Enhanced methanol oxidation on PtNi nanoparticles supported on silane-modified reduced graphene oxide

Developing low cost, highly efficient, and long-term stability electrocatalysts are critical for direct oxidation methanol fuel cell. Despite huge efforts, designing low-cost electrocatalysts with high activity and long-term durability remains a significant technical challenge. Here, we prepared a new kind of platinum-nickel catalyst supported on silane-modified graphene oxide (NH₂-rGO) by a two-step method at room temperature. Powder X-ray diffraction, UV–vis spectroscopy, Raman, FTIR spectroscopy and X-ray photoelectron spectroscopy results confirm that GO was successfully modified with 3-aminopropyltriethoxysilane (APTES), which helps to uniformly disperse PtNi nanoparticles. Cyclic voltammetry, chronoamperometry, CO-stripping and rotating disk electrode (RDE) results imply that PtNi/NH₂-rGO catalyst has significantly higher catalytic activity, enhance the CO toxicity resistance, higher stability and much faster kinetics of methanol oxidation than commercial Pt/C under alkaline conditions.     

电信专业学术英文写作模块化教学实践

学术英文写作是当今电子信息专业研究生必修的一门课程。然而传统的以教师为中心的灌输式教学已不能跟上网络迅猛发展的趋势,尤其是当疫情来临的特殊形势下。此外,现有的学术英文写作教学研究仅提供宏观的设计,缺乏具体的实际可操作性。为此,本文以引言写作逻辑为教学模块案例,探索了如何充分利用网络资源的优势,开展以学生为中心的课前课中课下有机融合的灵活的教学设计。所探索的引言写作技巧和详实的教学设计,为模块化网络教学提供一个切实可行的参考方案。     

Swapping catalytic active sites from cationic Ni to anionic F in Fe–F–Ni3S2 enables more efficient alkaline oxygen evolution reaction and urea oxidation reaction

Electrolysis of water for producing hydrogen instead of traditional fossil fuels is one of the most promising methods to alleviate environmental pollution and energy crisis. In this work, Fe and F ion co-doped Ni₃S₂ nanoarrays grown on Ni foam substrate were prepared by typical hydrothermal and sulfuration processes for the first time. Density functional theory (DFT) calculation demonstrate that the adsorption energy of the material to water is greatly enhanced due to the doping of F and Fe, which is conducive to the formation of intermediate species and the improvement of electrochemical performance of the electrode. The adsorption energy of anions (F and S) and cations (Fe and Ni) to water in each material was also calculated, and the results showed that F ion showed the most optimal adsorption energy of water, which proved that the doping of F and Fe was beneficial to improve the electrochemical performance of the electrode. It is worth noting that the surface of Fe–F–Ni₃S₂ material will undergo reconstruction during the process of water oxidation reaction and urea oxidation reaction, and amorphous oxides or hydroxides in situ would be formed on the surface of electrode, which are the real active species.     

Hydrangea like composite catalysts of ultrathin Mo2S3 nanosheets assembled on N,S-dual-doped graphitic biocarbon spheres with highly electrocatalytic activity for HER

Water electrolysis is the most clean and high-efficiency technology for production of hydrogen, an ultimate clean energy in future. Highly efficient non-noble electrocatalysts for hydrogen evolution reaction (HER) are desirable for large scale production of hydrogen by water electrolysis. Especially, exposing as many active sites as possible is a vital way to improve activities of the catalysts. Herein, a series of new hydrangea like composite catalysts of ultrathin Mo₂S₃ nanosheets assembled uprightly and interlacedly on N, S-dual-doped graphitic biocarbon spheres were facilely prepared. The unique structure endowed the catalysts highly exposed edge active sites and prominently high activities for HER. Especially, the optimized catalyst Mo₂S₃/NSCS-50 exhibited as low as 106 mV of overpotential at 10 mA/cm² (denoted as ?₁₀). The catalyst also showed low Tafel slope of 53 mV/dec, low electron transfer resistance of 34 Ω and high stability evidenced by the result that the current density only attenuated 11.7% after 10 h i-t test. The catalyst has shown broad prospect for commercial application in water electrolysis.     

