Single Step Solid State Synthesis of Carbon Nanoparticles for Instantaneous Detection of Fe (III) in Water Samples.

Though iron is one of the vital micronutrients in biological systems excess of which is associated with various illness. Consumption of contaminated water and crops because of its extensive industrial utility is one of the major sources for excess iron in living beings. Hence, we have designed a sensor based on carbon nanoparticles for the detection of Fe (III) and we have also attempted to estimate Fe (III) in spiked water samples. Carbon nanoparticles (CNP) with quantum yield of 40.2 % was synthesized by solid state synthesis from aromatic molecular precursors unlike conventional synthesis methodology. The particle size, stability and optical properties of CNP were investigated by microscopic and spectroscopic techniques. CNP manifested a naked color change from colorless to yellow in presence of Fe (III) and 72 % of CNP's emission was quenched at 487 nm on excitation at 377 nm by Fe (III). The detection time was less than a second and limit of detection was calculated as 0.248 µM. The mechanistic aspect of detection was investigated and applicability of CNP was examined in spiked water samples.

Reduced Graphene Oxide Supported Molybdenum Oxide Hybrid Nanocomposites: High Performance Electrode Material for Supercapacitor and Photocatalytic Applications.

Using a simple solution based synthesis route, hexagonal MoO3 (h-MoO3) nanorods on reduced graphene oxide (RGO) sheets were prepared. The structure and morphology of resulting RGO-MoO3 nanocomposite were characterized using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The optical property was studied using UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence spectroscopy (PL). The RGO-MoO3 nanocomposites were used as an electrode for supercapacitor application and photocatalyst for photodegradation of methylene blue (MB) and rhodamine B (RhB) under visible light irradiation. We demonstrated that the RGO-MoO3 electrode is capable of delivering high specific capacitance of 134 F/g at current density of 1 A/g with outstanding cyclic stability for 2000 cycles. The RGOMoO3 photocatalyst degrades 95% of MB dye within 90 min, and a considerable recyclability up to 4 cycles was observed. The quenching effect of scavengers test confirms holes are main reactive species in the photocatalytic degradation of MB. Further, the charge transfer process between RGO and MoO3 was schematically demonstrated.

Fabrication of RuO2-Ag3PO4 heterostructure nanocomposites: Investigations of band alignment on the enhanced visible light photocatalytic activity.

The RuO2-Ag3PO4 heterostructured nanocomposite was successfully synthesized by facile in situ deposition of porous ruthenium oxide (RuO2) nanoparticles on the surface of the silver phosphate (Ag3PO4). Under visible light irradiation, the 0.5wt.% RuO2-Ag3PO4 heterostructure photocatalyst exhibits enhanced photocatalytic efficiency compared to other composites of RuO2-Ag3PO4 and Ag3PO4. The optimized 0.5wt.% RuO2-Ag3PO4 nanocomposites exhibited 1.5 times enhanced photocatalytic activity towards the degradation of methylene blue (MB) than Ag3PO4. Moreover, the degradation rate of 0.5wt.% RuO2-Ag3PO4 nanocomposite towards the cationic dyes MB and rhodamine B (RhB) was nearly 6.6 times and 4.7 times higher than that towards the anionic dye methyl orange (MO). The formed heterojunction electric field of 310mV at the interface between RuO2 and Ag3PO4 heterostructure induces downward band bending of Ag3PO4. Also, this electric field increases the separation efficiency of electrons-holes resulting higher degradation efficiency. The quenching effect of scavengers test confirms that holes are reactive species and the RuO2-Ag3PO4 nanocomposite is highly stable, exhibited 88% of MB degradation after 4 recycles. The RuO2-Ag3PO4 nanocomposites inhibit self oxidation of Ag3PO4 resulting improved efficiency and stability.

Effect of Eu1+ and A13+ Concentrations on Photoluminescence of Gd2O3:Eu3+.

Gd2O3:Eu3+Al3+ phosphors are synthesized by wet chemical method and its photoluminescence properties are studied at different concentrations of Eu3+ and A13+. In emission spectra, the dominant peak observed at 611 nm corresponds to hypersensitive electric dipole transition in Eu3+. For Eu3+ concentration of 0.02, a good emission profile is observed and further its emission studies are carried out for the phosphor annealed at different temperatures and with the addition of A13+. The critical distance between the luminescent center is calculated to study the concentration quenching phenomenon. Enhancement of energy transfer occurs on introducing Al3+ in Gd2O3:Eu3+ phosphor. CIE coordinates are also calculated for Gd2O3:Eu3+ A13+ to estimate the color purity of the phosphor.

Investigation on structural, thermal, optical and sensing properties of meta-stable hexagonal MoO(3) nanocrystals of one dimensional structure.

Hexagonal molybdenum oxide (h-MoO(3)) was synthesized by a solution based chemical precipitation technique. Analysis by X-ray diffraction (XRD) confirmed that the as-synthesized powder had a metastable hexagonal structure. The characteristic vibrational band of Mo-O was identified from Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly depicted the morphology and size of h-MoO(3.) The morphology study showed that the product comprises one-dimensional (1D) hexagonal rods. From the electron energy loss spectroscopy (EELS) measurement, the elemental composition was investigated and confirmed from the characteristic peaks of molybdenum and oxygen. Thermogravimetric (TG) analysis on metastable MoO(3) revealed that the hexagonal phase was stable up to 430 °C and above this temperature complete transformation into a highly stable orthorhombic phase was achieved. The optical band gap energy was estimated from the Kubelka-Munk (K-M) function and was found to be 2.99 eV. Finally, the ethanol vapor-sensing behavior was investigated and the sensing response was found to vary linearly as a function of ethanol concentration in the parts per million (ppm) range.

