This document summarizes research on electrodepositing silver nanoparticles onto carbon sphere surfaces using a pulse current. Key findings include:
1) Silver nanoparticles were successfully electrodeposited with a size of 100-400nm after 2 minutes using a pulse current.
2) Deposition occurred on accessible carbon surface sites, forming a monolayer of scattered nanoparticles. Continued deposition led to larger particles and multilayers.
3) Pulse current helped manage monolayer deposition compared to direct current, controlling particle size and number of layers.
M.Sc. Chemical Engineering Thesis Defense (Omer Farooqi)Omer Farooqi
This is the presentation for my M.Sc. research thesis. I worked on a novel electrode preparation method to carry out voltammetry in order to detect heavy metals in water.
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.
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.
M.Sc. Chemical Engineering Thesis Defense (Omer Farooqi)Omer Farooqi
This is the presentation for my M.Sc. research thesis. I worked on a novel electrode preparation method to carry out voltammetry in order to detect heavy metals in water.
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.
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.
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.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Zno and znopbs heterojunction photo electrochemical cellseSAT Journals
Abstract Photo Electrochemical Cell (PEC) can also be used for splitting of water into hydrogen and Oxygen. Here, ZnO nanorod PEC has been prepared in hydrothermal method and ZnO/PbS quantum dot PEC has been prepared by hydrothermal method and chemical bath deposition method. UV-Visible spectroscopy has been observed. Flat band voltage, bandwidth and majority charge carriers have been calculated from Mott-Schottky. Impedance variation at semiconductor and electrolyte junction has been observed with Electrochemical Impedance Spectroscopy (EIS). Keywords: Hydrothermal, Chemical bath, ZnO/PbS, UV-Vis, Mott-Schottky, EIS.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
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.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...Pawan Kumar
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
In recent times perovskite materials are extensively studied and have attracted much attention because they exhibit interesting the properties, showing potential applications in commercial, technical and biomedical. In Vietnam, perovskite materials be of interest research and applications are strong but with major research direction is to go deep into the electrical properties and the magnetic properties. The Lanthanum Strontium manganite is a perovskite-based crystal-structured ceramic material with the formula of La1-xSrxMnO3, where x describes the doping ratio. It has attracted much attention due to its good magnetic, electrical, and catalytic properties and is becoming an attractive possibility material in several biomedical applications, particularly with nano-size. In industry, this material is commonly used in as a cathode material in commercially produced solid oxide fuel cells. In this thesis, we present the Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized of the nanosize La1-xSrxMnO3 at x = 0; 0.1; 0.2; 0.3 and 0.4 which prepared by a modified sol-gel method. Structure and magnetic properties of them were systematically investigated in dependence on doped Sr ratio x. The structure was investigated by XRD and show slightly changed but magnetic properties varied strongly with changing the doping ratio x. Magnetic properties of samples were studied by Vibrating Sample Mode of Physical Properties Measurement System show at the room temperature, the samples show superparamagnetic properties with high saturated magnetization MS of 57 emu/g which strongly dependents on the doped Sr ratio x.
Gamry’s eQCM 10M™ is a rapid, impedance-scanning electrochemical quartz crystal microbalance (EQCM) that adds a valuable tool in the analytical toolbox of anyone investigating interfacial processes.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
This study aims to employ low-cost agro waste
biosorbent tamarind (Tamarindus indica) pod shells and
activated carbon prepared by complete and partial pyrolysis of
tamarind pod shell for the removal of hexavalent chromium
ions from aqueous solution. The effect of parameters namely,
initial metal ion concentration, pH, temperature, biomass
loading on chromium removal efficiency were studied. More
than 96.9% removal of Chromium was achieved using crude
tamarind pod shells as biosorbent. The experimental data
obtained were fitted with Langmuir, Freundlich, Temkin and
Redlich-Peterson adsorption isotherm models. The
experimental data fits well to Langmuir, Freundlich and
Temkin isotherms with regression coefficient R2 more than 0.9.
For Redlich-Peterson adsorption isotherm the experimental
data does not fit so well. The crude tamarind had maximum
monolayer adsorption capacity of 40 mg/g and a separation
factor of 0.0416 indicating it as best adsorbent among the three
tested adsorbent. Further, an attempt is made to fit sorption
kinetics with pseudo first order and pseudo second order
reactions. Pseudo second order kinetics model fits well to the
experimental data for all three adsorbents.
A supply chain consists of all parties involved
directly or indirectly, in fulfilling a customer request. The supply
chain includes not only the manufacturers and suppliers, but also
transporters, workhouse, retailers and even customers
themselves. Within each organization, such as a manufactures,
the supply chain includes all functions involved in receiving and
filling a customer request. These functions include, but are not
limited to, new product development, marketing operations,
distributions, finance, and customer service. Supply chain
management (SCM) is the management of an interconnected or
interlinked between network, channel and node businesses
involved in the provision of product and service packages
required by the end customers in a supply chain. Supply chain
management spans the movement and storage of raw materials,
work-in-process inventory, and finished goods from point of
origin to point of consumption. It is also defined as the "design,
planning, execution, control, and monitoring of supply chain
activities with the objective of creating net value, building a
competitive infrastructure, leveraging worldwide logistics,
synchronizing supply with demand and measuring performance
globally.
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.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Zno and znopbs heterojunction photo electrochemical cellseSAT Journals
Abstract Photo Electrochemical Cell (PEC) can also be used for splitting of water into hydrogen and Oxygen. Here, ZnO nanorod PEC has been prepared in hydrothermal method and ZnO/PbS quantum dot PEC has been prepared by hydrothermal method and chemical bath deposition method. UV-Visible spectroscopy has been observed. Flat band voltage, bandwidth and majority charge carriers have been calculated from Mott-Schottky. Impedance variation at semiconductor and electrolyte junction has been observed with Electrochemical Impedance Spectroscopy (EIS). Keywords: Hydrothermal, Chemical bath, ZnO/PbS, UV-Vis, Mott-Schottky, EIS.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
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.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...Pawan Kumar
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
In recent times perovskite materials are extensively studied and have attracted much attention because they exhibit interesting the properties, showing potential applications in commercial, technical and biomedical. In Vietnam, perovskite materials be of interest research and applications are strong but with major research direction is to go deep into the electrical properties and the magnetic properties. The Lanthanum Strontium manganite is a perovskite-based crystal-structured ceramic material with the formula of La1-xSrxMnO3, where x describes the doping ratio. It has attracted much attention due to its good magnetic, electrical, and catalytic properties and is becoming an attractive possibility material in several biomedical applications, particularly with nano-size. In industry, this material is commonly used in as a cathode material in commercially produced solid oxide fuel cells. In this thesis, we present the Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized of the nanosize La1-xSrxMnO3 at x = 0; 0.1; 0.2; 0.3 and 0.4 which prepared by a modified sol-gel method. Structure and magnetic properties of them were systematically investigated in dependence on doped Sr ratio x. The structure was investigated by XRD and show slightly changed but magnetic properties varied strongly with changing the doping ratio x. Magnetic properties of samples were studied by Vibrating Sample Mode of Physical Properties Measurement System show at the room temperature, the samples show superparamagnetic properties with high saturated magnetization MS of 57 emu/g which strongly dependents on the doped Sr ratio x.
Gamry’s eQCM 10M™ is a rapid, impedance-scanning electrochemical quartz crystal microbalance (EQCM) that adds a valuable tool in the analytical toolbox of anyone investigating interfacial processes.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
This study aims to employ low-cost agro waste
biosorbent tamarind (Tamarindus indica) pod shells and
activated carbon prepared by complete and partial pyrolysis of
tamarind pod shell for the removal of hexavalent chromium
ions from aqueous solution. The effect of parameters namely,
initial metal ion concentration, pH, temperature, biomass
loading on chromium removal efficiency were studied. More
than 96.9% removal of Chromium was achieved using crude
tamarind pod shells as biosorbent. The experimental data
obtained were fitted with Langmuir, Freundlich, Temkin and
Redlich-Peterson adsorption isotherm models. The
experimental data fits well to Langmuir, Freundlich and
Temkin isotherms with regression coefficient R2 more than 0.9.
