Mechanism On Nano-gold Synthesis By Microbe And Screened Biomolecule

The recent years saw the application of biosorption in controlling and removingmetal pollution being paid more and more attention. Meanwhile, the biosynthesis ofnanoparticles has become a hot topic due to a growing need to developenvironmentally benign technologies in material synthesis. As we all know, metalnanoparticles, because of its size and shape-dependent physicochemical andoptoelectronic properties, have been widely used in catalysis, biosensing, recordingmedia and optics. Under this circumstance, biosynthesis of gold nanoparticles bymicroboils like Bacillus subtilis was carried out in this paper. In addition, thereduction mechanism and controlled grow of gold nanoparticles were furtherinvestigated. On this base, function groups on the cell wall were confirmed and thescreened biomolecule including those function groups was used to improve the yieldof gold nanoparticles. So, tyrosine was screened to form gold nanoparticles in thispaper. What is more, the mechanism and effects of environmental factors onnanoparticles morphology were studied.Firstly, biosorption of Au （III） using Bacillus subtilis was investigated undervarious experimental conditions: pH, biomass concentration, contact time andtemperature. Then, this study turned to the equilibrium, kinetic and thermodynamicreactions of Au （III） biosorption. The results revealed that Au （III） biosorption wasfound to better fit the Freundlich model and pseudo-second-order kinetic model. Thethermodynamic parameters revealed this biosorption was exothermic andspontaneous.Besides, the environmental factors, including pH, temperature and reaction time,played an important role in controlling the size and morphology of gold nanoparticles.The result of XPS analysis indicated that the reaction route of Au3+by Bacillussubtilis is AuCl₃·HClâ†'AuClâ†'Au⁰. In the study of nano-gold biosynthesis bytyrosine, it speculated that many thin gold nanoparticles accumulated together to formthe large nanoparticles of special shapes.The results indicated that the screened biomolecule as biological reductant couldmuch improve the yield of nano-gold. However, the morphology of nano-gold synthesized by screened biomolecule differed from that Bacillus subtilis, which wasattributed to the influence of other groups on the function ones on the cell wall. Inaddition, self-assembling mechanism of nano-gold synthesized by Bacillus subtilisand tyrosine were different.Microbe was gradually substituted for the screened biomolecules as biologicalreductants, such as protein, amino acids and DNA and so on. Therefore, specialfunctional protein could be synthesized by DNA recombination and genic mutationthchnology, or the existing biomolecules were improved by the chemical modificationin order to obtain the effective biological reductants and form the ideal nano-gold. So,results from this paper could become the important base for the study, which utilizedthe screened biomolecule as effective biological reductant to realize the controlledgrowth of nano-gold.