Two-dimensional (2D) Janus materials with opposing components and properties on two sides have recently attracted fevered attention from various research fields for use as, for example, oil/water separating membranes, interfacial layers for mass transfer, 2D sensors and actuators. The Janus structure allows for a unidirectional transportation system and programmed response to certain stimuli to be achieved. Graphene, the 2D honeycomb network formed from one atomic layer of carbon atoms, has also received substantial research interest because of its intriguing structure and fascinating properties. The high mechanical strength, flexibility and optical transparency make graphene a unique candidate as a building block of 2D Janus materials through asymmetric modification with different functional groups on the graphene surfaces. This article reviews graphene-based 2D Janus materials, starting with a theoretical understanding of the behavior of Janus graphene. Then, different strategies for fabricating Janus graphene and its derivatives are reviewed in detail according to the chemical strategies of the modification methods. The applications of graphene-based Janus materials are discussed with a specific focus on the Janus structures that lead to bandgap engineering, as well as the construction of a responsive system on graphene.
High‐performance supercapacitors (SCs) are important energy storage components for emerging wearable electronics. Rendering low‐temperature foldability to SCs is critically important when wearable devices are used in a cold environment. However, currently reported foldable SCs do not have a stable electrochemical performance at subzero temperatures, while those that are performing are not foldable. Herein, a freestanding pure‐carbon‐based porous electrode, namely, lamellar porous carbon stack (LPCS), is reported, which enables stable low‐temperature‐foldable SCs. The LPCS, which is fabricated with a simple vacuum filtration of a mixture of carbon fibers (CFs), holey reduced graphene oxides (HRGOs), and carbon nanotubes (CNTs), possesses a lamellar stacking of porous carbon thin sheets, in which the CFs act as the skeleton and the HRGOs and CNTs act as binders. The unique structure leads to excellent compression resilience, high foldability, and high electronic and ionic conductivity. SCs made with the LPCS electrodes and ionic liquid electrolyte show a high energy density (2.1 mWh cm−2 at 2 mA cm−2), low‐temperature long lifetime (95% capacity after 10 000 cycles at −30 °C), and excellent low‐temperature foldability (86% capacity after 1000 folding cycles at −30 °C).
The two families of Ru -chromene and -chromone complexes isolated in this work represent the first examples of metalated chromene and chromone complexes synthesized through transition-metal-mediated cyclization of phenol-tethered ynone. These unprecedented metalated heterocyclic compounds exhibit remarkable features, such as pH-switchable metal-carbon bonding interactions, photo-triggerable release of organic chromone upon visible-light irradiation, and superior antioxidative property to their organic analogue (1,4-benzopyrone). These findings not only offer mechanistic insights into metal-induced activation of functionalized alkynes, but also add a new dimension to rational design of antioxidants and photo-responsive drug delivery systems.
Metallafuran complexes with a fused five‐membered phosphonium ring were synthesized from reactions between terminal ynones HC≡C(C=O)R and cis‐[Ru/Os(dppm)2Cl2] (dppm=1,1‐bis(diphenylphosphino)methane). A metal–vinylidene‐involving pathway was found to be an energetically feasible formation mechanism for these complexes. These phosphonium‐containing metallafurans, like many phosphonium‐functionalized drugs, have the ability to induce mitochondrial dysfunction. They also exhibit stronger cytotoxicity against several human cancer cell lines in comparison with their metal precursors and the classic anticancer drug cisplatin. Overall, this work provides structural and mechanistic insights for the rational design of functional metallacycles via activation of alkynes by RuII and OsII centers.
The two series of ruthenium-indolizinone complexes prepared by Ru-mediated cyclization of pyridine-tethered alkynes represent the first examples of metalated indolizinone complexes. Joint experimental-theoretical investigation suggests an unconventional 5-endo-dig cyclization pathway as their formation mechanism. They also exhibit moderate cytotoxicity against several human cancer cell lines.
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