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Papers by Ramalakshmi Mariappan
Scientific Reports, 2020
Long–term cycling performance of electrodes for application in supercapcitor has received large r... more Long–term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g−1 at 1 A g−1) with capacity retention of 96% after 7500 cycles at 5 A g−1. Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g−1 and energy density of 25 Wh kg−1 at a power density of 499 W kg−1 along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x...
Journal of Power Sources, 2019
Journal of Materials Science: Materials in Electronics, 2017
exhibit an excellent discharge capacity of 138.4 mA h g −1 at 1 C rate. The porous LNMO microcube... more exhibit an excellent discharge capacity of 138.4 mA h g −1 at 1 C rate. The porous LNMO microcubes in supercapacitor was exhibited a maximum specific capacity of 294 F g −1 at 0.75 A g −1 with an excellent specific capacitance retention of 97% after 1000 cycles. The described porous LNMO microcubes are highly suitable electrode material for energy storage applications.
November 2016, 2016
Polymeric inorganic nanocomposites have received considerable attention because of their potentia... more Polymeric inorganic nanocomposites have received considerable attention because of their potential application in diverse areas, including papermaking industries. To develop novel filler materials to improve important paper properties, polyacrylamide (PAM)-coated nano-calcium carbonate (CaCO3) nanocomposite fillers were synthesized and studied for their chemical and morphological characteristics. The effect of PAM-modified CaCO3 nanofillers on properties of paper made with bagasse-based pulp was evaluated and compared with papers made with pristine nano-CaCO3 fillers. The Fourier transform infrared spectroscopy results confirmed the attachment of PAM/CaCO3 nanocomposites with the cellulosic fiber matrix. The scanning electron microscope and light microscopic images confirmed that the PAM-modified CaCO3 fillers deposited larger aggregated clusters of particles on the fiber surfaces more firmly, which caused the improved paper properties. The surface and the optical properties of the ...
Analytica Chimica Acta, 2019
Analytica Chimica Acta, 2018
Sensors and Actuators B: Chemical, 2017
RSC Advances, 2016
Tunable magnetic and electrocatalytic characteristics of α-Fe2O3 nanostructures were fabricated b... more Tunable magnetic and electrocatalytic characteristics of α-Fe2O3 nanostructures were fabricated by tapping saponin induced anisotropic growth, demonstrated excellent electrocatalytic activity towards dopamine and uric acid with wider potential gap.
Sensors and Actuators B: Chemical, 2016
Abstract Acicular 1D iron oxide nanostructures such as needles, nanorods, and nanowires are attra... more Abstract Acicular 1D iron oxide nanostructures such as needles, nanorods, and nanowires are attracted much attention owing to their enhanced optical, magnetic, catalytic and mechanical properties over spherically shaped nanoparticles. In this article, we have reported the highly crystalline monodispersed thermally stable γ-Fe 2 O 3 nanosphere (20 nm) and γ-Fe 2 O 3 nanoleaves (8 μm) and FeO nanospheres (20 nm) synthesis using a facile nanoarchitecturing biosurfactant method. Characteristics of the iron oxide nanostructures were examined with field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimeteric analysis/differential thermogravimetric analysis (TG/DTA), fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and cyclic voltammetry (CV) electrochemical analysis. Taking advantage of the saponin with big polar head and long hydrocarbon chain, it has become possible to template the synthesis of γ-Fe 2 O 3 nanosphere and Aloe Vera Leaf (AVL) like nanostructures controlling the reaction time and Sapinduss Mukkorossi Fruit Extract (SMFE) concentration. The satellite peaks appeared at 718.5 eV and 716 eV respectively and XRD confirmed the formed γ-Fe 2 O 3 nanodots are unidirectionally colloid and coalescence via 303 plane to form γ-Fe 2 O 3 nanoleaves at lower surfactant, however at higher surfactant FeO spheres. Defect free γ-Fe 2 O 3 nanoleaves demonstrates a higher magnetization of 13.8–9 emu/g due to the absence of coherent rotation of the magnetic moment caused by the larger width of nanoleaves. It was revealed that the γ-Fe 2 O 3 nanoleaves and γ-Fe 2 O 3 nanospheres exhibite the uric acid oxidation at a reduced potential of 303 ± 3 mV with 150% and 80% enhanced electrocatalytic current respectively than GCE. This facile synthetic approach offers a greener alternative route for the synthesis of iron oxide nanostructures that are devoid of cellular and toxic chemical components. The synthesized nanomateials will find usage in magnetic storage devices, biomedical and electrocatalytic biosensor fields.
