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- 2018
- energy distribution
- graphene edge
- vacuum transistor
- Field emission
- Optoelectronic Information Science and Engineering
- Naval Research Laboratory
- KeyW Corporation
- Pohang University of Science and Technology (POSTECH)
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Surface Plasmon Resonance Based Highly Selective Fiber Optic Dopamine Sensor Fabricated Using Molecular Imprinted GNP/SnO <sub/>2</sub> Nanocomposite
摘要： Fabrication and characterization of a highly selective fiber optic surface plasmon resonance-based dopamine sensor using molecular imprinted graphene nanoplatelets/tin oxide (SnO2) nanocomposite have been reported. The synthesis of sensing layer has been carried out using a series of optimizations and morphological studies. The effectiveness of the sensing layer over other possible probe designs has been proved by performing control experiments for a dopamine concentration range covering the suggested level of dopamine for human being. The limit of detection (LOD) of the sensor evaluated is 0.031 μM, which is lower than the LOD values of various dopamine sensors fabricated using different methods. The specificity of the sensor for dopamine has been confirmed by performing experiments using various interferands while the stability and reusability of the sensor probe have been checked by performing experiments repeatedly for a long period of time. Apart from high sensitivity, low LOD, and fast response, the sensor can be used for remote sensing and online monitoring of dopamine.
关键词： surface plasmon resonance,SnO2 nanoparticles,optical fiber sensor,GNP/SnO2 nanocomposite,graphene,Dopamine,molecular imprinting
更新于2025-09-23 15:23:52
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Graphene foam field-effect transistor for ultra-sensitive label-free detection of ATP
摘要： As the major energy molecule of cells, adenosine triphosphate (ATP) regulates various biological processes and has been found to be closely related to many diseases. Therefore, ATP detection in trace amounts is very useful for understanding various biological processes, studying cellular events such as proliferation and apoptosis, and estimating contaminated degree of food and medical instrument. To date, the trace sensing ATP at picomolar level in biological systems is still a major challenge. Because of unique electrical and structural properties, graphene has attracted much attention in biosensing applications. Here, a sensitive and selective graphene foam field-effect transistor (GF-FET) biosensor for ATP detection is demonstrated. The lowest detection limit of the biosensors for analyzing ATP is down to 0.5 pM, which is one or several orders lower than the reported results. Moreover, the GF-FET biosensor show a good linear current response to ATP concentrations in a broad range from 0.5 pM to 50 μM. The GF-FET sensor surface can be regenerated for many times and used for up to weeks without significant loss of functionality. Based on this sensing platform, label-free measurements of ATP concentrations in human serum as well as in cell lysate are demonstrated. The work may provide a novel platform to study ATP release and energy-regulated biological processes, suggesting a promising future for biosensing applications.
关键词： FET,ATP,Graphene foams
更新于2025-09-23 15:23:52
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Reduction and compensation of humidity measurement errors at cold temperatures using dual QCM humidity sensors based on graphene oxides
摘要： One of the difficulties in measurements of relative humidity in a variety of environments is temperature-dependence especially at cold temperatures. Here, we report on the reduction and the compensation of temperature effects on humidity measurements using dual humidity sensors based on quartz crystal microbalance (QCM). Graphene oxide film is coated on quartz crystals as a humidity sensing layer for the detection of water sorption by the change of resonance frequency. Relative humidity in a test chamber, where dual QCM humidity sensors are located, is precisely controlled using a humidity generator at the temperature range from 20 °C to ?60 °C. It is found that single QCM humidity sensors measure humidity significantly higher than reference relative humidity by the generator as temperature is lowered due to the temperature-dependent resonance of quartz crystals. In an attempt to cancel out the temperature-dependent oscillation of QCM sensors, the ratio of resonance frequencies of dual QCM humidity sensors is used. Consequently, temperature-dependent errors in humidity measurement at low temperatures are evidently reduced. For the compensation of the remaining errors in the humidity measurement by dual QCM humidity sensors, a single formula is empirically obtained. After the compensation of low temperature effects, the dual QCM humidity sensors provide the measurement capability in terms of residual errors less than 1.1%rh throughout temperatures from 20 °C to ?60 °C. This study provides a useful insight to extend the applicability of QCM-based humidity sensors to environments with cold temperatures.
