Papers by Chandragiri Venkata Reddy
Electronic Materials Letters, 2016
S as precursors. The structural features of obtained materials were characterized by X-ray diffra... more S as precursors. The structural features of obtained materials were characterized by X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), thermal analysis (TG-DTA), N2 adsorption-desorption, and photoluminescence (PL). The influence on the photocatalytic activity of the MoS2 cocatalyst concentration with ZrO2 nanoparticles was studied. The MZr-2 hybrid sample had the highest photocatalytic activity for the degradation of methyl orange (MO), which was 8.45 times higher than that of pristine ZrO2 ascribed to high specific surface area and absorbance efficiency. Recycling experiments revealed that the reusability of the MZr-2 hybrid was due to the low photocorrosive effect and good catalytic stability. PL spectra confirmed the electronic interaction between ZrO2 and MoS2. The photoinduced electrons could be easily transferred from CB of ZrO2 to the MoS2 cocatalyst, which facilitate effective charge separation and enhanced the photocatalytic degradation in the UV region. A photocatalytic mechanism is proposed. It is believed that the ZrO2/MoS2 hybrid structure has promise as a photocatalyst with low cost and high efficiency for photoreactions.
Physica Scripta, 2012
ZnCdO nanocrystalline powder is synthesized by the simple solution method at room temperature. Sy... more ZnCdO nanocrystalline powder is synthesized by the simple solution method at room temperature. Synthesized powder was characterized by powder x-ray diffraction (XRD), scanning electron microscope with x-ray spectrometry (EDX), thermo gravimetry–differential thermal analysis (TG–DTA) and other spectroscopic techniques. The XRD pattern exhibited a mixture of hexagonal ZnO and cubic cadmium oxide phases. The crystallite size of the prepared powder was
Journal of Materials Science: Materials in Electronics, 2018
SnO 2-NiO p-n heterojunction nanocomposite was prepared by a solution combustion synthesis method... more SnO 2-NiO p-n heterojunction nanocomposite was prepared by a solution combustion synthesis method for the reduction of water pollution. The systematic investigation has been carried out by varying the content of Ni precursor. Structural and optical properties were characterized by X-ray diffraction, HR-TEM, XPS, UV-Vis, and FT-IR spectroscopies, respectively. The as-synthesized nanocomposites exhibited good crystallinity with phases belongs to SnO 2 and NiO. In case of nanocomposites, the reduced band gap was observed when compared to that of pure SnO 2. The photocatalytic performance was done for all samples in the presence of UV-Visible light. The SnO 2-NiO p-n heterojunction sample (SN3) shows 82% RhB dye degradation within 2 h. The enhanced photocatalytic efficiency is mainly due to the formation of the p-n junction. The possible photocatalytic mechanism was proposed for the degradation of RhB under UV-Visible light irradiation.
Ceramics International, 2018
Synthesis and structural, optical, photocatalytic, and electrochemical properties of undoped and ... more Synthesis and structural, optical, photocatalytic, and electrochemical properties of undoped and yttrium-doped tetragonal ZrO 2 nanoparticles, Ceramics International,
Applied Physics A, 2017
CdO, ZnS, and CdO/ZnS hybrid photocatalyst were prepared using a simple co-precipitation method, ... more CdO, ZnS, and CdO/ZnS hybrid photocatalyst were prepared using a simple co-precipitation method, and its photocatalytical activity was studied. The materials were characterized using powder XRD, TEM, HRTEM, BET, Raman, optical absorption, FT-IR, Thermal analysis and PL. The XRD patterns confirmed the crystal structure of the prepared samples. The surface analysis shows that the CdO/ZnS hybrid photocatalyst have larger surface area than the CdO and ZnS. Optical analysis of the nanocomposites revealed that the bond energy decreased after adding ZnS nanoparticles due to interactions with CdO nanoparticles. Raman spectroscopy showed the phonon modes of the CdO and ZnS, and PL spectra showed the electronic interaction between them. The photo-induced electrons can be easily transferred from the CdO to the ZnS in the composite, which facilitates effective charge separation and enhances photocatalytic degradation. The highest photocatalytic activity was achieved using the CdO/ZnS hybrid photocatalyst, with which more than 92% degradation was achieved. The enhanced photocatalytic activity could be ascribed to the low recombination rate of the electron and hole pairs because of the interface action between the CdO and ZnS.
Materials Science in Semiconductor Processing, 2017
The effects of Al and Ti seed layers were studied for undoped and Fe-doped ZnO thin films deposit... more The effects of Al and Ti seed layers were studied for undoped and Fe-doped ZnO thin films deposited on n-type Si substrates by electron beam (e-beam) evaporation. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The films grown on seed layers showed wurtzite hexagonal crystal nanorod and nanowire structures. A higher angle phase shift was observed in the doped thin films compared to the pristine ZnO films. Microstructural studies confirmed the growth of nanorods and nanowires with average widths of~32 nm and~8-29 nm, respectively. The nanostructures were denser and more crystalline on the Al seed layer than on the Ti seed layer for the doped thin films. However, in the undoped thin films, a more crystalline nature was observed on the Ti seeded layer than the Al seeded layer.
