Research On Silica Photonic Crystal Sensor And Applications Based On Environmental Detection

Photonic crystals are a new class of optical materials with spatially ordered lattice. The most important feature of photonic crystal is the band gap. The position of band gap follows the Bragg’s law, which makes it possible to achieve sensation of photonic crystal by altering one parameter of photonic crystal. In this paper, w e achieved the detection of environmental change by altering the lattice distance or the refractive index of photonic crystal.In this paper we prepared photonic crystal by spray-coating method. The major parameters in this procedure are pressure, distance and contact angle between substrate and latex, among these parameters the most important factor is contact angle, so we discussed the influence of contact angle. Firstly we spray-coated silica nanospheres on different substrate and studied the structure and reflecting spectrum to get the optimized contact angle in preparation procedure. Secondly we dissolved PVA and silica nanospheres in latex with different weight ratio of water, ethylene glycol and ethanol, choose the proper latex to prepare the photonic crystal sensor. Finally we tested reflecting spectrum caused by different concentration of water, and working curve of sensor is obtained. We tested repeatability of sensor and selectivity of sensor. The sensor we prepare displays orange in dry nitrogen w hile it turned to white when high concentration of water is bubbled in.Although the sensor can detect water, it cannot be used in detection of various vapor. In order to functionalize spheres, we prepared mesoporous silica nanospheres using monodispersed silica nanospheres. We studied the influence in addition of tetraethoxysilane and surfactant and the type of surfactant. We optimized the prepare procedure of mesoporous silica nanospheres : the concentration of tetraethoxysilane should be no more than 10 mmol/L and we choose cetyl trimethyl ammonium bromide to be the surfactant and the mass of surfactant should be around 1.5 g, we achieved to make mesoporous silica nanospheres with layer thickness around 40 nm. Using transmission electron microscopy, scanning electron microscopy and BET specific surface area test to characterize the mesoporous silica nanospheres. Using mesoporous nanospheres to fabricate photonic crystal sensor, and test its sensing properties under different gas atmosphere.