The selective sensing of gaseous target molecules is a challenge to analytical chemistry. Selectivity may be achieved in liquids by several different methods, but many of these are not suitable for gas-phase analysis. In this review, we will focus on molecular imprinting and its application in selective binding of volatile organic compounds and atmospheric pollutants in the gas phase. The vast majority of indexed publications describing molecularly imprinted polymers for gas sensors and vapour monitors have been analysed and categorised. Specific attention was then given to sensitivity, selectivity, and the challenges of imprinting these small volatile compounds. A distinction was made between porogen (solvent) imprinting and template imprinting for the discussion of different synthetic techniques, and the suitability of each to different applications. We conclude that porogen imprinting, synthesis in an excess of template, has great potential in gas capture technology and possibly in tandem with more typical template imprinting, but that the latter generally remains preferable for selective and sensitive detection of gaseous molecules. More generally, it is concluded that gas-phase applications of MIPs are an established science, capable of great selectivity and parts-per-trillion sensitivity. Improvements in the fields are likely to emerge by deviating from standards developed for MIP in liquids, but original methodologies generating exceptional results are already present in the literature.

A novel molecularly imprinted polymer nanoparticle-based assay (MINA) performed in magnetic microplates was developed as an improved high-quality alternative to existing antibody-based immunoassays.

An electrochemical gas sensor has been fabricated using molecularly imprinted polymer nanoparticles (nanoMIPs) and multiwalled carbon nanotubes on screen-printed electrodes. Methanol vapour was chosen as the target due to its toxicity as its suitability as a model for more harmful pollutant gases. The sensor functions under ambient conditions and in the required concentration range, in contrast to all previous MIP-based gas sensors for methanol. The sensitivity of the sensor was greatly improved by the addition of multiwall carbon nanotubes, resulting in a limit of detection of approximately 10 ppm. The nanoMIPs provide an inherent selectivity for the target inherent in its design. Selectivity studies were performed with structurally analogous alcohols at various concentrations, demonstrating selectivity for methanol 12.1 times that for ethanol at 2 mmol dm⁻³ and 4.2 times that for ethanol at 1 mmol dm⁻³. Interactions with isopropanol and n-propanol were found to be non-specific, and the response to water was negligible. This demonstrates an improvement over previous methanol gas sensors based on molecularly imprinted polymers. No response was observed with carbon nanotubes alone, and no selectivity was observed with non-imprinted equivalents of the nanoMIP sensor. The resulting device is by far the most practical MIP-based instrument for methanol gas sensing thus far described in the literature, being the only example capable of functioning at the necessary methanol vapour concentrations and at the required temperature and humidity. With the selectivity and sensitivity described and the simple design, the developed device provides a substantial advance in the field of molecularly imprinted gas sensors.

The solubility of polymer nanoparticles is a complex phenomenon dependent on solvent–solute and solute–solute interactions. Contrary to phase separation in standard polymerization reactions, which is a well established research area, the relationship between the solubility of polymer nanoparticles and the resulting diameter of the nanoparticles has been largely overlooked. Herein we demonstrate that the absolute size of polymer nanoparticles can be predicted (and controlled) by varying the relevant parameters of the polymerization conditions that influence the solubility and Flory parameter, χ_{s, p}. The position of the spinodal, associated with a given χ_{s, p} equivalent and determined with a simple thermodynamic model, allows an absolute value, Δχ_spinodal, to be applied in predicting polymer dimensions. The hydrodynamic diameter of particles at the primarily observed fraction was found to be dependent on D (nm) = −74Δχ_spinodal + 367 nm, where Δχ_spinodal must be positive for successful separation. Variation with total polymer fraction over a limited range can also be observed to follow a trend of approximately D (nm) = 173 ln[(xN)²10⁻³⁶/Δχ_spinodal] − 193 nm, thus giving a more general description of polymerization. We also assert the importance of separating spinodal-character phase separation from binodal-character phase separation in polymer nanoparticle synthesis. To the best of our knowledge this is the first successful Flory–Huggins based thermodynamic model of polymer nanoparticles, and should provide a useful guide to predictive design of future nanomaterials.