Plasma Processing and Treatment of 2D Transition Metal Dichalcogenides: Tuning Properties and Defect Engineering.

Two-dimensional transition metal dichalcogenides (TMDs) offer fascinating opportunities for fundamental nanoscale science and various technological applications. They are a promising platform for next generation optoelectronics and energy harvesting devices due to their exceptional characteristics at the nanoscale, such as tunable bandgap and strong light-matter interactions. The performance of TMD-based devices is mainly governed by the structure, composition, size, defects, and the state of their interfaces. Many properties of TMDs are influenced by the method of synthesis so numerous studies have focused on processing high-quality TMDs with controlled physicochemical properties. Plasma-based methods are cost-effective, well controllable, and scalable techniques that have recently attracted researchers' interest in the synthesis and modification of 2D TMDs. TMDs' reactivity toward plasma offers numerous opportunities to modify the surface of TMDs, including functionalization, defect engineering, doping, oxidation, phase engineering, etching, healing, morphological changes, and altering the surface energy. Here we comprehensively review all roles of plasma in the realm of TMDs. The fundamental science behind plasma processing and modification of TMDs and their applications in different fields are presented and discussed. Future perspectives and challenges are highlighted to demonstrate the prominence of TMDs and the importance of surface engineering in next-generation optoelectronic applications.

A hydrophilic carbon foam/molybdenum disulfide composite as a self-floating solar evaporator.

Solar-driven interfacial evaporation has gained increasing attention as an emerging and sustainable technology for wastewater treatment and desalinization. The carbon/molybdenum disulfide (C/MoS2) composite has attracted more attention due to its outstanding light absorption capability and optoelectronic properties as a solar steam generator. However, the hydrophobic nature of carbon and MoS2-based materials hinders their wettability, which is crucial to the effective and facile operation of a solar generator of steam. Herein, a pH-controlled hydrothermal method was utilized to deposit a promising photothermal MoS2 coating on melamine-derived carbon foams (CFs). The hydrophilic CF/MoS2 composite, which can easily be floatable on the water surface, is a high-efficiency solar steam evaporator with a rapid increase in temperature under photon irradiation. Due to the localized heat confinement effect, the self-floating composite foam on the surface of water has the potential to produce a significant temperature differential. The porous structure effectively facilitates fast water vapor escape, leading to an impressively high evaporation efficiency of 94.5% under a light intensity of 1000 W m-2.

Graphene/silver-based composites and coating on dead coral for degradation of organic pollution using the Z-scheme mechanism.

A high-performance photocatalytic nanocomposite consisting of silver phosphate-based particles with GO and RGO was synthesized by co-precipitation and hydrothermal methods. Ag3PO4 was prepared by a co-precipitation method. The as-prepared Ag3PO4 nanocomposites were characterized by different analyses. The results demonstrated that the Ag3PO4 particles were well dispersed on the graphene-based surfaces. The photocatalytic performance of the GO/RGO/Ag3PO4 nanocomposite was evaluated for the photodegradation of methylene blue (MB) under exposure to visible light (xenon lamp λ > 400 nm). The degradation rate was about 98% in 5 min. The enhancement in photocatalytic performance is attributed to the simultaneous presence of RGO and GO, which show significantly high absorption of organic molecules on the surface of GO/RGO, allowing the effective transfer and separation of photogenerated electrons. In addition, this modified structure can be in situ synthesized on dead coral structures that can be used in future real case-studies of the degradation of other organic pollutants. The ingredient of these composites, however, is about 93% Ag3PO4.

Core-Double-Shell Fe2O3@SiO2@Jarosite Hybrid Nanoparticles Synthesized by Laser Ablation of Turquoise in Ethanol.

This work highlights a facile green route for the one-step synthesis of iron oxide core-double-shell nanoparticles (NPs) and aluminum phosphide (AlP) nanosheets by pulsed laser ablation of the mineral turquoise target from Nishapur in the presence of an ethanol solvent. High-resolution transmission electron microscopy, selected-area electron diffraction pattern, and field emission scanning electron microscopy (FESEM) in combination with energy-dispersive X-ray mapping revealed the formation of NPs with a typical core@double-shell structure in which crystalline α-Fe2O3 (iron oxide) formed the core, while SiO2 (quartz) and (K, H3O)Fe3(SO4)2(OH6) (jarosite) participated as the inner and outer shell, respectively. However, the application of laser ablation on the turquoise phase of the target led to the formation of AlP nanosheets which was confirmed by the X-ray diffraction patterns and FESEM images. Strong absorption of the vein-ablated species in the UV region (250-360 nm) was the characteristic feature of α-Fe2O3 and jarosite phases, while the absorption band at 250-300 nm for the turquoise-ablated species was related to the presence of Cu compound species and also the α-Fe2O3 phase in the sample. Photoluminescence emission spectra for the vein-ablated species depicted a peak centered at 370 nm, while a peak located at 364 nm was ascribed to the turquoise-ablated species. In particular, these hybrid NPs with high purity and stability may offer new opportunities for bio-applications such as anticancer agents and water/wastewater applications.

Mechanochemical Green Synthesis of Exfoliated Edge-Functionalized Boron Nitride Quantum Dots: Application to Vitamin C Sensing through Hybridization with Gold Electrodes.

Two-dimensional boron nitride quantum dots (2D BNQDs) with excellent chemical stability, high photoluminescence efficiency, and low toxicity are a new class of advanced materials for biosensing and bioimaging applications. To overcome the current challenge about the lack of facile, scalable, and reproducible synthesis approach of BNQDs, we introduce a green and facile approach based on mechanochemical exfoliation of bulk h-BN particles in ethanol. Few-layered hydroxylated-functionalized QDs with a thickness of 1-2 nm and a lateral dimension of 2-6 nm have been prepared. The synthesized nanocrystals exhibit a strong fluorescence emission at 407 and 425 nm with a quantum efficiency of ∼6.2%. Spectroscopic analyses determine that interactions between oxygen groups of the solvent with boron sites occur, which along with the mechanical forces, lead to efficient exfoliation of the hexagonal structure and surface functionalization with -OH groups. We also demonstrate that the orbital interaction between BNQDs and the gold surface results in a profound electrochemical catalytic activity toward oxidation of vitamin C. It is shown that the BNQD-modified screen-printed gold electrode exhibits a decreased onset oxidation potential for about 0.37 V/AgCl. In addition to high catalytic activity, electrochemical studies also reveal that this electrode allows selective and sensitive detection of vitamin C with a good response over a wide range from 0.80 µM to 5.0 mM with a detection limit of 0.45 µM (S/N = 3) and a sensitivity of 1.3 µA µM-1 cm-2. Finally, the potential application of the hybrid sensor for detecting vitamin C in commercial drinks is demonstrated.