A Comprehensive Study on the Spectroscopic Characterization and Molecular Dynamics Simulation of Pristine and Functionalized Graphene Nanoplatelets for Gas Sensing Applications (original) (raw)
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Recent advances in graphene based gas sensors
Graphene, a single, one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice and thetwo-dimensional building block for carbon materials, has attracted great interest for a wide range ofapplications. Due to its superior properties such as thermo-electric conduction, surface area and mechan-ical strength, graphene materials have inspired huge interest in sensing of various chemical species. Inthis timely review, we discuss the recent advancement in the field of graphene based gas sensors withemphasis on the use of modified graphene materials. Further, insights of theoretical and experimentalaspects associated with such systems are also discussed with significance on the sensitivity and selectivityof graphene towards various gas molecules. The first section introduces graphene, its synthesis methodsand its physico-chemical properties. The second part focuses on the theoretical approaches that discussthe structural improvisations of graphene for its effective use as gas sensing materials. The third sectiondiscusses the applications of pristine and modified graphene materials in gas sensing applications. Vari-ous graphene modification methods are discussed including using dopants and defects, decoration withmetal/metal oxide nanoparticles, and functionalization with polymers. Finally, a discussion on the futurechallenges and perspectives of this enticing field of graphene sensors for gas detection is provided.
Recent Advances on Graphene-Based Gas Sensors
Russian Journal of Physical Chemistry A, 2020
Owing to its unprecedented structural, electronic and mechanical properties, graphene, a singleatomic sheet of carbon atoms, is effectively used to detect chemical species. In this work, adsorption of gaseous molecules, mainly toxic (NO 2 , NO, NH 3 , CO, CO 2 , HF, H 2 S, etc.) and volatile organic compounds (VOCs), on graphene and modified graphene (GO, rGO) has been reviewed. The gas sensing ability of graphene is enhanced by doping with heteroatoms, and functionalizing it with many groups, such as hydroxyl, epoxy, etc. Recent advances in detection of gaseous molecules by graphene and modified graphene, coupled with metal and metal oxide nanoparticles, which have high response and better sensitivity than metal and metal oxide NPs because of high surface area and increased electronic charge transfer, have also been reported.
2013
Graphene has attracted intense scientific interest due to its exceptional electrical, mechanical and chemical properties over the last couple of years. This strictly twodimensional (2D) material has potential applications in advanced electronic devices and composite materials. The challenge is to produce large area defect-free graphene necessary for electronic applications while bulk-production at gram scale of graphene with defects enabling anchoring sites for nanoparticles is required for applications like catalysis. Herein, we report the Ni-catalyzed ambient pressure chemical vapor deposition of (APCVD) synthesis of few-layer graphene, the spatial characterization of the fewlayered transparent graphene by micro Raman spectroscopy, its electrical characterization showing p-semiconductor behavior, as well as studies on the gas-sensing properties towards low concentrations of CO and H 2. Moreover, APCVD and low pressure CVD (LPCVD) growth of graphene have been carried on Cu-catalyst surfaces. Effect of metal catalyst thickness and CVD growth parameters (concentrations of the gases, growth time, cooling effect etc.) were studied in detail to optimize the quality of graphene with respect to the number of layers and defects. Chemical synthesis of graphene was established by oxidation of graphite to graphite oxide (GO) and followed by reduction process. Different methods (Staudenmaier's, Hummers', Modified Hummers' and Tour's Methods) to synthesize GO were studied comparatively to have highly oxidized GO. Various reduction techniques were studied to improve the quality of chemically derived graphene (CDG). Metal nanoparticles (NPs of Au, Ni and Pd) were successfully supported on CDG and employment of Pd/CDG as catalysts in the