2D Zinc Oxide - Synthesis, Methodologies, Reaction Mechanism, and Applications.

Zinc oxide (ZnO) is a thermally stable n-type semiconducting material. ZnO 2D nanosheets have mainly gained substantial attention due to their unique properties, such as direct bandgap and strong excitonic binding energy at room temperature. These are widely utilized in piezotronics, energy storage, photodetectors, light-emitting diodes, solar cells, gas sensors, and photocatalysis. Notably, the chemical properties and performances of ZnO nanosheets largely depend on the nano-structuring that can be regulated and controlled through modulating synthetic strategies. Two synthetic approaches, top-down and bottom-up, are mainly employed for preparing ZnO 2D nanomaterials. However, owing to better results in producing defect-free nanostructures, homogenous chemical composition, etc., the bottom-up approach is extensively used compared to the top-down method for preparing ZnO 2D nanosheets. This review presents a comprehensive study on designing and developing 2D ZnO nanomaterials, followed by accenting its potential applications. To begin with, various synthetic strategies and attributes of ZnO 2D nanosheets are discussed, followed by focusing on methodologies and reaction mechanisms. Then, their deliberation toward batteries, supercapacitors, electronics/optoelectronics, photocatalysis, sensing, and piezoelectronic platforms are further discussed. Finally, the challenges and future opportunities are featured based on its current development.

Organosilane with Gemini-Type Structure as the Mesoporogen for the Synthesis of the Hierarchical Porous ZSM-5 Zeolite.

A new kind of organosilane (1,6-bis(diethyl(3-trimethoxysilylpropyl)ammonium) hexane bromide) with a gemini-type structure was prepared and used as a mesoporogen for the synthesis of hierarchical porous ZSM-5 zeolite. There are two quaternary ammonium centers along with double-hydrolyzable -RSi(OMe)3 fragments in the organosilane, which results in a strong interaction between this mesoporogen and silica-alumina gel. The organosilane can be easily incorporated into the ZSM-5 zeolite structure during the crystallization process, and it was finally removed by calcination, leading to secondary pores in ZSM-5. The synthesized ZSM-5 has been systematically studied by XRD, nitrogen adsorption, SEM, TEM, TG, and solid-state one-dimensional (1D) and two-dimensional (2D) NMR, which reveal information on its detailed structure. It has a hierarchical porosity system, which combines the intrinsic micropores coming from the crystalline structure and irregular mesopores created by the organosilane template. Moreover, the mesoposity including pore size and volume within ZSM-5 can be systematically tuned by changing the organosilane/TEOS ratio, which confirms that this organosilane has high flexibility of use as a template for the synthesis of hierarchical porous zeolite.

Agri-waste derived electroactive carbon-iron oxide nanocomposite for oxygen reduction reaction: an experimental and theoretical study.

Herein, we have utilized agri-waste and amalgamating low Fe3+, to develop an economic iron oxide-carbon hybrid-based electrocatalyst for oxygen reduction reaction (ORR) with water as a main product following close to 4e- transfer process. The electrocatalytic activity is justified by electrochemical active surface area, synergetic effect, and density functional theory calculations.

Feasibility of brackish water and landfill leachate treatment by GO/MoS2-PVA composite membranes.

Two-dimensional (2D) based layered materials with tunable chemical functionalities and surface charge properties have emerged for on-demand applications including membrane technology. However, the process control, time and energy-efficient production of non-swelling graphene oxide (GO) with retaining physicochemical properties are still challenging. In this work, we have fabricated highly ordered GO membrane on cellulose acetate supporting membrane filters of 1.2 µm pore size using molybdenum disulphide (MoS2) as a nano-spacer and polyvinyl alcohol (PVA) as an adhesive for the first time with limited swelling. The fabricated membranes were used for NaCl rejection and removal of toxic heavy metal ions, and the radioactive element from landfill leachate water. The introduction of hydrophilic PVA, thickness control using a various amount of nanospacer and graphene oxide played a vital role in the transport mechanism, permeability, and selectivity index. The composition of PVA and MoS2 in the coating solution was optimized to tune the d-spacing of graphene oxide layers. The newly developed composite membranes have 89% rejection rate to NaCl and 3.96 L/m2h water flux at low operating pressures of 5 bar. Also, the prepared membranes have a high rejection of multivalent metal ions in landfill leachate. 86.5% to 99.8% rejection rate of multivalent metal ions in landfill leachate was observed for the M3 (GO (10): MoS2 (10): PVA (0.5)) membrane. The excellent rejection performance is ascribed to the combined impact of size exclusion, ion adsorption, electrostatic interaction and Gibbs-Donnan exclusion mechanism. The excellent stability and high rejection rate even after 216 h of operation make the fabricated membranes promising for use in practical water separation applications.

Surface Composition of Silver Nanocubes and Their Influence on Morphological Stabilization and Catalytic Performance in Ethylene Epoxidation.

Silver nanocubes with exposed (100) facets are reported to have improved selectivity with respect to their spherical counterparts for ethylene epoxidation. In the present study, we observe that the surface composition of the silver nanocubes also has a critical impact on activity. Detailed investigation of the surface composition of silver nanocubes has been carried out using HRTEM, SEM, EDS, EELS, and EFTEM. Surfaces of silver nanocubes are "passivated" by chloride, and its removal is essential to achieve any catalytic activity. However, the surface chloride is apparently essential for stabilizing the cubic morphology of the particles. Attempts were made to understand the competing effects of the surface species for retaining the morphology of the nanocubes and on their catalytic activity in ethylene epoxidation.