Design Of Fiber Optic Sensor Based On Modified Graphene And Its Application In Biological Detection

Food safety has been a hot controversy for quite a long time,thus a global problem has come out.With the quality of life improving and the variety of food increasing,the potential danger of food appears.What’s more,nowadays the health of people is negatively affected by the over-absorb of sugar and food-borne bacteria,even one’s life safety can be threatened.As a consequence,to develop a examining technique which is quick and accurate has been a necessary event.In recent years,various sensors have been continuously researched,especially fiber optic sensors which are widely used and developed,and biosensors provide a new detection method for detecting sugars and food-borne bacteria.Biosensors use biological matter as an identifier to convert biological reactions into optical signals for us to detect.as a result,food safety problem can be solved using the optical fiber biosensor,different identifiers can use different materials to react,thereby changing the effective refractive index of the fiber and generating an optical path difference,thereby detecting relevant information of the object to be tested.The main research contents of this paper are as follows:(1)Using the Furukawa S178 C fiber fusion splicer,by studying various welding methods and comparing them,the coarse cone welding of photonic crystal and ordinary single-mode fiber was finally selected to form Mach-Zehnder interference,and the structure of the sensor was initially determined.(2)Graphene grown by the CVD method is transferred to the surface of the photonic crystal fiber by a graphene transfer method to prepare a sensitive element based on a graphene-coated tapered photonic crystal fiber.Through the physical adsorption principle of graphene and sucrose solution,it is used for the detection of low concentration sucrose solution.(3)A graphene-based composite material was prepared.The coupling reaction of maltose and 1-aminoanthracene was carried out,and then graphene was added for stirring.Finally,the concanavalin A was added for mixing reaction to obtain a composite material.(4)The entire test system was designed by itself,and the composite material was formed on the surface of the photonic crystal fiber by dip coating method,and a modified graphene-based fiber biosensor was used to detect Escherichia coli with cellmembrane as lipopolysaccharide.(5)The Escherichia coli solution was cultured,and the concentration of the bacterial liquid was determined by scribing treatment,and Escherichia coli solutions of different concentrations were obtained by using a coating separation method.The prepared different concentrations of E.coli solution were added into the fiber sensing area to test the sensitivity performance,and the sensitivity,stability,response time and detection limit of the sensor were obtained according to the test results.