PhD Student at École de technologie supérieure studying Carbon Nanotube MEMS.
If you've ever drawn with a pencil, you've probably made graphene!
Accidental discovery Graphene was discovered in by Andre Geim and Kostya Novoselov in 2004. The discovery can almost be termed accidental but with years of prior studies and research. Graphene was first formed by removing flakes from a lump of graphite using sticky tape. This method is now famously called the "sticky tape method". Six years after their groundbreaking isolation of graphene, Andre and Kostya were awarded the 2010 Nobel Prize in physics for this work. What can Graphene do?? Graphene is considered as the world's first two dimensional material which basically means it is a crystalline material with a single atomic layer. This remarkable material is 200 times stronger than steel. It is also the thinnest material known-one million times thinner than the human hair. It is also the world's most conductive material as a result of its electronic structure. This could open new doors in electrical and electronics research. It's high strength means that it can be used as a composite in many areas. Graphene can also be used to improve the lifespan of the traditional lithium ion battery. Imagine going from 0 to 100% charge on your phone in under 2 minutes! Imagine a smartphone that you can wear on your wrists or a tablet that can be rolled up like a newspaper. Companies like Samsung, Apple and LG are currently investigating these technologies made possible by graphene. Graphene can also be used to further miniaturize transistors. Smaller transistors mean better performance and power consumption Seems too good to be true? Graphene is one material that promises a lot and it has received considerable attention from researchers all over the world due to its excellent properties. There is almost a rat race now to come up with the first commercial graphene product. There are also efforts to currently 3D print graphene which is a very interesting take on its production.The first commercial graphene product isn't far away! There SHOULD be some disadvantages for sure Yes there are as with any material. Graphene is a "Zero Band Gap" material - simply put, it is a material that cannot be turned off when it starts to conduct electricity. The costs associated with producing graphene commercially is still too high for commercialization. The toxicity of graphene is also quite high. Lastly, graphene is also susceptibe to an oxidative atmosphere. The pros outweigh the cons considerably, so it has all the ingredients to change our lives!
Abstract: We explore the feasibility of growing a continuous layer of graphene in prepatterned substrates, like an engineered silicon wafer, and we apply this as a mold for the fabrication of AFM probes. This fabrication method proves the fabrication of SU-8 devices coated with graphene in a full-wafer parallel technology and with high yield. It also demonstrates that graphene coating enhances the functionality of SU-8 probes, turning them conductive and more resistant to wear. Furthermore, it opens new experimental possibilities such as studying graphene-graphene interaction at the nanoscale with the precision of an AFM or the exploration of properties in nonplanar graphene layers.
Pub.: 09 Apr '13, Pinned: 20 Apr '17
Abstract: We present a microelectromechanical system (MEMS) graphene-based pressure sensor realized by transferring a large area, few-layered graphene on a suspended silicon nitride thin membrane perforated by a periodic array of micro-through-holes. Each through-hole is covered by a circular drum-like graphene layer, namely a graphene “microdrum”. The uniqueness of the sensor design is the fact that introducing the through-hole arrays into the supporting nitride membrane allows generating an increased strain in the graphene membrane over the through-hole array by local deformations of the holes under an applied differential pressure. Further reasons contributing to the increased strain in the devised sensitive membrane include larger deflection of the membrane than that of its imperforated counterpart membrane, and direct bulging of the graphene microdrum under an applied pressure. Electromechanical measurements show a gauge factor of 4.4 for the graphene membrane and a sensitivity of 2.8 × 10−5 mbar−1 for the pressure sensor with a good linearity over a wide pressure range. The present sensor outperforms most existing MEMS-based small footprint pressure sensors using graphene, silicon, and carbon nanotubes as sensitive materials, due to the high sensitivity.
Pub.: 11 Mar '16, Pinned: 20 Apr '17
Abstract: It remains a formidable challenge to develop supercapacitors having both high stretchability and electrochemical performance. A ternary polymer composite was herein developed by engineering graphene platelets (GnPs), poly (3,4-ethylenedioxythiophene) (PEDOT) and manganese dioxide (MnO2) into a kitchen sponge. Cost-effective GnPs having an electrical conductivity of 1460 S cm− 1 were deposited onto the sponge pore surface by a simple dipping and drying process, followed by in situ polymerization of 3,4-ethylenedioxythiophene. MnO2 was then deposited onto the GnPs and PEDOT layers through soaking the GnP/PEDOT sponge into KMnO4 solution. When the composite was used as the electrodes for a flexible, stretchable supercapacitor, we obtained not only high specific capacitance but a high stretchability up to 400%. The supercapacitor demonstrated a specific capacitance of 802.99 F g− 1 and an energy density of 55.76 Wh kg− 1, with 99% capacitance retention over 1000 stretching cycles; these are attributed to the synergy between the composite components as well as the wavy device structure. The mass and thickness of the MnO2 layer was found to increase with the soak, leading to the enhancement of electrochemical performance of GnP/PEDOT/MnO2 sponge electrodes, i.e. 368.96 F g− 1 for 5 min and 740.25 F g− 1 for 10 min.
