3D yolk-shell NiGa2S4 microspheres confined with nanosheets for high performance supercapacitors

Liu, S.,Kim, K.,Yun, J.,Kundu, A.,Sankar, K. V.,Patil, U.,Ray, C.,ChanJun, S. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.13

<P>Recent advances in the development of two-dimensional transition-metal chalcogenides (2D TMCs) have opened up new avenues for supercapacitor applications. However, they still suffer from limited specific capacitance and poor rate capability due to their poor interfacial properties and simple geometry. Here, we propose a facile strategy for the synthesis of yolk-shell NiGa2S4 microspheres comprising crumpled nanosheets supported on nickel foam. The robust structure not only highly facilitates the electron and charge transportation but also efficiently alleviates the volume expansion during redox reactions, contributing to excellent electrochemical behaviors in terms of specific capacitance and rate capability. Significantly, an asymmetric supercapacitor based on the prepared NiGa2S4 as the positive electrode and N, S-codoped graphene/Fe2O3 (N, S-G/Fe2O3) as the negative electrode delivers a high energy density of 43.6 W h kg(-1) at a power density of 961 W kg(-1) and retains an energy density of 22.2 W h kg(-1) even at 15 974 W kg(-1). These impressive results may provide a new perspective to develop high energy and power density storage systems for practical applications.</P>

Controllable sulfuration engineered NiO nanosheets with enhanced capacitance for high rate supercapacitors

Liu, S.,Lee, S.,Patil, U.,Ray, C.,Sankar, K. V.,Zhang, K.,Kundu, A.,kang, S.,Park, J.,ChanJun, S. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.9

<P>NiO has been intensively studied as a promising electrode material for supercapacitors because of its high theoretical specific capacitance, well-defined redox behavior, and good chemical compatibility with nickel foam. However, it still suffers from inferior rate capability and cycling stability because of the simple component and random structural integration. Herein, we report a tunable sulfuration process of NiO nanosheets constructed on porous nickel foam for supercapacitor applications. The resulting NiO/Ni3S2 with distinct structural features exhibits an ultra-high specific capacitance of 2153 F g(-1) at a current density of 1 A g (1), and the capacitance is retained at 1169 F g (1) even at a current density as high as 30 A g (1). An asymmetric supercapacitor device fabricated with NiO/Ni3S2 as the positive electrode and activated carbon as the negative electrode delivers high energy and power densities (52.9 W h kg(-1) at 1.6 kW kg(-1); 26.3 W h kg(-1) at 6.4 kW kg(-1)), and good cycling stability (a capacitance retention of 92.9% over 5000 cycles).</P>

A sub-decadal trend in diacids in atmospheric aerosols in eastern Asia

Kundu, S.,Kawamura, K.,Kobayashi, M.,Tachibana, E.,Lee, M.,Fu, P. Q.,Jung, J. Copernicus GmbH 2016 Atmospheric Chemistry and Physics Vol.16 No.2

<P>Abstract. Change in secondary organic aerosols (SOAs) has been predicted to be highly uncertain in the future atmosphere in Asia. To better quantify the SOA change, we examine the sub-decadal (2001-2008) trend in major surrogate compounds (C2-C10 diacids) of SOA in atmospheric aerosols from Gosan site on Cheju Island, South Korea. The Gosan site is influenced by pollution outflows from eastern Asia. The molecular distributions of diacids were characterized by the predominance of oxalic (C2) acid followed by malonic (C3) and succinic (C4) acids in each year. The seasonal variations in diacids in each year were characterized by the highest concentrations of saturated diacids in spring and unsaturated diacids in winter. The consistent molecular distributions and seasonal variations along with significantly similar air mass transport patterns are indicative of similar pollution sources for diacids in eastern Asia on a sub-decadal scale. However, the intensity of the pollution sources has increased as evidenced by the increases in major diacids at the rate of 3.9-47.4 % per year, particularly in April. The temporal variations in atmospheric tracer compounds (carbon monoxide, levoglucosan, 2-methyltetrols, pinic acid, glyoxylic acid, glyoxal and methylglyoxal) suggest that the increases in diacids are due to enhanced precursor emissions associated with more anthropogenic than biogenic activities followed by the compounds' chemical processing in the atmosphere. The trends in diacids contrast with the reported decreases in sulfate, nitrate and ammonium in recent years in eastern Asia. This study demonstrates that recent pollution control strategies in eastern Asia were not able to decrease organic acidic species in the atmosphere. The increases in water-soluble organic acid fraction could modify the aerosol organic composition and its sensitivity to climate relevant physical properties. </P>

Secrecy performance of a-k-u shadowed fading channel

A.S.M. Badrudduza,S.H. Islam,M.K. Kundu,I.S. Ansari 한국통신학회 2023 ICT Express Vol.9 No.2

In this paper, the physical layer security aspects of a wireless framework over shadowed (AKMS) fading channel are examined by acquiring closed-form novel expressions of average secrecy capacity, secure outage probability (SOP), and strictly positive secrecy capacity. The lower bound of SOP is derived along with the asymptotic expression of SOP at the high signal-to-noise ratio regime in order to achieve secrecy diversity gain. Capitalizing on these expressions, the consequences due to the simultaneous occurrence of fading and shadowing are quantified. Finally, Monte-Carlo simulations are demonstrated to assess the correctness of the expressions.

