Graphene-based gas sensor.
2017
Graphene, a honeycomb structure with single layer sp 2 hybridization carbon atom, has extraordinary mechanical and electrical
properties, exhibiting great potential in sensing area. The ultrahigh
electron mobility in room temperature as well as the ultrahigh specific
surface area, endows graphene a promising candidate for ultrasensitive
gas sensor. As a typical two dimensional material, every atom in graphene
can be regarded as surface atom. Therefore, every atom will be able
to interact with gas molecule, which provides an ultrahigh sensitivity
and the ultralow detection limit (as low as for single molecule detection).
The current researches for improvement of gas sensing mainly focus
on two aspects: (1) Design of different working principle devices;
(2) surface modification on graphene and composite with other materials
(i.e . metal, metal oxide and organic polymer). The
specific adsorption sites can be achieved, resulting the improvement
of selectivity. This review will present and summarize recent achievements
of graphene-based gas sensor in both aspects and also predict the
potential research direction in the future. According to different working mechanism, graphene-based gas sensor
can be classified as resistive type, field-effect-transistor (FET)
type, mass sensitive type, and micro-electromechanical system (MEMS)
type. Each kind has its advantages. Thanks to the simple manufacture
process, resistive gas sensor is investigated broadly. Compared to
passive resistive sensor, the active FET sensor exhibits better performance
in sensitivity and stability generally. As for mass sensitive sensor,
the unique mechanism can provide a new device structure different
from the other three types. However, concerning the compatibility
with integrated circuits (IC) manufacture, MEMS sensor can be a good
choice. Materials with high specific surface area are able to provide more
adsorption sites. Consequently, sensor performance can be improved
sharply. Therefore, surface modification on graphene and composite
with other materials attracts broad attention recently. By changing
the density and the type of functional groups on graphene surface,
specific adsorption sites can be achieved. Hence, the ability for
selective gas detection is enhanced. Besides, graphene-based composite
with other materials (i.e. metal, metal oxide and organic polymer)
is another effective strategy to optimize sensor performance. In conclusion, lots of achievements and big breakthroughs for graphene-based
gas sensor have been made in recent years. Especially the obvious
enhancement for sensitivity (as low as for single molecule detection)
and gas selective detection, graphene-based gas sensor exhibits great
advantage compared with traditional sensors. However, the time-consuming
process of gas adsorption and desorption hampers the real-time measurements
due to the long response and recover time. Therefore, improvement
in response and recover performance will be a potential research direction
in the future. In addition, the integration of different kinds of
gas sensors even other types of sensors will be a trend. Also, it
will be a desirable fundamental research to give explanations for
the sensing mechanism as well as to investigate the dynamic interaction
between gas molecules and graphene. Recently, it is believed that
with the help of special in - situ holder, researchers can launch experiments in transmission electron
microscope (TEM) to explore this fundamental study.
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