Q: What are the best storage conditions for thiols?
A: In principle, thiols should be stored in dry state, at low temperatures (~ -20°C) and under argon. In solution, they (especially EGn-terminated ones) are less stable, and we do not advise using solutions that are older than ~ 1 week.
Q: Which solutions to use to form SAMs on gold?
A: The standard prep is a 2 mM ethanolic solution.
Q: How rapidly do SAMs form?
A: Depends. For methyl-terminated thiols, the formation of a complete monolayer is virtually instantaneous. For thiols terminated in polar groups (e.g. carboxylic acids) the kinetics of SAM formation is considerably slower, and in some cases (e.g. highly charged end-groups) the monolayers that form are not complete. One has to play around with the conditions or prepare mixed SAMs.
Q: Do disulfides form SAMs?
A: Absolutely yes.
Q: Does the quality of a monolayer depend on chain length?
A: Marginally. For very short thiols (roughly, six or less carbons) there are quite a few defects; for longer chains, the quality of SAMs that form does not, to a good approximation, depend on chain length.
Q: What are the differences in adsorption characteristics of various EGn thiols?
A: Virtually none for n>2. In fact, resistances to bacterial and cell adsorption of EG3 and EG6 thiols are very similar. Different chain lengths are, however, useful in detailed mechanistic studies or when making mixed SAMs.
Q: What about protected thiols? Do they form monolayers?
A: Yes, for example AcS groups deprotect on contact with gold (see works by Allara and Whitesides from the beginning of the 90s). In general, however, some work might be necessary to figure out optimal conditions for the formation of good monolayers. On the other hand, for some important thiols - e.g., aldehyde-terminated ones - acyl protection of sulfur is the only way to get stable compounds. Please send us an email to learn more about pros and cons of using protected thiols.
Q: Are thiols toxic?
A: The vast majority of compounds we sell are relatively harmless. The unpleasant odor (especially, of short-chain molecules) is their most cumbersome characteristic.