gutturu rajasekhara reddy - Academia.edu (original) (raw)

Papers by gutturu rajasekhara reddy

Materials Science in Semiconductor Processing

A B S T R A C T Self-assembled hierarchical rhombus-, spindle-, and peanut-like zinc cobaltite (Z... more A B S T R A C T Self-assembled hierarchical rhombus-, spindle-, and peanut-like zinc cobaltite (ZnCo 2 O 4 , ZCO) microstructures have strategically engineered using an effective solvothermal approach. The various morphology-regulated ZCO samples have obtained by altering the concentration of precursors in the solvent. Effective strategic methods led to various regulated morphologies, as well as different physicochemical properties, such as the surface area/pore size/volume, crystalline nature, and non-stoichiometry of Zn and Co in the ZCO samples. The metal (Zn/Co)/O deficiencies have quantitatively estimated via X-ray photoelectron spectroscopy and confirmed by the Rietveld refinement of ZCO samples using X-ray diffraction data. A mechanistic study has performed to investigate the formation mechanism of the precursor concentration-dependent self-assembled ZCO microstructures. We demonstrate that the specific capacitance of ZCO has proportional to the Zn-deficiency/Co-excess. The Co-deficient-dependent electrochemical properties have studied for three samples and a decline in the following order: P-ZCO (1608.95 F g −1 at 0.35 A g −1 ) > S-ZCO (1007.48 F g −1 at 0.35 A g −1 ) > R-ZCO (629.05 F g −1 at 0.35 A g −1 ). The simple and inexpensive method of synthesized non-stoichiometric ternary metal oxides micro/ nanostructures will introduce new directions in this emerging energy field.

The varied trivalent Samarium ions activated lead borate glass with composition 40B 2 O 3 +35PbO ... more The varied trivalent Samarium ions activated lead borate glass with composition 40B 2 O 3 +35PbO +15Ba 2 CO 3 +(10-x)Li 2 CO 3 + xSm 2 O 3 (where x = 0.0, 0.1, 0.5, 1.0, 1.1, 1.5, 2.0 mol %) have been prepared by adopting melt-quenching method. For investigated glass matrices physical properties like thickness, density and refractive indices, polaron radius etc. were measured/calculated. The investigated glasses are characterized through the X-ray diffractometer (XRD), Fourier Transform Infra-Red (FT-IR), Absorption, Emission and fluor-escence lifetime analysis. The radiative properties for the optimized BPbBaLiSm10 glass have been calculated using J-O spectral intensity parameters. The luminescence spectra consist of four bands at 573, 610, 657 and 718 nm, which were assigned to 4 G 5/2 → 6 H 5/2 , 6 H 7/2 , 6 H 9/2 and 6 H 11/2 transitions of trivalent Sm 3+ ions respectively. In the present investigated glasses, BPbBaLiSm10 glass has highest emission peak intensity for the transition 4 G 5/2 → 6 H 5/2 at 610 nm. The high values of Stimulated emission cross-section (σ emi = 7.56 × 10 −22 cm 2), gain band width parameter (σ emi x τ exp = 15.25 × 10 −28 cm 3) and fluorescence lifetime (τ exp = 0.951 ms) for 4 G 5/2 → 6 H 5/2 transition of BPbBaLiSm10 glass strongly suggesting that the present investigated BPbBaLiSm10 glass may be potential candidate for development of visible lasers and photonics display (red colour) device applications.

