Ultra-sensitive Detection Of Explosives Based On Photonic Crystal Fluorescence Enhancement In Liquid Phase

In 1987 Yablonovitch controlled the spontaneous emission of light using the density of states of photonic bandga;John proposed that the periodic distribution of dielectric materials lead to Anderson local effect.Photonic crystals(PCs),a periodic arrangement of dielectric materials has been rapidly developed.The photon forbidden band formed by periodically distributed dielectric materials with different refractive indices has the ability to regulate the propagation of photons,including suppression and enhancement of spontaneous radiation.Photonic crystals are widely used in photonic devices such as high-reflection mirrors,fluorescence-enhanced sensors,optical waveguides and so on.In this paper,monodisperse polystyrene microspheres with positive and negative charges on the surface were synthesized by dispersion polymerization and emulsion polymerization,respectively.A modified St?ber method was used to prepare silica-encapsulated polystyrene microspheres.The hollow sphere photonic crystals with different photonic band gaps and dense silica shell structures were prepared by vertical convection self-assembly technique and hightemperature calcination techniques.The hollow sphere photonic crystals were used to enhance fluorescence emission to achieve ultra-sensitive detection of explosives in liquid phase.The main results were summarized,as follows:(1)Polystyrene microspheres with different surface charge were prepared,the high sphericity,narrow particle size distribution(<4%)and controllable particle size(180-300 nm).Microspheres were obtained by adjusting the initiator dosage and monomer styrene content.(2)For the modified St?ber method,the hollow spheres with adjustable morphology were prepared,and the p H of the reaction system was adjusted to obtain hollow spheres with fine surface roughness.By adjusting the amount of TEOS,the shell thickness of hollow spheres can be controlled.(3)The differences in fluorescence enhancement at the forbidden band positions were studied.The results show that the blue bandgap has the best effect on the fluorescence emission optical gain,which is about 13 times stronger.(4)The sensitivity and selectivity of explosive molecules in liquid phase were investigated by using hollow sphere photonic crystal fluorescence sensing technology.By detecting different concentrations of TNT molecules in the liquid phase,ultra-sensitive detection of photonic crystal fluorescence sensing technology was proved;The trace detection of different explosive molecules proved the selectivity of the method.