scholarly journals Graphene-Based Ammonia Sensors Functionalised with Sub-Monolayer V2O5: A Comparative Study of Chemical Vapour Deposited and Epitaxial Graphene †

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 951 ◽  
Author(s):  
Margus Kodu ◽  
Artjom Berholts ◽  
Tauno Kahro ◽  
Jens Eriksson ◽  
Rositsa Yakimova ◽  
...  
Keyword(s):  
Structural Damage ◽  
Free Charge Carrier ◽  
Chemical Vapour ◽  
Single Layer ◽  
Epitaxial Graphene ◽  
Ambient Atmosphere ◽  
Order Of Magnitude ◽  
Sensor Properties ◽  
Ammonia Sensors ◽  
Carrier Doping

Graphene in its pristine form has demonstrated a gas detection ability in an inert carrier gas. For practical use in ambient atmosphere, its sensor properties should be enhanced with functionalisation by defects and dopants, or by decoration with nanophases of metals or/and metal oxides. Excellent sensor behaviour was found for two types of single layer graphenes: grown by chemical vapour deposition (CVD) and transferred onto oxidized silicon (Si/SiO2/CVDG), and the epitaxial graphene grown on SiC (SiC/EG). Both graphene samples were functionalised using a pulsed laser deposited (PLD) thin V2O5 layer of average thickness ≈ 0.6 nm. According to the Raman spectra, the SiC/EG has a remarkable resistance against structural damage under the laser deposition conditions. By contrast, the PLD process readily induces defects in CVD graphene. Both sensors showed remarkable and selective sensing of NH3 gas in terms of response amplitude and speed, as well as recovery rate. SiC/EG showed a response that was an order of magnitude larger as compared to similarly functionalised CVDG sensor (295% vs. 31% for 100 ppm NH3). The adsorption site properties are assigned to deposited V2O5 nanophase, being similar for both sensors, rather than (defect) graphene itself. The substantially larger response of SiC/EG sensor is probably the result of the smaller initial free charge carrier doping in EG.

Electrolysis soy protein isolate-based oleogels prepared with an emulsion-templated approach

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Dianyu Yu ◽  
Yan Chen ◽  
Xing Chen ◽  
Yunyan Huang ◽  
Liqi Wang ◽  
...  
Keyword(s):  
Soy Protein ◽  
Xanthan Gum ◽  
Binding Capacity ◽  
Soy Protein Isolate ◽  
Single Layer ◽  
Protein Isolate ◽  
Regulatory Limits ◽  
Order Of Magnitude ◽  
The Stability ◽  
Oil Binding

Abstract This research focuses on the use of protein-polyphenol complex and protein-polyphenol: polysaccharide complexes to prepare oleogels through an emulsion-templated approach. Electrolysis soy protein isolate (ESPI) could be effectively adsorbed on the surface of a single-layer emulsion to increase the particle size. The order of the negative charges of the emulsion after adding polysaccharides was xanthan gum (XG)> pectin> carboxymethyl cellulose (CMC). Rheological behavior showed that the stability of the double-layer emulsions increased, and the viscoelasticity increased around one order of magnitude with the addition of polysaccharides. The oil binding capacity (OBC) of the oleogel prepared by adding polysaccharides increased to more than 97%. The peroxide value (PV) and anisidine value (AV) of XG oleogel were the minimum values in all samples. The AV and POV were within the regulatory limits of China after storage for 21 days. This provides a reference to design of ESPI-based oleogel for different applications.

scholarly journals Half integer quantum Hall effect in high mobility single layer epitaxial graphene

2009 ◽  
Vol 95 (22) ◽  
pp. 223108 ◽  
Author(s):  
Xiaosong Wu ◽  
Yike Hu ◽  
Ming Ruan ◽  
Nerasoa K Madiomanana ◽  
John Hankinson ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
High Mobility ◽  
Single Layer ◽  
Epitaxial Graphene ◽  
Half Integer ◽  
Integer Quantum Hall Effect ◽  
Integer Quantum

Gate-tunable ion–electron hybrid phototransistor based on a graphene/RbAg4I5 composite

2019 ◽  
Vol 7 (42) ◽  
pp. 13253-13260
Author(s):  
Pengfei Wang ◽  
Jun Yin ◽  
Qianqian Hu ◽  
Bocheng Lv ◽  
Jia-Lin Zhu ◽  
...  
Keyword(s):  
Binding Energy ◽  
Single Layer ◽  
Silver Ions ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Order Of Magnitude ◽  
Photo Response ◽  
Magnitude Increase ◽  
Linear Modulation