For Redlich-Peterson adsorption isotherm the experimental
data does not fit so well. The crude tamarind had maximum
monolayer adsorption capacity of 40 mg/g and a separation
factor of 0.0416 indicating it as best adsorbent among the three
tested adsorbent. Further, an attempt is made to fit sorption
kinetics with pseudo first order and pseudo second order
reactions. Pseudo second order kinetics model fits well to the
experimental data for all three adsorbents.
A supply chain consists of all parties involved
directly or indirectly, in fulfilling a customer request. The supply
chain includes not only the manufacturers and suppliers, but also
transporters, workhouse, retailers and even customers
themselves. Within each organization, such as a manufactures,
the supply chain includes all functions involved in receiving and
filling a customer request. These functions include, but are not
limited to, new product development, marketing operations,
distributions, finance, and customer service. Supply chain
management (SCM) is the management of an interconnected or
interlinked between network, channel and node businesses
involved in the provision of product and service packages
required by the end customers in a supply chain. Supply chain
management spans the movement and storage of raw materials,
work-in-process inventory, and finished goods from point of
origin to point of consumption. It is also defined as the "design,
planning, execution, control, and monitoring of supply chain
activities with the objective of creating net value, building a
competitive infrastructure, leveraging worldwide logistics,
synchronizing supply with demand and measuring performance
globally.
—Stochastic processes have many useful applications
and are taught in several university programmers. In this paper
we are using stochastic process with complex concept on Markov
chains which uses a transition matrix to plot a transition diagram
and there are several examples which explains various type of
transition diagram. The concept behind this topic is simple and
easy to understand.
This research deals with study of Degradation
behavior of starch blended with different percentage of
polypropylene (PP) .Twin screw extruder at 160- 190 °C and 50
rpm is used for manufacture of blend sheet. Degradation test
achieved according to ASTM standard (D 638 IV and D570-98).
Studies on their degradation properties were carried out by Soil
burial test, Water absorption test and Hydrolysis test. The
morphology test of the polypropylene / starch blend samples
was obviously seen in the (Dino- Light- Digital Microscope),
Results of soil burial test show that tensile strength and
percentage of elongation of polypropylene / starch blend
decrease with increasing the starch content and burial time. The
hydrolysis test show the weight losses increasing with the
increasing amount of starch. High percent of polypropylene
found to decrease the amount of water absorption of the blend.
The physical appearance and morphology studies of
polypropylene / starch blend after burial test in soil and
hydrolysis in water environment showed that all blend samples
was obviously changed after 90-day study period, whereas the
pure polypropylene samples remained unchanged
RFID-based public transport ticketing systems
rely on widespread networks of RFID readers that locate
the user within the transport network in real time to be
able to verify whether he can travel at that time with the
ticket he holds. This paper presents a system that uses that
same RFID-based location information to give the user
navigation indications depending on his current location
provided that the user has indicated beforehand the places
he intends to visit. The system was designed to be costeffectively
deployable on the short term but open for easy
extension. This paper is based on ticketing and
identification of the passenger in the public transport. In
the metropolitan city like Mumbai, Kolkata we have a
severe malfunction of public transport and various
security problems. Firstly, there is a lot of confusion
between the passengers regarding fares which lead to
corruption, Secondly due to mismanagement of public
transport the passengers faces the problem of traffic jam,
thirdly nowadays we have severe security problems in
public transport due anti-social elements.The entire
network comprises of three modules; Base Station Module,
In-Bus Modules and Bus Stop Module. The base station
module consists of monitoring system which includes GSM
and a PC. The In-Bus Modules consists of two
Microcontrollers, GSM Modem, GPS, Zigbee, RFID, LCD
and infrared sensor. RFID for ticketing purpose, GSM,
GPS is used for mobile data transmission and tracking
location. The Zigbee module is also interfaced with the
microcontroller which is used to send the bus information
to bus stop and to get the information from the bus stop to
bus. The Bus Stop Module is fixed at every bus stop
consists of Zigbee node which is interfaced with the
Microcontroller.
-In the field of Agriculture most important things
are fertility of soil, nutrition’s available in soil, water availability
in that area, atmospheric conditions .All these parameters are
playing the measure roll regarding the productivity of crop .In
this paper we are trying to go through the techniques which will
show us how to improve productivity with the minimum use of
natural resources like water, and avoid leaching of soil by using
fertilizers through drip. This can be used in greenhouse or open
environments to efficiently monitor soil moisture and
temperature, ambient temperature, and humidity. Wired
communications, sensor networks, and other complementary
technologies provide the necessary tools to compile and processes
physical variables, including temperature, humidity, and soil
moisture, pH of soil, fertilizer concentrations. Greenhouse and
precision agricultural, in general, demand real-time precise
measurement of these parameters in order to avoid unnecessary
exposure to unhealthy ambient conditions, assure maximum
productivity and provide value-added quality. This paper aims to
implement the basic application of automizing the irrigation field
by programming the components and building the necessary
hardware with ARM7 Processor. This is used to find the exact
field condition and maintaining their levels in the soil
In current year, endurable and entire renewable
energy resources are extensively used in electrical energy
generation system. Mainly, solar energy conservation systems
are apply in stand -alone system. Solar panels covert solar
radiation into direct electrical energy. Solar panels are one of
the most potential renewable energy technologies for refreshing
building. In this study, responsibility analysis of a solar system
installed in my collage academic block and hostel is
investigated. The system includes solar panel, battery,
generator, converter and loads. In this study we calculate
overall load in academic block (Electrical engineering
department and round building) and only boy hostel. After
knowing overall loads result for these buildings we simulate
this data through HOMER tool and we obtain the best result
which is presented in this paper.
The result obtained from the optimization gives the initial
capital cost as 296.000$ while operating cost is 2,882$/yr. Total
net present cost (NPC) is 332,846$ and the cost of energy
(COE) is 0.212$/kWh.
The main purpose of this research paper is that the
maximum demand of energy consumption for both academic
block and hostel are simulated through solar panel, for this
purpose which amount of solar panel and battery is required.
Bio-char can be produced by thermal conversion of
biomass. Palm shells were obtained from palm fruits (palmira).
They were air-dried to remove moisture. The dried palm shells
were ground to become powder and heated at 600ºC, 800ºC and
1000ºC for 2 h respectively. After heating, bio-char was obtained.
Structural properties of palm shell powder and bio-char were
examined by X-ray diffraction (XRD). Scanning electron
microscopy (SEM) was used to observe microstructure of biochar.
Properties such as hydration capacity, pH were also
evaluated.
This study was designed to evaluate the effect of
70% ethanolic crude extract of Portulaca oleracea L on mice
orgons . (In vivo),In vivo, the acute toxicity of 70 % ethanolic
extract of the plant on normal mice was studied. No toxic effect
was noted on normal mice even at 9500 mg /kg B.W S/C
injection.Histopathological changes due to ethanolic extract of
the plant in healthy mice were summarized in hyperplasia of
white pulp with amyloid deposition, proliferation of
megakaryocytes and mononuclear cell infiltration in the liver and
kidney parenchyma. There were no significant lesions detected in
the brain, heart and ovary in all treated groups.
When a ductile material with a crack is loaded in
tension, the deformation energy builds up around the crack tip
and it is understood that at a certain critical condition voids are
formed ahead of the crack tip. The crack extension occurs by
coalescence of voids with the crack tip. The “characteristic
distance” (Lc) defined as the distance b/w the crack tip & the void
responsible for eventual coalescence with the crack tip. Nucleation
of these voids is generally associated with the presence of second
phase particles or grain boundaries in the vicinity of the crack tip.