Bias dependent relaxation in different phases of an orthoconic antiferroelectric liquid crystal mixture (W-182)

P. Nayek,S. Ghosh,S. Kundu,T. Pal Majumder,S.K. Roy,N. Bennis,J.M. Otón,R. Dabrowski 한국물리학회 2010 Current Applied Physics Vol.10 No.2

The electro-optical behavior of the orthoconic antiferroelectric liquid crystal mixture W-182 has been studied. Surface-stabilized, low thickness cells of this mixture give a perfect double hysteresis loop with 1 Hz triangular signal, reaching different transmission levels for different voltages amplitudes. These levels can be stabilized with a single holding voltage, making it possible for the material to be passively multiplexed at video rate. With the application of bias field at three different temperatures, we have observed the field-induced Fréedericksz transition from SmI*A–SmC*A, antiferroelectric to ferroelectric, and ferroelectric to paraelectric transition. Such Fréedericksz transition point is decreased with the increase of temperature.

Runx3 is required for the differentiation of lung epithelial cells and suppression of lung cancer

Lee, K-S,Lee, Y-S,Lee, J-M,Ito, K,Cinghu, S,Kim, J-H,Jang, J-W,Li, Y-H,Goh, Y-M,Chi, X-Z,Wee, H,Lee, H-W,Hosoya, A,Chung, J-H,Jang, J-J,Kundu, J K,Surh, Y-J,Kim, W-J,Ito, Y,Jung, H-S,Bae, S-C Macmillan Publishers Limited 2010 Oncogene Vol.29 No.23

Human lung adenocarcinoma, the most prevalent form of lung cancer, is characterized by many molecular abnormalities. K-ras mutations are associated with the initiation of lung adenocarcinomas, but K-ras-independent mechanisms may also initiate lung tumors. Here, we find that the runt-related transcription factor Runx3 is essential for normal murine lung development and is a tumor suppressor that prevents lung adenocarcinoma. Runx3−/− mice, which die soon after birth, exhibit alveolar hyperplasia. Importantly, Runx3−/− bronchioli exhibit impaired differentiation, as evidenced by the accumulation of epithelial cells containing specific markers for both alveolar (that is SP-B) and bronchiolar (that is CC10) lineages. Runx3−/− epithelial cells also express Bmi1, which supports self-renewal of stem cells. Lung adenomas spontaneously develop in aging Runx3+/− mice (∼18 months after birth) and invariably exhibit reduced levels of Runx3. As K-ras mutations are very rare in these adenomas, Runx3+/− mice provide an animal model for lung tumorigenesis that recapitulates the preneoplastic stage of human lung adenocarcinoma development, which is independent of K-Ras mutation. We conclude that Runx3 is essential for lung epithelial cell differentiation, and that downregulation of Runx3 is causally linked to the preneoplastic stage of lung adenocarcinoma.

Leucaena Seeds as Protein Supplement in the Rations of Growing Sheep

Singh, Sultan,Kundu, S.S.,Negi, A.S.,Gupta, S.K.,Singh, N.P.,Pachouri, V.C. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.10

