High sensitivity D-shaped fiber decorated with self-assembly Ag nanoparticles for Raman enhancement via collecting backward and vertical direction scattering signals

To address the non-uniformity of hotspots and large background noise signals in the Raman spectrum of traditional surface-enhanced Raman scattering (SERS) probes, this paper presents a high-sensitivity and high-uniformity D-shaped fiber (DSF) SERS probe. The probe is prepared by transferring monolayer silver nanoparticles (AgNPs) with different particle sizes onto the DSF using a liquid-liquid interface method. The electromagnetic distribution on the DSF SERS probe is analyzed with FDTD (finite difference time domain) Solutions simulation software, and the corresponding theoretical enhancement factors are calculated. The DSF SERS probe decorated by AgNPs with a diameter of 100 nm exhibits the largest electric field value among our prepared samples. The experiments are conducted to compare two collection methods with backward and vertical directions The results show that vertical collection offers better Raman enhancement due to the suppression of background noise of the fiber, with a limit of detection (LOD) of 10 −11 mol/L for Rhodamine 6G (R6G). The experimental analytical enhancement factor (AEF) at 611 cm −1 is 1.7 × 10 9 . Furthermore, the multi-molecular detection performance of the DSF SERS probe is experimentally studied and realized successfully.