Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical technique for ultrasensitive detection of chemicals and biomolecules. As the high sensitivity of SERS requires analytes to be in close contact with a plasmonic substrate, the detection of analyte molecules with low chemical affinity towards the substrate is thus limited, for example dopamine molecules as well as other neurotransmitters (NTs), which are the focus within this thesis. Two binding methods of NTs to SERS substrates will be covered: by Cucurbit[n]uril (CB[n]) and by Fe(III) ions. The fundamental resonance modes of NTs molecules and ultratrace NTs SERS sensing are discussed in detail. Further exploration of SERS substrates in the format of oil/water interfacial film will also be reported. The SERS application integrated with microfluidic techniques will be discussed in the final part of this thesis.