Although approximate, Lc assumes a special significance since it
links the fracture toughness to the microscopic mechanism
considered responsible for ductile fracture. The knowledge of the
“characteristic distance” is also crucial for designing the size of
mesh in the finite element simulations of material crack growth
using damage mechanics principles. There is not much work
(experimental as well as numerical) available in the literature
related to the dependency of “characteristic distance” on the
fracture specimen geometry. The present research work is an
attempt to understand numerically, the geometry dependency of
“characteristic distance” using three-dimensional FEM analysis.
The variation of “characteristic distance” parameter due to the
change of temperature across the fracture specimen thickness was
also studied. The work also studied the variation of “characteristic
distance”, due to the change in fracture specimen thickness.
Finally, the ASTM requirement of fracture specimen thickness
criteria is evaluated for the “characteristic distance” fracture
parameter. “Characteristic distance” is found to vary across the
fracture specimen thickness. It is dependent on fracture specimen
thickness and it converges after a specified thickness of fracture
specimen. “Characteristic distance” value is also dependent on the
temperature of ductile material. In Armco iron material, it is
found to decrease with the increase in temperature.
Cloud computing solves the problem of real
time demand information and visibility at different location by
which information can be delivered with reliability, scalability
and flexibility between the supplier and customer. Logistics
network requires effective information flow for technical support
by which logistics infrastructures can be totally utilized and
tracked the information collection, transmission and operation.
Cloud is fast growing technology which can effectively reduce the
intermediate cost of flow of information and improve the link
between the logistics partners and customers. This paper
analyzes the advantages of cloud based logistics network and
defines in which way a logistics network manages Information
Flow Control (IFC) over the cloud, which allows the logistics
network to do work effectively.
A young astronomer’s by now ten years old
results are re-told and put in perspective. The implications are
far-reaching. Angular-momentum shows its clout not only in
quantum mechanics where this is well known, but is also a
major player in the space-time theory of the equivalence
principle and its ramifications. In general relativity, its
fundamental role was largely neglected for the better part of a
century. A children’s device – a friction-free rotating bicycle
wheel suspended from its hub that can be lowered and pulled
up reversibly – serves as an eye-opener. The consequences are
embarrassingly far-reaching in reviving Einstein’s original
dream
The technical study had been performed on
many foreign languages like Japanese; Chinese etc. but the
efforts on Indian ancient script is still immature. As the Modi
script language is ancient and cursive type, the OCR of it is still
not widely available. As per our knowledge, Prof. D.N.Besekar,
Dept. of Computer Science, Shri. Shivaji College of Science,
Akola had proposed a system for recognition of offline
handwritten MODI script Vowels. The challenges of
recognition of handwritten Modi characters are very high due
to the varying writing style of each individual. Many vital
documents with precious information have been written in
Modi and currently, these documents have been stored and
preserved in temples and museums. Over a period of time these
documents will wither away if not given due attention. In this
paper we propose a system for recognition of handwritten
Modi script characters; the proposed method uses Image
processing techniques and algorithms which are described
below.
General Terms
Preprocessing techniques: Gray scaling, Thresholding,
Boundary detection, Thinning, cropping, scaling, Template
generation. Other algorithms used- Average method, otsu
method, Stentiford method, Template-based matching method
To help corporations survive amidst worldwide
quality competition, the authors have focused on the strategic
development of a Higher-Cycled Product Design CAE Model
employing a Highly Reliable CAE Analysis Technology
Component Model. Their efforts are part of principle-based
research aimed at evolving product design and CAE development
processes to ensure better quality assurance. To satisfy the
requirements of developing and producing high quality products
while also reducing costs and shortening development times, the
effectiveness of this model was verified by successfully applying it
to the technological problems of loosening bolts and other
product design bottlenecks at auto manufacturers.
On the surface a packet is a chunk of information
but at the deeper level a packet is one unit of binary data capable
of being transferred through a network. Delivering data packets
for highly dynamic mobile ad hoc networks in a reliable and
timely manner. Driven by this issue, an efficient Position-based
Opportunistic Routing (POR) protocol which takes advantage of
the stateless property of geographic routing. In proactive routing
protocols the route discovery and recovery procedures are time
and energy consuming process. Once the path breaks, data
packets will get lost or be delayed for a long time until the
reconstruction of the route, causing transmission interruption.
but Geographic routing (GR) uses location information to
forward data packets, in a hop-by-hop routing fashion. Greedy
forwarding is used to select next hop forwarder with the largest
positive progress toward the destination while void handling
mechanism is triggered to route around communication voids. No
end-to-end route need to be maintained, leading to GR’s high
efficiency and scalability. In the operation of greedy forwarding,
the neighbour which is relatively far away from the sender is
chosen as the next hop. If the node moves out of the sender’s
coverage area, the transmission will fail. In GPSR (a very famous
geographic routing protocol), the MAC-layer failure feedback is
used to offer the packet another chance to reroute.
The combination of steganography and
cryptography is considered as one of the best security methods
used for message protection, due to this reason, in this paper, a
data hiding system that is based on image steganography and
cryptography is proposed to secure data transfer between the
source and destination. Animated GIF image is chosen as a
carrier file format for the steganography due to a wide use in web
pages and a LSB (Least Significant Bits) algorithm is employed to
hide the message inside the colors of the pixels of an animated
GIF image frames. To increase the security of hiding, each frame
of GIF image is converted to 256 color BMP image and the
palette of them is sorted and reassign each pixels to its new index,
furthermore, the message is encrypted by LZW ( Lempel _
Ziv_Welch) compression algorithm before being hidden in the
image frames. The proposed system was evaluated for
effectiveness and the result shows that, the encryption and
decryption methods used for developing the system make the
security of the proposed system more efficient in securing data
from unauthorized users. The system is therefore, recommended
to be used by the Internet users for establishing a more secure
communication
This paper focuses on the numerous techniques that
have been proposed over the years for metamaterial
characterization. These techniques are categorized into
analytical, field averaging and experimental methods, which
provide various methods to determine the complex permittivity,
complex permeability and refractive index of metamaterials.
Suspended nanoparticles in conventional fluids,
called nanofluids, have been the subject of intensive study
worldwide since pioneering researchers recently discovered the
anomalous thermal behavior of these fluids. The heat transfer from
smaller area is achieved through microchannels. The heat transfer
principle states that maximum heat transfer is achieved in
microchannels with maximum pressure drop across it. In this
research work the experimental and numerical investigation for
the improved heat transfer characteristics of serpentine shaped
microchannel heat sink using Al2O3/water nanofluid is done. The
fluid flow characteristics is also analyzed for the serpentine
shaped micrchannel. The experimental results of the heat
transfer using Al2O3 nanofluid is compared with the numerical
values. The calculations in this work suggest that the best heat
transfer enhancement can be obtained by using a system with an
Al2O3–water nanofluid-cooled micro channel with serpentine
shaped fluid flow
Space-time adaptive processing (STAP) is a signal
processing technique most commonly used in radar systems where
interference is a problem. The radar signal processor is used to
remove the unintentional cluttering effects caused by ground
reflections and echoes due to sea, desert, forest, etc. and intentional
jamming and make the received signal useful. In this paper a new
approach to STAP based on subspace projection has been described
in detail. According to linear algebra and three dimensional
geometry, if we project a range space on to a subspace spanned by
linearly independent vectors, we can suppress data which is
perpendicular to that subspace. In subspace based technique, the
received data is projected on to a subspace which is orthogonal to
clutter subspace to remove the clutter. The probability of target
detection can be find out in order to analyse the performance of the
proposed algorithm. Two existing algorithms, SMI and DPCA are
chosen to do the comparison. while plotting the detection Probability
against SINR , the results obtained are better for subspace technique
than DPCA and SMI. We got the SINR improved for subspace based
technique for same detection probability. The effect of subspace rank
on SINR was also analysed for understanding the computational load
caused by the technique. We also analysed the convergence of the
algorithm by taking plots of SINR against range snapshots.
