Abstract
Recently, surface enhanced Raman spectroscopy (SERS)-active photonic crystal fiber (PCFs) probes have gained great interest for biosensing applications due to the tremendous advantages it has over the conventional planar substrate based SERS measurements, with improvements on the detection sensitivity and reliability in measurements. So far, two main approaches were employed to get the analyte molecule in the vicinity of nanoparticles (NPs) inside PCFs in order to achieve the SERS effect. In the first case, analyte and NPs are pre-mixed and injected inside the holes of the PCF prior to the measurement. In the second approach, controlled anchoring of the NPs inside the inner walls of the PCF was achieved prior to the incorporation of the analyte. Although many studies have been conducted using one configuration or the other, no clear trend is emerging on which one would be the best suited for optimizing the biosensing properties offered by SERS active-PCF. In this paper, we investigate the performances of both configurations along with their interplays with the core size of the PCF probe. We have fabricated several samples of a standard PCF design with different core sizes, and SERS measurements of a standard Raman-active molecule are realized in the same conditions for enabling direct comparisons of the SERS intensity and measurement reliabilities between each configuration, yielding clear directions on the optimization of the SERS-active PCF probe. We envision that this study will pave the way for next-generation clinical biosensors for body fluid analysis, as it exhibits high sensitivity and excellent reliability.
Highlights
Surface enhanced Raman spectroscopy (SERS) is an analytical technique based on the inelastic scattering of light that allows the identification of molecules thanks to their clear vibrational fingerprint
A thorough rinsing with deionized water removed the unbound Au NPs and the fibers were dried. This will result in the formation of Au NPs monolayer inside the fiber. 1 mM ATP solution was pumped inside the SuC-photonic crystal fibers (PCFs) for ten minutes in order to bind to the anchored Au NPs
SERS active SuC-PCFs in both configurations exhibit a better reproducibility than conventional planar substrates, anchoring of Au NPs inside SuC-PCF leads to an excellent reproducibility (∼ 1%) and repeatability (< 15%)
Summary
Surface enhanced Raman spectroscopy (SERS) is an analytical technique based on the inelastic scattering of light that allows the identification of molecules thanks to their clear vibrational fingerprint. The smaller the core is, the more evanescent light will overlap in the holes and interact with NPs and the analyte leading to higher SERS-sensitivity of the PCF probe [33] This configuration may yield stronger absorption of the light by the NPs leading to shorter effective length of interaction along the PCF that reduces its benefits for improving the reliability of SERS measurements. Despite the numerous works showing the interests of PCF based SERS sensing, there is no clear direction on which configuration (injected/anchored) is more suitable to benefit from an efficient PCF SERS-probe design that optimizes the sensitivity, reliability offered by long length of interactions and reliable coupling efficiency with the Raman spectrometer. The impact of the core size on the PCF SERS-probe performances is investigated
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