Papers by kowsik sambath kumar
ACS Omega
MXenes are the class of two-dimensional transition metal carbides and nitrides that exhibit uniqu... more MXenes are the class of two-dimensional transition metal carbides and nitrides that exhibit unique properties and are used in a multitude of applications such as biosensors, water purification, electromagnetic interference shielding, electrocatalysis, supercapacitors, and so forth. Carbide-based MXenes are being widely explored, whereas investigations on nitride-based ones are seldom. Among the nitride-based MXenes obtained from their MAX phases, only Ti 4 N 3 and Ti 2 N are reported so far. Herein, we report a novel synthesis of V 2 NT x (T x is the surface termination) obtained by the selective removal of "Al" from V 2 AlN by immersing powders of V 2 AlN in the LiF−HCl mixture (salt−acid etching) followed by sonication to obtain V 2 NT x (T x = −F, −O) MXene which is then delaminated using the dimethyl sulfoxide solvent. The V 2 NT x MXene is characterized by Xray diffraction studies, field emission scanning electron microscope imaging, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope imaging. Supercapacitor electrodes are prepared using V 2 NT x MXenes and their electrochemical performances are examined by cyclic voltammetry, galvanostatic charge/discharge measurement, and electrochemical impedance spectroscopy. The V 2 NT x MXene electrode exhibits a specific capacitance of 112.8 F/g at a current density of 1.85 mA/cm 2 with an energy and power density of 15.66 W h/kg and 3748.4 W/kg, respectively, in 3.5 M KOH aqueous electrolyte. The electrode exhibits an excellent capacitance retention of 96% even after 10,000 charge/discharge cycles. An asymmetric supercapacitor fabricated with V 2 NT x as a negative electrode and Mn 3 O 4 nanowalls as a positive electrode helps obtain a cell voltage of 1.8 V in aqueous KOH electrolyte.
Nanoscale
Metal–organic frameworks are emerging players in the fabrication of flexible energy storage devic... more Metal–organic frameworks are emerging players in the fabrication of flexible energy storage devices to power flexible and wearable electronics.
Advanced Electronic Materials
Journal of Microelectromechanical Systems
Journal of Materials Chemistry A
Uncovering the mechanism behind the increase in capacitance of a 2D WS2 supercapacitor electrode ... more Uncovering the mechanism behind the increase in capacitance of a 2D WS2 supercapacitor electrode upon cycling using KPFM analysis.
Nanoscale Horizons
The synthesis routes and the electrochemical performance evaluation of transition metal dichalcog... more The synthesis routes and the electrochemical performance evaluation of transition metal dichalcogenide (TMD) based supercapacitor electrodes are discussed.
ACS Omega
Emerging flexible and wearable electronic devices necessitates the development of fiber-type ener... more Emerging flexible and wearable electronic devices necessitates the development of fiber-type energy storage devices to power them. Supercapacitors received great attention for applications in flexible and wearable devices due to their scalability, safety, and miniature size. Herein, we report the fabrication of a flexible supercapacitor using manganese(II,III) oxide (Mn 3 O 4) nanowalls (NWs) grown by electrochemical deposition on carbon fiber (CF) as electrode-active material. Here, CF serves as both a substrate for the growth of Mn 3 O 4 NWs and a current collector for making a lightweight supercapacitor. Two-dimensional Mn 3 O 4 NWs were uniformly grown on CF with high surface coverage. A three-dimensional nanostructured electrode is obtained using these individual two-dimensional Mn 3 O 4 NWs. The Mn 3 O 4 NWs grown on CF are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. A symmetric sandwich-type supercapacitor is fabricated using two-dimensional Mn 3 O 4 NW electrodes in an aqueous 1 M Na 2 SO 4 electrolyte. The Mn 3 O 4 NW supercapacitor electrode exhibits a specific capacitance of 300.7 F g −1 at a scan rate of 5 mV s −1. The assembled symmetric sandwich-type supercapacitor displayed high flexibility even at a bending angle of 180°without altering its performance. The Mn 3 O 4 NW supercapacitor also displayed a long cycle life of 7500 cycles with 100% capacitance retention.
Nanotechnology
Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due... more Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their inherently low energy density remains a great challenge. The high-performance supercapacitors utilize large electrode surface area for electrochemical double-layer capacitance and/or pseudocapacitance. To enhance the performance of supercapacitors, various strategies have been adopted such as electrode nanostructuring, hybrid electrode designs using nanocomposite electrodes and hybrid supercapacitor (HSC) configurations. Nanoarchitecturing of electrode-active materials is an effective way of enhancing the performance of supercapacitors as it increases the effective electrode surface area for enhanced electrode/electrolyte interaction. In this review, we focus on the recent developments in the novel electrode materials and various hybrid designs used in supercapacitors for obtaining high specific capacitance and energy density. A family of electrode-active materials including carbon nanomaterials, transition metal-oxides, transition metal-nitrides, transition metal-hydroxides, electronically conducting polymers, and their nanocomposites are discussed in detail. The HSC configurations for attaining enhanced supercapacitor performance as well as strategies to integrate with other microelectronic devices/ wearable fabrics are also included.
Biosensors, Jan 11, 2018
Adverse cardiac events are a major cause of late-stage drug development withdrawals. Improved in ... more Adverse cardiac events are a major cause of late-stage drug development withdrawals. Improved in vitro systems for predicting cardiotoxicity are of great interest to prevent these events and to reduce the expenses involved in the introduction of cardiac drugs into the marketplace. Interdigitated electrodes (IDEs) affixed with a culture well provide a simple, suitable solution for in vitro analysis of cells because of their high sensitivity, ease of fabrication, and label-free, nondestructive analysis. Culturing human pluripotent stem cell differentiated cardiomyocytes onto these IDEs allows for the use of the IDE⁻cell combination in predictive toxicity assays. IDEs with smaller interdigitated distances allow for greater sensitivity, but typically require cleanroom fabrication. In this communication, we report the definition of a simple IDE geometry on a printed nanostructured substrate, demonstrate a Cellular Index () increase from 0 to 7.7 for human cardiomyocytes, and a decrease i...
Advanced science (Weinheim, Baden-Wurttemberg, Germany), 2018
Wearable electronic devices represent a paradigm change in consumer electronics, on-body sensing,... more Wearable electronic devices represent a paradigm change in consumer electronics, on-body sensing, artificial skins, and wearable communication and entertainment. Because all these electronic devices require energy to operate, wearable energy systems are an integral part of wearable devices. Essentially, the electrodes and other components present in these energy devices should be mechanically strong, flexible, lightweight, and comfortable to the user. Presented here is a critical review of those materials and devices developed for energy conversion and storage applications with an objective to be used in wearable devices. The focus is mainly on the advances made in the field of solar cells, triboelectric generators, Li-ion batteries, and supercapacitors for wearable device development. As these devices need to be attached/integrated with the fabric, the discussion is limited to devices made in the form of ribbons, filaments, and fibers. Some of the important challenges and future di...
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Papers by kowsik sambath kumar