The Application Programming Interface restricts
the types of queries that the Web service can answer. For
instance, a Web service might provide a method that returns the
books of a given author in fast manner, but it might not provide a
method that returns the authors of a given book. If the user asks
for the author of some specific book, then the Web service cannot
be called – even though the underlying database might have the
preferred piece of information, this scenario is called asymmetry.
This asymmetry is particularly problematic if the service is used
in a Web service orchestration system. In this survey, we propose
to use on-the-fly information extraction (IE).IE used to collect
values, and then the value can be used as parameter Bindings for
the Web service. This survey shows how the information
extraction can be integrated into a Web service orchestration
system. The proposed approach is fully implemented in a
prototype called Search Using Services and Information
Extraction (SUSIE). Real-life data and services are used to
demonstrate the practical viability and good performance of our
approach
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.
Surface Activation of C-sp3 in Boron-Doped Diamond ElectrodeAlejandro Medel
Abstract C-sp2 (graphite) impurities are undesirable in synthetic diamond electrodes (C-sp3), because they can affect the electrochemical response. In this work, we demonstrate that Csp3 surfaces can be activated successfully by applying an anodic current density corresponding to sufficiently high potential where the hydroxyl radicals (●OH) are generated. The
effectiveness of this activation process was verified by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and cyclic voltammetry.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Electrical properties of Ni0.4Mg0.6Fe2O4 ferritesIJERA Editor
Ni0.4Mg0.6Fe2O4 Ceramic samples were prepared by conventional double sintering approach and sintered at 1300oC/4 h. These ferrites are further characterized using X-ray diffractometer. The diffraction study reveals that the present compound shows perfect single phase cubic spinel structure. In addition, the behavior of distinct electrical properties such as dielectric constant (ε'), dielectric loss (ε") and ac-conductivity (ζac) as a function frequency as well as temperature is analyzed using the LCR controller.
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.
A study of micro structural, magnetic and electrical properties of La-Co-Sm n...IJECEIAES
A Lanthanum (La 3+ ) doped Samarium-Cobalt nanoferrites (La_x,Co_0.2,Sm_0.2,Fe_(2-x) O_4, where x=0.0,0.5,1.0) have been synthesized by sol-gel method in citrate media. Obtained spinal ferrites micro structure properties have been investigated by XRD, FTIR, SEM-EDX, and TEM-SAED techniques. All the samples are nano in size with significant hysteresis. Micro structural analysis by XRD confirms the obtained samples showing the single phase cubic spinal structures with an average crystal size found from 12 nm to 25 nm, while the average particles sizes identified from TEM analysis are ranging from 21.5nm-26.8 nm (~23.4nm) and from 20.5 nm to 28(~26.4nm) nm for x=0.5,1.0. The lattice parameter found to be a= 8.402, 8.423, 8.467Å for the respective values of x= 0.0, 0.05, and 1.0. Electrical properties show increase in dc resistivity with increase in La ion concentration. Finally, it was concluded that the doping of Lanthanum ion (La 3+ ) in the ferrites structure is found to influencing the structural and electrical properties without scarifying the ferromagnetic character.
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.
Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1M...Scientific Review SR
The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.
Similar to ELECTRODEPOSITION OF SILVER NANOPARTICLES ON CARBON SPHERE SURFACES BY PULSE CURRENT (20)
Recent joint surgery studies reveal increased
revisions and resurfacing of the metal on metal hip joints. Metal
on metal hip implants were developed more than thirty years ago
and their application has been refined because of availability of
advanced manufacturing techniques and partly by advancements
in material science and engineering. Development of composite
materials may provide greater durability to metal-on-metal hip
implants .This review article is a study of the latest literature of
metal-on-metal hip implants and its various modeling techniques.
Numbers of methods are used for convergence and numerical
solution to investigate the performance of metal-on-metal hip
implant for accurate stable solution. This paper presents analysis
done by various researchers on metal-on-metal hip implants for
wear, lubrication, fatigue, bio-tribo-corrosion, design, toxicity
and resurfacing. After in vivo and in vitro studies, it is found that
all these methods have limitations. There is a need of more
insight for lubrication analysis, geometry of bearings, materials
and input parameters. The information provided in this work is
intended as an aid in the assessment of metal-on-metal hip joints.
Background Hospital contributes significantly tangible and intangible resources on a concurred plan by the scheduling of surgery on the OT list. Postponement decreases efficiency by declining throughput leads to wastage of resources hence burden to the nation. Patients and their family face economic and emotional implication due to the postponement. Postponement rate being a quality indicator controls check mechanism could be developed from the results. Postponement of elective scheduled operations results in inefficient use of the operating room (OR) time on the day of surgery. Inconvenience to patients and families are also caused by postponements. Moreover, the day of surgery (DOS) postponement creates logistic and financial burden associated with extended hospital stay and repetitions of pre-operative preparations to an extent of repetition of investigations in some cases causing escalated costs, wastage of time and reduced income. Methodology A cross-sectional study was done in the operation theaters of a tertiary care hospital in which total ten operation theaters of General Surgery Data of scheduled, performed and postponed surgeries was collected from all the operation theater with effect from March 1st to September 30th, 2018. A questionnaire was developed to find out the reasons for the postponement for all hospital’s stakeholders (surgeons, Anesthetist, Nursing Officer) and they were further evaluated time series analysis of scheduling of Operation Theater for moving average technique. Results Total 958 surgeries were scheduled and 772 surgeries performed were and 186 surgeries were postponed with a postponement rate of 19.42% in the cardiac surgery department during the study period. Month-wise postponement Rate exponential smoothing of time series data shows the dynamic of operating suits. To test throughput Postponement rate was plotted the postponed surgeries and on regression analysis is in a perfect linear relationship.
Introduction: Postponement of elective scheduled operations results in inefficient use of operating room (OR) time on the day of surgery. Inconvenience to patients and families also caused by postponements. Moreover, day of surgery (DOS) postponement creates logistic and financial burden associated with extended hospital stay and repetitions of pre-operative preparations to an extend of repetition of investigations in some cases causing escalated costs, wastage of time and reduced income. Methodology: A cross sectional study was done in the operation theaters of a tertiary care hospital in which total ten operation theaters of General Surgery Data of scheduled, performed and postponed surgeries was collected from all the operation theater with effect from march 1st to September 30th 2018. A questionnaire was developed to find out the reasons for the postponement for all hospital’s stakeholders (Surgeons, Anesthetist, Nursing officer) and they were further evaluated Time series analysis of scheduling of Operation Theater for Moving average Technique. Results: total 2,466 surgeries were scheduled and 1,980 surgeries were performed and 486 surgeries were postponed in the general surgery department during the study period. Month wise postponement forecast was in accordance with the performed surgeries and on regression analysis postponed surgeries were in perfect linear relationship with the postponement Rate.
