Controlling for the polarity and subjectivity of social media data based on the development of the COVID-19 outbreak, we analyse the relationships between the largest cryptocurrencies and such ...time-varying realisation as to the scale of the economic shock centralised within the rapidly-escalating pandemic. We find evidence of significant growth in both returns and volumes traded, indicating that large cryptocurrencies acted as a store of value during this period of exceptional financial market stress. Further, cryptocurrency returns are found to be significantly influenced by negative sentiment relating to COVID-19. While not only providing diversification benefits for investors, results suggest that these digital assets acted as a safe-haven similar to that of precious metals during historiccrises.
•The role of cryptocurrency as a safe-haven during the COVID-19 pandemic is examined.•We find evidence of significant growth in both returns and volumes traded.•Significant and pronounced time-varying price-volatility effects are identified.•Returns are found to be significantly influenced by negative COVID-19 sentiment.•Safe-haven effects are identified providing evidence of further product maturity.
Realization of a highly sensitive analysis and sensing platform is important for early-stage tumor diagnosis. In this work, a self-powered biosensor with a novel sandwich graphdiyne (SGDY) combined ...with an aptamer-specific recognition function was developed to sensitively and accurately detect tumor markers. Results indicated that the detection limits of microRNA (miRNA)-21 and miRNA-141 were 0.15 and 0.30 fM (S/N = 3) in the linear range of 0.05–10000 and 1–10000 fM, respectively. The newly designed platform has great promise for early-stage tumor diagnosis.
The rapid development of portable/wearable electronics proposes new demands for energy storage devices, which are flexibility, smart functions and long-time outdoor operation. Supercapacitors (SCs) ...show great potential in portable/wearable applications, and the recently developed flexible, smart and self-sustainable supercapacitors greatly meet the above demands. In these supercapacitors, conductive polymers (CPs) are widely applied due to their high flexibility, conductivity, pseudo-capacitance, smart characteristics and moderate preparation conditions. Herein, we'd like to introduce the CP-based flexible, smart and self-sustainable supercapacitors for portable/wearable electronics. This review first summarizes the flexible SCs based on CPs and their composites with carbon materials and metal compounds. The smart supercapacitors,
i.e.
, electrochromic, electrochemical actuated, stretchable, self-healing and stimuli-sensitive ones, are then presented. The self-sustainable SCs which integrate SC units with energy-harvesting units in one compact configuration are also introduced. The last section highlights some current challenges and future perspectives of this thriving field.
Progress of utilizing conductive polymers and their composites to prepare flexible, smart and self-sustainable supercapacitors for portable/wearable electronics is reviewed.
Significant “breathing effect” calls for exploring efficient strategies to address the intrinsic issues of silicon anode of lithium-ion batteries (LIBs). We here report a controllable synthetic route ...to fabricate the silicon–carbon hybrids, in which porous silicon nanoparticles (p-SiNPs) are loaded in void carbon spheres by forming the yolk–shell p-SiNPs@hollow carbon (HC) nanohybrids tunable. A set of controlled experiments accompanying with systematic characterizations demonstrate that the void space and mass loading of Si can be adjusted in an effective way so that the nanostructure can be optimized with achieving improved electrochemical performance as anode of lithium-ion batteries (LIBs). The optimized p-SiNPs@HC nanohybrids show excellent performance as anode for Li-ion battery, delivering a capacity of more than 1400 mA h g–1 after 100 cycles at 0.2 A g–1 and 720 mA h g–1 at a high current density of 4 A g–1. The present work may provide us with an attractive and promising strategy for advancing Si-based anode materials due to advantages of tunable structure of silicon–carbon nanohybrids for optimizing electrochemical performance.
