The document describes a method for synthesizing tungsten oxide nanorods using a template synthesis approach. Phosphotungstic acid is infiltrated into an alumina membrane template and then calcined, resulting in the formation of tungsten oxide nanorods inside the template. The nanorods are then characterized using various techniques. Scanning electron microscopy, transmission electron microscopy and atomic force microscopy images show that the nanorods have a diameter of around 200nm, matching the size of the pores in the alumina template. X-ray diffraction and Raman spectroscopy confirm the crystalline monoclinic phase structure of the synthesized tungsten oxide nanorods.
Facile Synthesis and Characterization of Pyrolusite, β-MnO2, Nano Crystal wit...Editor IJCATR
MnO2 nanoparticles have been synthesized by a simple combustion method using MnSO4.4H2O. The crystalline phase, morphology, optical property and magnetic property of the as prepared nanoparticle were characterized using XRD, FT-IR, FT-Raman, SEM, UV-Vis, PL and VSM respectively. Structural studies by XRD indicate that the synthesized material as tetragonal rutile crystal structure. FT-IR and FT-Raman analysis revealed the stretching vibrations of metal ions in tetrahedral co-ordination confirming the crystal structure. The PL and UV analysis having an emission band at 390 nm, showed a prominent blue peak at 453 nm as well as a green emission lines at 553 nm with band gap energy of 3.2eV. Magnetic measurements indicate that the Néel temperature of the β-MnO2 structures is 92.5K for Hc = 100 Oe which showed antiferromagnetic behaviour.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
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Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Facile Synthesis and Characterization of Pyrolusite, β-MnO2, Nano Crystal wit...Editor IJCATR
MnO2 nanoparticles have been synthesized by a simple combustion method using MnSO4.4H2O. The crystalline phase, morphology, optical property and magnetic property of the as prepared nanoparticle were characterized using XRD, FT-IR, FT-Raman, SEM, UV-Vis, PL and VSM respectively. Structural studies by XRD indicate that the synthesized material as tetragonal rutile crystal structure. FT-IR and FT-Raman analysis revealed the stretching vibrations of metal ions in tetrahedral co-ordination confirming the crystal structure. The PL and UV analysis having an emission band at 390 nm, showed a prominent blue peak at 453 nm as well as a green emission lines at 553 nm with band gap energy of 3.2eV. Magnetic measurements indicate that the Néel temperature of the β-MnO2 structures is 92.5K for Hc = 100 Oe which showed antiferromagnetic behaviour.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Photoelectrochemical characterization of titania photoanodes fabricated using...Arkansas State University
Design and fabrication of new electrodes for photo-electrolysis using a material that is photo-active, stable, corrosion resistant, and cost effective.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Maiyalagan, Fabrication and characterization of uniform ti o2 nanotube arrays...kutty79
TiO2 nanotubes have been synthesized by sol–gel template method using alumina membrane.
Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, UV absorption
spectrum and X-ray diffraction techniques have been used to investigate the structure, morphology
and optical properties of TiO2 nanotubes. SEM image showed that TiO2 nanotubes obtained were ordered and
uniform. The diameter and length of the nanotubes were decided by the pore size and thickness of alumina
template. Raman and XRD measurements confirmed the crystallinity and anatase phase of the TiO2 nanotubes.
The optical absorption measurement of TiO2 nanotubes exhibits a blue shift with respect to that of the
bulk TiO2 owing to the quantum size effect.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Photoelectrochemical characterization of titania photoanodes fabricated using...Arkansas State University
Design and fabrication of new electrodes for photo-electrolysis using a material that is photo-active, stable, corrosion resistant, and cost effective.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Maiyalagan, Fabrication and characterization of uniform ti o2 nanotube arrays...kutty79
TiO2 nanotubes have been synthesized by sol–gel template method using alumina membrane.
Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, UV absorption
spectrum and X-ray diffraction techniques have been used to investigate the structure, morphology
and optical properties of TiO2 nanotubes. SEM image showed that TiO2 nanotubes obtained were ordered and
uniform. The diameter and length of the nanotubes were decided by the pore size and thickness of alumina
template. Raman and XRD measurements confirmed the crystallinity and anatase phase of the TiO2 nanotubes.
The optical absorption measurement of TiO2 nanotubes exhibits a blue shift with respect to that of the
bulk TiO2 owing to the quantum size effect.
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...kutty79
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing
agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be
controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by
using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a
glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Electrochemical Synthesis of MoO3 Nanoparticles Effect of Temperature Convert...IJERA Editor
MoO3 nanorods were prepared by electrochemical reduction method using the tetra propyl ammonium bromide (TPAB) was structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio and at current density 14mA &18 mA. The reduction process takes place under atmospheric condition over a period of 2 h. Dried sample was calcinated in muffle furnace at 500ºC. The parameters such as current density and concentration of stabilizers were used to control the size of nanorods. The synthesized MoO3 nanorods were characterized by using UV-Visible, FT-IR, XRD, SEM-EDS and TEM analysis techniques.
Fabrication and characterization of nickelijoejournal
This paper shows that nickel nanowires of length 11μm and diameters 800 and 15nm were grown within
the pores of nuclear track polycarbonate membrane by electrodepositing nickel. Surface morphology and
crystallographic structure of the deposited nanowires was investigated using SEM, TEM and XRD
respectively. It is found that low current density gives good result, while high current density leads to the
formation of curled nanowires. Fabricated nanowires were further investigated for electrical properties
and found that nanowires obey ohm’s law. Through structural characterization it has been observed that
the fabricated nanowires posses FCC lattice structure.
Synthesis of MWNTs, DWNTs and SWNTs buckypaper using triton x 100. and compar...Awad Albalwi
In this study buckypaper of MWNTs, DWNTs and SWNT have been synthesised using filtration of carbon nanotubes dispersed in 1% TritonX 100 as solvents. Dispersions were generated by pulse sonication of each single wall carbon nanotubes (SWNTs) , Double wall carbon nanotubes (DWNTs) and Multi wall carbon nanotubes in TritonX solvent. Fist, sonication times were investigated for these CNTs to determine the optimum conditions for generating stable dispersions of carbon nanotubes. It was found that optimal dispersions could be generated using Trion X-100 solvent with all these carbon nanotube by using 30minute periods of pulse sonication. The Three buckypapers of MWNTs, DWNTs and SWNTs were produced by filtering dispersions of carbon nanotubes which had undergone 30 minutes of pulse sonication in TritonX100. Conductivity and measurements of the three buckypaper (SWNT,DWNT&MWNT) samples yielded average values of 14.24 , 23 and 19 Scm-1 respectively. Mechanical measurements were determined successfully . Homogeneity in the produced buckypapers were investigated confirming by scanning electron microscopy .
Synthesis and Characterisation of Copper Oxide nanoparticlesIOSR Journals
Cupric oxide (CuO) nanoparticles were prepared by the chemical route by calcinations at a higher temperature from 300oC to 400 oC. For the comparison transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements were made through JCPDS. There is good agreement between data produced by spectroscopy and the microscopic measurements.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Facile Synthesis and Characterization of Pyrolusite, β- MnO2, Nano Crystal wi...Editor IJCATR
MnO2 nanoparticles have been synthesized by a simple combustion method using MnSO4.4H2O. The crystalline phase,
morphology, optical property and magnetic property of the as prepared nanoparticle were characterized using XRD, FT-IR, FTRaman,
SEM, UV-Vis, PL and VSM respectively. Structural studies by XRD indicate that the synthesized material as tetragonal rutile
crystal structure. FT-IR and FT-Raman analysis revealed the stretching vibrations of metal ions in tetrahedral co-ordination confirming
the crystal structure. The PL and UV analysis having an emission band at 390 nm, showed a prominent blue peak at 453 nm as well as
a green emission lines at 553 nm with band gap energy of 3.2eV. Magnetic measurements indicate that the Néel temperature of the β-
MnO2 structures is 92.5K for Hc = 100 Oe which showed antiferromagnetic behaviour
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Introduction to nanoscience and nanotechnologyaimanmukhtar1
Introduction of nanoscience/nanotechnology ,properties/potential applications of nanomaterials and electrodeposition of metal single component and alloy nanowires in AAO template
EFFECT OF ULTRAVIOLET RADIATION ON STRUCTURAL PROPERTIES OF NANOWIRESijoejournal
Copper nanowires were prepared through electrochemical template synthesis using Nucleopore polycarbonate membranes having nominal pore sizes of 800nm and 15nm diameter. The 800nm and 15nm nanowires thus grown were viewed under SEM and TEM respectively, while their FCC crystallographic structure was confirmed through X-ray and electron diffraction patterns. The X-ray diffraction peaks indicated strong texturing for (200). The texturing was found to reduce significantly upon exposure to ultraviolet radiation.
