化学液相还原法制备零价铁纳米颗粒研究进展及展望

零价铁纳米颗粒磁性能卓越应用潜力巨大,已受到广泛关注。本文综述了采用化学液相还原法制备纳米铁的研究进展。总结了纳米铁制备过程中容易团聚和氧化两个关键问题:使用稳定剂可降低纳米铁团聚程度,表面包覆外壳可抑制纳米铁深度氧化。并详细介绍了水合肼、多元醇、碱金属硼氢化物3种常用还原剂的还原性能及其在制备过程中表现出的优缺点。提出化学液相还原制备纳米铁技术的发展依赖于对稳定剂与包覆剂的深入研究,对于还原反应工艺流程的工业化放大以及如何降低成本。     

聚乙烯吡咯烷酮及鞣酸对纳米金制备的影响

在经典Frens法制备金纳米粒子过程中引入聚乙烯吡咯烷酮(PVP)及鞣酸作为保护剂,制备出金纳米粒子并考察了保护剂用量、反应温度和搅拌速度对制备出的金纳米粒子的影响;在制备好的金纳米粒子表面,通过化学还原方法沉积生长银层。利用UV-Vis分光光度计,透射电子显微镜(TEM)等手段对得到的样品进行表征。结果表明:两种保护剂的存在可提高粒子的稳定性、单分散性、粒径分布均匀且在7 nm~25 nm内可控,重现性好;Au/Ag核壳结构复合粒子在适当的摩尔比范围内粒径可控且均匀稳定。     

细菌和颗粒浓度对纳米零价铁材料的柱迁移性影响

通过填充柱实验研究了氢自养反硝化细菌(HB)和不同颗粒浓度对纳米零价铁(nZVI)和壳聚糖包覆纳米零价铁(CS-nZVI)在多孔介质中迁移的影响。利用穿透曲线考察了纳米零价铁材料的迁移性能。结果表明,颗粒浓度(0.2,0.5,1 g/L)对nZVI在多孔介质中的迁移性没有显著影响;CS-nZVI在低浓度(0.2 g/L)下有较好的迁移性。CS-nZVI在不同颗粒浓度下的穿透率均高于nZVI,显示出较好的迁移性能。纳米零价铁悬浮液中加入细菌,颗粒迁移性增强,其中1/3 HB条件下对nZVI和CS-nZVI迁移的促进作用更明显;细菌存在条件下,nZVI迁移性能随颗粒浓度增加而增强,而CS-nZVI的迁移性与颗粒浓度不呈正相关关系。     

负载型Pt@Pd纳米粒子的制备与催化性能研究

用聚N-乙烯基乙酰胺接枝聚丙烯腈/聚苯乙烯(PNVA-g-PAN/PSt)聚合物微球为载体,H2PtCl6为金属源,无水乙醇为还原剂,将配位的Pt4+离子原位还原成为Pt纳米粒子负载于PNVA-g-PAN/PSt微球表面,进而在Pt纳米粒子上将Pd2+还原,制备了负载型Pt@Pd纳米粒子。用透射电子显微镜(TEM)对所制负载型Pt@Pd纳米粒子的形态与尺寸大小进行表征,结果显示,Pt@Pd纳米粒子均匀分布在聚合物微球表面;TEM和X-射线衍射结果显示,Pt@Pd纳米粒子的平均粒径随H2PtCl6与PdCl2比例的增加出现先增大后减小的变化趋势,粒径在9~22.2 nm之间;对肉桂酸产率的测定结果显示,该负载型Pt@Pd纳米粒子对碘代苯与丙烯酸交叉偶联反应有良好催化活性。     

纳米TiO_2的制备及其光催化性能

以钛酸四丁酯为原料,采用溶胶 凝胶法制备了纳米级TiO2颗粒,通过甲苯在样品上的光催化氧化过程评价了样品的光催化活性。考察了制备过程中的焙烧温度对样品颗粒的晶型、粒径和光催化性能的影响。X射线衍射结果表明,焙烧温度低于500℃时得到的样品都是锐钛矿型TiO2,700℃下得到的已基本是金红石型;随着焙烧温度的升高样品的粒径增大,光催化活性下降;甲苯在TiO2上的气相光催化氧化符合一级反应规律。     

聚醚砜/纳米零价铁复合膜制备及性能

采用共混法、金属配位法和液相还原法等方法成功制备了聚醚砜/纳米零价铁(PESU/NZVI)复合膜材料,通过扫描电子显微镜、X射线衍射、X射线光电子能谱和傅立叶变换红外光谱对PESU/NZVI复合膜进行了分析表征,考察了NZVI含量对PESU/NZVI复合膜性能的影响.结果表明,PESU/NZVI复合膜表面主要元素为C,...     

