Morphological variation of multiwall carbon nanotubes in supercritical water oxidation

[[abstract]]The morphological variation of multiwall carbon nanotubes (MWNT) in supercritical water oxidation (SCW) was investigated using a transmission electron microscope (TEM) and electron energy-loss spectroscopy (EELS). It was found that the peeling and sharpening of MWNT were influenced by the etching process in SCW oxidation. It was also found that the difference of mean etching rate between two adjoining blocks causes the morphological variation of MWNT. The results show that the change in characteristic energy-loss peaks as a function of total shell numbers along longitudinal axis of individual peeled tube.[[fileno]]2010304010019[[department]]化學

Oxygen radical-mediated oxidation reactions of an alanine peptide motif - density functional theory and transition state theory study

<p>Abstract</p> <p>Background</p> <p>Oxygen-base (O-base) oxidation in protein backbone is important in the protein backbone fragmentation due to the attack from reactive oxygen species (ROS). In this study, an alanine peptide was used model system to investigate this O-base oxidation by employing density functional theory (DFT) calculations combining with continuum solvent model. Detailed reaction steps were analyzed along with their reaction rate constants.</p> <p>Results</p> <p>Most of the O-base oxidation reactions for this alanine peptide are exothermic except for the bond-breakage of the C_α-N bond to form hydroperoxy alanine radical. Among the reactions investigated in this study, the activated energy of OH α-H abstraction is the lowest one, while the generation of alkylperoxy peptide radical must overcome the highest energy barrier. The aqueous situation facilitates the oxidation reactions to generate hydroxyl alanine peptide derivatives except for the fragmentations of alkoxyl alanine peptide radical. The C_α-C_βbond of the alkoxyl alanine peptide radical is more labile than the peptide bond.</p> <p>Conclusion</p> <p>the rate-determining step of oxidation in protein backbone is the generation of hydroperoxy peptide radical via the reaction of alkylperoxy peptide radical with HO₂. The stabilities of alkylperoxy peptide radical and complex of alkylperoxy peptide radical with HO₂are crucial in this O-base oxidation reaction.</p

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Development of Two-Dimensional Functional Nanomaterials for Biosensor Applications: Opportunities, Challenges, and Future Prospects

New possibilities for the development of biosensors that are ready to be implemented in the field have emerged thanks to the recent progress of functional nanomaterials and the careful engineering of nanostructures. Two-dimensional (2D) nanomaterials have exceptional physical, chemical, highly anisotropic, chemically active, and mechanical capabilities due to their ultra-thin structures. The diversity of the high surface area, layered topologies, and porosity found in 2D nanomaterials makes them amenable to being engineered with surface characteristics that make it possible for targeted identification. By integrating the distinctive features of several varieties of nanostructures and employing them as scaffolds for bimolecular assemblies, biosensing platforms with improved reliability, selectivity, and sensitivity for the identification of a plethora of analytes can be developed. In this review, we compile a number of approaches to using 2D nanomaterials for biomolecule detection. Subsequently, we summarize the advantages and disadvantages of using 2D nanomaterials in biosensing. Finally, both the opportunities and the challenges that exist within this potentially fruitful subject are discussed. This review will assist readers in understanding the synthesis of 2D nanomaterials, their alteration by enzymes and composite materials, and the implementation of 2D material-based biosensors for efficient bioanalysis and disease diagnosis

Development of Nonstoichiometric CuInS₂ as a Light-Harvesting Photoanode and Catalytic Photocathode in a Sensitized Solar Cell

A simple one-pot approach was developed to obtain nonstoichiometric CuInS₂ nanocrystals. Using this approach, both In-rich and Cu-rich CuInS₂ nanocrystals could be reliably synthesized by tuning stoichiometric combinations of [Cu]/[In] precursor constituents. By designing Cu-rich CuInS₂ heteronanostructures to serve as counter electrodes, quantum-dot-sensitized solar cells (QDSSCs) equipped with In-rich CuInS₂ and CdS cosensitizers delivered a power conversion efficiency of 2.37%, which is significantly more efficient than conventional Pt counter electrodes. To the best of our knowledge, this study represents the first report utilizing nonstoichiometric CuInS₂ nanocrystals as a photon-harvesting sensitizer comprised of a photoanode and photocathode in QDSSCs; also unique to this report, these nonstoichiometric CuInS₂ nanocrystals were formed by simply changing the cationic molar ratios without complicated precursor preparation. Impedance spectroscopy and Tafel polarization indicated that these Cu-rich CuInS₂ heteronanostructures had electrocatalytic activities (used for reducing S^2–/S_<i>n</i>^2–) that were superior to a Pt catalyst. Moreover, we demonstrated that Cu-rich CuInS₂ heteronanostructures were also useful counter electrodes in dye-sensitized solar cells, and this finding revealed a promising conversion efficiency of 6.11%, which was ∼96% of the efficiency in a cell with a Pt-based counter electrode (6.32%)

Improved Performance of CuInS₂ Quantum Dot-Sensitized Solar Cells Based on a Multilayered Architecture

