Responding to the ongoing novel coronavirus (agent of COVID-19) outbreak, China implemented “the largest quarantine in human history” in Wuhan on 23 January 2020. Similar quarantine measures were ...imposed on other Chinese cities within days. Human mobility and relevant production and consumption activities have since decreased significantly. As a likely side effect of this decrease, many regions have recorded significant reductions in air pollution. We employed daily air pollution data and Intracity Migration Index (IMI) data form Baidu between 1 January and 21 March 2020 for 44 cities in northern China to examine whether, how, and to what extent travel restrictions affected air quality. On the basis of this quantitative analysis, we reached the following conclusions: (1) The reduction of air pollution was strongly associated with travel restrictions during this pandemic—on average, the air quality index (AQI) decreased by 7.80%, and five air pollutants (i.e., SO2, PM2.5, PM10, NO2, and CO) decreased by 6.76%, 5.93%, 13.66%, 24.67%, and 4.58%, respectively. (2) Mechanism analysis illustrated that the lockdowns of 44 cities reduced human movements by 69.85%, and a reduction in the AQI, PM2.5, and CO was partially mediated by human mobility, and SO2, PM10, and NO2 were completely mediated. (3) Our findings highlight the importance of understanding the role of green production and consumption.
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•We estimated the effects of the implementation of travel restrictions on air pollution.•We tested human mobility as one potential mechanism underlying this effect.•We utilized long dynamic panel data models using data from 44 cities in north China.•The concentrations of SO2, PM2.5, PM10, NO2, and CO decreased by 6.76%, 5.93%, 13.66%, 24.67%, and 4.58%, respectively.•Human mobility dropped by 69.85% after governments implemented travel bans.
A considerable challenge in the conversion of carbon dioxide into useful fuels comes from the activation of CO2 to CO2.− or other intermediates, which often requires precious‐metal catalysts, high ...overpotentials, and/or electrolyte additives (e.g., ionic liquids). We report a microwave heating strategy for synthesizing a transition‐metal chalcogenide nanostructure that efficiently catalyzes CO2 electroreduction to carbon monoxide (CO). We found that the cadmium sulfide (CdS) nanoneedle arrays exhibit an unprecedented current density of 212 mA cm−2 with 95.5±4.0 % CO Faraday efficiency at −1.2 V versus a reversible hydrogen electrode (RHE; without iR correction). Experimental and computational studies show that the high‐curvature CdS nanostructured catalyst has a pronounced proximity effect which gives rise to large electric field enhancement, which can concentrate alkali‐metal cations resulting in the enhanced CO2 electroreduction efficiency.
The needle has landed: CdS nanostructures with sharp tips can generate large electric fields that lead to increased CO2 concentrations for CO2‐to‐CO conversion. The localized electric fields are significantly enhanced when two nanoneedles are in close proximity. These advantages result in CO2 electrocatalytic reduction with a 95.5±4.0 % CO Faraday efficiency.
Multiresponsive flexile sensors with strain, temperature, humidity, and other sensing abilities serving as real electronic skin (e‐skin) have manifested great application potential in flexible ...electronics, artificial intelligence (AI), and Internet of Things (IoT). Although numerous flexible sensors with sole sensing function have already been reported since the concept of e‐skin, that mimics the sensing features of human skin, was proposed about a decade ago, the ones with more sensing capacities as new emergences are urgently demanded. However, highly integrated and highly sensitive flexible sensors with multiresponsive functions are becoming a big thrust for the detection of human body motions, physiological signals (e.g., skin temperature, blood pressure, electrocardiograms (ECG), electromyograms (EMG), sweat, etc.) and environmental stimuli (e.g., light, magnetic field, volatile organic compounds (VOCs)), which are vital to real‐time and all‐round human health monitoring and management. Herein, this review summarizes the design, manufacturing, and application of multiresponsive flexible sensors and presents the future challenges of fabricating these sensors for the next‐generation e‐skin and wearable electronics.
