P. S. Ramesh

Synthesis, structural and optical properties of ZnO and Ni-doped ZnO hexagonal nanorods by Co-precipitation method.

Ni doped ZnO (Zn1-xNixO, x=0.0, 0.03, 0.06 and 0.09) nanorods have been synthesized by Co-precipitation method. Zinc acetate dehydrate [Zn(CH3COO)2⋅2H2O], nickel nitrate [Ni(NO3)3⋅6H2O], sodium hydroxide and poly (vinyl pyrrolidone) (PVP) were mixed together. The morphology, optical and microstructure were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive spectrum (EDS), atomic force microscopy (AFM), UV-DRS spectrum, photoluminescence spectra (PL) and Fourier transformer infrared spectroscopy (FT-IR). The presence of functional groups and chemical bonding is confirmed by FTIR. PL spectra of the Zn1-xNixO systems shows that the shift in near band edge (NBE) UV emission from 321 to 322 nm and a shift in red band (RB) emission from 620 to 631 nm which conforms the substitution of Ni into the ZnO lattice. The investigation conformed that the products were of the wurtzite structure of ZnO. The hexagonal nanorods have edge length 31 nm and thickness of 39 nm. EDS result showed that the amount of Ni in the product is about 9%, these Ni doped hexagonal nanorods exhibits a blue shifts and weak (UV) emission peak, compared with pure ZnO, which may be induced by the Ni-doping different concentrations 0.0, 0.3, 0.6 and 0.9 M. The growth mechanism of the doped hexagonal nanorods was also discussed.

Plant mediated green synthesis and antibacterial activity of silver nanoparticles using Emblica officinalis fruit extract.

A green straight forward method of synthesizing silver nanoparticles (AgNPs) in an aqueous medium was designed using Emblica officinalis (EO) fruit extract as stabilizer and reducer. The formation of AgNPs depends on the effect of extract concentration and pH were studied. The AgNPs was synthesized using E.officinalis (fruit extract) and nanoparticles were characterized using UV-Vis spectrophotometer, the presence of biomolecules of E.officinalis capped in AgNPs was found by FT-IR analysis, shape and size were examined by SEM and XRD. The XRD analysis respects the Braggs law and confirmed the crystalline nature of silver nanoparticles. From XRD the average size of AgNPs was found to be around 15nm. AFM has proved to be very helpful in the determination and verification of various morphological features and parameters. EO fruit extract mediated AgNPs was synthesized and confirmed through kinetic behavior of nanoparticles. The shape of the bio-synthesized AgNPs was spherical. Potent biomolecules of E.officinalis such as polyphenols, glucose, and fructose was capped with AgNPs which reduces the toxicity. The synthesized AgNPs were tested for its antibacterial activity against the isolates by disc diffusion method. The obtained results confirmed that the E.officinalis fruit extract is a very good bioreductant for the synthesis of AgNPs. It was investigated that the synthesized AgNPs showed inhibition and had significant antibacterial against both gram-positive and gram-negative bacterial strains.

Structural, FTIR and photoluminescence studies of Fe doped ZnO nanopowder by co-precipitation method

An investigation on Fe-doped ZnO (Zn1-xFexO, x=0, 0.03, 0.06 and 0.09mM) nanopowder have been synthesized by co-precipitated method annealed at 550°C were reported. The structural, morphological and optical properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectra (EDS) analysis, Atomic Force Microscopy (AFM), UV-Visible spectroscopy, and photoluminescence (PL) techniques, Fourier transform infrared (FTIR) spectroscopy. The XRD spectrum shows all the samples are hexagonal wurtzite structure. The presence of functional groups and chemical bonding are confirmed by FT-IR. The PL spectra of the Zn1-xFexxO systems show that the shift in near band edge (NBE) UV emission from 344.54 to 364.21nm and a shift in green band (GB) emission from 484 to 540nm which conforms the substitution of Fe into the ZnO lattice. UV-Visible measurement showed a decrease in the energy gap with increasing Fe content, probably due to an increase in the lattice parameters. It is also found that these results are in good agreement with other calculated and experimental results.

