In the present work, some MoS 2 and WS 2 nanosheets were prepared and characterized. Depending on the preparation procedures, trigonal prismatic (2H) or octahedral (1T) coordination of the metal atoms was obtained, exhibiting metallic (1T) or semiconducting (2H) character. Both MoS 2 and WS 2 nanosheets were found exhibiting large nonlinear optical (NLO) responses, strongly dependent on their metallic (1T) or semiconducting (2H) character. Therefore, the semiconducting character of MoS 2 and WS 2 exhibits positive nonlinear absorption and strong self-focusing behavior, while their metallic character counterparts exhibit strong negative nonlinear absorption and important self-defocusing behavior. In addition, the semiconducting MoS 2 and WS 2 were found exhibiting important and very broadband optical limiting (OL) action extending from 450 to 1750 nm. Therefore, by selecting the crystalline phase of the nanosheets, that is, their semiconduction/metallic character, their NLO response can be greatly modulated. The results of the present work demonstrate unambiguously that the control of the crystalline phase of MoS 2 and WS 2 provides an efficient strategy for 2D nanostructures with custom-made NLO properties for specific optoelectronic and photonic applications such as OL, saturable absorption, and optical switching.
Following the long-standing experience of the liquid exfoliation of graphite for the production of graphene, a number of analogous van der Waals 2D nanomaterials have been also produced and studied...
The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO2 and PVP-Ir/IrO2 types, as well as non-coated Ir/IrO2 nanoparticles, are synthesized using different synthetic protocols and characterized in terms of their chemical composition and morphology via X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM), respectively. Furthermore, their nonlinear optical (NLO) response and optical limiting (OL) efficiency are studied by means of the Z-scan technique, employing 4 ns laser pulses at 532 and 1064 nm. The results demonstrate that the PVP-Ir/IrO2 and Ir/IrO2 systems exhibit exceptional OL performance, while PVP-IrO2 presents very strong saturable absorption (SA) behavior, indicating that the present Ir-based nanohybrids could be strong competitors to other nanostructured materials for photonic and optoelectronic applications. In addition, the findings denote that the variation in the content of IrO2 nanoparticles by using different synthetic pathways significantly affects the NLO response of the studied Ir-based nanohybrids, suggesting that the choice of the appropriate synthetic method could lead to tailor-made NLO properties for specific applications in photonics and optoelectronics.
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