The preparation of ultralight, superelastic and multifunctional graphene aerogels still remains a challenge. Herein we develop a silane-crosslinked and modified graphene aerogel (SGA) using a novel ...and simple method of chemical vapor deposition of methyltriethoxysilane into graphene oxide aerogels. The SGA is mechanically robust and shows fantastic properties satisfying multiple applications. Firstly, the SGA exhibits hitherto the highest compression recoverability (99.5%), as well as a high energy loss coefficient and cycle stability. Secondly, the compressible and ultralight (minimum density of 0.35 mg cm −3 ) SGA could serve as a fast and recyclable superadsorbent being able to adsorb various organic liquids with ultrahigh capacity (>1000 g g −1 ), which is almost the highest value among known adsorbents. Moreover, the electrical resistance of SGA is highly sensitive to compressive strain and applied pressure due to the enhanced connection between adjacent graphene sheets, which makes the SGA a great pressure sensor with high sensitivity (−67.1 kPa −1 ) and a low detection limit (<30 Pa); the SGA demonstrates great potential in real-time monitoring of subtle actions like the beat of water droplets. Therefore, the flyweight and mechanically robust SGA holds fantastic properties and great potential in multiple applications.
A review is presented on catalysis in water, ionic liquids, supercritical CO
2 and fluorous solvents, highlighting the progress made in the past few years.
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Solvents play a critical role in ...“greening” synthetic chemistry, and this is also true in catalytic organic synthesis. This review attempts to summarize the progress made in the past a few years on homogeneous and heterogeneous catalytic reactions in the non-conventional solvents, water, ionic liquids, supercritical carbon dioxide and fluorous carbons, with the focus on those catalyzed by transition metal complexes. The reactions covered include hydrogenation, hydroformylation, carbonylation, Heck reactions, Suzuki and Stille couplings, Sonogashira reactions, allylic substitution, olefin metathesis, olefin epoxidation and alcohol oxidation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
Flexible pressure sensors have attracted considerable attention because of their potential applications in healthcare monitoring and human–machine interactions. However, the complicated fabrication ...process and the cos of sensing materials limit their widespread applications in practice. Herein, a flexible pressure sensor with outstanding performances is presented through an extremely simple and cost-efficient fabrication process. The sensing materials of the sensor are based on low-cost carbon black (CB)@airlaid paper (AP) composites, which are just prepared by drop-casting CB solutions onto APs. Through simply stacking multiple CB@APs with an irregular surface and a fiber-network structure, the obtained pressure sensor demonstrates an ultrahigh sensitivity of 51.23 kPa–1 and an ultralow detection limit of 1 Pa. Additionally, the sensor exhibits fast response time, wide working range, good stability, as well as excellent flexibility and biocompatibility. All the comprehensive and superior performances endow the sensor with abilities to precisely detect weak air flow, wrist pulse, phonation, and wrist bending in real time. In addition, an array electronic skin integrated with multiple CB@AP sensors has been designed to identify spatial pressure distribution and pressure magnitude. Through a biomimetic structure inspired by blooming flowers, a sensor with the open-petal structure has been designed to recognize the wind direction. Therefore, our study, which demonstrates a flexible pressure sensor with low cost, simple preparation, and superior performances, will open up for the exploration of cost-efficient pressure sensors in wearable devices.
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Electronic skin (e-skin) mimicking functionalities and mechanical properties of natural skin can find broad applications. We report the first dynamic covalent thermoset-based e-skin, which is ...connected through robust covalent bonds, rendering the resulting devices good chemical and thermal stability at service condition. By doping the dynamic covalent thermoset with conductive silver nanoparticles, we demonstrate a robust yet rehealable, fully recyclable, and malleable e-skin. Tactile, temperature, flow, and humidity sensing capabilities are realized. The e-skin can be rehealed when it is damaged and can be fully recycled at room temperature, which has rarely, if at all, been demonstrated for e-skin. After rehealing or recycling, the e-skin regains mechanical and electrical properties comparable to the original e-skin. In addition, malleability enables the e-skin to permanently conform to complex, curved surfaces without introducing excessive interfacial stresses. These properties of the e-skin yield an economical and eco-friendly technology that can find broad applications in robotics, prosthetics, health care, and human-computer interface.
