Green On-line Preparation And Property Characterization Of Metal Nanomaterials

In this study,Diospyros Kaki Thunb.and Platycladus platycladus extracts were used as plant reducing agents,and microwave-assisted reinforcement was used to successfully establish a simple,green and efficient method for on-line synthesis of gold nanoparticles,AgNP/r GO composites.The synthesis kinetics of AuNPs and AgNP/r GO were studied by UV-Vis.The morphology of the prepared materials was investigated by TEM,XRD and FTIR characterization.The catalytic performance of Na BH₄ for 4-NP degradation was studied.The main studies are as follows:（1）The optimum preparation conditions for the microwave-enhanced on-line synthesis of AuNPs from persimmon extract were as follows:concentration of HAu Cl₄·4H₂O was 2m M,microwave power was 100W,inner diameter of the reaction tube was 1 m M,length was 10m,and injection rate was 2.00 m L/min.The gold nanoparticles with various morphologies,good dispersion and stability were detected by transmission electron microscopy.The active substances in the persimmon extract played an important role in the synthesis of AuNPs and were coated on the surface of AuNPs after synthesis.The results of catalytic experiments showed that the more AuNPs were added,the faster the catalytic reaction was completed,indicating that the material had good catalytic activity.（2）Through the combination of microwave irradiation,flow chemistry and biosynthesis technology,the green,fast and efficient preparation of composite materials was realized.The optimal conditions for on-line synthesis of AgNP/r GO were as follows:extraction concentration 18g/L,Ag NO₃ concentration 5m M,microwave power 700W,reaction tube inner diameter 1mm,length 25m,injection rate 1.5 m L/min.The results show that stable AgNP/r GO can be synthesized quickly under the condition of microwave enhancement.TEM characterization showed that AgNPs exhibited good dispersion on the surface of r GO.FTIR spectra confirmed that phenols and flavonoids in plant extracts played a decisive role in the synthesis of AgNP/r GO.XRD further confirmed the presence of AgNPs on the surface of r GO.The results of catalytic experiments showed that the degradation of 4-NP could be completed within 12min by AgNP/r GO,which had good catalytic activity and was significantly better than that of AgNPs.（3）The optimal preparation conditions for the microwave-enhanced online synthesis of AuNPs from Platycladus Platycladus extract were as follows:the concentration of Platycladus Platycladus extract was 18g/L,the concentration of HAu Cl₄·4H₂O was 1.0 m M,the microwave power was 150W,the inner diameter of the reaction tube was 1mm,the length was 10 m,and the injection rate was 2.00m L/min.AuNPs prepared by microwave on line from the extract of Platycladus orientalis showed good catalytic activity for the catalytic conversi on of tetranitrophenol.The reaction was consistent with the first-order reaction kinetics and the catalytic effect was good.In conclusion,the method established in this paper is simple and efficient,and the research is expected to provide an important reference for the development of new and efficient preparation methods of composite nanomaterials and the development of more green and safe nanomaterials.