Simultaneous formation of ultra-thin MoSe2 nanosheets, Inorganic Fullerene-Like MoSe2 and MoO3 quantum dots using fast and ecofriendly Pulsed Laser Ablation in Liquid followed by microwave treatment

This research reports a rapid and scalable synthesis of MoSe2 Nanosheets (NSs), Inorganic Fullerene-Like (IF) MoSe2 and MoO3 quantum dots (QDs) with varying morphologies and crystal structures using Pulsed Laser Ablation in Liquid (PLAL) technique followed by microwave treatment of Bulk-MoSe2 powders. We show that using water as a solvent result in the formation of MoO3 QDs, single and few layered MoSe2 NSs and IF-MoSe2 structures from both Laser Modified (LM) and Laser Microwave Modified (LMM) MoSe2 samples. The presence of the predominant A1g mode in the Raman spectra of LM-MoSe2 and LMM-MoSe2 samples further showed the formation of single layer MoSe2 NS. Moreover, formation of small-sized MoSe2 heterolayers with an expanded interlayer spacing along the (002) planes for LMM samples which were subjected to microwave treatment for 30 min was demonstrated. Comparatively, for the samples subjected to microwave treatment for 60 min, most of the crystal orientations were vertical. The current study showed the controllable crystal orientation in MoSe2 samples by combined PLAL and microwave treatment. The two successive microwave steps led to change in the MoSe2 crystal orientation from horizontal to vertical. Selective oxygen incorporation induced by both PLAL and microwave treatment was also shown along the (100) and (002) planes for LM-MoSe2 and LMM-MoSe2, respectively. Understanding the selective oxygen incorporation in MoSe2 planes can shed light on the precise control of oxygenation in the crystal structures of 2D nanomaterials, synthesized heterostructures and nanocomposites.