Conductive silver nanowires-fenced carbon cloth fibers-supported layered double hydroxide nanosheets as a flexible and binder-free electrode for high-performance asymmetric supercapacitors

Sekhar, S. Chandra,Nagaraju, Goli,Yu, Jae Su Elsevier 2017 Nano energy Vol.36 No.-

<P><B>Abstract</B></P> <P>Silver nanowires (Ag NWs) have attracted particular interest in the development of various electronic and energy storage devices due to their one-dimensional structure, good conductivity, fast charge transportation and direct contact to the current collector. Herein, we have successfully deposited the binder-free nickel-cobalt layered double hydroxide nanosheets on Ag NWs-fenced carbon cloth (NC LDH NSs@Ag@CC) by a facile electrochemical deposition method with a chronoamperometry voltage of −1.0V for 120s. The electrically conductive and superhydrophilic nature of the hybrid nanocomposite electrode led to relatively high areal capacitance (1133.3 mF cm<SUP>−2</SUP> at 1mAcm<SUP>−2</SUP>) and good cycling stability (80.47% after 2000 cycles) compared to the electrode prepared without Ag NWs. Using such hierarchical NC LDH NSs@Ag@CC as a positive electrode, we further fabricated a flexible asymmetric supercapacitor (ASC) with activated carbon coated CC as a negative electrode. The as-assembled ASC exhibited maximum operational potential window of 1.6V, high areal capacitance of 230.2 mF cm<SUP>−2</SUP> and excellent cycling stability of 88.1% with remarkable energy densities at all the charge-discharge conditions (78.8 μWh cm<SUP>−2</SUP> at the power density of 785 μW cm<SUP>−2</SUP> and 40 μWh cm<SUP>−2</SUP> at the high power density of 12.1mWcm<SUP>−2</SUP>, respectively)</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conductive Ag NWs are uniformly decorated on carbon cloth fibers (Ag@CC). </LI> <LI> The highly conductive features and hydrophilicity of Ag@CC induce the dense growth of NC LDH NSs. </LI> <LI> Ag NWs provide the effective pathways for electron transportation during the redox process of NC LDH NSs. </LI> <LI> The areal capacitance of the electrode with Ag NWs is 2.3 times higher than the electrode without Ag NWs. </LI> <LI> The assembled asymmetric supercapacitor delivers high energy and power densities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Birnessite-type MnO₂ nanosheet arrays with interwoven arrangements on vapor grown carbon fibers as hybrid nanocomposites for pseudocapacitors

Sekhar, S. Chandra,Nagaraju, Goli,Cha, Sung Min,Yu, Jae Su The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.48

<▼1><P>A cost-effective composite electrode featuring MnO2 NSAs@VCFs exhibits good electrochemical performance as an electroactive material for pseudocapacitors.</P></▼1><▼2><P>Manganese dioxide nanosheet arrays with interconnected arrangements are easily synthesized on vapor grown carbon fibers (MnO2 NSAs@VCFs) by a simple wet-chemical method at low temperature. The conductive nature of the VCFs serves as a scaffold and easily reduces potassium permanganate species for the formation of hierarchical MnO2 NSAs@VCFs. When utilized as an electroactive material for pseudocapacitors, the sophisticated configuration of the nanocomposite provides an effective electrochemical activity and an electron pathway for higher electrochemical performance in 1 M Na2SO4 aqueous solution. The hierarchical MnO2 NSAs@VCFs exhibit a maximum specific capacitance of 115.3 F g<SUP>−1</SUP> at a current density of 0.5 A g<SUP>−1</SUP> with an excellent cycling stability of 85.6% after 2000 cycles at a current density of 5 A g<SUP>−1</SUP>. Such facile and cost-effective fabrication of a metal oxide nanocomposite with improved electrochemical performance allows it to be considered as a promising electroactive material for energy storage devices.</P></▼2>

Hierarchically Designed Ag@Ce₆Mo₁₀O₃₉ Marigold Flower-Like Architectures: An Efficient Electrode Material for Hybrid Supercapacitors

Sekhar, S. Chandra,Nagaraju, Goli,Ramulu, Bhimanaboina,Yu, Jae Su American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.43

