Gujjarahalli Thimmanna Chandrappa

Synthesis of bismuth vanadate: its application in H2 evolution and sunlight-driven photodegradation

A nanocrystalline m-BiVO4 photocatalyst for H2 evolution, which works under UV-light irradiation, has been synthesized by a facile solution combustion synthesis method. Hydrogen evolution over BiVO4 is a significant result in the field of renewable energy sources and here we are the first to show hydrogen evolution experimentally with BiVO4 in the absence of either coupling oxides or doping metals. The yield of hydrogen generated is about 489 μmol per 2.5 h of reaction under UV irradiation. The ultra-light yellow crystalline combustion derived nanopowder exhibits porous morphology with a strong absorption in the visible light region. The estimated band gap of BiVO4 powder is about 2.52 eV. The powder shows highly visible photocatalytic activity towards methylene blue degradation under sun light irradiation. The H2 evolution and photocatalytic activity of BiVO4 nanocrystalline powder can be attributed to its physical properties such as nanosize particles and large surface area.

Hydrothermal synthesis of amorphous MoS2nanofiber bundles via acidification of ammonium heptamolybdate tetrahydrate

MoS2nanofiber bundles have been prepared by hydrothermal method using ammonium molybdate with sulfur source in acidic medium and maintained at 180 °C for several hours. The obtained black crystalline products are characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PXRD pattern of the sample can be readily indexed as hexagonal 2H-MoS2. FTIR spectrum of the MoS2shows the band at 480 cm−1corresponds to the γas(Mo-S). SEM/TEM images of the samples exhibit that the MoS2nanofiber exist in bundles of 120–300 nm in diameter and 20–25 μm in length. The effects of temperature, duration and other experimental parameters on the morphology of the products are investigated.

Morphological Evolution of (NH4)0.5V2O5·mH2O Fibers into Belts, Triangles, and Rings

In this contribution, single-crystalline (NH(4))(0.5)V(2)O(5)·mH(2)O xerogels made of belts, rings, triangles, and ovals have been synthesized using a surfactant-free hydrothermal method. The analytical techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the morphology, composition, and structure of the as-prepared products. On the basis of SEM and TEM observations, we suggested that the as-prepared (NH(4))(0.5)V(2)O(5)·mH(2)O rings, triangles, and ovals have been formed by connecting two ends of the vanadium oxide sheet made of edge and corner sharing VO(5) square pyramids. The as-prepared (NH(4))(0.5)V(2)O(5)·mH(2)O nanobelts are up to several hundreds of micrometers long, 402-551 nm wide, and 235-305 nm thick. The thickness and width of the rings are respectively ∼454 nm and ∼1 μm. Triangles with three unequal sides having a thickness of ∼143 nm and a width of ∼1 μm were also formed. The crystalline orthorhombic phase of shcherbianite V(2)O(5) was obtained on calcination of (NH(4))(0.5)V(2)O(5)·mH(2)O at 350 °C for 2 h. The SEM image of this V(2)O(5) product retains the parent morphology of the preheated compound. A possible reaction mechanism and the growth process involved in the formation of belts/rings/triangles and ovallike microstructures are discussed.

Effect of fuel on the formation structure, transport and magnetic properties of LaMnO3+nanopowders

Single-step low-temperature solution combustion (LCS) synthesis was adopted for the preparation of LaMnO3+ δ (LM) nanopowders. The powders were well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface area and Fourier transform infrared spectroscopy (FTIR). The PXRD of as-formed LM showed a cubic phase but, upon calcination (900°C, 6 h), it transformed into a rhombohedral phase. The effect of fuel on the formation of LM was examined, and its structure and magnetoresistance properties were investigated. Magnetoresistance (MR) measurements on LM were carried out at 0, 1, 4 and 7 T between 300 and 10 K. LM (fuel-to-oxidizer ratio; ψ = 1) showed an MR of 17% at 1 T, whereas, for 4 and 7 T, it exhibited an MR of 45 and 55%, respectively, near the T M-I. Metallic resistivity data below T M-I showed that the double exchange interaction played a major role in this compound. It was interesting to observe that the sample calcined at 1200°C for 3 h exhibited insulator behavior.

Synthesis and characterisation of microstructural α-Mn2O3 materials

Low-dimensional α-Mn2O3 materials with novel surface morphologies have been prepared by thermal decomposition of hydrothermal-derived MnCO3. The powder X-ray diffraction pattern reveals that the Mn2O3 microstructures are of cubic phase structure. From Fourier transform infrared spectroscopy results, the peaks around 600–450 cm−1 correspond to Mn–O bending vibrations. From the TGA results, the observed major weight loss ∼31% between 350 and 540°C is due to the decomposition of MnCO3 into Mn2O3. The X-ray photoelectron spectroscopy results showed that Mn is in +3 oxidation state. The peaks at 641.2 and 652.73 eV are assigned to the Mn2p3/2 and Mn2p1/2 of Mn+3 states, respectively. The scanning electron microscope images showed that the α-Mn2O3 products exhibit spheres, dumbbell- and peanut-shaped microstructure. These microstructures are mainly composed of wires/rods and particles. The scanning electron microscope results also revealed that the obtained α-Mn2O3 maintains the frame structure of the precursor MnCO3.

