Characteristics And Morphology Regulation Of Gold Nanoparticles Synthesized By Different Fungi

Gold nanoparticles(AuNPs)have wide applications in industrial catalysis,pollution control and medical diagnosis due to their excellent optical and electronic properties as well as favorable stability and biocompatibility.Traditional physical and chemical methods for AuNPs synthesis are usually high-energy-consumption and involved in high energy and high dangerous.Recent years,synthesis of AuNPs by microbes has received increasing attention because of it's environmental-friendly,mild and low-cost nature.Compared with other microorganisms,fungi are considered to have enormous application potential in AuNPs synthesis,because they could secret large and varied biomolecules such as protein and sugars.However,the fungi resources reported for AuNPs synthesis are still limited.In addition,the morphology of AuNPs synthesized by microbes were varied,and it is hard to synthesize AuNPs with specific shape.Herein,the fungi resources isolation for gold nanoparticles synthesis,characterization of AuNPs synthesized by different fungi,as well as shape-controlled synthesis of AuNPs by Aspergillus sp.WL-Au were studied.Main contents and conclusions are as follows:1.In order to enrich fungal resources for nanoparticles synthesis,three fungi,WIN,WL-Go and WL-Au were obtained from the long-time running antibiotics resistance reactor.Based on 26S rRNA gene sequence analysis,strains WIN,WL-Go and WL-Au were respectively identified as Trichosporon montevideense,Trichoderma sp.and Aspergillus sp.Through the study of metal ions resistance of these strains,it was found that Fe3+ could promote the growth of fungi,Au3+,Ag+,Hg2+ inhibited the fungal growth.Meanwhile,atropurpureus products were synthesized in the cultural media with addition of Au3+,which were analyzed as gold particles.The capacity for AuNPs synthesis were verified by incubating microbial cells with HAuCl4.AuNPs of varied shapes,including main of sphere and pseudo-sphere as well as slight of triangle,hexagon and irregular shapes were prepared.The as-synthesized AuNPs were face centered cubic crystals and the(111)plane was in the predominant orientation.The characteristic absorption peaks of AuNPs were at 535 nm,545 nm and 549 nm.2.Since microbial cell-free extracts also could synthesize AuNPs,furthemore,the AuNPs synthesized by cell-free extracts were of good dispersity and uniform morphology.Hence,the characteristics of AuNPs synthesized by cell-free extracts of the isolated strains were investigated.Shperial and pseudo-spherial AuNPs with average sizes of 18.2 nm,10.2 nm and 31.2 nm were synthesized by cell-free extracts of strains WIN,WL-Go and WL-Au,respectively.The characteristic absorption peaks of as-synthesized AuNPs were recorded at 534 nm,565 nm and 532 nm,respectively.XRD analysis showed that the AuNPs were face centered cubic crystals and the(111)plane was in the predominant orientation.FTIR analysis indicated that some functional groups,including-O-H,-N-H,-C=O,-C-H,-C-OH and-C-O-C were involved in AuNPs synthesis and stablizaiton.AuNPs synthesized by cell-free extracts of strains WIN,WL-Go and WL-Au could efficiently catalyze the reduction of nitro-aromatic compounds and azo dyes.The highest catalytic reduction rate was up to 4.04×105 min-1 mmol-1 achieved by AuNPs synthesized by cell-free extracts of strain WL-Au.The decolorization efficiencies of azo dyes were maximally raised 69 folds catalyzed by AuNPs synthesized by strain WL-Go cell-free extracts.3.For further study the process of AuNPs synthesis,the effects of different factors,such as pH,biomass and HAuCl4 concentration,as well as metal ions stimulation on AuNPs synthesis were investigated.Through the experiments of AuNPs synthesis by different microbes,it was found that filamentous fungus WL-Au could synthesize AuNPs with uniform size distribution,smallest average size(9.5 nm)and highest catalytic rate for 4-nitrophenol reduction.Reaction pH could affect the AuNPs synthesized location.Uniform spherical AuNPs were synthesized excellularly at netural and alkalinity conditions.HAuCl4 concentration could affect as-syntheszed AuNPs shape.Spherical and pseudo-spherical AuNPs were synthesized at low concentration(1 mmol/L)of HAuCl4,while spherical and triangular AuNPs were synthesized at high concentration(5 mmol/L)of HAuCl4.Biomass could affect the AuNPs size.AuNPs with size of 25-35 nm were synthesized at 100 mg/L biomass,while AuNPs with size of 5-10 nm were synthesized at 480 mg/L biomass.In addition,the metal ions had significant influences on the synthesized location and shape of AuNPs.Spherical AuNPs with homogenous shape and small size were synthesized by Fe3+ induced cells.Moreover,the ability of extracellular synthesis of AuNPs significantly enhanced by Fe3+ inducing cells.In addition,uniform gold nanorods with good dispersity were synthesized by Pb2+ induced cells.4.Relative uniform gold nanorods were synthesized by Pb2+ induced cells of strain WL-Au.To futher analyze the characterisitics and influence factors involved in gold nanorods synthesis process,SEM,EDS and TEM methods were used to investigate the characteristics of AuNPs synthesized by Pb2+-induced cells.A large amount of gold nanorod were formed by Pb2+-induced active cells and adhered to the surface of mycelium.XRD analysis showed that the AuNPs were face centered cubic crystals and the(111)plane is in the predominant orientation.FTIR analysis indicated that some functional groups,including-O-H,-C-H,amine I and-C-O-C groups were attached on the surface of as-synthesized AuNPs.In addition,inactive Pb2+-induced cells could also synthesize gold nanorods.Furthermore,influences of Pb2+ concentration and biomass on gold nanorods synthesis were investigated.The proportion of gold nanorods was less than 1%when synthesized by 0.02 mmol/L Pb2+-induced cells,while it was more than 85%when synthesized by 0.1 mmol/L Pb2+-induced cells.The AuNPs formed by 25 mg/L biomass were mainly spherical and triangular shape and the amount of gold nanorods was less than 5%.However,the gold nanorod accounted for about 90%when AuNPs synthesized by 100-200 mg/L biomass.