The unique synergistic effect of hierarchical core–shell structures demonstrates great potential for designing the next-generation electrode materials for supercapacitors. In this work, we design ...binder-free MnCo2O4@NiMoO4 heterostructure core–shell nanowire arrays (NWAs) grown over a current collector of nickel foam (NF) achieved through a modified and simple hydrothermal process. The capacitive performance of the core MnCo2O4 NWAs was remarkably improved by growing a layer of NiMoO4 nanosheets (1244 F g−1 at 1 A g−1), which is superior to the capacitance of pristine MnCo2O4 (457.85 F g−1 at 1 A g−1). Moreover, the prepared MnCo2O4@NiMoO4 core–shell NWAs have been used along with commercial activated carbon (AC) to fabricate an asymmetric full supercapacitor device. MnCo2O4@NiMoO4//AC delivers a high energy density (42 W h kg−1) at a power density of 852.3 W kg−1 and a good cyclability with 93% of the initial capacitance retained at the end of 8000 successive charge/discharge cycles. Therefore, the MnCo2O4@NiMoO4 electrode material holds a great promise as a suitable candidate for high performance supercapacitors.
Vertical van der Waals (vdW) heterostructures have shown potential for gas sensing owing to their remarkable sensitivity. However, the optimization process for achieving the best gas sensing ...performance is complicated by the heterostructure's reliance on both physical and electrical characteristics. This study employs density functional theory (DFT) to analyse the structural and electronic parameters of a MoTe2/InN vdW heterostructure. The findings of this study indicate that the vdW heterostructure has a type-II band alignment with higher adsorption energy towards NH3, NO2, and SO2 than the individual monolayers. In specific, the heterostructure is well suited for NO2 detection but has limitations in reliably detecting NH3 and SO2 due to longer recovery times. We find significant hybridization between the adsorbate and interacting surfaces’ orbitals and a notable presence of NO2 molecular orbitals in proximity to the Fermi level. Additionally, dielectric and work function modulations offer a viable means to develop optical-based gas sensors that can selectively detect NO2. Our research provides valuable insights into vdW heterostructure design for high-performance gas sensors.
Highlights
Imine groups in covalent organic framework (COF) films act as dual-active sites for humidity sensing, inducing an intrinsic enhanced mechanism of reversible protonated tautomerism via ...water molecule-induced hydrogen bonding.
The
cis
-ketoimine reciprocal isomerization induces a stretching vibration effect for the ordered conjugated conductive frame of COF films, realizing fast response, wide range, and high sensitivity characteristics for humidity detection.
Resistance changes of COF film-based sensors keep a strong linear relationship with low-range relative humidity, reflecting the quantitative sensing mechanism at the molecular level.
Human metabolite moisture detection is important in health monitoring and non-invasive diagnosis. However, ultra-sensitive quantitative extraction of respiration information in real-time remains a great challenge. Herein, chemiresistors based on imine-linked covalent organic framework (COF) films with dual-active sites are fabricated to address this issue, which demonstrates an amplified humidity-sensing signal performance. By regulation of monomers and functional groups, these COF films can be pre-engineered to achieve high response, wide detection range, fast response, and recovery time. Under the condition of relative humidity ranging from 13 to 98%, the COF
TAPB-DHTA
film-based humidity sensor exhibits outstanding humidity sensing performance with an expanded response value of 390 times. Furthermore, the response values of the COF film-based sensor are highly linear to the relative humidity in the range below 60%, reflecting a quantitative sensing mechanism at the molecular level. Based on the dual-site adsorption of the (–C=N–) and (C–N) stretching vibrations, the reversible tautomerism induced by hydrogen bonding with water molecules is demonstrated to be the main intrinsic mechanism for this effective humidity detection. In addition, the synthesized COF films can be further exploited to effectively detect human nasal and oral breathing as well as fabric permeability, which will inspire novel designs for effective humidity-detection devices.
Mild air calcination endows carbon cloth (CC) with three orders of magnitude increase in specific capacitance. A 2.0 V activated CC based symmetric supercapacitor achieves high volumetric (7.62 mW ...h/cm3) and gravimetric (18.2 Wh/kg) energy densities.
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Commercial carbon clothes have the potential to be utilized as supercapacitor electrodes due to their low cost and high conductivity. However, the negligible surface area of the carbon clothes serves as a serious impediment to their utilization. Herein, we report a facile calcination activation method for carbon cloths to realize remarkable comprehensive electrochemical performance. The activated carbon cloths deliver a high areal capacitance (1700 mF/cm2), good rate capability, and stable cycling performance up to 20,000 cycles. Owing to the stability in the wide potential window, a designed symmetric capacitor can function in a cell voltage of 2.0 V and delivers high volumetric and gravimetric energy densities of 7.62 mWh/cm3 and 18.2 Wh/kg, respectively. The remarkable electrochemical performance is attributed to rich microporosity with high surface area, superior electrolyte wettability, and stability in wide potential window.
