•An alkyl-functionalized ionic liquid was used as monomer, stabilizer and catalyst to prepare MIPs.•The MWCNTs@BSA-MIPIL was prepared via a multi-step sol-gel route.•The imprinting conditions were optimized by investigating molecular interactions between templates and monomers.•The MWCNTs@BSA-MIPIL was found to be pH-responsive.•The MWCNTs@BSA-MIPIL demonstrated high adsorption capacity, good imprinting effect and strong shape selectivity to BSA.A pH-responsive surface molecularly imprinted poly(ionic liquids) (MIPILs) was prepared on the surface of multiwall carbon nanotubes (MWCNTs) by a sol-gel technique. The material was synthesized using a 3-aminopropyl triethoxysilane modified multiwall carbon nanotube (MWCNT-APTES) as the substrate, bovine serum albumin (BSA) as the template molecule, an alkoxy-functionalized IL 1-(3-trimethoxysilyl propyl)-3-methyl imidazolium chloride ([TMSPMIM]Cl) as both the functional monomer and the sol-gel catalyst, and tetraethoxysilane (TEOS) as the crosslinking agent. The molecular interaction between BSA and [TMSPMIM]Cl was quantitatively evaluated by UV–vis spectroscopy prior to polymerization so as to identify an optimal template/monomer ratio and the most suitable pH value for the preparation of the MWCNTs@BSA-MIPILs. This strategy was found to be effective to overcome the problems of trial-and-error protocol in molecular imprinting. The optimum synthesis conditions were as follows: template/monomer ratio 7:20, crosslinking agent content 2.0–2.5 mL, temperature 4 °C and pH 8.9 Tris–HCl buffer. The influence of incubation pH on adsorption was also studied. The result showed that the imprinting effect and selectivity improved significantly with increasing incubation pH from 7.7 to 9.9. This is mainly because the non-specific binding from electrostatic and hydrogen bonding interactions decreased greatly with the increase of pH value, which made the specific binding affinity from shape selectivity strengthened instead. The polymers synthesized under the optimal conditions were then characterized by BET surface area measurement, FTIR, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The adsorption capacity, imprinting effect, selective recognition and reusability were also evaluated. The as-prepared MWCNTs@BSA-MIPILs were also found to have a number of advantages including high surface area (134.2 m2 g−1), high adsorption capacity (55.52 mg g−1), excellent imprinting effect (imprinting factor of up to 5.84), strong selectivity (selectivity factor of 2.61 and 5.63 for human serum albumin and bovine hemoglobin, respectively), and good reusability.A pH-responsive bovine serum albumin molecularly imprinted poly(ionic liquids) was prepared on the surface of multiwall carbon nanotubes via a sol-gel route. The specific binding from shape selectivity was significantly strengthened by controlling the non-specific binding by adjusting the incubation pH value to 9.9. The use of ionic liquids as stabilizers, functional monomers and sol-gel catalysts was found to be a promising strategy for the preparation of water compatible molecularly imprinted polymers for protein molecules.

A series of novel protein molecularly imprinted polymers (MIPs) were synthesized through a surface molecular imprinting technique by using bovine serum albumin (BSA) as a template, acrylamide modified multi-walled carbon nanotubes (MWCNTs-AAm) as substrates, and allyl-functionalized ionic liquids (ILs) as monomers. The MWCNTs@BSA-MIPILs synthesized under different monomer/template/cross-linker ratios were characterized by FTIR, SEM and BET analyses. The adsorption kinetics and isotherm, imprinting effect, selectivity and competitiveness, reusability, and practical applicability were evaluated in detail. The influence of the outside diameters of MWCNTs and the anion types of ILs on the imprinting effect of the MWCNTs@BSA-MIPILs was also studied. The MWCNTs with smaller diameters (<8 nm and 10–20 nm) were more beneficial for the preparation of the surface imprinted polymers. The MIPs prepared with IL monomers composed of anions with low nucleophilicity and hydrogen bond basicity (PF6−), and high steric effect (CF3SO3−) were found to have a better imprinting effect in comparison with those prepared with Cl− and BF4−-based IL and the traditional acrylamide monomers. They also exhibited higher selective recognition ability for BSA than for human serum albumin, lysozyme, trypsin and bovine hemoglobin. The imprinting and selectivity factors were greatly improved in a binary protein solution containing BSA and bovine hemoglobin. The developed MWCNTs@BSA-MIPILs were also successfully used for the purification of BSA from bovine calf serum. These results indicated that the PF6− and CF3SO3−-based ILs, for their important role in stabilizing biomacromolecules, will be ideal functional monomers for the development of biocompatible MIPs for protein molecules.

