Graphene-based hybrids for chemiresistive gas sensors
Introduction
Gas sensors can detect combustible, explosive and toxic gases, and have been widely used in safety monitoring and process control in residential buildings, industries and mines. However, sensitivity and selectivity are still bottlenecks for current solid sensors of gases. Graphene has attracted much attention as a gas-sensing material since its discovery in 2004 [1] because of its unique characteristics, such as electrical and thermal conductivity, low electronic noise, large surface-area-to-volume ratio, high chemical stability and excellent adsorptivity. High carrier mobility and density, and low intrinsic noise promise a high signal-to-noise ratio in detection. Every atom of a graphene film is exposed to the environment, making the conductance of graphene highly sensitive to local electrical and chemical perturbations. These exceptional properties are particularly useful for the development of gas sensors.
The gas-sensing properties of graphene were first investigated by Novoselov et al. [1]. However, there was no systematic research report on the gas-sensing properties of graphene until three years later. In that report, graphene was shown to be capable of detecting individual gas molecules because of its low electronic noise [2]. However, it was difficult to reach that level in real detection conditions despite the unique characteristics of graphene [3], [4], [5].
Robinson et al. [6] subsequently fabricated a gas sensor by using reduced graphene oxide (RGO) as the sensing material, in which the exfoliated graphene oxide (GO) platelets were deposited to form an ultrathin continuous network and were then tunably reduced by hydrazine hydrate vapor. Most graphene-based gas sensors use RGO because:
- •
its abundant defects and chemical groups facilitate gas adsorption;
- •
the chemical and electrical properties of RGO are highly tunable; and,
- •
compared to non-conductive GO, RGO can efficiently transport charges.
These RGO sensors could detect chemical-warfare agents and explosives at parts-per-billion (ppb) levels, and can be seen as the precursor of RGO gas sensors. To further improve the gas-sensing performance of GO or RGO sensors, the layer-by-layer (LbL) method was used to assemble small GOs on a large scale on a thin film, which exhibited high sensitivity and selectivity in detecting NO2 and volatile organic compounds (VOCs) [7], [8].
However, pristine graphene sensors suffer from some disadvantages because there are few dangling bonds on their surface, which limit the chemisorption of target molecules on the graphene surface. Physical or chemical modification of graphene has therefore been investigated. Electron-beam irradiation [9], hydrogen plasma [10] and chemical-reduction reagents [11] have been employed to modify the surface of graphene while, at the same time, reducing GO. Additionally, a facile, low-cost, and efficient method has been reported by Cui et al. [12] to tune the structure and the properties of RGO by applying a transient voltage across the RGO. Compared with the unmodified RGO, the voltage-activated RGO showed significantly enhanced sensing responses because the voltage-activation method might deeply remove extrinsic p-doping sources from air, increase oxygen functional groups (epoxide and ether groups), and create a large number of defects in RGO that lead to significant changes in the electrical properties of RGO, such as electrical conductivity and field-effect-transistor (FET) behavior.
Besides the surface modification by physical methods, chemical modification has commonly been used to enhance the sensing properties of graphene [13]. In particular, graphene-based hybrids consisting of graphene and traditional gas-sensing materials (e.g., noble metals, metal oxides or conducting polymers) display not only the individual properties of the traditional gas-sensing materials and graphene, but also additional novel properties due to the synergistic effect between them. The outstanding gas-sensing properties of graphene greatly depend on the number of layers and its dispersion. Due to van der Waals and π-π stacking interactions among individual graphene sheets, they have a tendency to aggregate when graphene-dispersion solutions are dried. Incorporation of nanostructures of traditional gas-sensing materials into graphene sheets prevents graphene from becoming agglomerated and also helps to achieve a good distribution of nanostructures. Thus, the effective surface area available for the gas interaction increases by several times. These nanostructure-graphene hybrids are prepared by an in-situ method, where nanostructures are prepared in the presence of graphene solution, or by directly mixing two previously prepared solutions.
Although some reviews about graphene-based gas sensors were published recently [14], [15], [16], [17], little attention was given to hybridized graphene gas sensors. However, increasing effort has been devoted to development of the hybridized graphene gas sensors. A systematic review is therefore timely and necessary to evaluate the success and to identify the challenges for graphene hybrids in gas detection. Here, we review the sensing mechanism and unique performance of the graphene-based hybrids as gas sensors. This review will help researchers understand the evolution and the challenges of graphene-based hybrids, and also further stimulate interest in the development of gas-sensing techniques.
We introduce hybridized graphene gas sensors by dividing them into four types according to their sensing principles, i.e., the hybrids of graphene with noble metals, metal oxides and conducting polymers, respectively, and their ternary hybrids.
