The Detection Of Uric Acid Concentration Based On Near Infrared Surface Plasmon Resonance Of Nanoparticles Enhancement

The surface plasmon resonance technology is widely used in biological engineering, drug development, food safety and environmental monitoring areas because of its high sensitivity, rapid detection in real time, the sample without tag. At present, the SPR biosensor mainly exist the following problems: Firstly, the sensitivity is limited, small molecules can’t be detected directly; Secondly, it is easy to be effected by the disturbance of environment, the refractive index sensitivity of SPR sensor decreases with the increasing temperature, the effects of environmental temperature must be taken into account in high-precision quantitative analysis; Thirdly, compare to the visible spectrum zone, the metal nano-materials have strong SPR absorption in near infrared and good transmission characteristics in optical fiber. The components of multiple samples can be analyzed in qualitative and quantitative at the same time. However, the SPR technology in near infrared is lack of deep study till now. In addition, SPR can be enhanced by metal nanoparticles, improve the sensitivity of the sensor greatly, the enhancement of metal nanoparticles has become an important direction in the SPR field. The main research works of this paper are as follow:1. Detection of uric acid concentration in angle modulation SPR. According to the effective medium theory and Fresnel multilayer membrane structure, we calculate and simulate the enhancement of silver nanoparticles on SPR. The simulation of average refractive index sensitivity of single silver film SPR and nanoparticles modified SPR is 97.921°/RIU and 102.81°/RIU respectively. The method to obtain silver nanoparticles with size at 30 to 50 nm is secondary reduction method, soak the silver plated glass side in silver nanoparticle sol to fixed a layer of silver nanoparticles as the enhanced SPR sensing chips by physical adsorption method, detect the uric acid solution with concentration ranged from 0 to 1.25mmol/L by the light source at wavelength of 854 nm, the average refractive index sensitivity of single silver film SPR and nanoparticles modified SPR is 88.537°/RIU and 101.19°/RIU respectively, The results show that there is enhancement on SPR by silver nanoparticles in angle modulation, but not obvious.2. Detection of uric acid concentration in wavelength modulation SPR. Calculate and simulate the enhancement of silver nanoparticles on SPR in wavelength modulation, obtain the change of resonance spectrum of acid solution with concentration ranged from 0 to 1.25mmol/L by the light source at wavelength of 350 to 2500 nm, the simulation of average refractive index sensitivity of single silver film SPR and nanoparticles modified SPR is 1576nm/RIU and 5921.8nm/RIU respectively. The simulation results show that there is a significant enhancement on SPR by silver nanoparticles in wavelength modulation.3. Temperature characteristic research of near infrared SPR sensor. We take air and water as samples, detect the change of resonance angle when temperature ranges from 14℃ to 39℃ at the step of 5℃. If the sample is air, the change of resonance angle is very small, beyond of the accuracy of measurement of 0.04° by experiment device. For water, that the trend of which the resonance angle decreases with the increasing temperature is very obvious, about 0.05°/℃, the full width half maximum of the SPR reflectance curve broadens with the increasing temperature, the sensitivity decreases.