•Two crown ether functionalized ionic liquids with sol–gel reactive functional groups were synthesized.•The ionic liquids were used as selective stationary phase for solid phase microextraction.•The crown ether functionalized ionic liquid-based fibers were prepared by sol–gel reaction approaches.•The fibers had “bubble-like” surface characteristics, high thermal and chemical stability.•The fibers had high selectivity and extraction efficiency for medium polar to polar compounds.In this work, two novel crown ether functionalized ionic liquid (FIL)-based solid phase microextraction (SPME) fibers were prepared by sol–gel technology using the synthesized 1-(trimethoxysily)propyl 3-(6′-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([TMSP(Benzo15C5)HIM][N(SO2CF3)2]) and 1-allyl-3-(6′-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([A(Benzo15C5)HIM][N(SO2CF3)2]) as selective stationary phases. Owing to the introduction of trimethoxysilypropyl to the imidazole cation, the [TMSP(Benzo15C5)HIM][N(SO2CF3)2] could be chemically bonded to the formed sol–gel silica substrate through the hydrolysis and polycondensation reaction. Similarly, the [A(Benzo15C5)HIM][N(SO2CF3)2] was able to participate in the formation of the organic–inorganic copolymer coatings through the free radical crosslinking reaction. These two fibers were determined to have “bubble-like” surface characteristics analogous to a previously prepared [A(Benzo15C5)HIM][PF6]-based fiber. Their thermal stabilities were much higher than that of the [A(Benzo15C5)HIM][PF6]-based coating. They were capable of withstanding temperatures as high as 400 °C without evident loss of the crown ether FILs. They also had strong solvent, acid and alkali resistance, good coating preparation reproducibility and high selectivity for medium polar to polar compounds. The high selectivity of these two fibers could be attributed to the strong ion-dipole, hydrogen bonding and π–π interactions provided by the synergetic effect of ILs and benzo-15-crown-5 functionalities. Moreover, the selectivity of these two fibers was rather different although the structures of these two crown ether FILs were very similar. This is maybe because the relative contents of the crown ether FILs chemically bonded to the organic–inorganic copolymer coatings were quite different when prepared by different sol–gel reaction approaches.The proposed crown ether FIL-based fibers have special “bubble-like” surface characteristic due to the introduction of the hexanoyl substituted benzo-15-crown-5 to the imidazole cation.

Three alkoxyl-functionalized ionic liquids, 1-(3-triethoxysilyl propyl)-3-methyl imidazolium hexafluorophosphate (TESPMIM[PF6]), 1-(3-triethoxysilyl propyl)-3-methyl imidazolium tetrafluoroborate (TESPMIM[BF4]), and 1-(3-triethoxysilyl propyl)-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide (TESPMIM[N(SO2CF3)2]), were synthesized and used as selective coating materials to prepare chemically bonded ionic-liquid-based organic–inorganic hybrid solid-phase microextraction (SPME) fibers by sol–gel technology. A possible mechanism of the sol–gel process is proposed, and the successful binding of ionic liquids to the formed silica substrate was confirmed by Fourier-transform infrared spectroscopy (FT-IR). These ionic-liquid-based sol–gel coatings have porous surface structure, high thermal stability, strong solvent resistance, wide pH application range, good coating preparation reproducibility, special selectivity, and extraction efficiency for both polar and nonpolar compounds, such as phenolic environmental estrogens, fatty acids, aromatic amines, alcohols, phthalate esters, and polycyclic aromatic hydrocarbons. The TESPMIM[PF6]- and TESPMIM[BF4]-coated fibers have much lower thermal stability (to 300 and 285 °C, respectively) than TESPMIM[N(SO2CF3)2]-coated fiber (to 454 °C). However, the selectivity of these two fibers is higher towards strong polar analytes, while lower towards medium polar or nonpolar analytes compared with TESPMIM[N(SO2CF3)2]-based fiber. This could be explained by the fact that different counteranions in ionic liquid structures have different steric hindrance, nucleophilicity, hydrophobicity, and ability to form hydrogen bonds, resulting in significant difference in the characteristics of the ionic-liquid-based SPME fibers, such as the surface morphology, thermal stability, selective extraction ability, etc. This work demonstrates that the performance of the ionic-liquid-based coatings can be simply tuned by changing the counteranions incorporated into the ionic liquid structures.

