| The integration of nanoscale building blocks with well-controlled architectures intoactive nanostructured functional materials is a great technical challenge. Photonic crystalsare an emerging type of nano structural functional materials that possess periodicity in therefractive index. Due to the periodicity in dielectric materials, photonic crystal materialspossess a photonic band gap and special light manipulation properties. As a new typeadvanced functional polymers, photonic crystals demonstrate wide application in opticalsensing materials and optical devices.One important research direction of photonic crystal is the preparation of photoniccrystal structures. Three-dimensional (3D) photonic crystal fabrication has been widelyinvestigated. However, the formation of two-dimensional (2D) photonic crystals has beenreported only until recent years. For instance, most photonic crystal heterostructures whichcan enrich the optical properties are prepared based on3D photonic crystals. However, thepreparation procedure is time-consuming and the ordering is likely to be damaged. For2Dphotonic crystal preparation, even though the interface self-assembly affords an efficientmethod, it needs careful operation.Another important research area is photonic crystal structure-based stimuli-responsivematerial by combining intelligent material with photonic crystal. The raid response andself-reporting properties make these photonic crystal sensing materials becomingincreasingly attractive in the area of chemical and biological sensing. Unfortunately, thereare still some problem exist. First, the selectivity of many photonic crystal bio-chemicalsensors are not desirable. Second, traditional photonic crystal sensing materials are inverseopal structures prepared by using3D photonic crystals as templates. These preparationprocedures are tedious. Third,2D photonic crystal sensing materials are not studied widelyas3D photonic crystals yet. In addition, the target analytes are limited due to that most ofthe materials are based on functional hydrogels.In order to solve the problems encountered in the fabrication of photonic crystals andapplication of responsive photonic materials, in this thesis, we are focusing on the fabrication of photonic crystals and development of photonic crystal sensing materials. Inphotonic crystal preparation, firstly, several3D and2D photonic crystals with optical bandin visible region were fabricated; secondly, photonic crystal heterostructures based on2Dphotonic crystal were prepared; finally, a simple method for the preparation of free-standing2D colloidal crystal film were developed. In photonic crystal responsive materials, firstly,glucose responsive inverse opal hydrogel films and p-nitrophenol responsive colloidalcrystal films with high selectivity were developed; secondly, several photonic crystalsensing materials based on2D photonic crystal were prepared. These2D photonic crystalsensors exhibit fast and colorimetric response to glucose, pH, and fatty acid, respectively.The main contents and results are summarized as follows:1) Monodisperse size-controlled poly methyl methacrylate (PMMA), poly styrene (PS)and silica colloidal microspheres were fabricated, and formed3D colloidal crystals usingvertical deposition self-assembly methods. The resulting3D photonic crystals with wellordering and good monochromaticity exhibit strong Bragg diffraction in the visible region.2) Larger size (>500nm) PS and PMMA colloidal microspheres were prepared, andassembled into2D photonic crystals at the air/water interface by a needle tip flow method.The Bragg diffraction, Debye diffraction ring detection and structural color were used tocharacterize the optical property of these photonic crystals. Further more, two-and three-layer colloidal crystal heterostructures (CCHs) based on2D photonic crystals werefabricated by successive deposition of2D PMMA colloidal monolayer colloidal arrays ofdifferent particle sizes.The structure and optical properties of2D CCHs were characterizedby SEM, reflectance spectra, Debye diffraction rings and their diffracted wavelengths. Thelayers maintain their spacing and ordering and the2D CCHs diffraction measurementssuggest that the optical properties of the composite colloidal heterostructures arise mainlyfrom the independent diffraction of the individual2D colloidal arrays.3) A novel method to fabricate thin free-standing2D PMMA colloidal crystal filmswas developed. PMMA colloids were dispersed into methylbenzene/diethyl ether solution,and then one droplet of the suspension solution was dropped on the water surface. ThePMMA dispersion spreads on water surface and self-assembled into a thin2D colloidal crystal free-standing film. The obtained2D colloidal crystal film is mechanically strong andcan be transferred to mental mesh (~1cm2). In addition, it efficiently diffracts light as2Dphotonic crystal does which is promising in separation and analyticaltechnique.4) A glucose-sensitive inverse opal hydrogel based on the combination of photoniccrystal templating and molecular imprinting technique were fabricated. At pH9.6, theunique3D ordered porous hydrogel revealed selective optical changes in response toglucose concentration with a detection limit of1mM. In addition, by a self-assemblyapproach using p-nitrophenol (PNP) imprinted colloidal spheres, PNP responsive colloidalcrystal was prepared. The ordering of the colloidal crystal was stabilized by attaching thesecolloidal crystal onto an adhensive tape. The results showed that the diffraction wavelengthof the imprinted colloidal crystal red-shifted more than50nm in response to30mM PNPwith a detection limit of1mM. Color change due to the diffraction light shift can beobserved.5) A novel2D photonic crystal sensing material for the visual detection of glucosewith high selectivity is developed.PS2D colloidal crystal is embedded in a phenylboronicacid (PBA) functionalized hydrogel film to diffract light to sensitively report on thehydrogel surface area. The2D photonic crystal sensor exhibits significant sensitivityforglucose across the entire human physiological glucose range at the physiological ionicstrength with a detection limit of0.1mM and response time of3min.6) A hydrogel film with a highly ordered macropore monolayer on its surface bytemplate photo-polymerization of2-hydroxethyl methacrylate-co-acrylicacid hydrogelmonomers on a2D PS colloidal crystal were fabricated. The2D inverse opal hydrogelshowed pH response across pH2to7with response time of3min. Debye diffraction ringdetection and color change detection method which are easy and low-cost were used tocharacterize the hydrogel sensor.7) In order to expand the target analytes, a proof-of-concept for introducing proteinhydrogel into photonic crystal sensing material to expand the range of analytes weredemonstrated. Bovine serum albumin (BSA) isa globular protein that functions asbloodstreamcarriers of hydrophobes such as fatty acids. This novel2D photonic crystal protein hydrogel was prepared by attaching2D colloidal crystal onto pure BSA hydrogels.The2D photonic crystal BSA hydrogel is transparent and has desired mechanical strength.The binding ofsodium dodecanoateto the protein hydrogel swells the hydrogel volumecausing shifts inthe diffraction.Fabrication of photonic crystal and their application in bio-chemical sensing materialhave attracted considerable interest due to their unique optical properties and functionality.We expect that the work presented in this thesis could provide a convenient and efficientstrategy for the development of functional materials towards bio-chemical sensingapplications. |
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