<P>We facilely prepared silver nanoparticle-decorated Ce<SUB>6</SUB>Mo<SUB>10</SUB>O<SUB>39</SUB> marigold flower-like structures (Ag NPs@CM MFs) for use as an effective positive material in hybrid supercapacitors (HSCs). With the aid of ethylenediaminetetraacetic acid (EDTA) as a chelating agent, self-assembled CM MFs were synthesized by a single-step hydrothermal method. When the electrochemical properties were tested in an aqueous alkaline electrolyte, the synthesized CM MFs with 0.15 g of EDTA exhibited a relatively high charge storage property (55.3 μA h/cm<SUP>2</SUP> at 2 mA/cm<SUP>2</SUP>) with a battery-type redox behavior. The high capacity performance is mainly because of the large surface area of the CM MFs, and the hierarchically connected nanoflakes provide wide open wells for rapid accessibility of electrolyte ions and enable fast transportation of electrons. A further improvement in electrochemical performance was achieved (62 μA h/cm<SUP>2</SUP> at 2 mA/cm<SUP>2</SUP>) by decorating Ag NPs on the surface of the CM MFs (i.e., Ag NPs@CM MFs), which is attributed to the increased electric conductivity. Considering the synergistic effect and the high electrochemical activity, Ag NPs@CM MFs were further employed as an effective positive electrode for the fabrication of pouch-type HSC with porous carbon (negative electrode) in an alkaline electrolyte. The HSC exhibited a high cell potential (1.5 V) with maximum energy and power densities of 0.0183 mW h/cm<SUP>2</SUP> and 10.237 mW/cm<SUP>2</SUP>, respectively. The potency of HSC in practical applications was also demonstrated by energizing red and yellow light-emitting diodes as well as a three-point pattern torch light.</P> [FIG OMISSION]</BR>

Synthesis of Triazoloquinoxalines as Antitubercular Agents

Sekhar, Kondapalli Venkata Gowri Chandra,Rao, Vajja Sambasiva,Kumar, Dalip Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.8

1,2,4-Triazoles and quinoxalines were found to display various pharmacological activities. Hence a series of 1-aryl-4-methyl-1,2,4-triazolo[4,3-a]quinoxalines were synthesized. Due to various advantages of organic reactions under solvent-free conditions these compounds were developed using iodobenzene diacetate under solvent-free conditions. The synthesized compounds were characterized by elemental microanalysis, infrared spectroscopy, $^1H$ NMR, $^{13}C$ NMR and HRMS. All the synthesized compounds were investigated for their antitubercular activity and 5g was found to the most active compound.

Trust Predicated Routing Framework with Optimized Cluster Head Selection using Cuckoo Search Algorithm for MANET

Sekhar, J. Chandra,Prasad, Ramineni Sivarama The Institute of Electronics and Information Engin 2015 IEIE Transactions on Smart Processing & Computing Vol.4 No.2

This paper presents a Cuckoo search algorithm to secure adversaries misdirecting multi-hop routing in Mobile ad hoc networks (MANETs) using a robust Trust Predicated Routing Framework with an optimized cluster head selection. The clustering technique designed in this framework leads to efficient routing in MANETs. The heavy work load in the node causes an energy drop in cluster head, which leads to re-clustering of the group, and another cluster head is selected to avoid packet loss during data transmission. The problem in the re-clustering process is that the overall efficiency of the routing process is reduced and the processing time is increased. A Cuckoo search based optimization algorithm is proposed to solve the problem of re-clustering by selecting the secondary cluster head within the initially formed cluster group and eliminating the reclustering process. The proposed framework enables a node to select a reliable and secure route for MANET and the performance can be evaluated by comparing the simulated results with the AODV routing protocol, which shows that the performance of the proposed routing protocol are improved significantly.

Doping effects of hexagonal manganitesEr1−xYxMnO3with triangular spin structure

Sekhar, M. Chandra,Lee, Seongsu,Choi, Gwangho,Lee, Changhee,Park, J.-G. American Physical Society 2005 Physical review. B, Condensed matter and materials Vol.72 No.1

Efficacy of pushover analysis methodologies: A critical evaluation

Sekhar Chandra Dutta,Suvonkar Chakroborty,Anusrita Raychaudhuri 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.3

