Simultaneous photocatalytic oxidation and adsorption for efficient As(III) removal by magnetic BiOI/γ-Fe2O3 core–shell nanoparticles

Addressing arsenite pollution in groundwater has drawn great attention. It is attractive to pre-oxidize highly mobile As(III) to relatively low-toxic As(V) with a subsequent adsorption separation process. Herein, BiOI anchoring on γ-Fe₂O₃ is performed to synthesize BiOI/γ-Fe₂O₃ core–shell nanoparticles for efficient removal of As(III) via a simultaneous photocatalytic oxidization–adsorption process. The physical and chemical structures of BiOI/γ-Fe₂O₃ are investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction measurements. The photoluminescence and electron spin resonance (ESR) characterization were employed to ascertain the possible reaction mechanism of visible-light-driven photocatalytic oxidation of As(III). Such BiOI/γ-Fe₂O₃ delivers a superior As(III) removal capability under visible light irradiation with an arsenic removal efficiency of 99.8% within 180 min, higher than those of BiOCl/γ-Fe₂O₃ (81.7%) and BiOBr/γ-Fe₂O₃ (98.9%). The optimal BiOI/γ-Fe₂O₃ (molar ratio of 2:1) is obtained by rationally adjusting the molar ratio of BiOI to γ-Fe₂O₃. The as-synthesized BiOI/γ-Fe₂O₃ performs well in a wide pH range of 2–8. Only coexisting PO₄^3? anions have a significant effect on the As(III) removal. The free radical trapping experiment and ESR results demonstrate that the ?O₂^? and h⁺ are the main active substances for the photocatalytic oxidation of As(III) on BiOI/γ-Fe₂O₃. This work not only gives a novel magnetic core–shell nanoparticle photocatalyst for efficient photocatalytic oxidation and adsorption of As(III) but also offers a new strategy to rationally design BiOX for its related practical applications.     

Late-Stage Modification of Aminoglycoside Antibiotics Overcomes Bacterial Resistance Mediated by APH(3’) Kinases

The continuous emergence of antimicrobial resistance is causing a threat to patients infected by multidrug-resistant pathogens. In particular, the clinical use of aminoglycoside antibiotics, broad-spectrum antibacterials of last resort, is limited due to rising bacterial resistance. One of the major resistance mechanisms in Gram-positive and Gram-negative bacteria is phosphorylation of these amino sugars at the 3’-position by O-phosphotransferases [APH(3’)s]. Structural alteration of these antibiotics at the 3’-position would be an obvious strategy to tackle this resistance mechanism. However, the access to such derivatives requires cumbersome multi-step synthesis, which is not appealing for pharma industry in this low-return-on-investment market. To overcome this obstacle and combat bacterial resistance mediated by APH(3’)s, we introduce a novel regioselective modification of aminoglycosides in the 3’-position via palladium-catalyzed oxidation. To underline the effectiveness of our method for structural modification of aminoglycosides, we have developed two novel antibiotic candidates overcoming APH(3’)s-mediated resistance employing only four synthetic steps.     

微弧氧化陶瓷膜封孔后处理及抗高温氧化性能的研究

在铝酸盐体系中,利用微等离体氧化脉冲电源在Ti-6Al-4V合金表面制备了以Al2TiO5为主晶相的陶瓷膜层,然后采用钛酸四丁酯/乙醇和硅酸钠溶液的封孔方法对微弧氧化陶瓷膜进行封孔后处理。通过SEM及高温氧化测试,分析比较了陶瓷膜层在封孔前后的表面形貌以及抗高温氧化性能的变化情况。结果表明:封孔后膜层孔洞明显变小。经700℃高温氧化测试,采用钛酸四丁酯/乙醇溶液封孔方法不仅没有带来抗高温氧化性能的提高反而下降,而硅酸钠溶液的封孔方法提高了抗高温氧化性能。     

Fe掺杂Mn/TiO2低温脱硝催化剂的催化性能研究

采用氧化沉淀-浸渍法制备了不同含量Fe掺杂的Fe-Mn/TiO2低温脱硝催化剂,考察了催化剂在80~180 ℃范围内的脱硝能力并通过XRD、BET、TG、H2-TPR、NH3-TPD等测试手段,对催化剂的物理化学性质进行了表征.实验结果表明,Fe的加入并没有改变Mn/TiO2的主要晶相,仍是锐钛矿型的TiO2,MnOx和FeOx均以非晶态结构高度分散于载体表面,而且Fe的加入可以有效地改善催化剂的微观形貌、比表面积及表面酸性位点,从而提高其低温脱硝性能.Fe掺量在Fe/Ti为0.10时催化剂具有最佳性能,在120 ℃时脱硝率可达90;以上.     

