35 results on '"D. Jeyakumar"'
Search Results
2. Shape-tuned, surface-active and support-free silver oxygen reduction electrocatalyst enabled high performance fully non-PGM alkaline fuel cell
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Srinivasan Chandrasekaran, P. Anandha Ganesh, D. Jeyakumar, and A. N. Prakrthi
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Tafel equation ,Alkaline fuel cell ,Potassium hydroxide ,Materials science ,Ion exchange ,Reducing agent ,General Chemical Engineering ,Limiting current ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,0210 nano-technology - Abstract
Exploring non-platinum group metal (n-PGM) based efficient oxygen reduction reaction (ORR) electro-catalysts is highly important for realizing advancement in sustainable next generation-alkaline anion exchange membrane fuel cells (AAEMFCs). Herein, we demonstrate a new “hierarchical shape tuning approach” for the synthesis of controlled sized and shaped non-PGM based Ag ORR electro-catalysts with surface active nano-islands. Hierarchical shapes ranging from spherical (S-AgNs), worm-in-sphere, sphere-in-worm and vermiform (worm-like) Ag nanostructures (V-AgNs) were obtained by precisely varying the ratios of capping agent to dual reducing agents in water at ambient conditions. Compared to S-AgNs, V-AgNs revealed a higher mass normalized ORR Tafel activity (0.303 A mgAg−1 at 0.9 V), onset (1.06 V) and half wave (0.78 V) potentials and higher retention of limiting current density (>88%) after 5000 cycles in 0.5 M potassium hydroxide (KOH) solution attributable to their unique worm like morphology with surface active nano-islands and support free-nature enabled better catalyst utilization. In a fully “non-PGM AAEMFC” (n-PAAEMFC), V-AgNs exhibited the highest fuel cell activity of 115.6 mW cm−2 and stable short-term durability (∼240 h) compared to S-AgNs (41.3 mW cm−2) and previously reported fully n-PAAEMFCs indicating their potential use in next-generation alkaline fuel cells.
- Published
- 2021
3. Drilling Performances of Kenaf Fibre/Steel Mesh Reinforced Hybrid Epoxy Composites
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P. D. Jeyakumar, A. Arockia Julias, M. Thirumurugan, S. Mohamed Fahad, and K. Jamesha Ibrahim
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Materials science ,biology ,Drill ,Delamination ,Drilling ,Epoxy ,Fibre-reinforced plastic ,biology.organism_classification ,Kenaf ,Machining ,visual_art ,visual_art.visual_art_medium ,Fiber ,Composite material - Abstract
Drilling is one of the important machining operations in polymer matrix composites, which is used to join the polymer composites temporarily. The fiber reinforced polymer composites are widely used in automobile and aerospace fields in which the polymer composites are to be joined with similar or dissimilar materials. The present work focuses on the effects drilling parameters (speed and drill diameter) on kenaf fiber/steel wire mesh hybrid epoxy composites. To obtain the better mechanical properties, the hybrid composites are designed in such way that two layers of kenaf fiber and one layer of steel wire mesh reinforced in epoxy resin matrix. Delaminations, fiber pullout, and cracks are observed in microscopic examinations. Two different parameters of drilling speed and drill diameters are varied to cognizance the mechanism of delamination. The acceptable quality level of drilled holes was measured using toolmakers microscope through by calculating the circularity of drilled holes.
- Published
- 2021
4. Solid-State Planar Reference Electrode With Ion-Selective Electrodes for Clinical Diagnosis
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N. Prabu, D. Jeyakumar, R. Kalidoss, and A. Sivantha Raja
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Materials science ,Thiocyanate ,Potassium ,Sodium ,Inorganic chemistry ,technology, industry, and agriculture ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Reference electrode ,0104 chemical sciences ,chemistry.chemical_compound ,Membrane ,chemistry ,Electrode ,Electrical and Electronic Engineering ,0210 nano-technology ,Instrumentation ,Potassium tetraphenylborate - Abstract
A solid-state planar reference electrode (SSPRE) was fabricated and evaluated using polymer membrane, comprising polyvinyl chloride-co-polyvinyl acetate, nitrophenyl octyl ether as plasticizer, and potassium tetraphenylborate as anion blocker, and was used for the fabrication of SSPRE. Screen-printed Ag/AgCl electrode was used as the base electrode for the fabrication of SSPRE and was evaluated in background electrolyte solutions containing KNO3/KCl and was observed that there was no significant potential dependence on anions present in the background electrolyte. Furthermore, SSPRE was tested using a series of cations and anions in solution and varying pH of the background electrolyte with respect to commercial Ag/AgCl with 0.1 M KCl reference electrode. It was noted that the SSPRE provided stable potential by tuning the design of the screen-printed electrodes and the membrane potential. The reference potential does not differ in various background electrolyte solutions, except thiocyanate, which gave a negative shift at high concentration, ca. 0.1 M. Furthermore, the SSPRE was integrated with screen-printed potassium and sodium ion-selective electrodes, and was tested, and the performance was evaluated.
- Published
- 2018
5. A Facile Strategy for the Synthesis of Flower-Like Structures with Enhanced Nano-Porous Surfaces
- Author
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D. Jeyakumar and P. Anandha Ganesh
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Nano porous ,Materials science ,020209 energy ,Flower like ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,0210 nano-technology ,Instrumentation - Published
- 2018
6. Hierarchical approach of mitigating carbon influence in nano-porous electro-catalyst with unique surface islands for efficient methanol resistive oxygen reduction
- Author
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D. Jeyakumar and P. Anandha Ganesh
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Resistive touchscreen ,Materials science ,Aqueous solution ,General Chemical Engineering ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Durability ,Oxygen reduction ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Direct methanol fuel cell ,chemistry ,Chemical engineering ,Electrochemistry ,Methanol ,0210 nano-technology ,Carbon - Abstract
For the first time, we report a facile one pot aqueous method for support-free Pd85Pt15 nano-porous structures (NPoS) synthesis from PdMn nano-alloys at ambient conditions. A hierarchical approach was successfully employed through a simple “self-settlement” process with descending amounts of carbon to carbon-free electro-catalysts to improve catalyst utilization and avoid carbon degradation during fuel cell operating conditions. Pd85Pt15 NPoS exhibits enhanced methanol resistive oxygen reduction reaction (ORR) activity owing to the presence of highly active and unique surface PdPt islands compared to HiSPEC Pt/C catalysts. Accelerated durability tests of the support-free PdPt NPoS show enhanced durability in harsh acidic environment (1.0 N H2SO4) compared to HiSPEC Pt/C and DOE 2017–2020 durability target. Preliminary direct methanol fuel cell studies using hierarchically derived Pd85Pt15 NPoS variants were performed at ultra-low Pt content. The effects of carbon content and catalyst layer thickness on fuel cell activities are well discussed.