Pub.: 27 Mar '17, Pinned: 20 Apr '17
Abstract: Benefit from exceptional electrical transport properties, graphene receives worldwide attentions, especially in the domain of high frequency electronics. Due to absence of effective bandgap causing off-state the device, graphene material is extraordinarily suitable for analog circuits rather than digital applications. With this unique ambipolar behavior, graphene can be exploited and utilized to achieve high performance for frequency multipliers. Here, dual-gated graphene field-effect transistors have been firstly used to achieve frequency quadrupling. Two Dirac points in the transfer curves of the designed GFETs can be observed by tuning top-gate voltages, which is essential to generate the fourth harmonic. By applying 200 kHz sinusoid input, arround 50% of the output signal radio frequency power is concentrated at the desired frequency of 800 kHz. Additionally, in suitable operation areas, our devices can work as high performance frequency doublers and frequency triplers. Considered both simple device structure and potential superhigh carrier mobility of graphene material, graphene-based frequency quadruplers may have lots of superiorities in regards to ultrahigh frequency electronic applications in near future. Moreover, versatility of carbon material system is far-reaching for realization of complementary metal-oxide-semiconductor compatible electrically active devices.
Pub.: 19 Apr '17, Pinned: 20 Apr '17
Abstract: The interaction between GO and DNA is very sensitive to the environment. For example, under the acidic condition, the affinity from GO to DNA will be enhanced, weakening the capability of GO on distinguishing DNAs with different confor-mations. Such effect impedes the development of sensitive pH biosensors based on GO-DNA nano-systems. In this work, we systematically studied the affinity between GO and i-motif forming oligonucleotides (IFOs) under different pH values and developed a herring sperm DNA (HSD) treatment method. By this method, the surface of GO is occupied by HSD so as to compromise the attractive force of GO which has been excessively enhanced at the acidic condition. As a result, the ability of GO in distinguishing between "open" and "closed" IFOs is successfully generalized to a wider pH range. Finally a pH-sensitive GO-IFO nano-system was fabricated, which showed excellent sensing ability not only in vitro but also in intracellular pH detection. As the appropriate interaction between GO and DNA is the basis for constructing GO-DNA biosensors, the strategy developed in this work shows great potentials to be applied to a variety of other GO-DNA sensing systems.
Pub.: 19 Apr '17, Pinned: 20 Apr '17
Abstract: The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer-scale electronic devices. Presently, long-lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate-voltage pulses, have been employed to achieve bandwidths suitable for applications such as video-frame-rate imaging. Here, atomically thin graphene-WS2 heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10(6) . Highly mobile ions and the nanometer-scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS2 . Responsivity R = 10(6) A W(-1) and detectivity D* = 3.8 × 10(11) Jones are observed, approaching that of single-photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video-frame-rate imaging applications.
Pub.: 19 Apr '17, Pinned: 20 Apr '17
Abstract: By a simple one-step reduction self-assembly process, a three-dimensional composite material graphene/polypyrrole aerogel (GPA) has been fabricated. The polypyrrole nanorods (PNRs) not only act as a spacer to avoid the graphene sheets aggregation and enhance mechanical strength but also effectively adjust the permittivity of GPAs to gain expected microwave absorption (MA) performance. Compared with pure graphene aerogel (GA), these aerogels with the ultralow density of around 0.020 g/cm3 show improved MA performance that the maximum reflection loss (RL) can reach −51.12 dB at the frequency of 6.4 GHz, and the effective absorption bandwidth (RL < −10 dB) was 5.88 GHz (10.48–16.36 GHz) corresponding to an absorber thickness of 3.0 mm. Such outstanding MA performances are attributed to the polarization and relaxation process that is correlated with the transformed microstructure of GPAs.
