Toward Plasmonic Neural Probes: SERS Detection of Neurotransmitters through Gold‐Nanoislands‐Decorated Tapered Optical Fibers with Sub‐10 nm Gaps

Abstract

Integration of plasmonic nanostructures with fiber‐optics‐based neural probes enables label‐free detection of molecular fingerprints via surface‐enhanced Raman spectroscopy (SERS), and it represents a fascinating technological horizon to investigate brain function. However, developing neuroplasmonic probes that can interface with deep brain regions with minimal invasiveness while providing the sensitivity to detect biomolecular signatures in a physiological environment is challenging, in particular because the same waveguide must be employed for both delivering excitation light and collecting the resulting scattered photons. Here, a SERS‐active neural probe based on a tapered optical fiber (TF) decorated with gold nanoislands (NIs) that can detect neurotransmitters down to the micromolar range is presented. To do this, a novel, nonplanar repeated dewetting technique to fabricate gold NIs with sub‐10 nm gaps, uniformly distributed on the wide (square millimeter scale in surface area), highly curved surface of TF is developed. It is experimentally and numerically shown that the amplified broadband near‐field enhancement of the high‐density NIs layer allows for achieving a limit of detection in aqueous solution of 10−7 m for rhodamine 6G and 10−5 m for serotonin and dopamine through SERS at near‐infrared wavelengths. The NIs‐TF technology is envisioned as a first step toward the unexplored frontier of in vivo label‐free plasmonic neural interfaces.

“Afterglow” Photodynamic Therapy Based on Carbon Dots Embedded Silica Nanoparticles for Nondestructive Teeth Whitening

“…Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemical structures of CDs@SiO 2 . FT-IR spectrum analysis identified stretching vibrations for O–H (3190 cm –1 ), C–H (2920 cm –1 ), CO (1710 cm –1 ), CN/N–H (1625 cm –1 ), C–N/C–H (1390 cm –1 ), and C–O (1160 cm –1 ) bonds, − implying the formation of polyaromatic structures and the presence of related residues at the edge of PCDs and FCDs (Figure e,f). The differing feature was that FCDs had a C–F vibrational peak at 1033 cm –1 due to the presence of fluorine atom doping (Figure f).…”

Resonance-Assisted Surface-Enhanced Raman Spectroscopy Amplification on Hierarchical Rose-Shaped MoS2/Au Nanocomposites

“…According to the above results, S a = 250.11, b = 3509, thus, LOD = 2.1 × 10 –9 M which is the LOD of CV molecules on MoS 2 /Au-6 NCs substrate. The LOD of Au-modified MoS 2 substrate is superior to that of Au nanoislands-decorated optical fibers with 10 nm gaps …”

“…The LOD of Au-modified MoS 2 substrate is superior to that of Au nanoislands-decorated optical fibers with 10 nm gaps. 42 To quantitatively evaluate the Raman signal enhancement capabilities of different substrates, the enhancement factor (EF) of MoS 2 and MoS 2 /Au-6 samples is calculated by the following equation: 43…”

Illuminating the Brain: Advances and Perspectives in Optoelectronics for Neural Activity Monitoring and Modulation

“…[79] TFs possess the ability to rapidly transition between uniformly transmitting light over a large area and delivering tightly focused light. [83,93] Different wavelengths of light can be separately adjusted and delivered to particular parts of the space. TF probe comprises a single slender and pointed waveguide, thus keeping invasive damage to a minimum.…”