Table 1.

List of several potential SERS reporter/probe molecules. General requirements of the molecule: it adsorbs to both gold and silver surfaces; knowledge about the vibrational assignments, there are calculations and very solid work about all qualitative aspects of its SERS spectrum on different substrates.

Raman reporter	Advantages	Disadvantages
SH‐functionalized molecules	High affinity to gold surfaces, covalent binding	High water insolubility
Recommended: 4‐Mercaptobenzoic acid (deprotonated at pH 10) or the boronic acid equivalent	Polar aromatic thiol Good water solubility (pH 10) An attractive candidate as a universal probe and for modelling the surface	pH dependence of SERS fingerprint
Thiophenol	Small, well‐defined structure (conformation) High binding affinity relatively independent on the surfactant (citrate, CTAB) A good candidate as model analyte for most of the surfaces	Extreme toxicity and difficult handling (low vapor pressure, correct storage under inert gases)
1‐ and 2‐ Naphthalenethiol, 4‐Biphenylthiol	Strong, rich distinctive signal	Moderate toxicity
N, NHx‐functionalized molecules	Ideal test analytes for silver surfaces Good water solubility	pH dependence of surface coverage and of SERS fingerprint
Recommended: Adenine	A good candidate for non‐covalently binding models	Domination by one strong band mode (ca. 737 cm−1)
2,2′‐Bipyridine	Strong, rich distinctive signal
Melamine	Strong, rich distinctive signal Relevant in the context of food adulteration
Dyes (not recommended)	Very strong SE(R)RS on silver and gold surfaces High water solubility	Change of optical cross‐section upon adsorption to metal
Rhodamine 6G, Crystal violet, Malachite green, Methylene blue	Mostly used analytes for testing new SERS substrates Raman reporter molecules in many applications	Strong electronic resonances High fluorescence background in RRS spectra (difficult to correctly determine EF, especially for Rhodamine 6G)
Riboflavin (vitamin B2)	Distinctive SERS spectrum Weaker electronic resonances Biological and food additive relevance	Weak surface adsorption Large size Low water solubility