Synthesis and characterization of metal sulfide nanoribbons on graphene by self-assembly of inorganic ions

Abstract text (incl. figure legends and references)

Bottom-up synthesis of nanostructures on surfaces depends on the self-assembly of nanoscale building blocks. The diversity of accessible nanostructures, however, have been constrained by the limited choice of atomic and molecular building blocks that can be evaporated on a surface. Here, we bypass this limitation by using complex inorganic ions generated from electrospray ionization as building blocks to synthesize nanostructures on surfaces. We deposited HMo_nS_3n+1^­– (n = 4-8) ions onto a freestanding single-layer graphene by electrospray ion-beam deposition (ESIBD), and imaged the resulting nanostructures by aberration-corrected scanning transmission electron microscopy (STEM). The molecules form anisotropic, single-layered, crystalline MoS₂ nanoflakes (< 20 nm²), which in turn self-assemble into MoS₂ nanoribbons extending as far as 1 μm (Fig. 1). The widths of the nanoribbons were tuned by the precursors, as the HMo_nS_3n+1­^– (n = 4-8) ions formed 4 ± 1 nm wide nanoribbons, the HMo_nS3_n+1­^– (n = 5-8) ions 5 ± 2 nm wide nanoribbons, and the HMo_nS_3n+1­^– (n = 6-8) ions formed 8 ± 3 nm wide ones. This first observation of such nanostructures evidences the potential of this approach to prepare previously inaccessible nanomaterials on surfaces.

Figure 1 HMo_nS^_3n+1­^– ions were deposited onto single layer graphene by ESIBD, and self-assembled into 1 μm long monolayer MoS₂ nanoribbons as observed by STEM.