Research On Optical Fiber Sensor For Accurate Measurement Of Cu²⁺ Concentration In Liquid Environment

As an important metal element,copper plays the special role in the fields of electric power,chemical industry,energy and national defense.But in recent years,the transitional development of copper metal has caused the pollution range and extent of copper(?)rapidly increase in liquid environment,and then it has a serious impact on ecological environment,human health and safety,thus,it is a necessary and meaningful work to detect and analyze the copper(?)concentration in liquid environment.Optical fiber sensing technology has been widely applied to physical,chemical,biological and other detection fields because its high sensitivity,fast response,and immunity to electromagnetic interference.In this paper,a plastic optical fiber(POF)sensor for accurate measurement of copper(?)in liquid environment is developed.In this study,to obtain a high-sensitivity copper(?)optical fiber sensor,the plastic optical fiber refractive index sensor is fabricated by chloroform wet etching technique firstly,on this basis,the high-sensitivity plastic optical fiber refractive index sensor is fabricated by acetic acid wet etching technique,then the plastic optical fiber copper(?)sensor is fabricated by the high-sensitivity plastic optical fiber refractive index sensor coupling graphene oxide(GO),which can accurate measurement copper(?)in liquid environment.The main results we obtained as follows:(1)Chloroform wet etching technique for fabrication of plastic optical fiber(POF)refractive index sensor.Firstly,the etchant is prepared by employing the chloroform and anhydrous ethanol.Secondly,we investigated the effects of the concentration and temperature of the etchant on the etching rate and surface morphology of the POF sensors.Thirdly,we examined the transmission spectrum of the etched POF sensors,and checked the sensitivity of the etched POF sensors by using the glucose solutions.The experimental results show that the POF sensors,which are fabricated using the etchant with a concentration of 70%under temperature of 25 ?,exhibits smooth and clean surface morphology,good light transmission,and a sensitivity of 3.8[(RIU)(g/L)]-1 in the glucose solutions.(2)Acetic acid wet etching technique for fabrication of high-sensitivity plastic optical fiber(POF)refractive index sensor.Firstly,the etchant is prepared by employing acetic acid and distilled water.Secondly,we investigated the effects of the concentration and temperature of the etchant on the etching rate and surface morphology of the POF sensors.Thirdly,the high-sensitivity POF sensors can be obtained by optimizing the etching conditions.The experimental results show that the POF sensors,which are fabricated using the etchant with a concentration of 80%under temperature of 25 ? and an ultrasonic power of 130 W,exhibits a high-quality surface morphology(smoother,cleaner),excellent light transmission,and a sensitivity of 9.1[(RIU)(g/L)]-1 in the glucose solutions.(3)Plastic optical fiber copper(?)sensor based on graphene oxide.Firstly,The graphene oxide(GO)and(3-aminopropyl)trimethoxysilane(APS)were immobilized on the sensing surface of the plastic optical fiber using layer-by-layer self-assembly method,and the GO/APS used as copper(?)sensitive film.Secondly,we investigated the surface morphology of the sensor by optical microscope and electron microscope.Thirdly,we evaluated the performance of the sensor in terms of light transmission,sensitivity,response time and detection range.Furthermore,we also studied the method of the sensor to enhance stability and sensitivity.The experimental results show that the good sensitivity of the proposed POF copper(?)sensor with GO,which can accurate measurement of 0.1?100 mg/L copper(?)in liquid environment,the sensor shows the low detection of 0.05 mg/L and the sensitivity of-0.000625[(RIU)(mg/L)]-1,60-second response times,and the maximum error of 4.7%in actual sample detection.