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Sensors Based on 2D Materials
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Sensors Based on 2D Materials

Sensors have a wide range of uses in modern civilization, including healthcare, security, forensics, and environmental protection. Sensors made with microfabrication processes are very appealing. Two-dimensional (2D) materials have promise as sensor building blocks. Their atomically thin nature, flat surfaces, and ability to form van der Waals heterojunctions open the way for multifunctional functionality.

The primary premise of 2D sensing materials is to detect changes in conductivity caused by the adsorption of chemical or biological molecules that might behave as electron donors or acceptors. The huge surface-to-volume ratio of 2D materials enables for highly sensitive detection of molecules adsorbed on their surface. We produce functionalized 2D materials for low-cost and high-performance sensor devices using plasma-assisted or optically modified processes.

Alfa Chemistry can create 2D material solutions that are unique to our customers' needs. Please get in touch with us right away so that we can assist you with your sensor application research.

Gas Sensors

The development of scalable, selective, and extremely sensitive gas sensors is becoming more important as environmental concerns, air pollution, and climate change grow. Environmentally dangerous gases such as NH3 and NOx can also be detected using 2D materials. Due to its unique electrical properties, 2D TMDC has been effectively employed to construct nanoelectronic devices in gas sensing. In gas sensing, electronic instruments are used. Alfa Chemistry has been investigating the use of 2D material-based sensors for this purpose in recent years.

Schematic of the low-temperature plasma-assisted selenization process of the MOx film.Fig 1. Schematic of the low-temperature plasma-assisted selenization process of the MOx film. (Nan H, et al. 2019)

By converting WO3 films across a vast area with an ICP plasma source, we were able to achieve a low-temperature synthesis of big-area WS2 films. When exposed to NH3, the WS2 films respond by increasing their electrical conductivity. This indicates that NH3 is a charge donor for the nWS2 type. The NH3 concentration has a linear relationship with the sensor response. The sensor's detection limit of 1.4 ppm at ambient temperature indicates that it is sensitive enough for a variety of applications.

By synthesizing large-area WSe2 on a flexible PI substrate, Alfa Chemistry was able to detect NOx. At temperatures as low as 250°C, WSe2 was created via an ICP plasma-assisted selenization method of WO3. The films have a sensitivity of 20% at 25 ppb and a detection limit of 0.3 ppb at ambient temperature, indicating that they might be used to construct a low-cost flexible sensor with high sensitivity.

Humidity Sensors

Humidity sensors can use plasma-functionalized graphene films as active elements. Alfa Chemistry uses O2 plasma to create functionalized graphene sheets with varying quantities of oxygen dopants. By designing graphene oxide films and transferring them to flexible plastic substrates, we were able to achieve periodically varying humidity responses. The interaction of water molecules with the oxygen functional groups in the plasma-treated graphene is credited with the sensing observation. Water molecules can establish hydrogen bonds with the added oxygens, doping the graphene sheet. When compared to pristine graphene films, this bonding is known to be stronger than the van der Waals physical adsorption of water, making it more sensitive to humidity.

A humidity sensor based on a MoS2 thin film synthesized on PI substreate, which showed resistance change toward different RH from 15% to 95%.Fig 2. A humidity sensor based on a MoS2 thin film synthesized on PI substreate, which showed resistance change toward different RH from 15% to 95%. (Ahn C, et al. 2015)

Biosensors

A biosensor is described as a device containing at least two key components, a bioreceptor, and a physicochemical sensor, that can sense biological signals as input and generate multiple readout signals as output. Because 2D materials have outstanding electrical and physicochemical properties, biosensors have been made out of naturally occurring 2D layered materials with biocompatibility, such as graphene. Alfa Chemistry has a lot of experience in this field and can help customers find the right 2D materials and applications.

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References

  1. Nan H, et al. (2019). "Recent Advances in Plasma Modification of 2D Transition Metal Dichalcogenides." Nanoscale. 11: 19202-19213.
  2. Ahn C, et al. (2015). "Low-Temperature Synthesis of Large-Scale Molybdenum Disulfide Thin Films Directly on a Plastic Substrate Using Plasma-Enhanced Chemical Vapor Deposition." Adv. Mater. 27(35): 5223-5229.

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