Template Imprinting Versus Porogen Imprinting of Small Molecules: A Review of Molecularly Imprinted Polymers in Gas Sensing

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.

Facile synthesis of core–shell structured magnetic Fe3O4@SiO2@Au molecularly imprinted polymers for high effective extraction and determination of 4-methylmethcathinone in human urine samples

In this study, a novel material of core–shell structured magnetic molecularly imprinted polymers (Fe3O4@SiO2@Au (FSA)-MIPs) was successfully prepared for the rapid and selective determination of 4-methylmethcathinone (mephedrone, 4-MMC). The adsorption capacity of FSA-MIPs is 34.7 mg·g−1 at 308 K, which is significantly higher than magnetic non-imprinted polymers profiting from the imprinting effect. The FSA-MIPs have a short equilibrium (20 min) and could be reused more than six times. Moreover, the selectivity coefficients of FSA-MIPs for 4-MMC, 3,4-dimethylmethcathinone, butylone, 4-ethylmethcathinone, acetylfentanyl, and methylene blue are 4.01, 5.65, 7.62, 12.30, and 20.87 respectively, further indicating the markedly enhanced binding selectivity of FSA-MIPs. As an adsorbent, the FSA-MIPs were successfully applied for effective extraction of 4-MMC in three human urine samples with the recovery rates ranging from 85.5–92.6%. The results confirmed that the FSA-MIPs have good prospects in the extraction and separation of synthetic cathinones, which is suitable for further application in the criminal sciences field.

Effects of chitosan and Tween 80 addition on the properties of nanofiber mat through the electrospinning

Chitosan (CS) with excellent biomedical properties was mixed with polyvinyl alcohol (PVA) to be used as the spinning solution. The spinning solutions with various concentrations of CS:PVA from 10:90% to 50:50% (v/v) were investigated. Tween 80 (T80) was added in the spinning solutions of CS and PVA. The nanofiber mats with and without T80 addition obtained from the spinning solutions by electrospinning technique were investigated and addressed. The results showed that the viscosity of the CS and PVA spinning solutions increased with increasing the CS concentration, whereas the viscosity decreased after T80 addition. The nanofiber mats with 10–30% CS concentrations were prepared successfully as a smooth surface and high dense nanofiber mat. The average diameter of the nanofiber decreased with increasing the CS concentration. The increase in the CS concentration of the nanofiber mat can increase the mechanical and antibacterial properties, whereas the wettability and drug release property were decreased. Moreover, the nanofiber mats with T80 addition had higher mechanical property and wettability than the nanofiber mats without T80 addition. Finally, the T80 addition can enhance hydrophilicity and promote the drug release property of the nanofiber mat.