Powder Technology, 2014
The 3-Aminopropyltriethoxy silane (APTES) coated magnetite nanopowders were prepared as carriers ... more The 3-Aminopropyltriethoxy silane (APTES) coated magnetite nanopowders were prepared as carriers for anticancer drug "Curcumin" through the modified controlled chemical co-precipitation method using Oleic acid as the apt surfactant to attain ultrafine, nearly spherical and well-dispersed Fe 3 O 4 magnetic nanoparticles. The APTES coated and uncoated Fe 3 O 4 nanoparticles were characterized by XRD, FE-SEM, FT-IR, Raman and VSM techniques. The size of the Fe 3 O 4 nanoparticles and their distribution were determined by particle size analyzer. TEM results show that the average particle size is 15 nm and the particles are homogeneously dispersed which is corroborating well with the FE-SEM images. The room temperature VSM measurements showed that magnetic particles were superparamagnetic characteristics. The amount of APTES bound to the iron oxide nanoparticles were estimated by thermogravimetric analysis (TGA) and the bonding of APTES to the iron oxide nanoparticles was confirmed by FT-IR and Raman analysis. Drug loading and release profile was studied through UV-Vis Spectrophotometer. The Curcumin drug binding on to the amino moiety of APTES-Fe 3 O 4 nanoparticle was also confirmed through CLSM and FT-IR spectroscopic techniques. Rapid curcumin drug loading in 2 hrs and the controlled drug release in 1 hr 15% and in 48 hrs 80% drug release were observed, which is applicable to in-vivo applications. The present findings show that the APTES-Fe 3 O 4 nanoparticles are promising for targeted curcumin drug delivery applications.
Journal of Solid State Electrochemistry, 2013
For the first time, solid solutions of LiMn 2-X Mo X O 4 nanoparticles were synthesized by combus... more For the first time, solid solutions of LiMn 2-X Mo X O 4 nanoparticles were synthesized by combustion method at 700°C in air. The synthesized LiMn 2-X Mo X O 4 (X=0.0-0.2) nanoparticles were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy (FT-IR), Field emission-scanning electron microscopy, and Particle size analysis. The unit-cell constant is increasing from 8.237 to 8.293 Å with the increase of Mo, the presence of Mo at X≤ 0.05 in LiMn 2-X Mo X O 4 nanoparticles retained the spinel structure (Fd-3m), whereas on increasing the Mo (X ≥ 0.05 %), the ordering of Li + ions in both octahedral and tetrahedral cationic position leads to the lowering of symmetry (P4 1 32). On increasing the Mo content, prominent peak splitting and broadening are observed at 600-500 and 830 cm −1 for Li-Mn-O and MoO respectively in the FT-IR spectra. The TG/DTA spectrum reveals that the convenient formation of Li mangano-molybdate is at 700°C. The voltammograms of all the samples show two redox peaks centered around 4 V except for the sample with higher Mo doping (X=0.2). The sample with X=0.03 shows higher redox peak current values. A marginal increase of 146 Ω R ct value was found for the LiMn 1.97 Mo 0.03 O 4 nanomaterial after 10th cycle which is rather high for the rest of the materials. A discharge capacity retention of 88 % at 50th cycle is observed for X=0.03 sample, while the other samples exhibit drastically reduced capacity. The LiMn 1.97 Mo 0.03 O 4 nanoparticle can able to deliver higher and constant discharge capacity, and it may be a good alternative for the existing cathode materials.
Journal of Electroanalytical Chemistry, 2014
Solid solutions of LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanoparticles were synt... more Solid solutions of LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanoparticles were synthesized by ureaglycerol combustion method. The undoped/doped LiMn 2 O 4 nanoparticles were characterized by XRD, FT-IR, FE-SEM and electrochemical techniques. The LiMn 2ÀXÀY Ti X Fe Y O 4 spinel shows higher lattice constant of 8.279 Å at X = 0.10 Ti doping, while the Ti and Fe dual doped exhibits a = 8.212 Å. No obvious impurity phases/structural changes are observed in all the synthesized LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanomaterials. The appearance of FT-IR band at $603 cm À1 evidenced the formation of Li-Ti-Mn-O bonds. Increased peak current is observed for the compound LiMn 1.90 Ti 0.05 Fe 0.05 O 4 attributable to the improved Li + diffusion caused by the reduced R ct values and path lengths. LiMn 1.90 Ti 0.05 Fe 0.05 O 4 exhibits a very small increase of 73 X cm 2 R ct value even after 100th cycle, while that of 1122 X cm 2 for LiMn 2 O 4. A high specific discharge capacity of 125 mA h g À1 is retained even after 100th cycle effected by presence of Ti & Fe in the Mn site. The LiMn 1.90 Ti 0.05 Fe 0.05 O 4 nanoparticles sample exhibit decent capacity retention of 90% at 100th cycle, and it can be able to deliver higher and constant discharge capacity and it may be a good alternative for the existing cathode materials.