- Published
- 2018
7. Synthesis of Porphyrin-Appended Poly(fluorene-alt -triphenylamine)s: Effect of Appending Groups on Optical and Electrochemical Properties
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Veeman Sannasi and D. Jeyakumar
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Photoluminescence ,Materials science ,Uv vis absorption ,02 engineering and technology ,General Chemistry ,Fluorene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Photochemistry ,Triphenylamine ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Dicyanomethane ,0210 nano-technology - Published
- 2018
8. Effect of appended porphyrin in poly(fluorene-alt-benzothiadiazole): synthesis, characterization, physico-chemical and electrochemical studies
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D. Jeyakumar and Veeman Sannasi
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chemistry.chemical_classification ,Photoluminescence ,Materials science ,Polymers and Plastics ,Carbazole ,02 engineering and technology ,General Chemistry ,Polymer ,Fluorene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,Gel permeation chromatography ,chemistry.chemical_compound ,chemistry ,Polymerization ,Materials Chemistry ,Copolymer ,0210 nano-technology - Abstract
Poly(fluorene-alt-benzothiadiazole) having 5 and 10% equivalent meso-tetraphenylporphyrin (m-MTPCC) linked through oxyethylene spacer in carbazole (P2, P3) and the parent poly(9,9-di-hexylfluorene-alt-2,1,3-benzothiadiazole) (P1) were synthesized using Suzuki polymerization reaction. These polymers were characterized using FT-IR, 1H NMR, TGA and gel permeation chromatography. The synthesized polymers are soluble in common organic solvents and are found to be thermally stable. Weight average molecular weights of the polymers were 51.895, 71.224 and 34.789 kDa for P1, P2 and P3, respectively. These copolymers (P2 and P3) shows absorption maxima at around 320, 422, 452 nm and emission maxima at 540 nm in solution, whereas in film state, these polymers (P2 and P3) shows absorption maxima at around 322, 422, 466 and 554 nm and emission at around 539, 654 and 718 nm. The photoluminescence emission at 648 and 720 nm when excited at 320 nm shows that energy transfer from polymer backbone to porphyrin. Surface morphology, optical absorption and emission properties of these polymers with PCBM were also studied. Electrochemical characterization of these polymers shows deep HOMO levels for P2 and P3 when compared with parent polymer and the details are reported.
- Published
- 2017
9. Enhancing the Efficiency of DSSCs by the Modification of TiO 2 Photoanodes using N, F and S, co-doped Graphene Quantum Dots
- Author
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Sumana Kundu, Amitava Patra, Gopalraman Anantharaj, P. Sarojinijeeva, Pitchai Ragupathy, G. Saritha, Sambandam Anandan, R. Karthick, K. Vijayamohanan Pillai, Rajesh Bera, D. Jeyakumar, and M. Selvaraj
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Photoluminescence ,Materials science ,business.industry ,Graphene ,General Chemical Engineering ,Fermi level ,Doping ,Energy conversion efficiency ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Dye-sensitized solar cell ,symbols.namesake ,law ,Quantum dot ,Electrochemistry ,symbols ,Optoelectronics ,0210 nano-technology ,business - Abstract
We report an enhanced power conversion efficiency (PCE) of 11.7% ± 0.2 and a fill factor (FF) of 71% for dye-sensitized solar cells (DSSC) with an active area of 0.16 cm2 after modifying the TiO2photoanode with size-selective (ca. 2 nm) N,F,S-codoped graphene quantum dots (NFS-GQDs) that exhibit a photoluminescence quantum yield (PLQY) of 70%. An upward shift in the Fermi level has been observed, perhaps responsible for the improved performance along with the possibility of preventing the back electron transfer from TiO2. Mott Schottky analysis indicates a shift (52 mV)in the flat band potential, which is directly related to the Voc of the system. Detailed characterization (IPCE, TCSPC etc) indicates the important role of hetero atoms in facilitating the enhanced performance. Thus, our results suggest that the incorporation of size controlled, hetero atom doped GQDs can enhance the efficiency of DSSCs enabling more opto-electronic applications.
- Published
- 2017
10. ESTIMATION AND VALIDATION OF INTERFACIAL HEAT TRANSFER COEFFICIENT DURING SOLIDIFICATION OF SPHERICAL SHAPED ALUMINUM ALLOY (AL 6061) CASTING USING INVERSE CONTROL VOLUME TECHNIQUE
- Author
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L. Anna Gowsalya, R. Rajaraman, Ramalingam Velraj, and P. D. Jeyakumar
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Materials science ,Alloy ,General Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,Fluid mechanics ,Heat transfer coefficient ,engineering.material ,Volume (thermodynamics) ,chemistry ,Casting (metalworking) ,Aluminium ,Mass transfer ,engineering ,General Materials Science ,Composite material ,Thermal fluids - Published
- 2019
11. Synthesis and characterization of polyphenylene vinylenes having m-terphenyl group: comparison of their optical properties
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D. Jeyakumar and Veeman Sannasi
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chemistry.chemical_classification ,Materials science ,Photoluminescence ,Polymers and Plastics ,General Chemical Engineering ,Dispersity ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Gel permeation chromatography ,chemistry.chemical_compound ,chemistry ,Polymerization ,Phenylene ,Terphenyl ,Polymer chemistry ,Materials Chemistry ,Copolymer ,0210 nano-technology - Abstract
A series of alternate block copolymers of polyphenylene vinylenes that have 1,3-dioctyloxy phenylene in the center of kinked m-terphenyl group as one of the building blocks with either one of the aromatic groups, viz., 1,4-dioctyloxy benzene, 4,6-dioctyloxy benzene and 4,4′-dioctyloxy biphenyl, was synthesized through Heck polymerization. These alternate block copolymers, viz., poly(2,5-bis(octyloxy)phenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P1), poly(2,4-bis(octyloxy)phenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P2) and poly(4,4′-bis(octyloxy-3,3′-biphenylene vinylene alt 4′,6′-bis(octyloxy)-1,1′:3′,1″-terphenylene) (P3), were characterized for their thermal and optical properties. The synthesized polymers had good solubility in organic solvents and were stable up to 350 °C. The molecular weights of the synthesized polymers were in the range 4370–10,900 Da with polydispersity range 1.52–1.65, which were measured by the gel permeation chromatography technique. The optical properties of these polymers showed absorptions in solution at around 400, 329, and 345 nm for P1, P2, and P3 polymers, respectively. The photoluminescence emission maxima of the polymers were at around 461 nm with a shoulder 439 and 424 nm for P1, P2, and P3, respectively. Photoluminescence emission of films of these polymers showed minimum redshift (20 nm) when compared with spectra of their solutions. The optical and photoluminescence emission properties of these polymers were found to vary on the backbone structure.