零价铁体系预处理硝基苯废水机理的研究

研究了三种零价铁体系在不同pH值条件下对硝基苯废水处理的效果,评价了硝基苯在铜电极和石墨电极上的电还原特性,提出了催化铁内电解法和传统铁屑法处理硝基苯废水反应机理的区别,并归纳了不同pH值条件下硝基苯的主要还原途径。结果表明:酸性条件下,三者的处理效果相差不大;中性和碱性条件下,铁粉法的处理效果显著下降,而催化铁内电解法使传统铁屑法处理硝基苯废水的效率平均提高了20%左右。     

聚乙烯吡咯烷酮/银纳米粒子/β-环糊精复合纳米纤维的制备

采用液相原位还原法,在聚乙烯吡咯烷酮(PVP)/乙醇溶液中加入硝酸银,制得PVP/银纳米粒子/乙醇溶液,然后加入一定量的PVP/氨水溶液,再加入β-环糊精获得复合溶液。通过静电纺复合溶液得到含有银纳米粒子的三组分复合纳米纤维。利用紫外光谱法对溶胶内的银纳米粒子进行了表征,运用扫描电子显微镜对纤维的形貌和结构进行了表征,并以大肠杆菌为细菌模型,测试了样品的抗菌性能。     

纳米粒子增强碳纤维复合材料界面性能的研究进展

详细介绍了纳米粒子改性碳纤维的方法、原理及其在增强碳纤维复合材料界面性能方面的研究进展,并指出了纳米粒子改性碳纤维复合材料界面性能存在的相应问题,为提高碳纤维复合材料界面性能的研究提供了参考。     

纳米零价铁的制备及应用研究进展

主要综述了新型水处理材料纳米零价铁及其特点、常用制备方法(高能球磨法、液相还原法),以及该材料的改性和在污废水处理中的应用等;最后对纳米零价铁的发展趋势进行了展望,对纳米零价铁深入研究的领域和亟待解决的问题进行了分析。     

埃洛石负载的纳米金可控制备及对环己烷选择性氧化的催化性能

埃洛石纳米管（HNTs）是一类具有独特物理结构和化学性质的天然黏土化合物,本文以经过提纯和聚二烯丙基二甲基氯化铵溶液（PDDA）改性的埃洛石为载体,将预先制备的粒径可控的金溶胶负载到改性埃洛石（PHNTs）表面得到负载型的纳米金颗粒,通过调节氯金酸前体的浓度和用量,实现了对负载型纳米金尺寸的有效调控,透射电镜表征结果显示,埃洛石负载的纳米金分散性良好,平均粒径分别处于2nm以下、2～5nm和5nm以上。以环己烷的液相选择性氧化为模型反应,评价了所制备的不同尺度负载型纳米金粒子的活性和对环己醇和环己酮的选择性。结果表明：纳米金颗粒的平均粒径处于2～5nm时,表现出最好的催化活性和选择性,在170℃和2.0MPa下反应2h,环己烷的转化率可达10.29%,环己醇和环己酮的选择性达85.75%,优于该反应体系使用的工业催化剂对活性和选择性的指标要求。此外,X射线光电子能谱仪表征结果显示,当埃洛石负载的纳米金平均粒径处于2～5nm时,金元素主要以Au⁰ 的形式存在。     

Tunable synthesis of SiO2-encapsulated zero-valent iron nanoparticles for degradation of organic dyes

A series of nanocomposites consisting of zero-valent iron nanoparticles (ZVI NPs) encapsulated in SiO₂ microspheres were successfully synthesized through a successive two-step method, i.e., the wet chemical reduction by borohydride followed by a modified Stöber method. The as-synthesized nanocomposites were characterized using X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer, and inductively coupled plasma-atomic emission spectrometer. The catalytic performance of SiO₂-encapsulated ZVI nanocomposites for the degradation of organic dyes was investigated using methylene blue (MB) as the model dye in the presence of H₂O₂. The results showed that the degradation efficiency and apparent rate constant of the degradation reaction were significantly enhanced with increased ZVI NPs encapsulated in SiO₂ microspheres, whereas the dosage of H₂O₂ remarkably promoted degradation rate without affecting degradation efficiency. The content-dependent magnetic property ensured the excellent magnetic separation of degradation products under an external magnet. This strategy for the synthesis of SiO₂-encapsulated ZVI NPs nanocomposites was low cost and easy to scale-up for industrial production, thereby enabling promising applications in environmental remediation.     