The main objective of this study is to empirically examine the impact of REM on various aspects of investment efficiency, including overinvestment and underinvestment. By examining the interplay ...between these complex constructs, this research endeavors to provide deeper insights and contribute to a more comprehensive understanding of the intricate effects of real earnings management on investment efficiency. This study utilizes a sample of 11,172 firm-year observations from publicly listed companies domiciled in the U.S. The study employs two empirical techniques to examine the research hypotheses: the generalized method of moments (GMM) and multinomial logit with two-way dimensional clustering. By employing robust analytical techniques, this research contributes to the scholarly discourse surrounding REM and its effect in shaping present and future investment. The results demonstrate a robust negative relationship between these two variables. Specifically, a negative association exists between a controlled or low-level of real earnings management with underinvestment and overinvestment. These findings imply that REM is a critical determinant of investment efficiency. Therefore, reducing REM can enable firms to optimize their investments more effectively.
Securitization enhances liquidity of debt contracts. However, its structural deficiency at origination has led to the freezing of its secondary market and failure of institutions holding the ...collateral. This paper builds on key cultural (i.e., Islamic) rulings to rectify flaws entrenched in securitized debt stemming from asymmetric information and agency issues. These injunctions help in the efficient underwriting of debt contracts across the globe to: (i) redeem its ‘toxicity’; (ii) guarantee liquidity; (iii) alleviate fragility of the financial system; and (iv) promote economic growth. Finally, this study promotes a rethink of the current ‘Islamic’ financial system from a narrow literalist juridical perspective to one that is grounded in financial economics.
•This paper employs Islamic rulings to rectify flaws endemic in securitized debt.•These injunctions redeem ‘toxicity’ of debt contracts.•They guarantee liquidity, alleviate fragility, and promote economic growth.
How does competition in firms' product markets influence stock returns? We examine this question using firms domiciled in the UK. We find that firms in less concentrated industries earn higher ...returns, even after controlling for the well-known determinants of the cross-section of UK stock returns. Furthermore, we suggest a novel asset pricing model that explicitly incorporates industry concentration as a distinguished risk factor capturing important features of product markets. Our results link the explanatory power of R&D activity of stock returns to product market structure. Also, we suggest an explanation for value premium on the basis of product market structure that favours barriers to entry interpretation for the higher returns obtained by less concentrated industries.
Two-dimensional materials have shown immense promise for gas-sensing applications due to their remarkable surface-to-volume ratios and tunable chemical properties. However, despite their potential, ...the utilization of ReSe2 as a gas-sensing material for nitrogen-containing molecules, including NO2, NO, and NH3, has remained unexplored. The choice of doping atoms in ReSe2 plays a pivotal role in enhancing the gas adsorption and gas-sensing capabilities. Herein, the adsorption properties of nitrogen-containing gas molecules on metal and non-metal single-atom (Au, Pt, Ni, P, and S)-doped ReSe2 monolayers have been evaluated systematically via ab initio calculations based on density functional theory. The findings strongly suggest that intrinsic ReSe2 has better selectivity toward NO2 than toward NO and NH3. Moreover, our results provide compelling evidence that all of the dopants, with the exception of S, significantly enhance both the adsorption strength and charge transfer between ReSe2 and the investigated molecules. Notably, P-decorated ReSe2 showed the highest adsorption energy for NO2 and NO (−1.93 and −1.52 eV, respectively) with charge transfer above 0.5e, while Ni-decorated ReSe2 exhibited the highest adsorption energy for NH3 (−0.76 eV). In addition, on the basis of transition theory, we found that only Au-ReSe2 and Ni-ReSe2 can serve as reusable chemiresisitve gas sensors for reliable detection of NO and NH3, respectively. Hence, our findings indicate that gas-sensing applications can be significantly improved by utilizing a single-atom-doped ReSe2 monolayer.
The practice of shorting stocks was put forward as one of the causes of the recent financial crisis whereas Shiller (2003), for example, considers shorting an essential element of an efficient ...market. Shorting involves selling borrowed stocks and subsequently closing the position by purchasing and returning the stock to the lender. A profit will be realised if the stock's price decreases. Shorting enables investors who do not own a perceived overvalued stock to sell. Using a high-frequency UK dataset for the period between September 2003 and April 2010, our findings suggest shorting indicates evidence of overvalued stocks as significantly negative abnormal stock returns appear to follow an increase in shorting. These results do not hold, however, for shorting which occurs around the ex-dividend date. We further find that these results hold during the recent financial crisis.
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