Latest ArticlesNonaqueous Li-O2 batteries attract attention for their theoretical specific energy density. However, due to the difficulty of decomposition of Li2O2, Li-O2 batteries have high charge overpotential and poor cycling life. So all kinds of catalysts have been studied on the cathode. Compared to heterogeneous solid catalysts, soluble catalysts achieve faster and more effective transport of electrons by reversible redox pairs. Here, we first report ruthenocene (Ruc) as a mobile redox mediator in a Li-O2 battery. 0.01 mol/L Ruc in the electrolyte effectively reduces the charging voltage by 610 mV. Additionally, Ruc greatly increases the cycling life by four-fold (up to 83 cycles) with a simple ketjen black (KB) cathode. The results of SEM, XPS and XRD confirm that less discharge product residue accumulated after recharge. To verify the reaction mechanisms of the mediator, free energy profiles of the possible reaction pathways based on DFT are provided.
Nano-polyhedral NiSe2/CoSe2 (Ni-Co-Se) with hollow architectures are synthesized by selenizing the precursors of Ni-Co bimetallic hydroxides that are directly derived from ZIF-67. The as-fabricated Ni-Co-Se electrodes exhibit high specific capacitance of 1668 F/g at 1 A/g accompanying with outstanding rate capability (about 82.8% retention of the initial capacity at 20 A/g). The corresponding Ni-Co-Se//AC all-solid-state hybrid supercapacitors are assembled by directly using the Ni-Co-Se on carbon fabric as the positive electrode, which deliver high energy density and power density (38.5 Wh/kg at 802.1 W/kg, 32.0 Wh/kg at 8008.8 W/kg), excellent cyclic stability (82.3% retention after 5000 cycle) and robust mechanical flexibility (no obvious attenuation at bending to different angles). This work will provide a new and smart route for constructing transition metal selenides for supercapacitor devices.
The metal organic framework functionalized with sulfonic acid was combined with magnetic nanoparticles to fabricate a new nanocomposite (denoted as Fe3O4@PDA@Zr-SO3H). By combining with gas chromatography-electron capture detector, the resulting Fe3O4@PDA@Zr-SO3H nanocomposite was successfully used as a high-efficiency adsorbent for pre-concentrating eight organochlorine pesticides from water sample in environment. Apart from the ability of fast separation, the as-prepared Fe3O4@PDA@Zr-SO3H nanocomposite also exhibited high adsorption capacity for organochlorine pesticides. With the use of optimal experimental conditions, the linear relationship can be obtained in the range of 0.05~300 μg/L, the correlation coefficient was over 0.9978, and the relative standard deviation was located in 2.5%-7.7%. Moreover, the limit of detection and quantification was between 0.005-0.016 μg/L and 0.017~0.050 μg/L. Finally, the nanocomposite was used for the determination of organochlorine pesticides from environmental water samples, and displayed the recovery of 82%-118%.
In recent years, the research of nitrogen reduction reaction (NRR) under ambient conditions has attracted wide attention for their relatively low energy consumption, in which rational design of electrocatalysts is the key to achieve high-performance NRR. Metal-organic frameworks (MOFs), as a new kind of porous material, have been intensively studied in the past few decades owing to not only their structural versatility and tunability but also intrinsic porosity. Due to their structural features, MOFs also have potential applications in mild condition electrocatalysis of NRR. In this review, the recently experimental and theoretical studies of MOFs in NRR electrocatalysts are briefly summarized.
In this work, a series of chitin-supported Ru catalysts, composed of ultrasmall Ru nanoparticles supported on the chitin nanofibers, with different Ru content from 0.07 wt% to 0.93 wt%, are fabricated. Results from catalyzed NaBH4 hydrolysis experiments indicate that the catalytic activity of the fabricated chitin-supported Ru catalysts increases gradually with the decreasing of Ru content. The rate of hydrogen generation from NaBH4 hydrolysis catalyzed by the catalyst with 0.07 wt% Ru content is as high as 55.29 L min-1 at 30 ℃, and this reaction exhibits activation energy of 39.16 kJ/mol. The augment of NaBH4 dosage in the experiments does not weaken the catalytic activity. In addition, the fabricated chitin-supported Ru catalysts show excellent durability in NaBH4 hydrolysis, with only 9.2% activity loss after used for 20 cycles. With excellent catalytic activity and durability, the as-obtained Ru catalysts provide a promising choice for promoting hydrogen production from NaBH4 hydrolysis.