Biosynthesis of AgNPs using Carica Papaya peel extract and evaluation of its antioxidant and antimicrobial activities.

Waste fruit peel mediated synthesis of silver nanoparticles (AgNPs) is a green chemistry approach that links nanotechnology and biotechnology. Using biological medium such as peel extract for the biosynthesis of nanoparticles is an ecofriendly and emerging scientific trend. With this back drop the present study focused on the biosynthesis of AgNPs using Carica Papaya peel extract (CPPE) and evaluation of its antimicrobial potentials of the nanoparticles against different human pathogens and to investigate the free radical scavenging activity. Water soluble antioxidant constituents present in Carica Papaya peel extract were mainly responsible for the reduction of silver ions to nanosized Ag particles. UV-vis spectral analysis shows surface plasmon resonance band at 430nm. The presence of active proteins and phenolic groups present in the biomass before and after reduction was identified by Fourier transform infrared spectroscopy. X-ray diffraction study shows the average size of the silver nanoparticles is in the range of 28nm, as well as revealed their face centered cubic structure. Atomic force microscope image gives the 3D topological characteristic of silver nanoparticles and the particle size ranges from 10 to 30nm. The average particle size distribution of silver nanoparticles is 161nm (Dynamic light scattering) and the corresponding average zeta potential value is -20.5mV, suggesting higher stability of silver nanoparticles. Biologically synthesized nanoparticles efficiently inhibited pathogenic organisms both gram-positive and gram-negative bacteria. The biosynthesized nanoparticles might serve as a potent antioxidant as revealed by DPPH and ABTS+assay.

Spectral, morphological and antibacterial studies of β-cyclodextrin stabilized silver – Chitosan nanocomposites

The aim of the study is to investigate the antibacterial properties and characterization of β-cyclodextrin (β-CD) stabilized silver - chitosan nanocomposite (Ag-Cts NCs). An effective and eco-friendly technique for the synthesis of Ag-Cts NCs in the presence of a strong stabilizing agent β-CD is described. The well formed nanocomposites were characterized by the Ultraviolet Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Photoluminescence spectroscopy (PL), Scanning electron microscope (SEM/EDS), Atomic force microscope (AFM), High resolution transmission electron microscope (HR-TEM) and Zeta potential measurement (ZP). The results confirmed that the poly dispersed Ag-Cts NCs are less than 15nm in size with spherical shape and show good stability. The antibacterial activity was also investigated and β-CD coated Ag-Cts NCs showed a promising bacterial activity against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus) micro-organism.

Antioxidant activity of chemically synthesized AgNPs and biosynthesized Pongamia pinnata leaf extract mediated AgNPs – A comparative study

Biosynthesis of metal nanoparticles is the present research in the limb of nanotechnology which reduces the toxicity of metal nanoparticles. Green chemistry approach emphasizes that the usage of plant material has offered a reliable, simple, nontoxic and eco-friendly that links Nanotechnology and Biotechnology. Increasing environmental concerns over chemical synthesis routes have resulted in attempts to develop bio-mimetic approaches. The current study deals with novel method for biosynthesis of AgNPs using Pongamia pinnata leaf extract as reducing agent. These biosynthesized nanoparticles were characterized with the help of UV-vis Spectroscopy, Photoluminescence (PL) and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Atomic force microscopy (AFM), Dynamic light scattering (DLS) and Zeta Potential (ZP). Free radical scavenging potential of P. pinnata synthesized silver nanoparticles was evaluated in vitro by using five different assays viz., DPPH, ABT+S, Hydroxyl, Superoxide anion and Nitric oxide scavenging assays are also adopted. Capping of AgNPs by various polyphenolic compounds present in P. pinnata leaf extract appears to be a major contributor to lower toxicity compared to chemically synthesized AgNPs. The surface plasmon resonance shows 425nm and grain size of the AgNPs was measured from XRD and FTIR revealed the bioconjucation of AgNPs. The in vitro antioxidant activity of AgNPs showed a significant effect on scavenging of free radicals. The results suggest that the silver nanoparticles from P. pinnata can be potent natural antioxidants and can be essential for health preservation against oxidative stress related degenerative diseases, such as cancer. The vitality of this study lies in the formation of silver nanoparticles by utilizing the wealth of global ecological resources, eliminating obnoxious and toxic reagents which are hazardous to be handled as well as to be applied.

