Surface-Enhanced Raman Scattering Performance of Macroporous Grapefruit-Type Microstructured Fiber Optic Probes

With the development of optical fiber preparation technology and nanomaterial preparation technology, fiber probes have become a new type of surface-enhanced Raman scattering (SERS) substrate; by preparing different structures on common single mode fiber or multimode fiber and modifying the corresponding nanomaterials can obtain a variety of types of optical fiber surface-enhanced Raman scattering probes, and achieve better detection results. But the structure of the fiber itself has limited it, common fiber can only use the end face or measurement surface to provide Raman detection "hot spot" area, limiting its SERS performance to further improve. In this paper, a surface-enhanced Raman scattering (SERS) probe for a macroporous grapefruit-type microstructured fibre (MSF) is prepared, in which the macroporous grapefruit-type MSF SERS probe structure is fabricated by fusing a section of stepped multimode fiber to a grapefruit-type microstructured fibre. The SERS performance of the home-made silver nanosol substrates and the macroporous grapefruit-type MSF SERS probes are examined separately. MSF SERS probes loaded with silver nanoparticles are prepared by the sol-gel self-assembly method, and different fibre-optic SERS probes are prepared by controlling the self-assembly time (Ag/MSF-x, where x is the self-assembly time, 15,30,45,60 min, respectively). The solution detection method was used to detect 10(-3) mol center dot L-1 methylene blue (MB) probe molecule with Ag/MSF-x probe, and the Ag/MSF-45 probe was screened by comparing the enhancement effect under the same conditions. In order to further detect the SERS performance of the Ag/MSF-45 probe, MB solutions with different concentrations are prepared, and the nano silver soluble substrates and Ag/MSF-45 probe are used to detect them. The experimental results showed that MB's limit of detection (LOD) was 10(-6) mol center dot L-1 for the nano-soluble substrate and 10(-7) mol center dot L-1 for the Ag/MSF-45 probe. The reproducibility of the Raman signal shows that the RSD values for the nanosilver soluble substrates and the Ag/MSF-45 probe are within a reasonable range for each characteristic peak. A log-transformed fit of the Raman intensity and concentration of the nano silver soluble substrates and the Ag/MSF-45 probe detecting MB at a Raman shift of 1 619 cm(-1), with a good R-2 of 0.916 28 for the nanosol substrate and 0.988 48 for the Ag/MSF-45 probe. The reproducibility results for both the nanosilver soluble substrates and the Ag/MSF-45 probe show that their RSD values were within a reasonable range for each of the characteristic peaks, but the Ag/MSF-45 probe has a smaller RSD value for each of the characteristic peaks than the nanosilver soluble substrates, with a maximum of 13.89%. The enhancement factor (AEF) of the Ag/MSF-45 probe is calculateed using 10-6 mol center dot L-1 MB, and the AEF of the Ag/MSF-45 probe is reached 6.09 x 10(6), showing a good enhancement effect. Therefore, based on the unique air pore structure of the large hole grapefruit-type MSF SERS probe, it has high sensitivity and good reproducibility, and its SERS performance is better than the nano silver soluble substrates, and has a wide range of applications in agriculture, chemical analysis, bioassay and the detection of large molecules.