Bio-fabrication Of Noble Metal Nanoparticles For Catalytic And Biological Applications

The protocols based on green chemistry principles and methodologies are considered as the most acceptable and safe procedures for fabricating nano-scale materials and their applications in variety of scientific fields. The prime objective of the current study is to design and construct particles at nano-scale by green, safe and economic procedure and to evaluate their biological and catalytic potentials. Several Chinese plants extracts (in water) were used as reductive and stabilization agents for the formation of silver (Ag) and gold (Au) nanoparticles.Dimocorpus longan seeds extract was used for the green fabrication of Ag-NPs and were characterized. The formation of Ag-NPs was preliminary confirmed by UV-vis spectroscopy. The Ag-NPs have shown the characteristics UV peak around 420 nm,which confirms the formation Ag-NPs. The capped silver in the Ag-NPs had face centered cubic form, which was confirmed by XRD technique. Elemental mapping of the nanoparticles demonstrated the presence of silver as a major element (EDX study).The resulted particles were in the nano-sizes (20-40 nm) as determined by TEM and dynamic light scattering (DLS) studies. The potential bio-molecules that capped the silver atoms were identified by FTIR study, which showed the involvement of protein and phenolic compounds. Particles of silver (from Dimocorpus longan seeds) were applied as green catalyst in chemical reactions using nitro-phenol and methylene blue as test compounds. The silver based fabricated catalyst showed promising activity in reducing the hazardous methylene blue in comparison to commercial silver nanoparticles. Similarly, effective conversion of nitro-phenol to a value added product(aminophenol) was achieved in presence of green Ag-NPs as a catalyst. In addition,the green catalyst was also an efficient agent in scavenging DPPH free radicals, and thus was multiplicative in nature. In summary, the silver based nano-catalyst could be a safe material in detoxifying variety of harmful and hazardous chemicals.In another project, gold salt was fabricated into particle of nano-sizes using coptis chinensis as a source of phyto-chemicals that successfully reduced the respective metal atoms into the corresponding particles. The prepared Au-NPs were successfully characterized by the upper mentioned analytical techniques. Particles of gold (Au-NPs)were utilized as therapeutic agent against multiple bacteria and it was found that these materials are able to damage bacteria by inducing variety of reactive oxygen agents,which in turn destroy pathogenic bacteria. Microscopic analysis of the bacteria treated with nanoparticles showed severe damage to their membrane and leakage of cellular materials especially protein and nucleic acids. All these mechanisms by the developed material (Au-NPs) were considered for their bactericidal action. More importantly, the green fabricated Au-NPs exhibited the desired biocompatibility to human red blood cells, thus making these phyto-chemicals covered particles suitable for pharmaceutical applications. In addition, metal nanoparticles biosynthesized by using natural products from plants extracts could be used as green catalysts for the detoxification of environmental hazardous materials can be scaled up for industrial applications.