Multiresponsive flexible sensors susceptible to various stimuli including strain, temperature, humidity, etc., have been rapidly emerging due to their great potential application in e‐skins. Thus, the recent progress of multiresponsive flexible sensors including the design strategies (the choices of sensing materials and mechanisms, and structure designs and fabrication methods), applications and prospects is reviewed to promote further development of e‐skins.
Pyroptosis is a form of regulated cell death mediated by gasdermin family members, among which the function of GSDMC has not been clearly described. Herein, we demonstrate that the metabolite ...α-ketoglutarate (α-KG) induces pyroptosis through caspase-8-mediated cleavage of GSDMC. Treatment with DM-αKG, a cell-permeable derivative of α-KG, elevates ROS levels, which leads to oxidation of the plasma membrane-localized death receptor DR6. Oxidation of DR6 triggers its endocytosis, and then recruits both pro-caspase-8 and GSDMC to a DR6 receptosome through protein-protein interactions. The DR6 receptosome herein provides a platform for the cleavage of GSDMC by active caspase-8, thereby leading to pyroptosis. Moreover, this α-KG-induced pyroptosis could inhibit tumor growth and metastasis in mouse models. Interestingly, the efficiency of α-KG in inducing pyroptosis relies on an acidic environment in which α-KG is reduced by MDH1 and converted to L-2HG that further boosts ROS levels. Treatment with lactic acid, the end product of glycolysis, builds an improved acidic environment to facilitate more production of L-2HG, which makes the originally pyroptosis-resistant cancer cells more susceptible to α-KG-induced pyroptosis. This study not only illustrates a pyroptotic pathway linked with metabolites but also identifies an unreported principal axis extending from ROS-initiated DR6 endocytosis to caspase-8-mediated cleavage of GSDMC for potential clinical application in tumor therapy.
Hybrid graphene aerogels (HGA) consisting of graphene oxide (GO) and graphene nanoplatelets (GNP) were prepared and introduced into polyethylene glycol (PEG) via vacuum impregnation, aiming at ...obtaining composite phase change materials (PCMs) with high thermal conductivity, outstanding shape-stabilization, high energy storage density, commendable thermal repeatability and the ability to light-to-heat energy storage. GO nanosheets formed a three-dimensional supporting network to keep the shape of PEG stable during phase change and GNP dispersed uniformity along the network structure of GO and thus a thermal conductive pathway was constructed. The incorporation of HGA remarkably enhanced the thermal conductivity and shape-stabilization of the composite PCMs. The PEG/HGA composite PCM with only ca. 0.45 wt% GO and ca. 1.8 wt% GNP, showed an enhanced thermal conductivity of 1.43 W/mK from 0.31 W/mK of pure PEG and an improvement of 361%, much higher than the improvement that can be achieved by solution or melt blending. Moreover, an energy conversion from light to heat was realized with the composite PCMs. Thus, this work provides a simple, green and environmentally friendly way to achieve simultaneous enhancement of the thermal conductivity, energy storage density and shape-stabilization of PCMs and realize light-to-thermal energy conversion.
As a renewable and environment-friendly technology for seawater desalination and wastewater purification, solar energy triggered steam generation is attractive to address the long-standing global ...water scarcity issues. However, practical utilization of solar energy for steam generation is severely restricted by the complex synthesis, low energy conversion efficiency, insufficient solar spectrum absorption and water extraction capability of state-of-the-art technologies. Here, for the first time, we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine (PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability (≈ 96% in a wide solar spectrum range of 250–1,500 nm wavelength). Moreover, such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA, as well as the interspacing between core-shell microspheres. The solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2% and 93.6%, respectively. Besides, the PDA@MXene photothermal layer renders the system durable mechanical properties, allowing producing clean water from seawater with the salt rejection rate beyond 99%. Furthermore, stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of MXene. Therefore, this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.