Review on recent progress in nitrogen doped graphene synthesis, characterizat...materials87
Nitrogen doping has been an effective way to
tailor the properties of graphene and render its potential use
for various applications. Three common bonding configurations
are normally obtained when doping nitrogen into the
graphene: pyridinic N, pyrrolic N, and graphitic N. This paper
reviews nitrogen-doped graphene, including various synthesis
methods to introduce N doping and various characterization
techniques for the examination of various N bonding
configurations. Potential applications of N-graphene are also
reviewed on the basis of experimental and theoretical studies
Green synthesis of well dispersed nanoparticles using leaf extract of medicin...
Fabrication, morphology and structural characterization of tungsten oxide nanorods
1. Full Paper
Fabrication, morphology and structural characterization of
tungsten oxide nanorods
T.Maiyalagan, B.Viswanathan*
National Center for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras,
Chennai 600 036, (INDIA)
Phone : +91-044-22574200 ; Fax: +91-44-22574202
E-mail : bvnathan@iitm.ac.in
Received: 1 September, 2007 ; Accepted: 6th September, 2007
st
ABSTRACT KEYWORDS
The Template synthesis of Tungsten oxide nanorods by calcination of Tungsten oxide nanorods;
Phosphotungtstic acid (HPW) on alumina membrane template is described. Template synthesis;
The nanorods were characterized by electron microscopic analyses, Raman, Alumina template.
IR and X-ray diffraction techniques. SEM, TEM and AFM images reveal the
hollow structures and vertically aligned features of the nanotubes and the
phase structure of the WO3 was proved by X-ray diffraction. In addition, it
is observed that the cycle ability of the nanorods is superior to that of bulk
materials, which implies that the morphology has an influence on the elec-
trochemical performances of the material.
2007 Trade Science Inc. - INDIA
INTRODUCTION The rich structural chemistry of tungsten oxides encom-
passes a multitude of interesting compounds and a wide
There is great interest in the synthesis of one-di- spectrum of tungstic acids and different WO3 phases.
mensional nanostructured materials because of its po- Tungsten oxide is an important functional material. In
tential applications in many areas. Metal-oxide semi- recent years, a variety of nanometer-scaled structures
conductors such as WO3, TiO2, and ZnO and SnO2 of tungsten oxide have been developed. These nano
are widely used in sensors, having high detection ability structures have demonstrated promising properties. To
and stability[1–3]. These transition metal oxides have date, WO3 has been one of the most extensively stud-
drawn much attention from scientists in recent years ied materials for its Electrochromic, photochromic and
because they are applied as electrochromic materials. thermo chromic properties for use in devices, such as
Their potential applications include several technologi- information displays, sensor devices and smart Win-
cal areas. Tungsten metal, tungsten oxides and tung- dows. In addition, WO3 has a high potential for use in
states represent a fascinating class of materials. Tung- electrochemical devices, such as rechargeable lithium
sten wires/filaments are widely used as tips for field batteries, owing to its rich chemical intercalation reac-
emission and tips for scanning tunneling microscopy[4]. tivity. The oxides of transition metal tungsten have at-
2. 2 Tungsten oxide nanorods
.
tracted constant research interest for the past few de- pared by oxidation at high temperature well-oriented
Full Paper
cades due to their wide applicability as gas sensors for WOx nanorods on a(0. 01)W surface.
