Fabrication of Functional Molecularly Imprinted Materials using Nanoparticle Building Blocks

Abstract: Molecularly imprinted polymers (MIPs) have attracted great interest in many applications including bioseparation, chemical sensing, catalysis, drug delivery, etc. Recently, molecularly imprinted nanoparticles have become accessible due to a number of synthetic methods that have been developed. The high molecular binding selectivity, fast binding kinetics and colloidal stability make MIP nanoparticles ideal building blocks for fabrication of new multifunctional materials. As examples, magnetic susceptibility, fluorescence response, plasmonic enhancements have been integrated into MIP materials by different physical entrapments or chemical conjugation methods. In this thesis, the use of nanoparticle building blocks for preparation of functional MIP materials is studied. First, different chemical conjugation methods are investigated to allow MIP nanoparticles to be covalently linked to various materials extending from fluorescent molecules, magnetic nanoparticles, to hydrophilic cryogels. Click chemistry based on Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction and amine-glutaraldehyde crosslinking reaction are used to conjugate core-shell MIP nanoparticles with other functional components. To enable ordinary MIP nanoparticles to act as useful building blocks, a simple photo-conjugation method based on perfluorophenyl azide (PFPA) has been developed. The composite materials obtained by the different chemical conjugation methods display not only high molecular selectivity, but also additional attractive features, such as magnetic susceptibility, fluorescence response, as well as macroporous structure allowing purification of complex samples. In the second part, inorganic nanoparticles are used as surfactants to stabilize oil-in-water emulsion (Pickering emulsion) to synthesize water-compatible MIP microspheres. The new MIP material exhibits high molecular selectivity and allows direct separation of target analytes in water. The chemical conjugation methods developed in this thesis have a general applicability and should provide convenient means to developing other functional materials and devices. The use of nanoparticle surfactants in molecular imprinting has enabled direct molecular separation under pure aqueous condition. The new synthetic approach based on Pickering emulsion polymerization opens new possibilities for molecularly imprinted materials, particularly in the area of bioseparation and sensing.