Microstructure, structural, optical and piezoelectric properties of BiFeO₃ nanopowder synthesized from sol-gel

Sankar Ganesh, R.,Sharma, S.K.,Sankar, S.,Divyapriya, B.,Durgadevi, E.,Raji, P.,Ponnusamy, S.,Muthamizhchelvan, C.,Hayakawa, Y.,Kim, D.Y. ELSEVIER 2017 Current Applied Physics Vol.17 No.3

<P>Nanocrystalline BiFeO3 (BFO) powder was synthesized by sol-gel method and subsequent annealed at 100-500 degrees C. The microstructural analysis of BFO nanopowder confirmed the perovskite like structure of spherical nanoparticles annealed at 500 degrees C. The Raman spectrum of BFO nanoparticles showed the rhombohedrally structure with the space group of R3c. The XPS spectrum of BFO nanopowder showed the peaks of Bi, Fe, and O at the binding energy of 158.8, 711.75 and 529.2 eV, respectively. The piezoelectric properties of BFO nanoparticles were evaluated by making the sandwiched structure of graphene/BiFeO3-PDMS/graphene. The fabricated piezoelectric device demonstrated an output voltage of 0.4 V by applying the normal pressure from human finger on the device. (C) 2016 Elsevier B.V. All rights reserved.</P>

Photocatalytic properties of Mn-doped NiO spherical nanoparticles synthesized from sol-gel method

Sankar, S.,Sharma, Sanjeev K.,An, Namhyun,Lee, Hwauk,Kim, Deuk Young,Im, Young Bin,Cho, Yung Duk,Ganesh, R. Sankar,Ponnusamy, S.,Raji, P.,Purohit, L.P. Elsevier 2016 OPTIK -STUTTGART- Vol.127 No.22

<P><B>Abstract</B></P> <P>Mn-doped NiO (NiO:Mn) nanopowders were synthesized from an inexpensive sol-gel method. The XRD peak profile analysis of NiO:Mn nanopowders confirmed the cubic structure. The spherical nanoparticles of NiO:Mn were evaluated from the SEM and TEM analysis and the grain size decreased as the Mn concentration increased. The average crystallite size decreased from 35.44nm to 30.5nm and the bandgap increased from 3.79eV to 3.95eV as the Mn concentration increased from 0wt.% to 4wt.%. The photocatalytic properties of NiO:Mn nanopowders were measured for the lowest and highest Mn dopant concentrations (Mn: 0 & 4wt.%) by using the methylene blue dye under UV illumination. The NiO:Mn (Mn: 4wt.%) nanoparticles showed the highest photocatalytic activity due to the highest activation sites. Therefore, it is revealed that the Mn: 4wt.% nanoparticles are observed to be more suitable for the photocatalytic activity of methylene blue dye degradation.</P>

Microstructure, structural, optical and piezoelectric properties of BiFeO3 nanopowder synthesized from sol-gel

R. Sankar Ganesh,Sanjeev K. Sharma,S. Sankar,B. Divyapriya,E. Durgadevi,P. Raji,S. Ponnusamy,C. Muthamizhchelvan,Y. Hayakawa,김득영 한국물리학회 2017 Current Applied Physics Vol.17 No.3

Nanocrystalline BiFeO3 (BFO) powder was synthesized by sol-gel method and subsequent annealed at 100e500 C. The microstructural analysis of BFO nanopowder confirmed the perovskite like structure of spherical nanoparticles annealed at 500 C. The Raman spectrum of BFO nanoparticles showed the rhombohedrally structure with the space group of R3c. The XPS spectrum of BFO nanopowder showed the peaks of Bi, Fe, and O at the binding energy of 158.8, 711.75 and 529.2 eV, respectively. The piezoelectric properties of BFO nanoparticles were evaluated by making the sandwiched structure of graphene/ BiFeO3-PDMS/graphene. The fabricated piezoelectric device demonstrated an output voltage of 0.4 V by applying the normal pressure from human finger on the device.

Purification and Partial Characterization of a Detergent and Oxidizing Agent Stable Alkaline Protease from a Newly Isolated Bacillus subtilis VSG-4 of Tropical Soil

Sib Sankar Giri,V. Sukumaran,Shib Sankar Sen,M. Oviya,B. Nazeema Banu,Prasant Kumar Jena 한국미생물학회 2011 The journal of microbiology Vol.49 No.3

An extracellular detergent tolerant protease producing strain VSG-4 was isolated from tropical soil sample and identified as Bacillus subtilis based on morphological, biochemical characteristics as well as 16S-rRNA gene sequencing. The VSG-4 protease was purified to homogeneity using ammonium sulphate precipitation,dialysis and sephadex G-200 gel permeation chromatography with a 17.4 purification fold. The purified enzyme was active and stable over a broad range of pH (8.0-11.0, optimum at 9.0) and temperature (40°C to 60°C, optimum at 50°C). The thermostability of the enzyme was significantly increased by the addition CaCl_2. This enzyme was strongly inhibited by PMSF and DFP, suggesting that it belongs to the serine protease superfamily. The purified VSG-4 alkaline protease showed remarkable stability in anionic (5 mM SDS) and ionic (1% Trion X-100 and 1% Tween 80) detergents. It retained 97±2% and 83.6±1.1% of its initial activity after 1 h preincubation in the presence of 1% H_2O_2 and 1% sodium perborate, respectively. Furthermore, the purified enzyme showed excellent stability and compatibility with some commercial laundry detergents besides its stain removal capacity. Considering these promising properties, VSG-4 protease may find tremendous application in laundry detergent formulations.

