A SERS fiber probe fabricated by layer-by-layer assembly of silver sphere nanoparticles and nanorods with a greatly enhanced sensitivity for remote sensing.

Remote sensing remains a challenge due to its demand for high sensitivity, convenient sampling and rapid response time. Surface enhanced Raman scattering (SERS) spectroscopy is a powerful analytical method for the detection of various samples. Here, aiming at increasing the sensitivity, a novel strategy for the preparation of a SERS probe is demonstrated by using hollow optical fiber tips decorated by layer-by-layer assembly of two kinds of nanoparticles. Specifically, Au@Ag core-shell nanorods and Ag nanospheres with opposite surface charge were assembled layer-by-layer on the tip of hollow optical fibers through electrostatic interaction. Then, much more hotspots are generated due to the close gap between the nanorods and nanospheres in the resultant 3D structure, which can lead to a dramatically enhanced SERS activity of the probe compared with that fabricated by pure silver sphere nanoparticles or nanorods. On the other hand, taking the advantages of the vibration spectroscopic fingerprints property of SERS spectra and the long-distance communication capacity of optical fibers, the remote online detection of biological species including proteins, funguses and cells can be easily achieved within a few minutes. Therefore, such a novel kind of optical fiber-SERS sensor holds great potential for the rapid detection of a wide range of samples due to its superiority of simplicity and high sensitivity.