Sumanta Kumar Karan | Pennsylvania State University (original) (raw)

Papers by Sumanta Kumar Karan

Research paper thumbnail of A Mesoporous High-Performance Supercapacitor Electrode Based on Polypyrrole Wrapped Iron Oxide Decorated Nanostructured Cobalt Vanadium Oxide Hydrate with Enhanced Electrochemical Capacitance

Industrial & Engineering Chemistry Research

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Research paper thumbnail of Polyaniline/α-Ni(OH)2/iron oxide-doped reduced graphene oxide-based hybrid electrode material

Journal of Applied Electrochemistry

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Research paper thumbnail of Fast Charging Self-Powered Wearable and Flexible Asymmetric Supercapacitor Power Cell with Fish Swim Bladder as an Efficient Natural Bio-Piezoelectric Separator

Nano Energy

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Research paper thumbnail of Salt leached viable porous Fe 3 O 4 decorated polyaniline – SWCNH/PVDF composite spectacles as an admirable electromagnetic shielding efficiency in extended Ku-band region

Composites Part B: Engineering

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Research paper thumbnail of An Approach to Fabricate PDMS Encapsulated All-Solid-State Advanced Asymmetric Supercapacitor Device with Vertically Aligned Hierarchical ZnFeCo Ternary Oxide Nanowire and Nitrogen Doped Graphene Nanosheet for High Power Device Applications

ACS Applied Materials & Interfaces, 2017

We highlight the design and fabrication of a polydimethylsiloxane (PDMS) encapsulated advanced al... more We highlight the design and fabrication of a polydimethylsiloxane (PDMS) encapsulated advanced all-solid-state asymmetric supercapacitor (ASC) device consisting of hierarchical mesoporous zinc-iron-cobalt ternary oxide (ZICO) nanowire coated nickel (Ni) foam (ZICO@Ni foam) as a promising positive electrode and nitrogen doped graphene coated Ni foam (N-G@Ni foam) as negative electrode in the presence of PVA-KOH gel electrolyte. Owing to outstanding electrochemical behavior and ultrahigh specific capacitance of ZICO (≈ 2587.4 F/g at 1 A/g) and N-G (550 F/g at 1 A/g) along with their mutual synergistic outputs, the assembled all-solid-state ASC device exhibits an outstanding energy density of ≈40.5 Wh/kg accompanied by a remarkable long-term cycle stability with ≈95% specific capacitance retention even after 5000 charge-discharge cycles. The exclusive hierarchical ZICO nanowires were synthesized by a facile two-step process comprising of a hydrothermal protocol followed by an annealing treatment on a quartz substrate. While Zn(2+) gives the stability of the oxide system, Fe and Co ions provide better electronic conductivity and capacitive response under vigorous cyclic condition. The extraordinary performance of as-fabricated ASC device resembles its suitability for the construction of advanced energy storage devices in modern electronic industries.

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Research paper thumbnail of A Facile Approach to Develop Highly Stretchable PVC/ZnSnO3 Piezoelectric Nanogenerator with High Output Power Generation for Powering Portable Electronic Devices

Industrial & Engineering Chemistry Research, 2016

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Research paper thumbnail of Single wall carbon nanohorn (SWCNH)/graphene nanoplate/poly(methyl methacrylate) nanocomposites: A promising material for electromagnetic interference shielding applications

RSC Advances

Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) na... more Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared through addition of GNP/PMMA bead into the SWCNH dispersed PMMA matrix during its polymerization.

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Research paper thumbnail of High Energy Density Ternary Composite Electrode Material Based on Polyaniline (PANI), Molybdenum trioxide (MoO3) and Graphene Nanoplatelets (GNP) Prepared by Sono-Chemical Method and Their Synergistic Contributions in Superior Supercapacitive Performance

Electrochimica Acta

ABSTRACT

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Research paper thumbnail of Single wall carbon nanohorn (SWCNH)/graphene nanoplate/poly(methyl methacrylate) nanocomposites: a promising material for electromagnetic interference shielding applications

RSC Adv., 2015

Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) na... more Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared through addition of GNP/PMMA bead into the SWCNH dispersed PMMA matrix during its polymerization.

