Colloidal dispersions of solution processed Transition Metal Dichalcogenides (TMDs, MX2) have attracted considerable attention due to the complementarity of their semi-conductive properties relative to other low dimensional nanomaterials (e.g. graphene, BN, aluminosilicates, phosphenes, etc.). However, energy intensive sonication, aggressive chemistries, large concentration of dispersants, and a small choice of stabilizing solvents limit scalable strategies, and thus access to large quantities of well-defined layers. Mechanistically, redox exfoliation generates polyoxometalates in-situ, which exfoliate and stabilize single-to-few layer TMD sheets in the absence of shear or cavitation forces via columbic repulsion. Kinetically, polyoxometalate form quickly, while surface adsorption and delamination is rate limiting. From this insight, substantial single-to-few layer yields (&gt; 10%) and drastically reduce reaction times (&lt; 24 hrs) are achieved through optimizing the rate of polyoxometalate formation and use of shear forces. This unique access to stable dispersions of Group IV – VII TMDs in polar organic solvents (acetonitrile, acetone, alcohols) at high concentration (10% w/w) afford development of Group-specific strategies for covalent layer functionalization that compliment other methods directed toward passivation of defects and terminal edges. For example, direct hybridization of Group VI 2H-MX2 TMDs (e.g. MoS2, MoSe2, MoTe2) via alkyl organometallic chemistry yield layers dispersed in non-polar solvents (THF, CHCl3, CH2Cl2) with –ene and –yne functionality and enhanced oxidative stability. Reduction of Group V 2H-MX2 (e.g. VS2, TaS2, NbS2, NbSe2, NbTe2), such as via amines and phosphines, tune optoelectronic properties in addition to increasing oxidative stability. The development of a general, transferable, and scalable approach to stable, functionalized TMD dispersions is expanding evaluation of this 2D nanomaterial family for numerous bulk polymer technologies, such as thermal/optical coatings, structural nanocomposites, and inks for flexible electronics.

Covalent functionalization of redox-exfoliated layered transition metal dichalcogenides (group IV – VII)

2019 Spring National Meeting

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