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Fe3O4@Au nanomaterials were prepared by the self‐assembly method. An enzyme‐free, ultrasensitive electrochemical detection of uric acid was achieved based on the peroxidase‐like activity of Fe3O4@Au. The proposed procedure has exhibited excellent catalytic activities and achieved significant enhancements of the current responses to uric acid. The detection range was from 0.1 to 10 mmol/L, and the limit of detection was 0.087 μmol/L. Under the action of external magnetic field, the magnetic particles can be easily separated from the bottom liquid, which has the advantages of simple operation and high separation efficiency. Moreover, this detection method combining a simulated enzyme and electrochemical can enhance the effective output of the overall electrochemical signal without modifying the electrode, and excellent reproducibility can be achieved. Compared to colorimetric assay, the electrochemical one has higher sensitivity and selectivity, and was further applied in ultrasensitive detection of uric acid in food samples. In short, the proposed electrochemical assay has great potential in the fields of food quality control and biomedical analysis. [ABSTRACT FROM AUTHOR]

Syngas is a very important intermediate in chemical industry for energy chemicals production through F–T synthesis. Methane steam reforming (MSR) and dry reforming (MDR) reactions are two extensively studied approaches for syngas production. Developing sintering-resistant catalyst for syngas production from the reforming reactions is a hot topic because high-temperature requirement for the reactions always deactivates catalyst due to sintering and carbon deposition. In this study, we synthesized sintering-resistant Ni@SiO2 catalyst for stable performances of MSR and MDR. Characterization of TEM, XRD, etc., revealed that the Ni@SiO2 catalyst could maintain original core–shell structure and preserve Ni nanoparticle size at temperature as high as 1123 K. The excellent sintering resistance was attributed to encapsulation of thermally stable SiO2 nanospheres, which confined Ni nanoparticles migration and thus avoided aggregation. The work provided a potential sintering-resistant catalyst for heterogeneous reactions. [ABSTRACT FROM AUTHOR]

A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) ring cavity laser employing a twin-core fiber (TCF) comb filter and a nonlinear amplifying loop mirror (NALM) is proposed and demonstrated. By appropriately adjusting the polarization controllers, the NALM as an amplitude equalizer can effectively reduce the mode competition caused by the homogeneous broadening gain medium in the PM-EDF. Under 150 mW pump power, up to 26 wavelength outputs within a 3 dB bandwidth are achieved and their signal-to-noise ratio (SNR) is 39.5 dB. Besides, the TCF comb filter is experimentally fabricated using a length of 0.78 m TCF spliced between two segments of the single-mode fiber. The transmission spectra of the filter in experimental measurements are in accord with the results of theoretical analysis, and its wavelength spacing is 0.29 nm. Meanwhile, the power fluctuation and wavelength shift are within 0.1 dB and 0.02 nm, respectively. The experimental results indicate that the proposed multi-wavelength fiber laser performs with high stability at room temperature. In addition, the multi-wavelength laser with the TCF comb filter can offer more wavelengths in a 3 dB spectral range and higher SNR than one using a Sagnac loop filter, and the length of the filter is also reduced by more than six times. [ABSTRACT FROM AUTHOR]

A free radical scavenging system based on Fe 3 O 4 @Au/MOF-ABTS˙ + has formed the basis of a novel method for the highly sensitive and specific spectrophotometric determination of ascorbic acid (AA). The Fe 3 O 4 @Au/MOF nanozyme with magnetic separation properties was effectively prepared and evaluated using an environmentally friendly technique. Nanomaterials have the advantages of superparamagnetism, biocompatibility, chemical stability, and enhanced synergistic peroxidase-like activity, which can be utilized in catalysis to oxidise the peroxidase substrate 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) into a green-colored product in the presence of H 2 O 2 . AA as an antioxidant has scavenging effects on ABTS radicals and can reduce green ABTS˙ + to uncolored ABTS 2- , contributing to a substantial reduction in green color. Based on such a premise, a highly selective and sensitive chromogenic sensing method depending on the peroxidase-like activity of the nanocomposites was developed in order to achieve the efficient detection of AA in real samples. Under optimum conditions, the proposed technique had a detection range of 0.001-0.1 mmol L -1 , a limit of detection of 0.098 μmol L -1 , and a detection time of only 30 seconds. The newly proposed colorimetric analysis method devoid of enzymes has broad application potential in the areas of quality control and quality and safety detection.