Figure 1c shows the transmission electron microscopy (TEM, TecnaiTM G2 F30, FEI, Hillsboro, OR, USA) image of the exfoliated product, from which one can see that the free-standing nanosheets were inhomogenous with different sizes and morphologies. Figure 1 Schematic illustration of liquid exfoliation process, XRD results, TEM, and theoretically

perfect crystal structure of WS 2 . (a) Schematic illustration of liquid exfoliation process from bulk WS2 to ultrathin nanosheets. (b) XRD results for pristine WS2 bulk (black line) and the exfoliated nanosheets (red line), the blue line is the standard WS2 diffraction peaks got from JCPDS card no. 85-1068. (c) TEM image of the exfoliated WS2 nanosheets. ABT263 (d) A theoretically

perfect crystal structure of the single-layered WS2. High-resolution TEM (HRTEM) image and the two-dimensional fast Fourier transform (FFT) analysis (Figure 2b,c) reveal the hexagonal lattice structure with the lattice spacing of 0.27 and 0.16 nm assigned to the (100) and (110) planes [17]. Further high-resolution TEM results for the selected regions for the inner and the edges of one nanosheet are shown in Figure 2b,d, respectively. Results indicate that the inner part of the nanosheets has a well-crystallographic structure without existence of defects. On the contrary, a clear disorder is observed at the edges; the result reveals a hexagonal arrangement see more of atoms with zigzag edges. The size distribution of as-prepared WS2 nanosheets was evaluated from the tapping-mode atomic force microscopy (AFM Dimension 3100 with Nanoscope IIIa controller, Veeco, CA, USA). As can be seen from Figure 2e, the diameter of the nanosheets

ranges from 200 to 500 nm, in accordance with the TEM observation. As also shown in Figure 2e, the randomly measured thicknesses for the nanosheets are ranging from 1.2 to 4.8 nm, where the maximum height profile Benzatropine of 4.9 nm is shown in Figure 2g. Considering that the c parameter of WS2 is 0.62 Å, the thickness of 1.8 to 4.9 nm denoted that the nanosheets comprised 2 ~ 8 single layers of WS2. Accidentally, some WS2 nanosheets have curled edges, rendering it possible to evaluate a sheet thickness during high-resolution TEM. One can see from Figure 2f that the nanosheet with 3 ~ 8 layers thick shows the presence of a high density of edges. Besides, the clear bend can be observed, which may arise from defects at the edges. Figure 2 Different types of imaging showing different characteristics of formed WS 2 nanosheets and FFT analysis. (a) TEM image of the WS2 nanosheets. (b, d) High-resolution TEM images for the selected regions are shown. (c) Two-dimensional FFT analysis for the WS2 nanosheets.