Curved 2D WS2 Nanostructures: Nanocasting and Silent Phonon Mode
Layered two-dimensional (2D) materials and their heterostructures possess excellent optoelectronic properties due to their unique planar features. However, planar structures can only selectively support the fundamental optical modes, which is averse to fully exploit the potentials of the 2D materials. Here, a novel type of tungsten disulfide (WS2) nanoparticles (NPs) with uniform size and morphology and highly ordered WS2 supercrystals (SCs) are synthesized by nanocasting process using ordered mesoporous silica as template. Due to the curved feature of individual nanostructures, their Raman signals show complex dependence behavior on the excitation wavelength, excitation power and temperature. Significantly, the silent phonon mode becomes Raman active due to the curvature of the interlaced WS2 layers. We believe that curved features will greatly enrich the optoelectronic applications of 2D materials.