Robust normalization is a prerequisite for reliable metabonomic analysis especially when intervention treatments cause drastic metabolomic changes or when spot urinary samples are employed without knowing the drinking water quantity. With the simulated and real datasets, here, we report a probabilistic quotient normalization method based on the mode-of-quotients (mPQN) which is suitable for metabonomic analysis of both NMR and LC-MS data with little and/or drastic metabolite changes. When applied to metabonomic analysis of both animal plasma samples and human urinary samples, this newly proposed method has clearly shown better robustness than all classical normalization methods especially when drastic changes of some metabolites occur.
By virtue of electrochemistry, a series of α, α-dihaloacetophenones were easily obtained with good to excellent yields. This electrochemical procedure was taken in a divided cell with constant current in aqueous media. The reaction can be carried out smoothly at room temperature under metal and oxidant free condition, which provides an eco-friendly synthesis for the α, α-dihaloacetophenone derivatives.
Accurate temperature measurement plays an important role in a variety of industrial processes and scientific researches. In our work, the dual-mode temperature response nanoprobe CDs-Tb-TMPDPA containing a two-photon ligand (4-(2, 4, 6-trimethoxyphenyl)-pyridine-2, 6-dicarboxylic acid, TMPDPA) sensitized Tb3+ as a temperature-sensitive unit and carbon dots (CDs) as photothermal reagent and a fluorescence reference unit, have been designed and synthesized. In this system, both the fluorescence intensity ratio and the fluorescence lifetime have a good response to temperature. In addition, due to the excellent photothermal conversion capability of CDs, photothermal antibacterial ability was also tested. Based on the temperature dependence of the fluorescence and the two-photon excitation characteristics of CDs-Tb-TMPDPA, the nanoprobe can also be used in the anti-counterfeiting. Our finding opens a new prospect for the use of two-photon sensitized dual-mode fluorescence thermometers.
Anodic electrocatalyst plays the core role in direct alcohol fuel cells (DAFCs), while traditional Pt-catalysts suffer from limited catalytic activity, high over potential and severe CO poisoning. Herein, by selectively depositing Rh atoms on the defective-sites of Pt nanowires (NWs), we developed a new Pt@Rh NW electrocatalyst that exhibited enhanced electrocatalytic performance for both methanol oxidation (MOR) and ethanol oxidation (EOR). Both cyclic voltammetry (CV) and in-situ infrared spectroscopy revealed that the presence of Rh atoms suppressed the generation of poisonous intermediates and completely oxidized alcohols molecule into CO2. Atomic resolusion spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy (CS-HAADF-STEM) and energy-dispersive X-ray spectroscopy (EDS) mapping analysis revealed that Rh atoms were primarily deposited on the defective sites of Pt NWs. Meanwhile, the presence of Rh atoms also modified the electronic state of Pt atoms and therefore lowered the onset potential for alcohols oxidation potential. This work gives the first clear clue on the role of the defective sites of Pt nanocatalyst poisoning, and propose that selectively blocking these sites with trace amount of Rh is an effective strategy in designing advantageous electrocatalysts.
Diarrhea, as a global public health problem, causes a large number of infections and deaths every year. Although Escherichia coli (E. coli) is one of the normal flora microorganisms in the human intestinal tract, it has five pathogenic bacteria types that can cause human diarrhea, known as diarrheagenic E. coli. When people are infected, rapid and accurate diagnosis, along with timely treatment, are especially important. Here, we introduce a new method to identify and analyze a large number of pathogenic strains in E. coli by multiplex PCR and barcoded magnetic bead hybridization. Results show that the detection sensitivities of enterohemorrhagic E. coli, enterotoxigenic E. coli, enteropathogenic E. coli, enteroinvasive E. coli and enteroaggregative E. coli were 1.3×103 CFU/mL, 2×104 CFU/mL, 4×104 CFU/mL, 7.2×104 CFU/mL and 1.7 CFU/mL respectively. This method has strong specificity and high sensitivity and detects multiple target sequences in one experiment. Compared with other methods, BMB array has great application potential.
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