Fig. 4: LODs and ss-SERS spectra of primary neurotransmitters for different concentrations ranging from 1 mM (10-3 M) to 1 aM (10−18 M).
From: Spread spectrum SERS allows label-free detection of attomolar neurotransmitters
a The characteristic Raman peak intensities of ss-SERS for acetylcholine of the learning neurotransmitter associated with Alzheimer’s dementia depending on neurotransmitter concentrations. The ss-SERS spectra exhibit a major SERS peak at 1150 cm−1 assigned to CH3 rocking and CH2 wagging. δ bending, τ twisting, ω wagging, ν stretching, ρ rocking. (The output power of the laser: 25 mW, the power at the sample: 1 mW, accumulation time: 10 s.) b Limit of detection for primary neurotransmitters down to attomolar concentrations. The nonlinear fit curves based on the experimental data for the neurotransmitters agree well with the Freundlich isotherm-like behavior \(\left( {\log {q}_{\mathrm{e}} = \log {K}_{\mathrm{F}} + \frac{1}{{n}}\log {C}_{\mathrm{e}}} \right)\), where qe, KF, n, and Ce represent the ss-SERS peak intensity, Freundlich isotherm constant, Freundlich isotherm exponent, and concentration, respectively.