Journal of Molecular Structure, 2013
h i g h l i g h t s Mn 2+ doped Zn 3 (BO 3) 2 nanopowder prepared by co-precipitation method. EPR... more h i g h l i g h t s Mn 2+ doped Zn 3 (BO 3) 2 nanopowder prepared by co-precipitation method. EPR spectrum showed resonance signal at g = 2.0032, which is indicate the Mn 2+ in octahedral symmetry. PL spectrum shows emission band in UV region. From optical absorption spectrum crystal field (Dq) and inter-electronic (B and C) parameters are evaluated. The bonding between Mn 2+ ions and its ligands is in ionic nature.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011
Optical and physical properties of Ni 2+ doped 20ZnO + xLi 2 O + (30 − x)Na 2 O + 50B 2 O 3 (5 ≤ ... more Optical and physical properties of Ni 2+ doped 20ZnO + xLi 2 O + (30 − x)Na 2 O + 50B 2 O 3 (5 ≤ x ≤ 25) glasses are carried out at room temperature. Powder XRD pattern of all the glass samples confirms the amorphous nature. Several physical parameters are evaluated for all the glasses with respect to the composition. The optical absorption spectra confirm the site symmetry of the Ni 2+ doped glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. It is interesting to observe that the optical band gap and Urbach energies exhibit the mixed alkali effect. The FT-IR spectral investigations of Ni 2+ doped glasses exhibit characteristic vibrations of BO 3 and BO 4 units.
Physica Scripta, 2011
A Cu2+ doped beta-barium borate nanopowder has been synthesized using the co-precipitation method... more A Cu2+ doped beta-barium borate nanopowder has been synthesized using the co-precipitation method. The average crystallite size of the present system is evaluated at 68 nm and the lattice cell parameters are calculated from x-ray diffraction data. Optical absorption spectral data reveal that the Cu2+ ions are in a tetragonally distorted octahedral site in the host lattice. Direct, indirect and
Materials Research Bulletin, 2011
Mixed alkali borate glasses are considered as an important class of materials in microelectronics... more Mixed alkali borate glasses are considered as an important class of materials in microelectronics, optics and optical fibers due to their excellent thermal, optical and electrical properties [1-3]. When one alkali ion is replaced by another alkali ion, keeping the total alkali content constant, these oxide glasses show non-linear behavior which causes mixed alkali effect (MAE). This non-linear behavior occurs in the system based on dynamic studies which are associated with the properties of alkali ion movement such as electrical conductivity, ionic diffusion, dielectric relaxation and internal friction [4]. The non-linearity arises depending on the static structure and alkali non-bridging oxygen of the system [5]. Recently the MAE in alkali zinc borate glasses has been reported using spectroscopic techniques [6-8]. The structure of pure vitreous B 2 O 3 consists of a random network of boroxol rings and BO 3 triangles connected by B-O-B linkage [9]. The addition of alkali oxides modifies the boroxol rings; complex borate groups with one or two four coordinate borate atoms are formed [10]. ZnO enters in the glass structure in the form of both network former and network modifier. MnO 2 , as a paramagnetic probe, has wide range of applications in various industrial sectors in making zinc-carbon batteries, ceramics, glasses, etc. The glass network containing interstices of varying diameters such as alkali ions of different sizes are more easily accommodated in the sites. As the ionic radius of Li is smaller than the ions in the network, it easily enters into the glass network interstitially forming a new environment. This leads to changes in the structure of studied glass samples. Hence all its related properties may change accordingly with the concentration of Li 2 O content. The aim of the present investigations is to examine the mixed alkali effect on physical and structural properties of a new quaternary system, Mn 2+ doped 20ZnO + xLi 2 O + (30Àx)Na 2 O + 50B 2 O 3 (5 x 25) glasses, using spectroscopic techniques. 2. Experimental 2.1. Preparation 0.1 mol% of Mn 2+ doped mixed alkali zinc borate glasses are prepared using Analar grade chemicals of ZnO, Li 2 CO 3 , Na 2 CO 3 , B 2 O 3 and MnO 2 as starting materials with 99.9% of purity. These mixtures are sintered at 750 K and melted in an electric furnace in a silica crucible around 1250 K for nearly 1 h. The melt is then quenched at room temperature in air to form a glass. The glasses so formed are further annealed at 700 K for 1 h to relieve the structural stress. The glass composition 19.9ZnO + xLi 2 O + (30Àx)x)Na 2 O + 50B 2 O 3 + 0.1MnO 2 (5 x 25), hereafter named as ZLNB
Journal of Non-Crystalline Solids, 2011
The physical and structural properties of Co 2+ doped 20ZnO + xLi 2 O + (30 − x)Na 2 O + 50B 2 O ... more The physical and structural properties of Co 2+ doped 20ZnO + xLi 2 O + (30 − x)Na 2 O + 50B 2 O 3 (5 ≤ × ≤ 25) (ZLNB) glasses have been studied and correlated. The physical and structural parameters of all the glasses are evaluated and a non-linear behavior is observed. No sharp peaks are observed in XRD patterns of the glass samples which confirm the amorphous nature. FT-IR spectra of ZLNB glasses reveal diborate units in borate network. The optical absorption spectra suggest the site symmetry of Co 2+ in the glasses is near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. The optical band gap and Urbach energies exhibit the mixed alkali effect. All the samples are found to be strong and stable in structure with low values of Urbach energy which lie between 0.027 eV and 0.039 eV. The correlation between densities and Urbach energies of Co 2+ doped ZLNB glasses with respect to Li 2 O content suggest a changeover conduction mechanism from electronic to ionic, with a diffusivity crossover point at x = 15 mol%.