Formation of crystalline Na2V6O16·3H2O ribbons into belts and rings.

Single-crystalline nanobelts and nanorings of Na(2)V(6)O(16)·3H(2)O structures have been facilely synthesized through a direct hydrothermal reaction between NaVO(3) and H(3)PO(4), without the addition of any harmful solvents or surfactants. The analytical techniques of scanning electron microscopy, transmission electron microscopy (TEM), powder X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared, high-resolution TEM, and selected-area electron diffraction have been used to characterize the morphology, composition, and structure of the synthesized products. The Na(2)V(6)O(16)·3H(2)O nanobelts are up to several hundreds of micrometers in length and 100-300 nm in thickness, and for nanorings, the diameters are 4.5-6.5 μm. H(3)PO(4) plays a key role in maintaining the pH of the solution as well as producing PO(4)(3-) ions in solution. The chemical reactions and a possible growth mechanism involved in the formation of Na(2)V(6)O(16)·3H(2)O nanobelts and nanorings are briefly discussed.

Synthesis and Characterization of Mo‐Oxide Nanoribbons

Mixed valence Mo‐oxide nanoribbons have been synthesized using MoO3 as precursor and hexadecylamine (HDA) as surfactant under hydrothermal condition at 180°C for 1 to 10 d. The morphology of the product is found to depend strongly on the duration of hydrothermal treatment, temperature and HDA/Mo ratio. The powder diffraction patterns of pre‐and post‐hydrothermally treated materials exhibit the highly intense and sharp reflections at low scattering angles that are typical for layered structures. The IR spectrum of Mo‐HDA composite is quite similar to hydrothermal treated samples except shifting of few bands to higher energy side. The weight change in TG‐DTA curves indicates the presence of HDA as intercalates. The SEM images of samples reveal the layered and flat nanoribbons formation. Dimensions of these flat nanoribbons found from SEM images are about 160 nm in thickness, 430–620 nm in width and several micrometers in length. The high resolution TEM images of Mo‐oxide nanoribbons corroborate the XRD results and the fringe spacing paralleling to the nanolayers is estimated to be 3.52 nm, which is close to the (001) lattice spacing of lamellar Mo‐oxide nanoribbons.

Surfactant Assisted Hydrothermal Synthesis of CdSe Nanostructural Materials

CdSe/CTAB composite nanostructural materials were successfully synthesized at 160–200 °C for 2 days through a facile surfactant (cetyl trimethyl ammonium bromide-CTAB) assisted hydrothermal method using cadmium acetate and sodium selenate as precursor. The obtained products were characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and thermo gravimetric analysis. Optical properties were studied by photoluminescence and UV-visible spectroscopy and morphology was investigated by scanning electron microscopy.

Synthesis, characterization and applications of nanostructural/nanodimensional metal oxides

Molybdenum oxide nanorods (MOx-NR) and vanadium oxide nanotubes (VOx-NT) have been prepared using MoO3 and V2O5 powders as precursors and hexadecylamine as surfactant via hydrothermal route. Porous nanocrystalline MgO powder has been prepared by a simple and instantaneous solution combustion process using corresponding magnesium nitrate as oxidizer and glycine as fuel. The compounds are characterized by XRD, TG-DTA, SEM, TEM, surface area and porosity measurements. Because of the porous nature having large surface area (107 m2/g) with nanodimension (12-23 nm), MgO powder has been successfully employed as defluoridizing agent for the removal of fluoride (75%) in ground water

Combustion-derived CuO nanoparticles: An effective and environmentally benign catalyst in the synthesis of aromatic nitriles from aromatic aldehydes

Abstract CuO nanoparticles were synthesized using an energy–efficient and rapid solution combustion technique with malic acid employed as a fuel. The combustion–derived CuO nanoparticles were used as catalysts in a one–pot synthesis of aromatic nitriles from aromatic aldehydes and hydroxylamine hydrochloride. The catalyst was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analysis. The catalytic activity of the CuO nanoparticles in the synthesis of aromatic nitriles from aromatic aldehydes was evaluated. The present protocol offers the advantages of a clean reaction, simple methodology, short reaction duration (1–2 min), and high yield (85%–98%). The catalytic activity of the CuO nanoparticles was found to be higher than that of bulk CuO powder under the same conditions. The catalyst can also be recovered and reused up to four times with no significant loss of catalytic activity. The present approach is inexpensive and is a convenient technique suitable for industrial production of CuO nanoparticles and nitriles.