Browsing by Author "Priyadharsini, N"

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EFFECT OF CHELATING AGENT ON THE SOL-GEL THERMOLYSIS SYNTHESIS OF LINIPO4 AND ITS ELECTROCHEMICAL PROPERTIES FOR HYBRID CAPACITORS
(Elsevier, 2018-08) Priyadharsini, N; Rupa Kasturi, P; Shanmugavani, A; Surendran, S; Shanmugapriya, S; Kalai Selvan, R
The present work reports the preparation of olivine structured LiNiPO4 nanoparticles through sol-gel thermolysis method using three different chelating agents of citric acid (LiNi-C), l-ascorbic acid (LiNi-A) and D-sorbitol (LiNi-S). The flame temperature and enthalpy change of each reaction using the chelating agent is calculated. Further, the sharp X-ray diffraction peak reveals the phase pure and high crystalline nature of the prepared LiNiPO4 nanoparticles with the space group of Pnma (62) irrespective of the chelating agents. The four possible fundamental vibrations of phosphate anion PO43− are revealed through Fourier Transform Infrared Spectroscopy (FTIR) studies. The presence of elements such as Ni, P and O and its valence state is identified through X-Ray Photoelectron Spectroscopy analysis. The spherical shape particles with the uniform size distribution of LiNi –S is observed than the LiNi-C, LiNi-A particles through FESEM analysis. The redox peaks and plateau regions in the cyclic voltammetry (CV) and Galvanostatic charge-discharge (GCD) profiles infer the dominance of battery-type charge process rather than a capacitive mechanism. As a result, LiNiPO4 exhibits a maximum specific capacitance of 417 F g−1 at 2 mV s−1 and 357 F g−1 at 1 mA cm−2 in 1 M LiOH, which enables as a suitable cathode material for hybrid supercapacitor. Also, the assembled hybrid supercapacitor delivered a high energy density of 12.5 Wh kg−1 at 200 W kg−1 as well as a longer cycle life of 89% at a current density of 1 mA cm−2 over 2000 cycles is noticed. These results infer that LiNiPO4 could be used as a novel electrode material for hybrid supercapacitor application.
GENERATION OF SUB-WAVELENGTH LONGITUDINAL MAGNETIC PROBE AND MULTIPLE SPOTS USING CIRCULARLY POLARIZED ANNULAR MULTI-GAUSSIAN BEAM
(Springer Link, 2019-11-13) Seethalakshmi, S; Udhayakumar, M; Priyadharsini, N; Rajesh, K B; Jaroszewicz, Z
Based on vector diffraction theory and inverse Faraday effect, we numerically studied the magnetization induced by a tightly focused circularly polarized annular multi-Gaussian beam. Numerical result shows that the magnetization spot as small as 0.4 λ which extends up to 8 λ can be induced for incident circularly polarized annular multi-Gaussian beam (CPAMGB). We also noted that the depth of focus of the generated magnetization spot can be very well improved up to 48 λ through suitable phase modulation to the incident CPAMGB by means of specially designed complex phase filter. Moreover, we also noted that one can generate a chain of magnetization spots of different numbers and sizes upon suitably changing the beam order of CPAMGB and radii of complex phase filter. We expect that such a study will be fruitful for experimental realization of all-optical magnetic recording, multiple magnetic particle trapping and transportation, confocal and magnetic resonance microscopy, as well as multilayer ultra-high-density magnetic storage.
NANO-SHEET-LIKE KNIPO4 AS A POSITIVE ELECTRODE MATERIAL FOR AQUEOUS HYBRID SUPERCAPACITORS
(Elsevier, 2017-08-20) Priyadharsini, N; Kalai Selvan, R
A facile sol-gel thermolysis route was adopted to synthesize KNiPO4 nano-sheets for the design of hybrid supercapacitors. The phase purity, homogeneity, and functional groups present in the synthesized KNiPO4 were characterized through X-ray diffraction and FTIR measurements. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images showed that the nano-sheet-like particles were loosely stacked. The electrochemical properties of the KNiPO4 electrode were studied in various aqueous-based electrolytes such as 1 M LiOH, 1 M NaOH, and 1 M KOH to explore their superior performances. Among these electrolytes, the KNiPO4 electrode provided a maximum specific capacity of 278 C g−1 in 1 M KOH at 5 mV s−1. A hybrid supercapacitor was fabricated using the synthesized KNiPO4 as the positive electrode and activated carbon as the negative electrode in a 1 M KOH aqueous electrolyte. The supercapacitor exhibited a specific capacitance of 48 F g−1 in 1 M KOH at 0.6 mA cm−2 and energy density of 13 Wh kg−1 at a power density of 59 W kg−1. In addition, the hybrid system retained 93% of its initial specific capacitance even after 2000 cycles. A KNiPO4-based hybrid system thus exhibits superior characteristics and hence is a promising candidate for high-performance electrochemical energy storage devices.
