Enhanced visible light-driven photocatalytic performance of CdSe nanorods.

Cadmium selenide (CdSe) semiconductor nanorods are prepared in hydrothermal process using hydrazine hydrate (N2H4.H2O) and ammonia (NH3.H2O) as reducing agents. The reaction time is increased to 7 h and the amount of hydrazine hydrate used is also increased to 15 mL which have resulted in diminished stacking faults in the CdSe nanorods prepared. The crystal structure, morphological variations, and size of the prepared CdSe nanorods are examined by XRD analysis. The crystalline size of the CdSe nanorods is 20-30 nm in diameter. HRTEM images reveal the formation of high order CdSe nanorods of the length about 25-40 nm. The bandgap in the CdSe nanoparticles is determined to be 2.17 eV. The peak at 595 nm in photoluminescence (PL) spectrum indicates oxygen vacancy defects in the prepared CdSe sample. The variation of dielectric properties with respect to temperature and frequency of pelletized CdSe is studied. High photocatalytic efficiency (98%) of catalyst/H2O2 is also achieved for decomposition of Rhodamine-B dye.

Synthesis of titanium oxide nanoparticles using Aloe barbadensis mill and evaluation of its antibiofilm potential against Pseudomonas aeruginosa PAO1.

Titanium dioxide nanoparticles (TiO2-NPs) were synthesized using the aqueous leaf extract of Aloe barbadensis as a reducing and fabricating agent. The biosynthesis of the TiO2-NPs was initially confirmed by UV-vis spectroscopy. Based on the HRTEM and FESEM analysis, the biosynthesized NPs were found to be polydispersed and predominantly spherical in shape, with an average size of ~20 nm. A sharp and strong characteristic peaks of titanium (Ti) and oxygen (O) observed in the EDS pattern confirmed the synthesis of the TiO2-NPs. The FTIR spectroscopy suggested the presence of terpenoids, flavonoids and proteins which might be responsible for the biosynthesis and fabrication of the TiO2-NPs. The crystalline nature of the synthesized TiO2-NPs constituting of a mixture of brookite, anatase, and rutile phases was indicated by the XRD pattern. The spectral window around 180-1000 cm-1 covered the high-frequency Raman spectra of the TiO2-NPs. The Raman vibrational spectrum showed four Eg modes centered at 197.84, 399.24, 514.50, and 641.58 cm-1 representing the anatase phase of TiO2-NPs. The strongest and broadened peak of anatase was observed at the frequency of 641.58 cm-1. The metabolic activity of P. aeruginosa exposed to the MIC of TiO2-NPs was measured based on the reduction of tetrazolium salt by the dehydrogenase enzyme, produced by the metabolically active bacterial cells. The reduction in TTC was evident from the appearance of a red colored formazan in the solution. A noticeable suppression in the cell viability by 30.76 ±â€¯3.96% of P. aeruginosa in the biofilm mode was found in presence of TiO2-NPs. Furthermore, the Minimum Inhibitory Concentration (MIC) of TiO2-NPs exhibited profound antibiofilm activity against P. aeruginosa by effectively preventing the adherence of the planktonic cells to the substratum. Thus, these NPs may be employed in controlling bacterial infections associated with biofilm.

Up-Scalable Synthesis of Size-Controlled White-Green Emitting Behavior of Core/Shell (CdSe/ZnS) Quantum Dots for LED Applications.

Research on CdSe/ZnS core-shell quantum dots (QDs) was synthesized by a chemical route using bio-conjugated organic amino acid (L-Cysteine). The structural, morphological, and optical properties of the nanocrystal powder samples were analyzed using various characterization techniques. The diameter of the resulting QDs was about 3 nm with uniform size distribution. The optical properties QDs exhibited an absorption and emission peak at 515 and 525 nm respectively, at room temperature. The QDs through emission in the spectral range at 516-535 nm is special for their application in green LEDs and white-light generation. The high optical properties performance of the QDs nanocomposites gained indicates that the materials are promising for (LED) applications.

Photocatalytic Activity and Humidity Sensor Studies of Magnetically Reusable FeWO4-WO3 Composite Nanoparticles.

