The use of single layer MoS2 (SLM) in nano-devices is of significant interest, and its optoelectronic properties have been shown to be able to be tuned by modifying its surface. To explore this, radical reactions of compounds such as 4-nitrobenzenediazonium tetrafluoroborate (4-NDB) with MoS2 in aqueous solution have been previously investigated as a means for facile modification, but a detailed study has yet to have been carried out of the nature of its chemical reactivity with MoS2 on Au(111) substrates with varying layer thicknesses. Here, the mechanical, optical and chemical properties of single and multilayer (bulk) MoS2 on Au(111) substrates were investigated before and after being functionalized with 4-NDB in aqueous solution. By employing AFM to study the exfoliated MoS2 sheets on Au substrates after 4-NBD modification, it was found that the nitrobenzene formed a multilayer molecular film on the MoS2 surface. The extent of coverage of nitrobenzene on SLM was observed to be larger than on bulk MoS2, mostly likely due to increased electronic coupling between monolayer MoS2 and the gold substrate. Nitrobenzene films formed on SLM and bulk MoS2 could be readily worn away by AFM under modesty applied loads of 10 nN and 3 nN, respectively, indicating that the binding of nitrobenzene on SLM is stronger than that on bulk MoS2. The thickness of molecular films formed was observed to be ~1.5 nm regardless of the number of MoS2 layers or, the solution reaction concentration.

Reactivity of 4-NBD with single and multilayer layer MoS2 on Au(111)

2019 Fall National Meeting

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