关键词： Compensation,Graphene oxide,Cold temperature,Quartz crystal microbalance,Humidity measurement,Humidity sensor
更新于2025-09-23 15:23:52
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The influences of temperature, humidity, and O2 on electrical properties of graphene FETs
摘要： The influences of temperature, humidity, and O2 to the gas sensing characteristics of graphene field effect transistors (FETs) have been studied as these environmental factors are often encountered in practical gas sensing applications. Both empirical results and theoretical analyses are characterized for heated graphene FET gas sensors from room temperature to 100°C under a wide range of applied gate voltages. It is found that at a constant applied gate voltage of -20 V with respect to the gate voltage at the neutrality point, the sensitivity of the device to humidity decreases; while the sensitivity to O2 decreases first, and increases afterwards as the operation temperature increases. These phenomena are explained by using the physisorption and chemisorption models between gases and the graphene surface. Furthermore, devices operate in the hole regime (the majority carrier is hole in the prototype devices) result in lower sensitivity to humidity and O2 as compared to those results of gas sensors operating in the electron regime due to the p-type doping effects of moisture and O2. As such, this work provides good foundations for graphene-based FET gas sensors in practical application environments under the influences of ambient air, temperature, and humidity.
关键词： ambient air,gas sensor,temperature,Graphene field effect transistor,humidity,oxygen
更新于2025-09-23 15:23:52
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Multifunctional ZnO/polyurethane-based solid-solid phase change materials with graphene aerogel
摘要： In this work, multifunctional polyurethane-based phase change materials with zinc oxide (ZnO) and graphene aerogel (GA) were prepared through facile impregnation. ZnO and GA improved the latent heat of the system from 86.8 J/g to 108.1 J/g for the heterogeneous nucleation and chemical mitigations. Furthermore, the photo-/electro-thermal energy conversion efficiency of the system with ZnO and GA is 80.1%, 84.4%, respectively, for the efficient light absorption of ZnO and GA as well as the electrical conductivity of GA. The as-prepared materials with high latent heat, excellent form-stability, remarkable thermal stability as well as reliability, efficient light-/electro-thermal energy conversion, have great prospects for applying in energy harvesting, conversion and storage devices like solar heater, smart textile and greenhouse.
关键词： Graphene aerogel,Light-thermal conversion,Electro-thermal conversion,Zinc oxide
更新于2025-09-23 15:23:52
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Influence of compression strains on photon absorption of silicene and germanene
摘要： In this paper, optical properties of silicene and germanene under compressive homogeneous strain are investigated within the density function theory. Results show that the optical-field response are strongly depend on the amount of applied strain. As the strain increases, the amount of optical absorption increases. In fact, by applying the compressive strain in the silicene and germanene, the band gap at the Dirac points decreases where ultimately reaches zero. Depending on the amount of strain, absorption peak shows red and blue shifts by increasing the strain. This can be realized by considering the change of the band gap energy and transition rates by the strain. In both of these graphene-like structures, the light absorption along zigzag direction is greater than that of the armchair direction.
关键词： Graphene-like structures,Compressive strain,Density functional theory,Optical properties
更新于2025-09-23 15:23:52
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Growth of vanadium dioxide nanostructures on graphene nanosheets
摘要： The metal oxide/graphene hybrid nanomaterials have been known as promising functional materials for advanced applications such as high capacitive electrode material of secondary batteries, and high sensitive material of high performance gas sensors. Here, morphology controlled vanadium dioxide (VO2) nanostructures were grown on Si wafer and exfoliated graphene by the vapor transport method using a horizontal furnace system. One-dimensional VO2 nanowires were grown on SiO2(300 nm)/Si substrate under 0.4 kPa condition. On the other hand, thick polycrystalline of VO2 platelets were grown on exfoliated graphene nanosheets under 0.4 kPa condition. In addition, polycrystalline VO2 platelets were only grown on exfoliated graphene nanosheets under 101 kPa (atmospheric pressure) condition. The growth of polycrystalline VO2 platelets on graphene nanosheets in atmospheric pressure condition is attributed to preferential growth on functional group of graphene surface such as carbonyl. The functional group is served as nucleation site of VO2 nanostructures.