Reductant-free synthesis of magnetoplasmonic iron oxide-gold nanoparticles

Stable suspensions of spherical 10–15 nm superparamagnetic iron oxide nanoparticles (SPIONs) have been synthetized by co-precipitation, stabilized with citric acid, surface functionalized with aminopropyltriethoxysilane (APTES) and finally decorated with ultra-small gold nanoparticles (GNPs) by in situ reduction of a soluble gold salt (HAuCl₄), obtaining well dispersed SPIONs-GNPs colloids.The morphology, size and stability of the SPIONs-GNPs suspensions have been controlled by adjusting the molar ratio of the reagents (Fe/HAuCl₄ and Fe/APTES). The synthesis route differs from that typically found in literature, using tunable chelating layer modifications (such as citric acid and –NH₂ groups) of the magnetic core, depositing GNPs on the amine-functionalized iron oxide surface without the use of a specific reducing agent, and tuning the process pH and temperature. An explanation of how the different chemical species involved in the synthesis route could be responsible for the reducing action has been provided. The SPIONs-GNPs colloids have been characterized after each synthesis step by Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS), Fourier transform infrared spectroscopy (FTIR), ζ Potential measurements, magnetic measurements with a vibrating-sample magnetometer (VSM) and UV–VIS spectroscopy. The SPIONs-GNPs colloids showed magnetoplasmonic behaviors since they maintained the plasmonic properties of GNPs and the superparamagnetic response of iron oxide NPs.     

Olive leaves extract mediated zero-valent iron nanoparticles: synthesis,characterization, and assessment as adsorbent for nickel (II) ions in aqueous medium

Abstract

Zero-valent iron nanoparticles (NZVI-NPs) possess significantly high surface area and volume ratio, and this unique surface characteristic has enhanced reactivity to their adsorption potential. In this work, a bio-matter (Olive leaves extract) is deployed as a nature-inspired reducing agent for the synthesis of NZVI-NPs. The particle size of NZVI-NPs has been determined using particle sizer. The NZVI-NPs are characterized using analytical and morphological techniques such as ultraviolet???visible spectroscopy (UV???vis), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. The average crystalline size of NZVI-NPs are around 30–60?nm while maximum adsorption is at 225?nm. XRD spectrum shows two distinctive diffraction peaks at 25.40° and 42.50° corresponding to lattice plane value indexed at (200) and (222) planes of faced centered cubic (FCC). At optimized experimental conditions, NZVI-NPs show 97% removal efficiency of Ni⁺² ions from aqueous solution. The equilibrium time has been found to be 55?min and the monolayer maximum adsorption capacity is 139.5?mg/g. Kinetically, Ni⁺² ions adsorption has been modelled using various physical isotherms and the data best fitted Freundlich isotherm model and pseudo-first-order kinetic; revealing a maximum adsorption capacity of 139.5?mg/g at 25?±?3?°C and pH of 6.5. Desorption tests affirm the possibility of recovering reasonable amount of NZVI-NPs after used. The specific surface area of the NZVI-NPs sample measured by BET analysis is 21.9967 m²/g indicating a high adsorption capacity.     

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe₃O₄ nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe₃O₄ nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.     

Generation and characterization of catalytic nanocomposite materials of highly isolated iron nanoparticles dispersed in clays

Nanostructured metallic iron particles in montmorillonite matrix have been prepared at ambient temperature through iron intercalation followed by reduction of resulting iron pillared montmorillonite with potassium borohydride. The resulting nanocomposites have been characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), UV–VIS-diffuse reflectance spectrometer (UV–VIS). The catalytic performances of resulting nanocomposites have been evaluated by probe phenol oxidation reaction with hydrogen peroxide. The results reveal that the nanosized iron polyoxocations intercalated clays can be successfully obtained by conventional synthesis of pillared clays, and after reduction of pillars, the highly dispersed zero-valent iron nanoparticles in clay matrix with diameter in the range of 3–10 nm can be successfully yielded. Over the nanocomposites catalyst prepared at a molar ratio of [CO ₃ ²⁻ ]/[Fe³⁺] = 0.5, the catalytic conversion of phenol oxidation is 49.5% with a 67.4% of selectivity to carbon dioxide and tar. The iron species dispersed in clay matrix may provide the catalytic active sites and the size of iron species has an effect on selectivity. More highly isolated iron nanoparticles dispersed in clays could lead to higher catalytic deep oxidation.     

