Developing efficient and stable oxygen evolution reaction (OER) catalysts that can work well at high current densities for seawater electrolysis is desirable but remains a significant challenge. Here ...a novel and scalable strategy is developed to synthesize partially amorphous boron-modified cobalt iron layered double hydroxides (B-Co2Fe LDH). Benefiting from enhanced electronic kinetics and abundant active sites, this hierarchical nanosheet-nanoflake-structured B-Co2Fe LDH catalyst shows superb OER catalytic activity, requiring overpotentials of 205 and 246 mV to drive current densities of 10 and 100 mA cm−2, respectively, in 1 M KOH, along with a small Tafel slope of 39.2 mV dec−1. Its partial amorphousness feature leads to enhanced stability and corrosion resistance, which help the B-Co2Fe LDH catalyst to work well in the critical seawater condition. It requires overpotentials of 310 and 376 mV to drive current densities of 100 and 500 mA cm−2, respectively, in 1 M KOH seawater and can work continuously for 100 h without producing any hypochlorite. This work can enable the development of LDH catalysts for highly selective seawater oxidation using a general approach.
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•A novel strategy is developed to synthesize partially amorphous boron-modified cobalt iron layered double hydroxides.•The B-Co2Fe LDH catalyst has a hierarchical nanosheet-nanoflake structure to expose active sites with strong corrosion resistance.•It requires low overpotential and shows excellent stability for OER in alkaline seawater.•In situ Raman and post-OER analysis are applied to analyze the transformation of B-Co2Fe LDH during OER.
One-dimensional (1D) structural Cd-doped SnO2 are prepared using shaddock peels as bio-templates via a facile hydrothermal method. The as-synthesized materials are characterized by different ...techniques, including XRD, FESEM, TEM, XPS and N2 adsorption-desorption. Interestingly, unique 1D fiber-like structures are observed and composed of numerous small nanoparticles. Moreover, the result shows that 5 mol% Cd-doped SnO2 nanofibers possesses a larger specific surface area of 38.850 m2/g. At the same time, the gas-sensing properties of sensors based on as-prepared SnO2 nanofibers are also investigated. The 5 mol% Cd-doped SnO2 nanofibers based sensor shows the highest response towards formaldehyde at a lower operating temperature of 160 °C. The excellent gas-sensing properties of sensor towards formaldehyde may attribute to the unique 1D fiber-like structure, large specific surface area and the additive of Cd, which can provide more active sites for the reaction between adsorbed oxygen ions and formaldehyde molecules on the surface of sensing materials. In addition, based on the above experimental results, the possible sensing mechanism of sensor towards formaldehyde is discussed in detail.
Gas sensor based on 5 mol% Cd-doped SnO2 nanofibers prepared using shaddock peels as bio-templates via a facile hydrothermal method shows high gas response, low detection limit and fast response toward various formaldehyde gas at the relative low operating temperature of 160 °C. Display omitted
•Cd-doped SnO2 nanofibers were using shaddock peels as bio-templates at first time.•Cd-doped SnO2 nanofibers based gas sensor shows a high response towards formaldehyde.•Sensor has good repeatability, stability, fast response and recovery towards formaldehyde.•1D structure increases surface area and oxygen specie to promote oxidation of formaldehyde.
•Duplex S-N curve associated with surface and subsurface failures under R = 0 is more obvious.•Deflection of crack surfaces contributes to the slow crack growth especially in the FCA.•Subsurface ...failure mechanism with the determination of stress intensity factors is elucidated.•An energy-based life prediction approach with crack nucleation and growth is proposed.
Fully reversed and pulsating tension fatigue tests were performed to clarify the subsurface failure behavior of TC11 titanium alloy in high-cycle and very-high-cycle regimes. The deflection of crack surfaces induces the premature contact of crack surfaces and slow crack growth. The whole failure processes mainly include: (i) nucleation of microcracks, (ii) coalescence and growth of microcracks, (iii) formation of facet cluster area, (iv) early macrocrack growth, (v) formation of fisheye, (vi) unstable macrocrack growth and (vii) momentary fracture. Based on the modeling of crack nucleation and growth, an energy-based approach is well proposed to predict the total fatigue life.