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Research paper thumbnail of High Energy Density Ternary Composite Electrode Material Based on Polyaniline (PANI), Molybdenum trioxide (MoO3) and Graphene Nanoplatelets (GNP) Prepared by Sono-Chemical Method and Their Synergistic Contributions in Superior Supercapacitive Performance

Electrochimica Acta, 2015

ABSTRACT

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Research paper thumbnail of Carbon nanohorn-graphene nanoplate hybrid: An excellent electrode material for supercapacitor application

Journal of Applied Polymer Science, 2015

ABSTRACT This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate ... more ABSTRACT This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate (GNP) hybrid (CNGN). The well-CNH-decorated GNP-plate electrode materials show high capacitance value (≈677 F/g) and can be extensively used in new generation for energy storage. In the hybrid (CNGN), two nanofillers jointly affect the capacitance behavior and increase the capacitance value of the CNGN hybrid. Homogeneous coating of CNH over the GNP plate plays an effective role to enhance the capacitance behavior of the composite. Field emission scanning electron microscopy and high-resolution transmission electron microscopy analysis of the composite confirmed the CNH coating on the GNP plate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42118.

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Research paper thumbnail of Polymer Based Piezoelectric Nanogenerators Design for Science

Design for Science, 2016

Recently, polymer based piezoelectric nanogenerators (PNGs) devices have attracted great attentio... more Recently, polymer based piezoelectric nanogenerators (PNGs) devices have attracted great attention for harvesting mechanical energy under different small mechanical and biomechanical actions with variable amplitude and frequency available in our living environment and lots of efforts have been devoted toward realization of highly sensitive and flexible sensors. Although these devices show excellent energy harvesting performance but their low mechanical robustness limits their use in various fields of applications. In our study, we have developed a facile method that involves solution casting process and judicious control in compression molding to design and fabricate a flexible hybrid piezoelectric nanogenerator (HPNG) consisting of PVDF and AlO-rGO by integrating flexible conducting steel woven fabric electrodes. Here, we have utilized the mechanical stiffness of the steel woven fabric to make the composite nanogenerator robust as well as to serve as a charge collector. The novel PVDF/AlO-rGO pressure sensor based on flexible steel fabric shows an unprecedented shifting of open circuit output voltage to a high value of ≈ 36 V and short circuit current of ≈ 0.8 μA, corresponds to a high power density of ≈ 27.97 μW/cm3 under repeating human finger imparting condition. Also, the HPNG is exceedingly efficient to charge the capacitor in a very short time span (» 6.1 V in 96.6 sec), and exhibits high energy conversion efficiency up to » 12.47 %. Benefitting from the excellent sensing as well as output performance properties, the HPNG shows an outstanding durability of »158400 cycles and ≈1600 cycles in a cyclic compression test under sewing machine vibration and human motion conditions, respectively. This high output performance and energy conversion efficiency of HPNG enable to lit up different color of several commercial light-emitting diodes (LEDs) instantly and power up many portable electronic devices like wrist watch, calculator, speaker and, mobile LCD screen through capacitor charging. Such high performance durable HPNG flexible pressure sensor the promising candidate for various small pressure applications such as bending, twisting, foot striking, folding at elbow, sewing machine vibration, heel pressing, and jogging/walking. The developed woven fabric integrated flexible HPNG is highly desirable for large-scale application of portable and flexible electronics devices, and may open up a new platform for energy harvesting material that can covert low-frequency mechanical energy from human activity into electricity.

