In the past few decades, the development of optical probes for thiols has attracted great attention because of the biological importance of the thiol-containing molecules such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This tutorial review focuses on various thiol detection methods based on luminescent or colorimetric spectrophotometry published during the period 2010–2012. The discussion covers a diversity of sensing mechanisms such as Michael addition, cyclization with aldehydes, conjugate addition–cyclization, cleavage of sulfonamide and sulfonate esters, thiol–halogen nucleophilic substitution, disulfide exchange, native chemical ligation (NCL), metal complex-displace coordination, and nanomaterial-related and DNA-based chemosensors.