Industrial & Engineering Chemistry Research, 2013
A heterogeneous catalyst has been derived from a waste material of fresh water bivalve mollusk (i... more A heterogeneous catalyst has been derived from a waste material of fresh water bivalve mollusk (i.e., Margaritifera falcata outer shell) for the transesterification of palm oil. The shell was washed, crushed, ground, and calcined at 850°C to derive active CaO catalyst. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), and differential thermal analysis/ thermogravimetric (DT/TG) analysis. The DT/TG analysis showed the decomposition of calcium carbonate present in the shell at 780°C. The XRD peaks for calcined shell were observed at 2θ = 32.22°, 53.53°, and 64.03°characteristics of CaO and showed high crystallinity. The textural structure of shell can be observed from the SEM images indicated that the structure of shell changed with calcination temperature. The FTIR absorption bands of the calcined shell were observed at 1471, 1090, and 874 cm −1 , which are attributed to the decrease of the reduced mass of the functional group attached to the CO 3 2ions. The waste driven (bivalve mollusk outer shell) catalyzed palm oil transesterification resulted in a high yield (90%) and conversion (98.2%) of biodiesel that was obtained at a 10:1 (methanol to oil) molar ratio and 4 wt % catalyst concentration at 60°C in 5 h reaction time. The conversion of biodiesel was determined by 1 H NMR.
![Research paper thumbnail of [Bmim][TfO] ionic liquid-assisted oriented growth of Co3O4 nanoworms](https://attachments.academia-assets.com/89622497/thumbnails/1.jpg)
](Materials Research Bulletin, 2013
Scientific Reports, 2020
Long–term cycling performance of electrodes for application in supercapcitor has received large r... more Long–term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g−1 at 1 A g−1) with capacity retention of 96% after 7500 cycles at 5 A g−1. Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g−1 and energy density of 25 Wh kg−1 at a power density of 499 W kg−1 along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x...
Journal of Power Sources, 2019
Journal of Materials Science: Materials in Electronics, 2017
exhibit an excellent discharge capacity of 138.4 mA h g −1 at 1 C rate. The porous LNMO microcube... more exhibit an excellent discharge capacity of 138.4 mA h g −1 at 1 C rate. The porous LNMO microcubes in supercapacitor was exhibited a maximum specific capacity of 294 F g −1 at 0.75 A g −1 with an excellent specific capacitance retention of 97% after 1000 cycles. The described porous LNMO microcubes are highly suitable electrode material for energy storage applications.
November 2016, 2016
Polymeric inorganic nanocomposites have received considerable attention because of their potentia... more Polymeric inorganic nanocomposites have received considerable attention because of their potential application in diverse areas, including papermaking industries. To develop novel filler materials to improve important paper properties, polyacrylamide (PAM)-coated nano-calcium carbonate (CaCO3) nanocomposite fillers were synthesized and studied for their chemical and morphological characteristics. The effect of PAM-modified CaCO3 nanofillers on properties of paper made with bagasse-based pulp was evaluated and compared with papers made with pristine nano-CaCO3 fillers. The Fourier transform infrared spectroscopy results confirmed the attachment of PAM/CaCO3 nanocomposites with the cellulosic fiber matrix. The scanning electron microscope and light microscopic images confirmed that the PAM-modified CaCO3 fillers deposited larger aggregated clusters of particles on the fiber surfaces more firmly, which caused the improved paper properties. The surface and the optical properties of the ...
Analytica Chimica Acta, 2019
Analytica Chimica Acta, 2018
Sensors and Actuators B: Chemical, 2017
RSC Advances, 2016
Tunable magnetic and electrocatalytic characteristics of α-Fe2O3 nanostructures were fabricated b... more Tunable magnetic and electrocatalytic characteristics of α-Fe2O3 nanostructures were fabricated by tapping saponin induced anisotropic growth, demonstrated excellent electrocatalytic activity towards dopamine and uric acid with wider potential gap.
