Functionalization of Two‐Dimensional MoS2: On the Reaction Between MoS2 and Organic Thiols

Abstract Two‐dimensional layered transition metal dichalcogenides (TMDs) have attracted great interest owing to their unique properties and a wide array of potential applications. However, due to their inert nature, pristine TMDs are very challenging to functionalize. We demonstrate a general route to functionalize exfoliated 2H‐MoS 2 with cysteine. Critically, MoS 2 was found to be facilitating the oxidation of the thiol cysteine to the disulfide cystine during functionalization. The resulting cystine was physisorbed on MoS 2 rather than coordinated as a thiol (cysteine) filling S‐vacancies in the 2H‐MoS 2 surface, as originally conceived. These observations were found to be true for other organic thiols and indeed other TMDs. Our findings suggest that functionalization of two‐dimensional MoS 2 using organic thiols may not yield covalently or datively tethered functionalities, rather, in this instance, they yield physisorbed disulfides that are easily removed.