Scientific reports, 2019

, respectively, obtained by the XRD analysis. The catalytic activity of the CeO 2 ncs was studied... more , respectively, obtained by the XRD analysis. The catalytic activity of the CeO 2 ncs was studied for the purpose of obtaining the reduction of malachite green (MG) in the presence of sodium borohydride (NaBH 4) at room temperature. Environmental pollution is one of the most serious problems facing human beings and other life forms due to the increasing population, industrialization, and urbanization 1. Dyes are major pollutants that are released from textile industrial effluent 2. Malachite green (MG, including aniline green; basic green 4; diamond green B; and vic-toria green B) is a water-soluble cationic dye that is available in two forms malachite green chloride (C 23 H 25 ClN 2) and malachite green oxalate (C 52 H 54 N 4 O 12) (Table 1). It is used as an industrial dye for the dyeing of leather, wool, silk, cotton, jute, paper and the manufacturing of printing inks and paints 3. The extensive usage of MG dye has caused several health problems, including significant effects on the immune and reproductive systems 4. MG also has the potential to cause genotoxic and carcinogenic effects and is extremely cytotoxic to mammalian cells 5 , and hence the suitable treatment of wastewater containing MG dye is highly necessary. Several methods have been developed, such as physical, chemical, biological, and photocatalytic degradation methods for the treatment of industrial effluent 3,6-9. The physical and chemical methods include adsorption 10 , ion-exchange 11 , irradiation 12 , oxidation processing 13 , chemical precipitation 14 , photolysis 15 , coagulation/flocculation 16 , electrochemical treatment 17 , ozonisation 18 , photo-Fenton degradation 19,20 , reduction and oxidation 21. The biological methods include fungal degradation 22 , bacterial degradation 23 , and aerobic and anaerobic degradation 24. However, these methods are generally expensive, are unable to completely remove the dye, and produce high sludge and by-products that cause secondary pollution 25. In recent years photocatalytic degradation of organic dyes has been used effectively, but this process is slow and energy-consuming. Compared with photocatalytic activity, a catalytic reduction is a relatively fast process without high energy requirements 26. Ce is a rare earth element with a wide bandgap (~3.2 eV), lanthanide series, and exists as a free metal or oscillates between in the Ce 3+ and Ce 4+ oxidation states 27. CeO 2 NCs, also known as nanoceria, have been widely used in catalysis, fast-ion conductors, UV blockers, energy storage, and optical sensors due to its excellent physical and chemical properties 28-31. CeO 2 is an effective catalyst for the removal of organic dyes from effluents because ceria also hops between Ce 3+ and Ce 4+ valence states containing oxygen vacancies that allow NCs to act as regenerative catalysts 32. Various methods have been reported in the literature for the synthesis of ceria 33-37 , including sol-gel 38 , microwave combustion 39 , flame spray pyrolysis 40 , solvothermal 41 , microemulsion 42 , spray drying system 43 , hydrothermal 44 ,

A high-temperature solid state reaction route was employed to synthesize the phosphate based new ... more A high-temperature solid state reaction route was employed to synthesize the phosphate based new orange-red emitting trivalent samarium (Sm 3+ ) ions doped calcium zinc phosphate (CZP: CaZn2(PO4)2) phosphor. The crystalline phase formation was studied by X-ray diffraction analysis. The surface properties of the phosphor were investigated by X-ray photoelectron spectroscopy. Under the excitation of 402 nm, the emission spectra of CZP:Sm 3+ has several peaks and the dominant peak at 596 nm was ascribed to 4 G5/2 → 6 H7/2 transition. The concentration quenching effect of Sm 3+ in CZP phosphor was observed for 5 at%. The mechanism of energy transfer between similar Sm 3+ ions was determined to be quadrupolequadrupole interaction. The decay curves of all phosphors were well fitted to the first-order exponential function. The chromaticity coordinates were located in the orange-red region of the chromaticity diagram. Therefore, these results suggest that the orange-red emitting new CZP:Sm 3+ phosphor to be used in the phosphor-converted white light emitting diodes.

A series of Er 3 þ ions doped tellurium calcium zinc niobium borate glasses were prepared by the ... more A series of Er 3 þ ions doped tellurium calcium zinc niobium borate glasses were prepared by the melt quenching technique. The prepared samples were investigated by optical absorption and near infrared fluorescence spectroscopic studies. The obtained Judd-Ofelt intensity parameters Ω λ (λ ¼2, 4 and 6) were determined through experimental and calculated oscillator strengths obtained from absorption spectra and their results are studied and compared with reported literature. The stark-level energies of 4 I 13/2 excited and 4 I 15/2 ground states were evaluated by using both the absorption and emission measurements. The effect of Er 3 þ ion concentration on the emission intensity of 4 I 13/2-4 I 15/2 transition was discussed. Intense and broad 1.53 mm infrared fluorescence is observed at 980 nm diode laser excitation. Photoluminescence (PL) and its decay behavior studies were carried out for the transition 4 I 13/2-4 I 15/2 at 1.53 mm emission. The broad emission together with higher values of the bandwidth (81 nm), stimulated emission cross-section (32.25 Â 10 À 22 cm 2) and lifetime (530 ms for 1.0 mol% of Er 3 þ) of level 4 I 13/2 make these glasses attractive for broadband amplifiers. From the analysis of spectroscopic data, the present glass is a prospective photonic material for practical applications in the visible and NIR region.

