As one unique group of two-dimensional (2D) nanomaterials, 2D metal nanomaterials have drawn increasing attention owing to their intriguing physiochemical properties and broad range of promising ...applications. In this Review, we briefly introduce the general synthetic strategies applied to 2D metal nanomaterials, followed by describing in detail the various synthetic methods classified in two categories, i.e. bottom-up methods and top-down methods. After introducing the unique physical and chemical properties of 2D metal nanomaterials, the potential applications of 2D metal nanomaterials in catalysis, surface enhanced Raman scattering, sensing, bioimaging, solar cells, and photothermal therapy are discussed in detail. Finally, the challenges and opportunities in this promising research area are proposed.
A hollow multishell structure (HoMS) is an assembly of multiple shells with voids between the individual shells. Accessible through nanopores, these voids represent separate reaction environments in ...the same assembly, such that HoMSs have unique properties that are applicable to diverse fields. These applications have mostly exploited the large specific surface area, high loading capacity and/or buffering effect of HoMSs, benefiting the mass/energy transmission and effective surface area. In comparison, the temporal-spatial ordering of reactions, as well as the dynamic smart behaviour of HoMSs, have been less explored but are also emphasized in this Perspective. We first describe the synthesis of HoMSs and the thermodynamic and kinetic aspects of their formation. We then consider the composition and structural functionalization of each shell within a HoMS and then highlight how these enable applications based on temporal-spatial ordering and dynamic smart behaviour.
As a novel two-dimensional (2D) material, graphene shows great benefits in electric and material science. Compared to 1D nanomaterials, it may show more excellent properties. Here, we introduced ...graphene as 2D bridges into the nanocrystalline electrodes of dye-sensitized solar cells, which brought a faster electron transport and a lower recombination, together with a higher light scattering. On the basis of these advantages, the short-circuit current density was increased by 45% without sacrificing the open-circuit voltage, and the total conversion efficiency was 6.97%, which was increased by 39%, comparing with the nanocrystalline titanium dioxide photoanode, and it was also much better than the 1D nanomaterial composite electrode.
Hollow multishelled structures (HoMSs), with relatively isolated cavities and hierarchal pores in the shells, are structurally similar to cells. Functionally inspired by the different transmission ...forms in living cells, we studied the mass transport process in HoMSs in detail. In the present work, after introducing the antibacterial agent methylisothiazolinone (MIT) as model molecules into HoMSs, we discover three sequential release stages, i.e., burst release, sustained release and stimulus-responsive release, in one system. The triple-shelled structure can provide a long sterility period in a bacteria-rich environment that is nearly 8 times longer than that of the pure antimicrobial agent under the same conditions. More importantly, the HoMS system provides a smart responsive release mechanism that can be triggered by environmental changes. All these advantages could be attributed to chemical diffusion- and physical barrier-driven temporally-spatially ordered drug release, providing a route for the design of intelligent nanomaterials.
The chemical structure and electronic properties of two-dimensional (2D) carbon-supported TiO2, TiO2–graphdiyne, and TiO2–graphene composites have been studied by first-principles density functional ...theory. Calculation results show that TiO2(001)–graphdiyne composites possess superior charge separation and oxidation properties, having the longest lifetimes of photoexcited carriers among all of the 2D composites containing TiO2 of different facets. Our experimental results further proved that TiO2(001)–graphdiyne composites could be a promising photocatalyst. For photocatalytic degradation of methylene blue, the rate constant of the TiO2(001)–graphdiyne composite is 1.63 ± 0.15 times that of the pure TiO2(001) and 1.27 ± 0.12 times that of the TiO2(001)–graphene composite.
Hierarchical structures with different length scales, which appear in many animals and plants, play important roles in their structural and functional integrity . These structures endow their host ...animals and plants with intriguing properties including super-hydrophobicity, reversible adhesion as well as mechanical or optical properties.
More than just an empty shell: Multishelled Co3O4 microspheres were synthesized as anode materials for lithium‐ion batteries in high yield and purity. As their porous hollow multishell structure ...guarantees a shorter Li+ diffusion length and sufficient void space to buffer the volume expansion, their rate capacity, cycling performance, and specific capacity were excellent (1615.8 mA h g−1 in the 30th cycle for triple‐shelled Co3O4; see graph).
Similar to heterostructures composed of different materials, possessing unique properties due to the synergistic effect between different components, the crystal‐phase heterostructures, one variety ...of hetero‐phase structures, composed of different crystal phases in monometallic nanomaterials are herein developed, in order to explore crystal‐phase‐based applications. As novel hetero‐phase structures, amorphous/crystalline heterostructures are highly desired, since they often exhibit unique properties, and hold promise in various applications, but these structures have rarely been studied in noble metals. Herein, via a one‐pot wet‐chemical method, a series of amorphous/crystalline hetero‐phase Pd nanosheets is synthesized with different crystallinities for the catalytic 4‐nitrostyrene hydrogenation. The chemoselectivity and activity can be fine‐tuned by controlling the crystallinity of the as‐synthesized Pd nanosheets. This work might pave the way to preparing various hetero‐phase nanostructures for promising applications.
Amorphous/crystalline heterophase Pd nanosheets exhibit crystallinity‐dependent chemoselectivity and catalytic activity.
High-energy-density lithium-sulfur(Li-S) batteries are drawing dramatic research interests to fulfill the ever-increasing demands of electrical vehicles. However, challenges with the insulating ...property of sulfur and its lithiation products and its large volume expansion, and the shuttle effect of lithium polysulfides, hinder the commercial application of Li-S batteries. Lots of material design concepts have been developed to address the failure modes. Among them, hollow micro-/nanostructures with abundant compositional and geometrical feasibility have been proved fruitful in addressing the current obstacles of Li-S batteries. Here, typical examples of designing hollow micro-/nanostructures to address the problems of Li-S batteries and simultaneously improve the practical capacity and lifespan are highlighted. In particular, the great effect of structural engineering on minimizing volume change, inhibiting the shuttle effect and catalyzing polysulfide conversion are discussed systematically. Finally, future directions of hollow nanostructure design to enhance the progress of Li-S batteries are also provided.
The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and ...potential applications. Herein, by elaborately designing and choosing two flexible molecules with C 3v molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA.
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