Section snippets
Hybrids of graphene with noble metals
Noble metals have been employed to fabricate catalytic combustion sensors because of their high catalytic activity to flammable gases [18], so some researchers have attached noble-metal nanostructures onto graphene to form hybrids for flammable-gas detection. Table 1 shows the comparison of gas-sensing performance of noble-metal/graphene hybrids, from which it can be seen that most of the sensors operated at room temperature. However, most noble-metal-based sensors operate at high temperature
Hybrids of graphene with metal oxides
Metal oxides (e.g., SnO2, ZnO, In2O3 and Co3O4) have been widely used as gas sensors because of their advantages of low cost, easy production, compact size and simple measuring electronics [31], [32], [33]. However, the morphology and the structure of the sensing materials significantly influence their sensing performance, so various nanostructured metal oxides have been prepared to improve gas-sensing properties [34], [35], [36], [37].
As a recent research interest, the hybrids of graphene with
Hybrids of graphene with conducting polymers
In the past few decades, conducting conjugated polymers, such as polythiophene (PTh), polyaniline (PANI), and polypyrrole (PPy), which have π-conjugated carbon chains, have been investigated intensely, especially for their gas-sensing properties. They have exhibited many excellent properties, such as electrochemical reversibility, environmental stability, high conductivity, good mechanical performance and ease of preparation through chemical and electrochemical methods. Moreover, they possess
Ternary graphene-based hybrids
To improve the sensing performance of graphene-based binary hybrids further, ternary or quaternary graphene hybrids have been developed in which noble-metal-metal oxide, noble-metal-conducting polymer or metal-oxide-conducting polymer was hybridized with graphene to combine their advantages. To combine the advantages of noble metal and metal oxide, Pd-WO3 nanostructures were incorporated on RGO sheets using a controlled hydrothermal process to fabricate effective hydrogen-gas sensors; they
Conclusions and perspectives
Graphene-based hybrids have been widely investigated for use as chemiresistive gas sensors with high sensitivity and selectivity, so they have much potential to be widely used (e.g., public safety and pollution monitoring). We reviewed the sensing principles and synthesis processes of the graphene-based hybrids with noble metals, metal oxides and conducting polymers in order to understand and to design novel gas sensors better. We hoped to increase interest among those concerned with further
Acknowledgments
We appreciate the financial support of the National Basic Research Program of China (2013CB934300) and the National Natural Science Foundation of China (61374017, 61106012 and 21475133). Xing-Jiu Huang also thanks the One Hundred Person Project of the Chinese Academy of Sciences and the CAS Institute of Physical Science, University of Science and Technology of China (2012FXCX008) for financial support.
References (110)
- et al.
Flexible NO2 sensors fabricated by layer-by-layer covalent anchoring and in situ reduction of graphene oxide
Sensor. Actuat. B-Chem
(2014) - et al.
Improvement of gas sensing behavior in reduced graphene oxides by electron-beam irradiation
Sensor. Actuat. B-Chem
(2014) - et al.
Gas sensor based on p-phenylenediamine reduced graphene oxide
Sensor. Actuat. B-Chem
(2012) - et al.
Preparation, characterization and NH3-sensing properties of reduced graphene oxide/copper phthalocyanine hybrid material
Sensor. Actuat. B-Chem
(2014) - et al.
Recent developments on graphene and graphene oxide based solid state gas sensors
Sensor. Actuat. B-Chem
(2012) - et al.
Synthesis of Pd or Pt/titanate nanotube and its application to catalytic type hydrogen gas sensor
Sensor. Actuat. B-Chem
(2007) - et al.
Selectivity towards H2 gas by flame-made Pt-loaded WO3 sensing films
Sensor. Actuat. B-Chem
(2011) - et al.
Hydrogen sensing of the mixed-potential-type MnWO4/YSZ/Pt sensor
Sensor. Actuat. B-Chem
(2015) - et al.
Pd-doped reduced graphene oxide sensing films for H2 detection
Sensor. Actuat. B-Chem
(2013) - et al.
