Experimental methods in chemical engineering: X‐ray photoelectron spectroscopy‐XPS

X‐ray photoelectron spectroscopy (XPS) is a quantitative surface analysis technique used to identify the elemental composition, empirical formula, chemical state, and electronic state of an element. The kinetic energy of the electrons escaping from the material surface irradiated by an x‐ray beam produces a spectrum. XPS identifies chemical species and quantifies their content and the interactions between surface species. It is minimally destructive and is sensitive to a depth between 1–10nm. The elemental sensitivity is in the order of 0.1 atomic %. It requires ultra high vacuum ( Pa) in the analysis chamber and measurement time varies from minutes to hours per sample depending on the analyte. XPS dates back 50 years ago. New spectrometers, detectors, and variable size photon beams, reduce analysis time and increase spatial resolution. An XPS bibliometric map of the 10 000 articles indexed by Web of Science^[1] identifies five research clusters: (i) nanoparticles, thin films, and surfaces; (ii) catalysis, oxidation, reduction, stability, and oxides; (iii) nanocomposites, graphene, graphite, and electro‐chemistry; (iv) photocatalysis, water, visible light, and ; and (v) adsorption, aqueous solutions, and waste water.     

Boronic acid-functionalized nanoparticles: synthesis by microemulsion polymerization and application as a re-usable optical nanosensor for carbohydrates

Translucent boronic acid-carrying nanolatexes are prepared by copolymerisation of vinylbenzyl chloride in microemulsion followed by post functionalisation with 3-aminophenylboronic acid. The diol binding capacity and selectivity of the phenylboronic acid remain unchanged after anchoring to polymer nanoparticles (16 nm diameter, 0.22 mmol/g). The binding of a catechol dye, Alizarin Red S (ARS), to the boronic acid-carrying nanoparticles affords a colored, stable, nanolatex which is used for the selective visual detection of fructose in a competitive assay. The binding of fructose at pH 8.2 is readily evidenced by a color change and monitored by UV/Vis spectroscopy. The nanosensor can be regenerated in acidic medium. The entrapment of the nanolatex in a dialysis cell provides a re-usable support for binding and optical detection.     

纳米粒子/环氧树脂复合材料的固化动力学研究

在纳米Al2O3、Si3N4、SiC填充环氧树脂复合材料体系中,纳米粒子表面活性及粒子与环氧树脂之间的相互作用影响着环氧树脂的固化过程.本文利用傅立叶红外光谱表征了纳米粒子与环氧树脂之间的化学作用情况,并利用差视扫描量热仪研究了不同纳米粒子/环氧树脂复合材料的固化动力学.结果表明,具有相对最强表面活性的纳米Al2O3粒子与基体之间的相互作用最强,同时该粒子对环氧树脂固化过程的促进作用最显著.     

低温控制中和水解法制备纳米TiO_2

以Ti(SO4)2为原料,采用低温控制中和水解法制备出了锐钛矿型纳米TiO2粉体。采用XRD和SEM对产品做了表征和分析,并对前驱体晶相的控制作了初步的探讨。     

混凝法去除水中TiO2纳米颗粒

为了探讨混凝法去除水中纳米颗粒的可行性及最佳条件,研究了无机混凝剂（PAC、PFS、PAFC）和有机絮凝剂（CPAM、APAM、NPAM）对TiO₂纳米颗粒的去除效果,并考察了投加量、pH、沉淀时间、水力条件及有机无机复配对TiO₂纳米颗粒去除效率的影响。单独投加PAC、PFS和PAFC时,三者对应的最高去除率分别为92.51%、84.43%、95.66%。单独投加CPAM、APAM、NPAM时三者对应的去除率仅为61.72%、29.06%、55.37%。复配最佳混凝条件为：投加40 mg/LPAC和3 mg/LCPAM,pH值为9,G值143.5/s,沉淀时间15 min,此时,TiO₂纳米颗粒去除率为99.6%。     

甘草次酸修饰的聚天冬氨酸苄酯纳米粒制备及表征

用甘草次酸(GA)修饰可生物降解的聚天冬氨酸苄酯(PBLA),将其制备成纳米粒,考察其作为药物载体的可行性.首先将GA氨基化,以引发L-天冬氨酸-β-苄酯-N-羧酸酐(BLA-NCA)开环聚合,合成不同分子量的材料GA-NH-PBLA,通过1H-NMR、FT-IR对其结构进行表征,GPC显示3种材料的分子量为1 565,3 560,5 550.采用MTT法以人肝癌细胞(HepG2)为对象,评价其作为药物载体的安全性,结果实验表明该材料无细胞毒性.采用乳化-溶剂挥发法制备包载紫杉醇(PTX)的纳米粒,并考察了不同分子量材料GA-NH-PBLA对纳米粒粒径,包封率及载药量的影响.结果显示:分子量为5 550的材料,制得的纳米粒粒径约100 nm,粒径分布均匀,球形度良好,具有良好的缓释作用,表明分子量大的材料更适合作为药物载体.     

