Abstract
In this study, we integrate plasmonic metal nanomaterials with a piezoelectric polyvinylidene fluoride (PVDF) polymer and lithium niobate (LiNbO3) based composite to form an all-solid-state flexible self-energized sensor. We demonstrate that following the application of a load, the film enhances the surface-enhanced Raman spectroscopy (SERS) signal of an analyte molecule up to 14 times. The piezoelectric β-phase of PVDF in the film is optimized through the introduction of multi-walled carbon nanotubes and post-fabrication UV irradiation annealing. Additionally, the SERS signal enhancement can be further increased by the application of in situ UV light irradiation of the sample, resulting in the generation of photoexcited electrons from LiNbO3 microparticles introduced into the composite. Both the application of a mechanical displacement and the UV light-induced charge generation result in an improved charge transfer between the film and an analyte molecule. The piezoelectric PVDF/LiNbO3 film has been shown to be a suitable SERS platform for the detection of important biological molecules, demonstrating the potential of the substrate for fast on-site detection applications.
Highlights
The design and fabrication of chemical sensors with high sensitivity and selectivity have attracted considerable attention in fields such as environmental monitoring, medical diagnostics, and forensic analysis[1–16] Surface-Enhanced Raman Spectroscopy (SERS) is a powerful vibrational spectroscopic technique widely used in analytical chemistry that enables precise molecular identification.[17]
We propose that the combined effects of localized surface plasmon resonance excitation in the metal, stress-induced charge generation in polyvinylidene fluoride (PVDF), as well superbandgap excitation in LiNbO3 due to UV light irradiation result in a significant boost of the SERS signal
We propose that the role of LiNbO3 in enhancing the SERS signal intensities is through the application of superbandgap UV irradiation through photo-induced enhanced Raman spectroscopy (PIERS).[22]
Summary
The design and fabrication of chemical sensors with high sensitivity and selectivity have attracted considerable attention in fields such as environmental monitoring, medical diagnostics, and forensic analysis[1–16] Surface-Enhanced Raman Spectroscopy (SERS) is a powerful vibrational spectroscopic technique widely used in analytical chemistry that enables precise molecular identification.[17]. The electromagnetic enhancement contribution results from the amplification of the local electromagnetic fields near nanostructured metals due to the excitation of localized surface plasmon resonances. The chemical enhancement mechanism arises from charge transfer between the SERS substrate and the analyte molecule. We aim to exploit both mechanisms simultaneously by using plasmon-active metallic nanostructures combined with a piezoelectric polyvinylidene fluoride (PVDF) polymer facilitating charge transfer, leading to better SERS efficiency of the substrate. Electric-field up-regulated surface-enhanced Raman spectroscopy (E-SERS) has been shown to effectively increase Raman signal intensities through combining triboelectric or piezoelectric materials with plasmonic nanomaterials.[8,20,21] For instance, it has been demonstrated that the SERS signal from a probe molecule can be enhanced up to threefold by depositing it on a triboelectrically active material combined with Au–Ag nanostructures.[20]. The E-SERS mechanism enables an increase in Raman signals up to ten times for a variety of analyte molecules
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