Two-fluid non-Newtonian models for blood flow in catheterized arteries - A comparative study

D. S. Sankar,Usik Lee 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9

Steady flow of blood through catheterized arteries is studied by assuming the blood as a two-fluid model with the suspension of all the erythrocytes in the core region as a non-Newtonian fluid and the plasma in the peripheral layer as a Newtonian fluid. The non-Newtonian fluid in the core region of the artery is modeled as (i) Casson fluid and (ii) Herschel-Bulkley fluid. The expressions for the shear stress, velocity, flow rate, wall shear stress and flow resistance, obtained by Sankar and Lee (2008a, 2008b) for the two-fluid Casson model and two-fluid Herschel-Bulkley model are used to get the data for comparison. It is noticed that the plug flow velocity, velocity distribution and flow rate for the two-fluid H-B model are considerably higher than that of the two-fluid Casson model for a given set of values of the parameters. Further, it is found that the resistance to flow is significantly lower for the two-fluid H-B model than that of the two-fluid Casson model. Thus, the two-fluid H-B model is more useful than the two-fluid Casson model to analyze the blood flow through catheterized arteries.

<i>Chlorophytum borivilianum</i> Polysaccharide Fraction Provokes the Immune Function and Disease Resistance of <i> Labeo rohita</i> against <i> Aeromonas hydrophila</i>

Giri, Sib Sankar,Sen, Shib Sankar,Chi, Cheng,Kim, Hyoun Joong,Yun, Saekil,Park, Se Chang,Sukumaran, V. Hindawi Publishing Corporation 2015 Journal of immunology research Vol.2015 No.-

<P>The present study aimed to investigate the effects of<I> Chlorophytum borivilianum</I> polysaccharide (CBP), as a dietary supplement administered at varying concentrations with feed (basal diet), on various cytokine-related responses in<I> Labeo rohita</I> fingerlings. Immune parameters and immune-related gene expressions were measured at 3rd, 4th, and 5th week after feeding. The results revealed that dietary administration of CBP at 0.2% and 0.4% for 4 weeks significantly upregulated serum lysozyme and phagocytic activity. Complement C3 and respiratory burst activity (RBA) were significantly higher after 4 weeks of CBP feeding. The immune related genes<I> IL-8</I>,<I> IL-1β</I>,<I> TNF-α</I>, and<I> iNOS</I> were downregulated (<I>P</I> < 0.05) in groups with 0.2% and 0.4% CBP supplemented diets at week 4. Expression of anti-inflammatory cytokines (<I>IL-10</I> and<I> TGF-β</I>) was also downregulated (<I>P</I> < 0.5) after 4 weeks of feeding with 0.2% to 0.8% CBP. However, five weeks of CBP administration had no significant effect on immune gene expression, except<I> TNF-α</I> and<I> IL-8</I>. Fish fed with 0.4% CBP for 4 weeks showed maximum resistance against<I> Aeromonas hydrophila</I> (73.3% survival) compared to control. From these results, we recommend that CBP administration at 0.4% for 4 weeks could effectively improve immune response and disease resistance in<I> L. rohita</I>.</P>

Biogenerated silica nanoparticles synthesized from sticky, red, and brown rice husk ashes by a chemical method

Sankar, S.,Sharma, S.K.,Kaur, N.,Lee, B.,Kim, D.Y.,Lee, S.,Jung, H. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.4

An inexpensive chemical method was used to synthesize biogenic mesoporous silica (m-SiO<SUB>2</SUB>) from rice husk ash (RHA). A comparative study was carried out to produce silica nanoparticles (S-SiO<SUB>2</SUB>, R-SiO<SUB>2</SUB>, and B-SiO<SUB>2</SUB>) from three type of rice husk ashes (sticky, red, and brown). The microstructure of m-SiO<SUB>2</SUB> was dependent on the geographical provenance and the types of RHA. An analysis of the SEM and TEM micrographs reveals that the S-SiO<SUB>2</SUB> nanoparticles had a clustered spherical shape, while R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles were found to be purely spherical. The average crystallite size of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles evaluated from the TEM measurements were observed to be 50, 20 and 10nm, respectively. The XRD pattern of silica nanopowders had an absence of sharp peaks that confirmed the amorphous nature of the material. The Fourier transform infrared (FTIR) spectra of silica nanoparticles showed the symmetric Si-O and O-Si-O stretching bond vibrations at 462, 1088, and 1098cm<SUP>-1</SUP>. The surface area of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanopowders was measured to be 7.5513, 201.45, and 247.18m<SUP>2</SUP>g<SUP>-1</SUP>, respectively. The surface area of uniformly-distributed spherical nanoparticles of B-SiO<SUB>2</SUB> was observed the highest, which can be applied for the application of energy storage and drug delivery systems.