SO2 and H2S[5,6], as excellent field emitters(specifically However, the study on nanoscaled WO3 materials
W18O49)[7] and as photo anodes in photochemical is still in its infancy due to lack of suitable preparation
cells[8]. In addition, WOx have also found unique appli- method. In the present work, we report a novel route
cation in electro chromic devices due to their excellent for template synthesis of crystalline WO3 nanorods. Our
voltage-modulated optical properties[9]. Tungsten work on the tungsten oxide tubular structures featured
oxide(WO3) is an n-type semiconductor with a reported a low cost and an easy manipulation technique. In the
band gap of about 2.6-2.8eV[10]. The intrinsic conduc- fabrication, no catalyst was involved and only a rough
tivity arises from its non-stoichiometric composition- vacuum was required.
giving rise to a donor level formed by oxygen vacancy
defect in the lattice. Since tungsten has many oxidation EXPERIMENTAL
states, i.e., 2, 3, 4, 5 and 6, the tungsten compound can
exist in many forms. For instance, the typical forms of Materials
tungsten oxides are tungsten(VI) oxide(WO3, lemon All the chemicals used were of analytical grade.
yellow appearance) and tungsten(IV) oxide(WO2, Phosphotungstic acid(Sisco Research Laboratories,
brown and blue appearance)[11]. Such electronic prop- India), dichloromethane and concentrated HF(Merck)
erties make the tungsten oxides suitable for various ap- were used. Alumina template membranes were obtained
plications such as electrochromic[12], photochromic[13], from Whatman Anopore Filters. Anodisc alumina mem-
photocatalyst[14], and gas sensors[15-17]. Various meth- branes with a pore size of 200nm and thickness of 60m
ods including chemical vapour deposition[18], electro- were purchased from Whatman(catalog no. 6809-
chemical deposition[19], laser vaporization[20, 21] have 6022; Maidstone, U.K.).
been used to prepare tungsten oxide thin films. In con-
ventional WO3 thin films with nanoscale-sized grains, Synthesis of Tungsten oxide nanorods.
the electrical conduction is mainly controlled by free 10g of Phosphotungtstic acid(H3PW12O40) was
carrier transport across the grain boundaries. So the stirred in a 30ml of methanol solution. The resulting
synthesis of mono crystalline tungsten oxide as nano colloidal suspension was infiltrated into the membrane
wires or nanorods is of great interest. In the past years, under vacuum by wetting method. The same proce-
Zhu et al.[22] produced a micrometer scale tree-like struc- dure was repeated 1 to 8 times. The upper surface of
ture by heating a tungsten foil, partly covered by SiO2 the membrane was then polished gently by sand pa-
in Ar atmosphere at 16000C. These nanostructures were per(2500 grit) and dried at 368 K for 1 h. The forma-
composed by monoclinic W18O49 nanoneedles and WO3 tion of WO3 nanorods inside alumina template(WO3 /
nanoparticles. Nanorods of several oxides including AAO) was further achieved by programmed tempera-
WO3 have been prepared by templating on acid-treated ture thermal decomposition from 95 to 5000C min-1 and
carbon nanotubes[23]. By heating WS2 in oxygen, fibers finally calcinated at 873K for 3h in air. The removal of
of W18O49 were produced with a pine-treelike struc- the AAO template was performed by dissolving alu-
ture[24]. Mixtures of WO2 and WO3 with nanorods mina template in 10%(v/v) HF. The WO3 nanorod prod-
structure were obtained by Koltypin et al.[25] via amor- uct was washed with a copious amount of deionized
phous tungsten oxide nanoparticles. Li et al.[26] have water, to remove the residual HF and dried at 393 K.
