核壳结构纳米粒子

纳米粒子由于具有大量的潜在应用,近年来已引起人们极大的关注。通过表面改性(如制备核壳结构的纳米粒子)可以使其获得更多特殊的性质。本文就最近几年制备壳核结构纳米粒子的方法进行了总结,根据其核、壳的不同材料进行了分类,并对其中某些方法进行了比较。     

二氧化硅-聚丙烯腈核-壳结构复合纳米粒子的制备与表征

以甲基丙烯酸-3-(三甲氧基硅基)丙酯改性的SiO2纳米粒子为种子,采用乳液聚合法制备了粒径分布较窄的SiO2-聚丙烯腈(SiO2-PAN)核-壳结构复合纳米粒子。采用动态光散射、傅里叶红外光谱、透射电镜和扫描电镜表征了复合纳米粒子的粒径及分布、组成、形态和结构,并研究了表面活性剂的加入方式、反应温度及交联剂的引入对制备SiO2-PAN复合纳米粒子的影响。结果表明:SiO2-PAN复合纳米粒子为核-壳结构。采用半连续加入表面活性剂的方法,可以成功抑制乳液聚合中次级粒子的生成。通过增加表面活性剂的初始加入量、加快表面活性剂的补加速率,或降低反应温度,可使SiO2-PAN复合纳米粒子的粒径变小。反应温度的降低以及交联剂的引入使SiO2-PAN复合纳米粒子的表面变得平滑。     

核-壳结构的氯化银/聚丙烯酰胺复合纳米粒子的制备与表征

用反相微乳液作为模板制备了核-壳结构的氯化锯／聚丙烯酰胺(AgCI／PAM)复合纳米粒子。透射电镜(TEM)证实复合粒子为核-壳结构，平均直径约100nm。扫描电子显微镜(SEM)和X射线衍射分析显示，平均粒径约50nm的AgCl均匀分散在聚合物中。FTIR谱图表明：AgO与PAM之间存在较强的相互作用。用能级探洲光谱(Energy Detected Spectrum，EDS)和润湿分散实验比较了不同方法改性的复合粒子的表面结构与润湿性能。     

铝纳米粒子表面引发聚合制备核壳纳米结构

利用硅烷偶联剂引发法制备核壳结构金属铝纳米粒子(Al NPs)@聚合物, 并研究了聚合反应时间和单体浓度对核壳结构尺寸的影响. 首先合成了硅烷偶联引发剂{2-溴-2-甲基-[3-(三甲氧基硅基)丙基]丙酰胺}, 并通过在甲苯中回流的方法, 将其锚定在金属铝纳米粒子表面. 然后, 在粒子表面引发甲基丙烯酸甲酯的原子转移自由基聚合, 形成聚甲基丙烯酸甲酯(PMMA)壳层. 通过核磁共振波谱仪(NMR)和傅里叶变换红外光谱仪 (FTIR)证明了引发剂和PMMA的成功接枝. 透射电子显微镜(TEM)图像表明, PMMA改性后的金属铝纳米粒子的尺寸和形貌基本不变, 且被厚度约为15 nm聚合物壳层完整均匀地包覆. 此外, 利用动态光散射(DLS)进一步揭示了聚合时间和单体浓度对核壳结构水合直径(D_h)的影响, 发现延长聚合时间或增加单体浓度均可显著提高核壳结构尺寸.     

