Copper oxide nanoparticles (CuO Nps) were synthesized using Millettia pinnata leaf extract via an eco-friendly, cost-effective, reliable, and simple green synthetic pathway and were evaluated for visible light assisted photocatalytic properties by carrying out photocatalytic degradation of dyes. The green synthesized CuO NPs were characterized using various analytical techniques like UV-Visible Spectroscopy (UV-Vis), Fourier-Transform Infrared Spectroscopy (FT-IR), X-Ray Diffractometer (XRD), Transmission Electron Microscopy (TEM) and (EDAX) analysis. The biosynthesis was affirmed by UV-vis spectroscopy exhibiting peak at 290 nm. In FTIR analysis, the chemical bonds corresponds to the phytochemicals responsible for bioreduction activity were identified. Energy dispersive spectroscopy (EDS) showed high intense metallic peak of copper (Cu), oxygen (O) and low intense peaks of carbon (C) due to the capping action of biomolecules of plant extract in CuO NPs formation. The X-ray diffraction (XRD) pattern showed distinctive peaks corresponding to (200), (211) and (310) planes revealing the high crystalline nature of synthesized CuO NPs. The TEM analysis also confirmed that the formed nanoparticles had spherical morphology with uniform symmetry.

Green synthesis is an alternative way to reduce the formation of harmful chemical products by using eco-friendly procedures for the synthesis. Microbial synthesis is one of the green methods to avoid pollution. In microbial synthesis of nanoparticles, microbes are utilized for the conversion of metal ions to nano sized particles. Platinum nanoparticles (PtNPs) exhibit intrinsic antimicrobial, anticancer, and antioxidant activities. Thus they are extensively used for biomedical applications. Bacteria like Acinetobacter calcoaceticus, Calothrix cyanobacteria, fungi such as F. oxysporum and Neurospora crassa, and algae like Padina gymnospora and Plectonema boryanum were reported as reducing agent and stabilizing agent for the microbial synthesis of Pt NPs. Size of the bacteria based synthesized Pt NPs (2 to 3.5nm) were lower when comparing to fungi (2 to 100nm) and algae (25 to 300nm) based synthesized nanoparticles. Pt NPs with cuboidal, hexagon, triangle, quasi spherical, octahedral, and spherical shapes were reported. Variations in shape were due to different kind of microbe used and other conditions of synthesis. The microbial synthesized Pt NPs exhibited excellent antibacterial activity.

Research on plasmonics and their applications in diverse fields has increased significantly over the last decade. The present work primarily aimed to bio-fabricate silver and gold plasmonic nanoparticles and to study their potential as photocatalysts and as DNA binders. To achieve this, Ag and Au NPs were derived employing Peristrophe paniculata and their optical, morphological and structural properties were investigated by standard analytical techniques. The formation rate constant k was 2.58 × 10 À 2 min À 1 and 3.56 × 10 À 2 min À 1 for Ag and Au NPs correspondingly. FT-IR analysis showed that the water-soluble alkaloid, 5-amino-3,4-dihydro-2H-pyrrole-2-carbonitrile was responsible for the stabilization of nanoparticles. Transmission electron microscopic studies disclosed the formation of uniform spherical AgNPs and irregularly shaped AuNPs and the diameter was 9.32 nm and 27.85 nm respectively which was again corroborated by XRD studies (16.64 nm and 36.08 nm). The interaction of ct-DNA with Ag and Au NPs was investigated using absorption spectroscopy in the UV-Vis range and the binding constant values were 2.2 × 10 5 M À 1 and 8.1 × 10 6 M À 1 respectively. The degradation of methylene blue and malachite green by AgNPs was almost 100 % and 65 % respectively in 3 h under sunlight and neutral pH (pseudo first order rate constants were 7.9 × 10 À 3 min À 1 and 1.9 × 10 À 3 min À 1 ). Moreover, the derived AgNPs exhibited mitigate activity against targeted pathogens. Thus, this green technique could be implicit for the eco-friendly synthesis of Ag and Au NPs, and the prepared nanoparticles may be explored as photocatalysts for the degradation of cationic dyes without any added oxidants.