A phototransistor based on a composite of single-layer graphene and superconductor RbAg4I5 realizes linear modulation of the binding energy between electrons and silver ions, resulting in a two order of magnitude increase of photo-response.

scholarly journals Self-Assembled Vanadium Oxide Nanoflakes for p-Type Ammonia Sensors at Room Temperature

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 317 ◽  
Author(s):  
Haihong Yin ◽  
Changqing Song ◽  
Zhiliang Wang ◽  
Haibao Shao ◽  
Yi Li ◽  
...  
Keyword(s):  
Vanadium Oxide ◽  
Room Temperature ◽  
Gas Sensing ◽  
Electron Microscopies ◽  
Ammonia Sensing ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Self Assembled ◽  
Ammonia Sensors ◽  
P Type

VO2(B), VO2(M), and V2O5 are the most famous compounds in the vanadium oxide family. Here, their gas-sensing properties were investigated and compared. VO2(B) nanoflakes were first self-assembled via a hydrothermal method, and then VO2(M) and V2O5 nanoflakes were obtained after a heat-phase transformation in nitrogen and air, respectively. Their microstructures were evaluated using X-ray diffraction and scanning and transmission electron microscopies, respectively. Gas sensing measurements indicated that VO2(M) nanoflakes were gas-insensitive, while both VO2(B) and V2O5 nanoflakes were highly selective to ammonia at room temperature. As ammonia sensors, both VO2(B) and V2O5 nanoflakes showed abnormal p-type sensing characteristics, although vanadium oxides are generally considered as n-type semiconductors. Moreover, V2O5 nanoflakes exhibited superior ammonia sensing performance compared to VO2(B) nanoflakes, with one order of magnitude higher sensitivity, a shorter response time of 14–22 s, and a shorter recovery time of 14–20 s. These characteristics showed the excellent potential of V2O5 nanostructures as ammonia sensors.

Graphene as an anti-corrosion coating layer

2015 ◽  
Vol 180 ◽  
pp. 495-509 ◽  
Author(s):  
Line Kyhl ◽  
Sune Fuglsang Nielsen ◽  
Antonija Grubišić Čabo ◽  
Andrew Cassidy ◽  
Jill A. Miwa ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Graphene Layer ◽  
Room Temperature ◽  
Crystal Surface ◽  
Hexagonal Lattice ◽  
Chemical Vapour ◽  
Ambient Atmosphere ◽  
Free Standing ◽  
Corrosion Properties ◽  
Hot Surface

Graphene, a single layer of carbon atoms arranged in an aromatic hexagonal lattice, has recently drawn attention as a potential coating material due to its impermeability, thermodynamic stability, transparency and flexibility. Here, the effectiveness of a model system, a graphene covered Pt(100) surface, for studying the anti-corrosion properties of graphene, has been evaluated. Chemical vapour deposition techniques were used to cover the single crystal surface with a complete layer of high-quality graphene and the surface was characterised after exposure to corrosive environments with scanning tunnelling microscopy (STM) and Raman spectroscopy. Graphene covered Pt samples were exposed to: (i) ambient atmosphere for 6 months at room temperature and 60 °C for 75 min, (ii) Milli-Q water for 14 hours at room temperature and 60 °C for 75 min, and (iii) saltwater (0.513 M NaCl) for 75 min at room temperature and 60 °C. STM provides atomic resolution images, which show that the graphene layer and the underlying surface reconstruction on the Pt(100) surface remain intact over the majority of the surface under all conditions, except exposure to saltwater when the sample is kept at 60 °C. Raman spectroscopy shows a broadening of all graphene related peaks due to hybridisation between the surface Pt d-orbitals and the graphene π-bands. This hybridisation also survives exposure to all environments except saltwater on the hot surface, with the latter leading to peaks more representative of a quasi free-standing graphene layer. A mechanism explaining the corrosive effect of hot saltwater is suggested. Based on these experiments, graphene is proposed to offer protection against corrosion in all tested environments, except saltwater on a hot surface, and Raman spectroscopy is proposed as a useful method for indirectly assessing the chemical state of the Pt surface.

Epitaxial Single-Layer Graphene on the SiC Substrate

2012 ◽  
Vol 717-720 ◽  
pp. 645-648 ◽  
Author(s):  
Sergey Yu. Davydov ◽  
Alexander A. Lebedev
Keyword(s):  
Silicon Carbide ◽  
Density Of States ◽  
Anderson Model ◽  
Single Layer ◽  
Epitaxial Graphene ◽  
Single Layer Graphene ◽  
Electron Charge ◽  
Analytical Expression ◽  
Layer Graphene

The analytical expression for the density-of-states (DOS) of single-layer graphene interacting with the SiC surface (epitaxial graphene) is obtained. The silicon carbide DOS is described within the scope of the Haldane-Anderson model. It is shown that due to the interaction with the substrate the gap of about 0.01-0.06 eV arises in the epitaxial graphene DOS. The estimation indicates that the electron charge of about (−10-3) e/atom transfers from the substrate to graphene.