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Research paper thumbnail of Bio-waste onion skin as an innovative nature-driven piezoelectric material with high energy conversion efficiency

Nano Energy, 2017

Development of non-toxic, ultra-sensitive, and flexible bio-inspired piezoelectric nanogenerator ... more Development of non-toxic, ultra-sensitive, and flexible bio-inspired piezoelectric nanogenerator has become a great challenge for next generation biomedical applications. High performance organic/inorganic materials based piezoelectric nanogenerators suffer from several unavoidable problems such as complex synthesis and high toxicity. Biodegradable and biocompatible piezoelectric material is utmost needed in in-vivo condition to harvest energy for biomedical applications. Here, we report a novel bio-piezoelectric nanogenerator (BPNG) using naturally abundant self-aligned cellulose fibrous untreated onion skin (OS) as efficient piezoelectric material having piezoelectric strength of ∼ 2.8 pC/N. The fabricated OSBPNG generated output voltage, current, instantaneous power density and high piezoelectric energy conversion efficiency of ≈ 18 V, ≈ 166 nA, ≈ 1.7 μW/cm 2 , and ≈ 61.7%, respectively, and turn on 30 green LEDs by a single device under repeated com-pressive stress of ≈ 34 kPa and ≈ 3.0 Hz frequency. In addition, maximum output voltage (≈ 106 V) was achieved when 6 units are connected in series, which instantaneously turns on 73 combined LEDs (30 green, 25 blue, and 18 red). OSBPNG is highly effective during throat movement such as coughing, drinking and swallowing. Furthermore, because it works at very low pressure originating from heart pulse or beat, it could be used in pacemakers and health care units. Finally, OSBPNG successfully differentiates speech signals, indicating its potential for speech recognition.

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Research paper thumbnail of Effect of g-PVDF on enhanced thermal conductivity and dielectric property of Fe-rGO incorporated PVDF based flexible nanocomposite film for efficient thermal management and energy storage applications

RSC Advances, 2016

Here, we investigate the effect of thermal conductivity of g-crystallites of PVDF in Fe-rGO/PVDF ... more Here, we investigate the effect of thermal conductivity of g-crystallites of PVDF in Fe-rGO/PVDF nanocomposite, which are of potential use as actuators and temperature sensors for thermal management applications. The formation of g-crystallites help to increase the thermal conductivity of the nanocomposite up to 0.89 W mK À1 at low level of filler loading (3 wt%) and we showed that the thermal conductivity depends on the amount of crystalline polar g-phase in addition to filler concentration. Although thermal conductivity depends on the crystallinity of the nanocomposite, here enhancement of thermal conductivity is not related only to crystallinity, as the crystallinity is decreased compared to neat PVDF. However the thermal conductivity increases because of the generation of a higher number of g-crystallites of small size. Furthermore, the nanocomposite at low filler loading also shows high dielectric constant with low dielectric loss of the order of z57 and z0.13, respectively, at 1 kHz. Moreover, the energy storage property and its dependence on g-crystallite size reveals that the material can also exhibit superior released energy density (1.45 J cm À3) as compared to pure PVDF.

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Research paper thumbnail of Self-powered flexible Fe-doped RGO/PVDF nanocomposite: an excellent material for a piezoelectric energy harvester

Nanoscale, 2015

In this work, we report the superior piezoelectric energy harvester ability of a non-electrically... more In this work, we report the superior piezoelectric energy harvester ability of a non-electrically poled Fe-doped reduced graphene oxide (Fe-RGO)/poly(vinylidene fluoride) (PVDF) nanocomposite film prepared through a simple solution casting technique that favors the nucleation and stabilization of ≈99% relative proportion of polar γ-phase. The piezoelectric energy harvester was made with non-electrically poled Fe-RGO/PVDF nanocomposite film that gives an open circuit output voltage and short circuit current up to 5.1 V and 0.254 μA by repetitive human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar γ-phase in the PVDF, due to the electrostatic interactions among the –CH 2 –/–CF 2 – dipoles of PVDF and the delocalized π-electrons and remaining oxygen functionalities of Fe-doped RGO via ion-dipole and/or hydrogen bonding interactions. Fourier transform infrared spectroscopy (FT-IR) confirmed the nucleation of the polar γ-phase of PVDF by electrostatic interactions and Raman spectroscopy also supported the molecular interactions between the dipoles of PVDF and the Fe-doped RGO nanosheets. In addition, the nanocomposite shows a higher electrical energy density of ≈0.84 J cm −3 at an electric field of 537 kV cm −1 , which indicates that it is appropriate for energy storage capabilities. Moreover, the surface of the prepared nanocomposite film is electrically conducting and shows an electrical conductivity of ≈3.30 × 10 −3 S cm −1 at 2 wt% loading of Fe-RGO.

