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PUBLICATIONS

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Patents

Journals

  • 34

    High-performance and robust triboelectric nanogenerators based on optimal microstructured poly(vinyl alcohol) and poly(vinylidene fluoride) polymers for self-powered electronic applications

      Abstract

      Triboelectric nanogenerators (TENGs) which are one of the notable renewable energy harvesting devices have been demonstrated for various types of energy harvesting, sensing, and self-powered electronic applications. However, enhancing the electrical output performance by optimizing the TENG parameters and reducing its processing cost is still major issues to be resolved for practical and industrial utilization. Herein, we demonstrated a cost-effective and high-performance TENG using polyvinylidene fluoride (PVDF) and microstructure aligned polyvinyl alcohol (MS@PVA) polymers as negatively and positively polarized triboelectric materials, respectively. The PVDF film developed by a facile and cost-effective ultra-sonication process and its high electroactive β-phase can be utilized to enhance the electric dipole-dipole interactions in the film, and also lead to an increase in its piezoelectric coefficient. Besides, the PVA film was produced by a simple solidification method and the microstructures on its surface are developed by merely corresponding inverse patterns on commercially available sandpaper. The resultant TENG with the PVDF and MS@PVA polymers exhibited maximum peak-to-peak open-circuit voltage, short-circuit current, and instantaneous output power density values of 230 V, 6 μA, and 3.1 W/m2, respectively. Ultimately, such a high electrical output generated by the TENG was employed to drive portable electronic devices such as displays and light-emitting diodes.

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    • 33

      Multicomponent architectured battery-type flexible yarns for high-performance wearable supercapatteries

      Abstract

      Rational design of light weight, flexible and wearable yarn-type electrodes with selectively designed battery-type materials has attracted a promising research interest for the development of high-performance miniatured energy storage devices. However, the relatively lower energy storage performance caused by poor mass loading of existing fiber/yarn-based devices limits their practical applicability in a wide range. Herein, an unique plaiting approach is demonstrated to design flexible and wearable yarn-type supercapatteries (YSCs) with high electrochemical performance. With ubiquitous polyester fabric fibers (PFs) in a plaiting form, PFs are converted into highly conductive plaited PFs via dual layered metallization with superior surface roughness. Upon deposition of carbon nanotubes and nickel cobalt double hydroxides on metallized PFs, an efficient battery-type electrode is designed, which exhibits a high specific capacity of 162.8 mAh g−1 with an excellent cycling stability of 93.3% in alkaline electrolyte. The two-electrode system-based solid-state YSCs are further assembled using multicomponent architectured battery-type and capacitive-type activated carbon electrodes, which enables a high potential of 1.55 V with superior energy and power densities (30.49 Wh kg−1 and 1137.26 W kg−1), respectively. By capitalizing high energy storage, the solar charging-based YSC is practically examined to be able to energize various wearable electronics.

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    • 32

      Rare-earth-free Sr2YSb1-xO6:xMn(4+): Synthesis, structure, luminescence behavior, thermal stability, and applications

        Abstract

        We report the rare-earth-free Sr2YSbO6 (SYS):Mn4+ phosphors with excellent photoluminescence performance for indoor illuminations. The phase structure, elemental composition, luminescence behavior, thermal stability, lifetime, color purity, and quantum yield (QY) were analyzed in detail. The resultant sample showed a broadband excitation wavelength in the range of 250–450 nm, and the optimal doping concentration was 0.5 mol%. Under the suitable excitation wavelength of 307 nm, the SYS:0.005Mn4+ phosphor emitted a deep-red emission with the Commission Internationale de I'Eclairage chromaticity coordinate of (0.708, 0.290) and a high color purity of 93.34%. The emission intensity was found to be about 59.45% at 423 K while the activation energy was 0.28 eV. Moreover, the lifetime and QY of the optimal sample were measured to be 641.58 µs and 38.37%, respectively. Eventually, the white lighting-emitting didoes (LEDs) exhibited a strong white light with good color-rendering index (CRI) and correlated color temperature (CCT) values. Besides that, the novel LED structure based on the SYS:0.005Mn4+-polydimethylsiloxane film could also emit a warm white region while the CRI and CCT values were measured to be about 81.39 and 3091 K.