FAILURE MECHANISM OF SINGLE-LAYER CYLINDRICAL RETICULATED SHELLS UNDER EARTHQUAKE MOTION

2012 ◽  
Vol 12 (02) ◽  
pp. 233-249 ◽  
Author(s):  
XU-DONG ZHI ◽  
FENG FAN ◽  
SHI-ZHAO SHEN
Keyword(s):  
Failure Mechanism ◽  
Structural Damage ◽  
Failure Modes ◽  
Dynamic Instability ◽  
Single Layer ◽  
Dynamic Strength ◽  
Fuzzy Synthetic Evaluation ◽  
Strength Failure ◽  
Earthquake Motion ◽  
Structural Responses

In order to have a good understanding of the failure mechanism of single-layer cylindrical reticulated shells under earthquake motions, two failure modes, that is, dynamic instability and dynamic strength failure, are studied of single-layer cylindrical reticulated shells under earthquake motion. The accumulation of material damages that may accelerate failure of these shells under dynamic actions is considered. The relationships between the structural responses under the ultimate loads are investigated through a systematic simulation study that covers different parameters. A method is proposed for classification of failure modes of the shells, using the fuzzy synthetic evaluation theory and the structural responses of different sample studies. The effectiveness of the proposed method is proved through applications to some examples. Finally, a damage model is established for identification of different structural damage levels and for determination of the ultimate load for strength failure.

scholarly journals Effects of Sm2O3 and V2O5 Film Stacking on Switching Behaviors of Resistive Random Access Memories

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 318
Author(s):  
Lin ◽  
Wu ◽  
Chen
Keyword(s):  
Resistive Switching ◽  
Random Access ◽  
Single Layer ◽  
High Resistance State ◽  
Switching Behavior ◽  
Bipolar Resistive Switching ◽  
Compliance Behavior ◽  
Order Of Magnitude ◽  
Resistance State ◽  
Switching Characteristics

: In this work, the resistive switching characteristics of resistive random access memories (RRAMs) containing Sm2O3 and V2O5 films were investigated. All the RRAM structures made in this work showed stable resistive switching behavior. The High-Resistance State and Low-Resistance State of Resistive memory (RHRS/RLRS) ratio of the RRAM device containing a V2O5/Sm2O3 bilayer is one order of magnitude higher than that of the devices containing a single layer of V2O5 or Sm2O3. We also found that the stacking sequence of the Sm2O3 and V2O5 films in the bilayer structure can affect the switching features of the RRAM, causing them to exhibit both bipolar resistive switching (BRS) behavior and self-compliance behavior. The current conduction mechanisms of RRAM devices with different film structures were also discussed.

Comparative Investigation of the Graphene-on-Silicon Carbide and CVD Graphene as a Basis for Biosensor Application

2019 ◽  
Vol 799 ◽  
pp. 185-190 ◽  
Author(s):  
Natalja Sleptsuk ◽  
Alexander A. Lebedev ◽  
Ilya Eliseyev ◽  
Oleg Korolkov ◽  
Jana Toompuu ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Electrode Materials ◽  
Single Layer ◽  
Chemical Vapor ◽  
Comparative Investigation ◽  
Epitaxial Graphene ◽  
Single Layer Graphene ◽  
Electrochemical Biosensing ◽  
Graphene Films ◽  
Biosensor Application

Graphene has been employed as electrode materials in various electrochemical biosensors due to its excellent electrical, mechanical, thermal and optical properties. In the present study, Chemical Vapor Deposited (CVD) and epitaxial graphene on SiC were examined as material for electrochemical biosensing application. The surface of both types of graphene were characterized using Raman spectroscopy as well as with Scanning Electron Microscopy (SEM). As the key point for the comparison, the impedance spectroscopy measurements of different graphene films using deionized water and saline 0.9% NaCl solution were performed as well. The method of impedance measurements applied to graphene films expands the range of possibilities for using this material as sensitive biosensors. Based on the comparative tests results, it is possible to draw the first simple conclusions about the advantages of CVD or epitaxial graphene. Based on the results of impedance spectroscopy, it is possible to draw a simple conclusion – single layer graphene has the higher sensitivity.

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