Fabrication Of Metal Based Nanomaterials By Green Protocol And Their Catalytic And Biomedical Applications

Water plays a pivotal role in sustenance and propagation of life,however,over the last decade water contamination caused by organic pollutants has become a serious global concern whereby severely affecting humans as well as the ecosystem.A number of industries including cosmetic,textile,paper,plastic food processing etc.utilize large amounts of dyes on a daily basis.The direct discharge of these dyes into water bodies(such as rivers and oceans etc.)poses severe environmental concerns and human health issues owing to their nonbiodegradable nature.Moreover,at very low dye concentrations(<1mg/L)these can affect the clarity of water thus rendering it undesirable to use.Likewise,a number of healthcare related infections arising in hospitals are responsible for economic issues in healthcare systems.Many of these hospital acquired infections are a result of drug-resistant or even multi-drug resistant bacteria such as alpha and beta-hemolytic streptococcus.The designing and development of new and potent antibacterial materials against nosocomial infections has been a great challenge for researchers.Apart from this,the major interest in the development of such antibacterial material is to use a naturally occurring substance with strong antioxidant properties.In fact,the main reason for a number of pathological problems including inflammation,skin diseases,aging,cancer and coronary heart diseases is the oxidative stress generated via multiple factors.The designing and development of new materials has gained much attention in order to tackle such ongrowing issues of the world.In order to achieve this objective,researchers have been working on a number of new methods for synthesis and development of novel materials with desired properties.Thus,for such purpose,a number of efforts have been made to develop high functionality materials via combination of multiple constituents with low production cost.The present study is aimed at researching and developing metal-based nanocomposites having enhanced efficiency,high stability and profound reusability,and to study their applicability for various purposes.The green synthesized nanomaterials were systematically characterized by UV-vis spectroscopy,Scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared microscopy(FTIR),High resolution transmission electron microscopy(HRTEM),Thermo gravimetric analysis(TGA),Zeta potential,dynamic light scattering(DLS)and Elemental mapping.The current project is mainly comprised of three different studies which are given below.In this project,facile,economical and eco-benign experimental procedure were adopted to synthesize Au/MgO nanocomposite with the help of Tagetes minuta leaves extract.Phytochemicals present in the leaves of Tagetes minuta were acting as reducing and stabilizing agents to avoid the aggregation of nanomaterials during the preparation of Au/MgO nanocomposite.The as synthesized nanocomposite was systematically characterized by above mentioned techniques.UV-visible spectrum confirmed the presence of MgO and Au due to the presence of two SPR peaks at 315 nm and 528 nm,respectively.Moreover,the Au/MgO nanocomposite exhibited superior photocatalytic,antibacterial,hemolytic and antioxidant activities.Photocatalytic performance tests of Au/MgO nanocomposite was appraised by the rapid degradation of the methylene blue(MB)under UV light illumination.More importantly,after four successive cycles of MB degradation,the photocatalytic efficacy remained unchanged,which ensures a stability of the Au/MgO nanocomposite.Furthermore,the antibacterial tests showed that the advanced nanocomposite inhibited the growth of Escherichia coli,Bacillus subtilis,and Staphylococcus aureus with a zone of inhibition 18(±0.3),21(± 0.5)and 19(±0.4)nm,respectively.The cytotoxicity study revealed that Au/MgO nanocomposites are nontoxic to ordinary healthy RBCs.Interestingly,the Au/MgO nanocomposite also possesses an excellent antioxidant activity,whereby effectively scavenging 82%stable and harmful DPPH.Overall,the present study concludes that eco-benign Au/MgO nanocomposite has excellent potential for the remediation of bacterial pathogens and degradation of MB.The second project of the current study involves the formation of Ag/MgO nanomaterials by reduction procedure using leaf extract of Olea cuspidata.The phytochemicals in leaf extract act as stabilizing and capping agents in reduction of precursor's salts.The characterization study of Ag/MgO nanocomposite revealed that these nanocomposites were highly dispersed,spheroid in shape and having small size.To explore the biological potential of synthesized nanocomposite,antibacterial activities against gram negative(Escherichia coli)bacteria and gram positive(Staphylococcus aureus)has been evaluated.The results indicate that the maximum zone of inhibition observed for E.coli and staphylococcus aureus was 30(±0.8)mm and 26(±0.7)mm respectively,in the presence of as synthesized nanocomposite.The photocatalytic activity in contrary to MB decomposition was seen efficiently.Moreover,the antioxidant nature of green synthesized Ag@MgO nanocomposite was analyzed by destabilizing and scavenging maximum percentage(93%)of dangerous and harmful 2,2diphenyl-1-picrylhydrazyl(DPPH)free radicals.The FT-IR study confirmed the presence of essential and vital components in Olea cuspidata in the form of organic acids(Citrus Acid)which aids in stabilizing the entire structure with enhanced properties.In third project,principles and techniques of green chemistry were implemented which exploit environmentally and economically friendly methods using an accessible and non-toxic medium,that is water and ascorbic acid(Vit.C),which leads to the synthesis of silver/copper oxide(Ag/CuO)nanocomposite.Vit.C was used to furnish the synthesis of excellent and controlled crystalline silver nanoparticles(AgNPs),copper oxide(CuO)and Ag/CuO nanocomposite.Moreover,the structures of all the synthesized nanomaterials were confirmed by a wide range of above mentioned characterization techniques.The prepared nanomaterials were evaluated for catalytic decomposition of methyl orange(MO)in dark,visible light and UV light.The results showed that 20%,50%and 90%degradation of MO in 40 min was observed in dark,visible light and UV light,respectively.To further explore the biological potential of synthesized Ag/CuO nanocomposite,we also evaluated it for an inactivation of bacteria where Escherichia coli has 17(±0.5 mm)and Staphylococcus aureus has 20(±0.6 mm)zone of inhibition in light.The results showed that reactive oxygen species(ROS)were produced in the presence of light and Ag/CuO.These ROS are the main source of inactivation of bacteria.