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Research paper thumbnail of An Approach to Design Highly Durable Piezoelectric Nanogenerator Based on Self-Poled PVDF/AlO-rGO Flexible Nanocomposite with High Power Density and Energy Conversion Efficiency

Advanced Energy Materials, 2016

Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power densi... more Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power density, and high energy conversion efficiency is of great concern. Here a flexible, sensitive, cost effective hybrid piezoelectric nanogenerator (HPNG) developed by integrating flexible steel woven fabric electrodes into poly(vinylidene fluoride) (PVDF)/aluminum oxides decorated reduced graphene oxide (AlO-rGO) nanocomposite film is reported where AlO-rGO acts as nucleating agent for electroactive β-phase formation. The HPNG exhibits reliable energy harvesting performance with high output, fast charging capability, and high durability compared with previously reported PVDF based PNGs. This HPNG is capable for harvesting energy from a variety and easy accessible biomechanical and mechanical energy sources such as, body movements (e.g., hand folding, jogging, heel pressing, and foot striking, etc.) and machine vibration. The HPNG exhibits high output power density and energy conversion efficiency, facilitating direct light on different color of several commercial light-emitting diodes instantly and powers up many portable electronic devices like wrist watch, calculator, speaker, and mobile liquid crystal display (LCD) screen through capacitor charging. More importantly, HPNG retains its performance after long compression cycles (≈158 400), demonstrating great promise as a piezoelectric energy harvester toward practical applications in harvesting biomechanical and mechanical energy for self-powered systems.

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Research paper thumbnail of A Mesoporous High-Performance Supercapacitor Electrode Based on Polypyrrole Wrapped Iron Oxide Decorated Nanostructured Cobalt Vanadium Oxide Hydrate with Enhanced Electrochemical Capacitance

Industrial & Engineering Chemistry Research

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Research paper thumbnail of Polyaniline/α-Ni(OH)2/iron oxide-doped reduced graphene oxide-based hybrid electrode material

Journal of Applied Electrochemistry

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Research paper thumbnail of Fast Charging Self-Powered Wearable and Flexible Asymmetric Supercapacitor Power Cell with Fish Swim Bladder as an Efficient Natural Bio-Piezoelectric Separator

Nano Energy

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Research paper thumbnail of Salt leached viable porous Fe 3 O 4 decorated polyaniline – SWCNH/PVDF composite spectacles as an admirable electromagnetic shielding efficiency in extended Ku-band region

Composites Part B: Engineering

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Research paper thumbnail of An Approach to Fabricate PDMS Encapsulated All-Solid-State Advanced Asymmetric Supercapacitor Device with Vertically Aligned Hierarchical ZnFeCo Ternary Oxide Nanowire and Nitrogen Doped Graphene Nanosheet for High Power Device Applications

