Photoinduced Separation of Strongly Interacting 2-D Layered TiS₂ Nanodiscs in Solution

Abstract

Colloidal 2-D layered transition metal dichalcogenide (TMDC) nanodiscs synthesized with uniform diameter and thickness can readily form the vertically stacked assemblies of particles in solution due to strong interparticle cohesive energy. The interparticle electronic coupling that modifies their optical and electronic properties poses a significant challenge in exploring their unique properties influenced by the anisotropic quantum confinement in different directions taking advantage of the controlled diameter and thickness. Here, we show that the assemblies of 2-D layered TiS2 nanodiscs are efficiently separated into individual nanodiscs via photoexcitation of the charge carriers by pulsed laser light, enabling the characterization of the properties of noninteracting TiS2 nanodiscs. Photoinduced separation of the nanodiscs is considered to occur via transient weakening of the interparticle cohesive force by the dense photoexcited charge carriers, which facilitates the solvation of each nanodisc by the solvent molecules.

Thickness-Dependent Characterization of Chemically Exfoliated TiS2 Nanosheets

“…60−62 The position of these peaks has been attributed to the size of the TiS 2 nanosheets, with laterally smaller and thinner nanosheets, resulting in a blue-shifted peak. 61…”

“…The interband transition peak (600 nm) is slightly blue-shifted compared to the water exfoliation (590 nm NMP, 596 nm water) (Table S2) as previously discussed; this blue shift indicates thinner nanosheets being stabilized in the solution, thus indicating that by solvent exchange with NMP, we are able to stabilize mono- and few-layered nanosheets (<3L) while it is less effective in stabilizing thicker nanosheets (>3L). 60,61,67…”

Two-Dimensional Colloidal Nanocrystals

“…These light-induced dispersions are stable over time, and the vertical stacks can be created again via a decrease of the solvent polarity. 274 The same TiS 2 nanodiscs can also be vertically oriented on a surface using electric fields (Figure 34b). In contrast to other anisotropic nanocrystals such as nanorods, applying a continuous electric field does not result in orientation control of the nanodiscs in solution.…”

Two-Dimensional Metallic Niobium Diselenide for Sub-micrometer-Thin Antennas in Wireless Communication Systems

“…The detailed fabrication conditions and procedures are described in the Experimental Section. The UV–visible absorption spectrum of the NbSe 2 colloidal solution (Figure a) reveals two broad absorption peaks around 307 and 500 nm arising from interband transitions from the Fermi level to the band in the ΣM direction, which is characteristic of metallic nanomaterials. , The peaks at 307 and 500 nm were associated with the absorption of violet and red colors, respectively, whose mixture leads to the magenta color of the NbSe 2 colloidal solution (see the digital photograph in the inset of Figure a). Moreover, the Tyndall scattering shown in the inset of Figure a reveals the good colloidal dispersion of the NbSe 2 sheets in deionized water, which was confirmed by the zeta-potential values of less than −46 mV irrespective of the solution concentration (see Figure S3b), owing to intrinsic polarity and surface functional groups. , Although the colloidal solution of exfoliated NbSe 2 is dispersible up to 5 wt % in deionized water, it remains highly crystalline and conducting.…”