Pub.: 06 Mar '17, Pinned: 20 Apr '17
Abstract: Efficient utilization of solar energy for clean water is an attractive, renewable and environment-friendly way to solve the long-standing water crisis. For this task, we prepared the long-range vertically aligned graphene sheets membrane (VA-GSM) as the highly efficient solar thermal converter for generation of clean water. The VA-GSM was prepared by the antifreeze-assisted freezing technique we developed, which possessed the run-through channels facilitating the water transport, high light absorption capacity for excellent photothermal transduction, and the extraordinary stability in rigorous conditions. As a result, VA-GSM has achieved the average water evaporation rates are 1.62 and 6.25 kg m-2 h-1 under one and four sun illumination with the superb solar thermal conversion efficiency of up to 86.5% and 94.2% respectively, better than that of most carbon materials reported previously, which can efficiently produce the clean water from seawater, common wastewater and even concentrated acid and/or alkali solutions.
Pub.: 20 Apr '17, Pinned: 20 Apr '17
Abstract: The rapid growth of flexible and stretchable electronics paves the way toward compact and wearable power source devices. A shape-adaptive and stretchable energy harvester is particularly attractive due to its mobility, sustainability, and availability. In this work, a crumpled-graphene-based stretchable triboelectric nanogenerator (TENG) to harvest mechanical energy under various deformations is reported. Due to the unique stretchability of crumpled graphene structures, the crumpled-graphene-based TENGs could operate under compressive mode, stretching mode, and, more uniquely, their hybridized mode. Importantly, by shrinking a given planar graphene layer into a smaller region, a more crumpled TENG device delivered a higher output voltage, revealing the superior potential to develop smaller and better performance power generators for emerging wearable electronics. Its application as the energy harvester and motion sensor was demonstrated using finger and wrist motions.
Pub.: 18 Apr '17, Pinned: 20 Apr '17
Abstract: Herein, a novel ZnMoO4/reduced graphene oxide (rGO) hybrid was synthesized via a one-pot hydrothermal method followed by a thermal annealing process for the first time. The plate-like ZnMoO4 with diameter of 50–200 nm were uniformly distributed on the basal plane of two-dimensional rGO. As a novel anode material, ZnMoO4/rGO hybrid exhibited high reversible capacity (maximum capacity of 923.4 mAh g−1 at 0.1 A g−1), good rate capability (354.1 mAh g−1 at 2 A g−1), and excellent cycling stability over 500 cycles (0.064% capacity loss per cycle) overwhelmingly superior to those of bare ZnMoO4-based anode. The enhanced electrochemical performance of ZnMoO4/rGO hybrid is due to the unique composite structure with improved electronic conductivity, shortened lithium ion transport pathways, decreased lithium ions diffusion resistance, and the synergistic effect between the crystalline ZnMoO4 and the conductive rGO matrix.
Pub.: 08 Mar '17, Pinned: 20 Apr '17
Abstract: Recent attention has been focused on the synthesis and application of flexible lithium-ion battery electrodes for the development of high-performance and durable electronic devices. Herein, we synthesize a novel composites with carbonized cotton covered by graphene/SnO2 (CGN/SnO2), in which SnO2 nano-particles grow in-situ on the cotton fibers covered with graphene oxide (CGO) under the following thermal annealing process. The conductivity of the composites and the sizes of the SnO2 particles in the composites could be expediently adjusted by changing the thermal annealing temperatures. The as-prepared flexible CGN/SnO2 composites can be directly used as an anode for lithium-ion batteries without the addition of conductive additive, binder and current collector. The CGN/SnO2 composites prepared at 500 °C have exhibited a good reversible specific capacity (calculated by the weight of whole electrode) of 406 mAh·g− 1 (1.70 mAh·cm− 2) after 80 cycles. This work provides an effective way for the metal oxide composed with flexible carbon framework, promising to develop a new portable electrochemical energy-storage electrode.
Pub.: 14 Mar '17, Pinned: 20 Apr '17
Abstract: Novel dense graphene foams were fabricated by directly growing graphene on nickel templates by chemical vapor deposition. The as-grown graphene foam showed a hierarchical structure consisting of graphene microspheres with nano pores as flower-like morphology. The high quality of the graphene foam was confirmed by Raman spectrum and conductivity measurement as high as 5100 S m−1. To test its potential application in lithium ion battery, the monolithic graphene foam hybridized with TiO2 nanoparticles as anode material was synthesized via atomic layer deposition. The electrode exhibited high specific capacity (204 mAh g−1, 91 mAh g−1) even at high current (20 C, 60 C, respectively, 1 C = 335 mA g−1) with good stability and reversibility. The outstanding electrical performance could be attributed to the flower-like dense porous nanostructure in the graphene foam, which would work not only as a highly conductive host matrix for ion and electron transportation, but also effectively buffer the volume expansion during the lithiation and delithiation process.
Pub.: 09 Apr '17, Pinned: 20 Apr '17
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