Fabrication And Characterization Of Long-range Surface Plasmon Resonance Biosensors

The evanescent wave in a long-range surface plasmon resonance sensor (LRSPR)possesses stronger electromagnetic field strength, longer surface transportation distance,deeper penetration depth. Therefore, compared to conventional surface plasmon resonance sensor (cSPR), the LRSPR sensor shows a higher sensitivity and a larger detection area.Currently the material of the dielectric buffer layer is lack, and the preparation method is complicated. Therefore, it is highly desirable to develop a fast and simple method to prepare the dielectric buffer layer for the construction and application of LRSPR sensors.In this work, we use the plasma enhanced chemical vapor deposition (PECVD) method for the first time to deposite fluorocarbon film on SF11 glass substrates by using the 1H,1H,2H-perfluoro-1-decene (PFOE) as polymerization monomer. Then we construct the long-range surface plasmon resonance sensor by using this film as the dielectric buffer layer.By controlling the reaction conditions, such as gas discharge mode, duty cycle and plasma input power, we can obtain fluorocarbon films with different refractive indices. We can also achieve various thicknesses of ppPFOE films by controlling the deposition time. Atomic force microscopy (AFM) was used to characterize the surface morphology of the deposited films. Surface plasmon resonance (SPR) technique and optical waveguide mode spectroscopy (OWS) were used to determine the thickness and refractive index of fluorocarbon films. After optimizing the layer structure of the LRSPR sensor layer, the LRSPR sensor with the best performance was studied in solution of both ethylene glycol(EG) and lysozyme (Lyz).The results showed that the prepared fluorocarbon thin films' deposition rate is very stable when the PFOE monomer was deposited in the continuous wave discharge mode with an input power of 60 W. The ppPFOE thicknesses are proportional to the deposition time with a deposition rate of 65 nm/min. We found that the refractive index of the fluorocarbon film is about 1.3756 in air, which is very close to that of the water (n=1.333).By analyzing with the SPR and OWS, we found that the fluorocarbon film exhibits good adhesion onto both the gold film and the SF11 glass substrate without the use of any adhesive layer, and this film can be directly applied without any post-processing. The sensitivity of the LRSPR biosensor with the optimal layer structure is higher than that of the cSPR sensor, which can be improved by 4.2 times.