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      • 31

        Air-gap embedded triboelectric nanogenerator via surface modification of non-contact layer using sandpapers

        Abstract

        With the increased number of small electronics and demand for their energy source, renewable energy sources have received much attention. Above all, a triboelectric nanogenerator (TENG) based on the combination of contact electrification and electrostatic induction has been researched as a method of converting mechanical energy into electricity. In order to increase the electrical output of TENGs with raising the surface charge density, a lot of researchers have focused on the fabrication methods to employ micro-/nano-structures onto a contact surface of the TENG, but have been facing several issues regarding the degradation of the output performance from the iterative operation process. Hence, it is highly required to introduce an approach to enhancing the performance of TENG, while minimally degrading the output power during the long-term operation. In this paper, an air-gap embedded TENG (AE-TENG), which contains a microstructure on the non-contact surface by means of a sandpaper, is proposed. These small air-gaps between the spin-coated polydimethylsiloxane and the non-contact surface can significantly boost the total surface charge density of the dielectric layer. Thus, the electrical output performance of the AE-TENG is enhanced without any surface engineering on the contact surface. Furthermore, the effect of the air-gap induced surface charges on the electric potential is systematically analyzed by not only experimentally electrical outputs, but theoretical and computational modeling based on the V–Q–x relationship and simulation software tool. This air-gap induced triboelectric effect opens a new perspective of the development of electrical outputs by providing a structural/theoretical understanding for TENGs.

        Graphical abstract: Air-gap embedded triboelectric nanogenerator via surface modification of non-contact layer using sandpapers
        Link
      • 30

        ZnO nanorods@conductive carbon black nanocomposite based flexible integrated system for energy conversion and storage through triboelectric nanogenerator and supercapacitor

        Abstract

        Owing to the tremendous increase in global environmental pollution and the scarcity of fossil fuel depletion, the scout for new, renewable, and green energy alternatives has been escalated. Specifically, flexible energy conversion and storage devices that act as power sources for wearable electronics are in demand. Herein, we propose an integrated energy conversion and storage system composed of flexible ZnO nanorods (NRs)@conductive carbon black (CB) nanocomposite (NC) based triboelectric nanogenerator (FZCT) and supercapacitor (FZCS). Firstly, ZnO NRs are prepared via a facile precipitation method and then the work function of the ZnO NRs is tuned with the addition of CB. The FZCT is fabricated using ZnO NRs@CB NCs coated nickel foam (NF) as a positive tribo-layer against counter tribo-layer (PTFE). FZCT with optimized content of CB (20 wt%) generated an open circuit voltage (VOC) of 28 V, a short circuit current (ISC) of 4.5 µA, and a power density of 80 µW/cm2. The VOC and the ISC values of the FZCT with optimized CB content are greater than that of pure ZnO NRs based FZCT. The FZCS is developed using the same ZnO NRs@CB/NF as a positive electrode and activated carbon coated NF (AC/NF) as a negative electrode in 1 M Na2SO4 electrolyte. The areal capacitance, maximum areal energy density, and power density of the FZCS are, 448 mF/cm2, 0.12 mW h/cm2, and 27.44 mW/cm2, respectively. Furthermore, an integrated energy conversion and storage system is successfully implemented by connecting the FZCT and FZCS through a bridge rectifier. The integrated device is able to convert and store the energy generated by FZCT very efficiently. The experiments reveal that the FZCT developed from this study can deliver the electrical output while it is attached even onto the human body. This study offers new opportunities in integrated energy conversion and storage devices with simple structured flexible materials.

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      • 29

        Hybrid tribo-thermoelectric generator for effectively harvesting thermal energy activated by the shape memory alloy

        Abstract

        Thermal energy is generated from all equipment during operation. Likewise, thermal energy exists everywhere and dissipates uselessly. It is necessary to transform thermal energy into renewable electrical energy by utilizing materials and devices exhibiting unique features of thermal properties. Shape memory alloys (SMAs) consisting of a compound of nickel (Ni) and titanium (Ti), operate based on unique thermomechanical properties, such as shape memory effect (SME) and superelastic effect (SE). Due to these two effects, SMAs are possible to be deformed and recovered by external heat. One-dimensional SMA wire (SW) can effectively harvest wasted thermal energy by the phase change in SMA from a wrinkled state to a straight state in order to generate continuously rotating energy with two sheaves. In this paper, we propose a thermally-driven SMA-wire based hybrid generator (SW-HG), including a disk-TENG and thermoelectric generator (TEG) which lead to generate a high voltage and large current, respectively. In addition, the operation principle of rotating by the deformation and the recovery of the SW at the phase-change temperature are systematically investigated as well as analyzed using two theoretical models. The unique thermomechanical behavior of the SW-HG is applied to commercial vehicles using output signals for the real-time temperature monitoring inside the engine room. Considering these unique features of SW, the SW-HG is expected to be dependable devices for IoT applications as well as can effectively convert surrounding wasted heat energy into reusable electrical energy in real life.

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      • 28

        Strong Green Emission of Erbium(III)-Activated La2MgTiO6 Phosphors for Solid-State Lighting and Optical Temperature Sensors

        Abstract

        In this work, novel green-emitting La2MgTiO6:Er3+ (LMTO:Er3+) phosphors were successfully synthesized. The phase structure, electronic structure, morphology, luminescence behaviors, and other optical characteristics were investigated in detail. Besides, the optical sensing properties of the thermal-coupled levels (2H11/2, 4S3/2) were investigated based on the fluorescence intensity ratio principle, and the maximum absolute and relative sensing sensitivities were found to be as high as 0.963% and 1.107% K–1, respectively. The packaged light-emitting diode (LED) emitted the near-white light with a color-rendering index of 77.12 and a proper correlated color temperature of 4989 K, respectively. Finally, the novel polydimethylsiloxane film-converted LED structure was fabricated. All the above results suggest that the novel LMTO:Er3+ phosphors are proposed for solid-state lighting and luminescent thermometers.