磁性催化剂的研究进展

磁性催化剂具有磁响应特征,可利用外磁场将其分离和回收,其应用克服了传统催化剂在分离与回收过程中能耗高、质量损失大等问题,降低了反应成本。因此,对磁性催化剂的研究具有现实意义。重点阐述了磁性催化剂的合成及其在氧化反应、加氢反应、偶合反应等领域的应用研究进展,并对磁性催化剂的发展趋势进行了展望。     

Fe3O4-H2O2类Fenton体系催化降解苯酚

为提出基于新型磁纳米Fe3 O4催化剂的类Fenton体系,采用化学共沉淀法制备磁纳米Fe3 O4,用四甲基氢氧化铵（ TMAH）对所制备的磁纳米Fe3 O4进行表面改性,就Fe3 O4－H2 O2类Fenton体系对苯酚废水的处理效果进行探讨,考察催化剂投量、H2 O2浓度、pH、反应时间等因素对COD和挥发酚去除率的影响．结果表明：磁纳米颗粒平均粒径为30 nm,并在20～100 nm内呈现良好的粒度分布．不同剂量TMAH包覆的3种催化剂经超声预处理后,在室温（13℃）下对50 mg／L苯酚（相当于112 mg／L COD）的降解效果基本一致．当催化剂投量为0．8 mmol／L、H2 O2浓度为2．0 mmol／L、pH为4．5、反应时间180 min时,COD去除率最高可达72％;催化剂投量为0．4 mmol／L、H2 O2浓度为2．0 mmol／L、 pH为4．5、反应时间为90 min时,挥发酚的去除率接近100％．而在重复使用方面,3＃Fe3O4－TMAH（2 mL）催化剂的回用性最好,4次反应COD的去除率分别为73％、29％、28％、26％,挥发酚去除率分别为100％、84％、67％、54％．该类Fenton体系具有不产生多余泥量的优点,且磁纳米催化剂在外磁场作用下可实现快速分离回收．     

Preparation and spectral analysis of gold nanoparticles using magnetron sputtering and thermal annealing

Gold(Au) nanoparticles were prepared on Au-fi lm-coated K9 glass and silicon substrates by direct current(DC) magnetron sputtering and thermal annealing treatment. The effects of substrate material, annealing temperature, and time on morphologies of Au nanoparticles were investigated, and the formation mechanism of Au nanoparticles was discussed. The experimental results indicate that silicon substrate is more suitable for the formation of Au nanoparticles. On a silicon substrate, Au nanoparticles formed with good spherical shapes at temperature over 700 ℃. It was also found by spectral analysis that the fi eld enhancement factor of the island-shaped Au particles was smaller than that of the granular Au particles; the better the spherical shape as well as the smaller the size and spacing of Au particles, the higher the light absorption rate; the absorption peak had a red shift with increasing particle size and spacing.     

Fe^3＋离子修饰的金纳米粒子对DNA的高效吸附

在谷胱甘肽功能化的金纳米粒子表面螯合Fe^3＋离子后,研究了DNA分子在不同p H和盐浓度条件下在粒子表面的吸附和脱附行为。在pH〈4.0的条件下,DNA通过所含的磷酸根基团与粒子表面的Fe^3＋离子产生配位相互作用而吸附到粒子表面,此过程受盐浓度影响不大。当pH〉4.0时,由于溶液中氢氧根离子的竞争作用,使DNA的磷酸根基团不能与Fe^3＋离子配位,此时只能通过静电或氢键作用吸附,但是吸附效率很低。因此,Fe^3＋离子修饰的金纳米粒子只在低p H条件下可以实现对DNA的高效吸附。这种基于配位作用的吸附效率要高于盐桥作用,而且不会受到溶液中盐浓度的影响。