100 research outputs found
Surface morphology engineering of metal oxide-transition metal dichalcogenide heterojunction
No full textA tremendous effort has been made to develop 2D materials-based FETs for electronic applications due to their atomically thin structures. Typically, the electrical performance of the device can vary with the surface roughness and thickness of the channel layer. Therefore, a two-step surface engineering process is demonstrated to tailor the surface roughness and thickness of MoSe2 multilayers involving exposure of O2 plasma followed by dipping in (NH4)2S(aq) solution. The O2 plasma treatment generated an amorphous MoOx layer to form a MoOx/MoSe2 heterojunction, and the (NH4)2S(aq) treatment tailored the surface roughness of the heterojunction. The ON/OFF current ratio of MoSe2 FET is about 1.1 × 105 and 5.7 × 104 for bare and chemically etched MoSe2, respectively. The surface roughness of the chemically treated MoSe2 is higher than that of the bare, 4.2 ± 0.5 nm against 3.6 ± 0.5 nm. Conversely, a 1-hour exposure of the multilayer MoOx/MoSe2 heterostructure with the (NH4)2S(aq) solution removed the amorphous oxide layer and scaled down the thickness of MoSe2 from ~92.2 nm to ~38.9 nm. The preliminary study shows that this simple two-step strategy can obtain a higher surface-area-to-volume ratio and thickness engineering with acceptable variation in electrical properties
Polarization-controlled amplified spontaneous emission in 2D semiconductors with birefringent microcavity
No full textWe report on the polarization-controlled amplification of excitonic emission in the monolayer WS2 coupled with ZnO microcavity. From polarization-resolved micro-photoluminescence spectroscopy and numerical modeling, we found that the polarization of WS2 excitonic emission can be tailored by the whispering gallery modes of the birefringent ZnO microcavity. Furthermore, the light input-light output curves exhibit the clear threshold kink and the superlinear increase in the output intensity for both the TM and TE polarization modes, indicating the polarization-dependent amplification of excitonic emission. Our results suggest an approach to realize the polarization-controlled photonic devices based on 2D materials. © 2021 Author(s).1
Selective removal of radioactive iodine from water using reusable Fe@Pt adsorbents
No full text© 2022 The Author(s)Environmental damage from serious nuclear accidents should be urgently restored, which needs the removal of radioactive species. Radioactive iodine isotopes are particularly problematic for human health because they are released in large amounts and retain radioactivity for a substantial time. Herein, we prepare platinum-coated iron nanoparticles (Fe@Pt) as a highly selective and reusable adsorbent for iodine species, i.e., iodide (I−), iodine (I2), and methyl iodide (CH3I). Fe@Pt selectively separates iodine species from seawater and groundwater with a removal efficiency ≥ 99.8%. The maximum adsorption capacity for the iodine atom of all three iodine species was determined to be 25 mg/g. The magnetic properties of Fe@Pt allow for the facile recovery and reuse of Fe@Pt, which remains stable with high efficiency (97.5%) over 100 uses without structural and functional degradation in liquid media. Practical application to the removal of radioactive 129I and feasibility for scale-up using a 20 L system demonstrate that Fe@Pt can function as a reusable adsorbent for the selective removal of iodine species. This systematic procedure is a standard protocol for designing highly active adsorbents for the clean separation and removal of various chemical species dissolved in wastewater.Y
Biomolecule based fiber supercapacitor for implantable device
No full textWith the growing demand for electronic medical devices for healthcare applications, we studied an implantable supercapacitor that can operate in an implantable electronic device. Here, we report a flexible implantable fiber supercapacitor for an in vivo energy storage device. The fiber supercapacitor has a high flexibility and a high potential to be applied in an implant device because the fiber can be implanted in the blood vessel and the wound can be stitched with the fiber-like suture. The fiber electrodes were fabricated in a biscrolling process that trapped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ferritin nanoclusters within multiwalled carbon nanotube (MWNT) sheets that provide mechanical strength and electrical conductivity. In addition, the supercapacitor is biocompatible because the MWNT sheets are coated with biocompatible materials such as PEDOT:PSS and ferritin. The areal capacitance of the PEDOT:PSS/ferritin/MWNT fiber supercapacitor was 32.9 mF/cm2 in a phosphate buffered saline solution, and the areal energy density was 0.82 μWh/cm2; these values are 52 times higher than that of the guest-free MWNT yarn. The supercapacitor operated well in a mouse and exhibited excellent biocompatibility; the capacitance was maintained above 90% in the mouse after eight days. © 2018 Elsevier Ltd1
Harvesting electrical energy from torsional thermal actuation driven by natural convection
No full textThe development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to-cold temperature difference of about 13 degrees C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.This work was supported by the Creative Research Initiative Center for Self-Powered Actuation of the National Research Foundation and the Ministry of Science, ICT & Future Planning (MSIP) in Korea. Support in Australia was from Centre of Excellence funding from the Australian Research Council. Support in the USA was from Air Force Grant AOARD-FA2386-13-4119, Air Force Office of Scientific Research grant FA9550-15-1-0089, and Robert A. Welch Foundation grant AT-0029
