The Study On The MOFs Based One-Dimensional Photonic Crystal Volatile Organic Compounds Sensor And Its Performance

Photonic crystals are a new type of metamaterials with media designed in highly ordered in the physical structure,which are developed in recent years.Photonic crystals can mold the flow of light and improve the interaction between light and medium,for what they have broad application prospects in many fields.In the sensing field,with the specific responsive sensing medium placed in the photonic crystal,the photonic crystal sensor can offer the certain optical signal for various external signal sources(temperature,pressure,gas,etc.)due to the tunable photonic band gap.From the perspective of fabrication,based-on-film-optics one dimensional photonic crystals are the most widely studied because of their simple fabrication and mature technology.Metal organic frameworks(MOFs)materials are widely used in gas adsorption,separation,sensing and other fields with the high level in specific surface area,porosity,and adjustability of pore size and functions.When MOFs are implanted in photonic crystals as the active sensing component,due to the porosity and rich host-guest interaction,the photonic crystals can realize recognizable optical signals displayed by obvious band gap shift upon the adsorption of analysts.It has a wide significance in the field of directional identification of toxic gas and the concentration calibration of specific gas concentration.Therefore,this paper will focus on the research of MOF based one-dimensional photonic crystal gas sensor.The research contents of this paper are as follows:1.The theoretical model of one-dimensional photonic crystal was constructed,and the calculation of reflectivity and photonic band gap of one-dimensional photonic crystal was theoretically performed using the transfer matrix method.The effects of various structural parameters(incident angle,period number,refractive index,layer thickness)on the band gap structure and optical properties of one-dimensional photonic crystals were investigated by MATLAB,which provided theoretical guidance for the preparation of MOF based one-dimensional photonic crystals in subsequent experiments.2.A typical MOF based one-dimensional photonic crystal sensor(MIL-101-NH₂(Cr)/Ti O₂)_n)with distinct structural color was prepared by using the spinning coating method.The reliability and validity of the sensor are verified by using the above theoretical simulation.In terms of sensor performance,the MIL-101-NH₂(Cr)based one-dimensional photonic crystal sensor has the maximum optical response signal to methanal with a peak shift of 43 nm,which can effectively distinguish it from other analytic gases.In the methanal concentration test,the optical response showed a good linear relationship with methanal concentration(R²=0.99362).The corresponding concentration sensitivity was 0.02 nm/ppm and the minimum detectable methanal concentration was 5 ppm in theory.In addition,the sensor has a response time about 500 ms and a recovery time about20 seconds.In addition,this MOF-based sensor has reliable repeatability and stability in long-term storage and high temperature environments,making it highly competitive in the field of gas sensing.3.In order to improve the performance of MOF-based one dimensional photonic crystal sensor,the study on the doping the second metal in MOF was performed.Pure ZIF-8(Zn)and bimetallic ZIF-8(Zn@Co)were selected as the sensing layer.Considering the experimental situation and the theoretical optimization,the typical four-period one-dimensional photonic crystal sensors were prepared respectively.Compared with the pure ZIF-8(Zn)based sensor in the control group,the sensor based on bimetallic ZIF-8(Zn@Co)has higher optical response and better sensing performance for chlorobenzene(MCB),and has higher selectivity.This shows the possibility of enhancing the performance of MOF-based sensors by doping the second metal.In addition,the bimetallic ZIF-8(Zn@Co)-based one dimensional photonic crystal sensor has high performance in the low concentration range of chlorobenzene(MCB)(<100 ppm)showed high linearity and sensitivity(0.05 nm/ppm),with a response time about 600 ms and a recovery time about 9.5 s at 600 ppm MCB.Moreover,the bimetallic MOF based one dimensional photonic crystal sensor shows good reversibility and stability after being stored at 200?,ultrasound for 45 min,and normal temperature for 30 days.This also shows the potential application prospect of the bimetallic MOF based one-dimensional photonic crystal sensor.