Synthesis of structural and optical characterization of surfactant capped ZnO nanocrystalline.

The presence of surfactant (CTAB) at three different concentrations viz., (0.5, 1 and 1.5 M) on zinc oxide (ZnO) nanocrystalline at 550°C was synthesized. The optical properties of each surfactant capped zinc oxide nanocrystalline were investigated using UV-Visible absorption. The characterization of these nanocrystalline was performed by X-ray diffractometer Spectrum (XRD), Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and Atomic force microscopy (AFM) and Fourier transformer infrared (FTIR) spectroscopy. The effect of CTAB on the morphology of the ZnO was studied by SEM/EDS which revealed that the diameter of the product is in the range of 42-70 nm. Out of the three surfactant concentrations CTAB (0.5 M) capped zinc oxide nanoparticle has smallest crystalline size of 19.4 nm. Thus, the presence of surfactant on the surface of zinc oxide plays a significant role in reducing defect. The excitonic UV emission has been observed at 275 nm.

Crystal growth, structural, optical, dielectric and thermal studies of an amino acid based organic NLO material: l-Phenylalanine l-phenylalaninium malonate

Good transparent single crystals of L-phenylalanine L-phenylalaninium malonate (LPPMA) have been grown successfully by slow evaporation technique from aqueous solution. Single crystal X-ray diffractometer was utilized to measure unit cell parameter and to confirm the crystal structure. The chemical structure of compound was established by FT-NMR technique. The vibrational modes of the molecules of elucidated from FTIR spectra. Its optical behaviour has been examined by UV-vis spectral analysis, which shows the absence of absorbance in the visible region. Thermal properties of the LPPMA crystal were carried out by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques, which indicate that the material does not decompose before melting. The melting point of grown crystal was observed as 180°C by melting point apparatus. The NLO property was confirmed by the powder technique of Kurtz and Perry. The dielectric behaviour of the sample was also studied for the first time.

Spinel CuCo2O4 Nanoparticles: Facile One-Step Synthesis, Optical, and Electrochemical properties

Nanocrystalline CuCo2O4 spinel structure was prepared by a facile one-step route without any surfactant. The materials physio-chemical properties were systematically investigated with different analytical methods. It is observed that the spinel type CuCo2O4 nanoparticles showed interesting multi-functional features for both optical and electrochemical applications.Typical x-ray diffraction pattern indicates the growth of well-crystalline CuCo2O4 nanoparticles with a cubic spinel structure. From the transmission electron microscope images, a uniform particle distribution with an average size of ~20 nm can be seen. UV-visible spectrum shows the absorption maximum at 264.5 nm and exhibits an optical band gap 4.02 eV. Electrochemical analysis further reveals the pseudo-capacitive behaviour with the specific capacitance of 290 F g−1 at 2 mA cm−2. In addition, the magnetic study of CuCo2O4 substantiates the presence of room temperature weak ferromagnetic ordering at low magnetic field strength.

Synthesis of Cu Loaded TiO2 Nanoparticles for the Improved Photocatalytic Degradation of Rhodamine B

Copper doped Titanium dioxide TiO2 nanoparticles were synthesized by sol–gel method using titanium tetraisopropoxide and copper sulfate as precursors. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), Photoluminesce spectroscopy (PL) and atomic force microscopy (AFM). XRD analysis confirms the formation of anatase titanium dioxide and average particle size was 35nm. Cu– TiO2 exhibits a shift in the absorption edge toward visible spectrum. The rate of recombination and transfer behavior of the photoexcited electron–hole pairs in the semiconductors was recorded by photoluminescence. From SEM spherical shaped nanoparticles was observed. Comparing with pure TiO2 nanoparticles, Cu doped TiO2 photocatalyst exhibited enhanced photocatalytic activity under natural sunlight irradiation in the decomposition of rhodamine B aqueous solution. The maximum 97% of degradation e...