Photonic Crystal Film Fluorescence Sensor For Efficient Detection Of Organic Vapors

Volatile organic compounds?VOCs?can enter into human body via skin,respiratory tract,and digestive tract,and has strong irritation to skin mucosa,respiratory mucosa and eye conjunctiva.That will damage human organs and has intense carcinogenesis,tetratogenesis and mutagenesis,which will seriously affect human health.Therefore,it is very important for human health and environment protectiuon to develop high efficient,fast,and real-time sensors for detecting VOCs.In this dissertation,photonic crystal?PC?film fluorescence sensors were prepared by infiltrating or modifying functional molecules to inverse opal photonic crystals?IOPC?.The slow photon effect of PC can enhance the fluorescence and improve the sensitivity of the fluorescence detection.The specific interaction between the functional molecules and the analytes can achieve the selective detection.The three-dimensional macroporous structure of IOPC is favorable for the diffusion of vapors and the adsorption onto the pore wall,which can improve the detection speed.Finally,the highly sensitive,selective and quick detection of organic vapors can be realized.The main contents are as follows:1.Tetrahydrofuran vapor-sensitive PC film fluorescence sensor was fabricated by infiltrating a tetraphenylethene polymer?TPEP?into the voids of SiO₂ IOPC,which was prepared from sacrificial template method.The as-prepared sensor emitted fluorescence at 464 nm.The fluorescence intensity can be significantly enhanced based on the slow photon effect of PC by selecting appropriate PC,which can improve the detection sensitivity.The fluorescence of the sensor quenched when exposed to tetrahydrofuran vapor.The reason is that TPEP,as one of “aggregation-induced emission” polymer molecules,shows nonemissive or faintly emissive in solutions but become strongly emissive when aggregated.When the sensor was placed in the atmosphere oftetrahydrofuran for 2 min,the fluorescenc quenching could be observed quickly because the interconnected macroporous structure and high specific surface area of IOPC is benificial to the quick diffusion of tetrahydrofuran vapor and condensation onto the pore wall.Herein TPEP was dissolved in tetrahydrofuran and the fluorescence quenched.The prepared sensor has a high sensitivity and the detection limit is 2 ppm.The tests in different vapors demonstrated that the sensor has good selectivity.When the sensor was exposed to air,tetrahydrofuran volatilized and TPEP changed to aggregated state from solution,and then the sensor's fluorescence recovered,which implied that the sensor can be reusable.Therefore,the TPEP-infiltrated PC sensor can be utilized for the tetrahydrofuran detection with high sensitivity,selectivity,quickness and reversibility.2.We fabricated a quickly responsive,highly sensitive,excellently selective and conveniently recyclable fluorescent film sensor for the detection of formaldehyde?FA?vapor,which is based on Fluoral-p infiltrated SiO₂ inverse opal photonic crystals?IOPC?.The as-prepared sensor combined the properties of the IOPC's interconnected macroporous structure,high surface area,the slow photo effect which can amplify the fluorescence,and the formation of fluorescent product generated from selective reaction between Fluoral-p and FA.Upon exposure to FA vapor for 20 s,the arisen fluorescence can be clearly observed and the intensity can be magnified remarkably.The fluorescence enhancement for FA detection on the optimized sensor can be up to 76.3-fold compared with that of the control sample.The sensor achieved a detection limit of 0.008 mg/m3 and had good selectivity for FA.Additionally,the sensor could be easily recycled by washing with ethanol,followed by infiltrating Fluoral-p again.Therefore,the designed Fluoral-p infiltrated IOPC can be utilized as a highly effective fluorescent sensor for detecting gaseous FA,which provides a promising strategy for improving response rate and detection sensitivity,and has enormous potential to the detection of other gases by choosing suitable IOPC and functional molecules.3.The 2,2':5',2''trithiophene?3T-CHO?modified SiO₂ IOPC fluorescence sensor was fabricated to be used for the detection of formaldehyde vapor.The 3T-CHO modified SiO₂ IOPC was irradiated by UV light and then was exposed to theenvironment of formaldehyde vapor.After 20 s,the fluorescence at 458 nm could be observed and the fluorescence intensity increased along with increasing the exposure time.The fluorescence intensity achieved to the maximum at 1800 s.The fluorescence was derived from a physical complex of FA molecules and the photo-oxidative product of3T-CHO under the irradiation of UV light.The results demonstrated that the as-prepared PC film irradiated by UV light can be used to quickly detect FA.The macroporous structure of the preapared IOPC is favorable for the diffusion of FA vapor and the IOPC's high specific surface area will provide more reaction sites.In addition,the slow photon effect of PC can enhance the fluorescence.All the above-mentioned is beneficial to highly efficient detection of FA.The control experiments showed that the response is selective.When the sensor was exposed to air,FA volatilized and the fluorescence quenched,which demonstrated that the film can be used repeatedly.Therefore,the constructed 3T-CHO modified IOPC can be employed as a fluorescence sensing film for detecting FA vapor,which provides a new way for developing gas sensors based on photonic crystals.