Different mole ratios of (8:2, 6:4, 4:6 and 2:8) iron tungstate-tungsten trioxide (FeWO4-WO3) composite nanoparticles were synthesized by solid state method. The synthesized composite nanoparticles were characterized by powder X-ray diffraction analysis (XRD), field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. The crystalline nature and particle size of the samples were characterized by powder X-ray diffraction analysis (XRD). The morphology was confirmed by field-emission scanning electron microscopy (FE-SEM) analysis and transmission electron microscope (TEM). The energy dispersive X-ray spectroscopy (EDX) proved the purity of nanocomposites. Vibrating sample magnetometer reveals that the sample shows paramagnetic property based on the metal present in the prepared nanocomposites at room temperature. The magnetic property is due to the structural defects rather than the impurity phase. Magnetization saturation value (Ms = 398.7 emu/g) of FWWO-46 composite nanoparticles is high enough to be magnetically removed by applying a magnetic field. The composites were subjected to DC conductance measurement as a function of relative humidity in the range of 5-98%, achieved by different water vapour buffers thermostated at room temperature. The sensitivity factor, Sf (R5%/R98%) measured at 25 °C revealed that FWWO-46 shows the highest humidity sensitivity factor Sf = 3956, with a response and recovery time of 45 s and 100 s respectively. Photocatalytic degradation of methylene blue (MB) from aqueous solution has been carried out using FeWO4-WO3 composite nanoparticles as photocatalyst under Ultraviolet radiation.

Antioxidant and Photocatalytic Activity of Aqueous Leaf Extract Mediated Green Synthesis of Silver Nanoparticles Using Passiflora edulis f. flavicarpa.

The purpose of this study is to minimize the negative impacts of synthetic procedures and to develop environmentally benign procedures for the synthesis of metallic nanoparticles. In the present study, Passiflora edulis f. flavicarpa (P. edulis) aqueous leaf extract mediated green synthesis of silver nanoparticles are described. The synthesized silver nanoparticles were characterized by UV-Vis Spectroscopy, Fluorescence Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV). The silver nanoparticles (AgNPs) showed antibacterial activities against both gram positive (staphylococcus) and gram negative (Escherichia coli) bacteria. The efficacy of the synthesized silver nanoparticles (AgNPs) was demonstrated as catalyst in the photocatalytic degradation of Methyl Orange (MO) and Methylene Blue (MB) dyes which were measured spectrophotometrically. The study revealed that biosynthesized silver nanoparticles using Passiflora. edulis f. flavicarpa, plant extract was found to be very effective as antioxidant agent.

Direct Electrodeposition of Gold Nanoparticles on Glassy Carbon Electrode for Selective Determination Catechol in the Presence of Hydroquinone.

A simple and reliable voltammetric sensor for simultaneous determination of Catechol (CT) and Hydroquinone (HQ) was developed by electrodepositing the gold nanoparticles on the surface of the Glassy Carbon Electrode (GCE). The cyclic voltammograms in a mixed solution of CT and HQ have shown that the oxidation peaks become well resolved and were separated by 110 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both CT and HQ were remarkably increased three times in comparison with the bare GCE. This makes gold nanoparticles deposited GCE a suitable candidate for the determination of these isomers. In the presence of 1 mM HQ isomer, the oxidation peak currents of differential pulse voltammograms are proportional to the concentration of CT in the range of 21 µM to 323 µM with limit of detection 3.0 µM (S/N = 3). The proposed sensor has some important advantages such as low cost, ease of preparation, good stability and high reproducibility.

Structural, Optical, Morphological and Microbial Studies on SnO2 Nanoparticles Prepared by Co-Precipitation Method.

Nanoparticles of tin oxide (SnO2) powders were prepared by co-precipitation method at 500 °C, 700 °C and 900 °C temperature. The sintered SnO2 nanoparticles, structural, optical, magnetic, morphological properties and microbial activity have been studied. XRD studies reveals that sintered powder which exhibits tetragonal crystal structure and both crystallinity as well as crystal size increase with increase in temperature. The morphological studies reveal randomly arranged grains with compact nature grain size increases with sintering temperature. The compositional analyses of SnO2 nanoparticles have been studied using X-ray photoelectron spectroscopy analysis. The optical band gap values of SnO2 nanoparticles were calculated to be about 4.3 eV in the temperature 500 °C, comparing with that of the bulk SnO2 3.78 eV, by optical absorption measurement. Room temperature M-H curve for pure SnO2 nanoparticles exhibits ferromagnetic behaviour. The tin oxide nanoparticles are acted as potential candidate material for bacterial and fungal activity.