- Published
- 2016
12. Highly transparent flexible polydimethylsiloxane films - a promising candidate for optoelectronic devices
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Dhanapalan Shanmuga sundar, C. Sanjeeviraja, D. Jeyakumar, and Avaninathan Sivanantha Raja
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Materials science ,Polymers and Plastics ,Young's modulus ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,symbols.namesake ,chemistry.chemical_compound ,Ultimate tensile strength ,Materials Chemistry ,Transmittance ,Composite material ,chemistry.chemical_classification ,Polydimethylsiloxane ,business.industry ,Organic Chemistry ,Polymer ,Molar absorptivity ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Siloxane ,symbols ,Optoelectronics ,0210 nano-technology ,business ,Refractive index - Abstract
In the present work, a siloxane based flexible substrate for optoelectronic applications with improved flexibility and high temperature withstanding capacity has been fabricated and the details are reported. The structural and optical properties of the substrate were characterized and the optical transparency is found to be about 90% − 95% in the visible region. The substrate withstands temperatures up to 300 °C without significant degradation and has a low thermal coefficient of expansion. Fourier transform infrared spectral data show the materials in the prepared substrate and SEM studies show the surface and cross-sectional characteristics of the substrate. It has good mechanical strength, can withstand a high breaking load of 7 N, has a average tensile strength of 48.86 MPa and high average tensile modulus of 127.32 and also possesses excellent surface smoothness and resistance to both chemical and moisture with better rigidity; it will be a long lasting alternative for flexible plastic substrates. The optical characteristics such as refractive index (n) and extinction coefficient (k) are also reported. © 2016 Society of Chemical Industry
- Published
- 2016
13. Synthesis and characterization of transparent and flexible polymer clay substrate for OLEDs
- Author
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C. Sanjeeviraja, D. Jeyakumar, A. Sivanantharaja, and D. Shanmuga Sundar
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Materials science ,business.industry ,Visible light communication ,02 engineering and technology ,Substrate (printing) ,Flexible organic light-emitting diode ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Flexible display ,Transmittance ,OLED ,engineering ,Optoelectronics ,Saponite ,0210 nano-technology ,business ,Refractive index - Abstract
Organic Light Emitting Diode (OLED) has major applications in the field of displays, lighting and visible light communication. Due to the advantages of low cost, light weight, low power and high efficiency, flexible organic light emitting diode have attracted the interest of researchers all over the World. Flexible OLEDs are considered to be the best suitable candidate for next generation lighting devices. In this research, a new flexible and transparent substrate with an average transmittance of 60-70% in the visible region (300-700nm) is synthesized with the help of organic materials such as tetraphenylphosphonium modified lithium saponite (TPP-LiSA), Synthetic Saponite (SA) and N, N-dimethylformamide (DMF). The as-synthesized substrate exhibits refractive index as close as glass which makes this substrate to be used for flexible displays. Characteristics such as extinction coefficient (k), absorption of the synthesized substrate are also calculated.
- Published
- 2016
14. A kish graphitic lithium-insertion anode material obtained from non-biodegradable plastic waste
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T. Prem Kumar, D. Jeyakumar, T. Sri Devi Kumari, Adriel Jebin Jacob Jebaraj, and T. Antony Raj
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Materials science ,Waste management ,Carbonization ,Precipitation (chemistry) ,020209 energy ,Mechanical Engineering ,chemistry.chemical_element ,02 engineering and technology ,Building and Construction ,Pollution ,Industrial and Manufacturing Engineering ,Lithium-ion battery ,Anode ,General Energy ,chemistry ,Chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Lithium ,Graphite ,Electrical and Electronic Engineering ,Dissolution ,Carbon ,Civil and Structural Engineering - Abstract
Graphitic carbon continues to dominate as the choice anode material in lithium-ion batteries despite its theoretical specific capacity of 372 mAhg −1 . Tailored forms of graphite with higher practical capacities should, therefore, be of interest to the industry. This paper reports the production of a kish graphitic anode material from polyvinyl chloride by simultaneous carbonization of the polymer and dissolution of the resulting carbon in an iron melt to produce a supersaturated solution of carbon in iron, and subsequent precipitation of the carbon as graphite upon cooling. Our study presents a process for converting non-biodegradable plastic wastes that litter our surroundings into a technologically useful product. The new material exhibits a first-cycle reversible capacity of 444 mAhg −1 and sustains at least 200 cycles at C/10 rate before its capacity drops below 372 mAhg −1 .
- Published
- 2016
15. Performance of cross-linked polymers based gel electrolyte in the fabrication of quasi-solid state dye-sensitized solar cells
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A. Arulraj, P. Anbarasu, K. Rajendran, V. Sannasi, M. Kesavan, D. Jeyakumar, and Mohan Ramesh
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010302 applied physics ,chemistry.chemical_classification ,Acrylate ,Materials science ,Mechanical Engineering ,Cross-link ,technology, industry, and agriculture ,Ether ,02 engineering and technology ,Polymer ,Electrolyte ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,chemistry.chemical_compound ,Dye-sensitized solar cell ,chemistry ,Chemical engineering ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,0210 nano-technology ,Quasi-solid ,Ethylene glycol - Abstract
Cross-linked polymer (CLP) composed of poly(ethylene glycol) methyl ether acrylate and poly(ethylene glycol) diacrylate has been used in synthesizing gel electrolyte. A set of electrolyte samples was synthesized using gel casting method by varying the weight percentage ratio of cross-linked polymers from 2–14 % in an incremental order (2 %) with respect to poly (ethylene oxide) (PEO) and evaluated its performance by employing in the fabrication of dye-sensitized solar cells. The synthesized polymer was subjected to different analytical techniques such as NMR, TGA, DSC, GPC, and FTIR to confirm the materials. The molecular weight of the CLP has been measured using GPC and the obtained value is found to be 3.655 KDa with polydispersity of 1.94. The CLP-PEO gel electrolyte with 10 % weight ratio has obtained the highest ionic conductivity of 3.07 × 10−6 S/cm−1 at room temperature and best photo-conversion efficiency of 5.1 % was achieved for the same.
