| Molecular imprinting technique (MIT) is becoming increasingly recognized as a powerful technique of preparing synthetic polymers that contain tail-made recognition sides for certain molecules. The most significant advantages of molecularly imprinted materials are high affinity and high selectivity to analyte, mechanical/chemical stability, low cost and ease of preparation, usage of long lifetime, and hence have attracted extensive research interests due to the potential application in purification, separation, immunoassay, biomimics, chemical and biological sensors, catalysis, environment detection, drug release and other relevant fields for its predetermination, specificity and practicability of molecule recognition.The research described in this thesis gives a brief overview of the development of novel strategies facilitating advanced understanding of the fundamental principles governing selective recognition of molecularly imprinted polymers and fluorescence emission energy transfer (FEET) at molecular level, which is a prerequisite for the rational optimization of biomimetic and sensor materials, and discusses the problems and challenges that molecular imprinting technique meets with at present. Ideal molecularly imprinted materials should exhibit these characteristic as follow: complete removal template molecules, able to be post-synthetically functionalized, homogeneous imprinted sites of high stability, high affinity, rapid binding kinetics and transduction of binding into easy readout etc. However, traditional molecular imprinting techniques often produce the polymer materials exhibiting high selectivity but low binding capacity, poor site accessibility, and slow binding kinetics due to most imprinted recognition sites to be embedded in high rigid polymer matrix interior. Therefore, controlling template molecules to locate in the proximity of materials surface is critical to create more effective recognition sites and to improve sites accessibility. As an alternative to these approaches, nano-sized imprinting materials may provide a potential solution to these difficulties due to their extremely high surface-to-volume ratio which lead to the recognition sites to locate in the proximity of materials surface This thesis aims at an exclusive TNT recognition and detection. The nanoshell of TNT-imprinted SiO2@MIP nanoparticles with high density imprinted sites, high selectivity, high affinity and rapid binding kinetics had been prepared by means of using nanotechnology, surface functionalized design and molecular imprinting technique etc. Moreover, molecular properties and sensitivity mechanism of nanostructured molecularly imprinted materials and fluorescence emission energy transfer (FEET) on silica surface to trace TNT molecular were also investigated.It is well known that silica has been of considerable interest because it forms the basis of technologically important materials. The ability to functionalize silica materials has prompted a renewed interest in enriching our understanding of its fundamental properties and enhancing its performance in currently existing applications. Monodisperse silica colloidal nanoparticles were suitably used as the imprinted-template substrates of surface nanostuctured molecule imprinting through the chemistry modification. because this support offers pronounced advantages over the organic supports, such as: (a) the immobilization on silica results in a great variety of silylating agents, allowing a myriad of pending functional groups in the inorganic framework; (b) functional groups immobilized on the surface react easier oninorganic support, whose behavior, differs from the organic support. (c) the inorganic supports do not swell in organic solvents; (d) it is resistant to organic solvent; (e) silica has a high thermal resistance and (f) the controllable size and dispersivity of the particle.Monodisperse silica colloidal particles that are uniform in size and shape have extensive application not only in the field of physical chemistry dealing with dynamic behavior and stability of particle systems, but also in industries involving catalysts, chromatography, ceramics, pigments, photographic emulsion, etc. Monodisperse silica particles can be prepared by hydrolysis and condensation of alkoxysilanes in a mixture of alcohol, water, and ammonia. The results have demonstrated the formation of monodisperse silica particles through the hydrolysis and condensation of tetraethylorthosilicate (TEOS) in ethanol with ammonia as catalyst, many studies have been made on the many mechanisms of this reaction system. However, herein, the size and dispersivity of silica particles were investigated through the effective factors of reaction, such as, reactant concentration (TEOS, ammonia aqueous and demonized water), reaction temperature. Therefore, the suitable size and dispersivity of silica particles that is imprinted as support were achieved by the effective parameters of change reaction condition. Subsequently, the monodispersive silica particles are chemically modified using a two-step procedure to obtain the acrylamide-monomer-capping silica particles. Firstly, Aminopropyl modification of silica nanoparticles was carried out through the covalently attached to silica surface using 3-aminopropyltriethoxylsilane at inert solvent under nitrogen atmosphere. Then, the resultant amino end groups of APTS monolayer were further acryloylated with acryloyl chloride (CH2=CHCOCl). Finally, the AA-APTS-silica particles were obtained. The nature and morphology of particles was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and FT-IR.Herein, TNT used as analyte, a surface functional-monomer-directing strategy for the highly-dense imprinting of 2, 4, 6-trinitrotoluene (TNT) molecules at the surface of silica nanoparticles was investigated. It has been demonstrated that the vinyl functional-monomer layer of silica surface can not only direct the selective occurrence of imprinting polymerization at the surface of silica through the copolymerization of vinyl end groups with functional monomers, but also drive TNT templates into the formed polymer shells through the charge-transfer complexing interactions between TNT and the functional-monomer layer. The two basic processes lead to the formation of uniform core-shell TNT-imprinted nanoparticles with a controllable shell thickness and a high density of effective recognition sites. A stepwise progressive polymerization was designed toward the controllable preparation of high-quality shell of TNT-imprinted polymers in the silica surface. Compared to traditional imprinted particles, the imprinted nanoshell with high density of surface imprinted sites can significantly improve the binding capacity, binding kinetics and recognizing selectivity. A critical value of shell thickness for the maximum rebinding capacity was determined by testing the evolution of rebinding capacity with shell thickness, which provides new insights into the effectiveness of molecular imprinting and the form of imprinted materials. These results reported here can not only find many applications in molecularly-imprinting techniques but also form the basis of a new strategy for preparing various polymer-coating layers on silica support.Herein, TNT used as analyte, the finding of an investigation of fluorescence emission energy transfers (FEET) strategy for the ultratrace dectetion of 2, 4, 6-trinitrotoluene (TNT) in solution and vapor environments was reported. The FEET-based nanoparticle sensors were synthesized by covalently linking fluorescent dyes and amine ligands onto the surface of silica nanoparticles through the use of alkoxysilane coupling reactions. It has been demonstrated that electron-rich amine ligands (3-aminopropyl triethoxysilane, APTS) can specifically bind TNT molecule with electron-deficient aromatic ring by the charge-transfer complexing interaction, and the resultant APTS-TNT complex strongly absorbs the fluorescence emission of the chosen dye molecules. The two basic processes occurring at surface of silica nanoparticles lead to the selectivity and rapidly response to TNT by fluorescence quenching. The nanoparticle-assembled photoluminescence arrays through the etched microwells on silicon chip can sensitively detect down to several pg of TNT solution or several ppb of TNT from other types of nitrocompounds by the higher efficiency offluorescence quenching. These results reported herein will also form a novel basis ofnanosensor design for the detection of other analytes such as metal ions and biological molecules. |