Ultra-long life fatigue tests of 106-109 cycles under asymmetrical loading were conducted to elucidate the subsurface facets-induced crack nucleation behavior of two alpha-beta titanium alloys, and a ...theoretical method of describing the microstructure-based strength relationship was proposed. As a result, two titanium alloys all present the continuously descending S–N (stress - number of cycles) curve characteristics with subsurface non-defect induced failure. A bright convergence zone with facets becomes the remarkable feature of failure. By means of the milling of focused ion beam system, the coalescence and growth of subsurface micro-cracks crossing several grains along the 45° angle, controlled by the maximum shear stress, can be observable. Based on this, a subsurface facets-induced crack nucleation and growth mechanisms for titanium alloys was proposed in combination with the discussion of small crack fracture mechanics. In view of the good consistency between the evaluated nucleation life of crack at the size of convergence zone with facets and the total life, the microstructure-based modelling method for evaluating fatigue strength of titanium alloys with subsurface failure in ultra-long life regime can be acceptable.
Detecting environmental contaminants is crucial for protecting ecosystems and human health. While traditional carbon dot (CD) fluorescent probes are versatile, they may suffer from limitations like ...fluctuations in signal intensity, leading to detection inaccuracies. In contrast, ratiometric fluorescent probes, designed with internal self-calibration mechanisms, offer enhanced sensitivity and reliability. This review focuses on the design and applications of ratiometric fluorescent probes based on CDs for environmental monitoring. Our discussion covers construction strategies, ratiometric fluorescence principles, and applications in detecting various environmental contaminants, including organic pollutants, heavy metal ions, and other substances. We also explore associated advantages and challenges and provide insights into potential solutions and future research directions.
Pd functionalized TiO2 nanoparticles were synthesized by a facile hydrothermal method. The structure, morphology, surface chemical states and surface area were characterized by X-ray diffraction ...(XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 adsorption-desorption isotherms, respectively. The as-synthesized pure and Pd functionalized TiO2 nanoparticles were used to fabricate indirect-heating gas sensor, and the gas-sensing characteristics towards butane were investigated. At the optimum temperature, the sensors possess good response, selectivity, response/recovery, repeatability as well as long-term stability. Especially for the high response, the response of 7.5 mol% Pd functionalized TiO2 nanoparticles based sensor reaches 33.93 towards 3000 ppm butane, which is about 9 times higher than that of pure TiO2 nanoparticles. The response and recovery time are 13 and 8 s, respectively. Those values demonstrate the potential of using as-synthesized Pd functionalized TiO2 nanoparticles as butane gas detection, particularly in the dynamic monitoring. Apart from these, a possible mechanism related to the enhanced sensing performance is also investigated.
ZnO nanoparticles with high crystallinity and several nanometers in size were synthesized by a low-temperature solvothermal route from zinc acetate dihydrate (Zn(CH
3
COO)
2
·2H
2
O), potassium ...hydroxide (KOH) and methanol (CH
3
OH). The structural and the morphological characterizations of the ZnO nanoparticles were performed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N
2
-sorption isotherms. The obtained nanoparticles are highly crystalline wurtzite-type ZnO with a uniform near-spherical shape and an average particle size estimated to be 8.4 ± 1.3 nm. Such a small particle size and slight agglomeration are attributed to the use of methanol, which acts as both a solvent and an inhibitor of growth and agglomeration. The as-synthesized ZnO nanoparticles were directly used as a gas sensing material toward
n
-butanol gas. Such a designed sensor device exhibits several advantages such as a high and fast response, short recovery time, and good stability toward
n
-butanol gas. At the optimal operating temperature (320 °C), its gas response toward 500 ppm
n
-butanol is 805 and the response and recovery times are 22 and 6 seconds, respectively.
The crack initiation and early growth behaviors of a TC4 titanium alloy under high cycle fatigue and very high cycle fatigue were experimentally investigated. The results show that it exhibits the ...duplex S–N curve characteristics associated with surface and interior failures at a stress ratio of 0.1, while it represents the similar S–N curve characteristics only related to surface failure at a stress ratio of −1. The interior failure is accompanied with the occurrence of facets, granular bright facets (GBFs), and fisheye. Slip-like patterns are observable on the facets easily formed under positive stress ratio. The interior failure process is characterized as (i) occurrence of slip lines on partial α grains under cyclic loading, (ii) initiation and growth of microcracks within some α grains, (iii) coalescence of microcracks and formation of GBF, (iv) stable long crack growth within fisheye, (v) unstable crack growth outside fisheye, and (vi) final momentary fracture.