- Published
- 2018
- Full Text
- View/download PDF
16. Fabrication of Stable Dye Sensitized Solar Cell with Gel electrolytes Using Poly(ethylene oxide)-Poly(ethylene glycol)
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D. Jeyakumar, M. Selvaraj, James Joseph, and Gopalraman Anantharaj
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chemistry.chemical_classification ,Materials science ,Ethylene oxide ,General Chemical Engineering ,Inorganic chemistry ,Iodide ,technology, industry, and agriculture ,Electrolyte ,Dielectric spectroscopy ,Dye-sensitized solar cell ,chemistry.chemical_compound ,chemistry ,Electrochemistry ,Ionic conductivity ,Triiodide ,Ethylene glycol ,Nuclear chemistry - Abstract
Fabrication of quasi solid state dye sensitized solar cell with a stable gel electrolyte employing poly(ethylene oxide) (PEO)-poly(ethylene glycol) (PEG) is reported in this paper. PEO-PEG with either one of alkali iodides (LiI or NaI or KI), 1,2-dimethyl-3-propyl imidazolium iodide (DMPI), 4-tertbutylpyridine (TBP) and iodine in acetonitrile were used for the gel electrolyte preparation. The ionic conductivity and the triiodide diffusion coefficient of the gel electrolytes were measured by Electrochemical Impedance Spectroscopy. The photoconversion efficiency of gel state DSSC with NaI was found to be 5.4% at 100 mW/cm 2 with AM 1.5 Gfilter. When nanocrystalline TiO 2 was used as the filler in the gel electrolyte, the photoconversion efficiency was found to be increased up to 6.3%. The quasi solid state DSSC retained its initial value for 600 hours aging under ambient conditions.
- Published
- 2015
17. Synthetic functionalized terpolymeric resin for the removal of hazardous metal ions: synthesis, characterization and batch separation analysis
- Author
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D. Jeyakumar, Raja S. Azarudeen, Marimuthu Thirumarimurugan, Mohamed A. Riswan Ahamed, and N. Prabu
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Thermogravimetric analysis ,Aqueous solution ,Materials science ,Polymers and Plastics ,Synthetic resin ,Ion exchange ,Metal ions in aqueous solution ,Inorganic chemistry ,technology, industry, and agriculture ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Nitroaniline ,Adsorption ,stomatognathic system ,020401 chemical engineering ,Organic chemistry ,Thermal stability ,0204 chemical engineering ,0210 nano-technology - Abstract
An effectual functionalized synthetic resin involving anthranilic acid/4-nitroaniline/formaldehyde was synthesized for the detoxification of hazardous metal ions. The resin was characterized by Fourier transform infrared, 1H, and 13C nuclear magnetic resonance spectroscopy, and its morphology was established through scanning electron microscope and X-ray diffraction. The resin was analyzed by thermogravimetric analysis to assess the thermal stability, in which the resin could be used in high temperature aqueous solutions for the elimination of harmful metal ions. The ion-exchange property of the resin was evaluated by batch technique for specific metal ions viz. Fe3+, Co2+, Ni2+, Cu2+, Zn2+, and Pb2+. The study was extended to three variations such as effect of metal ion uptake in the presence of various electrolytes in different concentrations, effect of pH, and effect of contact time. The outcome proved that the resin can be used as a strong cation-exchanger to remove various metal ions from the solutions. The resin could be regenerated and reused with quantitative recovery of metal ions for few cycles. On comparison with the earlier reported resins, the synthesized resin has found excellent capability of metal ion recovery. The resin possesses an utmost ion-exchange capacity, which is in good harmony with isotherm models and kinetics. Copyright © 2015 John Wiley & Sons, Ltd.
- Published
- 2015
18. White light emission in alkali metal ion co-doped single host lattice phosphor Sr3B2O6:Ce3+,Eu2+,A+ [A=Li, Na and K]
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D. Jeyakumar, Paulraj Arunkumar, S. Sekar, and Narayanan Lakshminarasimhan
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Diffraction ,Materials science ,Photoluminescence ,Infrared ,Process Chemistry and Technology ,Analytical chemistry ,Phosphor ,Alkali metal ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,Materials Chemistry ,Ceramics and Composites ,Diffuse reflection ,Spectroscopy - Abstract
White light emitting alkali metal ion co-doped single host lattice phosphors Sr 2.955 B 2 O 6 :0.02Ce 3+ , 0.005Eu 2+ , 0.02A + [A=Li, Na and K] were synthesized by high temperature solid state reaction. The synthesized phosphors were characterized by powder X-ray diffraction and Fourier transform infrared spectroscopic techniques. The optical properties were studied using diffuse reflectance UV–vis reflectance spectroscopy and photoluminescence (PL) spectroscopy. The role of Ce 3+ as a sensitizer of Eu 2+ was found from PL excitation results. The PL white light emission depends on the nature of co-doped alkali metal ion charge compensator.
