Unveiling the Structure of MoS_x Nanocrystals Produced upon Laser Fragmentation of MoS₂ Platelets

Abstract

Transition-metal dichalcogenide MoS 2 nanostructures have attracted tremendous attention due to their unique properties, which render them efficient nanoscale functional components for multiple applications ranging from sensors and biomedical probes to energy conversion and storage devices. However, despite the wide application range, the possibility to tune their size, shape, and composition is still a challenge. At the same time, the correlation of the structure with the optoelectronic properties is still unresolved. Here, we propose a new method to synthesize various morphologies of molybdenum sulfide nanocrystals, on the basis of ultrashort-pulsed laser fragmentation of MoS 2 platelets. Depending on the irradiation conditions, multiple MoS x morphologies in the form of nanoribbons, nanospheres, and photoluminescent quantum dots are obtained. Besides the detailed structural analysis of the various crystals formed, the structure–property relation is investigated and discussed.

SLM-processed MoS2/Mo2S3 nanocomposite for energy conversion/storage applications

“…Laser-based thinning can effectively exfoliate MoS 2 in a controlled manner 24 to enable green fabrication of 3D shapes from 2D nanomaterials 25 , 26 , and improve the charge capacitance properties of Mo 2 S 3 nanostructures 27 . The thinning mechanism of MoS 2 , with a high laser absorption coefficient due to the weak van der Waals forces between poorly coupled MoS 2 layers, can be attributed to localized temperature-dependent sublimation of upper layers of bulk 2H-MoS 2 lattice, arising through the absorption of high-energy laser 24 , 25 , 28 . At the next steps, laser irradiation on thinned 2H-MoS 2 can lead to further photoinduced exfoliation to form few-layered nanosheets 25 .…”

“…The thinning mechanism of MoS 2 , with a high laser absorption coefficient due to the weak van der Waals forces between poorly coupled MoS 2 layers, can be attributed to localized temperature-dependent sublimation of upper layers of bulk 2H-MoS 2 lattice, arising through the absorption of high-energy laser 24 , 25 , 28 . At the next steps, laser irradiation on thinned 2H-MoS 2 can lead to further photoinduced exfoliation to form few-layered nanosheets 25 . On the other hand, the more laser reflection due to the high reflection ratio of Mo powder 28 , the more thinning of 2H-MoS 2 existing nearby Mo powders 25 .…”

“…At the next steps, laser irradiation on thinned 2H-MoS 2 can lead to further photoinduced exfoliation to form few-layered nanosheets 25 . On the other hand, the more laser reflection due to the high reflection ratio of Mo powder 28 , the more thinning of 2H-MoS 2 existing nearby Mo powders 25 .…”

“…Accordingly, high-energy laser processing of MoS 2 can impose a highly localized temperature resulting in the thinning of MoS 2 as well as the creation of many α-phase nucleation sites for 2H to 1T phase transformation 25 , 26 , 31 . Mo 2 S 3 nanostructures can due to surface phase transformation also be formed through thermal annealing or sputtering of MoS 2 in an Ar-isolated atmosphere and at high temperatures above 1300 ºC 25 .…”

Laser-Assisted Fabrication for Metal Halide Perovskite-2D Nanoconjugates: Control on the Nanocrystal Density and Morphology

“…Some of the nanohexagons remain as previously but also quite spherical nanocrystals appeared from their partial fragmentation. The nanocrystals transform to nanoribbons through a laser-induced melting and subsequent recrystallization due to the laser energy absorption [43]. Very recently, similar structures have been observed through temperature-driven transformation and the rearrangement of atoms at the connecting facets [44].…”