dehydrogenation and hydrolysis of ammonia borane (AB). Moreover, metal oxide NPs of titanium dioxide (by UV-assisted method and hydrothermal method), tungsten oxide (by sonochemical method) and zinc oxide (via thermal decomposition method), were successfully deposited on CDG. Composites of CDG with TiO 2 and WO 3 were applied successfully in photodegradation reactions of methylene blue (MB) under UV-light. Sensing measurements of ZnO/CDG hybrid materials were conducted towards hydrogen gas at room temperature and elevated temperatures (200 o C and 300 o C). VI Zusammenfassung: Graphen steht seit mehreren Jahren im Mittelpunkt des wissenschaftlichen Interesses, dies aufgrund seiner außergewöhnlichen elektrischen, mechanischen und chemischen Eigenschaften. Dieses zwei-dimensionale (2D) Material besitzt potenzielle Anwendungsmöglichkeiten in einer Vielzahl von elektronischen Bauteilen sowie als Kompositmaterial. Die besondere Herausforderung besteht darin große Stücke von defektfreiem Graphen herzustellen, welche für den Einsatz in der Elektronik benötigt werden. Ein weiterer Anwendungsaspekt liegt in der in der Herstellung von nicht defektfreiem Graphen im Grammmaßstab, wobei diese Defektstellen als Verankerungsstellen für Nanopartikel dienen können und so für den Einsatz als Komposit beispielsweise in der Katalyse geeignet sind. In der vorliegenden Arbeit wird zunächst auf die Synthese von Graphen mit einer geringen Zahl an Lagen mittels Nickel katalysierter Gasphasendeposition unter Raumdruck (APCVD) eingegangen, danach auf die Charakterisierung des erzeugten Graphens, mittels Micro-Ramanspektroskopie sowie weiterhin auf die elektrischen p-leitenden Eigenschaften dieses Materials eingegangen. Zusätzlich wurde das gassensorische Verhalten bezüglich geringer Konzentrationen von CO und H 2 untersucht sowie das Wachstum von Graphen mittels Gasphasenabscheidung (APCVD und LPCVD) auf Kupferkatalysatoroberflächen untersucht. Der Einfluss der Katalysatorabscheidung und der CVD Wachstumsparameter, wie z.B. Gaskonzentration, Wachstumszeit und Abkühlungzeit wurden intensiv studiert um die Qualität des erzeugten Graphens in Hinblick auf die Zahl der Graphenlagen und-defekte zu optimieren. Desweiteren wurde die nasschemische Synthese von Graphen durch Oxidation von Graphit zu Graphitoxid (GO) und anschließender Reduktion untersucht. Verschiedene Methoden (nach Staudenmaier, Hummers, modifizierte Hummers und Tour Methoden) wurden vergleichend untersucht. Ebenso wurden verschiedene Reduktionstechniken studiert, um die Qualität des chemisch erzeugten Graphens (CDG) zu steigern. Gold-, Nickel-und Palladium-Nanopartikel konnten erfolgreich auf die Oberfläche des CDG aufgebracht werden. Das so erhaltene Pd/CDV Komposit konnte als wirksamer Katalysator in der Dehydrierung und Hydrolyse von Amminboran getestet werden. Darüber hinaus wurden Nanopartikel aus Titandioxid mittels UV-Deposition und Hydrothermalmethode, Wolframoxid mittels Ultraschall und Zinkoxid mittels thermischer Zersetzung erzeugt. Die TiO 2 und WO 3 basierten CDG Materialien zeigten sich katalytisch aktiv für den Photoabbau von Methylenblau (MB) unter UV-Bedingungen. Gassensorische Messungen an den ZnO/CDG Hybridmaterialien zeigten eine Sensoraktivität gegenüber Wasserstoff bei Raumtemperatur sowie erhöhten Temperaturen (200°C und 300°C).
Graphene and g-C3N4-Based Gas Sensors
Journal of Nanotechnology, 2022
The efficient monitoring of the environment is currently gaining a continuous growing interest in view of finding solutions for the global pollution issues and their associated climate change. In this sense, two-dimensional (2D) materials appear as one of highly attractive routes for the development of efficient sensing devices due, in particular, to the interesting blend of their superlative properties. For instance, graphene (Gr) and graphitic carbon nitride g-C3N4 (g-CN) have specifically attracted great attention in several domains of sensing applications owing to their excellent electronic and physical-chemical properties. Despite the high potential they offer in the development and fabrication of high-performance gas-sensing devices, an exhaustive comparison between Gr and g-CN is not well established yet regarding their electronic properties and their sensing performances such as sensitivity and selectivity. Hence, this work aims at providing a state-of-the-art overview of th...