A novel sol–gel-coated ionic liquid-based ([AMIM][N(SO2CF3)2]–OH-TSO) fiber was successfully applied for the determination of phthalate esters (PAEs) in agricultural plastic films by ultrasonic extraction (UE) combined with solid phase microextraction–gas chromatography (SPME–GC) due to its high thermal stability, specific selectivity and extraction efficiency. The extractant for UE and the adsorption time for SPME were optimized to achieve higher extraction efficiency. The desorption temperature and time were also optimized to avoid the carryover effect of previous extraction, and ultimately improve the precision and accuracy of the method. The [AMIM][N(SO2CF3)2]–OH-TSO fiber showed comparable, or even higher response to most of the investigated PAEs than the commercial PDMS, PDMS–DVB and PA fibers. The carryover problem, often encountered when using commercial fibers, had been eliminated when desorption was performed at 360 °C for 8 min. The proposed SPME–GC method showed good linearity over three to four orders of magnitude, and low limits of detection ranged from 0.003 to 0.063 μg L−1. The relative standard deviation values obtained were below 10%, and the recoveries were in the ranges of 90.2–111.4%. Some of the PAEs studied were detected at very high concentration in these agricultural plastic film samples, resulting in a potential risk of crop damage, environmental contamination and human health exposure.Highlights► A thermally stable ionic liquid-based sol–gel coating ([AMIM][N(SO2CF3)2]–OH-TSO) as solid phase microextraction fiber. ► An ultrasonic extraction–solid phase microextraction–gas chromatography method for the determination of phthalate esters in agricultural plastic films. ► The carryover problem, often encountered when using commercial fibers, has been eliminated when desorption was performed at 360 °C for 8 min. ► The developed fiber has comparable or even higher response to PAEs than the commercial PDMS, PDMS–DVB and PA fibers.

A novel crown ether functionalized ionic liquid (IL), 1-allyl-3-(6′-oxo-benzo-15-crown-5 hexyl) imidazolium hexafluorophosphate was synthesized and used as selective stationary phase to prepare task-specific IL-based solid phase microextraction (SPME) fibers by sol–gel method and free radical cross-linking technology. The underlying mechanism of the sol–gel reaction was proposed and the successful chemical bonding of the crown ether functionalized IL to the formed hybrid organic–inorganic copolymer coating was confirmed by FT-IR spectroscopy. The performance of this in situ created crown ether functionalized IL-based SPME fibers, was investigated in detail. The coating has porous surface structure, stable performance in high temperature (to 340 °C) and in different solutions (water, organic solvent, acid and alkali), and good coating preparation reproducibility. In contrast to the sol–gel derived 1-allyl-3-methyl imidazolium hexafluorophosphate-based coating prepared in our previous work with the identical procedure, the extraction performance of this newly developed sol–gel crown ether functionalized IL-based coating was superior for alcohols, phthalate esters, phenolic environmental estrogens, fatty acids and aromatic amines due to the introduction of benzo-15-crown-5 functional group in IL structure. Moreover, it was shown to provide higher or comparable extraction efficiencies for most analytes studied than did the commercial PDMS, PDMS/DVB and PA fibers.

In this work, two allyl-functionalised ionic liquids (ILs), 1-allyl-3-methylimidazolium hexafluorophosphate and 1-allyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide, were used as selective coating materials to prepare chemically bonded ILs-based organic–inorganic hybrid solid phase microextraction fibres. These fibres were prepared with the aid of γ-methacryloxypropyltrimethoxysilane as bridge using sol–gel method and free radical cross-linking technology. The underlying mechanisms of the sol–gel reaction were proposed, and the successful binding of these functional ILs to the sol–gel substrate was confirmed by Fourier transform infrared spectroscopy. These IL-based sol–gel coatings had porous surface structure, high thermal stability, a wide range of pH stability, strong solvent resistance and good coating preparation reproducibility. They also had high selectivity and sensitivity towards strong polar phenolic environmental estrogens (PEEs) and aromatic amines due to the strong electrostatic interactions, hydrogen bonding and π–π interactions provided by the special molecular structure of these imidazolium ILs. Moreover, their characteristics were somewhat different depending on the type of anions in the IL structure. The practical applicability of these IL-based sol–gel coatings was evaluated through the analysis of PEEs in two real water samples. The detection limits were quite low, varying from 0.0030 to 0.1248 μg L−1. The linearity was very good in the range of 0.1 to 1000 μg L−1 for most analytes, and the relative standard deviation values were below 6%. The relative recoveries were between 83.1 and 104.1% for lake water and between 89.1 and 97.1% for sewage drainage outlet water.