Sustainable Methanol Vapor Sensor Made with Molecularly Imprinted Polymer

Dr. Mona Amit Kaushal, Arihant School of Pharmacy & Bio-Research Institute, Gujarat Technological University

Why a methanol vapour sensor at all?

Researchers are currently exploring customized molecular recognition of analytes and employing cutting-edge methods to observe changes in recognition elements. They aim to develop exceptionally sensitive and precise biosensors. Biology offers numerous examples of precise molecular recognition, with many intricate processes occurring within cells or during cell-to-cell communication. Such careful molecular recognition systems are actively studied for the development of biosensors. The problems with current gas-phase sensors include the necessity for high temperatures, the use of risky chemicals, and inefficient processes. The researchers chose methanol vapor as our target because it simultaneously poses a common industrial hazard and serves as a relatively safe analogue for volatile pollutants. The purpose of this study was to build a MIP-based gas-phase (methanol vapour) sensor using green chemistry to close this gap.

Constructing the methanol vapour sensor:

• Flask A: 15 mg of PVA was dissolved in 37.5 ml of distilled water using ultrasonication for 20 minutes at 40 degrees.
• A graphite solution (75 mg in 7.5 ml D/W) was sonicated in Flask B in the same bath until it is completely dissolved.
• 4.75 microliters of CH₃OH should be added to the dispersed solution in flask A. After 60 minutes of careful stirring and heating (to 40°C), dropwise add a 15 microliter solution of glutaraldehyde (50% w/w aq. solution).
• After 120 minutes, 6.83 ml of the graphite solution in Flask B was added, and 20 hours were spent stirring. To produce a concentration of 15mg/ml, the final solution was transferred, evaporated, and then redistributed in distilled water.
• The working electrode of the screen-printed electrode (SPE) was levelled with glutaraldehyde (0.5 L of a 50% weight percent aqueous solution) using a pipet tip.
• The SPE was then transferred to a surface at 50 °C where it was allowed to dry for about 20 minutes before the composite was drop-cast (2.2 L in two 1.1 L individual additions) onto the glutaraldehyde-activated electrode surface.
• A Bluetooth-capable, rechargeable potentiostat with an attached composite electrode was contained in a chamber with a predetermined volume of liquid methanol. Continuous cyclic voltammetry (CV) measurements were made throughout the evaporation, and DPV (differential pulse voltammetry) was added at the peak response. Following a 1 s equilibration period, sweeps were performed from 5.0 to 5.0 V.
• These sweeps were routinely carried out using CV at 0.5 V/s scan speed and 0.01 V energy step. Differential pulse voltammetry (DPV) has an energy step of 0.01 V, a scan rate of 0.1 V/s, a pulse energy of 0.2 V, and a pulse duration of 0.02 s.

Results:

Sensitivity
Minimum Observed Concentration (CV)	253 micromol/dm3
Minimum Observed Concentration (DPV)	126 micromol/dm3
Selectivity
Strong response, but below MeOH	Ethanol
Low response	Propan-2-ol, Propan-1-ol, Acetone

Conclusion:

To get beyond these restrictions, it is imperative to build synthetic molecular systems that mirror biological molecular recognition structures. Molecularly Imprinted Polymer (MIP) is One of the most recent systems of interest. MIP offers precision toward the target molecule, better affinity, durability, stability, and ease of production. To make the aforementioned sensor a commercial product and to overcome the shortage of nonrecycled reagents, more study is necessary.

Also read: Exogenous Klotho as a Cognition Booster in Aging Primates

Reference:

Cowen, T., & Cheffena, M. (2023). Molecularly imprinted polymer real-time gas sensor for ambient methanol vapor analysis developed using principles of sustainable chemistry. ACS Sustainable Chemistry & Engineering, 11(29), 10598–10604. https://doi.org/10.1021/acssuschemeng.3c02266

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