Preparation And Study On The SERS Probe And LSPR Optical Fiber Sensor

Noble metal nanoparticles have LSPR and SERS character, and the optical fiber is low cost, small bulk and can detect analytes real-time. The LSPR optical fiber sensor and SERS probe optical fiber sensor were prepared by combining the optical fiber technology and the character of noble metal nanoparticles. The two optical fiber sensors detected bio-immunity molecule and environmental pH respectively.1. The LSPR sensor: The Au nanoparticle (Np) assembly film as the sensing layer was built on the polyelectrolyte (PE) multilayer (PDDA/PSS/PAH) modified sidewall of unclad optical fiber. The film has good mono-dispersion, outstanding reproducibility, high stability and capacity. Thus, the sensor has outstanding reproducibility and stability, and it has higher sensitivity to the environmental refractive index. The sensitivities are 9.46TU/RIU for 48nm Au and 5.94TU/RIU for 23nm Au.2. The rabbit IgG modified optical fiber LSPR sensor was employed to detect the goat anti-rabbit IgG. Different concentrations of goat anti-rabbit IgG (in PBS solution) were pumped into the liquid cell. The 23nm Au assembled optical fiber LSPR sensor was used here due to its shorter preparing time. The entire dynamics process of goat anti-rabbit IgG adsorption is collected. A working curve based on an exponential equation is obtained. The lowest detection concentration of goat anti-rabbit IgG is supposed to be 11.1ng/mL. The sensor has no response except the interfered concentration is thousand times than the analytes.3. The optical fiber SERS probe is prepared by dripping the Ag colloid on the end of the optical fiber. The end of the optical fiber is dipped in the 4MBA aqueous solution. The 4MBA molecule will adsorb on the surface of the Ag nanoparticles. The group of the 4MBA molecule will alter in the different pH environment, so the certain peak in the SERS spectrum will alter together. The most prominent feature is the ring-breathing mode at 1590cm-1. The stretching mode at 1420cm-1 (νs(coo-)) is sensitive to the pH. The standard curve of the sensor can be made by the plot of the pH as function of the peak intensity at 1420cm-1. The sensitive range to the pH of the sensor is 4-11. It can be found that the rough Ag surfaces and alkaline pH (>10) can promote partial decarboxylation of 4MBA molecule.