Synthesis, Characterization, and Typical Application of Nitrogen‐Doped MoS₂ Nanosheets Based on Pulsed Laser Ablation in Liquid Nitrogen

Abstract

One group of 2D layered materials is the transition metal dichalcogenides (TMDs) with MX 2 structure, where M denotes a transition metal such as Mo, W, Re, Nb, etc. and X ascertains a chalcogen atom, namely, S, Se, and Te. Unlike graphene's single carbon atomic-thick layer, a monolayer of TMDs consists of X-M-X sandwiches which are interacted by interlayer weak van der Waals forces and strong in-plane covalent bonding between atoms. As a result of their interesting and diverse structural, electronic, optical, mechanical, chemical, and thermal properties, this class of materials is still a topic of many recent scientific studies. [1][2][3][4][5][6][7] Particularly, MoS 2 shows a potential application in 2D nanoscale technology. [1,[8][9][10] The bandgap of MoS 2 semiconductor undergoes from indirect 1.29 eV (bulk) to direct 1.90 eV (monolayer) transitions. [5] The monolayer MoS 2 contains large specific surface areas, strong visible light-absorbing ability, and extreme flexibility against the bulk MoS 2 . [6,11] Such intriguing properties make MoS 2 a perfect alternative material for numerous applications such as photocatalysts, [12,13] photodetectors, [14,15] field-effect transistors, [16] solar cells, [17] and biomedical purposes [18,19] as well as optical fiber sensors (OFS). [10,20] The latter is a well-known sensor due to high sensitivity, noise and electromagnetic interference immunity, compact size, low cost, and multiplex capability. The OFS applications based on Fabry-Pérot interferometer (FPI) include industry, environment, medical care, homeland security, and defense. A simple and low-cost ultrasensitive configuration has been shown to upgrade FPI-acoustic OFS. Owing to high strength, flexibility, and relatively small Young's modulus, the MoS 2 membrane significantly improves the sensor sensitivity against others. [10]

In-Situ Generation of Nitrogen-Doped MoS2 Quantum Dots Using Laser Ablation in Cryogenic Medium for Hydrogen Evolution Reaction

“…In other words, the N-MoS 2 QDs formation mechanism relies on the pulsed laserinduced thermal shock waves and interlayer position of N 2 causes to exfoliate flakes due to high temperature gradient. Subsequently, the sudden and rapid expansion that occurs during laser irradiation leads to a phase transition from liquid to gaseous [21,22]. Figure 5d depicts the covalent N-doping of MoS 2 QDs during the synthesis of PLA in cryogenic liquid-LN 2 , demonstrating the replacement of N at the S locations.…”

“…The position of A and B peaks is located towards the direct excitonic transitions, which can be shifted by changing the number of layers. Moreover, the position of C and D peaks arises from the direct transition that occurs by provoking the deep valence to the conduction bands [22]. However, the characteristic excitonic peaks notably vanish during the creation of N-MoS 2 QDs owing to the effects of quantum confinement and the quasi-continuous electronic energy band structure.…”

“…Figure 3a illustrates the normalized optical absorption spectrum of N-MoS2 QD excitonic peaks of material of interest appear at 256 and 282 nm (λ < 300 nm) in the UV region [40,46]. Conversely, the excitonic peaks are observed at A: 677, B: 627, and D: 402 nm in the form of nanosheets [22]. The position of A and B peaks is lo towards the direct excitonic transitions, which can be shifted by changing the num layers.…”

“…However, there is no article addressing the synthesis of MoS 2 QDs in cryogenic media. The presence of LN 2 as a monolayer 2D fluid during the synthesis of MoS 2 and graphene oxide via the PLA method facilitates the rapid cooling of the laser-induced plasma [21,22]. Moreover, the optimum and easy conditions for in-situ doping nitrogen in nanostructures provide better results than other methods involving the expensive facilities and complex processes [23,24].…”

“…The materials' electronic features, catalytic activity, and the intrinsic conductivity are improved after the N doping [26][27][28][29][30]. Recently, we obtained the N-MoS 2 nanosheets (NSs) utilizing the PLA in a LN 2 medium, demonstrating its properties as p-type semiconductor [22]. On the other hand, H 2 as a combustion product benefits from high energy density and zero effect on the environment.…”