A novel Pd nanocube-graphene hybrid for hydrogen detection
Sensor. Actuat. B-Chem
(2014)
Reduced graphene oxide as an over-coating layer on silver nanostructures for detecting NH3 gas at room temperature
Sensor. Actuat. B-Chem
Flexible hydrogen sensors using graphene with palladium nanoparticle decoration
Sensor. Actuat. B-Chem
Metal oxide nano-crystals for gas sensing
Anal. Chim. Acta
Gas sensors using hierarchical and hollow oxide nanostructures: overview
Sensor. Actuat. B-Chem
Enhancing NO2 gas sensing performances at room temperature based on reduced graphene oxide-ZnO nanoparticles hybrids
Sensor. Actuat. B-Chem
Enhanced room temperature sensing of Co3O4-intercalated reduced graphene oxide based gas sensors
Sensor. Actuat. B-Chem
Fabrication of alpha-Fe2O3@graphene nanostructures for enhanced gas-sensing property to ethanol
Appl. Surf. Sci
LPG sensing application of graphene/Bi2O3 quantum dots composites
Solid State Sci
In situ synthesis of graphene/SnO2 quantum dots composites for chemiresistive gas sensing
Mat. Sci. Semicon. Proc
Metal oxide-based gas sensor research: how to?
Sensor. Actuat. B-Chem
Grain-size effects on gas sensitivity of porous SnO2-based elements
Sensor. Actuat. B-Chem
Development of microstructure In/Pd-doped SnO2 sensor for low-level CO detection
Sensor. Actuat. B-Chem
Chemical control synthesis of nanocrystalline SnO2 by hydrothermal reaction
Mater. Lett
Reduced graphene oxide mediated SnO2 nanocrystals for enhanced gas-sensing properties
J. Mater. Sci. Technol
SnO2 nanoparticles-reduced graphene oxide nanocomposites for NO2 sensing at low operating temperature
Sensor. Actuat. B-Chem
Parts per billion-level detection of benzene using SnO2/graphene nanocomposite composed of sub-6 nm SnO2 nanoparticles
Anal. Chim. Acta
Synthesis of single-crystalline potassium-doped tungsten oxide nanosheets as high-sensitive gas sensors
J. Alloy. Compd
Fabrication of a novel 2D-graphene/2D-NiO nanosheet-based hybrid nanostructure and its use in highly sensitive NO2 sensors
Sensor. Actuat. B-Chem
Preparation and gas sensing properties of hierarchical flower-like In2O3 microspheres
Sensor. Actuat. B-Chem
Preparation of porous flower-like CuO/ZnO nanostructures and analysis of their gas-sensing property
J. Alloy. Compd
Hydrogen sensor based on graphene/ZnO nanocomposite
Sensor. Actuat. B-Chem
One-pot reflux method synthesis of cobalt hydroxide nanoflake-reduced graphene oxide hybrid and their NOx gas sensors at room temperature
J. Alloy. Compd
Tin oxide/graphene composite fabricated via a hydrothermal method for gas sensors working at room temperature
Sensor. Actuat. B-Chem
A novel ammonia sensor based on high density, small diameter polypyrrole nanowire arrays
Sensor. Actuat. B-Chem
Hybridized conducting polymer chemiresistive nano-sensors
Nano Today
Applied novel sensing material graphene/polypyrrole for humidity sensor
Sensor. Actuat. B-Chem
Hybrid film of chemically modified graphene and vapor-phase-polymerized PEDOT for electronic nose applications
Org. Electron
Electric field effect in atomically thin carbon films
Science
Detection of individual gas molecules adsorbed on graphene
Nat. Mater
Intrinsic response of graphene vapor sensors
Nano Lett
Practical chemical sensors from chemically derived graphene
ACS Nano
Graphene films and ribbons for sensing of O2, and 100 ppm of CO and NO2 in practical conditions
J. Phys. Chem. C
Reduced graphene oxide molecular sensors
Nano Lett
Layer-by-layer films of graphene and ionic liquids for highly selective gas sensing
Angew. Chem. Int. Edit
A practical carbon dioxide gas sensor using room-temperature hydrogen plasma reduced graphene oxide
Sensor. Actuat. B-Chem
Ultrasensitive chemical sensing through facile tuning defects and functional groups in reduced graphene oxide
Anal. Chem
Fabrication, optimization, and use of graphene field effect sensors
Anal. Chem
Graphene-based chemical sensors
J. Phys. Chem. Lett
Biological and chemical sensors based on graphene materials
Chem. Soc. Rev
Nanostructured Pt decorated graphene and multi walled carbon nanotube based room temperature hydrogen gas sensor
Nanoscale
Cited by (282)
Highly responsive hydrogen sensor based on Pd nanoparticle-decorated transfer-free 3D graphene
2024, Sensors and Actuators B: ChemicalElectrochemical impedance spectroscopic investigation on detection of H<inf>2</inf>S gas using 2D TiO<inf>2</inf>/rGO nano-composites
2023, Applied Surface Science AdvancesThe effects of gas exposure on the graphene/AlGaN/GaN heterostructure under UV irradiation
2023, Sensors and Actuators B: ChemicalRecent advances in MoS<inf>2</inf>-based nanomaterial sensors for room-temperature gas detection: A review
2023, Sensors and Diagnostics