In the present paper the experimental study of
Nanotechnology involves high cost for Lab set-up and the
experimentation processes were also slow. Attempt has also
been made to discuss the contributions towards the societal
change in the present convergence of Nano-systems and
information technologies. one cannot rely on experimental
nanotechnology alone. As such, the Computer- simulations and
modeling are one of the foundations of computational
nanotechnology. The computer modeling and simulations
were also referred as computational experimentations. The
accuracy of such Computational nano-technology based
experiment generally depends on the accuracy of the following
things: Intermolecular interaction, Numerical models and
Simulation schemes used. The essence of nanotechnology is
therefore size and control because of the diversity of
applications the plural term nanotechnology is preferred by
some nevertheless they all share the common feature of control
at the nanometer scale the latter focusing on the observation
and study of phenomena at the nanometer scale. In this paper,
a brief study of Computer-Simulation techniques as well as
some Experimental result
Solar cell absorber Kesterite- type Cu2ZnSnS4 (CZTS) thin films have been prepared by Chemical Bath Deposition (CBD). UV–vis absorption spectra measurement indicated that the band gap of as-synthesized CZTS was about1.68 eV, which was near the optimum value for photovoltaic solar conversion in a single-band-gap device. The polycrystalline CZTS thin films with kieserite crystal structure have been obtained by XRD. The average of crystalline size of CZTS is 27 nm
Multilevel inverters play a crucial part in the
areas of high and medium voltage applications. Among the three
main multilevel inverters used, the capacitor clamped multilevel
inverter(CCMLI) has advantage with respect to voltage
redundancies. This work proposes a switching pattern to improve
the performance of chosen H-bridge type CCMLI over
conventional CCMLI. The PWM technique used in this work is
Phase Opposition Disposition PWM(PODPWM). The
performance of proposed H-bridge type CCMLI is verified
through MATLAB-Simulink based simulation. It has been
observed that the THD is low in chosen CCMLI compared to
conventional CCMLI.
- In this paper, we introduce a practical mechanism of
compressing a binary phase code modulation (BPCM) signal
according to Barker code with 13 chips in presence of additive
white Gaussian noise (AWGN) by using a digital matched filter
(DMF) corresponding to time domain convolution algorithm of
input and reference signals using Cyclone II EP2C70F896C6
FPGA from ALTERA placed on education and development
board DE2-70 with the following parameters: frequency of
BPCM signal fIF=2 MHz, sampling frequency
f MHz SAM 50
,pulse period
T 200s
, pulse width
S 13sc
, chip width
CH 1sc
, compressing factor
KCOM 13
, SNRinp=1/1, 1/2, 1/3, 1/4, 1/5 and processing
gain factor SNRout/SNRinp=11.14 dB.
The results of filter operation are evaluated using a digital
oscilloscope GDS-1052U to display the input and output signals
for different SNRinp.
Flooding is one of the most devastating natural
disasters in Nigeria. The impact of flooding on human activities
cannot be overemphasized. It can threaten human lives, their
property, environment and the economy. Different techniques
exist to manage and analyze the impact of flooding. Some of these
techniques have not been effective in management of flood
disaster. Remote sensing technique presents itself as an effective
and efficient means of managing flood disaster. In this study,
SPOT-10 image was used to perform land cover/ land use
classification of the study area. Advanced Space borne Thermal
Emission and Reflection Radiometer (ASTER) image of 2010 was
used to generate the Digital Elevation Model (DEM). The image
focal statistics were generated using the Spatial Analyst/
Neighborhood/Focal Statistics Tool in ArcMap. The contour map
was produced using the Spatial Analyst/ Surface/ Contour Tools.
The DEM generated from the focal statistics was reclassified into
different risk levels based on variation of elevation values. The
depression in the DEM was filled and used to create the flow
direction map. The flow accumulation map was produced using
the flow direction data as input image. The stream network and
watershed were equally generated and the stream vectorized. The
reclassified DEM, stream network and vectorized land cover
classes were integrated and used to analyze the impact of flood on
the classes. The result shows that 27.86% of the area studied will
be affected at very high risk flood level, 35.63% at high risk,
17.90% at moderate risk, 10.72% at low risk, and 7.89% at no
risk flood level. Built up area class will be mostly affected at very
high risk flood level while farmland will be affected at high risk
flood level. Oshoro, Imhekpeme, and Weppa communities will be
affected at very high risk flood inundation while Ivighe, Uneme,
Igoide and Iviari communities will be at risk at high risk flood
inundation level. It is recommended among others that buildings
that fall within the “Very High Risk” area should be identified
and occupants possibly relocated to other areas such as the “No
Risk” area.
Without water, humans cannot live. Since time began,
we have lived by the water and vast tracts of waterless land have
been abandoned as it is too difficult to inhabit. At any given
moment, the earth’s atmosphere contains 4,000 cubic miles of
water, which is just 0.000012% of the 344 million cubic miles of
water on earth. Nature maintains this ratio via evaporation and
condensation, irrespective of the activities of man.
There is a certain need for an alternative to solve the water
scarcity. Obtaining water from the atmosphere is nothing new -
since the beginning of time, nature’s continuous hydrologic cycle
of evaporation and condensation in the form of rain or snow has
been the sole source and means of regenerating wholesome water
for all forms of life on earth.
An effective method to generate water is by the separation of
moisture present in air by condensation. In this study, the water
present in air is condensed on the surface of a container and then
collected in an external jacket provided on the container.
Insulations are provided to optimize the inner temperature of the
container.
The method is although uncommon but has certain advantages
which make it a success. The process is economical and does not
require a lot of utilities. It also helps in further reducing the
carbon footprint.
In every moment of functioning the Li-Ion
battery must provide the power required by the user, to have a
long operating life and to and to provide high reliability in
operation. The methods for analysis and testing batteries are
ensuring that all these conditions imposed to the batteries are
met by being tested depending on their intended use.
The success rate of real estate project is
decreasing as there is large scale of project and participation of
entities. It is necessary to study the risk factors involved in the
project. This paper focused on types of risks involved in the
project, risk factors, risk management tools & techniques.
Identification of risk of the project in terms of the total cost of the
project has been divided under Technical, Financial, Sociopolitical
and Statutory cost centers. Large real estate projects
have to tackle the following issues: land acquisition, skilledlabour
shortage, non-availability of skilled project managers, and
mechanization of the construction process to cater to the growing
demands. Non- availability of supporting infrastructure, political
issues like instability of the government leading to regulatory
issues, social issues, marketing forms an important part in these
projects as this is a onetime investment and the purchase cycle is
long , long development period makes the same project be at
different points in the real estate value cycle.
- In the present scenario carbon emission and sand
mining are major concern due to its hazardous effect to
environment and making serious imbalance to the ecosystem.
Various studies have been conducted to reduce severe effect on
environment, using byproducts like copper slag as partial
replacement of fine aggregate. Different researchers have also
revealed numerous uses of copper slag as a replacing agent in
determining the strength of concrete. A comprehensive review of
studies has been presented in this paper for scope of replacement
of fine aggregate from copper slag in concrete
- Security is a concept similar to being cautious
or alert against any danger. Network security is the condition of
being protected against any danger or loss. Thus safety plays a
important role in bank transactions where disclosure of any data
results in big loss. We can define networking as the combination
of two or more computers for the purpose of resource sharing.
Resources here include files, database, emails etc. It is the
protection of these resources from unauthorized users that
brought the development of network security. It is a measure
incorporated to protect data during their transmission and also
to ensure the transmitted is protected and authentic.
Security of online bank transactions here has been
improved by increasing the number of bits while establishing the
SSL connection as well as in RSA asymmetric key encryption
along with SHA1 used for digital signature to authenticate the
user
Background: Septoplasty is a common surgical
procedure performed by otolaryngologists for the correction of
deviated nasal septum. This surgery may be associated with
numerous complications. To minimize these complications,
otolaryngologists frequently pack both nasal cavities with
different types of nasal packing. Despite all its advantages,
nasal packing is also associated with some disadvantages. To
avoid these issues, many surgeons use suturing techniques to
obviate the need for packing after surgery.
Objective: To determine the efficacy and safety of trans-septal
suture technique in preventing complications and decreasing
morbidity after septoplasty in comparison with nasal packing.
Patients and methods: Prospective comparative study. This
study was conducted in the department of Otolaryngology -
Head and Neck Surgery, Rizgary Teaching Hospital - Erbil,
from the 6th of May 2014 to the 30th of November 2014.
A total of 60 patients aged 18-45 years, undergoing septoplasty,
were included in the study. Before surgery, patients were
randomly divided into two equal groups. Group (A) with transseptal
suture technique was compared with group (B) in which
nasal packing with Merocel was done. Postoperative morbidity
in terms of pain, bleeding, postnasal drip, sleep disturbance,
dysphagia, headache and epiphora along with postoperative
complications including septal hematoma, septal perforation,
crustation and synechiae formation were assessed over a follow
up period of four weeks.