- Published
- 2015
19. Synthesis and optical properties of poly(2,7-(9,9-dihexylfluorene)-3,3′(4,4′-dialkoxybiphenyl))
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Tini P. Jose, D. Jeyakumar, and V. Sannasi
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chemistry.chemical_classification ,Thermogravimetric analysis ,Photoluminescence ,Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,General Chemical Engineering ,General Chemistry ,Polymer ,Gel permeation chromatography ,chemistry ,Chemical engineering ,Polymer chemistry ,Materials Chemistry ,Thin film ,Glass transition ,Alkyl - Abstract
Five new polymers were synthesized by Suzuki coupling reaction using 9,9-dihexylfluorene-2,7-diboronic acid and 3,3′-dibromo-4,4′-dialkoxybiphenyl as the starting materials. The synthesized alternating copolymers were characterized using gel permeation chromatography, 1H and 13C NMR, FT-IR, optical absorption and emission spectroscopic techniques. The thermal behavior of these polymers was analyzed using thermal gravimetric analysis and temperature modulated differential scanning calorimetric studies. The thermal studies show all the polymers were stable up to 300 °C and the glass transition temperature depends on the alkyl chain length. All the polymers have absorption around 330 nm in solution as well as in film, whereas the polymers have emission around 390 nm in both solution and film. Absorption and emission properties of the synthesized materials are not significantly different in solution, but are dramatically different as thin films at different annealing temperatures.
- Published
- 2014
20. Electrochemical lithium insertion behavior of FeNbO4: Structural relations and in situ conversion into FeNb2O6 during carbon coating
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R. Vinith Gandhi, D. Jeyakumar, G. Kamalanathan, G. Rahul, T. Sri Devi Kumari, Narayanan Lakshminarasimhan, and T. Prem Kumar
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Materials science ,chemistry.chemical_element ,Crystal structure ,engineering.material ,Condensed Matter Physics ,Electrochemistry ,Anode ,Crystallography ,chemistry ,Coating ,Chemical engineering ,engineering ,General Materials Science ,Orthorhombic crystal system ,Lithium ,Powder diffraction ,Monoclinic crystal system - Abstract
Electrochemical properties of FeNbO 4 as a lithium insertion anode material were studied with a view to understand structure–property relationships. Orthorhombic and monoclinic polymorphs of FeNbO 4 were synthesized and characterized by powder X-ray diffraction and laser Raman spectroscopy. Possible redox reactions, as deciphered from cyclic voltammograms, suggest the structural similarity between orthorhombic and monoclinic polymorphs upon lithium insertion. A coating of carbon led to a remarkable improvement in the electrochemical performance of monoclinic FeNbO 4 . The coated material exhibited an average reversible capacity of 125.5 mAh g −1 . The material also sustained hundreds of charge/discharge cycles and exhibited good rate capability. Upon coating with carbon, the monoclinic FeNbO 4 transformed into FeNb 2 O 6 . The conversion and stability were confirmed by powder XRD and laser Raman studies of carbon-coated material before and after 450 cycles. The in situ conversion of FeNbO 4 into FeNb 2 O 6 during carbon coating was further supported by EPR studies in which the absence of signal for the carbon-coated material indicated conversion of Fe 3+ to Fe 2+ . Our study reveals the possibility of exploring potential materials in the Fe–Nb–O system and enhancing their performance as anode materials for lithium-ion batteries.
- Published
- 2014
21. One pot aqueous synthesis of nanoporous Au85Pt15 material with surface bound Pt islands: an efficient methanol tolerant ORR catalyst
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D. Jeyakumar and P. Anandha Ganesh
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Materials science ,Aqueous solution ,Nanoporous ,chemistry.chemical_element ,Nanotechnology ,Electrochemistry ,Catalysis ,Anode ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Galvanic cell ,General Materials Science ,Methanol ,Platinum - Abstract
For the first time, we are reporting the synthesis of Au100-xPtx nanoporous materials in the size range of 7-10 nm through the galvanic replacement of Ag by Pt from Au100-xAg2x spherical nano-alloys (x = 20, 15, 10 and 5) in an aqueous medium. The galvanic replacement reaction follows the 'Volmer-Weber' growth mode, resulting in the formation of surface bound platinum islands on a nanoporous gold surface. The high angle annular dark field image and low angle X-ray diffraction studies confirm the presence of nanoporous Au100-xPtx NPs. The electrochemical studies using the Au85Pt15/C catalyst show excellent methanol tolerance behaviour and better performance towards oxygen reduction reaction (ORR) in terms of high mass activity, mass-specific activity and figure of merit (FOM) when compared to HiSPEC Pt/C commercial catalyst. Preliminary studies on a full cell using nanoporous Au85Pt15/C (loading 1.0 mg cm(-2)) as the cathode material and Pt-Ru/C (loading: 0.5 mg cm(-2)) as the anode material performed better (38 mW cm(-2)) than the HiSPEC Pt/C cathode material (16 mW cm(-2)).
- Published
- 2014
22. Synthesis of porphyrin-appended poly(fluorene-alt-carbazole): photoluminescent and electrochemical studies
- Author
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V. Sannasi and D. Jeyakumar
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chemistry.chemical_classification ,Quenching (fluorescence) ,Photoluminescence ,Materials science ,Polymers and Plastics ,Carbazole ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Polymer ,Fluorene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Tetraphenylporphyrin ,Polymer chemistry ,Materials Chemistry ,0210 nano-technology ,Absorption (electromagnetic radiation) - Abstract
Poly(fluorene-alt-carbazole) appended with meso-tetraphenylporphyrin (MTPPC) linked through oxyethylene spacer and the parent poly(N-hexyl-2,7-carbazole-alt-9,9-di-n-hexyl fluorene) (P1) were synthesized and characterized. Optical absorption properties of the polymers containing 5% of MTPPC (P2) and 10% of MTPPC (P3) in the polymer backbone show extended optical absorption toward long wavelength compared to the parent polymer P1. Optical absorption studies of the polymers showed that polymer P1 has absorption at 384 nm in solution, whereas polymers P2 and P3 have absorption at 384 nm corresponding to polymer backbone and soret band at 421 nm with Q bands at around 518 and 554 nm in solution. P1 shows photoluminescence emission around 417 nm, whereas P2 and P3 fall around 656 nm. Thermal, electrochemical, and quenching studies of the polymers have been studied and the details are reported.