Conductive elastomeric materials of multi-walled carbon nanotube (MWCNT) filled thermoplastic vulcanizate (TPV) based on polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) blends were ...fabricated via different processing procedures, i.e., one-step and two-step methods, to control strain sensitivity aiming at applications from strain sensors to stretchable conductors. The phase size of cross-linked EPDM could be effectively tuned and the average diameter of EPDM particles was 550 nm for one-step TPV and 230 μm for two-step TPV. Uniform dispersion of MWCNTs in two-step TPV and serious aggregations of MWCNTs in one-step TPV were observed. Both TPVs showed excellent strain-resistance repeatability for 50 tensile and recovery cycles. The one-step-TPV showed a potential to be used as strain sensor due to a high gauge factor (GF) of 1004 at a strain of 100%, while the resistance for the two-step TPV composite was independent with strain even at a strain of 200%, resulting in a stretchable conductor with excellent resistance memory effect. The different strain sensitivity can be explained by the orientation of PP matrix. Moreover, the two-step TPV showed much lower electrical conductivity percolation threshold, 0.65 wt.%. This work provided a simple route to tune the strain sensitivity of MWCNTs filled TPVs based on PP/EPDM blends for applications from strain sensors to highly stretchable conductor through different processing procedures to control the morphologies and MWCNT dispersion.
Piezoelectric film pressure sensors are forthcoming choices for self-powered flexible and portable electronics because of their unique advantages in instant response and linear pressure-electrical ...signal relationship. However, it is commonly of challenge to achieve high output voltage response to pressure in piezoelectric polymer films. Here, we report a piezoelectric film pressure sensor fabricated by electrospun polyvinylidene-fluoride-trifluoroethylene (PVDF-TrFE)/MXene nanofiber mats. As a new two-dimensional nanomaterial, MXene has not only a large amount of surface functional groups to enable interaction with the dipoles of PVDF-TrFE molecular chains, but also high electrical conductivity to potentially increase the polarization of PVDF-TrFE during electrospinning. As such, by comparison with the control pressure sensor consisting of neat PVDF-TrFE film, the composite film sensor shows significantly improved output voltage, and the improvements are closely dependent on MXene content. For instance, the composite film with 2.0 wt% MXene can achieve an instantaneous output power density of ~3.64 mW/m2 under the pressure of 20 N with the frequency of 1 Hz. Such piezoelectric PVDF-TrFE/MXene films are capable of sensing body motion for healthcare. Furthermore, the hydrophilicity of MXene allows the film pressure sensor to monitor humidity change, thus the composite film sensor demonstrates potential application in multifunctional electronic skins.
The electrospun PVDF-TrFE/MXene composite film with good piezoelectric properties shows a good linear pressure-electrical signal response and ability of sensing human daily activities. Display omitted
Cyclic polymers attract attention because of their endless structure and unique properties, which differ from the linear analogs. However, the synthesis of cyclic polymers is difficult and prohibits ...their functions and applications. In this study, we reported chiral cyclic PdII‐catalysts that initiate a living ring‐expansion polymerization of isocyanides, yielding a single‐handed cyclic‐helical poly(phenyl isocyanide), with predictable molecular weight (Mn) and low dispersity (Mw/Mn), in good yield. Using this method, cyclic bottlebrush polymers were prepared via the grafting‐onto strategy. The cyclic topology was confirmed using various spectroscopic data and atomic force microscope observation. Moreover, the cyclic polymer brushes, comprising of a one‐handed helical backbone, showed interesting photoluminescence and circularly‐polarized luminescence.
A family of chirally cyclic PdII catalysts were developed that initiated a living ring‐expansion polymerization of isocyanides, providing cyclic polymers with precise molecular weight and low dispersity. Owing to the single‐handed helical backbone, these polymers showed interesting circularly polarized luminescence with tuneable handedness and dissymmetric factor.
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