Results: Out of 60 patients, 37 patients were males (61.7%)
and 23 patients were females (38.3%). Patients with nasal
packing had significantly more postoperative pain (P<0.05)><0.05). There was no significant difference between
the two groups with respect to nasal bleeding, septal
hematoma, septal perforation, crustation and synechiae
formation.
Conclusion: Septoplasty can be safely performed using transseptal
suturing technique without nasal packing.
The basic reason behind the need to
monitor water quality is to verify whether the examined
water quality is suitable for intended usage or not. This
study is conducted on Al -Shamiya al- sharqi drain in
Diwaniya city in Iraq to make valid assessment for the
level of parameters measured and to realize their effects
on irrigation. In order to assess the drainage water
quality for irrigation purposes with a high accuracy, the
Irrigation Water Quality Index (IWQI) will be examined
and upgraded (integrated with GIS) to make a
classification for drainage water. For this purpose, ten
samples of drainage water were taken from different ten
location of the stuay area. The collected samples were
analyzed chemically for different elements which affect
water quality for irrigation.These elements are :
Calcium(Ca+2), Sodium(Na+
), Magnesium(Mg+2),
Chloride( ), Potassium(K+
), Bicarbonate(HCO3),
Nitrate(NO3), Sulfate( , Phosphate( , Electrical
Conductivity(EC), Total Dissolved Solids (TDS), Total
Suspended Solids (TSS) and pH-values (PH). Sodium
Adsorption Ratio (SAR) and Sodium Content (Na%)
have been also calculated. Results suggest that, the use of
GIS and Water Quality Index (WQI) methods could
provide an extremely interesting as well as efficient tool
to water resource management. The results analysis of
(IWQI) maps confirms that: 52% of the drainage water
in study area falls within the "Low restriction" (LR) and
47%of study area has water with (Moderate
restriction)(MR),While 1% of drainage water in the
study area classified as (Sever restriction) (SR). So, the
drainage water should be used with the soil having high
permeability with some constraints imposed on types of
plant for specified tolerance of salts
The cable-hoisting method and rail cable-lifting
method are widely used in the construction of suspension bridge.
This paper takes a suspension bridge in Hunan as an example,
and expounds the two construction methods, and analyzes their
respective merits and disadvantages.
Baylis-Hillman reaction has been achieved on
different organic motifs but with completion times of three to
six days. Micellar medium of CTAB in water along with the
organic base DABCO has been used to effect the BaylisHillman
reaction on a steroidal nucleus of Withaferin-A for the
first time with different aromatic aldehydes within a day to
synthesize a library of BH adducts (W1a –W14a) and (W1bW14b)
as a mixture of two isomers and W15 as a single
compound. The isomers were separated on column and the
major components were chosen for bio-evaluation. Cytotoxic
activity of the synthesized compounds was screened against a
panel of four cancer cell lines Lung A-549, Breast MCF-7,
Colon HCT-116 and Leukemia THP-1 along with 5-florouracil
and Mitomycin-C as references. All the compounds exhibited
promising activity against screened cell lines and were found to
possess enhaunced activity than parent compound. BH adducts
with aromatic systems having methoxy and nitro groups were
found to be more active.
This paper presents the details on the
experimental investigation carried out to get the desired fresh
properties of the SCC. Tests were performed on various mixtures
to obtain the required SCC. In the present research work we
have replaced 15% of cement with class F fly ash. By varying the
quantity of water and sand the mortar mix was prepared. Later
varying percentage of coarse aggregate was added to the mortar
to obtain the desired SCC.
The batteries used in electric and hybrid vehicles
consists of several cells with voltages between 3.6V battery and
4.2 V in series or parallel combinations of configurations for
obtaining the necessary available voltages in the operation of a
hybrid electric vehicle. How malfunction of a single cell affects
the behavior of the entire battery pack, BMS main function is to
protect individual cells against over-discharge, overload or
overheating. This is done by correct balancing of the cells. In
addition BMS estimates the battery charge status
This project aims at using (PD-MCPWM) Phase
disposition multi carrier pulse width modulation technique to
reduce leakage current in a transformerless cascaded multilevel
inverter for PV systems. Advantages of transformerless PV
inverter topology is as follows, simple structure, low weight and
provides higher efficiency , but however this topology provides a
path for the leakage current to flow through the parasitic
capacitance formed between the PV module and the ground.
Modulation technique reduces leakage current with an added
advantage without adding any extra components.
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ELECTRODEPOSITION OF SILVER NANOPARTICLES ON CARBON SPHERE SURFACES BY PULSE CURRENT
1. International Journal of Technical Research and Applications e-ISSN: 2320-8163,
www.ijtra.com Volume 2, Issue 6 (Nov-Dec 2014), PP. 154-158
154 | P a g e
ELECTRODEPOSITION OF SILVER
NANOPARTICLES ON CARBON SPHERE
SURFACES BY PULSE CURRENT
Manal A. Hassan1*, Zeinab Abdel Hamid1, Nabil Nassif1, Mahmoud rabah2
1
Corrosion Control and Surface Protection Lab, CMRDI
2
Chemical and Electrochemical Treatment Lab, mineral processing Dept. CMRDI
1
nmzmanal@yahoo.com, 1
forzeinab@yahoo.com, 1
nabilnassif01@hotmail.com, 2
mahmoud.rabah@ymail.com
Abstract- This work studied the effect of applying pulse current
(ton=off=1s) on the electrodeposition of silver nanoparticles on
carbon sphere surface as a substrate. The electrolyte is made of 0.1
M KNO3, 0.1 M KCN and 0.01M AgNO3. The pH value has been
adjusted in the alkaline region of 9.1 with the help of K(NO3)
addition. Experiments were carried out at room temperature for
periods up to 12 minutes. The cell is fitted with a mechanical stirrer
to keep the electrolyte in a dynamic state. Product(s) was
characterized with the help of SEM and EDX and field emission.
Results obtained show that silver nanoparticles has successfully
electrodeposited under pulse current conditions with a particle size
of 100–400 nm after 2 minutes. Deposition takes place on certain
accessible sites of the carbon surface of the substrate forming a
monolayer of scattered silver nanoparticles. Formation of macro
particles with larger diameter and multilayer in thickness takes
place with continuous deposition of silver nanoparticles on the
formerly deposited silver. Pulse current helps management of the
monolayer deposition as compared to the steady DC application
with respect to particle diameter and number of layers.
Keywords: Galvanostatic pulse current silver nanoparticles
Homogeneous distribution Electrodeposition.
I. INTRODUCTION
Several techniques had been examined for the synthesis of
nanoparticles [1]. Electroplating of silver has been studied
applying conventional methods of direct current (DC). The pulse
plating technique would be of considerable benefit to the silver
deposition especially in jeweler industries. The main benefits of
using pulse plating were to significantly reduce the consumption
of silver. It also resulting in significant reduction in the
production cost, time as well as improving the quality of the
coatings [2, 3]. Supported nanoparticles were shown to be
important for many applications, including catalysis [4] and
electroanalysis [5]. Mahmoud Rabah reported that silver
nanoparticles were prepared from E-waste by chemical and
electrokinetic process [6]. Nanoparticles of silver can be
synthesized by different methods in solution or in gas phase. In
case it was required to generate particles firmly attached to a
surface, previous methods did not always provide the best
solution. Electrochemical deposition has arisen as a promising
technique to synthesize nanoparticles because of its high
selectivity and cost effectiveness [7]. Several groups have
electrodeposited metallic nanoparticles on various substrates
such as glassy carbon (GC) [8], highly oriented pyrolitic graphite
(HOPG) [9-11], indium doped tin Oxide (ITO) [12, 13] and
others [14]. However, the electrodeposition of narrowly
dispersed distributions of small nanoparticles was described to
be still a challenge. The adhesion of silver nanoparticles to a
surface determined the range of applicable techniques to
characterize the substrate surface such as Scanning Electron
Microscopy (SEM) [8, 14] or Atomic Force
Microscopy/Scanning Tunneling Microscopy (AFM/STM)
[9.10]. In practice however, the resolution of a FESEM is limited
to particles with diameters larger than 6–7 nm and the AFM/
STM. Lateral resolution was affected by the geometry of the tip
so the apparent diameters obtained from an AFM image failed to
represent the dimensions of the deposited particle. Furthermore,
none of these techniques was suitable for high-resolution
structural analysis of small nanoparticles. Transmission Electron
Microscope (TEM) is the ideal tool for studying the
morphological and structural properties of nanoparticles [15].
