Preparation And Properties Of Metal Nanoparticles By Rudbeckia Hirta L. Aqueous Extract

Plant mediated synthesis is one of the most important biological methods for preparing metal nanoparticles,and it is widely recognized as a green synthesis method at present.Rudbeckia hirta L.belongs to Chrysanthemum plant,it is mostly used for landscaping and decoration.However,there are no reports on the preparation of nano-metal materials as a reducing agent.Nanosilver was recognized for its excellent properties in many fields,nano copper and nano-copper oxide was used to replace some precious metal nanoparticles.In order to further develop the scientific value of Rudbeckia hirta L.,in this paper,nano-silver,nano copper and nano-copper oxide were prepared by plant reduction with aqueous extract as reducing agent,then study the properties of nano-silver and nano-copper oxide respectively.The experimental details were as follows:1.The aqueous extract was used to reduce silver nitrate under light conditions,the particle size distribution of the prepared silver nanoparticles was 1.4-3.2 nm,they were small-sized and equally distributed.The optimum technology by single factor experiment was as follows:the volume ratio of aqueous extract to silver nitrate is 6:4,illumination time 20 min,light intensity600 W;The yield was 89.86%.2.The bacteriostatic properties of the nano-silver powder were tested.The results showed that the nano-silver powder had strong bacteriostatic effect on Staphylococcus aureus and Escherichia coli;The bacteriostatic diameter of 1.4 mg nano-silver powder was 22 mm for Escherichia coli and that of 1.7 mg nano-silver powder was 28 mm for Staphylococcus aureus.3.The toxicity of nano-silver sol to Botrytis cinerea,Cylindrocarpon destructans and Fusarium solani were studied.The inhibition rates of 14.29 mg/L nano-silver sol to three ginseng pathogens were 87.04%,76.04%and 81.25%.Virulence regression equation of synthesized silver nanoparticles sol to Botrytis cinerea was y=0.9366x+4.7861,EC₅₀ value were 1.69 mg/L;Virulence regression equation of synthesized silver nanoparticles sol to Cylindrocarpon destructans was y=1.2959x+4.5812,EC50 value were 2.10 mg/L;Virulence regression equation of synthesized silver nanoparticles sol to Fusarium solani was y=1.0222x+4.3436,EC50 value were 4.39 mg/L.4.The nano copper and nano-copper oxide was prepared under light conditions by plant reduction method,the boiled extract as reducing agent and copper sulfate as the source of copper,the results show that when the volume ratio of boiled extract to copper sulfate was 8:2,illumination time 20 min,light intensity 360 W,could get nano copper with a small particle size of 5 nm and the purity of nanometer copper oxide is high,the particle size distribution was5-23 nm after centrifugal and drying,this confirmed by TEM and XRD.The yield was 62.5%.5.The adsorption capacity of lateritic soil,dark brown soil and yellow soil on nano-copper oxide and the effect of temperature on the adsorption capacity were tested.The maximum adsorption capacity of three soils for nano-copper oxide was 17.55 mg/g,18.51 mg/g and 17.56mg/g respectively in 96 h at 25℃;With the increase of temperature,the adsorption capacity of three soils on nano-copper oxide increased with the increase of temperature,the adsorption of nano-copper oxide by yellow soil was most affected by temperature,and the adsorption amount of yellow soil is lower than that of dark brown soil in the early stage,it is gradually higher than dark brown soil with time.The adsorption capacity of nano-copper copper in lateritic soil and yellow soil reached the maximum at 45℃,were 20.41 mg/g and 20.73 mg/g respectively;The adsorption of nano-copper oxide in dark brown soil was greatly affected by temperature at low temperature,and was less affected by temperature at high temperature and adsorption amount reaches 19.43 mg/g at 55℃.Compared with the total amount of nano-copper oxide that enters the soil every year,the amount of nano-copper oxide adsorbed in the soil is limited,so most of the nano-copper oxide in the soil exists in a non-adsorbed fixed form.A large amount of nano-copper oxide will cause soil pollution and the effect of temperature on soil pollution caused by nano-copper oxide is weak.