关键词： Nanostructures,Hybrid Nanomaterials,Vapor Transport Method,Graphene,Vanadium Dioxide
更新于2025-09-23 15:23:52
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A Green and Facile Synthesis for rGO/Ag Nanocomposites Using One-step Chemical Co-reduction Route at Ambient Temperature and Combined First Principles Theoretical Analyze
摘要： Recently, graphene decorated with various inorganic nanoparticles, such as Pt, Au, Ag, TiO2 and Fe3O4, among which Ag nanocomposites are good candidates for electronics, optics, electrochemistry and catalysis. However, preparation techniques for Ag nanoparticles/carbon matrix hybrids require tedious multi-step processes often involving toxic reducing agents / high temperatures which is not viable for scalable production. Here, a facile, one step and eco-friendly chemical co-reduction route was utilized to synthesis of a new nanocomposites by Ag nanoparticle anchored on reduced graphene oxide (rGO) at ambient temperature and combined first principles theoretical analyze their interfacial adsorption behavior, is reported. In this way, graphene oxide (GO) and Ag+ simultaneously reduced by thiourea dioxide (TD) without using any additional reduced reactants. Results indicated that GO was successfully reduced to rGO and well-dispersed Ag nanoparticles with sizes of 6~7 nm, anchored on the surface of rGO sheets. Reduction mechanism was attributed to the synergistic effect of its hydrolysis products in aqueous media. The experiment and theoretical calculation results obtained demonstrate this method to be applicable to the synthesis of other metals on rGO sheets in order to improve wettability and interfacial bonding between rGO and metal and may possibly find various forthcoming medicinal, industrial and technological applications.
关键词： In-stiu co-reduction,Green reduce graphene/Ag nanocomposites,Interfacial behavior,First principles,Thiourea dioxide
更新于2025-09-23 15:23:52
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Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistors with Graphene
摘要： A thermal analysis of AlGaN/GaN high electron mobility transistors (HEMTs) with Graphene is investigated using Silvaco and Finite Element Method. Two thermal management solutions are adopted; first of all, graphene is used as dissipation material between SiC substrate and GaN buffer layer to reduce thermal boundary resistance of the device. At the same time, graphene is also used as a thermal spread material on the top of the source contacts to reduce thermal resistance of the device. The thermal analysis results show that the temperature rise of device adopting graphene decreases by 46.5% in transistors operating at 13.86 W/mm. Meanwhile, the thermal resistance of GaN HEMTs with graphene is 6.8 K/W, which is much lower than the device without graphene, which is 18.5 K/W. The thermal management solutions are useful for integration of large-scale graphene into practical devices for effective heat spreading in AlGaN/GaN HEMT.
关键词： AlGaN/GaN,Thermal Management,High-Electron-Mobility Transistors (HEMTs),Graphene
更新于2025-09-23 15:23:52
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Unconventional charge and spin-dependent transport properties of a graphene nanoribbon with line-disorder
摘要： Electronic transport with a line (or a few lines) of Anderson-type disorder in a zigzag graphene nanoribbon is investigated in the presence of Rashba spin-orbit interaction. Such line-disorders give rise to a peculiar behavior in both charge as well as spin-polarized transmission in the following sense. In the weak-disorder regime, the charge transport data show Anderson localization up to a certain disorder strength, beyond which the extended states emerge and start dominating over the localized states. These results are the hallmark signature of a selectively disordered (as opposed to bulk disorder) graphene nanoribbon. However, the spin-polarized transport shows a completely contradicting behavior. Further, the structural symmetries are shown to have an important role in the spintronic properties of the nanoribbons. Moreover, the edge-disorder scenario (disorder selectively placed at the edges) seems to hold promise for the spin-filter and switching device applications.
关键词： Anderson localization,spin transport,graphene nanoribbon,line-disorder,Rashba spin-orbit interaction
更新于2025-09-23 15:23:52