Two-dimensional nanohybrid of MoS2 and Rose Bengal: Facile solution growth and band structure probing

We report a facile growth of 2D layered nanohybrid (LNH) of liquid-phase exfoliated MoS2 flakes and Rose Bengal (RB) molecules as charge-transfer complex, evidenced with several methods including UV-vis absorption and photoluminescence. Raman line-broadening and red-shift to lower-wavenumber side of A(1g) peak of MoS2 in nanohybrid confirms adsorption of p-type RB as n-type dopant including lattice-strain modulation. Nanohybrid also shows better stability in solution than its constituent components as evidenced by Zeta potential results. The crystal phase invariance of MoS2 after forming nanohybrid has been confirmed from TEM and Raman studies. The resulting 2D-0D nanohybrid is found to suppress the intrinsic n-type nature of MoS2, which reflects as reduction of rectification ratio from 3.1 to 2.6, as observed in STM I-V measurements. The band edges are identified by measuring the local density-of-states (LDOS) as differential tunnel conductance (dI/dV) at room-temperature on an UHV-STM system, which strongly emphasizes the formation of type-II heterojunction of 2D MoS2 as acceptor and OD RB as donor. The strategy explored here is the facile growth of 2D-0D nanohybrid by assembling organic molecules on 2D MoS2 flakes to achieve a distinct electronic structure and provide unprecedented capabilities to engineer the band structure of 2D layered materials.