Fabrication And Property Characterization Of Molecularly Imprinted Photonic Hydrogels

Molecular imprinting technique is an effective way to fabricate polymers that contain tailor-made recognition sites for certain molecular. Owing to the complementarity in the size, shape, and binding sites, the created nano-cavities made by molecular imprinting show high selectivity towards imprinted molecules. Owing to the periodic porous structure, inverse opal photonic crystals interreact with visible lights intensively, resulting in the fascinating optical properties(Bragg diffraction) and bright structural color. Based on the combination of molecularly imprinted hydrogels and inverse opal photonic crystals, Molecularly Imprinted Photonic Hydrogels(MIPHs) are fabricated successfully. The specific adsorption of MIPHs to target molecules leads to the change of the volume of MIPHs and photonic crystal lattice parameter, which results in the shift of Bragg diffraction peak and color change that can be detected by naked eyes. Therefore, the semi-quantitative for anylytes is possibly to be achieved.Herein we fabricated two kinds of MIPHs for L-Tryptophan(L-Trp) and folic acid(FA), and characterized their sensoring properties. The fabricated MIPHs showed serials of desirable features, such as high specificity and sensitivity, signal self-reporting, quick response, and well regenerative ability and reproducibility. The main contents and results are summarized as follows:(1) MIPHs with excellent inverse opal structutre were fabricated by traditional colloidal template method, where precursor infiltration process was completed by “sandwich” method or “infiltration through small angle of inclination”. In this thesis, MIPHs were prepared by “sandwich” method that is simple and convinent. Furthermore, the MIPHs film can be exfoliated from the substrate in H2 O to get a free-standing photonic crystal film, which enhanced the property of swell-deswell and allowed the application to be more convinent.(2) L-Tryptophan(L-Trp) imprinted photonic hydrogels(L-MIPHs) were fabricated through photopolymerization methods with acrylamide(AM). With the increase of the concentration of L-Trp, the Bragg diffraction peak of L-MIPHs redshifted 83 nm, and the colour change can be observed by naked eyes.(3) Molecularly imprinted photonic hydrogels(CD-MIPHs) for L-Trp based on β-cyclodextrin(β-CD) were fabricated through photopolymerization methods with acrylamide(AM) and maleic anhydride modified β-CD(MAH-β-CD). Response surface methodology(RSM) based on central composite design(CCD) was used to find the key factor playing more important role in the fabrication of the MIPHs and predict optimum polymer composition with limited number of experiments. With the increase of the concentration of L-Trp, the Bragg diffraction peak of CD-MIPHs redshifted 126 nm, and the chiral discrimination of CD-MIPHs to Tryptophan was investigated.(4) The FA-MAH-β-CD inclusion complex was firstly prepared by the inclusion prosess of folic acid(FA) with MAH-β-CD. Then molecularly imprinted photonic hydrogels(F-MIPHs) for folic acid(FA) based on β-cyclodextrin(β-CD) were fabricated through photopolymerization methods with acrylamide(AM) and maleic anhydride modified β-CD(MAH-β-CD). The detection limit of F-MIPHs was found to be equal to 10-12 mol/L.