Study On Functional Microfiber Sensing Technology For Detecting Dyes And Mercury Ions

The rapid development of industry has caused serious pollution and destruction of water resources.Rapid and accurate detection of substance content in water resources is of positive significance to environmental protection of water resources.Microfiber sensor not only integrates the advantages of optical fiber communication such as strong anti-interference ability,low loss and fast transmission,but also shows a high sensitivity response to changes in the external environment with the characteristics of strong evanescent field.In this paper,the detecting alizarin red S dye and metal mercury ion(Hg²⁺),which are the common substances in water pollution,are taken as examples to design and study two kinds of functional microfiber sensors.These proposed sensors provide a broader idea and platform for the development of optical detection technology,and are expected to promote the construction of a distributed,multi-parameter internet of things communication platform.A tapered microfiber sensor based on multi-walled carbon nanotubes（MWCNTs）for detecting the concentration of alizarin red S dye is proposed and verified through experiments.MWCNTs fixed on the surface of optical fiber can adsorb the alizarin red S dye molecule due to its porous structure.The surface refractive index（RI）change caused by MWCNTs coated with the fiber surface adsorbing of alizarin red S dye can be captured by optical microfiber,which is macroscopically converted into wavelength drift in the interference spectrum.The sensor has a high RI sensitivity of 1942.25nm/RIU and a low temperature cross sensitivity of-0.03nm/℃.Experimental results show that the sensor provides rapid detection of alizalizin alizarin red S dye in the concentration range of 0-1000mg/L,and the sensitivity is 0.412nm/（mg/L）in the low concentration range of 0-25mg/L.The sensor has great potential in the field of environmental security protection.The monitoring of heavy metal ions content has positive significance for water resources quality monitoring and environmental protection.Herein,a tapered microfiber sensor functionalized polydopamine/4-mercaptopyridine（PDA/4-MPY）film for detection of trace Hg²⁺concentration in water is proposed and demonstrated.The microfiber device has excellent sensing performance including a refractive index（RI）sensitivity response of1146nm/RIU and a low-cross temperature response of-0.03nm/℃.Hg²⁺heavy metal ion is captured by the surface functional film to affect the RI of the microfiber surface,which leads to the wavelength shift of the interference spectrum.Experimental results demonstrate that the sensor has an obvious regular response to metal Hg²⁺ions in the range of 0-100n M having the sensitivity reaches 1.015nm/n M in the low concentration range of 0-10n M with a high reliability（R²=0.99）.Meanwhile,the sensor has good specific recognition ability for metal Hg²⁺ions.The sensor has broad application prospects in heavy metal ion content monitoring and water resources quality monitoring.