Fabrication And Application Of Electrochemical Sensors Based On Molecularly Imprinted Polymer Films

Molecularly imprinted polymer (MIP) is a novel three-dimensional cross-linked polymer with molecular recognition sites designed for a particular analyte. The electrochemical sensors based on it own lots of advantages such as good selectivity, high stability and long service life, thus they become one of the research hotspots. Furthermore, by combining with nanomaterials and ionic liquids with molecular imprinted polymer, the characteristics and performance of sensors can make be further improved, so the research in this area is very active in recent years. In this dissertation, the electrochemical sensors based on the composite materials containing of molecularly imprinted polymer, graphene and ionic liquid are constructed successfully, the main study content and results as the followings:(1) A novel electrochemical sensor for the detection of methyl parathion was constructed. It was fabricated by coating a GCE with graphene oxide (GO) ionic liquid mixture, followed by methyl parathion molecularly imprinted poly(methacrylic acid) suspension. Then made GO turn to graphene by electrochemical reduction. In this configuration, ionic liquid had a good film-forming performance. Meanwhile, the introduced graphene and ionic liquid exhibited noticeable enhanced sensitivity to methyl parathion. Under the optimized conditions, the peak current of methyl parathion was linear to its concentration in the range of 0.010-7.0 μmol·L-1 with a sensitivity of 12.5 μA/mol·L-1 mm 2, and the detection limit was 6 nmol·L-1 (S/N=3). The sensor also displayed high selectivity and stability. It was successfully applied to the determination of methyl parathion in samples.(2) A novel molecularly imprinted electrochemical sensor was fabricated by dropcasting of tartrazine imprinted poly(4-vinylpyridine) suspension on a glassy carbon electrode surface, which was modified by Pt nanoparticals encapsulated IL functionalized MWNTs hybrid (MWNTs-IL@PtNPs). The novel hybrid was prepared by Click chemistry, and it had large surface area, high conductive ability and demonstrated good electrochemical response to tartrazine. Under the optimized conditions, the peak current was linear to tartrazine concentration in the ranges of 0.03～5.0 μmol·L-1 and 5.0-20 μmol·L-1 with sensitivities of 0.72 μA/μmol·L-1 mm2 and 0.24 μA/μmol·L-1 mm2, respectively; the detection limit was 8 nmol·L-1 (S/N=3). The sensor could be applied to the determination of tartrazine in practical samples.(3) A water-compatible sunset yellow molecularly imprinted polymer (MIP) was prepared by using ionic liquid 1-(α-methyl acrylate)-3-allylimidazolium bromide as functional monomer, which could interact with sunset yellow through π-π, hydrogen-bonding and electrostatic interaction. The resulting MIP particles size used ionic liquid as monomer were smaller in comparison with the other two kinds of MIPs (prepared with methacrylic acid and 4-vinylpyridine as monomers), and they were also more uniform. Hence they had larger specific surface area, and were favorable for molecular recognization. When the material was supported on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of sunset yellow, the resulting electrochemical sensor presented good analytical performance. Under the optimized conditions, the linear detection range of the sensor was 0.010-1.4μmol·L-1 and 1.4-16 μmol·L-1 with sensitivities of 5.0 μA/μmol·L-1 mm2 and 1.4 μA/μmol·L-1 mm2 respectively; the detection limit was 4 nmol·L-1 (S/N=3). The sensor was successfully applied to the determination of sunset yellow in some soft drinks, and the acceptable recovery manifested its feasibility.(4) A novel water-compatible surface-imprinted ionic liquid (IL) polymer was synthesized on multi-walled carbon nanotubes (MWNTs) through reversible addition-fragmentation chain transfer (RAFT) precipitation polymerizationm. Owing to the intrinsic advantages of RAFT precipitation polymerizationm and surface imprinting technology, the obtained imidacloprid imprinted material showed enhanced adsorption capacity and mass transfer rate. When it was supported on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of imidacloprid, the resulting electrochemical sensor presented high sensitivity, selectivity, stability and reproducibility. Under the optimized conditions, the peak current of imidacloprid was linear to its concentration in the range of 0.2-24 μmol·L-1 and the detection limit was down to 0.08 μmol·L-1 (S/N=3). It was successfully applied to determine imidacloprid in real samples such as cabbage and apple peel, which had high recovery.(5) A novel brucine imprinted polymer on MWNTs was prepared by RAFT precipitation polymerization. The polymer was further grafted with hydrophilic poly(glycerol monomethacrylate) brushes to improve its water-compatibility. The obtained molecularly imprinted material showed enhanced accessibility to brucine and improved selective recognition property in water medium. When the material was supported on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of brucine in H2SO4 solution, the resulting electrochemical sensor presented good performance. Under the optimized conditions, the peak current was linear to brucine concentration in the ranges of 0.006-0.6 umol·L-1 and 0.6-5.0 μmol·L-1 with sensitivities of 15.3 μA/μmol·L-1 mm2 and 5.4 μA/μmol·L-1 mm2, respectively; the detection limit was 2 nmol·L-1 (S/N=3). The proposed sensor also exhibited excellent stability and good reproducibility. It was successfully applied to the determination of brucine in practical samples and the recovery was acceptable.(6) The RAFT chain-transfer agent was synthesized on the surface of AuNPs using Click chemistry, then an imprinted polymer with hydrophilic polymer brushes was prepared on the RAFT chain-transfer agent modified AuNPs by RAFT precipitation polymerizationm, mediated by hydrophilic polyethylene glycol macromolecular cochain-transfer agent. The obtained molecularly imprinted material showed improved accessibility to fenitrothion and recognition property in water medium. When the material was immobilized on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of fenitrothion, the obtained sensor presented linear response in the range of 0.01-5 μmol·L-1, with a sensitivity of 6.1 μA/μmol·L-1 mm. The low limit of detection was 8 nmol·L-1 (S/N=3).