Evaluation of physicochemical properties and microbial counts of raw and cooked low-fat patties added with eggplant powder prepared with different drying methods

Effects of different drying methods and different addition levels of eggplant (EP) on product quality of low-fat patties (LFPs) were investigated during storage. EP was dried in an oven dryer at 60 °C or a freeze dryer at −50 °C. LFPs were prepared by replacing with 1.5% soy protein isolate (SPI). Six treatments were used in this study: (1) control (CTL), without addition of EP; (2) reference (REF), 0.1% ascorbic acid; (3) O1, 0.25% oven-dried (OD) EP; (4) O2, 0.5% ODEP; (5) F1, 0.25% freeze-dried (FD) EP; and (6) F2, 0.5% FDEP. Redness (a*) and lightness (L*) values in LFPs added with EP were lower than those of others (p < 0.05) and decreased with increasing storage time. Yellowness (b*) values of cooked patties were increased during storage time (p < 0.05), with control having the highest value. The addition of EP or ascorbic acid into LFPs lowered microbial counts than control (p < 0.05). Thiobarbituric acid reactive substances (TBARS) was increased during storage, with REF having the lowest value, and patties added with EP had lower TBARS values than control during storage. Volatile basic nitrogen (VBN, mg%) contents of all patties also increased during storage time with O2 and F2 having lower values than control. Therefore, EP might have potential as a natural antioxidant in meat products during storage.     

Microstructure and some properties of powder-pack borided Ti–5Mo–5V–8Cr–3Al alloy with special attention to the microstructure at the interface TiB/substrate

The borided layer was prepared on the surface of the Ti–5Mo–5V–8Cr–3Al alloy by powder-pack boriding at 1000°C-10h. SEM, EPMA and TEM were used to investigate the effects of alloying elements (Al, V, Mo and Cr) on the growth of TiB whiskers in the borided Ti–5Mo–5V–8Cr–3Al alloy. Wear properties of borided Ti–5Mo–5V–8Cr–3Al alloy were investigated using dry reciprocating friction tests. SEM results show that the thickness of boride layer in Ti–5Mo–5V–8Cr–3Al alloy is thinner than that in the Cp-Ti. This is attributed to the enrichment of alloying elements especially V in TiB/substrate by TEM, which hinders the diffusion of B atoms, thus resulting in the short and thick TiB whiskers in Ti–5Mo–5V–8Cr–3Al alloy. Borided Ti–5Mo–5V–8Cr–3Al alloy has the better wear resistance than as-received alloy.     

雪菊精油对希氏肠球菌产酪胺及相关基因表达的影响

探讨不同质量浓度雪菊精油对希氏肠球菌（Enterococcus hirae）N47产酪胺的影响机制。利用反转录实时定量聚合酶链式反应分析E. hirae在雪菊精油作用下酪氨酸脱羧途径相关基因的表达情况；利用高效液相色谱法检测不同质量浓度雪菊精油对E. hirae产酪胺的影响。并将E. hirae接入到含不同质量浓度雪菊精油的熏马肠中发酵，评估香肠pH值、菌落总数和酪胺积累量。结果表明：在E. hirae纯培养体系和熏马肠体系中，雪菊精油通过抑制微生物的生长和酪氨酸脱羧途径中tyr DC、tyr P基因的表达，降低酪胺的积累量（P＜0.05）。当雪菊精油添加量为1/2最小抑菌浓度（minimal inhibitory concentration，MIC）和MIC时，熏马肠中酪胺的含量分别为78.52 mg/kg和45.83 mg/kg，较对照组分别减少了64.72%和79.41%。     

基于乙酰胆碱酯酶和氧化应激研究海胆酮对阿尔茨海默症的作用机制

海胆酮是一种酮式类胡萝卜素，主要从海胆及藻类等海洋生物中提取。本文研究海胆酮对乙酰胆碱酯酶（acetylcholinesterase，AChE）的抑制作用，应用酶动力学、荧光光谱、圆二色光谱和分子对接技术研究海胆酮对AChE的抑制机理，并用淀粉样β蛋白片段25～35（amyloid beta-peptide 25-35，Aβ25-35）诱导大鼠肾上腺嗜铬细胞瘤细胞（PC12细胞）建立阿尔茨海默症（Alzheimer’s disease，AD）模型，研究海胆酮对AD细胞模型氧化应激损伤的作用。结果表明，海胆酮有很强的AChE抑制活性，其半抑制质量浓度为（16.29±0.97）μg/mL，抑制常数Ki为3.82 μg/mL，表现为竞争性抑制；海胆酮可诱导AChE二级结构改变，更容易与AChE活性中心氨基酸Ser200、His440、Trp84和Tyr121结合，阻碍底物碘代硫代乙酰胆碱（acetylthiocholine iodide，ATCI）与酶结合，从而引起酶活力降低。海胆酮能有效抑制Aβ25-35诱导PC12细胞的AChE活力，降低丙二醛含量，增加超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶活力，减轻Aβ25-35诱导的PC12细胞氧化应激损伤。本研究基于AChE和氧化应激阐明了海胆酮对AD的潜在作用机制，为海胆酮在功能食品、生物医药等领域的应用提供了数据支持和理论根据。