原子级壳层厚度Ru@Pt核壳结构纳米粒子的制备与表征

采用连续多元醇法,以RuCl₃·xH₂O和PtCl₂为前驱体,乙二醇为还原剂,聚乙烯吡咯烷酮为稳定剂的反应体系,并通过调节PtCl₂用量和还原温度成功制备了壳层厚度约为1.5个Pt原子层的单分散Ru@Pt核壳结构纳米粒子,利用透射电子显微镜(TEM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)等分析方法对其微观结构、粒径分布、晶型结构、物相组成进行了表征。 结果表明,该纳米粒子分布均匀且基本为球形,平均粒径约为3.57 nm,其中内核直径约为2.49 nm,外壳厚度约为0.55 nm,壳层金属Pt具有很好的晶型,Pt原子主要为{111}晶面,内核金属Ru与外壳金属Pt互相产生了电子效应使Pt的衍射峰和Ru、Pt的电子结合能产生了一定偏移,并初步研究了有效控制该核壳结构纳米粒子壳层厚度和增强核与壳两种金属之间电子效应的因素,使其有望在催化等领域发挥潜在的应用价值。     

Au/Ag核-壳结构纳米粒子的制备及其SERS效应

随着大量有关表面增强拉曼散射 (SERS)的实验和理论研究的开展 ,金属纳米粒子作为一类重要的 SERS增强介质 ,已引起了人们浓厚的研究兴趣 [1] .而 Au和 Ag作为最常用的活性基底物质 ,更是研究的热点 [2 ,3 ] .最近 ,美国印第安那大学的 Nie等 [4 ] 在单个银纳米粒子上 ,观察到高达 1 0 14 ～ 1 0 15的SERS因子 .同时 ,他们的另外一项工作表明银纳米粒子的形状和大小对 SERS活性有很大影响 [5] .但是 ,由于 Ag溶胶制备的重复性较差 ,且粒度分布不均匀 ,通过控制银颗粒大小而调控 SERS活性是相当困难的[6] .与 Ag相比 ,Au在可见光…     

CeO2@Au核壳结构纳米粒子的合成与性质研究

采用沉淀法制备了球形CeO2纳米粒子,将其作为核粒子溶液,然后向其中滴加四氯合金酸溶液,在CeO2胶体表面利用柠檬酸钠还原[AuCl4]-离子,得到了CeO2@Au核壳结构纳米粒子。TEM分析表明,CeO2纳米粒子分散效果好,粒径为5 nm;CeO2@Au核壳粒子为球形,无团聚,平均粒径为15 nm。XRD分析表明,CeO2@Au核壳粒子为晶型结构,属于立方晶系,CeO2空间群为O5H-FM3M,Au的空间群为Fm-3m。UV-vis分析发现,CeO2@Au核壳粒子在300和520 nm处呈现出两个比较强的吸收峰,分别对应于CeO2胶体溶液的吸收峰和金粒子的表面等离子共振吸收峰。EDS分析了核壳结构CeO2@Au纳米粒子中存在Ce,O和Au 3种元素。XPS分析表明,Ce3d3/2和Au4f电子结合能与标准结合能相比发生了变化,说明CeO2与Au之间存在着相互作用。     

光催化还原制备Au/Ag核壳结构纳米粒子及其修饰电极的电催化性能

以Keggin结构硅钨杂多酸H4SiW12O40(SiW12)为光催化还原剂,通过光化学还原法制备Au/Ag核壳结构纳米粒子. 透射电子显微镜分析显示,所得纳米粒子粒径为30～40 nm,呈均匀分散的球形颗粒,该制备方法的特点是可以较好的避免单金属纳米粒子的形成. 将Au/Ag核壳纳米粒子修饰到具有PVP膜的玻碳电极表面,得到SiW12-(Au/Ag)-PVP多层膜修饰电极. 该修饰电极在0.5 mol/L H2SO4介质中具有良好的电化学响应,在0～-0.75 V电位范围内,出现了3对归属于SiW12的氧化还原峰,且电极性能稳定,灵敏度高. 对H2O2的电催化还原性能明显优于单金属Ag纳米粒子修饰电极,说明Au核的存在可以很好的改善Ag的电催化性能,Au和Ag之间存在相互协同催化作用.     