However, the particles may be supported onto a TEM grid or
additional TEM. Sample preparation could alter the properties of
the electrodeposited particles In some cases, particles had been
removed from the substrate and dissolved by ultra snication to be
deposited again on a TEM grid [9]. Also, some TEM images of
as-electrodeposited nanoparticles have been presented by
Penner's group [10] by transferring thin (10–40 nm) HOPG
flakes froma working electrode onto TEM grids. However, size
distribution and particle density of nanoparticles were studied by
TEM. The authors claimed a new and straightforward approach
by using carbon coated gold TEM grids as substrates for the
electrodeposition of silver nanoparticles. That method enabled to
perform conventional FESEM measurements but also allows us
to correlate TEM and electrochemical information on early
nucleation and growth in a direct manner.
This paper aims to study the effect of applying pulse current on
the catalytic activity of electrodeposited silver nanoparticles on
carbon substrate. Parameters affecting the magnitude and
properties of the deposited nanoparticles of silver such as current
density, time, and the pH value have been investigated.
II. EXPERIMENTAL
A. Materials and Methods
a) Chemicals used in this study were pure grade
chemicals.
Silver nitrate 0.1M solution was prepared in a de-ionized water.
A standard 0.1 M solution of KNO3 and KCN were used to
adjust and control the pH value of the electrolyte at 9.1 and a
complexing agent respectively.
b) The electrolysis cell
It is made of Pyrex glass beaker 250 ml. The cell is fitted with
two holders for fixing the electrodes, a magnetic stirrer, precise
micrometer and voltmeter. The main power is connected to a
sliding resistance. The two electrodes (anode and cathode) were
2. International Journal of Technical Research and Applications e-ISSN: 2320-8163,
www.ijtra.com Volume 2, Issue 6 (Nov-Dec 2014), PP. 154-158
155 | P a g e
made of small sheet measuring 30 x10 x 0.3 mm in thickness.
Electrodes were made of graphite-doped polypropylene. The
carbon electrodes were washed with pure water followed by
acetone prior to use. Fig.1 shows a photograph of the cell
Fig, 1 A photograph of the experimental set-up for pulse
current
B. Description of the electro deposition process
The pH value was adjusted and kept constant at 9.1 with the help
of addition of drops of 0.1M potassium nitrate solution.
Experiments were carried out at room temperature. The working
area of the cathode was 4 cm2
. The two electrodes were
separated by silk screen diaphragm. The cell is fitted with a
separating funnel filled with silver stock solutions. The electro
deposition was carried out under galvanostatic conditions using a
DC power supply unit Model QJ3005.
C. Methods of measurement the characteristics of the
deposited silver
A potentiostate/galvanostate IVIUMSTAT, controlled by
personal computer was used for the voltammetric measurements.
Weight of deposited silver was recorded by a precise electronic
balance. The crystalline structure of silver nanoparticles
electrodeposited on carbon was examined by x-ray diffraction
(Shimadzu XRD-6000). The surface morphology of the silver
nanopartiocles was examined with the help of Philip XL-40FEG
filed emission SEM.
III. RESULTS
Results reveal that the rate of deposition of silver particles at
current density 12 mA dm-2
amounts to 0.515 mg/cm-2
.min and
alleviates to 0.21 and 0.16 mg/cm-2
.min with lower current
density conditions of 6 and 5 Adm-2
respectively. The rate of
deposition linearly relates to the current density value and time
up to 10 minutes.
Fig.2 shows the weight of the deposited silver as a function of
time. It can be seen that the weight deposited increases with time
up to 8 minutes after which it decreases with more time. Fig 3
shows the rate of deposition against time. It is seen that the rate
of deposition of silver nanoparticles as affected by time of
electrodeposition at room temperature. It is seen that the rate
decreases with increasing time up to 12 min whereby a minimum
value is attained (012 mg cm-2
min-1
) with more time, the rate
of deposition is kept more or less the same.
t.me/min
4 6 8 10 12 14 16 18
Wtgain/g
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.010
Fig. 2: relationship between weight gain/gm of deposition of
silver nanoparticles on porous graphite against time/min at
current density 6Adm-2
, room temperature, and pH9.1 under
pulsed condition (Ton=Toff=1sec)
time/min
0 2 4 6 8 10 12 14 16 18
log(rateofdeposition,mg/cm2
/min
0.001
0.01
0.1
1
10
Fig.3 Rate of deposition of Ag as function of time at 6A/dm2
current density, room temp, and pH 9.1 under pulsed
condition (Ton, Toff =1sec)
Fig 4 shows the rate of electro deposition as a function of current
density. It can be seen that the rate of electro deposition of silver
increases with increasing current density value passing through a
maximum at (6Adm-2
). With further increase in current density,
the rate value decreases drastically to reach a minimum value of
(3 mg cm-2
min-1
)
Fig.5 shows the effect of pH value of the silver electrolyte on the
rate of silver electrodeposition at room temperature. It is seen
decreases slightly within the pH range 8.4 – 9.1. With more basic
electrolyte (pH ≥ 9.2 to 9.9, the rate of electrodeposition of silver
exhibits pronounced decrease
current density, Adm-2
2 3 4 5 6 7 8 9
rateofdepositionmg/cm
2
/min
-1
0
1
2
3
4
Fig.4 Rate of deposition of Ag as function of current density
at time 2min ,room temperature and pH 9.1 under pulsed
condition(Ton,Toff =1sec)
3. International Journal of Technical Research and Applications e-ISSN: 2320-8163,
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156 | P a g e
pH
8.2 8.4 8.6 8.8 9.0 9.2 9.4 9.6 9.8 10.0
rateofdeposition,mgcm
-2
min
-1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Fig.5 Rate of deposition of Ag as function of pH at current
density 8 Adm-2
, time 2min ,room temperature and under
pulsed condition(Ton,Toff =1sec)
, duty cycle %
33.3% 50% 66.6%
rateofdeposition,mg/cm
2
/min
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Fig.6 Rate of deposition and duty cycle % (γ). 8 A/dm2
, time
2 min ,room temperature, pH 9.1
Fig.6 shows the rate of electrodeposition of silver as influenced
by the duty cycle percent (γ). It can be seen that the rate curve
displays a parabolic shape with its maximum of 0.8 mg/cm2
/ min
while its minimum value amounting to 0.4 mgcm-2
min-1
with (γ)
value of 50%..
Fig.7 shows the strength of adhesion of the deposited silver on
the carbon substrate expressed as the weight removed upon
agitation with water at room temperature. It can be seen that
weight removed of the deposited silver nanoparticles increase
with increasing current density till reach to 5Adm-2
, passing
through that value the rate of deposition decrease to reach 6Adm-
2
then slightly decrease.
c.d.Adm-2
1 2 3 4 5 6 7
weightloss,mg
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Fig.7 Relation between weight loss and current density,
2min., room temperature, pH 9.1 and under pulsed
condition(Ton,Toff =1sec
Fig.8 shows the Anodic cyclic voltammetry curves (CV) of
ethanol oxidation in alkaline solution using Ag on nonporous
carbon surface with various scanning rates (5, 25, 50, and 100)
mVs-1
. It can be seen that the four peaks are displayed at 0.5, 3.7,
6 and 8.2 mA.cm-2
with 0.5, 0.58, 0.69 and 0.80 mV
respectively. Fig. 9 shows the plots of current density peak (I)
against square root of scan rate of Ag/C electrode in KOH+5M
ethanol. It is seen that the current peak value is linearly related to
the scan rate. The slop of the linear relation amounts to
mA/scan rate.
