Layer-by-Layer Sorting of Rhenium Disulfide via High-Density Isopycnic Density Gradient Ultracentrifugation

Abstract

Isopycnic density gradient ultracentrifugation (iDGU) has been widely applied to sort nanomaterials by their physical and electronic structure. However, the commonly used density-gradient medium iodixanol has a finite maximum buoyant density that prevents the use of iDGU for high-density nanomaterials. Here, we overcome this limit by adding cesium chloride (CsCl) to iodixanol, thus increasing its maximum buoyant density to the point where the high-density two-dimensional nanomaterial rhenium disulfide (ReS2) can be sorted in a layer-by-layer manner with iDGU. The resulting aqueous ReS2 dispersions show photoluminescence at ∼1.5 eV, which is consistent with its direct bandgap semiconductor electronic structure. Furthermore, photocurrent measurements on thin films formed from solution-processed ReS2 show a spectral response that is consistent with optical absorbance and photoluminescence data. In addition to providing a pathway for effective solution processing of ReS2, this work establishes a general methodology for sorting high-density nanomaterials via iDGU.

Advent of 2D Rhenium Disulfide (ReS2): Fundamentals to Applications

“…reported the exfoliation and layer-by-layer sorting of ReS2 in aqueous surfactant solutions using iDGU technique. [43] Both chemical and liquid exfoliation require extensive post-exfoliation modifications. The problem of lithium intercalation and post-exfoliation modification was overcome by growing a thin film of ReS2 by the CVD method, followed by exfoliation of ReS2 thin-films in Nmethyl-2-pyrrolidone (NMP) in an ultrasonication bath.…”

Low-Dimensional ReS2/C Composite as Effective Hydrodesulfurization Catalyst

“…The absence of the (002) reflection has been reported for MoS 2 and WS 2 layers with no preferential orientation and random arrangement [26,27]. The Raman spectrum showed in the Figure 1b indicates the characteristic Raman modes (labeled III to V) for ReS 2 [3,28]. The signal located~157 cm −1 corresponds to the overlap of Eg-like (III and IV) vibrations, and the peak at~210 cm −1 resulted from the Ag-like (V) vibrational mode.…”

“…Figure 3a shows two Re 4f peaks at 41.4 eV and 43.8 eV, corresponding to the core levels 4f 7/2 and 4f 5/2 respectively for Re +4 . Figure 3b shows two S2p characteristic peaks located at 161.8 eV and 163.0 eV, ascribed respectively to the core levels 2p 3/2 and 2p 1/2 of S −2 [28,35]. Also, the S/Re atomic ratio obtained by XPS was about 1.8, indicating the formation of sulfur-deficient ReS 2−x layers, which is consistent with the energy-dispersive X-ray spectroscopy (EDS) spectrum analysis ( Figure S1).…”

Solution-processed two-dimensional materials for ultrafast fiber lasers (invited)

“…However, variations of the standard centrifugation exist. Density gradient ultracentrifugation allows a more precise control on the number of layers and lateral size [181][182][183], where flakes separate according to their density through a density gradient. However, this process is time consuming and has a very low yield, and thus is not useful for practical applications, including SAs.…”