Optical fiber localized surface plasmon resonance sensor based on dense gold trisoctahedra

Abstract

Tuning the plasmonic coupling of noble metal nanoparticles is important for improving the sensitivity and performance of localized surface plasmon resonance (LSPR) sensing. Combining the excellent LSPR performance of gold trisoctahedra (Au TOH) with unique tips, a novel optical fiber LSPR sensor was prepared by uniformly and densely assembling Au TOH on optical fiber using liquid-liquid interface self-assembly method. This method allows for the non-destructive transfer of pre-prepared dense Au TOH monolayer film onto optical fiber in a simple and time-saving manner. The LSPR characteristics of Au TOH on optical fiber with different spacing were simulated by the finite difference time domain (FDTD). Expectedly, the decreasing of the Au TOH spacing can enhance the local electric field strength, and leads to LSPR peak broadening, resonance wavelength redshift, and improving the sensing sensitivity. Meanwhile, the nanoparticle gap of the practically prepared optical fiber LSPR sensor was approximately 5 nm, and such narrow gap ensures the sensitivity of sensor based on the theoretical simulation results. Furthermore, the detection of sucrose solutions with different concentrations was successfully achieved based on the sensor combined with microfluidic technology, with the highest sensitivity up to 200.67 nm/RIU. The remarkable performance and simple preparation strategy make this optical fiber LSPR sensor own excellent potentials for highly sensitive and cost-effective biomedical sensing applications.