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

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>

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.

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.

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>

Redox Additive-Improved Electrochemically and Structurally Robust Binder-Free Nickel Pyrophosphate Nanorods as Superior Cathode for Hybrid Supercapacitors

Sankar, Kalimuthu Vijaya,Seo, Youngho,Lee, Su Chan,Chan Jun, Seong American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.9

<P>For several decades, one of the great challenges for constructing a high-energy supercapacitor has been designing electrode materials with high performance. Herein, we report for the first time to our knowledge a novel hybrid supercapacitor composed of battery-type nickel pyrophosphate one-dimensional (1D) nanorods and capacitive-type N-doped reduced graphene oxide as the cathode and anode, respectively, in an aqueous redox-added electrolyte. More importantly, ex situ microscopic images of the nickel pyrophosphate 1D nanorods revealed that the presence of the battery-type redox additive enhanced the charge storage capacity and cycling life as a result of the microstructure stability. The nickel pyrophosphate 1D nanorods exhibited their maximum specific capacitance (8120 mF cm<SUP>-2</SUP> at 5 mV s<SUP>-1</SUP>) and energy density (0.22 mWh cm<SUP>-2</SUP> at a power density of 1.375 mW cm<SUP>-2</SUP>) in 1 M KOH + 75 mg K<SUB>3</SUB>[Fe(CN)<SUB>6</SUB>] electrolyte. On the other side, the N-doped reduced graphene oxide delivered an excellent electrochemical performance, demonstrating that it was an appropriate anode. A hybrid supercapacitor showed a high specific capacitance (224 F g<SUP>-1</SUP> at a current density of 1 A g<SUP>-1</SUP>) and high energy density (70 Wh kg<SUP>-1</SUP> at a power density of 750 W kg<SUP>-1</SUP>), as well as a long cycle life (a Coulombic efficiency of 96% over 5000 cycles), which was a higher performance than most of those in recent reports. Our results suggested that the materials and redox additive in this novel design hold great promise for potential applications in a next-generation hybrid supercapacitor.</P> [FIG OMISSION]</BR>

Rapid sonochemical synthesis of spherical silica nanoparticles derived from brown rice husk

Sankar, S.,Kaur, Narinder,Lee, Sejoon,Kim, Deuk Young Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.7

<P><B>Abstract</B></P> <P>The nanoparticles of silica (SiO<SUB>2</SUB>) were synthesized from brown rice husk <I>via</I> the sonochemical process, during which the sonication time was varied from 0 to 50 min so as to modulate the material properties of the nanoparticles. The synthesized SiO<SUB>2</SUB> nanoparticles were confirmed to have amorphous natures in their structural characteristics. The mean particle sizes of the nanoparticles were increased from 5 to 40 nm with increasing sonication time from 0 to 50 min, respectively. The SiO<SUB>2</SUB> nanoparticles synthesized with the sonication time of 50 min showed to possess the highest porosity among our samples. Accordingly, the sample exhibited a higher effective surface area of 271.22 m<SUP>2</SUP>g<SUP>−1</SUP>. In addition, the bandgap of the SiO<SUB>2</SUB> nanoparticles was decreased from 5.77 to 5.68 eV with increasing sonication time (<I>i.e.</I>, 0 → 50 min). The results suggest that the SiO<SUB>2</SUB> nanoparticles synthesized with an appropriate control of the sonication time (<I>e.g.</I>, 50 min) hold promise for future nano-ecosystem applications such as nano-biosensors and energy storage nano-devices.</P>

Binder-free cobalt phosphate one-dimensional nanograsses as ultrahigh-performance cathode material for hybrid supercapacitor applications

Sankar, K. Vijaya,Lee, S.C.,Seo, Y.,Ray, C.,Liu, S.,Kundu, A.,Jun, S.C. Elsevier Sequoia 2018 Journal of Power Sources Vol. No.

<P><B>Abstract</B></P> <P>One-dimensional (1D) nanostructure exhibits excellent electrochemical performance because of their unique physico-chemical properties like fast electron transfer, good rate capability, and cyclic stability. In the present study, Co<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> 1D nanograsses are grown on Ni foam using a simple and eco-friendly hydrothermal technique with different reaction times. The open space with uniform nanograsses displays a high areal capacitance, rate capability, energy density, and cyclic stability due to the nanostructure enhancing fast ion and material interactions. Ex-situ microscope images confirm the dependence of structural stability on the reaction time, and the nanograsses promoted ion interaction through material. Further, the reproducibility of the electrochemical performance confirms the binder-free Co<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> 1D nanograsses to be a suitable high-performance cathode material for application to hybrid supercapacitor. Finally, the assembled hybrid supercapacitor exhibits a high energy density (26.66 Wh kg<SUP>−1</SUP> at 750 W kg<SUP>−1</SUP>) and longer lifetimes (80% retained capacitance after 6000 cycles). Our results suggests that the Co<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> 1D nanograss design have a great promise for application to hybrid supercapacitor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Binder-free cobalt phosphate cathode for hybrid supercapacitor. </LI> <LI> Stable structure and good electrochemical interaction confirmed via morphology. </LI> <LI> Uniform and direct growth enhances the electrochemical performance. </LI> <LI> The OH<SUP>−</SUP> ions more favor for large energy storage than NO<SUB>3</SUB> <SUP>−</SUP> ions. </LI> <LI> Ex-situ analysis confirms the influence of morphology on cyclic stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

An Adaptive Image Quality Assessment Algorithm

Sankar, Ravi,Ivkovic, Goran The Institute of Internet 2012 Journal of Advanced Smart Convergence Vol.1 No.1

An improved algorithm for image quality assessment is presented. First a simple model of human visual system, consisting of a nonlinear function and a 2-D filter, processes the input images. This filter has one user-defined parameter, whose value depends on the reference image. This way the algorithm can adapt to different scenarios. In the next step the average value of locally computed correlation coefficients between the two processed images is found. This criterion is closely related to the way in which human observer assesses image quality. Finally, image quality measure is computed as the average value of locally computed correlation coefficients, adjusted by the average correlation coefficient between the reference and error images. By this approach the proposed measure differentiates between the random and signal dependant distortions, which have different effects on human observer. Performance of the proposed quality measure is illustrated by examples involving images with different types of degradation.