Tunable photoluminescence on 2D WS₂ quantum dots

Laser synthesis of nanoparticles in a liquid has already opened a new page in the history of the development of the in-test-tube method for the fabrication of nanomaterials. A fascinating continuation of the topic is the synthesis of quantum-sized nanostructures with complex topology/morphology, when the initial materials for their fabrication are strongly anisotropic van der Waals (vdW) and 2D materials. Two aspects determine the photoluminescence properties of such nanostructures at once: the dependence of the emission wavelength is determined by the size quantization effects as in conventional semiconductors, while the photoluminescence intensity results from the dependence of relative positions of the energy bands on the number of layers in the nanostructure. In this work, the progress on the development of straightforward laser and auxiliary ultrasonic methods for the synthesis of quantum-sized photoluminescent nanostructures from WS₂ powder is reported. By combining various solvents and different treatment times, the possibility of tuning the photoluminescence spectra of the obtained 2D WS₂ flakes and quantum dots over a wide spectral range is demonstrated.