Simulation of Graphene Nanoplatelets for NO$_{2}$ and CO Gas Sensing at Room Temperature
2022
This work reports the modeling and simulation of gas sensors made from pristine graphene nanoplatelets (P-GnPs) using COMSOL Multiphysics software. The mass balance equation was solved while including contributions of electromigration flux. An example GnP-based gas sensor was simulated to undergo exposure to NO2 and CO gases at different concentrations to understand the effects of adsorption. Various electrical properties and the overall sensor responses were also studied as a function of gas concentration in order to determine how viable such sensors could be for target gases. The results herein show that the resistance of the P-GnP-based gas sensor decreases when exposed to NO2 gas whereas an opposite trend is seen when CO gas is used for exposures, ultimately suggesting that the P-GnPs exhibit p-type behavior. Sensitivities of 23 % and 60 % were achieved when the P-GnP-based gas sensor was exposed to 10 mol/m3 concentration of NO2 and CO at room temperature, respectively. The dat...
Raman Spectroscopy of Graphene, Graphite and Graphene Nanoplatelets
2D Materials, 2019
The theoretical simplicity of sp 2 carbons, owing to their having a single atomic type per unit cell, makes these materials excellent candidates in quantum chemical descriptions of vibrational and electronic energy levels. Theoretical discoveries, associated with sp 2 carbons, such as the Kohn anomaly, electron-phonon interactions, and other exciton-related effects, may be transferred to other potential 2D materials. The information derived from the unique Raman bands from a single layer of carbon atoms also helps in understanding the new physics associated with this material, as well as other two-dimensional materials. The following chapter describes our studies of the G, D, and G′ bands of graphene and graphite, and the characteristic information provided by each material. The G-band peak located at ~1586 cm −1 , common to all sp 2 carbons, has been used extensively by us in the estimation of thermal conductivity and thermal expansion characteristics of the sp 2 nanocarbon associated with single walled carbon nanotubes (SWCNT). Scanning electron microscope (SEM) images of functionalized graphene nanoplatelet aggregates doped with argon (A), carboxyl (B), oxygen (C), ammonia (D), fluorocarbon (E), and nitrogen (F), have also been recorded and analyzed using the Gwyddion software.
The Synergistic Properties and Gas Sensing Performance of Functionalized Graphene-Based Sensors
Materials, 2022
The detection of toxic gases has long been a priority in industrial manufacturing, environmental monitoring, medical diagnosis, and national defense. The importance of gas sensing is not only of high benefit to such industries but also to the daily lives of people. Graphene-based gas sensors have elicited a lot of interest recently, due to the excellent physical properties of graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO). Graphene oxide and rGO have been shown to offer large surface areas that extend their active sites for adsorbing gas molecules, thereby improving the sensitivity of the sensor. There are several literature reports on the promising functionalization of GO and rGO surfaces with metal oxide, for enhanced performance with regard to selectivity and sensitivity in gas sensing. These synthetic and functionalization methods provide the ideal combination/s required for enhanced gas sensors. In this review, the functionalization o...
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2019)
The paper reviews the state of the art of graphene employed as an active layer in chemiresistive gas sensors. Graphene properties such as high specific surface area, low noise, planar structure, flexibility, etc., are commonly highlighted as strengths in the sensors technology. However, the listed virtues are mostly related to the pristine graphene or even graphene monolayers, while majority of devices use chemically synthesized graphene derivatives. These vague statements may be induced by the high level of graphene hype and racing for the research grants. Moreover, graphene has no dangling bonds functioning as prime reaction agents. This led us to propose more adequate view onto a capacity of graphene in the area of gas sensors. In this study, we focused onto three aspects: (i) the substantiation of the low noise for sensing devices, (ii) the assumed versus actual surface area of the real graphene layers, and (iii) an integration of graphene sensors into silicon circuits.
Analytical Approach to Study Sensing Properties of Graphene Based Gas Sensor
Sensors, 2020
Over the past years, carbon-based materials and especially graphene, have always been known as one of the most famous and popular materials for sensing applications. Graphene poses outstanding electrical and physical properties that make it favorable to be used as a transducer in the gas sensors structure. Graphene experiences remarkable changes in its physical and electrical properties when exposed to various gas molecules. Therefore, in this study, a set of new analytical models are developed to investigate energy band structure, the density of states (DOS), the velocity of charged carriers and I-V characteristics of the graphene after molecular (CO, NO2, H2O) adsorption. The results show that gas adsorption modulates the energy band structure of the graphene that leads to the variation of the energy bandgap, thus the DOS changes. Consequently, graphene converts to semiconducting material, which affects the graphene conductivity and together with the DOS variation, modulate veloci...