Excellent ultraviolet optical limiting properties of Se nanosheets

Abstract

Selenium (Se) is located in the fourth period of the periodic table in group VIA (element 34). In this experiment, three different solvents (isopropyl alcohol, N-methyl-2-pyrrolidone, and ethanol) were used to prepare the two-dimensional (2D) Se nanosheets, which were manufactured by the liquid phase exfoliation (LPE) method with a thickness of 3.35 ~ 4.64 nm and a transverse scale of several hundred nanometers. The nonlinear absorption (NLA) properties at 355, 532, and 1064 nm were studied using the open aperture Z-scan technique. Final results showed that Se nanosheets exhibited optical limiting (OL) effect in all three wavebands and three solvents, and had large two-photon absorption coefficients, especially in ultraviolet (UV) waveband. Which proved that Se nanosheets had great potential application as excellent OL materials in UV waveband. Our research broadens the path for the semiconductor field of Se, inspires the application of Se in nonlinear optics field.

Two-Dimensional Nb4AlC3 (MAX) and Nb4C3 (MXene): Excellent Optical Limiting Materials with Oppositely Applicated Waveband

“…The normalized transmittance ( T ) equation based on the OA Z-scan method is T = (1 – α l )/(1 – α 0 l ), where α and α 0 are the total absorption coefficient and the linear absorption coefficient, respectively, and l is the thickness of the sample, which is 2 mm. Equation is the calculation formula for a, where I ( z ) is the power density that varies with sample movement, I s is the SA intensity, and β is the TPA coefficient …”

“…The two-photon mechanisms of Nb 4 AlC 3 and Nb 4 C 3 are similar to those of graphene, selenium, and tellurium and can be described as follows: when the excitation photon energy reaches the threshold of TPA, the electron absorbs two photons sequentially or simultaneously to jump to a higher energy level, which macroscopically leads to a rapid decrease in transmittance. According to the NLA results, Nb 4 AlC 3 nanosheets exhibit greater modulation depth and larger β values at 1064 nm (low photon energy), which means that the TPA under low photon energy excitation has a larger energy band volume and thus more electrons are needed to absorb more photons to fill the energy band.…”

“…Two-dimensional nanomaterials such as graphene, carbon allotropes, and MXenes have attracted increasing attention in the fields of energy storage, catalysis, sensing, and optics − due to their excellent electronic properties and unusual physicochemical characteristics. − MXenes are a fast-growing family of 2D materials and are transition metal carbides or nitrides with the general formula M n +1 X n T x ( n = 1–3), , where M is a transition metal such as Ti, Nb, V, etc., X is a C or N element, and T x denotes surface terminations such as OH, O, F, and/or Cl, which are bound to the external M layer. , The MAX phases, which are predecessors to MXenes, are layered ternary carbides or nitrides with ceramic and metallic properties. − The general formula is M n +1 AX n ( n = 1–3), where A primarily consists of group IIIA or IVA elements (e.g., the Al element). − MXenes were obtained by selectively etching the A-layer atoms of the MAX phases . The discovery of MXenes has reignited interest in the investigation of MAX phases.…”