synthesized WO3 nanobelts and nanorods via physical Characterization methods
vapour deposition process where the nanostructures
were deposited on silicium wafers maintained at 6000C. The scanning electron micrographs were obtained
Recently Liu et al.[27] reported on the preparation of after the removal of alumina template using a JEOL
tungsten oxide nanowires through a vapour-solid growth JSM-840 model, working at 15keV. For transmission
process by heating a tungsten wire partially wrapped electron microscopic studies, the nanorods dispersed
with boron oxide at 12000C and Shingaya et al.[28] pre- in ethanol were placed on the copper grid and the im-
3. T.Maiyalagan and B.Viswanathan 3
temperature with 514.5nm excitation in backscattered
Full Paper
mode using Bruker FRA106 FT-Raman instrument. The
IR spectrum was recorded with Perkin-Elmer (L-710)
spectrophotometer.
Electrochemical measurements
The catalyst was electrochemically characterized
by cyclic voltammetry(CV) using an electrochemical
analyzer(Bioanalytical Sciences, BAS 100). A common
three-electrode electrochemical cell was used for the
Figure 1 : (a) SEM Micrograph of the WO3 nanorod and (b) measurements. The counter and reference electrodes
AFM micrograph of the nanorod
were a platinum plate(5cm2) and a saturated Ag/AgCl
electrode respectively. The CV experiments were per-
formed using 1M H2SO4 solution at a scan rate of 50
mV/s. All the solutions were prepared by using ultra
pure water (Millipore, 18M). The electrolytes were
degassed with nitrogen before carrying out the electro-
chemical measurements.
Preparation of working electrode
Figure 2 : (a) TEM Micrograph of the WO3 nanorod and (b) Glassy carbon (GC) (BAS Electrode, 0.07cm2) was
EDS pattern of nanorod
polished to a mirror finish with 0.05m alumina sus-
pensions before each experiment and this served as an
underlying substrate of the working electrode. In order
to prepare the composite electrode, the nanorods were
I% Transmittance
dispersed ultrasonically in water at a concentration of
1mg ml-1 and 20l aliquot was transferred on to a pol-
ished glassy carbon substrate. After the evaporation of
water, the resulting thin catalyst film was covered with
5-wt% Nafion solution. Then the electrode was dried
at 353 K and used as the working electrode.
Wave number(cm -1 )
Figure 3 : FT-IR Spectrum of the (a) Calcined HPW (b) RESULTS AND DISCUSSION
Bulk WO3 and (c) WO3 nanorods
The morphology of tungsten oxide nanorods was
ages were obtained using Phillips 420 model, operating studied with SEM, AFM, transmission electron micros-
at 120keV. The nanorods were sonicated in acetone copy (TEM) images on a Philips CM12/STEM instru-
for 20 minutes and then dropped on cleaned Si sub- ment. The scanning electron microscopy (SEM) image
strates. Next the AFM imaging was performed in air presented in figure 1(a) shows the rod like morphology
using a Nanoscope IIIA atomic force microscope (Digi- of the product. Further the AFM image confirms the
tal Instruments, St. Barbara, CA) operated in contact rod like morphology in figure 1(b) which represents low
mode. magnification. The morphology of the nanorods can be
The X-ray diffraction patterns were obtained on a confirmed with TEM micrograph shown in figure 2(a).
Philips PW1820 diffractometer with CuKá (1.54178 Å) The dimensions of the nanorods were matched with the
radiation. The WO3 nanorods placed in glass capillary outer diameter of the template used. The diameter of
tubes were used for recording Raman spectrum at room the nanorods was found to be around 200nm.
4. 4 Tungsten oxide nanorods
.
Full Paper
Intensity(a.u.)
Current(mA)
Potential(V)
Raman shift (cm-1 )
Figure 4 : Raman spectrum of the WO3 nanorods
Current(mA)
Intensity(a.u.)
