Abstract
.We report a fiber-optic plasmonic probe with nanogap-rich gold nanoislands for on-site surface-enhanced Raman spectroscopy (SERS). The plasmonic probe features nanogap-rich Au nanoislands on the top surface of a single multimode fiber. Au nanoislands were monolithically fabricated using repeated solid-state dewetting of thermally evaporated Au thin film. The plasmonic probe shows in SERS enhancement factor and 100 nM in limit-of-detection for crystal violet under both the excitation of laser light and the collection of SERS signals through the optical fiber. The fiber-through measurement also demonstrates the label-free SERS detection of folic acid at micromolar level. The plasmonic probe can provide a tool for on-site and in vivo SERS applications.
Highlights
In vivo molecular biosensing of disease-related biomarkers enables early diagnosis of diseases diseases,[1] intraoperative guidance for cancerous tissue removal,[2] and monitoring biomarkers of chronic diseases, such as diabetes[3] and atherosclerosis.[4]
SERS signals on the fiber-top surface radiatively scatter in all directions and an MMF is highly suitable for high photon collection, compared to a single-mode fiber (SMF) with low numerical aperture (NA).[17]
The percentage of total scattered light collected on the top surface of both SMF and MMF was calculated for the maximum collection efficiency of SERS signals.[17]
Summary
In vivo molecular biosensing of disease-related biomarkers enables early diagnosis of diseases diseases,[1] intraoperative guidance for cancerous tissue removal,[2] and monitoring biomarkers of chronic diseases, such as diabetes[3] and atherosclerosis.[4]. The substantial enhancement of both an excitation light and Raman scattering of small molecules near electromagnetic hotspots of plasmonic nanostructures results in extraordinary sensitivity of SERS.[6] For decades, plasmonic nanostructures on miscellaneous substrates[7,8,9] have enabled biomedical SERS applications from in situ point-of-care testing[10] to in vivo molecular sensing.[3] In particular, labeled plasmonic nanoparticles have been extensively utilized as SERS reporters for the in vivo detection and intraoperative guidance of cancerous lesions.[11,12,13] technical challenges of plasmonic nanoparticles probes, such as labeling of Raman-active molecules, high administered dosage, or toxicity, still remain substantial obstacles for SERS-based in vivo molecular detection.[14]. Repeated solid-state dewetting effectively constructs nanogap-rich Au nanoislands on the fiber-top surface, which induce strong electromagnetic (EM) hotspots and enable strong light excitation as well as highly sensitive SERS detection of biomolecules through the plasmonic probe
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