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- 2016
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23. Synergistic interaction of treatment and blending on the stability of high-density polyethylene
- Author
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G. Suresh, Doble Mukesh, and D. Jeyakumar
- Subjects
Chromium ,Weight loss ,Materials science ,Oxygenated compounds ,Polymers and Plastics ,Polymers ,Starch ,UV treatment ,chemistry.chemical_element ,Mechanical properties ,Thermal treatment ,Low molecular weight ,Metal-polymer complexes ,Star polymers ,Synergistic interaction ,Degradation ,chemistry.chemical_compound ,Polymer chemistry ,Materials Chemistry ,Chlorine ,Thermoplastics ,High density polyethylenes ,Metal ions ,Potato starch ,chemistry.chemical_classification ,Potato starches ,Mass spectrometry ,Treatment conditions ,Additives ,food and beverages ,General Chemistry ,Polymer ,Polyethylene ,Blending ,Waste disposal ,Hydrocarbons ,Waste treatment ,Surfaces, Coatings and Films ,chemistry ,High-density polyethylene ,Nuclear chemistry - Abstract
Degradation of high-density polyethylene (HDPE) films blended with 0.5, 1.0, and 2.0% metal ions (MIs, chromium = 36%, silicon = 8%, aluminum = 4%, and chlorine = 2%) and 5, 10, and 20% potato starch were studied under two different abiotic treatment conditions (they were either heated to 70�C or exposed to UV at 300-400 nm) for a period of 100 days. The addition of metals did not affect the mechanical strength of the polymer, whereas starch blending did. The latter turned the polymer yellow. HDPE with MIs exhibited higher levels of oxidation than the other samples. UV treatment affected the mechanical strength of the MI-blended HDPE more than the other additive or the thermal treatment. The formation of extractable oxygenated compounds and unoxidized low-molecular-weight hydrocarbons increased with increasing concentration of additives in HDPE. The surface energy in all cases increased, this indicated that the polymers turned hydrophilic. The maximum weight loss (28%) was seen in the 2% MI-blended HDPE exposed to UV followed by the 20% starch-blended polymer exposed to heat (24%). These results indicate a synergy between blending and the treatment strategy, this also suggests an optimal waste-disposal strategy. � 2012 Wiley Periodicals, Inc.
- Published
- 2012
24. Structure–property relations in hexagonal and monoclinic BiPO4:Eu3+nanoparticles synthesized by polyol-mediated method
- Author
-
Narayanan Lakshminarasimhan, D. Jeyakumar, Paulraj Arunkumar, and C. Jayajothi
- Subjects
Materials science ,General Chemical Engineering ,Hexagonal phase ,chemistry.chemical_element ,General Chemistry ,Crystal structure ,Nanocrystalline material ,Bismuth ,symbols.namesake ,Crystallography ,chemistry ,Phase (matter) ,symbols ,Isostructural ,Raman spectroscopy ,Monoclinic crystal system - Abstract
Hexagonal BiPO4·xH2O and Bi0.95Eu0.05PO4·xH2O nanoparticles were synthesized by a polyol-mediated method employing diethylene glycol. The powder X-ray diffraction revealed the phase purity and isostructural nature of both undoped and Eu3+-doped BiPO4. The monoclinic Bi0.95Eu0.05PO4 was obtained by heating the hexagonal Bi0.95Eu0.05PO4·xH2O at 600 °C. The microscopical characterization revealed the formation of nanocrystalline materials. Water molecules present in the bismuth precursor favoured the formation of hexagonal phase at low temperature. The role of DEG molecules in arresting the particle growth during the phase transformation of Bi0.95Eu0.05PO4 from hexagonal to monoclinic was observed. The synthesized materials were characterized using different spectroscopic techniques such as FT-IR, Raman, 31P MAS-NMR, DRUV-Vis and PL. The difference in the crystal structures and symmetries is clearly reflected in the spectral results of hexagonal and monoclinic Bi0.95Eu0.05PO4. The structure-property relations were studied to derive its importance from both fundamental and technological aspects.
- Published
- 2012
25. High-capacity potato peel-shaped graphite for lithium-ion batteries
- Author
-
D. Jeyakumar, T. Sri Devi Kumari, R. Surya, A. Manuel Stephan, and T. Prem Kumar
- Subjects
Materials science ,Morphology (linguistics) ,Scanning electron microscope ,chemistry.chemical_element ,Ion ,Bismuth ,symbols.namesake ,chemistry ,Chemical engineering ,symbols ,General Materials Science ,Lithium ,Graphite ,Raman spectroscopy ,Carbon - Abstract
Highly graphitic carbons are obtained by precipitating carbon from molten steel inoculated with bismuth. Scanning electron microscopy images show that the products have a potato peel morphology. The inoculant leads to a breaking of the local symmetry of the graphitic structure as evidenced by Raman spectroscopic studies. The products exhibit flat charge-discharge profiles below about 200 mV versus LrVLi, reversible capacities even exceeding the theoretical limit of 372 mAh/g for perfectly graphitic structures, low first-cycle irreversible capacities, and sustained hundreds of cycles.
- Published
- 2011
26. Performance of dye-sensitized solar cells employing polymer gel as an electrolyte and the influence of nano-porous materials as fillers
- Author
-
M. Kesavan, A. Arulraj, P. Anbarasu, Mohan Ramesh, D. Jeyakumar, K. Rajendran, and P. Anandha Ganesh
- Subjects
Materials science ,Polymers and Plastics ,Metals and Alloys ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Nano porous ,Dye-sensitized solar cell ,Chemical engineering ,Polymer gel ,0210 nano-technology - Published
- 2018
27. Synthesis and characterization of nanosized titanium dioxide and silicon dioxide for corrosion resistance applications
- Author
-
K. Maruthan, M. Selvaraj, D. Jeyakumar, and A.M. Kamalan Kirubaharan
- Subjects
chemistry.chemical_classification ,Nanocomposite ,Materials science ,Silicon dioxide ,technology, industry, and agriculture ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,Surfaces, Coatings and Films ,Dielectric spectroscopy ,Corrosion ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Coating ,Silicone resin ,Titanium dioxide ,engineering ,Interpenetrating polymer network ,Composite material - Abstract
We are reporting the preparation and characterization of nano-titanium dioxide and silica. The corrosion resistance performance of these nanopigments in silicone as well as silicone–polypyrrole Interpenetrating Polymer Network has been evaluated by impedance spectroscopy. The capacitance and resistance exerted by this nanocomposite coating were compared with the microcomposite coating and found that the nanocomposite coatings has the resistance in the order of 108 Ω cm2 in 3% sodium chloride solution, which is more than the microcomposite coating. The comparison of heat resistance performance of these composite coatings indicates that nanocomposite coatings exhibit higher heat resistance property than the microcomposite coatings.