Potential(V)
Figure 6 : Cyclic voltammograms for (a) Bulk WO3 and
(b) WO3 nanorods in 1M H2SO4 at scan rate of 50mV s-1 at
298K
20(degrees)
813cm-1 correspond to the stretching modes of the
Figure 5 : XRD patterns of (a) HPW and (b) WO3 nanorods
WO3[30-32]. The XRD pattern for the as-synthesized
The composition of the nanorods was investigated tungsten oxide nanorods and Phosphotungstic acid are
using an energy dispersion spectroscopy (EDS). Figure given in figure 5(a,b) respectively. The diffraction peaks
2(b) shows EDS of the WO3 nanorods. EDS analysis and the peak intensities of the tungsten oxide nanorods
indicates that the nanorods are mainly composed of W are in good agreement with the diffraction peaks of crys-
and O (the Cu signal comes from the TEM grids). No talline monoclinic phase of WO [33,34].
3
evidence of impurities was detected in the WO3 nanorods. The electrochemical behavior of bulk WO3 and
The FT-IR spectra of WO3 nanorods recorded in WO nanorods were studied in 1M H SO as shown in
3 2 4
the region 400-3500cm-1 are shown in figure 3. The figure 6. The cyclic voltammogram shows an anodic
broad band from 1000cm-1 to 500cm-1 corresponds to peak current at -0.07V and it is due to the formation of
the W-O vibrational mode. It has been widely reported tungsten bronzes by hydrogen intercalation in the tung-
that HPW with Keggin structures gives several strong, sten trioxide. The electrochemical response due to W
typical IR bands at ca. 1079cm-1(stretching frequency is seen at -0.1V in the forward scan, which matches
of P-O of the central PO4 tetrahedron), 983cm-1(ter- with the peak reported in literature[30]. Further, the sta-
minal bands for W=O in the exterior WO6 octahedron), bility of tungsten trioxides in sulphuric acid medium was
889 cm-1 and 805 cm-1(bands for the W-Ob-W and W- evaluated by carrying out the cyclic voltammetry by
Oc-W bridge, respectively)[29]. repeating voltammetric cycles in 1M H2SO4. An initial
The raman spectra of WO3 nanorods exhibiting decrease in current was observed and after few cycles
bands at 717 and 808cm-1 are shown in figure 4. These the peak current remained the same even after 50 cycles
bands agree closely to the wave numbers of the stron- and this confrims the stability of WO nanorods in sul-
3
gest modes of monoclinic-WO3. The bands at 703 and furic acid medium.
5. T.Maiyalagan and B.Viswanathan 5
CONCLUSIONS [14] G.R.Bamwenda, H.Arakawa; Appl.Catal., A210,
Full Paper
181 (2001).
In summary, a simple template synthesis method [15] M.Akiyama, J.Tamaki, N.Miura, N.Yamazoe;
has been described for preparing WO3 nanorods by a Chem.Lett., 16, 11 (1991).
[16] A.A.Tomchenko, V.V.Khatko, I.Emelianov; Sens.
direct calcination of Phosphotungtstic acid(HPW) in the
Actuators, B46, 8 (1998).
channels of the alumina template. The size of nanorods
[17] D.S.Lee, S.D.Han, J.S.Hun, D.D.Lee; Sens.
is around 200nm which matches with the diameter of Actuators, B60, 57 (1999).
the template used. The Tungsten oxide nanorods with [18] E.Brescacin, M.Basato, E.Tondello; Chem.Mater.,
controlled morphology and composition have been 11, 314 (1999).
achieved. The morphology of the aligned nanostructures [19] Z.R.Yu, X.D.Jia, J.H.Du, J.Y.Zhang; Sol.Energy
was verified by SEM, AFM and TEM. It was found Mater.Sol.Cells, 64 55 (2000).
that WO3 nanorods exhibit higher electrochemical ac- [20] M.Sun, N.Xu, J.W.Yao, E.C.Wang; J.Mater.Res.,
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[21] S.T.Li, M.S.El-Shall; Nanostruct.Mater., 12, 215
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