Optical, Magnetic and Photocatalytic Activity Studies of Li, Mg and Sr Doped and Undoped Zinc Oxide Nanoparticles.

Nanoparticles of Li, Mg and Sr doped and undoped zinc oxide was prepared by simple precipitation method. The structural, optical, and magnetic properties of the samples were investigated by the Powder X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared (FTIR) spectroscopy, Ultra-violet Visible spectroscopy (UV-vis) spectra, Photoluminescence (PL) and Vibrational Sample Magnetometer (VSM). The Powder X-ray diffraction data confirm the formation of hexagonal wurtzite structure of all doped and undoped ZnO. The SEM photograph reveals that the pores availability and particles size in the range of 10 nm-50 nm. FTIR and UV-Visible spectra results confirm the incorporation of the dopant into the ZnO lattice nanostructure. The UV-Visible spectra indicate that the shift of blue region (lower wavelength) due to bandgap widening. Photoluminescence intensity varies with doping due to the increase of oxygen vacancies in prepared ZnO. The pure ZnO exist paramagnetic while doped (Li, Mg and Sr) ZnO exist ferromagnetic property. The photocatalytic activity of the prepared sample also carried out in detail.

Photocatalytic activity of binary metal oxide nanocomposites of CeO2/CdO nanospheres: Investigation of optical and antimicrobial activity.

We report the synthesis of high quality CeO2-CdO binary metal oxide nanocomposites were synthesized by a simple chemical precipitation and hydrothermal method. Cerium nitrate and cadmium nitrate were used as precursors. Composition, structure and morphology of the nanocomposites were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD pattern proves that the final product has cubic phase and the particle size diameter of the nanocomposites are 27nm, XRD results also indicated that the crystalline properties of the nanocomposite were improved without affecting the parent lattice, FESEM analysis indicates that the product is composed of spherical particles in clusters. The morphological and optical properties of CeO2-CdO nanosamples were characterized by HRTEM and DRS spectroscopy. The IR results showed high purity of products and indicated that the nanocomposites are made up of CeO2 and CdO bonds. Absorption spectra exhibited an upward shift in characteristic peaks caused by the addition of transition metal oxide, suggesting that crystallinity of both the metal oxide is improved due to specific doping level. TGA plots further confirmed the purity and stability of nanomaterials prepared. Hence the nanocomposite has cubic crystal lattice and form a homogeneous solid structure. From the result, Cd(2+) ions are embedded in the cubic crystal lattice of ceria. The growth rate increases which are ascribed to the cationic doping with a lower valence cation. Ce-Cd binary metal oxide nanocomposites showed antibacterial activity, it showed the better growth inhibition towards p.aeruginosa. Exploit of photodegradation and photocatalytic activity of large scale synthesis of CeO2-CdO binary metal oxide nanocomposites was reported.

Synthesis and characterization studies of MgO:CuO nanocrystals by wet-chemical method.

In this report, we examine the progress in adapting these nanomaterials for several predominantly photonics device fabrication by wet-chemical method. Nanocomposite of magnesium oxide (MgO) with copper oxide (CuO) doped nanoparticles were characterized by X-ray powder diffraction (XRD) and the observed peaks are quite agreeable with the pure phase cubic structure. High-resolution transmission electron microscopic (HR-TEM) results reveal that the resultant nanopowders are porous and agglomerated with polycrystalline nano-entities. Field emission of selected-area electron diffraction (SAED) studies showed that the average size of the nanoparticles were 20nm. Photoluminescence spectra of MgO:CuO were investigated, showing emission peaks around 375nm relating to new energy levels induced by defects or defect levels generation and confocal micro-Raman images indicated that the chemical molecular vibrational band structure and morphology of the product which is spherical shaped nanoparticles with an average particle size of ∼25nm with standard deviation. The electrochemical response of MgO:CuO which is proves that the nano-copper/magnesium has high functionality due to the small size and it has higher electrochemical activity without any modifications.