Green synthesis of ultrathin 2D nanoplatelets, hematene and magnetene, from mineral ores in water, with strong optical limiting performance

Abstract

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...

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

“…Hematene and magnetene nanoplatelets were produced by mild sonication of the corresponding ores and were isolated as a water dispersion with a yield of about 10% for both products. Hematene nanocrystals were plain with an average size of 200 nm and very low size distribution (based on DLS and AFM analysis) and thickness between 1 and 1.5 nm . Magnetene nanocrystals were also plain with a mean thickness of 5.4 nm, and the majority of them have a lateral size of about 150 nm.…”

“…As regards their atomic structure, based on selected area electron diffraction (SAED) patterns, hematene showed a planar d-spacing of 0.23 nm that corresponds to the (113) lattice of hematite, while magnetene exhibited planar dspacings of 0.31, 0.24, and 0.21 nm which correspond to the (220), (311), and (400) planes of magnetite. 47 In Figure 1a, the UV−vis−NIR absorption spectra of two aqueous dispersions of hematene (0.45 mg/mL) and magnet-ene (1.95 mg/mL) are presented. As can be seen, the absorption spectrum of hematene is dominated by a relatively strong and broad absorption band extended from 300 to 600 nm, ascribed to ligand to metal charge transfer (LMCT) and Fe 3+ ligand field transitions (or d−d transitions), 50,51 while the absorption above 600 nm is assigned to d−d transitions and magnetically coupled pair excitations.…”

“…Recently, it was reported that hematene and magnetene nanoplatelets, under nanosecond laser excitation, exhibit strong reverse saturable absorption (RSA) behavior, giving rise to exceptional optical limiting performance. 47 The appearance of RSA behavior was ascribed to two-photon absorption (2PA), excited state absorption (ESA), nonlinear scattering, and thermal effects. 58 The different NLO absorptive response, i.e., the appearance of strong saturable absorption (SA) observed under femtosecond laser excitation in the present study, is due to different operational mechanisms contributing to the NLO absorption in this case, as will be discussed in the next.…”

“…The as prepared samples were characterized by various spectroscopic methods as discussed in detail elsewhere. 47 Ultrafast NLO Measurements. For the determination of the ultrafast NLO response of hematene and magnetene, Z-scan and OKE techniques were used.…”

“…Both fine hematene and magnetene nanoplatelets were purified from melamine by filtration (hydrophilic nylon membrane, 0.2 μm). The as prepared samples were characterized by various spectroscopic methods as discussed in detail elsewhere …”