E/mV Vs (SCE)
0.0 0.2 0.4 0.6 0.8
I/mACm
-2
-2
0
2
4
6
8
10
scan rate 5 mVs-1
scan rate 25 mVs-1
scan rate 50 mVs-1
scan rate 100mVs-1
Fig.8: The anodic cyclic voltammetry curves (CV) of
oxidation of ethanol in alkaline solution at Ag/C electrode
(deposited at the optimum conditions) with various scan rate
(5, 25, 50, 100) mVs-1
.
Fig.9: Plots of peak current density (I) against square root of
scan rate f Ag/C electrode in KOH+5M ethanol.
Figure 10 shows the anodic cyclic voltammetry curves (CV) of
oxidation of ethanol (5M) in alkaline solution (1MKOH) at 5
mVs-1
scan rate using porous and nonporous carbon electrodes. It
can be seen that the anodic cyclic voltammetry value displays
more or less the same value of 0.15 mA/cm2
with increasing the
potential up to 0.38 mV. With higher potential > 0.38 mV, the
anodic cyclic voltammetry displays a rapid increase to reach a
peak of 3 mA/cm2
at 0.46 mV with porous graphite electrodes.
The corresponding values obtained with nonporous graphite
electrodes displays a broad maximum of about 1 mA/cm2
at the
same potential. It is worth noting that the standard reduction
potential of (OH) group amounts to +0.8277 mA [R].
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157 | P a g e
E/mV Vs (SCE)
0.0 0.1 0.2 0.3 0.4 0.5
i/mACm
-2
-2
-1
0
1
2
3
4
(a)
(b)
Fig. 10: Anodic cyclic voltammetry curves (CV) of
oxidation of ethanol (5M) in alkaline solution (1MKOH)
at 5 mVs-1
scan rate using different electrodes: (standard
(OH) oxidation +0.8277 mA/cm2
[R])
a) Silver/ porous graphite electrode.
b) Silver/ non-porous graphite electrode
E/mV Vs (SCE)
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
i/mACm
-2
-2
0
2
4
6
8
a) Ag /non porous 1MKOH
b) Ag /non porous 1MKOH+5M ethanol
c) nonporous graphite electrode in 1MKOH
d) nonporous graphite electrode in 1MKOH+5Methanol
Fig.11: Cyclic volt ammograms at 5 mVs-1
scan rate for
a) Silver / non porous graphite electrode in 1M KOH
solution.
b) Silver / non porous graphite electrode in 1M KOH +5M
ethanol solution.
c) Non porous graphite electrode in 1M KOH solution.
d) Non porous graphite electrode in 1M KOH +5M
ethanol solution
Figure 11 shows the Cyclic voltametry CV of silver
nanoparticles electrodeposited on porous and nonporous carbon
substrate in 1 M KOH. Parallel experiments were carried out in
presence of 5 M ethanol. It is seen that the silver on porous
carbon displays more catalytic effect in oxidizing ethanol as
compared to silver on nonporous substrate. Silver oxidative peak
appeared at 0.47 mV. The catalytic activity becomes very
pronounced with higher potential values >0.6 mV.
Fig 12 shows SEM photograph of the electrodeposited silver on
porous and nonporous carbon substrate. The particle size
amounts to 117 um.
Fig. 12 SEM of silver deposit on graphite-PP substrate,
mag.x 50,000
IV. DISCUSSION
Electrodeposition of silver nanoparticles has its importance from
the fact that the metal is used as a catalyst. Nanoparticles of the
Nobel metal acquire high catalytic activity as compared to the
common regular silver particles. In this context, the method used
in this work, investigated the application of pulse current
technique to help deposition of silver on carbon with a slow rate
to accomplish deposition of fine particles of nano size. Results
revealed that the used silver nitrate solution is a suitable
electrolyte to carry out silver electro deposition. The addition of
potassium nitrate helps to keep the silver solution at constant pH
value of 9.1. The process of deposition takes place according to
the following equation
AgNO3 Ag +
+ NO3
-1
………(1)
Ag+
+ e-
Ag …………….….(2)
Reaction 2 would be enhanced by controlling the potential of the
electrolysis process across the solution bulk and the surface of
the cathode to establish a concentration gradient at the cathode
vicinity. Adjustment of the current density, the concentration of
the silver ions in solution and the temperature promote the
successful deposition of silver in nano size. The use of pulse
current prevails the time enough for silver ions to diffuse through
the established concentration gradient to be available for
deposition. Results given in Figs 2 and 3 are in a good agreement
with this model. The effect of current density (Fig.3) can be
explained in the light of a model which suggested that at low
current density, the rate of silver deposition is low due to
deficiency of electrons (equation 2). With gradual increase in
current density, excessive silver ions are liable to be discharged
and deposited. The maximum rate of deposition takes place with
6 A/dm2. With further increase in current density, rapid
deposition of silver particles takes place with less significant
adhesion forces on the carbon substrate. In other words, the
deposited silver is loose without enough adhesion forces to
cement to the cathode surface and fall down in the bottom of the
electrolyzing cell. The effect of pH (Fig.4) on the rate of silver
deposition revealed that high OH-
groups would inhibit silver ion
diffusion from the solution bulk to the cathode. Results of
Figures 8 and 9 show that silver particles display catalytic
activity to oxidize ethanol. Such activity becomes very
5. International Journal of Technical Research and Applications e-ISSN: 2320-8163,
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158 | P a g e
pronounced with silver on porous graphite substrate as judged
from the increasing value in current density peak value as
compared to the value with silver on nonporous graphite (Fig.
10). This phenomenon finds support from the fact that porous
substrate provide larger surface area of the silver catalyst to help
more catalytic activity. SEM investigations of the silver metal
deposited on graghite-doped PP (mag.x500) supports this model.
Porous graphite provides the silver catalysis with increasing sites
accessible for deposition. Catalytic activity of the deposited
silver is further improved by using pulse current technique for
electro deposition of silver nano particles. A proper time
necessary for diffusion of silver ions and discharging before
deposition seems available in the cathode vicinity. In other
words, silver ions in nanoparticles size are successfully
deposited under pulse current density conditions and room
temperature on sites of the graphite surface. The use of current
density 6 Adm-2
prevail the optimum conditions to deposit silver
in nano size. Higher current density implies that silver ions are
discharged simultaneously and would aggregate to form particles
larger in size. Excessive high current density is not in favor of
nano particles deposition as particles of silver will deposit in
loose grains falling on the bottom of the electrolyzing cell. It is
worth noting that the applied potential may affect the current
density value (Fig.7). This is legitimate on the basis of the fact
that the power (VA) only suitable for silver ions discharge would
be highly recommended.
V. CONCLUSION
Nano particles of silver have wide range of applications in the
fields of energy, environmental, and medical technologies due to
their unique properties determined primarily by its size,
composition, and structure. Silver nano particles have been of
considerable interest because of their unusual and fascinating
properties. The electrolyte conditions are controlled by addition
of potassium nitrate and potassium cyanide. The optimum
electro deposition conditions for silver in nano size are current
density= 6 Adm-2
, pH 9.1, silver concentration 0.04 N, pulse ton
= t off = 1 at room temperature. Nano particles of silver deposited
successfully on graphite substrate and its catalytic activity
increases when porous graphite demonstrated as a substrate.
Pulse current helps to deposit silver in nano size particles from
silver nitrate at alkaline pH value with higher catalytic activity to
oxidize ethanol.
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