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Aerobic oxidation of 5-hydroxymethylfurfural (HMF) effectively catalyzed by a Ce0.8Bi0.2O2-delta supported Pt catalyst at room temperature
No full textThe oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was efficiently catalyzed when Pt nanoparticles (NPs) were supported onto a Ce0.8Bi0.2O2-delta solid solution. 98% yield of FDCA was achieved within 30 min at room temperature and the catalyst was reused five times without much loss of FDCA selectivity. It is the first report on the oxidation of HMF, an alcohol and an aldehyde, effectively catalyzed by a ceria-based material supported Pt catalyst. The individual properties of the Pt NPs and the ceria-based support were retained and not affected after their combination. The superior oxygen activation ability of the Bi-doped ceria thoroughly changed the performance of the ceria supported Pt catalyst. Pt NPs were responsible for the formation of the Pt-alkoxide intermediate, followed by beta-H elimination with the help of hydroxide ions. Bi-containing ceria accelerated the oxygen reduction process because of the presence of a large amount of oxygen vacancies and the cleavage of the peroxide intermediate promoted by bismuth. These specific functions were well incorporated during the catalytic oxidation cycle, leading to the generation of the highly efficient Pt/Ce0.8Bi0.2O2-delta catalyst for HMF oxidation at room temperature
Synthesis of hollow PdRuCo nanoparticles with enhanced electrocatalytic activity
No full textHerein, a simple one-pot method for the synthesis of trimetallic PdRuCo hollow nanocrystals is developed. PdRuCo hollow nanocrystals with different compositions can be obtained through a wet-chemical route, just by using a sacrificial Co nanoparticle template. The prepared nanomaterials have been analyzed by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, etc. The prepared PdRuCo nanospheres possess an alloyed nanostructure and with an average diameter of about 49 nm. The prepared nanocrystals show much better catalytic activity for ethylene glycol and glycerol electrooxidation than that of a commercial Pd/C catalyst. The reduced cost and enhanced catalytic activity of the as-prepared Pd-based materials allow them to possess great potential applications in direct fuel cells
