Label-Free SERS Selective Detection of Dopamine and Serotonin Using Graphene-Au Nanopyramid Heterostructure

Abstract

Ultrasensitive detection and spatially resolved mapping of neurotransmitters, dopamine and serotonin, are critical to facilitate understanding brain functions and investigate the information processing in neural networks. In this work, we demonstrated single molecule detection of dopamine and serotonin using a graphene–Au nanopyramid heterostructure platform. The quasi-periodic Au structure boosts high-density and high-homogeneity hotspots resulting in ultrahigh sensitivity with a surface enhanced Raman spectroscopic (SERS) enhancement factor ∼1010. A single layer graphene superimposed on a Au structure not only can locate SERS hot spots but also modify the surface chemistry to realize selective enhancement Raman yield. Dopamine and serotonin could be detected and distinguished from each other at 10–10 M level in 1 s data acquisition time without any pretreatment and labeling process. Moreover, the heterostructure realized nanomolar detection of neurotransmitters in the presence of simulated body fluids. These findings represent a step forward in enabling in-depth studies of neurological processes including those closely related to brain activity mapping (BAM).

Bioanalytical applications of surface-enhanced Raman spectroscopy: de novo molecular identification

“…121 They also reported the detection of these neurotransmitters at concentrations as low as 10 −9 M in simulated body fluids supplemented with background serum proteins. The dominant vibrational band for dopamine was associated with the C=C stretching mode.…”

“…It was reported that the π-π interactions between the ring structures and the graphene contributed to the chemical enhancement. 121 Bailey et al detected the neurotransmitters: dopamine, serotonin, norepinephrine, epinephrine, and catechol to investigate the role of surface absorption in SERS. 122 The dominant vibrational bands were associated with phenol moiety, which suggest that this area of the neurotransmitter adsorbs to the SERS active-surface.…”

Fundamentals and applications of SERS-based bioanalytical sensing

“…Even in unpurified samples, single picomolar concentrations can be measured [155]. There is a variety of detected molecules, including TNT [155], neurotransmitters dopamine and serotonin [156], and incubated Escherichia coli [157]. Label-free SERS assays have also been developed using PDMS in an integrated microfluidic device for biomolecular detection [158].…”

A Review on Applications of Two-Dimensional Materials in Surface-Enhanced Raman Spectroscopy

“…For 2D materials used in hybrid SERS platform with patterned metallic SERS nanostructures, graphene is the ideal choice because graphene only has a few intrinsic Raman peaks and large-area high quality graphene is easily achievable. Another benefit of graphene is that its intrinsic peak intensity could be used to quantify the analytes [20,22].…”

“…Two-dimensional (2D) materials, such as graphene and molybdenum disulfide (MoS 2 ), have unique electronic and optical properties and thus attract wide interests in their potential applications in electronic devices, sensors, and energy generation [13][14][15][16][17][18]. In addition to the above-mentioned applications, graphene and other 2D materials have also been explored to enhance Raman signals [13,[19][20][21][22]. Since the discovery of graphene's Raman enhancement capability [23], extensive researches have been done to reveal the enhancing mechanism of twodimensional materials, as well as their application in Raman enhancement either with bare 2D material substrate or with hybrid metal/2D material substrate [24][25][26][27].…”