Multi-functional Fluorescent Sensing With Rhodamine B And The Sensing System Design

Rhodamine B(RhB)is a typical fluorescent organic dye.It has high coefficient of mole absorption,excellent light stability,wide emission wavelength range and high quantum efficiency.Moreover,the fluorescence of RhB is convenient for detecting in visible range,and it is biological histocompatible.Then the fluorescence sensing system of RhB can satisfy different physiological,natural environment test requirements.In this research,fluorescence of RhB or RhB/H610-resin composite were used for multi-functional sensing applications of temperature,stress and pH value without making any modification on the organic dye.Besides traditional fluorescent temperature sensing techniques such as fluorescence intensity technique,fluorescence intensity ratio(FIR)technique,several new sensing techniques with broadband fluorescence were developed in the research.The techniques were named barycenter technique,selfreferenced intensity ratio technique and integral intensity ratio technique,respectively.In the experiment,an RhB/H610-resin composite or aqueous solution of RhB were excited under a diode laser with a wavelength of 405 nm and used for the complete multi-functional sensing of temperature,stress and pH value.Accordingly,sensing system was built using these fluorescence characteristics of RhB as the sensing signals.The newly proposed barycenter shift of the emission band(?B),self-referenced intensity ratio(R)and integral intensity ratio(RI)were employed to characterize the change of the fluorescence band which depended on the environmental factors-temperature(?),stress(MPa)and pH value.Static characteristics of the fiber optic sensing system such as repeatability and hysteresis were analyzed.The experimental findings mainly include:(1)Sensing functions of temperature: ?B=620.89-1.08?+0.1?2 and R=0.82-0.01?(R=I(625nm)/I(615nm)).The repeatability of the barycenter technique was determined as 0.8%FS,and that of the self-referenced intensity ratio technique was 1.6%FS.(2)Sensing functions of stress: ?B=620.89-1.08?+0.1?2 and R=0.82-0.01?(R=I(625nm)/I(615nm)).The repeatability of the barycenter technique was determined as 2.8%FS,and that of the self-referenced intensity ratio technique was 2.1%FS.When the barycenter technique was employed,the maximum hysteresis of the RhB/H610-resin composite is 11.8%FS.(3)Sensing functions of pH value: ?B=836.36-75.71pH+5.85pH2,R=1.86-0.15pH(R=I(595nm)/I(585nm))and RI=0.17+0.04 pH.(4)Particularly,the sensing system was verified by applications in the real-time monitoring of microwave treatment and the determination of glycine concentration.Amongst the multiple sensing functions retrieved,the two novel techniques showed advantages such as improved precision and promoted sensitivity.The fluorescent sensing with RhB is a candidate for characterizing biological samples and microwave treatment.