Plasmonic Ag/ZnO Nanoscale Villi in Microstructure Fibers for Sensitive and Reusable Surface-Enhanced Raman Scattering Sensing

Abstract

Microstructure fibers, integrating microfluidic channels and light guidance in one fiber, enable three-dimensional surface-enhanced Raman scattering (SERS) detection for large signal accumulation. However, the available fiber SERS probes are complicated to prepare and they are not reusable. In addition, light interacts with analytes in a form of an evanescent field, which is very weak. In this paper, we developed a SERS platform based on suspended-core photonic crystal fibers decorated with Ag/ZnO nanocomposites on the inner surface for direct, ultrasensitive, and reusable analyte detection. The unique configuration not only transfers a corelocalized field to the liquid interface to greatly enhance the light−analyte interaction but also facilitates charge transfer to further improve the SERS detection sensitivity and degradation efficiency. The detection limit of crystal violet solution is 10 −13 M, and the enhancement factor reaches 10 11 . The relative standard deviation is as low as 5.4%, ensuring the reproducibility of SERS detection. The probe has good photocatalytic performance and can degrade molecules under ultraviolet-light illumination within 20 min. This ultrasensitive and reusable SERS probe shows great application potential in rapid and in situ liquid detection.

Ag/ZnO Nanocomposite-Decorated Capillary for Rapid Trace Gas Identification Based on Surface-Enhanced Raman Scattering under Ambient Conditions

“…The peaks’ intensity detected with an AgNP-decorated capillary is about 7.4 times lower than that detected with an Ag/ZnO nanocomposite-decorated capillary, as shown in Figure d. As a metal oxide semiconductor, ZnO has a Fermi level higher than that of Ag, which provides chemical enhancement by the improvement of charge-transfer efficiency . Furthermore, the densely distributed and elongated Ag/ZnO nanocomposites exhibit remarkable superhydrophilicity and resemble numerous villi structures.…”

“…The density and size of AgNPs were controlled by the concentration ratio of silver ammonia to glucose and the reaction time. 26 As shown in Figure 1b−d, ZnO nanorods are uniformly and vertically arranged along the inner wall of the capillary, with a length of approximately 1 μm and an average diameter of 200 nm. AgNPs, with a diameter of approximately 80 nm, are distributed on the top and sides of the ZnO nanorods.…”

“…After that, Ag nanoparticles (AgNPs) were in situ-synthesized on the surface of ZnO nanorods by using the silver mirror reaction. The density and size of AgNPs were controlled by the concentration ratio of silver ammonia to glucose and the reaction time . As shown in Figure b–d, ZnO nanorods are uniformly and vertically arranged along the inner wall of the capillary, with a length of approximately 1 μm and an average diameter of 200 nm.…”

“…As a metal oxide semiconductor, ZnO has a Fermi level higher than that of Ag, which provides chemical enhancement by the improvement of charge-transfer efficiency. 26 Furthermore, the densely distributed and elongated Ag/ZnO nanocomposites exhibit remarkable superhydrophilicity and resemble numerous villi structures. These unique characteristics promote efficient liquid infiltration (inset in Figure 2) and substantially augment the specific surface area, thereby significantly enhancing the efficiency of interaction between light and analytes.…”

Direct and Rapid Sensing of Per- and Polyfluoroalkyl Substances Using SERS-Active Optical Fibers

“…It is based on microstructured optical fibers (MOFs) decorated with β-cyclodextrin (β-CD)-functionalized silver nanoparticles (AgNPs). AgNPs can provide a strong electromagnetic enhancement via localized surface plasmon resonance, with surface roughness and nanogaps contributing as hot spots. , β-CD contains seven glucose subunits arranged in an end-to-end fashion, which are configured into a conical cavity with an aptitude for forming inclusion complexes. The outer surface of this structure presents seven primary alcohol groups, imparting a degree of hydrophilicity, while the inner core comprises 14 secondary alcohol groups, rendering it hydrophobic in nature.…”