2D Non-van der Waals Nanoplatelets of Hematene and Magnetene: Nonlinear Optical Response and Optical Limiting Performance from UV to NIR.

Recently, the preparation of some hematene and magnetene ultrathin non van der Waals (non-vdW) 2D nanoplatelets was reported starting from hematite and magnetite natural iron ores. The present work reports on the determination and evaluation of the nonlinear optical response and the optical limiting (OL) action of these 2D nanoplatelets dispersed in water under ns laser excitation. The obtained results show that both hematene and magnetene exhibit strong nonlinear absorption and refraction, comparable and even larger than those of other van der Waals (vdW) 2D counterpart materials. In addition, due to their strong nonlinear absorption, both hematene and magnetene show exceptional OL performance from the UV to visible, attaining very low values of optical limiting onset (OLon ), comparable and even lower than that of vdW 2D nanomaterials, such as graphene, graphene oxide, other transition metal dichalcogenides like MoS2 , WS2 and MoSe2 , black phosphorous and antimonene. Moreover, hematene was found to exhibit more efficient OL action than magnetene for all the excitation wavelengths studied, attributed to more efficient ligand to metal charge transfer. The present findings open new possibilities for the potential use of these non-vdW 2D materials in photonics and optoelectronics, e. g., as optical limiters and optical switchers.

Strong Ultrafast Saturable Absorption and Nonlinear Refraction of Some Non-van der Waals 2D Hematene and Magnetene Nanoplatelets for Ultrafast Photonic Applications.

In the present work, some non-van der Waals (non-vdW) 2D materials, namely, hematene and magnetene nanoplatelets, were synthesized starting from hematite and magnetite ores, respectively, using a green synthesis method, and they were dispersed in water. Then, their ultrafast nonlinear optical (NLO) response was studied under 50 fs, 400 nm laser excitation. Both non-vdW 2D materials revealed strong saturable absorption with NLO absorption coefficient ß, saturable intensity, and modulation depth of about -33.2 × 10-15 m/W, 320 GW/cm2, and 19%, respectively, for hematene, and about -21.4 × 10-15 m/W, 500 GW/cm2, and 17% for magnetene. These values are comparable to those of other vdW 2D materials, such as graphene, transition metal dichalcogenides (TMDs) like MoS2, WS2, and MoSe2, black phosphorus (BP), and some MXenes (Ti3C2Tx), recently reported as efficient saturable absorbers. In addition, both hematene and magnetene dispersions displayed strong Kerr type NLO refraction with nonlinear refractive index parameters γ' comparable and even larger than those of van der Waals 2D materials. In all cases, hematene was found exhibiting significantly larger optical nonlinearities than magnetene, most probably due to the formation of a more efficient charge transfer system. The results of the present work are strongly suggesting that hematene and magnetene can have applications in a wide range of photonic and optoelectronic applications.

Iridium-Based Nanohybrids: Synthesis, Characterization, Optical Limiting, and Nonlinear Optical Properties.

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.

A new class of third-order nonlinear optical materials: laser pulse-duration dependant saturable absorption and nonlinear refraction in platinum(II) diimine-dithiolate complexes.

The third-order nonlinear optical (NLO) properties of a series of platinum diimine-dithiolate complexes [Pt(N^N)(S^S)] were investigated by means of Z-scan measurements, revealing second hyperpolarizability values up to 10-29 esu, saturable absorption properties, and nonlinear refractive behaviour, which were rationalized also by means of DFT calculations.