- Published
- 2009
28. Polyol mediated synthesis of tungsten trioxide and Ti doped tungsten trioxide
- Author
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P. Porkodi, V. Yegnaraman, and D. Jeyakumar
- Subjects
Thermogravimetric analysis ,Materials science ,Scanning electron microscope ,Mechanical Engineering ,Inorganic chemistry ,Diethylene glycol ,chemistry.chemical_element ,Tungsten ,Condensed Matter Physics ,Tungsten trioxide ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Differential thermal analysis ,X-ray crystallography ,General Materials Science ,Nuclear chemistry ,Titanium - Abstract
Polyol mediated synthesis for the preparation of tungsten trioxide and titanium doped tungsten trioxide has been reported. The reaction was carried out using chlorides of tungsten and titanium in diethylene glycol medium and water as the reagent for hydrolysis at 190 deg. C. Formation of a blue coloured dimensionally stable suspension of the precursor materials was observed during the course of the reaction. The particle sizes of the precursor materials were observed to be around 100 nm. The precursor materials were annealed to give tungsten trioxide and titanium doped tungsten trioxide. The precursor materials were characterised using TGA/DTA, FT-IR, optical spectra, SEM, TEM and powder XRD methods. It was observed that the doping of titanium could be effected at least up to 10% of Ti in WO{sub 3}. The TGA/DTA studies indicated that WO{sub 3-x}.H{sub 2}O is the dominant material that formed during the polyol mediated synthesis. The XRD data of the annealed samples revealed that the crystalline phase could be manipulated by varying the extent of titanium doping in the tungsten trioxide matrix.
- Published
- 2006
29. High Temperature Processable Flexible Polymer Films
- Author
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A. Sivanantha Raja, C. Sanjeeviraja, D. Jeyakumar, and D. Shanmuga Sundar
- Subjects
Materials science ,Bioengineering ,02 engineering and technology ,Substrate (electronics) ,Flexible organic light-emitting diode ,chemistry.chemical_compound ,0202 electrical engineering, electronic engineering, information engineering ,Transmittance ,General Materials Science ,Electrical and Electronic Engineering ,chemistry.chemical_classification ,Polydimethylsiloxane ,business.industry ,020206 networking & telecommunications ,Polymer ,Conformable matrix ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Flexible electronics ,Computer Science Applications ,chemistry ,Optoelectronics ,Orthosilicate ,0210 nano-technology ,business ,Biotechnology - Abstract
Recent developments in the field of flexible electronics motivated the researchers to start working in verdict of new flexible substrate for replacing the existing rigid glass and flexible plastics. Flexible substrates offer significant rewards in terms of being able to fabricate flexible electronic devices that are robust, thinner, conformable, lighter and can be rolled away when needed. In this work, a new flexible and transparent substrate with the help of organic materials such as Polydimethylsiloxane (PDMS) and tetra ethoxy orthosilicate (TEOS) is synthesized. Transmittance of about 90–95% is acquired in the visible region (400–700[Formula: see text]nm) and the synthesized substrate shows better thermal characteristics and withstands temperature up to 200[Formula: see text]C without any significant degradation. Characteristics such as transmittance ([Formula: see text]), absorption ([Formula: see text]), reflectance ([Formula: see text]), refractive index ([Formula: see text]) and extinction coefficient ([Formula: see text]) are also reported.
- Published
- 2016
30. Yttrium oxide:Eu3+ red phosphor by self-propagating high temperature synthesis
- Author
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R. Jagannathan, M. Kottaisamy, D. Jeyakumar, and M. Mohan Rao
- Subjects
Materials science ,Scanning electron microscope ,Mechanical Engineering ,Inorganic chemistry ,Self-propagating high-temperature synthesis ,Analytical chemistry ,Oxide ,Sintering ,chemistry.chemical_element ,Phosphor ,Yttrium ,Condensed Matter Physics ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,General Materials Science ,Crystallite ,Europium - Abstract
Yttrium oxide doped with trivalent europium has been prepared by self-propagating high temperature (SPHT) synthesis, also known as combustion synthesis, with nitrogen-based fuels. The materials synthesized have been characterized by X-ray diffraction, scanning electron microscopy, and luminescent emission spectroscopy. Crystallite size, powder density, and photoluminescent-emission intensity/efficiency are found to depend on the fuels used. The phosphor products were sintered with and without sintering aids. The results obtained are discussed with respect to the processing method employed.
- Published
- 1996
31. Hydrolysis of SnCl2 on polyaniline: Formation of conducting PAni-SnO2 composite with enhanced electrochemical properties
- Author
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Shahid Anwar, D. Jeyakumar, M T Vijayan, and Chepuri R.K. Rao
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Composite number ,General Chemistry ,Polymer ,Conductivity ,Tin oxide ,Electrochemistry ,Surfaces, Coatings and Films ,Tetragonal crystal system ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Polyaniline ,Materials Chemistry ,Composite material ,In situ polymerization - Abstract
SUMMARYIn conclusion, first time we report that SnCl 2 candope PAni-EB form by producing SnO 2 and HCl.The formed HCl doped the quinoid segments of theE.B structure in a conventional way to form conduct-ing PAni salt and SnO 2 is deposited on the surfaceof the polymer concomitantly to give conductingPAni-SnO 2 composite. In this method of preparation(composite A), tin oxide particles are deposited onPAni fibers. In the case of in situ polymerization(composite B), the composite is a homogeneous mix-ture of some free SnO 2 particles, SnO 2 on PAni andas well as SnO 2 encapsulated/embedded in PAni.The conductivity of the samples A and B increasedsignificantly due to the presence of SnO 2 nanopar-ticles, where the tin oxide particles are crystallizedin tetragonal (t-SnO 2 ) structure. In this study, it isalso established that composite A and B exhibitedimproved electrochemical property compared withpure PAni. The composite B showed enhancedpseudo capacitance as high as 219 F g 1 .The authors thank the directors of IICT and CECRIfor their constant encouragement, unstinted support.References
- Published
- 2011
32. Functionalization of graphene with nitrogen using ethylenediaminetetraacetic acid and their electrochemical energy storage properties
- Author
-
N. Ilayaraja, T. K. Shruthi, Marappan Sathish, and D. Jeyakumar
- Subjects
Materials science ,Graphene ,General Chemical Engineering ,Inorganic chemistry ,Oxide ,Ethylenediaminetetraacetic acid ,General Chemistry ,Electrochemistry ,Capacitance ,law.invention ,chemistry.chemical_compound ,chemistry ,X-ray photoelectron spectroscopy ,law ,Surface modification ,Graphene oxide paper - Abstract
Recently there has been a considerable focus on the synthesis of nitrogen functionalized graphene for energy storage and conversion. Herein, we report a simple, economical and facile process for the synthesis of nitrogen containing graphene composite which can be scaled up for mass production by using a nitrogen containing organic compound, ethylenediaminetetraacetic acid (EDTA) and graphene oxide as precursors. From the XRD studies, the increase in the interlayer distance between the graphene sheets confirms the functionalization of graphene sheets and the FT-IR spectroscopic analysis revealed the presence of N-containing functional groups in N-doped graphene sheets. XPS analysis confirms the chemical nature of N-containing functional groups, and TG analysis showed the amount of EDTA loaded on the graphene sheets. This composite exhibits a large specific capacitance of 290 F g−1 at 0.1 A g−1 with a capacitance retention of 67% and 58% at high current densities of 10 and 20 A g−1, respectively, thereby showing superior rate capability. In addition, it showed long-term electrochemical stability through 6000 charge–discharge cycles even at a high current density of 5 A g−1 with a specific capacitance loss of 2%.