Ti6A14V表面微弧氧化陶瓷涂层的结构和摩擦学特性

采用交流微弧氧化法，在Na2SiO3-(NaPO3)6-Na3MoO4溶液中制备了Ti6A14V表面氧化物陶瓷涂层，用X射线衍射仪、扫描电子显微镜和球-盘摩擦磨损试验机研究了涂层的结构、形貌及摩擦学性能，用纳米压痕仪测定了涂层致密层的硬度，用扫描电子显微镜观察涂层磨损表面形貌，用能谱仪分析涂层磨屑的元素组成．结果表明：厚约20pm的涂层致密均匀，主要由锐钛矿和金红石相氧化钛组成；涂层致密层的硬度约为13．5GPa；在0．5N低载荷和摩擦循环次数小于2000次条件下，涂层同GCrl5钢对摩时的摩擦系数仅为0．18～0．20，较基底Ti6A14V与其对摩的摩擦系数低得多．摩擦过程中较软的GCr15钢球材料向涂层表面转移，涂层的磨损机制主要是轻微磨粒磨损与粘着磨损．     

二硫化钼表面氧化行为的研究（Ⅱ）─—二硫化钼摩擦表面氧化与电子转移的研究

利用电子自旋共振谱和Ｘ射线光电子能谱研究了二硫化钼ＭｏＳ＿２摩擦表面的氧化和电子转移，发现ＭｏＳ＿２在摩擦过程中是以Ｍｏ￣（４＋）经由Ｍｏ￣（５＋）过渡态继而与氧作用生成稳定的Ｍｏ￣（６＋），并且是以ＭｏＯ＿３的形式存在，证明ＭｏＳ＿２的摩擦表面除有一般认为的Ｍｏ￣（４＋）和Ｍｏ￣（６＋）这两种化学状态以外，还有Ｍｏ￣（５＋）自由基离子这种从未发现的的中间态。Ｍｏ￣（５＋）是４ｄ￣１电子构型，其在室温下于空气或氧气中是稳定的，然而在摩擦环境或添加剂的作用下，Ｍｏ￣（５＋）所含不成对电子很容易发生转移而生成Ｍｏ￣（６＋），这种研究结果更加深入地揭示了ＭｏＳ＿２摩擦表面氧化过程的复杂性，因此，应当从摩擦化学角度重新认识ＭｏＳ＿２摩擦氧化产物及其形成机制，这于研究摩擦环境和添加剂对润滑剂的抗氧化协同效应具有重要意义。     

鲱鱼精DNA的电化学氧化及与组蛋白的相互作用

应用循环伏安法、微分脉冲伏安法和荧光光谱法研究了鲱鱼精DNA的电化学氧化及其与组蛋白的相互作用.结果发现,在0.20~1.25 V电位区间内,DNA在酸性溶液中呈现一个明显的不可逆氧化峰,在中性及碱性溶液中呈现两个不可逆氧化峰.氧化峰电位随溶液pH值增大而负移,变化幅度为-57 mV.pH-1.氧化峰电流与DNA浓度(0.45~8.20 mmol.L-1)成线性关系.DNA能与组蛋白结合,导致氧化电位正移,氧化电流减小,并减弱钌配合物指示剂和DNA相互作用的荧光强度以及减少DNA的氧化损伤.     

高温氧化-化学发光检测法测定水中总氮

采用高温氧化-化学发光检测法（high temperature oxidation ＆ chemiluminescence, HTO-CL）进行水质总氮（TN）的在线测定。总氮浓度（CN）与化学发光的强度（IN）呈良好的线性关系,线性区间为0．05～100mg／L。对真实水样采用本方法进行测定,其结果与国标方法相符,回收率在90％～110％之间。以本方法为工作原理的TN-2000型总氮测定仪可用于地表水质及污水的在线监测。     

肾上腺素在对甲苯磺酸修饰电极上的电化学行为

研究了对甲苯磺酸在玻碳电极上电化学聚合的条件及修饰电极的电化学特性, 发现该聚合膜对肾上腺素的电氧化有显著的催化作用, 在pH 7.0的磷酸盐缓冲溶液中, 搅拌富集40 s后, 用循环伏安法对肾上腺素进行了测定, 线性范围: 4.05×10-7～9.45×10-6 mol/L, 检出限为3.2×10-8 mol/L. 对2.0×10-6 mol/L肾上腺素平行测定7次相对标准偏差为2.4%. 该电极有效地排除了抗坏血酸的干扰, 具有良好的稳定性和重现性.     

电磁感应在线消化-原子荧光光谱法测定茶水中的砷

利用电磁感应加热原理,研制了在线消化还原、氢化物发生原子荧光法分析装置,实现了茶水中As量的在线测定.对各种实验参数和干扰情况进行了研究.方法的检出限为0.063 μg/L;样品分析精密度(RSD)为2.5%(n=11).