The study was carried out to evaluate leucaena seeds as a protein replacement of mustard seed cake (MSC) in the concentrate mixture of growing lambs. Fifteen owing male lambs (Local${\times}$Corridale) with an average body weight of 16.3 kg were allocated into three dietary treatments (T1, T2, and T3) with five animals in each group. Animals were offered dry mixed grass, berseem hay and concentrate mixture to meet their nutrient requirements. In concentrate mixture of T1, (Control) MSC was used as protein source, while in T2 and T3 groups, 25 and 50% of MSC was replaced by leucaena leucocephala seeds. On completion of three months (90 days) of feeding, a digestion cum-metabolism trial was conducted to determine DMI, nutrient utilization, and nitrogen balance. Changes in body weight were recorded at 15 day internals and eating patterns were recorded for 3 consecutive days at the end of the feeding trial. MSC had higher CP contents than leucaena seeds (27.0%). Mimosine contents in leucaena seeds were 1.1 compared to 0.2 and 0.4% in concentrate mixture of T2 and T3 group, respectively. Dry matter intake varied non-significantly ($79.3{\pm}1.2$ to $83.4{\pm}1.3g/kg$ $w^{0.75}$) across the dietary treatments. Digestibility of DM and cell wall polysaccharides (NDF, ADF. Cellulose and hemicellulose) were comparable, however CP digestibility was relatively lower in leucaena luecocephala seeds based groups (T2 $45.5{\pm}1.7$ and T3 $46.7{\pm}3.5$) compared to MSC supplemented group (T1 $47.7{\pm}0.9%$). The growth rate of lambs was non-significantly higher in T1 ($79.2{\pm}5.4$) compared to T2 ($73.8{\pm}8.8$) and T3 ($73.9{\pm}7.0$), respectively. The animals were in positive nitrogen balance and N-balance varied from 1.8 to 2.9 g/d across treatment groups. The eating rate (% of total offered) of concentrate up-to 15 min was relatively higher in T1 (82.4) than T2 (74.2) and T3 (77.8%). However no effect of leucaena seeds was recorded on total DMI of animals. The results of the study revealed that the inclusion of up to 50% leucaena seeds, as protein source in concentrate mixture of lambs had no adverse effect on DMI, nutrient utilization, eating patterns, nitrogen balance and growth performance of lambs.

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>

Zinc Chloride Modified Electronic Transport and Relaxation Studies in Barium-Tellurite Glasses

Sunil Dhankhar,R. S. Kundu,Sunita Rani,Preeti Sharma,S. Murugavel,Rajesh Punia,N. Kishore 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.5

The ac conductivity of halide based tellurium glasses havingcomposition 70 TeO2-(30-x) BaO-x ZnCl2 ; x = 5, 10, 15 , 20 and 25has been investigated in the frequency range 10-1 Hz to 105Hz and inthe temperature range 453 K to 553 K. The frequency and temperaturedependent ac conductivity show mixed behaviour with increase inhalide content and found to obey Jonscher’s universal power law. Thevalues of dc conductivity, crossover frequency and frequency exponenthave been estimated from the fitting of experimental data of acconductivity with Jonscher’s universal power law. For determining theconduction mechanism in studied glass system, frequency exponent hasbeen analyzed by various theoretical models. In presently studiedglasses, the ac conduction takes place via overlapping large polarontunneling (OLPT). The values of activation energy for dc conduction(W) and the one associated with relaxation process (ER) are found toincrease with increase in x up to glass sample with x = 15 and thereafterit decrease with increase in zinc chloride content. DC conduction takes place via variable range hopping (VRH) as proposed byMott with some modification suggested by Punia et al. The value of real part of modulus (M') is observed to decrease withincrease in temperature. The value of stretched exponent (β) obtained from fitting of M'' reveals the presence of non-Debye typeof relaxation in presently studied glass samples. Scaling spectra of ac conductivity and values of electric modulus (M' and M'')collapse into a single master curve for all the compositions and temperatures. The values of relaxation energy (ER) for all thestudied glass compositions are almost equal to W, suggesting that polarons have to overcome same barrier while relaxing andconducting. The conduction and relaxation processes in the studied glass samples are composition and temperature independent.

Facile synthesis of pristine FeS2 microflowers and hybrid rGO-FeS2 microsphere electrode materials for high performance symmetric capacitors

B. Balamuralitharan,Suresh Kannan Balasingam,S. N. Karthick,Ananthakumar Ramadoss,Manab Kundu,박진수,조인호,프라바카르,전용석,김희제 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-

Iron pyrite (FeS2) is an interesting mineral in the transition metal dichalcogenide group due to its highabundance in the earth’s crust which can be used for various electrochemical energy storage applications,such as batteries and supercapacitors; however, it suffers from low rate capability and poor cycleperformance, which hampers its use from large-scale commercial applications. In the present study, irondisulfide microspheres anchored onto a reduced graphene oxide matrix (rGO-FeS2 hybrid) were grownusing a superficial hydrothermal method. For comparison, rGO-free iron disulfide material wassynthesized under the same hydrothermal conditions, and uniformly distributed FeS2 micro-sizeflowerswere formed. The energy storage capacity of both electroactive materials (FeS2 and rGO-FeS2 hybridmaterial) was tested for supercapacitor applications in a symmetric cell configuration. The pristine FeS2microflower electrode exhibited an areal capacitance of 70.98 mF cm 2 at 5 mV s 1. On the other hand,the rGO-FeS2 hybrid microsphere electrode exhibited an enhanced areal capacitance of 112.41 mF cm 2 atthe same scan rate with an excellent capacitance retention of 90% over 10,000 cycles. The improvedelectrochemical performance of the rGO-FeS2 hybrid material is due mainly to its improved electricalconductivity, high surface area indicating an enhanced electron, and ion transfer mechanism. This studysuggests that the rGO-FeS2 hybrid electrode material has potential applications in energy storage devices.