Facile hydrothermal synthesis of carbon-coated cobalt ferrite spherical nanoparticles as a potential negative electrode for flexible supercapattery

Sankar, Kalimuthu Vijaya,Shanmugapriya, Sathyanarayanan,Surendran, Subramani,Jun, Seong Chan,Selvan, Ramakrishnan Kalai Elsevier 2018 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.513 No.-

<P><B>Abstract</B></P> <P>Battery type electrodes would replace the currently available pseudocapacitive electrodes by the cause of high energy density and long discharge time. In this regard, battery type carbon coated CoFe<SUB>2</SUB>O<SUB>4</SUB> spherical nanoparticles is prepared by the facile hydrothermal method and tested as the possible negative electrode for supercapattery applications. The phase purity, electronic states of elements, and the presence of carbon is inferred through various sophisticated techniques. The calculated surface area of CoFe<SUB>2</SUB>O<SUB>4</SUB> and carbon coated CoFe<SUB>2</SUB>O<SUB>4</SUB> are found to be 9 and 26 m<SUP>2</SUP> g<SUP>−1</SUP>, respectively. The morphological analysis confirms the formation of uniform CoFe<SUB>2</SUB>O<SUB>4</SUB> nanospheres (∼25 nm) with a thin layer of carbon coating (∼2 nm). The amorphous carbon coating over CoFe<SUB>2</SUB>O<SUB>4</SUB> nanosphere is identified via high-resolution transmission electron microscope. The observed peak and plateau regions in the cyclic voltammogram and galvanostatic charge/discharge curves reveals the battery-type charge storage behaviour of the material. The carbon coated CoFe<SUB>2</SUB>O<SUB>4</SUB> delivers the maximum length capacitance of 9.9 F m<SUP>−1</SUP> at 1 mV s<SUP>−1</SUP> with a useful lifespan over 5000 cycles. The electrochemical impedance spectroscopy reveals that the carbon-coated CoFe<SUB>2</SUB>O<SUB>4</SUB> delivers the low charge transfer resistance than CoFe<SUB>2</SUB>O<SUB>4</SUB>. Further, the fabricated supercapattery provides the energy density of 160 × 10<SUP>−8</SUP> Wh cm<SUP>−1</SUP> at a power density of 67.2 μW cm<SUP>−1</SUP>. As well as, the device shows 93% of coulombic efficiency and 75% of the specific capacitance retention over 11,000 cycles. Overall, it is believed that the carbon-coated CoFe<SUB>2</SUB>O<SUB>4</SUB> can serve as a good candidate for flexible supercapatteries.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Template-free rapid sonochemical synthesis of spherical α-MnO₂ nanoparticles for high-energy supercapacitor electrode

Sankar, S.,Inamdar, Akbar I.,Im, Hyunsik,Lee, Sejoon,Kim, Deuk Young Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.14

<P><B>Abstract</B></P> <P>Spherical MnO<SUB>2</SUB> nanoparticles were synthesized at room temperature <I>via</I> template-free sonochemical reduction of potassium permanganate using a reducing agent of polyethylene glycol under two different time durations (<I>i.e.</I>, 15 min (M1) and 30 min (M2)). The M2 sample exhibited the α-phase of the tetragonal MnO<SUB>2</SUB> structure, whereas the M1 sample showed the δ-MnO<SUB>2</SUB> phase. For microstructural analyses, the M2 sample revealed a spherical structure of the nanoparticles with an average grain size of 20–30 nm. When using spherical MnO<SUB>2</SUB> nanoparticles (<I>i.e.</I>, M2) as an electrode material for the supercapacitor device, the maximum specific capacitance of 136 F/g was observed at the current density of 0.5 A/g. The device displayed an excellent cyclic stability of 72% after 5000 charge/discharge cycles, and showed a high energy density up to 38.3 Wh/kg. These results suggest that the sonochemically-synthesized spherical MnO<SUB>2</SUB> nanoparticles could be used as a suitable electrode material for high-energy electrochemical supercapacitors.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ultrathin graphene nanosheets derived from rice husks for sustainable supercapacitor electrodes

Sankar, S.,Lee, H.,Jung, H.,Kim, A.,Ahmed, A.,Inamdar, A.,Kim, H.,Lee, S.,Im, H.,YoungKim, D. Royal Society of Chemistry 2017 New journal of chemistry Vol.41 No.22