxide was systematically studied by AFM and Raman imaging,and its interfacial self-assembly behavior and its application in nanofiltration membrane and hybrid hydrogel materials were investigated.The main research content is divided into the following three parts:The first part of the work is the preparation and characterization of a new type of Janus graphene oxide nanosheet（JGO）.In this part,JGO was successfully prepared by the combination of partially intercalated graphite oxide and strong ultrasonic breaking.Compared with the traditional asymmetric chemical modification,the preparation and structure regulation of JGO are carried out at the same time,which effectively avoids the sheets reaccumulation in the modification process.Through the characterization of the chemical composition,morphology and structural properties of JGO nanosheets,it is confirmed that the surface chemical properties of JGO nanosheets are asymmetrical and there are obviously different oxidation regions on JGO nanosheets.Because of its unique amphiphilic,the prepared JGO particles have the emulsifying effect of Pickering and have good stability to the emulsified oil-water interface.In addition,we firstly observed that JGO formed an eyelash-like liquid crystal arrangement at the oil/water interface.The second part of the work is studying the effect of oxidation degree of GO on the filtration performance of nanofiltration membrane.On the basis of the first part of the work,a series of low oxidation GO films were prepared by adjusting the amount of potassium permanganate and their respective thin films were prepared by vacuum filtration.Compared with the traditional GO nanofiltration membrane,the low oxidation GO membrane showed high flux(53.4 Lm^-2h^-1bar^-1)and dye rejection rate（>99%）.The traditional GO formed a layered and regular membrane structure due to the ordered self-assembly in the vacuum filtration process,so they show low water flux owing to small interlayer spacing.While other GO layers with lower oxidation degree are disorderly self-assembled during vacuum filtration,resulting in GO nanofiltration membranes with disordered layered structure,which show high flux and dye rejection rate.The third part is to prepare JGO/cellulose/CMC hydrogel.In this part,amphiphilic JGO rigid particles were added to cellulose/CMC hydrogel to improve the mechanical properties of pure cellulose hydrogel.We found that JGO has good compatibility with alkaline urea cellulose aqueous solution.The mechanical property data showed that the compressive strength of pure cellulose hydrogel was greatly improved by the addition of JGO,and the hybrid hydrogel showed excellent compression resilience.The dense hydrogen-bonded cross-linking network of pure cellulose hydrogels makes it difficult for water molecules to enter in a short time,so there is almost no obvious change under water.The addition of JGO reduces the cross-linking network density of the original hydrogel,which makes it easier for water molecules to enter,thus showing a rapid self-recovery behavior macroscopically.