- Published
- 2014
33. Manganese hexacyanoferrate derived Mn3O4 nanocubes–reduced graphene oxide nanocomposites and their charge storage characteristics in supercapacitors
- Author
-
K. Subramani, Marappan Sathish, and D. Jeyakumar
- Subjects
Supercapacitor ,Nanocomposite ,Materials science ,Graphene ,Oxide ,General Physics and Astronomy ,Nanotechnology ,law.invention ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Chemical engineering ,law ,symbols ,Physical and Theoretical Chemistry ,Cyclic voltammetry ,Raman spectroscopy ,Hausmannite ,Graphene oxide paper - Abstract
Mn3O4-reduced graphene oxide (RGO) nanocomposites were prepared by chemical decomposition of the manganese hexacyanoferrate (MnHCF) complex directly on the graphene surface. XRD studies revealed the formation of crystalline hausmannite Mn3O4 nanocubes in the as-prepared nanocomposites without any heat treatment. The FE-SEM images showed the formation of Mn3O4 nanocubes on the graphene surface in the as-prepared nanocomposites. HR-TEM studies confirmed the homogeneous dispersion of ∼25 nm Mn3O4 nanocubes on graphene nanosheets. The amount of Mn3O4 nanocubes and graphene in the nanocomposites was estimated using TGA analysis from room temperature to 800 °C in air. The FT-IR and Raman spectroscopic analysis confirmed the functional groups in the nanocomposites and defects in graphene nanosheets in the nanocomposites. Cyclic voltammetry and galvanostatic charge-discharge experiments demonstrated a high specific capacitance of 131 F g(-1) in 1 M Na2SO4 electrolyte at a current density of 0.5 A g(-1) for the RGM-0.5 nanocomposite. A capacitance retention of 99% was observed for 500 charge-discharge cycles at a current density of 5 A g(-1), which conformed the excellent stability of the RGM electrodes. The prepared Mn3O4-RGO nanocomposites are promising for electrochemical energy storage.
- Published
- 2014
34. Au–Pt graded nano-alloy formation and its manifestation in small organics oxidation reaction
- Author
-
Palanichamy Murugan, Narayanan Lakshminarasimhan, N. Ilayaraja, D. Jeyakumar, and N. Prabu
- Subjects
Materials science ,Absorption spectroscopy ,X-ray photoelectron spectroscopy ,Renewable Energy, Sustainability and the Environment ,Transmission electron microscopy ,Analytical chemistry ,Nanoparticle ,General Materials Science ,Chemical stability ,General Chemistry ,Cyclic voltammetry ,High-resolution transmission electron microscopy ,Catalysis - Abstract
A graded nano-alloy of Au100−xPtx (x = 7, 15, 23, 32, 40, 51, 62, 73 and 86) nanoparticles (NPs) formed by co-reduction of HAuCl4 and H2PtCl6 and the details are presented in this work. Au100−xPtx NPs were characterized using surface plasmon resonance (SPR) absorption spectroscopy and transmission electron microscopy (TEM). The NPs were dispersed in Vulcan carbon (Au100−xPtx/C) and annealed at 250, 400, 600 and 800 °C. The as-formed and annealed materials were characterized using TEM, high resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (XRD), cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The CV studies indicate excess Pt on the surface, which is corroborated by XPS and HR-TEM results. The XRD data show that Vegard's law is obeyed by the as-formed material and the materials annealed at 250 and 400 °C, indicating that these materials are not nano-alloys. The studies clearly indicate that the formation of Au100−xPtx NPs is kinetically controlled rather than being controlled by the thermodynamic stability. The results demonstrate the formation of graded alloys of Au100−xPtx NPs. Pt excess in the graded nano-alloy is reflected favourably in the electrochemical oxidation of small organics. In the methanol oxidation reaction (MOR), the peak current value per mg of Pt increases as a function of x, reaches a maximum value at x = 23 and the ratio of forward current to reverse current for MOR reached an unprecedented value of 6.7, which shows the catalyst’s stability against poisoning by carbonaceous intermediates.
- Published
- 2013
35. Nano silicon carbide: a new lithium-insertion anode material on the horizon
- Author
-
D. Jeyakumar, T. Sri Devi Kumari, and T. Prem Kumar
- Subjects
Materials science ,General Chemical Engineering ,chemistry.chemical_element ,General Chemistry ,Chemical vapor deposition ,Electrochemistry ,Anode ,Carbide ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Nano ,Silicon carbide ,Lithium ,Nano silicon - Abstract
Bulk-synthesized silicon carbide, hitherto considered inactive for electrochemical lithium insertion, is demonstrated as a potential high-capacity, long-cycling anode material for lithium-ion batteries. In this study, we show that cubic (3C polytype) nano SiC, prepared by a chemical vapour deposition (CVD) method, delivers a reversible lithium insertion capacity of about 1200 mA h g−1 over 200 cycles.
- Published
- 2013
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