Preparation Of Silver Loaded Cellulose Nanocrystals And Their Applications In PVA

Antimicrobial material is a kind of functional material with its own inhibition or sterilization properties.Its core component is an antimicrobial agent,whicih is a chemical component with highly sensitivity to bacteria,molds and other microorganisms.Cellulose is a rich renewable natural resource.Its molecules can be manipulated at the nano-scale and antibacterial agents can be added to it to synthesize new nano-scale materials with antibacterial properties.In this paper,rod cellulose nanocrystals(CNC)with length of 100?200 nm and diameter of 10?30 nm were prepared by sulfuric acid hydrolysis.Silver nanoparticles(AgNPs)were prepared by reducing silver nitrate(AgNO3)on the surface of CNC using glucose(C6H12O6)as reducing agents and polyvinylpyrrolidone(PVP)as dispersing agent.With the addition of PVP into the reaction system,AgNPs was evenly dispersed with a diameter of 10?30 nm and no agglomeration were detected.A large amount nano-silver was loaded on cellulose nanocrystals and evenly dispersed.XRD results showed that AgNPs had four obvious diffraction peaks and good crystallization performance,and the characteristic diffraction peaks of CNC could be seen,indicating that the mixture of AgNPs and CNC did not change their crystal patterns.The UV spectrum results showed that the maximum absorption wavelength of AgNPs was 420 nm.When the reaction time increased from 1 h to 5 h,the intensity of the absorption peak was continuously enhanced,and the width of the corresponding half-peak width was narrowed.The color of the solution was gradually changed from colorless to yellowish-yellow,yellow-brown,red-brown and tan,indicating that AgNPs with different particle sizes were generated.Similarly,increasing the dosage of C6H12O6 and AgNO3 concentration respectively can increase the yield of AgNPs.The results of antibacterial test showed that silver-loaded cellulose nanocrystals solution had good inhibition properties to E.coli and S.aureus.In order to improve the overall properties of polyvinyl alcohol(PVA)film,silver loaded cellulose nanocrystals solution was added into PVA solutions to prepare CNC-PVA-AgNPs composite films by solution casting method.Their structure and properties were characterized.The results showed that the tensile strength of CNC-PVA-AgNPs films increased from 49 MPa to 73 MPa compared with pure PVA film.The water absorption is lower.The films showed strong antimicrobial activity against both E.coli and S.aureus.The antibacterial composite aerogel was prepared by freeze drying of PVA solution with the addition of silver-loaded cellulose nanocrystals.The pores of aerogel were evenly distributed.Aerogels formed by liquid nitrogen freezing are generally honeycomb shaped,with certain directivity,compact fiber arrangement and many pores.Compared with pure PVA aerogel,cnc-pva-agnps aerogel has larger specific surface area,more porosity,more adsorption for methylene blue,and higher decolorization rate.CNC-PVA-AgNPS aerogel nitrogen stripping absorption isotherm belong to ? type,with characteristics of the mesoporous.The compressive stress of the silver-loaded aerogel was larger than that of the pure PVA aerogel.The higher the concentration of AgNO3 was,the greater the compressive stress was,and the compressive stress tended to be stable at a certain AgNO3 concentration.Aerogel has good antibacterial activity against E.coli and S.aureus.