| Cellulose is the most abundant biopolymer on the earth.It has the characteristics of degradable,recyclable and environmentally friendly.These characteristics have attracted close attention from scholars.Nano-sized nanocellulose made of cellulose not only has the characteristics of cellulose,but also has high specific surface area,high aspect ratio,high crystallinity,excellent mechanical strength and controllable surface chemistry and other properties.The rich hydroxyl groups on the surface of nanocellulose make it a ligand for metal atoms,and can be used as a binding site for nano metal particles in nanocomposites.In this paper,ultrafine gold nanoparticles/CNC?UAuNPs/CNC?composites were prepared by using CNC as template and stabilizer and ethanol as reducing agent.The effects of reaction conditions on the physicochemical properties of UAuNPs/CNC were discussed.The surface effect and photothermal effect were applied to the catalytic redox reaction and photothermal hydrogel respectively,which provide a theoretical basis and technical bas is for the application of CNC-based gold nanoparticles composites.1.The cotton linters were used as raw materials and hydrolyzed by sulfuric acid to prepare CNC.UAuNPs/CNC composites were prepared by reducing HAuCl4 with ethanol as reducing agent and CNC as template and stabilizer under alkaline conditions of 70°C.The effects of pH,CNC concentration and HAuCl4 concentration on the morphology,particle size and dispersibility of UAuNPs were investigated.The results showed that the pH value has the most significant effect on the morphology and particle size of the prepared UAuNPs.With the increase of pH value,the particle size of UAuNPs was getting smaller and smaller,the size distribution was more and more uniform,and the dispersion was getting better and better.Further,at an alkaline condition of pH=12,UAuNPs having an average particle diameter of less than 5 nm can be obtained.The concentration of CNC and HAuCl4 had little effect on the particle size of UAuNPs.The higher the concentration of CNC,the more obvious its effect as a dispersant,and the more uniform the dispersion of UAuNPs.2.The prepared UAuNPs/CNC composites were applied as the catalyst to the redox reaction.The reaction of NH4Cl and NaNO2 was catalyzed at room temperature,and the reaction results were analyzed by chemical kinetics.It was found that the reaction of NH4Cl and NaNO2 which needs to occur at 75°C and above could be carried out at room temperature by using the UAuNPs/CNC composites as catalyst,and the nitrogen generated by the reaction is collected by a drainage gas collection method.The reaction was analyzed by the basic method of chemical kinetics.The reaction was found to be a second-order reaction consistent with the second-order kinetic equation.The kinetic equation was ???=4.12×10-5t+1.52×10-4,and the reaction rate could be determined by the formula to be 4.12×10-5s-1.3.UAuNPs/CNC-based composite hydrogels were prepared by using the prepared UAuNPs/CNCs composite as raw material,N-isopropylacrylamide?NIPAm?as atemperature sensitive monomer,N,N'-methylenebisacrylamide?MBA?as acrosslinking agent and potassium persulfate?KPS?as initiator.The swelling property and photothermal property of the hydrogel were investigated.The results showed that the prepared UAuNPs/CNC-based composite hydrogel has a typical irregular porous structure of hydrogel,which can exhibit the swelling property of hydrogel when changing temperature.The swelling balance ratio of the UAuNPs/CNC-based composite hydrogel was determined to be 22.7,which was an important parameter for determining the swelling property of the hydrogel.The UAuNPs/CNC-based composite hydrogel was compared with the CNC-based hydrogel by the method of specific wavelength irradiation.It was found that the former had higher dehydration rate than the latter,which might be due to the gold nanoparticles in the UAuNPs/CNC-based composite hydrogel had a photothermal effect to cause heat generation,thereby increasing the dehydration rate of the hydrogel. |
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