ACS Applied Materials & Interfaces, 2017

We highlight the design and fabrication of a polydimethylsiloxane (PDMS) encapsulated advanced al... more We highlight the design and fabrication of a polydimethylsiloxane (PDMS) encapsulated advanced all-solid-state asymmetric supercapacitor (ASC) device consisting of hierarchical mesoporous zinc-iron-cobalt ternary oxide (ZICO) nanowire coated nickel (Ni) foam (ZICO@Ni foam) as a promising positive electrode and nitrogen doped graphene coated Ni foam (N-G@Ni foam) as negative electrode in the presence of PVA-KOH gel electrolyte. Owing to outstanding electrochemical behavior and ultrahigh specific capacitance of ZICO (≈ 2587.4 F/g at 1 A/g) and N-G (550 F/g at 1 A/g) along with their mutual synergistic outputs, the assembled all-solid-state ASC device exhibits an outstanding energy density of ≈40.5 Wh/kg accompanied by a remarkable long-term cycle stability with ≈95% specific capacitance retention even after 5000 charge-discharge cycles. The exclusive hierarchical ZICO nanowires were synthesized by a facile two-step process comprising of a hydrothermal protocol followed by an annealing treatment on a quartz substrate. While Zn(2+) gives the stability of the oxide system, Fe and Co ions provide better electronic conductivity and capacitive response under vigorous cyclic condition. The extraordinary performance of as-fabricated ASC device resembles its suitability for the construction of advanced energy storage devices in modern electronic industries.

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Research paper thumbnail of A Facile Approach to Develop Highly Stretchable PVC/ZnSnO3 Piezoelectric Nanogenerator with High Output Power Generation for Powering Portable Electronic Devices

Industrial & Engineering Chemistry Research, 2016

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Research paper thumbnail of Single wall carbon nanohorn (SWCNH)/graphene nanoplate/poly(methyl methacrylate) nanocomposites: A promising material for electromagnetic interference shielding applications

RSC Advances

Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) na... more Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared through addition of GNP/PMMA bead into the SWCNH dispersed PMMA matrix during its polymerization.

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Research paper thumbnail of High Energy Density Ternary Composite Electrode Material Based on Polyaniline (PANI), Molybdenum trioxide (MoO3) and Graphene Nanoplatelets (GNP) Prepared by Sono-Chemical Method and Their Synergistic Contributions in Superior Supercapacitive Performance

Electrochimica Acta

ABSTRACT

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Research paper thumbnail of Single wall carbon nanohorn (SWCNH)/graphene nanoplate/poly(methyl methacrylate) nanocomposites: a promising material for electromagnetic interference shielding applications

RSC Adv., 2015

Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) na... more Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared through addition of GNP/PMMA bead into the SWCNH dispersed PMMA matrix during its polymerization.

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Research paper thumbnail of High Energy Density Ternary Composite Electrode Material Based on Polyaniline (PANI), Molybdenum trioxide (MoO3) and Graphene Nanoplatelets (GNP) Prepared by Sono-Chemical Method and Their Synergistic Contributions in Superior Supercapacitive Performance

Electrochimica Acta, 2015

ABSTRACT

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Research paper thumbnail of Carbon nanohorn-graphene nanoplate hybrid: An excellent electrode material for supercapacitor application

Journal of Applied Polymer Science, 2015

ABSTRACT This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate ... more ABSTRACT This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate (GNP) hybrid (CNGN). The well-CNH-decorated GNP-plate electrode materials show high capacitance value (≈677 F/g) and can be extensively used in new generation for energy storage. In the hybrid (CNGN), two nanofillers jointly affect the capacitance behavior and increase the capacitance value of the CNGN hybrid. Homogeneous coating of CNH over the GNP plate plays an effective role to enhance the capacitance behavior of the composite. Field emission scanning electron microscopy and high-resolution transmission electron microscopy analysis of the composite confirmed the CNH coating on the GNP plate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42118.

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Research paper thumbnail of Polymer Based Piezoelectric Nanogenerators Design for Science

