Detection Technology Of Environmental Quality Parameters Based On Nb₂CT_X Composite Fiber

With the development of economy and society,environmental quality issues have increasingly attracted the attention of people.Water quality and environmental humidity,as important environmental quality parameters,profoundly affect the industrial and agricultural production and people’s living.Therefore,there are urgent requires to develop the efficient and convenient detection technology for the detection of water quality and environmental humidity.Fiber optic sensing technology is a feasible strategy for realizing effective detection of environmental quality by virtue of its environmental friendliness and no secondary pollution,sustainable development,high sensitivity,excellent tolerance to harsh environments,and remote sensing capacity.For the detection of water quality and environmental humidity,high-performance fiber optic sensors based on Nb₂CT_X composite microfiber,Tilted fiber Bragg grating（TFBG）,and microfiber coupler are achieved in this paper.By analyzing the response characteristics of the sensors to the concentration of water pollutants and the level of environmental humidity,high-sensitivity detection of water pollution and environmental humidity have been achieved,which is expected to provide new ideas for the development of environmental quality detection technology.The main research contents of this paper are as follows:1.The fabrication methods and sensing mechanisms of the microfiber are summarized,and the sensor based on Nb₂CT_X composite microfiber for biochemical oxygen demand（BOD）detection is investigated.The sensitivity enhancement mechanism of the excellent physical and chemical properties of Nb₂CT_X for BOD detection is analyzed.Experimental results show that the sensitivity of the sensor is34.98 nm/mg/mL,which is more than 2 times higher than the bare fiber sensor,and the sensor can realize the temperature compensation.The sensor based on Nb₂CT_Xcomposite microfiber for environment humidity detection is investigated.The humidity sensitive properties of Nb₂CT_X are analyzed.Experimental results show that the sensor has a sensitivity of-86 pm/%RH in the range of 18.5%-72.4%RH;and a high-sensitivity of 585 pm/%RH in the range of 72.4%-95.4%RH.2.The sensing mechanisms of TFBG are summarized,and the sensor based on Nb₂CT_X composite TFBG for environment humidity detection is investigated.The response characteristics of TFBG higher-order cladding modes to environment humidity are analyzed.Experimental results show that the sensor achieves a wavelength sensitivity of 0.010 nm/%RH and a transmission intensity sensitivity of-0.031 dB/%RH in the humidity range of 83.1%-95.6%RH.The sensor based on Nb₂CT_X composite TFBG for streptomycin sulfate humidity detection is investigated.Experimental results show that the sensor achieves a sensitivity of 253.8 pm/mg/mL,which is more than twice that of a bare sensor.3.The basic theory of the photothermal effect,the fabrication methods and sensing mechanisms of the microfiber coupler are summarized,the microfiber coupler sensor based on the photothermal effect of streptomycin sulfate molecule is investigated.The performance enhancement mechanisms of Nb₂CT_X composite microfiber coupler and photothermal effect of streptomycin sulfate molecules are analyzed.Experimental results show that the sensitivity of the sensor to detect streptomycin sulfate is 23.76 nm/mg/mL,and the detection limit is 0.00084 mg/mL.