This Article describes a CuInS₂ quantum dot (QD)-sensitized solar cell (QDSSC) with a multilayered architecture and a cascaded energy-gap structure fabricated using a successive ionic-layer adsorption and reaction process. We initially used different metal chalcogenides as interfacial buffer layers to improve unmatched band alignments between the TiO₂ and CuInS₂ QD sensitizers. In this design, the photovoltaic performance, in terms of the short-circuit current density (<i>J</i>_SC), open-circuit voltage (<i>V</i>_OC), fill factor (FF), and power conversion efficiency (PCE), was significantly improved. Both <i>J</i>_SC and <i>V</i>_OC were improved in CuInS₂-based QDSSCs in the presence of interfacial buffer layers because of proper band alignment across the heterointerface and the negative band edge movement of TiO₂. The PCE of CuInS₂-based QDSSCs containing In₂Se₃ interfacial buffer layers was 1.35%, with <i>J</i>_SC = 5.83 mA/cm², <i>V</i>_OC = 595 mV, and FF = 39.0%. We also examined the use of alternative CdS and CdSe hybrid-sensitized layers, which were sequentially deposited onto the In₂Se₃/CuInS₂ configuration for creating favorable cascaded energy-gap structures. Both <i>J</i>_SC (11.3 mA cm^–2) and FF (47.3%) for the CuInS₂/CdSe hybrid-sensitized cells were higher than those for CuInS₂-based cells (<i>J</i>_SC = 5.83 mA cm^–2 and FF = 39.0%). In addition, the hybrid-sensitized cells had PCEs that were 1.3 times those of cells containing identically pretreated In₂Se₃ interfacial buffer layers. Additionally, we determined that ZnSe served as a good passivation layer on the surface of CuInS₂/CdSe hybrid-sensitized QDs, prevented current leakage from the QDs to electrolytes, and lowered interfacial charge recombination. Under simulated illumination (AM 1.5, 100 mW cm^–2), multilayered QDSSCs with distinct architectures delivered a maximum external quantum efficiency of 80% at 500 nm and a maximum PCE of 4.55%, approximately 9 times that of QDSSCs fabricated with pristine CuInS₂

Biomass-Mediated Synthesis of Cu-Doped TiO2 Nanoparticles for Improved-Performance Lithium-Ion Batteries

Pure TiO2 and Cu-doped TiO2 nanoparticles are synthesized by the biomediated green approach using the Bengal gram bean extract. The extract containing biomolecules acts as capping agent, which helps to control the size of nanoparticles and inhibit the agglomeration of particles. Copper is doped in TiO2 to enhance the electronic conductivity of TiO2 and its electrochemical performance. The Cu-doped TiO2 nanoparticle-based anode shows high specific capacitance, good cycling stability, and rate capability performance for its envisaged application in lithium-ion battery. Among pure TiO2, 3% Cu-doped TiO2, and 7% Cu-doped TiO2 anode, the latter shows the highest capacity of 250 mAh g–1 (97.6% capacity retention) after 100 cycles and more than 99% of coulombic efficiency at 0.5 A g–1 current density. The improved electrochemical performance in the 7% Cu-doped TiO2 is attributed to the synergetic effect between copper and titania. The results reveal that Cu-doped TiO2 nanoparticles might be contributing to the enhanced electronic conductivity, providing an efficient pathway for fast electron transfer

Synthesis of Eco-Friendly CuInS₂ Quantum Dot-Sensitized Solar Cells by a Combined Ex Situ/in Situ Growth Approach

A cadmium-free CuInS₂ quantum dot (QD)-sensitized solar cell (QDSC) has been fabricated by taking advantage of the ex situ synthesis approach for fabricating highly crystalline QDs and the in situ successive ionic-layer adsorption and reaction (SILAR) approach for achieving high surface coverage of QDs. The ex situ synthesized CuInS₂ QDs can be rendered water soluble through a simple and rapid two-step method under the assistance of ultrasonication. This approach allows a stepwise ligand change from the insertion of a foreign ligand to ligand replacement, which preserves the long-term stability of colloidal solutions for more than 1 month. Furthermore, the resulting QDs can be utilized as sensitizers in QDSCs, and such a QDSC can deliver a power conversion efficiency (PCE) of 0.64%. Using the SILAR process, in situ CuInS₂ QDs could be preferentially grown epitaxially on the pre-existing seeds of ex situ synthesized CuInS₂ QDs. The results indicated that the CuInS₂ QDSC fabricated by the combined ex situ/in situ growth process exhibited a PCE of 1.84% (short-circuit current density = 7.72 mA cm^–2, open-circuit voltage = 570 mV, and fill factor = 41.8%), which is higher than the PCEs of CuInS₂ QDSCs fabricated by ex situ and in situ growth processes, respectively. The relative efficiencies of electrons injected by the combined ex situ/in situ growth approach were higher than those of ex situ synthesized CuInS₂ QDs deposited on TiO₂ films, as determined by emission-decay kinetic measurements. The incident photon-to-current conversion efficiency has been determined, and electrochemical impedance spectroscopy has been carried out to investigate the photovoltaic behavior and charge-transfer resistance of the QDSCs. The results suggest that the combined synergetic effects of in situ and ex situ CuInS₂ QD growth facilitate more electron injection from the QD sensitizers into TiO₂