We report the design, synthesis, and characterization of a novel heterojunction array of α-Fe(2)O(3)/graphene/BiV(1-x)Mo(x)O(4) core/shell nanorod for photoelectrochemical water splitting. The ...heterojunction array was prepared by hydrothermal deposition of α-Fe(2)O(3) nanorods onto Ti substrate, with subsequent coating of graphene interlayer and BiV(1-x)Mo(x)O(4) shell by photocatalytic reduction and a spin-coating approach, respectively. The heterojunction yielded a pronounced photocurrent density of ∼1.97 mA/cm(2) at 1.0 V vs Ag/AgCl and a high photoconversion efficiency of ∼0.53% at -0.04 V vs Ag/AgCl under the irradiation of a Xe lamp. The improved photoelectrochemical properties benefited from (1) the enhanced light absorption due to behavior of the "window effect" between the α-Fe(2)O(3) cores and BiV(1-x)Mo(x)O(4) shells, and (2) the improved separation of photogenerated carriers at the α-Fe(2)O(3) nanorod/graphene/BiV(1-x)Mo(x)O(4) interfaces. Our results demonstrate the advantages of the novel graphene-mediated core/shell heterojunction array and provide a valuable insight for the further development of such materials.
The COVID-19 pandemic presented a dynamic black-swan event to which governments implemented support programmes to reduce sectoral probability of default. This research analyses investor response to ...such assistance, designed to mitigate the effects of the pandemic upon international aviation and tourism. Investor confidence in such support schemes is estimated through short-term abnormal returns. Results indicate significant differential behaviour, with fiscal policy found to be a dominant and largely effective mechanism generating median abnormal returns of 2.17 %. Specific assistance programmes relating to COVID-19 loan facilities, and the provision of pandemic relief packages significantly alleviated short-term investor concerns with median abnormal returns estimated between 2.87 % and 3.89 % respectively. Our empirical results offer investors and policymakers an additional layer of information.
•We analyse investor response to COVID-19 aviation and tourism assistance packages•Investor confidence in such support schemes is estimated through abnormal returns•Results indicate significant differential behaviour•COVID-19 loan facilities and relief packages generate the most significant response•Our empirical results offer investors and policy-makers an additional layer of information
We report a high-performance bi-functional electrocatalyst composed of 3D crumpled graphene (CG)-cobalt oxide nanohybrids. This is the first report on using CG coupled with nanocrystals as both ...oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts. The nitrogen-doped CG-CoO hybrid exhibits excellent catalytic activity and durability, making it a high-performance non-precious metal-based bi-functional catalyst for both ORR and OER.
This paper examines volatility and skewness spillover between Chinese stock index and index futures markets during the market crash in 2015. The results reveal that the volatility spillover from ...futures to spot is significant and stronger than the other way around and the transmission of downside risk is bilateral with the futures market taking the lead. Moreover, the measures announced during the market crash to curb the speculative futures trading appears to enhance the spillover of both volatility and skewness from futures to spot markets. This paper thus sheds some light on the validity of such measures to restore market efficiency during a stock market crash.
Developing photoanodes with efficient sunlight harvesting, excellent charge separation and transfer, and fast surface reaction kinetics remains a key challenge in photoelectrochemical water splitting ...devices. Here we report a new strongly coupled ternary hybrid aerogel that is designed and constructed by in situ assembly of N-deficient porous carbon nitride nanosheets and NiFe-layered double hydroxide into a 3D N-doped graphene framework architecture using a facile hydrothermal method. Such a 3D hierarchical structure combines several advantageous features, including effective light-trapping, multidimensional electron transport pathways, short charge transport time and distance, strong coupling effect, and improved surface reaction kinetics. Benefiting from the desirable nanostructure, the ternary hybrid aerogels exhibited remarkable photoelectrochemical performance for water oxidation. Results included a record-high photocurrent density that reached 162.3 μA cm–2 at 1.4 V versus the reversible hydrogen electrode with a maximum incident photon-to-current efficiency of 2.5% at 350 nm under AM 1.5G irradiation, and remarkable photostability. The work represents a significant step toward the development of novel 3D aerogel-based photoanodes for solar water splitting.
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