Sensors and Actuators B: Chemical, 2016
Abstract Acicular 1D iron oxide nanostructures such as needles, nanorods, and nanowires are attra... more Abstract Acicular 1D iron oxide nanostructures such as needles, nanorods, and nanowires are attracted much attention owing to their enhanced optical, magnetic, catalytic and mechanical properties over spherically shaped nanoparticles. In this article, we have reported the highly crystalline monodispersed thermally stable γ-Fe 2 O 3 nanosphere (20 nm) and γ-Fe 2 O 3 nanoleaves (8 μm) and FeO nanospheres (20 nm) synthesis using a facile nanoarchitecturing biosurfactant method. Characteristics of the iron oxide nanostructures were examined with field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimeteric analysis/differential thermogravimetric analysis (TG/DTA), fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and cyclic voltammetry (CV) electrochemical analysis. Taking advantage of the saponin with big polar head and long hydrocarbon chain, it has become possible to template the synthesis of γ-Fe 2 O 3 nanosphere and Aloe Vera Leaf (AVL) like nanostructures controlling the reaction time and Sapinduss Mukkorossi Fruit Extract (SMFE) concentration. The satellite peaks appeared at 718.5 eV and 716 eV respectively and XRD confirmed the formed γ-Fe 2 O 3 nanodots are unidirectionally colloid and coalescence via 303 plane to form γ-Fe 2 O 3 nanoleaves at lower surfactant, however at higher surfactant FeO spheres. Defect free γ-Fe 2 O 3 nanoleaves demonstrates a higher magnetization of 13.8–9 emu/g due to the absence of coherent rotation of the magnetic moment caused by the larger width of nanoleaves. It was revealed that the γ-Fe 2 O 3 nanoleaves and γ-Fe 2 O 3 nanospheres exhibite the uric acid oxidation at a reduced potential of 303 ± 3 mV with 150% and 80% enhanced electrocatalytic current respectively than GCE. This facile synthetic approach offers a greener alternative route for the synthesis of iron oxide nanostructures that are devoid of cellular and toxic chemical components. The synthesized nanomateials will find usage in magnetic storage devices, biomedical and electrocatalytic biosensor fields.
Powder Technology, 2014
The 3-Aminopropyltriethoxy silane (APTES) coated magnetite nanopowders were prepared as carriers ... more The 3-Aminopropyltriethoxy silane (APTES) coated magnetite nanopowders were prepared as carriers for anticancer drug "Curcumin" through the modified controlled chemical co-precipitation method using Oleic acid as the apt surfactant to attain ultrafine, nearly spherical and well-dispersed Fe 3 O 4 magnetic nanoparticles. The APTES coated and uncoated Fe 3 O 4 nanoparticles were characterized by XRD, FE-SEM, FT-IR, Raman and VSM techniques. The size of the Fe 3 O 4 nanoparticles and their distribution were determined by particle size analyzer. TEM results show that the average particle size is 15 nm and the particles are homogeneously dispersed which is corroborating well with the FE-SEM images. The room temperature VSM measurements showed that magnetic particles were superparamagnetic characteristics. The amount of APTES bound to the iron oxide nanoparticles were estimated by thermogravimetric analysis (TGA) and the bonding of APTES to the iron oxide nanoparticles was confirmed by FT-IR and Raman analysis. Drug loading and release profile was studied through UV-Vis Spectrophotometer. The Curcumin drug binding on to the amino moiety of APTES-Fe 3 O 4 nanoparticle was also confirmed through CLSM and FT-IR spectroscopic techniques. Rapid curcumin drug loading in 2 hrs and the controlled drug release in 1 hr 15% and in 48 hrs 80% drug release were observed, which is applicable to in-vivo applications. The present findings show that the APTES-Fe 3 O 4 nanoparticles are promising for targeted curcumin drug delivery applications.
