Preparation And Modification Of Starch Nanoparticles And Their Composite With Graphene

Nanomaterials is one of the hottest topics in the fields of materials science.Starch nanoparticles prepared from starch are widely used in many fields because of their availability,renewability,low price,good biological safety,biocompatibility and biodegradability.The study of starch nanoparticles(SNP)has great significance to the application and promotion of starch and the enrichment of nanomaterials.In this work,the preparation method of starch nanoparticles has been investigated in order to improve the preparation rate of starch nanoparticles.Study the effect of dialdehyde modification process on the properties of starch nanoparticles,in order to obtain high-quality dialdehyde starch nanoparticles.Moreover,starch nanoparticles and dialdehyde starch nanoparticles were applied to graphene to study its influence on the properties of graphene,especially the induction,energy storage,and adsorption properties.(1)In this paper,starch nanoparticles(SNC)prepared by mixed acid are compared with those prepared by sulfuric acid.When the total hydrogen ion concentration is 6.32 mol/L,the rate of preparing starch nanoparticles by mixed acid is much higher than that of sulfuric acid acidolysis,and as the content of hydrochloric acid in the mixed acid increases,the rate of preparation will also increase.Starch nanoparticles prepared by the mixed acid method and the starch nanoparticles prepared by the sulfuric acid method have no obvious difference in particle morphology,group structure,and surface element changes.When the ratio of sulfuric acid and hydrochloric acid to provide H ion concentration is 1:1,it only takes 1 h to prepare starch nanoparticles,and the hydrolysis rate has reached 95.38%,which is the hydrolysis degree of sulfuric acid hydrolysis for 9 days,and the hydrolysis rate has increased by more than 200 times Moreover,the starch nanoparticles prepared by the mixed acid method and the starch nanoparticles prepared by the sulfuric acid method have no obvious difference in particle morphology,group structure,and surface element changes.When the ratio of sulfuric acid and hydrochloric acid to provide H ion concentration is 1:1 to hydrolyze starch for more than 1 h,the crystalline structure of starch will change to a V-shaped structure,and it will eventually become V-shaped.However,the emulsification experiment found that starch nanoparticles prepared with too high hydrochloric acid content had poor stability when preparing Pickering emulsions.Therefore,when preparing starch nanoparticles by the method of mixing hydrochloric acid and sulfuric acid,although an increase in the content of hydrochloric acid will improve the preparation efficiency,an excessively high content of hydrochloric acid will result in a transformation of the crystal structure and a decrease in emulsification properties.(2)In this paper,starch nanoparticles are combined with graphene to prepare a composite film.The experimental results show that starch nanoparticles can be well dispersed in graphene.The introduction of starch nanoparticles has a greater impact on the structure,thermodynamic properties and surface elements of graphene.Due to the excellent mechanical properties of starch nanoparticles,the tensile strength of the composite film is improved after being compounded with graphene.However,as the addition rate of starch nanoparticles increases,the elongation at break of the composite film decreases.We found that 10% RGO-SNC has a strong sense of temperature,humidity,bending and stretching,other deformations and water.Therefore,the 10% RGO-SNC prepared in this article has certain potential in sports and health monitoring.(3)Physicochemical and emulsification properties of dialdehyde starch nanocrystals(DASNC)and dialdehyde starch nanoparticles(DASNP)were measured in this study.The starch nanocrystals(SNC),which are prepared by sulfuric acid hydrolysis,were oxidized by sodium periodate to obtain the DASNC.The DASNP were prepared by gelatinization and alcohol precipitation of dialdehyde starch.After oxidization by sodium periodate,the SNCs and SNPs became smaller and more suitable for dispersion.X-ray diffraction results showed that the crystal pattern of the SNC was preserved after oxidation.However,only a single broad peak at the Bragg angle of the DASNP was observed.The SNC and DASNC can form Pickering emulsions,but the emulsions stabilized by the SNP and DASNP could be easily broken.The preparation methods for the two kinds of dialdehyde starch nanoparticles are different,so their structures,properties and applications are different.(4)In this work,graphene oxide(GO)nanosheets are combined with dialdehyde starch nanocrystals to form highly porous,mechanically robust,compressible aerogels,which can be used as supercapacitor electrodes and efficient adsorbents.The introduction of the DASNC to GO was confirmed by SEM,TEM,FT-IR,Raman,XPS,and TGA.After DASNCs attached to the reduced graphene(RGO),the aerogel skeleton became more robust,resulting in high mechanical properties.DASNC can effectively prevent irreversible self-stacking between graphene nanosheets;therefore,the electrochemical performance of reduced graphene oxide was fully realized,and the specific capacitance was increase from 198 to 316 F/g.The hybrid aerogels were also used to remove four dye contaminants.Results showed that DASNCs-RGO hybrid aerogels(SRGO)had high adsorption capacities toward rhodamine B(RB)and crystal violet(CV)due to the highly porous structure and high specific surface.The highest adsorption capacities toward RB and CV of SRGO were 539 mg/g and 318 mg/g.The results of adsorption kinetics showed that there was chemisorption mechanism interaction between the hybrid aerogels and dye contaminants during the adsorption process.