Silica gel-mediated hydrohalogenation of unactivated alkenes using hydrohalogenic acids under organic solvent-free conditions

Silica gel-mediated hydrochlorination of unactivated alkenes using 35% hydrochloric acid under organic solvent-free conditions proceeded to give the corresponding chlorides in good yields. Hydrobromination or hydriodination using 47% hydrobromic acid or 55% hydriodic acid afforded the corresponding halides, respectively. Silica gel could be recycled five times without any significant loss of activities.     

Development of an electrophoretic method based on nanostructured materials for HbA1c determination

Glycosylated hemoglobin (HbA1c) detection is performed routinely in hospitals as it is the most widespread confirmatory diagnosis of diabetes mellitus. Here we present a novel CE method for measuring HbA1c by introducing silica nanoparticles (NPs) modified with a boronic acid derivative (sugar loadings of 51 ± 2 μg/mg) as pseudo‐stationary phase. Before the sample injection, SiO₂NP─B(OH)₂ were introduced via pressure. Electrophoretic separation was explored through variation of the buffer pH and separation voltage, being the best separation, resolution and shorter separation time achieved with a 25 mM phosphate buffer pH 6.5. The calibration curve obtained was expressed as Area = 182.05%⁻¹ × HbA1c − 377.02; R² = 0.9826, using a UV/VIS absorbance detector at 415 nm (diode array). No interferences were observed from carbamylated or acetylated hemoglobin and the method shows a noteworthy stability. A paired t‐test was applied to compare the developed CE method with a commercial HbA1c test and no significant variations have been observed at a 90% significance level.     

Investigations of the local distortions and EPR parameters for Cu2+ in xNa2O‐(30–x)K2O‐70B2O3 (5 ≤ x ≤ 25 mol%) glasses

The local distortions and electron paramagnetic resonance parameters for Cu²⁺ in the mixed alkali borate glasses xNa₂O‐(30–x)K₂O‐70B₂O₃ (5 ≤ x ≤ 25 mol%) are theoretically studied with distinct modifier Na₂O compositions x. Owing to the Jahn–Teller effect, the octahedral [CuO₆]¹⁰⁻ clusters show significant tetragonal elongation ratios p ~19% along the C₄ axis. With the increase of composition x, the cubic field parameter Dq and the orbital reduction factor k exhibit linearly and quasi‐linearly decreasing tendencies, respectively, whereas the relative tetragonal elongation ratio p has quasi‐linearly increasing rule with some fluctuations, leading to the minima of g factors at x = 10 mol%. The composition dependences of the optical spectra and the electron paramagnetic resonance parameters are suitably reproduced by the linear or quasi‐linear relationships of the relevant quantities (i.e., Dq, k, and p) with x. The above composition dependences are analyzed from mixed alkali effect, which brings forward the modifications of the local crystal‐fields and the electronic cloud distribution around Cu²⁺ with the variation of the composition of Na₂O.     

聚多巴胺功能化硅胶沉积单分散Pd纳米粒子的简易原位合成及用作醇需氧氧化反应的多相可循环使用的纳米催化剂（英文）

本文报道了一种不使用任何稳定剂或还原剂,原位合成硅胶/聚多巴胺复合物(SiO_2/PDA)负载的Pd纳米颗粒(Pd NPs)的简易方法.该方法先将PDA涂覆的SiO_2颗粒浸在Pd镀液中,然后利用PDA中含N基团的还原能力将Pd物种原位还原为纳米簇合物.并采用高分辨透射电镜、前场扫描电镜、能量散射谱、X射线衍射、X射线光电子能谱、诱导耦合等离子体和红外光谱等手段对所得纳米复合物的结构、形貌和物化性质进行了表征.被PDA基团锚合的Pd NPs具有显著的小颗粒(30–40 nm)特性.作为一个可循环使用的纳米催化剂,SiO_2/PDA/Pd NPs在醇的需氧氧化反应中表现出高活性.另外,催化剂经回收和多次重复使用时未出现明显的失活.     

Base-catalyzed reactions enhanced by solid acids: Amine-catalyzed nitroaldol (Henry) reactions enhanced by silica gel or mesoporous silica SBA-15

The reactions of various aldehydes with CH₃NO₂ catalyzed by Et₃N, n-C₆H₁₃NH₂, and Me₂N(CH₂)₂NH₂ were accelerated by the addition of silica gel to give aromatic (aliphatic) β-nitroalcohols, aromatic nitroalkenes, and aromatic 1,3-dinitroalkanes, respectively. Mesoporous silica SBA-15 showed higher activity than silica gel for the synthesis of aromatic nitroalkenes by the reactions of the corresponding aldehydes with CH₃NO₂ catalyzed by n-C₆H₁₃NH₂.     