Journal of Solid State Electrochemistry, 2013
For the first time, solid solutions of LiMn 2-X Mo X O 4 nanoparticles were synthesized by combus... more For the first time, solid solutions of LiMn 2-X Mo X O 4 nanoparticles were synthesized by combustion method at 700°C in air. The synthesized LiMn 2-X Mo X O 4 (X=0.0-0.2) nanoparticles were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy (FT-IR), Field emission-scanning electron microscopy, and Particle size analysis. The unit-cell constant is increasing from 8.237 to 8.293 Å with the increase of Mo, the presence of Mo at X≤ 0.05 in LiMn 2-X Mo X O 4 nanoparticles retained the spinel structure (Fd-3m), whereas on increasing the Mo (X ≥ 0.05 %), the ordering of Li + ions in both octahedral and tetrahedral cationic position leads to the lowering of symmetry (P4 1 32). On increasing the Mo content, prominent peak splitting and broadening are observed at 600-500 and 830 cm −1 for Li-Mn-O and MoO respectively in the FT-IR spectra. The TG/DTA spectrum reveals that the convenient formation of Li mangano-molybdate is at 700°C. The voltammograms of all the samples show two redox peaks centered around 4 V except for the sample with higher Mo doping (X=0.2). The sample with X=0.03 shows higher redox peak current values. A marginal increase of 146 Ω R ct value was found for the LiMn 1.97 Mo 0.03 O 4 nanomaterial after 10th cycle which is rather high for the rest of the materials. A discharge capacity retention of 88 % at 50th cycle is observed for X=0.03 sample, while the other samples exhibit drastically reduced capacity. The LiMn 1.97 Mo 0.03 O 4 nanoparticle can able to deliver higher and constant discharge capacity, and it may be a good alternative for the existing cathode materials.
Journal of Electroanalytical Chemistry, 2014
Solid solutions of LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanoparticles were synt... more Solid solutions of LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanoparticles were synthesized by ureaglycerol combustion method. The undoped/doped LiMn 2 O 4 nanoparticles were characterized by XRD, FT-IR, FE-SEM and electrochemical techniques. The LiMn 2ÀXÀY Ti X Fe Y O 4 spinel shows higher lattice constant of 8.279 Å at X = 0.10 Ti doping, while the Ti and Fe dual doped exhibits a = 8.212 Å. No obvious impurity phases/structural changes are observed in all the synthesized LiMn 2ÀXÀY Ti X Fe Y O 4 (X = 0.0 6 X P 0.1, Y = 0.05) nanomaterials. The appearance of FT-IR band at $603 cm À1 evidenced the formation of Li-Ti-Mn-O bonds. Increased peak current is observed for the compound LiMn 1.90 Ti 0.05 Fe 0.05 O 4 attributable to the improved Li + diffusion caused by the reduced R ct values and path lengths. LiMn 1.90 Ti 0.05 Fe 0.05 O 4 exhibits a very small increase of 73 X cm 2 R ct value even after 100th cycle, while that of 1122 X cm 2 for LiMn 2 O 4. A high specific discharge capacity of 125 mA h g À1 is retained even after 100th cycle effected by presence of Ti & Fe in the Mn site. The LiMn 1.90 Ti 0.05 Fe 0.05 O 4 nanoparticles sample exhibit decent capacity retention of 90% at 100th cycle, and it can be able to deliver higher and constant discharge capacity and it may be a good alternative for the existing cathode materials.
Industrial & Engineering Chemistry Research, 2013
A heterogeneous catalyst has been derived from a waste material of fresh water bivalve mollusk (i... more A heterogeneous catalyst has been derived from a waste material of fresh water bivalve mollusk (i.e., Margaritifera falcata outer shell) for the transesterification of palm oil. The shell was washed, crushed, ground, and calcined at 850°C to derive active CaO catalyst. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), and differential thermal analysis/ thermogravimetric (DT/TG) analysis. The DT/TG analysis showed the decomposition of calcium carbonate present in the shell at 780°C. The XRD peaks for calcined shell were observed at 2θ = 32.22°, 53.53°, and 64.03°characteristics of CaO and showed high crystallinity. The textural structure of shell can be observed from the SEM images indicated that the structure of shell changed with calcination temperature. The FTIR absorption bands of the calcined shell were observed at 1471, 1090, and 874 cm −1 , which are attributed to the decrease of the reduced mass of the functional group attached to the CO 3 2ions. The waste driven (bivalve mollusk outer shell) catalyzed palm oil transesterification resulted in a high yield (90%) and conversion (98.2%) of biodiesel that was obtained at a 10:1 (methanol to oil) molar ratio and 4 wt % catalyst concentration at 60°C in 5 h reaction time. The conversion of biodiesel was determined by 1 H NMR.
Materials Research Bulletin, 2013