Journal of Molecular Structure, 2013
h i g h l i g h t s " Cu 2+ ion doped ZnCdO nanopowder is prepared by simple solution method. " P... more h i g h l i g h t s " Cu 2+ ion doped ZnCdO nanopowder is prepared by simple solution method. " Powder XRD pattern conforms the prepared powder is in the nanoscale. " Site symmetry for copper ion is tetragonal distorted octahedral site symmetry.
Ceramics International, 2019
doped ZrO 2 nanoparticles prepared by a template-free method for electrochemical energy storage a... more doped ZrO 2 nanoparticles prepared by a template-free method for electrochemical energy storage and abatement of dye degradation,
Cu(II) ion-doped NaCaAlPO 4 F 3 phosphor has been synthesized using a solid state reaction method... more Cu(II) ion-doped NaCaAlPO 4 F 3 phosphor has been synthesized using a solid state reaction method. The prepared sample is characterized by powder X-ray diffraction, scanning electron microscope, optical absorption, electron paramagnetic resonance photoluminescence and Fourier transform infrared spectroscopy techniques. The crystallite size evaluated from x-ray diffraction data is in nanometers. Scanning electron microscopy micrographs showed the presence of several irregular shaped particles. From optical absorption and electron paramagnetic resonance spectral data the doped Cu(II) ions are ascribed to distorted octahedral site symmetry. The synthesized phosphor exhibits emission bands in ultraviolet , blue and green regions under the excitation wavelength of 335 nm. The CIE chromaticity coordinates (x = 0.159, y = 0.204) also calculated for the prepared sample from the emission spectrum. The Fourier transform infrared spectroscopy spectrum revealed the characteristic vibrational bands of the prepared phosphor material.
Cobalt Cadmium Ferrite, COo.5Cdo.5Fe204 nanoferrite powder with the suitable stoichiometric ratio... more Cobalt Cadmium Ferrite, COo.5Cdo.5Fe204 nanoferrite powder with the suitable stoichiometric ratio was prepared by using co-precipitation method. As prepared sample was characterized by using powder X-ray diffraction (XRD), Scanning Electron Microscope with EDX and Vibrating sample magnetometer (VSM). At room temperature the specific saturation magnetization (Ms) of the prepared material was measured. From the powder XRD data, the average crystallite size was calculated. SEM images showed the surface morphology of prepared nanoferrite sample along with chemical mapping.
Cr 3+ doped β-BaB 2 O 4 nanopowder has been prepared by using co-precipitation method and their s... more Cr 3+ doped β-BaB 2 O 4 nanopowder has been prepared by using co-precipitation method and their spectral properties are studied by various spectroscopic techniques like Powder XRD, EPR, Optical, FT-IR and Photo Luminescence. Powder X-ray diffraction data reveals that the crystal structure belongs to monoclinic and the average crystallite size is evaluated. SEM images showed the surface morphology. Crystal field (Dq), and inter electronic repulsion (B&C) parameters are evaluated from the optical absorption data. From EPR and optical absorption investigations the site symmetry of Cr 3+ ion in the prepared sample is ascribed to a distorted octahedron. The CIE chromaticity coordinates are calculated from the emission spectrum as x ¼ 0.179 and y¼ 0.174. FT-IR spectrum shows the characteristic vibrational bands related to β-BaB 2 O 4 .
