Abstract
Polystyrene (PS) opal and titania (TiO2) inverse opal films were fabricated by the self-assembly colloidal crystal template technique. Based on Bragg’s law, these sensors were used to detect the different concentrations of ethanol solution. The results indicated that TiO2 inverse opal films were advantageous over PS opal film for detecting the ethanol concentration. TiO2 inverse opal films sintered at 600 °C retained the highest sensitivity for ethanol concentration identification, since the anatase phase was transformed into the rutile phase, which resulted in an enhancement of the refractive index, i.e., an increase in the amount of the red shift.
Highlights
Photonic crystals are promising materials for applications in optoelectronics and photonics as well as in the field of optical sensing
Because polystyrene colloidal crystals are notable for their easy removal, an inverse opal scaffold structure with a high refractive index [20] can be prepared for rapid quantitative analysis of ethanol concentration
Ntitania is the refractive index of titania, nethanol is the refractive index of different ethanol concentrations, and f is the packing factor (=0.74) of the crystal structure, the results indicate that the structure is a well-ordered 3D face centered cubic order structure [10]
Summary
Photonic crystals are promising materials for applications in optoelectronics and photonics as well as in the field of optical sensing. To develop an effective and simple mean for detection of the ethanol concentration, we consider using the iridescent photonic sensors because the iridescent scales of the M. butterfly produce a different optical response when it was exposed to different chemical solvents. The photonic crystal effect has been exploited to create a chemical sensor, optical measurements have evidenced that the polymer composite structure presents a different optical response as a function of the solvent applied on the surface [11]. Several groups have obtained inverse opal structures by using colloidal crystals of polystyrene or silica microspheres as templates. Because polystyrene colloidal crystals are notable for their easy removal, an inverse opal scaffold structure with a high refractive index [20] can be prepared for rapid quantitative analysis of ethanol concentration. A polystyrene microsphere was chosen as the template, and TiO2 was chosen as the inverse opal structure material in this study
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