Various Pushover analysis methodologies have evolved as an easy as well as designersfriendly alternative of nonlinear dynamic analysis for estimation of the inelastic demands of structures under seismic loading for performance based design. In fact, the established nonlinear dynamic analysis to assess the same, demands considerable analytical and computational background and rigor as well as intuitive insight into inelastic behavior for judging suitability of the results and its interpretation and hence may not be used in design office for frequent practice. In this context, the simple and viable alternative of Pushover analysis methodologies can be accepted if its efficacy is thoroughly judged over all possible varieties of the problems. Though this burning issue has invited some research efforts in this direction, still a complete picture evolving very clear guidelines for use of these alternate methodologies require much more detailed studies, providing idea about how the accuracy is influenced due to various combinations of basic parameters regulating inelastic dynamic response of the structures. The limited study presented in the paper aims to achieve this end to the extent possible. The study intends to identify the range of applicability of the technique and compares the efficacy of various alternative Pushover analysis schemes to general class of problems. Thus, the paper may prove useful in judicial use of Pushover analysis methodologies for performance based design with easonable accuracy and relative ease.

Solvent Free Microwave Accelerated Synthesis of Heterocyclic Thiazolidin-4-ones as Antimicrobial and Antifungal Agents

Sekhar, Kondapalli Venkata Gowri Chandra,Rao, Vajja Sambasiva,Reddy, Aravalli Satish,Sunandini, Ravada,Satuluri, V S A Kumar Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.5

A simple and efficient method has been developed for conversion of arenecarbaldehyde-3-methylquinoxalin-2-ylhydrazones to 3-(2-methylquinoxalin-3-yl)-2-(substitutedphenyl)thiazolidin-4-ones in good yields using microwave irradiation technique on silica as solid support under solvent free conditions. The synthesized compounds were characterized by elemental microanalysis, infrared spectroscopy, $^1H$ NMR, and mass spectroscopy. All the synthesized thiazolidinones were investigated for their antimicrobial and antifungal activities. The results of the biological activities revealed that the compounds 3b, 3d, 3f and 3h exhibited excellent antibacterial activities while 3d and 3h exhibited good antifungal activity.

Electrical and electronic properties of nitrogen doped amorphous carbon (a-CNx) thin films

Sekhar C. Ray,W. Mbiombi,P. Papakonstantinou 한국물리학회 2014 Current Applied Physics Vol.14 No.12

Nitrogen-doped amorphous carbon thin films (a-CNx) were prepared on silicon substrate by pulsed laser deposition process using methane (CH4) and nitrogen (N2) as source gas. The electrical properties of a- CNx films changes with nitrogen concentration in the film structure. The intensity ratio of the D and G peak (ID/IG) increases with higher nitrogen concentration, which means that sp2-clusters were formed in these films and is responsible for the enhancement of conductivity of the a-CNx films. We observed that the amorphous carbon (a-C) films becoming more graphitic in nature yielding higher conductivity/lower resistivity with increase of nitrogen concentration. Electron field emission result shows that the emission current density enhances with nitrogen doping that indicates the useful in electron field emission devices application.

Compliance, Quality, and Appropriateness of Individualized Early Intervention Plans : Analysis and Issues

Sekhar S. Pindiprolu,Mark S. Innocenti KOREA INSTITUTE FOR SPECIAL EDUCATION 2005 The Asia-Pacific Journal of Inclusive Education Vol.2 No.-

individualized early intervention plans (referred to as Plans) are required in the United States (U.S.) for young children with disabilities. In this study, individual early intervention plans (i.e., Individualized Family Service Plans or IFSPs and Individualized Education Programs or IEPs) from a western U.S. state were examined for their compliance, quality, and appropriateness. A total of 127 IFSPs and 244 IEPs were obtained from five early intervention programs and six local education agency preschool special education programs as part of a statewide evaluation of early intervention services. Compliance was measured by noting the presence of mandated components, as specified in the Individuals with Disabilities Education Act, in the Plans. Quality was measured by nothing the presence of components advocated by professionals as best practices in the literature. Further, the goals/outcomes and objectives were coded for their quality using an adapted evaluation criteria (Notari & Bricker, 1990; Notari and Shuster, 1994). Appropriateness was measured in terms of the relationship between the childs classification and goals/outcome domains listed on the Plans. Results suggest that (a) the Plans, in general, were in compliance with the mandated components, (b) there were discrepancies in the quality of various aspects of the Plans, and (c) the goal/outcomes were congruent with the childrens disability classification. Issues for improving the quality of the Plans and the need for research demonstrating the Plans are linked to child progress are discussed.