Design for Science, 2016

Recently, polymer based piezoelectric nanogenerators (PNGs) devices have attracted great attentio... more Recently, polymer based piezoelectric nanogenerators (PNGs) devices have attracted great attention for harvesting mechanical energy under different small mechanical and biomechanical actions with variable amplitude and frequency available in our living environment and lots of efforts have been devoted toward realization of highly sensitive and flexible sensors. Although these devices show excellent energy harvesting performance but their low mechanical robustness limits their use in various fields of applications. In our study, we have developed a facile method that involves solution casting process and judicious control in compression molding to design and fabricate a flexible hybrid piezoelectric nanogenerator (HPNG) consisting of PVDF and AlO-rGO by integrating flexible conducting steel woven fabric electrodes. Here, we have utilized the mechanical stiffness of the steel woven fabric to make the composite nanogenerator robust as well as to serve as a charge collector. The novel PVDF/AlO-rGO pressure sensor based on flexible steel fabric shows an unprecedented shifting of open circuit output voltage to a high value of ≈ 36 V and short circuit current of ≈ 0.8 μA, corresponds to a high power density of ≈ 27.97 μW/cm3 under repeating human finger imparting condition. Also, the HPNG is exceedingly efficient to charge the capacitor in a very short time span (» 6.1 V in 96.6 sec), and exhibits high energy conversion efficiency up to » 12.47 %. Benefitting from the excellent sensing as well as output performance properties, the HPNG shows an outstanding durability of »158400 cycles and ≈1600 cycles in a cyclic compression test under sewing machine vibration and human motion conditions, respectively. This high output performance and energy conversion efficiency of HPNG enable to lit up different color of several commercial light-emitting diodes (LEDs) instantly and power up many portable electronic devices like wrist watch, calculator, speaker and, mobile LCD screen through capacitor charging. Such high performance durable HPNG flexible pressure sensor the promising candidate for various small pressure applications such as bending, twisting, foot striking, folding at elbow, sewing machine vibration, heel pressing, and jogging/walking. The developed woven fabric integrated flexible HPNG is highly desirable for large-scale application of portable and flexible electronics devices, and may open up a new platform for energy harvesting material that can covert low-frequency mechanical energy from human activity into electricity.

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Research paper thumbnail of Bio-waste onion skin as an innovative nature-driven piezoelectric material with high energy conversion efficiency

Nano Energy, 2017

Development of non-toxic, ultra-sensitive, and flexible bio-inspired piezoelectric nanogenerator ... more Development of non-toxic, ultra-sensitive, and flexible bio-inspired piezoelectric nanogenerator has become a great challenge for next generation biomedical applications. High performance organic/inorganic materials based piezoelectric nanogenerators suffer from several unavoidable problems such as complex synthesis and high toxicity. Biodegradable and biocompatible piezoelectric material is utmost needed in in-vivo condition to harvest energy for biomedical applications. Here, we report a novel bio-piezoelectric nanogenerator (BPNG) using naturally abundant self-aligned cellulose fibrous untreated onion skin (OS) as efficient piezoelectric material having piezoelectric strength of ∼ 2.8 pC/N. The fabricated OSBPNG generated output voltage, current, instantaneous power density and high piezoelectric energy conversion efficiency of ≈ 18 V, ≈ 166 nA, ≈ 1.7 μW/cm 2 , and ≈ 61.7%, respectively, and turn on 30 green LEDs by a single device under repeated com-pressive stress of ≈ 34 kPa and ≈ 3.0 Hz frequency. In addition, maximum output voltage (≈ 106 V) was achieved when 6 units are connected in series, which instantaneously turns on 73 combined LEDs (30 green, 25 blue, and 18 red). OSBPNG is highly effective during throat movement such as coughing, drinking and swallowing. Furthermore, because it works at very low pressure originating from heart pulse or beat, it could be used in pacemakers and health care units. Finally, OSBPNG successfully differentiates speech signals, indicating its potential for speech recognition.

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Research paper thumbnail of Effect of g-PVDF on enhanced thermal conductivity and dielectric property of Fe-rGO incorporated PVDF based flexible nanocomposite film for efficient thermal management and energy storage applications