Group A streptococcus (GAS) species are responsible for a broad spectrum of human diseases, ranging from superficial to invasive infections, and are associated with autoimmune disorders. There is no ...commercial vaccine against GAS. The clinical manifestations of GAS infection may be attributable to the large repertoire of virulence factors used selectively in different types of GAS disease. Here, we selected five molecules, highly conserved among GAS serotypes, and involved in different pathogenic mechanisms, as a multicomponent vaccine, 5CP. Intranasal (i.n.) immunization with 5CP protected mice against both mucosal and systemic GAS infection across serotypes; the protection lasted at least 6 months. Immunization of mice with 5CP constrained skin lesion development and accelerated lesion recovery. Flow cytometry and enzyme-linked immunosorbent assay analyses revealed that 5CP induced Th17 and antibody responses locally and systemically; however, the Th17 response induced by 5CP resolved more quickly than that to GAS when challenge bacteria were cleared, suggesting that 5CP is less likely to cause autoimmune responses. These findings support that immunization through the i.n. route targeting multiple nonredundant virulence factors can induce immunity against different types of GAS disease and represents an alternative strategy for GAS vaccine development, with favorable efficacy, coverage, duration, and safety.
GAS is among the most common human pathogens and causes a wide variety of diseases, likely more than any other microorganism. The diverse clinical manifestations of GAS may be attributable to its large repertoire of virulence factors that are selectively and synergistically involved in streptococcal pathogenesis. To date, GAS vaccines have not been successful due to multiple serotypes and postinfection sequelae associated with autoimmunity. In this study, five conserved virulence factors that are involved in GAS pathogenesis were used as a combined vaccine. Intranasal immunization with this vaccine induced humoral and cellular immune responses across GAS serotypes and protected against mucosal, systemic, and skin infections. The significance of this work is to demonstrate that the efficacy of GAS vaccines can be achieved by including multiple nonredundant critical virulence factors and inducing local and systemic immunity. The strategy also provides valuable insights for vaccine development against other pathogens.
This study aims to explore the relationship between macrosomia and amino acids in maternal and cord sera.
In the case-control study, 78 pairs of mothers and newborns were recruited from December 2016 ...to November 2019. Participants were divided into the macrosomia group (BW ≥ 4000 g,
= 39) and the control group (BW between 2500 g and 3999 g,
= 39) according to the birth weight (BW) of newborns. Maternal vein blood samples were collected before delivery and cord vein blood samples were collected after birth. The levels of amino acids in maternal and cord sera were measured by liquid chromatography and mass spectrometry (LC-MS/MS) in the year 2021. The difference in amino acid levels in maternal and cord sera between the two groups was compared, and the contribution of each amino acid to the difference between the two groups was analyzed. Unconditional logistic regression analysis was used to test the relationship between macrosomia and amino acids.
In maternal serum during the antepartum, the levels of asparagine, glutamine, methionine, alanine, and threonine in the macrosomia group were higher but arginine was lower than that in the control group (
< 0.05). In cord serum, the levels of lysine, histidine, phenylalanine, arginine, tryptophan, valine, isoleucine, glutamate, tyrosine, and total essential amino acid (EAA) in the macrosomia group were lower while glutamine was higher than that in the control group (
< 0.05). The ratios of EAA, valine, threonine, methionine, tryptophan, and alanine in maternal serum to those in cord serum were higher, while the ratio of glutamine was lower in the macrosomia group (
< 0.05). Arginine and threonine in maternal serum and glutamate, glutamine, and histidine in cord serum were associated with macrosomia (
< 0.05).
Most of the amino acid levels in the maternal sera of the macrosomia group are higher than those in the control group, while most of the amino acids' levels in the cord sera of the macrosomia group are lower than those in the control group. The ratios of some amino acids in maternal serum to those in cord serum were different between the two groups. Arginine and threonine in maternal serum and glutamate, glutamine, and histidine in cord serum are closely related to macrosomia.
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