Metal Nanoparticles Greenly Synthesized Using Konjac Polysaccharide And Their Applications

In recent years,the green synthesis of metallic nanomaterials from plant extracts and natural polysaccharides has attracted a lot of attention for researchers.Konjac polysaccharide(KGM)is a polysaccharide widely found in nature and is often used in the food industry and medical field due to its good biocompatibility,degradability and edibility.Polysaccharide has a strong reductive nature,and its molecular structure is suitable for stabilizing nanoparticles.Therefore,in this thesis,metallic nanomaterials were explored by green synthesis method using KGM.In this thesis,metal salts were used as precursors and KGM was used as reducing and stabilising agent to synthesise metal nanomaterials in a green way by in-situ reduction,and the synthesis process was optimised by varying the concentration of KGM,reaction time,reaction temperature and media p H.The as-synthesized metal nanomaterials were characterized by transmission electron microscopy,scanning electron microscopy,X-ray diffraction,infrared spectrometers,particle size meters,and ultraviolet spectrometers etc.The catalysis activity of the prepared nanoparticles were evaluated for the degradation of azo dyes and the reduction of Cr(VI).The main processes and conclusions are summarized as follows.(1)Au NPs/KGM composites were synthesized by hydrothermal method with chloroauric acid(HAu Cl4)as the precursor and KGM as the stabilizer and reducing agent.The experimental processes were optimized shown that the optimum synthesis conditions were W(KGM)=0.12%,C(HAu Cl4)=0.5m M,p H=10,t=30min,T=80°C.In addition the characterization displayed that the synthesized Au NPs/KGM particles were mostly spherical,highly crystalline,with an average particle size of48.72±5.05 nm.The nanoparticles are uniformly dispersed,with good stability due to encapsulated in KGM.The as-synthesized Au NPs/KGM has excellent catalytic activity for the degradation of azo dyes in the presence of sodium borohydride.(2)Ag NPs/KGM composites were synthesized by hydrothermal method with silver nitrate(Ag NO3)as the precursor and KGM as stabilizer and reducing agent.The experimental processes were optimized shown that the optimum synthesis conditions were W(KGM)=0.25%,C(Ag NO3)=0.5m M,p H=11,t=30min,T=60?.In addition the characterization displayed that the synthesized Ag NPs/KGM particles were mostly spherical and highly crystalline,with an average particle size of14.25±3.42 nm.The nanoparticles are uniformly dispersed,with good stability due to encapsulated in KGM.The as-synthesized Ag NPs/KGM has excellent catalytic activity for the degradation of azo dyes in the presence of sodium borohydride.(3)Using palladium chloride(Pd Cl2)as the precursor and KGM as the stabilizer and reducing agent,the Pd NPs/KGM composite was synthesized by hydrothermal method.The experimental processes were optimized shown that the optimum synthesis conditions were W(KGM)=0.3%,C(Pd Cl2)=0.5m M,p H=10,t=30min,T=90?.In addition the characterization displayed that the synthesized Pd NPs/KGM particles were mostly spherical and highly crystalline,with an average particle size of5.98±2.02 nm.The nanoparticles are uniformly dispersed,with good stability due to encapsulated in KGM.The as-synthesized Pd NPs/KGM has excellent catalytic activity for the degradation of azo dyes in the presence of formic acid.