蒙脱石搭载纳米Ni-Fe超声降解十溴二苯醚

为解决传统纳米零价铁（nZVI）降解污染物时易氧化团聚、反应活性低的问题,通过改性手段制备并表征了蒙脱石搭载纳米Ni-Fe（Ni-Fe/蒙脱石）等复合材料,考察污染物和纳米材料质量浓度、温度、溶液初始pH、超声辅助等对其降解十溴二苯醚（BDE-209）的影响,比较nZVI改性前后的降解效果,分析其机理并建立了反应动力学方程。结果表明：最佳反应条件为5mg/L的BDE-209、2g/L的nZVI、温度35℃、pH=3。超声处理10min时BDE-209基本降解完,其表观速率常数（k_obs,0.519min^-1）是震荡处理（0.013min^-1）的40倍、静置处理（0.004min^-1）的130倍。几种材料在10min时对BDE-209的降解率为：Ni-Fe/蒙脱石（99.5%） > nZVI/蒙脱石（85.1%） > 纳米Ni-Fe（64.8%） > nZVI（48.1%） > 蒙脱石（4.1%） > 纳米Ni（1.1%）,120min时k_obs为：Ni-Fe/蒙脱石（0.519min^-1） > nZVI/蒙脱石（0.209min^-1） > 纳米Ni-Fe（0.050min^-1） > nZVI（0.024min^-1）。蒙脱石、纳米Ni及超声本身基本不降解BDE-209。     

Microwave-assisted synthesis and characterization of bioactive chitosan scaffolds doped with Au nanoparticles for mesenchymal stem cells culture

In this work we present a novel strategy for chitosan-based scaffolds. Chitosan is a versatile biopolymer obtained from waste biomass known of its favorable biological properties. Thus it can replace other polymers in the preparation of bioactive scaffolds. To increase its durability chitosan can be crosslinked into form of the hydrogel yet application of toxic crosslinkers may lead to loss of biocompability. Mesenchymal stem cells can be used in cell therapy for advanced wound treatment. However their culture requires special biomaterials application. In this article a novel microwave-assisted synthesis method for bioactive chitosan scaffolds is presented.     

Magnetite nanoparticles: Electrochemical synthesis and characterization

Magnetite (Fe₃O₄) nanoparticles (NP) with sizes between 20 and 30 nm have been obtained by Fe electrooxidation in the presence of an amine surfactant, which acted as a supporting electrolyte and coating agent, controlling particle size and aggregation during the synthesis. The effect of different parameters on the nature and size of the particles as well as the mechanism of formation of the particles have been studied by different techniques. It was concluded that, under the electrochemical conditions used in this work, the NP mean size was found to be constant at around 20 nm when the electrooxidation current density is increased from 10 to 200 mA cm⁻². However, when the potential is over 6 V, particle size decreases from 30 to 20 nm and metallic iron appears as an impurity. The mechanism of particles formation has being clarified and the critical effect of the distance between electrodes for obtaining magnetic iron oxide nanoparticles has been understood. Finally, the presence of an electrostatic adsorbed surfactant coating the particles allows the functionalization of the particles easily by exchange reaction with biomolecules of interest, which makes this material very promising for future application in biotechnology.     

SiO_2/TiO_2复合纳米粒子的可控制备及表征

以聚丙烯酸(PAA)为模板,采用正硅酸乙酯(TEOS)水解法制备了SiO_2微球,在体系中加入钛酸四丁酯(TBOT),水解后在SiO_2表面自组装一层TiO_2,煅烧产物获得SiO_2@TiO_2空心球;通过TEM、XRD、固体紫外分光光度计对SiO_2@TiO_2的粒子形貌尺寸、晶型、紫外吸收特性等进行表征。结果表明,900℃下煅烧的SiO_2@TiO_2紫外屏蔽效果最好。为抑制TiO_2的光催化活性,在SiO_2@TiO_2表面再包覆一层SiO_2,得到SiO_2@TiO_2@SiO_2微球,具有抗紫外线、防沉降、对皮肤友好等优点。包覆之后的SiO_2@TiO_2@SiO_2三层结构仍具有良好的紫外屏蔽效果。