Influence of RE (Pr3+, Er3+, Nd3+) doping on structural, vibrational and enhanced persistent photocatalytic properties of ZnO nanostructures.

Rare earth (RE- Pr, Er and Nd) doped ZnO nanostructures were prepared through simple wet chemical precipitation route. The RE doping induced interesting morphological transition from spherical to flower like structures were analyzed. The X-ray diffraction (XRD) measurements revealed that the prepared materials were of highly crystalline in nature and RE dopant ions did not altered the crystal structure of ZnO. The microstrain of ZnO was altered with respect to the nature of dopants. In the case of the Pr doped ZnO, X-ray photoelectron spectroscopy (XPS) analysis confirmed that the dopant (Pr) ions successfully substituted in the ZnO lattice. Raman spectra revealed RE doping induced lower energy side shift and variation in intensity of the peaks related to the characteristic phonon modes of ZnO. In the case of Nd doped ZnO nanostructures, dopant induced suppression in classical Raman modes and evolution of multiphonon related modes were identified. Optical diffuse reflectance spectral (DRS) measurements, along with the characteristic excitonic band of ZnO, other bands associated to the transitions of 4f energy levels related to the RE ions were observed. The partially filled 4f orbitals led to the enhanced photocatalytic activity in RE doped ZnO nanostructures. The observed enhanced photocatalytic activity in RE doped ZnO when compared to bare ZnO was discussed. The decolorization efficiency of MB ensued the following order 96 > 94 > 86 > 78% for ZnErO, ZnNdO, ZnPrO and ZnO, respectively.

Altered electrochemical properties of iron oxide nanoparticles by carbon enhance molecular biocompatibility through discrepant atomic interaction.

Recent advancement in nanotechnology seeks exploration of new techniques for improvement in the molecular, chemical, and biological properties of nanoparticles. In this study, carbon modification of octahedral-shaped magnetic nanoparticles (MNPs) was done using two-step chemical processes with sucrose as a carbon source for improvement in their electrochemical application and higher molecular biocompatibility. X-ray diffraction analysis and electron microscopy confirmed the alteration in single-phase octahedral morphology and carbon attachment in Fe3O4 structure. The magnetization saturation and BET surface area for Fe3O4, Fe3O4/C, and α-Fe2O3/C were measured as 90, 86, and 27 emu/g and 16, 56, and 89 m2/g with an average pore size less than 7 nm. Cyclic voltammogram and galvanostatic charge/discharge studies showed the highest specific capacitance of carbon-modified Fe3O4 and α-Fe2O3 as 213 F/g and 192 F/g. The in vivo biological effect of altered physicochemical properties of Fe3O4 and α-Fe2O3 was assessed at the cellular and molecular level with embryonic zebrafish. Mechanistic in vivo toxicity analysis showed a reduction in oxidative stress in carbon-modified α-Fe2O3 exposed zebrafish embryos compared to Fe3O4 due to despaired influential atomic interaction with sod1 protein along with significant less morphological abnormalities and apoptosis. The study provided insight into improving the characteristic of MNPs for electrochemical application and higher biological biocompatibility.

Surfactant assisted control on optical, fluorescence and phonon lifetime in α-Bi2O3 microrods.

We report preparation of pure and surfactant added α-Bi2O3 microrods through simple chemical method at moderate temperature. Cetyltrimethyl ammonium bromide (CTAB) is used as a surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, UV-Vis absorption and photoluminescence (PL) measurements were carried out to understand the effect of surfactant (CTAB) on structural, phonon and optical properties of the prepared material. It is observed that the crystallite size, optical band gap and the structural defects (oxygen vacancies) decreases due to the effect of surfactant. Raman spectral studies exhibit various phonon modes of Bi2O3 and also decrease in the FWHM of the phonon modes is observed after the addition of CTAB.

Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles.

We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample.

Synthesis and concentration dependent antibacterial activities of CuO nanoflakes.

We report, synthesis and antibacterial activities of CuO nanoflakes. CuO nanoparticles are prepared at room temperature through sol-gel method. X-ray diffraction studies show the particles are monoclinic (crystalline) in nature. Scanning electron microscopy (SEM) images clearly show that the prepared particles are flake like in structure. Fourier transform infrared (FTIR) spectra exhibits three different bands that correspond to the Au and Bu modes. Antibacterial studies were performed on Shigella flexneri, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhimurium, Bacillus subtilis, Escherichia coli, Vibrio cholera, Pseudomonas aeruginosa and Aeromonas liquefaciens bacterial strains. Among these bacterial strains, S. flexneri and B. subtilis are most sensitive to copper oxide nanoparticles than the positive control (Penicillin G) and S. typhimurium strain shows the less sensitive. Results show that sensitivity is highly dependent on the concentrations of CuO nanoflakes.

Microstructure and enhanced exciton-phonon coupling in Fe doped ZnO nanoparticles.

We report the microstructure and exciton-phonon coupling properties of Fe doped ZnO nanoparticles. Particles are prepared through sol-gel method at room temperature. Doping of Fe(3+) induces strain in the host lattice. Microstructural properties are analysed through Williamson-Hall analysis. Optical absorption studies show strong free excitonic absorption band at 369 nm. The photoluminescence (PL) studies reveal that ultraviolet, blue and green emission bands are located at 380, 445 and 500 nm respectively. Fe doped ZnO nanoparticles exhibits only ultraviolet and blue emission bands. Increase of Fe concentration makes green emission gradually disappeared. Gaussian fitted photoluminescence spectra show the emission is composed of free exciton (FX) recombination and its higher orders of longitudinal optical (LO) phonon replicas. Doping induced blue shift in FX peak and also increases the exciton-phonon coupling.

Room temperature synthesis and optical studies on Ag and Au mixed nanocomposite polyvinylpyrrolidone polymer films.

Optical properties of silver, gold and bimetallic (Au:Ag) nanocomposite polymer films which are prepared by chemical method have been reported. The experimental data was correlated with the theoretical calculations using Mie theory. We adopt small change in the theoretical calculations of bimetallic/mixed particle nanocomposite and the theory agrees well with the experimental data. Polyvinylpyrrolidone (PVP) was used as reducing and capping agent. Fourier transform infrared spectroscopy (FTIR) study reveals the presence of different functional groups, the possible mechanism that leads to the formation of nanoparticles by using PVP alone as reducing agent. Optical absorption spectra of Ag and Au nanocomposite polymers show a surface plasmon resonance (SPR) band around 430 and 532 nm, respectively. Thermal annealing effect on the prepared samples at 60 °C for different time durations result in shift of SPR band maximum and varies the full width at half maximum (FWHM). Absorption spectra of Au:Ag bimetallic films show bands at 412 and 547 nm confirms the presence of Ag and Au nanoparticles in the composite.