Materials Science in Semiconductor Processing

A B S T R A C T Self-assembled hierarchical rhombus-, spindle-, and peanut-like zinc cobaltite (Z... more A B S T R A C T Self-assembled hierarchical rhombus-, spindle-, and peanut-like zinc cobaltite (ZnCo 2 O 4 , ZCO) microstructures have strategically engineered using an effective solvothermal approach. The various morphology-regulated ZCO samples have obtained by altering the concentration of precursors in the solvent. Effective strategic methods led to various regulated morphologies, as well as different physicochemical properties, such as the surface area/pore size/volume, crystalline nature, and non-stoichiometry of Zn and Co in the ZCO samples. The metal (Zn/Co)/O deficiencies have quantitatively estimated via X-ray photoelectron spectroscopy and confirmed by the Rietveld refinement of ZCO samples using X-ray diffraction data. A mechanistic study has performed to investigate the formation mechanism of the precursor concentration-dependent self-assembled ZCO microstructures. We demonstrate that the specific capacitance of ZCO has proportional to the Zn-deficiency/Co-excess. The Co-deficient-dependent electrochemical properties have studied for three samples and a decline in the following order: P-ZCO (1608.95 F g −1 at 0.35 A g −1 ) > S-ZCO (1007.48 F g −1 at 0.35 A g −1 ) > R-ZCO (629.05 F g −1 at 0.35 A g −1 ). The simple and inexpensive method of synthesized non-stoichiometric ternary metal oxides micro/ nanostructures will introduce new directions in this emerging energy field.

The varied trivalent Samarium ions activated lead borate glass with composition 40B 2 O 3 +35PbO ... more The varied trivalent Samarium ions activated lead borate glass with composition 40B 2 O 3 +35PbO +15Ba 2 CO 3 +(10-x)Li 2 CO 3 + xSm 2 O 3 (where x = 0.0, 0.1, 0.5, 1.0, 1.1, 1.5, 2.0 mol %) have been prepared by adopting melt-quenching method. For investigated glass matrices physical properties like thickness, density and refractive indices, polaron radius etc. were measured/calculated. The investigated glasses are characterized through the X-ray diffractometer (XRD), Fourier Transform Infra-Red (FT-IR), Absorption, Emission and fluor-escence lifetime analysis. The radiative properties for the optimized BPbBaLiSm10 glass have been calculated using J-O spectral intensity parameters. The luminescence spectra consist of four bands at 573, 610, 657 and 718 nm, which were assigned to 4 G 5/2 → 6 H 5/2 , 6 H 7/2 , 6 H 9/2 and 6 H 11/2 transitions of trivalent Sm 3+ ions respectively. In the present investigated glasses, BPbBaLiSm10 glass has highest emission peak intensity for the transition 4 G 5/2 → 6 H 5/2 at 610 nm. The high values of Stimulated emission cross-section (σ emi = 7.56 × 10 −22 cm 2), gain band width parameter (σ emi x τ exp = 15.25 × 10 −28 cm 3) and fluorescence lifetime (τ exp = 0.951 ms) for 4 G 5/2 → 6 H 5/2 transition of BPbBaLiSm10 glass strongly suggesting that the present investigated BPbBaLiSm10 glass may be potential candidate for development of visible lasers and photonics display (red colour) device applications.