溶胶-凝胶法制备掺Sm3+的SiO2玻璃的结构及发光性能

利用溶胶-凝胶技术制备了掺不同量Sm3+和不同退火温度下的SiO2凝胶和玻璃,通过三维荧光光谱、激发光谱、发射光谱的测试,确定了Sm3+在SiO2凝胶玻璃中的最佳激发波长为360 nm,最强发射波长为610 nm,激发光谱的峰位置在360、393、464 nm处,发射光谱的峰位置在578、591、595、610、732nm处,分别归属于4G5/2-6H5/2、4G5/2-6H7/2、4G5/2-6H11/2跃迁,并证明当掺杂量达到1.15%时,Sm3+的发光最强,当Sm3+的掺杂量超过1.15%时,发生浓度猝灭效应.     

掺Tb-硅基发光材料制备过程中结构及发光性能

采用溶胶-凝胶技术 ,制备了不同退火温度下掺 Tb3＋的 SiO2玻璃 ,掺 Tb3＋的凝胶玻璃在 448,544,585,620 nm显示 Tb3＋的 5D4- 7FJ(J=3,4,5,6)的特征发光光谱 .通过不同退火温度下样品的激发光谱、发射光谱、红外光谱、远红外光谱及差热-热重谱研究了掺 Tb3＋的硅基材料由凝胶向玻璃转变过程中的结构变化及对 Tb3＋发光性能的影响 .结果显示 ,在 50～ 100℃退火温度下 ,凝胶大部分吸附水分子被除去 ,在 150～ 500℃退火温度区 ,是凝胶向玻璃转变的主要结构变化区 ,并且其发光强度也明显增加 ,到 800℃时趋于稳定 .这些现象得出一个结论 ,Tb3＋的发光跃迁被 O－ H基强烈猝灭而随退火温度的升高而加强 .     

Use of Different Salt Solutions in Salting-Out TLC of Co(III) Complexes on Silica Gel

Saturated aqueous solutions of 28 different salts have been studied as a potential mobile phases for salting-out thin-layer chromatography, on silica gel, of a series of four mixed bis-aminocarboxylato cobalt(III) complexes. In addition, by linear regression analysis of chromatographic data obtained for fifteen mixed aminocarboxylato Co(III) complexes (four series) with solutions of ammonium chloride, three alkali metal chlorides, and four alkaline earth metal chlorides, four linear dependences previously established on different adsorbents with (NH₄)₂SO₄ solutions were confirmed. The qualities of the separations achieved with the salts were compared and Li⁺, Mg²⁺, and Ca²⁺ chlorides are proposed as the most suitable.     

醋酸乙烯酯在硅橡胶上的辐射接枝研究

研究了不同溶剂中的醋酸乙烯酯在硅橡胶上的辐射接技状况及接枝后硅橡胶表面结构情况．结果表明：（１）在硅橡胶－乙酸乙酯－醋酸乙烯酯体系中，接枝有自加速效应；（２）适量加入对苯二酚，接枝诱导期延长，接枝速率下降，凝胶效应消失，辐射接技经验关联式为ＲＰ＝０．２７×［Ｄ］（－０．５６０）×［Ｉ］（０．４９０）×［Ｃ］（０．９２０），接核反应为扩散控制反应；（３）不同的溶剂对硅橡胶接枝有不同的影响，如甲醇发生敏化作用，提高接枝速率，而苯发生惰化作用，降低接枝速率；（４）在合适的甲醇和苯配比时，接枝反应几乎恒速进行，用扫描电镜（ＳＥＭ）观察断面，接枝区比较均一，出现微相分离．     

中低压柱层析分离儿茶素的研究

采用全自动中低压柱层析制备色谱分离儿茶素,原料为含量高于85％的茶多酚,分别以硅胶、C18(十八烷基键合相硅胶)作为吸附剂,应用HPLC对分离产物进行鉴定.结果表明,以硅胶作为吸附剂时,甲醇和氯仿溶液梯度洗脱,得到纯度为96.3％的EGCG,得率32％;以C18作为吸附剂时,甲醇和水溶液梯度洗脱,得到90％以上纯度的EGCG、EC、ECG、CG 4种儿茶素,得率分别为28.8％、7.7％、17.0％、1.8％.