With appropriate stimuli, such as heat, humidity, or magnetic field, shape memory polymers (SMPs) can recover to their original shapes from temporary, programmed states. Using thermal responsive SMPs ...as substrates, we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas. The bilayer system was fabricated by depositing a layer of aluminum thin film on top of a SMP substrate programmed with a tensile strain. After the system was heated by a heating wire, hybrid wrinkling patterns were formed in a confined circular area around the heat source, with an inner spoke pattern and an outer ring pattern. Wrinkling patterns showed good symmetry, and the size of the wrinkling area can be tuned by controlling the heat input. This study offers a simple but effective approach to fabricate hybrid morphological features in micro-scale.
Graphic Abstract
Using thermal responsive SMPs as substrates, we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas. After the system was heated by a heating wire, hybrid wrinkling patterns were formed in a confined circular area around the heat source, with an inner spoke pattern and an outer ring pattern. Wrinkling patterns showed good symmetry, and the size of the wrinkling area can be tuned by controlling the heat input.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Asymmetric transfer hydrogenation has become a practically useful tool in reduction chemistry in the last decade or so. This was largely triggered by the seminal work of Noyori and co-workers in the ...mid-1990s and is driven by its complementing chemistry to hydrogenation employing H(2). This Focus Review attempts to present a "holistic" overview on the advances in the area, focusing on the achievements recorded around the last three years. These include more-efficient and "greener" metal catalysts, catalysts that enable hydrogenation as well as transfer hydrogenation, biomimetic and organocatalysts, and their applications in the reduction of C==O, C==N, and C==C bonds. Also highlighted are efforts in the development of environmentally benign and reusable catalytic systems.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In arthropods, evolution has created a remarkably sophisticated class of imaging systems, with a wide-angle field of view, low aberrations, high acuity to motion and an infinite depth of field. A ...challenge in building digital cameras with the hemispherical, compound apposition layouts of arthropod eyes is that essential design requirements cannot be met with existing planar sensor technologies or conventional optics. Here we present materials, mechanics and integration schemes that afford scalable pathways to working, arthropod-inspired cameras with nearly full hemispherical shapes (about 160 degrees). Their surfaces are densely populated by imaging elements (artificial ommatidia), which are comparable in number (180) to those of the eyes of fire ants (Solenopsis fugax) and bark beetles (Hylastes nigrinus). The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors into integrated sheets that can be elastically transformed from the planar geometries in which they are fabricated to hemispherical shapes for integration into apposition cameras. Our imaging results and quantitative ray-tracing-based simulations illustrate key features of operation. These general strategies seem to be applicable to other compound eye devices, such as those inspired by moths and lacewings (refracting superposition eyes), lobster and shrimp (reflecting superposition eyes), and houseflies (neural superposition eyes).
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Photoactuators have attracted significant interest for soft robot and gripper applications, yet most of them rely on free-space illumination, which requires a line-of-site low-loss optical path. ...While waveguide photoactuators can overcome this limitation, their actuating performances are fundamentally restricted by the nature of standard optical fibres. Herein, we demonstrated miniature photoactuators by embedding optical fibre taper in a polydimethylsiloxane/Au nanorod-graphene oxide photothermal film. The special geometric features of the taper endow the designed photoactuator with microscale active layer thickness, high energy density and optical coupling efficiency. Hence, our photoactuator show large bending angles (>270°), fast response (1.8 s for 180° bending), and low energy consumption (<0.55 mW/°), significantly exceeding the performance of state-of-the-art waveguide photoactuators. As a proof-of-concept study, one-arm and two-arm photoactuator-based soft grippers are demonstrated for capturing/moving small objects, which is challenging for free-space light-driven photoactuators.
Chemical recycling is one of the most promising technologies that could contribute to circular economy targets by providing solutions to plastic waste; however, it is still at an early stage of ...development. In this work, we describe the first light-driven, acid-catalyzed protocol for chemical recycling of polystyrene waste to valuable chemicals under 1 bar of O2. Requiring no photosensitizers and only mild reaction conditions, the protocol is operationally simple and has also been demonstrated in a flow system. Electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculations indicate that singlet oxygen is involved as the reactive oxygen species in this degradation process, which abstracts a hydrogen atom from a tertiary C–H bond, leading to hydroperoxidation and subsequent C–C bond cracking events via a radical process. Notably, our study indicates that an adduct of polystyrene and an acid catalyst might be formed in situ, which could act as a photosensitizer to initiate the formation of singlet oxygen. In addition, the oxidized polystyrene polymer may play a role in the production of singlet oxygen under light.
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