稀土发光材料的研究进展
Get PDF稀土发光材料已在众多领域获得广泛的应用,并且已成为稀土应用的主要领域之一。本文归纳了白光LED用稀土荧光粉、稀土光转换材料、稀土上转换发光材料、稀土纳米发光材料、真空紫外发光材料、稀土配合物电致发光材料和稀土闪烁体等的研究最新进展,并对未来发展趋势进行了展望
含嘧啶聚酰亚胺的制备及其粘结性能
Get PDF综合2,5-二氨苯基嘧啶(PRM)的刚性结构特征和配位化学特征以及二苯醚二胺(ODA)的柔性结构特征,制备出一系列性能可控的含嘧啶聚酰亚胺.含嘧啶聚酰亚胺的玻璃化转变温度、热稳定性、拉伸强度和模量等,均随聚酰亚胺中PRM比例的升高而增加.但热膨胀系数却随PRM比例的增加而降低,当PRM和ODA的比例为1∶1时,热膨胀系数为17×10-6K-1,与铜箔的热膨胀系数一致,可与铜箔形成尺寸稳定的无胶挠性覆铜板;同时,这一比例的含嘧啶聚酰亚胺与铜箔的粘结强度也达到最高(17.3 N·cm-1).这种含嘧啶聚酰亚胺的性能可以满足无胶挠性印制电路对基底膜材料的尺寸稳定性和粘结性能的要求
聚乙烯树脂的连续自成核与退火热分级实验参数优化及其与逐步结晶热分级对比
Get PDF以支化聚乙烯树脂为研究对象,研究连续自成核与退火热分级实验中,初始温度点(Ts)、升温降温速率、温度间隔(ΔT)和等温时间等实验参数对分级结果的影响,得到了一系列优化的实验参数或范围,为连续自成核与退火热分级方法的实际应用推广提供参考.并将连续自成核与退火(SSA)和逐步结晶(SC)两种热分级的实验结果进行了比较
基于聚多巴胺纳米粒子的荧光共振能量转移法检测microRNA
Get PDF基于聚多巴胺纳米粒子(PDA NPs)对Cy5标记单链DNA(Cy5-ssDNA)探针的荧光猝灭效应以及脱氧核糖核酸酶Ⅰ(DNaseⅠ)选择性切割DNA/RNA杂合结构中单链DNA的特性,建立了一种用于微小核糖核酸(miRNA)检测的新型恒温信号放大方法.在优化的实验条件下,体系的相对荧光强度(FR)与miR-21浓度的对数值成正比;对miR-21检测的线性范围为10 pmol/L~100 nmol/L,检出限达7 pmol/L.血清加标实验结果表明,该方法可用于生理环境下miR-21的检测
锑基双钙钛矿氧化物的研究进展
Get PDF系统地总结了双钙钛矿氧化物的晶体结构特点,根据阳离子有序性的不同将双钙钛矿材料分为3类,即岩盐有序、柱状有序和层状有序,并分析了各类有序的形成条件;从B位含有非磁性阳离子的角度入手,介绍了锑基双钙钛矿氧化物的晶体结构特点及其易获得高度B位岩盐有序的机制,并以几种典型的锑基双钙钛矿氧化物为例讨论了该类氧化物的磁、电性质,特别是B位有序度等晶体结构的改变对该类氧化物物理性质的影响。最后介绍了关于A位为不同稀土离子、B位含锑双钙钛矿氧化物的最新研究工作,研究结果表明随着A位稀土离子的替换介电常数ε’值呈单调递减的趋势,说明镧系收缩抑制了过渡金属离子之间的3d电子的跃迁从而抑制极化畴的翻转;对于B位为不同过渡金属元素的化合物,介电常数ε’值按照磁矩减小的趋势呈单调递减规律,反映了磁性与介电性质之间存在着一定的耦合关系,这对更加深入地研究和探索双钙钛矿氧化物材料的磁电性质提供了有价值的参考信息
一种新型室温固化、耐高温环氧树脂体系及其性能
No full text采用1-己基-3-甲基咪唑四氯化铁盐（[C6mim]FeCl4）与混合胺复配室温（20℃）固化双酚A型环氧树脂E-51,并与其它脂肪胺类室温固化E-51体系在力学性能、热性能、耐老化性能方面的数据进行了比较,同时分析了[C6mim]FeCl4不同添加量对固化体系性能的影响,结果显示:[C6mim]FeCl4/混合胺复配室温固化E-51体系的室温拉伸强度可达90 MPa,高温（120℃）下也保持了良好的力学性能,热失重（5%）分解温度为310℃,200℃老化7 d后,拉伸强度为28 MPa,是一种可在高温下使用的新型环氧树脂室温固化体系
Cf/SiC复合材料表面LaMgAl11O19/Er2Si2O7涂层的制备和抗氧化性能研究
No full text采用高温固相反应法合成Er2Si2O7和LaMgAl11O19（LMA）粉末,用大气等离子喷涂（atmospheric plasma spraying,APS）方法在碳纤维增强的碳化硅复合材料（Cf/SiC）基体表面依次制备Si或Er2Si2O7和LMA涂层,形成LMA/Er2Si2O7和LMA/Er2Si2O7/Si两种结构的抗氧化涂层,探索了LMA和Er2Si2O7在高温下的化学相容性以及涂层在静态空气中对基体的抗氧化保护性能。研究结果表明,两种涂层对基体都有良好的抗氧化保护作
NIR触发的两亲性含糖聚合物修饰的纳米金棒的制备及应用
No full text通过配体交换的方法成功将含糖聚合物PGAMA14-PCL32-SH接枝到纳米金棒的表面(Gly@AuNRs).借助X-射线光电子能谱(XPS)、动态光散射(DLS)、热重分析(TGA)等对Gly@AuNRs进行了表征.为了得到药物控释所需要的合适的实验条件,研究了近红外光照射下Gly@AuNRs在水溶液中的光热转换行为.用Gly@AuNRs包裹药物姜黄素(CUR),研究了药物的体外释放,发现近红外光能有效控制药物的体外释放.细胞实验结果表明含糖聚合物的接枝大大提高了纳米金棒的生物相容性.因此,Gly@AuNRs复合材料能够作为生物相容性载体材料,并实现近红外光触发的药物的可控释放