A graphene-based sensor works to detect gas molecules by measuring changes in the material’s electrical conductivity. Graphene-based gas sensors work by adsorbing gas molecules on the surface of graphene (which act as electron donors or acceptors).

  Graphene has an advantage in this field due to its very low noise. Because of this, even if no carriers are involved and only a few extra electrons are present, the carrier concentration of graphene can change significantly.

Electrochemical sensors

  It has also been shown that graphene is an effective chemical sensor in the electrolyte-gated configuration. Graphene-based high-gate insulators can be thinned to 1–5 nm in multimolar electrolytes. Even at their best, atomic layer deposition (ALD) high-gate graphene field-effect transistors (FETs) cannot match these levels.

  In DNA electrochemical sensors, electrode material for oxidase biosensors, graphene-based electrochemical sensors have been developed. Graphene performs better than carbon nanotubes in three areas; Direct enzyme electrochemistry, electrochemical detection of small biomolecules and electrolysis.

Photoelectric sensors

  The market for photoelectric sensors is basically indium tin oxide (ITO) embedded in transparent conductors. The high electrical conductivity and near transparency of graphene make it an attractive choice for transparent electrodes in photovoltaic cells and photoconductive sensors. The main advantage of graphene over ITO is that it is more compatible with flexible displays.

  A graphene photodetector works by measuring the photon flux. This detector performs measurement by converting the energy of absorbed photons into electric current. Graphene optical detectors have a much wider operating wavelength range than conventional detectors based on group IV and III-V semiconductors. In addition, graphene has a higher carrier mobility than other materials, which should be interpreted as ultrafast optical sensors.

Magnetic field sensors

  Isn’t graphene a good choice to use in magnetic field sensors? The Hall coefficient at room temperature for a conventional indium arsenide (InAs) sensor is much better than for a graphene-based sensor, but when we consider that graphene is only 0.34 nm thick, while InAs is 12 nm thick. , it is clear that the use of graphene is more suitable in terms of resistance to the Hall effect compared to InAs. In addition, unlike 2D electron gas (2DEG) devices, graphene does not need to be hidden in additional layers, which provides advantages in Hall effect sensing.

Mechanical sensors

  Mechanical sensors can detect changes in physical properties. Hempene’s mechanical sensors are capable of detecting changes in resonance frequency and measuring mass, force, pressure, strain, velocity, acceleration and weight.

  Research has shown that graphene can be successfully used as strain and pressure sensors. Graphene is used in strain and pressure sensors based on graphene as an active material to measure physical signals including strain and pressure. Due to its high level of electrical conductivity, graphene materials are often used as electrodes or conductive layers in graphene strain and pressure sensors.

  Conventional methods of transmission through graphene strain and pressure sensors include resistive, capacitive and piezoelectric. Resistive sensors convert external forces into a form of resistance that can be directly detected by a pre-built detection circuit through changes in electrical signals. This signal obtains the resistance measurement signal through the resistance change and transfers its resistance effect to the graphene.

  Capacitive sensors can detect different forms of force by converting mechanical actuation signals into displacement signals. The change in displacement leads to the change in capacitance, and the high conductivity, attractive mechanical properties, and large specific surface area of graphene make it an excellent choice for electrical conductors and electrodes in capacitive sensors.

  In the case of mechanical deformation, the piezoelectric material produces an electric charge, and this process also occurs in reverse, so that when an external electric field is applied to the piezoelectric material, it mechanically deforms. Research has also shown that single-layer graphene can detect negative piezoelectric effect, and double-layer and multi-layer graphene can detect positive piezoelectric conductivity effect.

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