RSC Advances, 2016

Here, we investigate the effect of thermal conductivity of g-crystallites of PVDF in Fe-rGO/PVDF ... more Here, we investigate the effect of thermal conductivity of g-crystallites of PVDF in Fe-rGO/PVDF nanocomposite, which are of potential use as actuators and temperature sensors for thermal management applications. The formation of g-crystallites help to increase the thermal conductivity of the nanocomposite up to 0.89 W mK À1 at low level of filler loading (3 wt%) and we showed that the thermal conductivity depends on the amount of crystalline polar g-phase in addition to filler concentration. Although thermal conductivity depends on the crystallinity of the nanocomposite, here enhancement of thermal conductivity is not related only to crystallinity, as the crystallinity is decreased compared to neat PVDF. However the thermal conductivity increases because of the generation of a higher number of g-crystallites of small size. Furthermore, the nanocomposite at low filler loading also shows high dielectric constant with low dielectric loss of the order of z57 and z0.13, respectively, at 1 kHz. Moreover, the energy storage property and its dependence on g-crystallite size reveals that the material can also exhibit superior released energy density (1.45 J cm À3) as compared to pure PVDF.

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Research paper thumbnail of Self-powered flexible Fe-doped RGO/PVDF nanocomposite: an excellent material for a piezoelectric energy harvester

Nanoscale, 2015

In this work, we report the superior piezoelectric energy harvester ability of a non-electrically... more In this work, we report the superior piezoelectric energy harvester ability of a non-electrically poled Fe-doped reduced graphene oxide (Fe-RGO)/poly(vinylidene fluoride) (PVDF) nanocomposite film prepared through a simple solution casting technique that favors the nucleation and stabilization of ≈99% relative proportion of polar γ-phase. The piezoelectric energy harvester was made with non-electrically poled Fe-RGO/PVDF nanocomposite film that gives an open circuit output voltage and short circuit current up to 5.1 V and 0.254 μA by repetitive human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar γ-phase in the PVDF, due to the electrostatic interactions among the –CH 2 –/–CF 2 – dipoles of PVDF and the delocalized π-electrons and remaining oxygen functionalities of Fe-doped RGO via ion-dipole and/or hydrogen bonding interactions. Fourier transform infrared spectroscopy (FT-IR) confirmed the nucleation of the polar γ-phase of PVDF by electrostatic interactions and Raman spectroscopy also supported the molecular interactions between the dipoles of PVDF and the Fe-doped RGO nanosheets. In addition, the nanocomposite shows a higher electrical energy density of ≈0.84 J cm −3 at an electric field of 537 kV cm −1 , which indicates that it is appropriate for energy storage capabilities. Moreover, the surface of the prepared nanocomposite film is electrically conducting and shows an electrical conductivity of ≈3.30 × 10 −3 S cm −1 at 2 wt% loading of Fe-RGO.

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Research paper thumbnail of An Approach to Design Highly Durable Piezoelectric Nanogenerator Based on Self-Poled PVDF/AlO-rGO Flexible Nanocomposite with High Power Density and Energy Conversion Efficiency

Advanced Energy Materials, 2016

Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power densi... more Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power density, and high energy conversion efficiency is of great concern. Here a flexible, sensitive, cost effective hybrid piezoelectric nanogenerator (HPNG) developed by integrating flexible steel woven fabric electrodes into poly(vinylidene fluoride) (PVDF)/aluminum oxides decorated reduced graphene oxide (AlO-rGO) nanocomposite film is reported where AlO-rGO acts as nucleating agent for electroactive β-phase formation. The HPNG exhibits reliable energy harvesting performance with high output, fast charging capability, and high durability compared with previously reported PVDF based PNGs. This HPNG is capable for harvesting energy from a variety and easy accessible biomechanical and mechanical energy sources such as, body movements (e.g., hand folding, jogging, heel pressing, and foot striking, etc.) and machine vibration. The HPNG exhibits high output power density and energy conversion efficiency, facilitating direct light on different color of several commercial light-emitting diodes instantly and powers up many portable electronic devices like wrist watch, calculator, speaker, and mobile liquid crystal display (LCD) screen through capacitor charging. More importantly, HPNG retains its performance after long compression cycles (≈158 400), demonstrating great promise as a piezoelectric energy harvester toward practical applications in harvesting biomechanical and mechanical energy for self-powered systems.

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