Gas-sensing properties of needle-shaped Ni-doped SnO2 nanocrystals prepared by a simple sol-gel chemical precipitation method.

The preparation of needle-shaped SnO(2) nanocrystals doped with different concentration of nickel by a simple sol-gel chemical precipitation method is demonstrated. By varying the Ni-dopant concentration from 0 to 5 wt%, the phase purity and morphology of the SnO(2) nanocrystals are significantly changed. Powder XRD results reveal that the SnO(2) doped with a nickel concentration of up to 1 wt% shows a single crystalline tetragonal rutile phase, whereas a slight change in the crystallite structure is observed for samples with nickel above 1wt%. High resolution scanning electron microscopy (HRSEM) results reveal the change in morphology of the materials from spherical, for SnO(2), to very fine needle-like nanocrystals, for Ni-doped SnO(2), annealed at different temperatures. The gas sensing properties of the SnO(2) nanocrystals are significantly enhanced after the nickel doping.

Structural and optical characterization of samarium doped yttrium oxide nanoparticles.

Here we demonstrate the preparation of samarium doped yttrium oxide nanoparticles using samarium chloride as a samarium source by co-precipitation method. The samarium doped yttria nanoparticles are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Fourier transform infra-red spectroscopy (FT-IR). The XRD results revealed that all the synthesized samples exhibit cubic phase with average grain size of the nanoparticles in the order of 9-20 nm, calculated by Scherer's formula. The strain present in the annealed sample is estimated from Williamson-Hall (W-H) plot which is in the order of 3 x 10(-3). SEM and HRTEM results showed that the samples are composed of aggregated nanoparticles with uniform shape and size. The particles are highly crystalline which is also confirmed by XRD results. The position of the absorption peak is shifted towards the lower wavelength side when particles sizes reduced around 10 nm is observed by UV-visible (UV-vis) spectrometer. The direct band gap is estimated from UV-vis absorption spectrum, the calculated value is 5.98 and 5.87 eV for as-prepared and annealed sample (800 degrees C) respectively. The high intense red emission band observed at 608 nm from 4G(5/2)-6H(7/2) transition for Y2O3:Sm3+ under excitation at 214 nm using fluorescence spectrometer.

An investigation on co-precipitation derived ZnO nanospheres.

This paper describes a simple chemical co-precipitation method for preparing nano-sized zinc oxide (ZnO) nanospheres. The morphological, thermal, structural, and chemical features of ZnO nanospheres were systematically studied and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo gravimetric analysis-differential scanning calorimetric analysis, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. The SEM micrographs reveal that the particles are spherical in nature and the precipitating agent ammonia plays a critical role in controlling the morphology of the nanospheres. Crystalline ZnO phase is obtained at higher annealing temperature and there by reduce the contents of the hydrated species. Powder XRD pattern indicated that the nanospheres exhibit wurtzite hexagonal ZnO phase. The average crystallite sizes of the ZnO nanospheres were calculated to be 14 nm for as-prepared sample and 16 nm for 500 degrees C annealed sample. The peak broadening in ZnO nanospheres due to lattice deformation was analyzed by plotting various modified form of W-H analysis such as uniform deformation model, uniform stress deformation model, and uniform deformation energy density model. From the three models, the strain values epsilon and the crystallite size D(v) were estimated and tabulated. The growth and the formation of ZnO were predicted and the results were confirmed by FT-IR studies.

New analytical models to investigate thermal conductivity of nanofluids.

Nanofluids are identified suitable for micro and nano scale heat transfer applications where a high heat flux is required. These fluids are still in their early developmental stage and the exact heat transfer mechanism in them is not known yet. Due to this situation, there exists no suitable theoretical model for predicting the thermal conductivity of nanofluid. In this paper two new models for nanofluid thermal conductivity are developed. The first model which is based on Weber formula is used to predict the nanofluid thermal conductivity. The thermal conductivity of Al2O3/water, CuO/water, TiO2/water and TiO2/ethylene glycol nanofluids predicted by this model were compared with the published experimental data. The second model is used to analyze the influence of the effects of particle shape, nanolayer thickness and Brownian motion in enhancing thermal conductivity of nanofluids.

Monoclinic ß-MoO(3) nanosheets produced by atmospheric microplasma: application to lithium-ion batteries.

Porous high surface area thin films of nanosheet-shaped monoclinic MoO(3) were deposited onto platinized Si substrates using patch antenna-based atmospheric microplasma processing. The films were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and electrochemical analysis. The electrochemical analysis shows original redox peaks and high charge capacity, and also indicates a reversible electrochemical behaviour particularly beneficial for applications in Li-ion batteries. SEM shows that the films are highly porous and consist of nanosheets 50-100 nm thick with surface dimensions in the micrometre range. HRTEM reveals that the MoO(3) nanosheets consist of the monoclinic beta phase of MoO(3). These intricate nanoarchitectures made of monoclinic MoO(3) nanosheets have not been studied previously in the context of applications in Li-ion batteries and show superior structural and morphological features that enable effective insertion of Li ions.