Elastomeric and Dynamic MnO2/CNT Core-Shell Structure Coiled Yarn Supercapacitor
No full textReversibly deformable and highly performing solid-state yarn supercapacitors are obtained using MnO2-deposited microcoiled yarn electrodes. The core(CNT)–shell(MnO2)-structured coiled electrodes achieve high stretchability (37.5%) without the help of elastomeric substrates, minimizing the size of the supercapacitors. Therefore, high specific capacitances of 34.6 F cm−3, 61.25 mF cm−2, and 2.72 mF cm−1 are achieved for coiled supercapacitors without impairing mechanical stretchability or electrochemical cyclability.This work was supported by the Creative Research Initiative Center for Self-powered Actuation and the Korea-US Air Force Cooperation Program Grant No. 2013K1A3A1A32035592 in Korea. Support at the University of Texas at Dallas was provided by Air Force Office of Scientific Research grants FA9550-15-1-0089, FA9550-14-1-0227, and FA2386-13-1-4119, NASA grants NNX14CS09P and NNX15CS05C, NSF grant CMMI 1120382, and the Robert A. Welch Foundation grant AT-0029. Additional support was from the Australian Research Council Discovery Grant DP110101073 and the Australian National Fabrication Facility
Microbuckled Mechano-electrochemical Harvesting Fiber for Self-Powered Organ Motion Sensors
No full textMechanical harvesters have attracted tremendous attention
as self-powered
strain sensors; previous harvesters required high stress to stretch
the fiber because of their high Young’s modulus and low elasticity.
We report on a mechano-electrochemical harvesting (MECH) fiber based
on the new buckle structure, which has a low Young’s modulus
(2 MPa) with high elasticity (up to 100%) in a similar physiological
fluid. MECH converts mechanical energy into electrical energy by changing
the capacitance due to changing the surface area caused by the microbuckle
on the surface. The damage to the cells can be minimized by their
softness; the fiber was stitched on the tissue of the pig stomach
while maintaining the performance like a suture fiber. Additionally,
the fiber successfully operated in an organ-similar system, which
is composed of the stomach or bladder of a pig. The fiber has a high
potential to be applied in wearable energy sources and self-powered
strain sensors
Biomolecule based fiber supercapacitor for implantable device
No full textWith the growing demand for electronic medical devices for healthcare applications, we studied an implantable supercapacitor that can operate in an implantable electronic device. Here, we report a flexible implantable fiber supercapacitor for an in vivo energy storage device. The fiber supercapacitor has a high flexibility and a high potential to be applied in an implant device because the fiber can be implanted in the blood vessel and the wound can be stitched with the fiber-like suture. The fiber electrodes were fabricated in a biscrolling process that trapped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ferritin nanoclusters within multiwalled carbon nanotube (MWNT) sheets that provide mechanical strength and electrical conductivity. In addition, the supercapacitor is biocompatible because the MWNT sheets are coated with biocompatible materials such as PEDOT: PSS and ferritin. The areal capacitance of the PEDOT:PSS/ferritin/MWNT fiber supercapacitor was 32.9 mF/cm(2) in a phosphate buffered saline solution, and the areal energy density was 0.82 mu Wh/cm(2); these values are 52 times higher than that of the guest-free MWNT yarn. The supercapacitor operated well in a mouse and exhibited excellent biocompatibility; the capacitance was maintained above 90% in the mouse after eight days.This work was supported by the Creative Research Initiative Center for Self-Powered Actuation and the DGIST R&D Program (18-NT-02) of the Ministry of Science, ICT and Future Planning in Korea. Support at the University of Texas at Dallas was provided by the Air Force Office of Scientific Research grants FA9550-15-1-0089 and FA2386-13-1-4119, NASA grant NNX15CSS05C, and Robert A. Welch Foundation grant AT-0029
Integrated Mechano-Electrochemical Harvesting Fiber and Thermally Responsive Artificial Muscle for Self-Powered Temperature–Strain Dual-Parameter Sensor
No full textSignificant progress in healthcare fields around the world has inspired us to develop a wearable strain–temperature sensor that can monitor biomedical signals in daily life. This novel self-powered temperature–strain dual-parameter sensor comprises a mechano-electrochemical harvester (MEH) and a thermally responsive artificial muscle (TAM). The MEHTAM system generates electricity from strain and thermal fluctuations. In addition, the sensor is comfortable to wear, owing to its stretchability (>100%), softness (<3 MPa), and one-dimensional fibers (diameter 230 μm). The MEH induces a change in the electrochemical capacitance, resulting in an electrical signal under applied strain (34 μA/m) and stress (20 μA/(m·MPa)). The TAM can be used as a mechanical temperature sensor, because the tensile stroke responds linearly to changes in temperature. As the harvester and artificial muscle are combined, the MEHTAM system generates electricity, owing to external and internal mechanical stimuli caused by muscle contractions as a response to temperature changes. The MEHTAM system that we have developed—a self-powered, strain–temperature dual-parameter sensor that is soft, stretchable, and fiber-shaped—is an interesting candidate for the production of comfortable, wearable, dual-parameter sensors
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