Construction And Property Study Of Functional Hybrid One Dimensional Photonic Crystals

Nature has provided a large variety of shapes and colors for living creatures.Various methods have been utilized to produce the colorful kaleidoscope.The most common approaches are coloration via pigments,dyes,or structure.The structure color is derived from periodically arranged photonic micro-/nano-structures,which is capable of manipulating the diffraction and/or reflection of light.Commonly,this structural color is more efficient and stable.It is increasingly realized that the micro/nanostructural features of materials have considerable effects on the material properties.Researchers devote much effort to mimicking natural archetypes of special structures and extraordinary functions via optimized fabrication methods.Photonic crystals?PC?are widely spread in nature.Animals such as certain butterflies and beetles use them for mimicry and survival techniques,for example,to distract predators.One dimensional photonic crystals?1DPC?are the representative type,where the periodicity exists in only one dimension.As the characteristic optical property of 1DPC,the photonic band gap?PBG?can reflect the light within a specific wavelength.The PBG presents as the structure color with the high brightness and saturation.The nature of the PBG is closely related to the structure color.The PBG can be adjusted by changing the structural parameters,while the responsive materials can cause the variation of structural parameters under the actuation of the environmental stimuli.Therefore,researchers use 1DPC to realize the visual detection of physical,chemical,biological and other environmental factors.Recent year,with the development of science and technology,the connotation and application of hybrid micro/nano-structures are expanding.Based on the excellent fluorescence?FL?,magnetic,photothermal and catalytic properties of nanomaterials,researchers have widely developed nanotechnology and successfully prepared semiconductor nanoparticles,metal/metal oxide nanoparticles and carbon dots?CDs?.These functional materials have been applied in the field of photoelectricity.The adjustment of light is the inherent property of 1DPC.The performance of photoelectric devices can be optimized by means of 1DPC.In this paper,we start from the composition of 1DPC and focus on the property of 1DPC in the light manipulation.The applications of 1DPC in optical fields such as visual detector,fluorescent controller and light-emitting diode?LED?were attained.In the second chapter,the polyelctrolyte/TiO₂ hybrid 1DPC have been established as a visible sensor to detect various charged materials,including polyelectrolytes and proteins.Polyelectrolytes were studied first;the reflectance spectra and optical images were monitored.The device succeeded in differentiating the varieties,concentrations and molecular weights of polyelectrolytes via the different shift speeds and degree of the PBG peak position.Regarding natural charged materials such as proteins,the sensor can still distinguish different types of proteins by adjusting the pH of solutions.As one kind of biomarker,the visible detection limit concentration of alpha-fetoprotein?AFP?can meet the requirements of clinical detection.Therefore,the sensor provides a general,intuitive and convenient method for the health monitoring.In the third chapter,with the aim to build a multifunctional solid fluorescent controller,a 1DPC and CdSe fluorescent layer were separated on the opposite sides of quartz substrates.The separation structure remarkably facilitates materials selection for the fluorescent controller,which allows one to freely choose the fluorescent substance and constituents of 1DPC from a wide range of available materials with the best desirable properties and without caring about the interactions between them.Fluorescent enhancement and weakened effect were successfully achieved when the excitation light was irradiated from different sides of the fluorescent device.In addition,the fluorescent intensity can be altered reversibly along with environmental pH values according to the change of a pH-responsive 1DPC,which is quite different from a previously reported quenching mode.Meanwhile,the mechanism of fluorescent variation was confirmed by the assistance of a finite-difference timedomain simulation?FDTD?.Furthermore,this device is also able to modulate fluorescent wavelength and full width at half-maximum?FWHM?by overlapping the PBG and the emission of CdSe.Therefore,this method offers a universal strategy for the fabrication of fluorescent controllers.In the fourth chapter,To optimize the broad emission of CDs,a versatile approach for narrowing the fluorescence of CDs via 1DPCs is developed.The 1DPC reported herein has sandwiched a thicker layer of CDs in the middle of two hybrid periodic laminar structures,yielding a transmittance dip.CDs are utilized as prepared without further purification.The transmittance dip is able to be tuned by altering the thickness of layers.Such background thus permits the adjustment of structural properties to narrow the FWHM and manipulate the emission color of LED device.The transmittance dip enhances the fluorescence intensity,which is quite different from the traditional color filter such as liquid crystal.Furthermore,the mechanism of fluorescent manipulation is confirmed by the assistance of a FDTD simulation.Such fluorescence tuning not only molds emission properties of CDs but also provides possibilities for the construction of more efficient devices for color purification.