Light-emitting MXene quantum dots

Abstract

MXene (M n+1 X n ) is an emerging class of layered two-dimensional (2D) materials, which are derived from their bulk-state MAX phase (M n+1 AX n , where M: early transition metal, A: group element 13 and 14, and X: carbon and/or nitrogen). MXenes have found wide-ranging applications in energy storage devices, sensors, catalysis, etc. owing to their high electronic conductivity and wide range of optical absorption. However, the absence of semiconducting MXenes has limited their applications related to light emission. Research has shown that quantum dots (QDs) derived from MXene (MQDs) not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield (QY). The optical properties and photoluminescence (PL) emission mechanisms of these light-emitting MQDs have not been comprehensively investigated. Recently, work on light-emitting MQDs has shown good progress, and MQDs exhibiting multi-color PL emission along with high QY have been fabricated. The synthesis methods also play a vital role in determining the light emission properties of these MQDs. This review provides an overview of light-emitting MQDs and their synthesis methods, optical properties, and applications in various optical, sensory, and imaging devices. The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.

Low Temperature Step Annealing Synthesis of the Ti2AlN MAX Phase to Fabricate MXene Quantum Dots

“…The step annealed Ti 2 AlN MAX phase was further etched by wet chemical etching to obtain multilayered Ti 2 N MXene sheets. In this particular method, the Al layer was removed by acid-salt treatment of the Ti 2 AlN MAX phase in a KF-HCl etchant solution [10,26,45,55]. The effective formation and phase composition of multilayered Ti 2 N MXene sheets were analyzed using XRD, FE-SEM, and Raman spectroscopy respectively, and the corresponding results are demonstrated in Figure 3.…”

“…Owing to their interesting optical properties, they can be used as crucial materials in optical sensors [41,42], bio-imaging [34], optical modulator [43] etc. Comparatively, carbide MQDs [44,45] derived from the MAX phase containing a carbide group such as V 2 AlC [46], Nb 2 AlC [33], and Ti 3 AlC 2 [39] have been studied more than nitride MQDs [10,26]; thus, the exploration and broad study of the properties and applications of nitride based MQDs are necessary.…”

Quantum Dots Compete at the Acme of MXene Family for the Optimal Catalysis

“…Like other organic or inorganic QDs, optical spectroscopy characterization of MQDs is obviously strong evidence for the information of MQDs. Photoluminescence spectrum (PL), photoluminescence excitation spectrum (PLE), electrochemiluminescence (ECL), and UV–Vis spectra can be used to characterize the luminous behavior of the MQDs [ 89 , 223 ]. For example, the UV–Vis adsorption spectrum of Ti 3 C 2 MQDs shows the adsorption at 320 nm, corresponding to two luminescence peaks of 250 and 320 nm in the PLE spectrum (Fig.…”

MXenes Quantum Dots for Biomedical Applications: Recent Advances and Challenges

“…When synthetic using the molten salt method, a salt with a low melting point was added to the reactants, and after the salt is added, the temperature is controlled above the melting point of the salt, and the salt melts and acts as a solvent. [68] Cheng et al [66] synthesized Mo 2 C quantum dot/carbon nanosheet (Mo 2 C/C) composite using the molybdenum acetylacetonate as a precursor and a mixture of sucrose and NaCl homogeneously mixed (Figure 7). The size of the Mo 2 C quantum dot material was 2 ~3 nm, and the crystalline surface spacing is 2.37 × 10 À 10 nm, which is consistent with the height of the Mo 2 C (002) crystalline surface.…”