Scientific reports, 2019

, respectively, obtained by the XRD analysis. The catalytic activity of the CeO 2 ncs was studied... more , respectively, obtained by the XRD analysis. The catalytic activity of the CeO 2 ncs was studied for the purpose of obtaining the reduction of malachite green (MG) in the presence of sodium borohydride (NaBH 4) at room temperature. Environmental pollution is one of the most serious problems facing human beings and other life forms due to the increasing population, industrialization, and urbanization 1. Dyes are major pollutants that are released from textile industrial effluent 2. Malachite green (MG, including aniline green; basic green 4; diamond green B; and vic-toria green B) is a water-soluble cationic dye that is available in two forms malachite green chloride (C 23 H 25 ClN 2) and malachite green oxalate (C 52 H 54 N 4 O 12) (Table 1). It is used as an industrial dye for the dyeing of leather, wool, silk, cotton, jute, paper and the manufacturing of printing inks and paints 3. The extensive usage of MG dye has caused several health problems, including significant effects on the immune and reproductive systems 4. MG also has the potential to cause genotoxic and carcinogenic effects and is extremely cytotoxic to mammalian cells 5 , and hence the suitable treatment of wastewater containing MG dye is highly necessary. Several methods have been developed, such as physical, chemical, biological, and photocatalytic degradation methods for the treatment of industrial effluent 3,6-9. The physical and chemical methods include adsorption 10 , ion-exchange 11 , irradiation 12 , oxidation processing 13 , chemical precipitation 14 , photolysis 15 , coagulation/flocculation 16 , electrochemical treatment 17 , ozonisation 18 , photo-Fenton degradation 19,20 , reduction and oxidation 21. The biological methods include fungal degradation 22 , bacterial degradation 23 , and aerobic and anaerobic degradation 24. However, these methods are generally expensive, are unable to completely remove the dye, and produce high sludge and by-products that cause secondary pollution 25. In recent years photocatalytic degradation of organic dyes has been used effectively, but this process is slow and energy-consuming. Compared with photocatalytic activity, a catalytic reduction is a relatively fast process without high energy requirements 26. Ce is a rare earth element with a wide bandgap (~3.2 eV), lanthanide series, and exists as a free metal or oscillates between in the Ce 3+ and Ce 4+ oxidation states 27. CeO 2 NCs, also known as nanoceria, have been widely used in catalysis, fast-ion conductors, UV blockers, energy storage, and optical sensors due to its excellent physical and chemical properties 28-31. CeO 2 is an effective catalyst for the removal of organic dyes from effluents because ceria also hops between Ce 3+ and Ce 4+ valence states containing oxygen vacancies that allow NCs to act as regenerative catalysts 32. Various methods have been reported in the literature for the synthesis of ceria 33-37 , including sol-gel 38 , microwave combustion 39 , flame spray pyrolysis 40 , solvothermal 41 , microemulsion 42 , spray drying system 43 , hydrothermal 44 ,

A high-temperature solid state reaction route was employed to synthesize the phosphate based new ... more A high-temperature solid state reaction route was employed to synthesize the phosphate based new orange-red emitting trivalent samarium (Sm 3+ ) ions doped calcium zinc phosphate (CZP: CaZn2(PO4)2) phosphor. The crystalline phase formation was studied by X-ray diffraction analysis. The surface properties of the phosphor were investigated by X-ray photoelectron spectroscopy. Under the excitation of 402 nm, the emission spectra of CZP:Sm 3+ has several peaks and the dominant peak at 596 nm was ascribed to 4 G5/2 → 6 H7/2 transition. The concentration quenching effect of Sm 3+ in CZP phosphor was observed for 5 at%. The mechanism of energy transfer between similar Sm 3+ ions was determined to be quadrupolequadrupole interaction. The decay curves of all phosphors were well fitted to the first-order exponential function. The chromaticity coordinates were located in the orange-red region of the chromaticity diagram. Therefore, these results suggest that the orange-red emitting new CZP:Sm 3+ phosphor to be used in the phosphor-converted white light emitting diodes.

A series of Er 3 þ ions doped tellurium calcium zinc niobium borate glasses were prepared by the ... more A series of Er 3 þ ions doped tellurium calcium zinc niobium borate glasses were prepared by the melt quenching technique. The prepared samples were investigated by optical absorption and near infrared fluorescence spectroscopic studies. The obtained Judd-Ofelt intensity parameters Ω λ (λ ¼2, 4 and 6) were determined through experimental and calculated oscillator strengths obtained from absorption spectra and their results are studied and compared with reported literature. The stark-level energies of 4 I 13/2 excited and 4 I 15/2 ground states were evaluated by using both the absorption and emission measurements. The effect of Er 3 þ ion concentration on the emission intensity of 4 I 13/2-4 I 15/2 transition was discussed. Intense and broad 1.53 mm infrared fluorescence is observed at 980 nm diode laser excitation. Photoluminescence (PL) and its decay behavior studies were carried out for the transition 4 I 13/2-4 I 15/2 at 1.53 mm emission. The broad emission together with higher values of the bandwidth (81 nm), stimulated emission cross-section (32.25 Â 10 À 22 cm 2) and lifetime (530 ms for 1.0 mol% of Er 3 þ) of level 4 I 13/2 make these glasses attractive for broadband amplifiers. From the analysis of spectroscopic data, the present glass is a prospective photonic material for practical applications in the visible and NIR region.