Cr 3+ doped β-BaB 2 O 4 nanopowder has been prepared by using co-precipitation method and their s... more Cr 3+ doped β-BaB 2 O 4 nanopowder has been prepared by using co-precipitation method and their spectral properties are studied by various spectroscopic techniques like Powder XRD, EPR, Optical, FT-IR and Photo Luminescence. Powder X-ray diffraction data reveals that the crystal structure belongs to monoclinic and the average crystallite size is evaluated. SEM images showed the surface morphology. Crystal field (Dq), and inter electronic repulsion (B&C) parameters are evaluated from the optical absorption data. From EPR and optical absorption investigations the site symmetry of Cr 3+ ion in the prepared sample is ascribed to a distorted octahedron. The CIE chromaticity coordinates are calculated from the emission spectrum as x ¼ 0.179 and y¼ 0.174. FT-IR spectrum shows the characteristic vibrational bands related to β-BaB 2 O 4 .
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights Mn 2+ doped Zn 3 (BO 3) 2 nanopowder prepared by co-precipitation method. EPR spectrum showed resonance signal at g = 2.0032, which is indicate the Mn 2+ in octahedral symmetry. PL spectrum shows emission band in UV region. From optical absorption spectrum crystal field (Dq) and inter-electronic (B and C) parameters are evaluated. The bonding between Mn 2+ ions and its ligands is in ionic nature. a b s t r a c t Mn 2+ doped Zn 3 (BO 3) 2 nanopowder has been prepared by simple chemical solution method and characterized by powder XRD, SEM with EDS and several spectroscopic techniques. From powder XRD pattern, the crystal structure belongs to monoclinic and the average crystallite size is evaluated. SEM images showed the surface morphology of as prepared samples. Optical absorption spectrum exhibited the characteristic bands of Mn 2+ ions in octahedral site symmetry. EPR spectrum showed resonance signal around g = 2.0 and from this bonding nature between the doped Mn 2+ ions and its ligands is also determined. Room temperature Photoluminescence spectrum showed UV emission band around 302 under the pho-ton excitation wavelength of 263 nm. FT-IR spectrum shows the characteristic vibration bands of metal oxide and borate molecules.
" Co 2+ doped ZnO nanopowder was synthesized by solid state reaction method. " Covalent bonding e... more " Co 2+ doped ZnO nanopowder was synthesized by solid state reaction method. " Covalent bonding exists between the doped metal ions and its ligands. " UV and blue emission bands are observed in PL spectrum. " Presence of ZnAO vibrations are confirmed from FT-IR spectrum. g r a p h i c a l a b s t r a c t The photoluminescence spectra of Co 2+ doped ZnO nanopowder is recorded at room temperature under the photon excitation of 285 nm. Three bands are observed. At first, a strong ultra violet (UV) near band edge (NBE) emission centered at 386 nm, second, a weak blue emission band centered at 468 nm. The strong UV band is assigned to the occurrence of free excitons recombination through an exciton–exciton collision process. The CIE chromaticity coordinates are also calculated from the emission spectrum (shown in Fig. 5) x = 0.136, y = 0.068. Compared with the NTSC standard CIE chromaticity coordinate values for blue (x = 0.14, y = 0.07) it is found that the CIE chromaticity coordinates of ZnO: Co 2+ is close to the NTSC standard values. This material can be used as LEDs and lamps. a b s t r a c t Cobalt ions doped zinc oxide nanopowder was prepared at room temperature by a novel and simple one step solid-state reaction method through sonication in the presence of a suitable surfactant Sodium Lau-ryl Sulphate (SLS). The prepared powder was characterized by various spectroscopic techniques. Powder XRD data revealed that the crystal structure belongs to hexagonal and its average crystallite size was evaluated. From optical absorption data, crystal fields (Dq), inter-electronic repulsion parameters (B, C) were evaluated. By correlating optical and EPR spectral data, the site symmetry of Co 2+ ion in the host lattice was determined as octahedral. Photoluminescence spectra exhibited the emission bands in ultraviolet and blue regions. The CIE chromaticity coordinates are also evaluated from the emission spectrum. FT-IR spectra showed the characteristic vibrational bands of ZnAO.
The spectral studies on 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5≤ x ≥25) doped with 0.1 mol% of paramagne... more The spectral studies on 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5≤ x ≥25) doped with 0.1 mol% of paramagnetic CuO impurity are carried out. XRD patterns of powder glass samples confirm the amorphous nature. Urbach energies are shown the structural stability of the systems. The optical band gap energies varies non-linearly within the range of 3.818 – 4.073 eV for direct and 3.770 – 4.024 eV for indirect transitions with the increase of Li2O content. The FT-IR spectral studies show that the glass systems contain BO3 and BO4 units in disordered manner. The structural changes have been observed with alkali contents of the systems. It is observed that the system is more stable at x = 20 mol%. Mixed Alkali Effect phenomenon has been explained in the glass host.
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Papers by Chandragiri Venkata Reddy