Structure And Photoinhibition Properties Of KH560@ZnO Doped Starch Composites

In this study,ZnO nanoparticles were prepared by hydrothermal method,zinc nitrate was used as the zinc source,PVP was selected as the surfactant,sodium hydroxide was used to adjust the reaction environment,and the p H of the reaction was controlled from 8.5 to12.5.Hexagonal wurtzite ZnO nanoparticles with different morphologies,such as cylindrical,flake-like and rod-like doping,cone-shaped nano-rod-like,short-columnar and cauliflower-like,were obtained.The results show that the photoluminescence properties and particle size distribution of ZnO nanoparticles are affected by the p H value of the reaction system.When the p H value of the hydrothermal reaction system is 11.5,the morphology of ZnO nanoparticles is uniform,and the particle size distribution is in the range of 100?500nm,with a narrow distribution range,and the average particle size is about 200 nm.The surface of nano-ZnO was modified by?-(2,3-epoxy propoxy)propyl trimethoxysilane(KH560),and the surface of nano-ZnO was connected by epoxy groups,and KH560@ZnO was obtained.The XRD diffraction peaks of the modified ZnO were basically the same as those of the standard spectra,but the intensity of the diffraction peaks increased,and the crystallization structure of nano-ZnO was not changed by the addition of KH560.The infrared spectrum shows that the relative strength of the-OH stretching vibration peak of KH560@ZnO is weakened,and the C-H stretching vibration peak and the characteristic peak of the Si-O bond are greatly shifted,indicating that the hydroxyl groups on the surface of ZnO react with KH560 to form a strong hydrogen bond.Gravity sedimentation analysis showed that the dispersion of modified ZnO nanoparticles was significantly enhanced,and the absorbance ratio(A/A₀)increased from 0.17 to 0.7 after sedimentation for about 7 h,and the time required for complete sedimentation was prolonged.Thermal analysis showed that the mass loss of modified ZnO increased by 3.14%compared with that before modification at 250?600?,and the grafting rate of nano-ZnO was 10.09%.The DSC curve of KH560@ZnO has an exothermic peak at 278.3?,339.6?,and 457.8?,respectively,and the enthalpies are 39.3 J/g,7.3521 J/g and 26.61 J/g,respectively.They correspond to the exothermic decomposition of hydrocarbon long chain carbonization,the exothermic combustion of organic alkoxy group oxidation,the removal of hydroxyl groups and part of the remaining organic matter.By melt blending method,KH560@ZnO was crosslinked with potato starch and epichlorohydrin,and glycerin was added into it.The starch composite semiconductor film material was obtained by gelatinization.X-ray diffraction showed that the crystal structure of starch and ZnO was still maintained when KH560@ZnO was mixed with starch.The infrared spectra of KH560@ZnO starch composite film showed that,compared with the starch film,the-OH vibration absorption peak was wider and the relative strength was stronger,the relative strength of the C-O characteristic absorption peak was stronger,and the C=O stretching vibration peak disappeared,indicating that the epoxy group of KH560participated in the formation of the ether bond in the starch gelatinization cross-linking film formation reaction.SEM-EDS shows that the surface morphology of 12 wt%KH560@ZnO starch composite film is uniform,and no obvious agglomerates appear,indicating that the content of nano-ZnO in the composite film material after modification is significantly increased,and the distribution is uniform,and the agglomeration phenomenon is significantly reduced.The mechanical properties test showed that the tensile strength of 5wt%KH560@ZnO starch composite film reached 30.3 MPa,which was 59%higher than that of starch film.The elongation at break of 7 wt%mixed starch film reached 8.34%,which was 2.77 times higher than that of starch film.The thermal analysis showed that the addition of nano-ZnO had a certain protective effect on the thermal decomposition of the starch composite membrane material.Compared with the starch membrane,the KH560@ZnO starch composite membrane had a new thermogravimetry curve in the stage of 125?225?,and the mass loss rate was 19.47%.This is the heat loss caused by the decomposition of groups formed by the reaction between KH560@ZnO and starch,further demonstrating that KH560 is involved in the bonding reaction of starch membrane gelatinization cross-linking.As KH560@ZnO in the increase of the content of starch in composite membrane materials increase the ultraviolet absorbance of the composite membrane material,composite membrane by uv irradiation,nanometer ZnO ultraviolet light absorption and scattering,and stimulated to produce electronic-hole pair,thus reducing the permeability of ultraviolet light,show KH560@ZnO starch composite membrane has the strong shelter to uv light.The results showed that with the increase of KH560@ZnO content in the composite membrane,the logarithmic period of bacterial growth lagged descend or even disappeared,and the bacterial inhibition rate also increased gradually.The bacterial inhibition rate of 10wt%starch composite could reach 95%,and the water contact Angle was 22.8°compared with that of starch membrane.The contact Angle is as high as 84°.The stronger the hydrophobicity is,the more it can destroy the biofilm and improve the bacteriostatic property.Photoluminescence studies show that the composite material has a UV emission peak of about 400 nm and a green emission peak of about 550 nm.Under the same excitation conditions,the photoluminescence intensity of the composite material increases with the increase of KH560@ZnO content,and the efficiency of electron-hole generation is improved when ZnO is excited,resulting in more bacteria lysis and death.