SENSITIVITY ENHANCEMENT OF SURFACE PLASMON RESONANCE SENSOR USING HYBRID CONFIGURATION OF 2D MATERIALS OVER BIMETALLIC LAYER OF CU–NI
(Elsevier, 2020-05-15) AlaguVibisha, G; Jeeban Kumar, Nayak; Maheswari, P; Priyadharsini, N; Nisha, A; Jaroszewicz, Z; Rajesh, K B; Rajan, Jha
This Theoretical study aims at improving the sensitivity of surface plasmon resonance biosensor under angular interrogation. We observed that the sensor configuration composed of bimetallic layer of Cu–Ni attached with 2D materials MoS2/WS2/MoSe2/WSe2/graphene enhanced the sensitivity of the sensor to a great extends. The thickness of the bimetallic layers and the number of layers of 2D materials are optimized to achieve maximum sensitivity. Numerical results shows that sensitivity as high as 480 /RIU is achieved for the well optimized bimetallic configuration consist of 35 nm of Cu and 20 nm of Ni thickness for the analyte refractive indices ranging from 1.33–1.335. Up on functionalizing the metal layers with bimolecular recognizing 2D materials, we noted that configuration with 35 nm of Cu, 15 nm of Ni with monolayer of 2D material WS2 enhanced the sensitivity as high as 426 /RIU. We expect that such a simple structure and promising results will lead the proposed sensor as a suitable and potential candidate for detecting biomolecules organic elements and other analytes.
SOL-GEL SYNTHESIS, STRUCTURAL REFINEMENT, AND ELECTROCHEMICAL PROPERTIES OF POTASSIUM MANGANESE PHOSPHATE FOR SUPERCAPACITORS
(Springer Link, 2018-01-26) Priyadharsini, N; Shanmugavani, A; Leonid, Vasylechko; Kalai Selvan, R
Using sol-gel thermolysis method, potassium manganese phosphate (a mixture of KMnPO4⋅H2O and KMnPO4 phases) was synthesized for supercapacitor applications. XRD analysis revealed phase composition and crystal structure of the prepared material. The dittmarite-type structure of KMnPO4⋅H2O as the primary phase was identified through full profile Rietveld refinement technique. The possible four normal modes of vibrations ν1(A1), ν2(E), ν3(F2), and ν4(F2) were analyzed through FTIR spectrum. Submicron-sized particles are identified using FE-SEM and TEM images. The layered structure of potassium manganese phosphate was corroborated through SAED pattern. Electrochemical performances of the mixed potassium manganese phosphate are investigated using cyclic voltammetry (CV) to identify the suitable aqueous electrolytes (1 M KOH, 1 M LiOH, and 1 M NaOH). It provides the maximum specific capacitance of 516 F g−1 at 2 mV s−1 in 1 M KOH aqueous electrolyte. The Trasatti plot revealed that the observed high specific capacitance mainly arises from the inner surface charge contribution. The electrode shows the better specific capacity of 329 F g−1 at a current density of 0.6 mA cm−2 in galvanostatic charge-discharge measurements. The electrochemical impedance spectral analysis (EIS) further corroborates that the charge-transfer resistance (Rct) is low in 1 M KOH (2.25 Ω) electrolyte than in 1 M LiOH (9.2 Ω) and 1 M NaOH (50.7 Ω) electrolytes.
SYNTHESIS AND CHARACTERIZATION OF POLYANILINE/MNWO4 NANOCOMPOSITES AS ELECTRODES FOR PSEUDOCAPACITORS (Article)
(Elsevier, 2012-03-15) Saranya, S; Kalai Selvan, R; Priyadharsini, N
Polyaniline (PAni)/MnWO4 nanocomposite was successfully synthesized by in situ polymerization method under ultrasonication and the MnWO4 was prepared by surfactant assisted ultrasonication method. The thermal stability of PAni was determined by TG/DTA (Thermo Gravimetric/ Differential thermal analysis). The structural and morphological features of PAni, MnWO4 and PAni/MnWO4 composite was analyzed using Fourier transform infrared spectrometry, X-ray diffraction (XRD), scanning electron microscope (SEM) and Transmission electron microscope (TEM) images. The electro-chemical properties of PAni, MnWO4 and its composites with different weight percentage of MnWO4 loading were studied through cyclic voltammetry (CV) for the application of supercapacitors as active electrode materials. From the cyclic voltammogram, 50% of MnWO4 impregnated PAni showed a high specific capacitance (SC) of 481 F/g than their individual counterparts of PAni (396 F/g) and MnWO4 (18 F/g). The galvanostatic charge–discharge studies indicate the in situ polymerized composite shows greater specific capacitance (475 F/g) than the physical mixture (346 F/g) at a constant discharge current of 1 mA/cm2 with reasonable cycling stability. The charge transfer resistance (Rct) of PAni/MnWO4 composite (22 ohm) was calculated using electrochemical impedance spectroscopy (EIS) and compared with its physical mixture (58 ohm).