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      • 27

        Novel Conductive Ag-Decorated NiFe Mixed Metal Telluride Hierarchical Nanorods for High-Performance Hybrid Supercapacitors

        Abstract

        Mixed metal chalcogenide nanoarchitectures have been attracting enormous attention as battery-type electrodes for hybrid supercapacitors (HSCs) owing to their enhanced electrochemical (EC) performance. Despite having high electrical conductivity and good EC properties, tellurium has not been fully utilized in metal chalcogenide electrodes as much as sulfur and selenium. Herein, a facile strategy for the fabrication of nickel and iron (NiFe) mixed metal telluride hierarchical nanorods (MMT HNRs) on nickel foam (NF) is proposed. Furthermore, conductive silver (Ag) is decorated on MMT HNRs (AMMT HNRs) to improve the conducting channels, thereby EC performance. Benefitting from the combined advantages of electroactive NiFe mixed metal, conductive tellurium and Ag, and hierarchical nanorod-like nanomorphology, the AMMT HNR electrode has delivered high areal capacity (1.1 mAh cm–2). Finally, the AMMT based HSC with activated carbon coated NF (AC/NF) as a negative electrode exhibited the highest areal capacitance (1176.5 mF cm–2) with high areal energy density (0.669 mWh cm–2) and power density (64 mW cm–2). Moreover, the HSC device has maintained good cycling stability (86% capacity retention) even after 5000 cycles. New findings of this study definitely shed light on the development of telluride-based mixed metal chalcogenide supercapacitors.

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      • 26

        Preparation of NiO decorated CNT/ZnO core-shell hybrid nanocomposites with the aid of ultrasonication for enhancing the performance of hybrid supercapacitors

        Abstract

        Supercapacitor (SC) electrodes fabricated with the combination of carbon nanotubes (CNTs) and metal oxides are showing remarkable advancements in the electrochemical properties. Herein, NiO decorated CNT/ZnO core-shell hybrid nanocomposites (CNT/ZnO/NiO HNCs) are facilely synthesized by a two-step solution-based technique for the utilization in hybrid supercapacitors. Benefitting from the synergistic advantages of three materials, the CNT/ZnO/NiO HNCs based electrode has evinced superior areal capacity of ~67 µAh cm−2 at a current density of 3 mA cm−2 with an exceptional cycling stability of 112% even after 3000 cycles of continuous operation. Highly conductive CNTs and electrochemically active ZnO contribute to the performance enhancement. Moreover, the decoration of NiO on the surface of CNT/ZnO core-shell increases the electro active sites and stimulates the faster redox reactions which play a vital role in augmenting the electrochemical properties. Making the use of high areal capacity and ultra-long stability, a hybrid supercapacitor (HSC) was assembled with CNT/ZnO/NiO HNCs coated nickel foam (CNT/ZnO/NiO HNCs/NF) as positive electrode and CNTs coated NF as negative electrode. The fabricated HSC delivered an areal capacitance of 287 mF cm−2 with high areal energy density (67 µWh cm−2) and power density (16.25 mW cm−2). The combination of battery type CNT/ZnO/NiO HNCs/NF and EDLC type CNT/NF helped in holding the capacity for a long period of time. Thus, the systematic assembly of CNTs and ZnO along with the NiO decoration enlarges the application window with its high rate electrochemical properties.

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      • 25

        Facile synthesis of MnMoO4@MWCNT and their electrochemical performance in aqueous asymmetric supercapacitor

        Abstract

        The MnMoO4@multi-walled carbon nanotube (MWCNT) composite is prepared successfully by a hydrothermal method. The composite is subjected as an electrode material for supercapacitors, showing excellent electrochemical feature with a high specific capacitance of 1017 F g−1 at 1 A g−1. The electrochemical behavior of the composite is compared with the MnMoO4 electrode material. Owing to high performance of composite, asymmetric supercapacitor (ASC) composed of MnMoO4@MWCNT and activated carbon is fabricated with an aqueous electrolyte. The device delivers a high energy density of 18.1 W h kg−1 at the power density of 362.4 W kg−1. With good energy storage properties of electrode material, it could store sufficient charge to power the twelve red color light-emitting diodes. Furthermore, a motor fan is rotated by ASC device. A digital watch is also powered by ASCs. The obtained results suggest that the prepared MnMoO4@MWCNT composite material is promising for energy storage devices.

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