Ag@Ag2S核壳结构纳米粒子的合成及光热转换性能研究

由于核壳结构的硫化银纳米材料不仅具有特殊的光学、电学性质而且还具有生物相容性,因此Ag@Ag_2S纳米材料的研究受到了国内外学者的高度关注。本课题以硫酸银或硝酸银为银源,以CTAB(十六烷基三甲基溴化铵)或聚乙烯吡咯烷酮为分散保护剂,以葡萄糖、聚乙烯吡咯烷酮或甲酸为还原剂,用硫代硫酸钠对所得的银纳米粒子进行硫化,将产物用SEM和EDS进行分析,证明得到了具有核壳结构的Ag@Ag_2S纳米粒子。最后对所得的Ag@Ag_2S纳米粒子进行光热转换性能研究,表明了用聚乙烯吡咯烷酮做还原剂得到的Ag@Ag_2S纳米粒子光热转换性能最好。     

超顺磁Fe_3O_4@PDA核-壳结构纳米粒子的制备及表征

利用多元醇高温热解法和溶液氧化法制备超顺磁四氧化三铁聚多巴胺核-壳结构纳米粒子(Fe_3O_4@PDA)。采用X射线衍射(XRD)、透射电子显微镜(TEM)、动态光散射(DLS)、傅里叶转换红外光谱(FT-IR)和热重分析(TG)等对Fe_3O_4@PDA的结构、形貌和组成进行表征。采用综合物性测试系统(PPMS)对样品的磁性能进行表征。结果表明:Fe_3O_4@PDA的尺寸可以通过氨水与多巴胺的物质的量之比和反应时间进行调控;当Fe_3O_4@PDA中Fe_3O_4的质量分数约为5%时,具有超顺磁性,磁饱和强度为3.8emu/g,比理论值高出36%。     

SnO2-TiO2薄膜载体对Au-Pt纳米颗粒电化学性能的影响

采用真空镀膜法在玻碳(GC)电极表面修饰SnO2-TiO2薄膜, 在SnO2-TiO2/GC复合电极表面组装Au-Pt双金属纳米颗粒, 制得Au-Pt/SnO2-TiO2/GC复合电极. 通过循环伏安法(CV)研究了SnO2-TiO2薄膜载体对Au-Pt双金属纳米颗粒电化学性能的影响; 采用扫描电镜(SEM)及X射线光电子能谱(XPS)对Au-Pt在SnO2-TiO2薄膜沉积的形貌及结构进行了表征. 研究结果表明, 10 nm的Au-Pt双金属纳米颗粒均匀地组装于SnO2-TiO2薄膜表面; SnO2-TiO2薄膜载体改善了复合电极抗CO中毒能力; Au-Pt双金属合金的形成提高了Pt 对甲醇氧化的电催化能力, SnO2-TiO2薄膜载体又使Pt纳米粒子d空轨道增多, 提高了Au-Pt双金属纳米颗粒的稳定性和催化性能.     

Synthesis of Core-Shell (Pd-Au) Bimetallic Nanoparticles in Microemulsions

Palladium-gold core-shell nanoparticles were synthesized in the aqueous domains of water in oil microemulsions by the sequential reduction of H₂PdCl₄ and HAuCl₄. The nanoparticles were characterized by ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). The UV-vis spectra confirm the presence of palladium nanoparticles after reducing H₂PdCl₄. These particles have been used as seeds for the core-shell particles. UV-vis spectra show that, after reducing HAuCl₄, the surface plasmon absorption of the nanoparticles is dominated by gold, revealing the encapsulation of the palladium seeds. These results agree with crystallographic analysis performed with high-resolution TEM pictures, as well as with selected area electron diffraction. The TEM pictures show the core-shell nanoparticles with an average diameter of 9.1 nm, as compared with 5 nm for the palladium seeds, in good agreement with the used Pd:Au molar ratio.     

团聚铂纳米粒子电极在甲醇氧化中的电催化特性

用H2还原法并以Nafion作为稳定剂合成团聚的Pt纳米粒子，附载于玻碳表面制备电催化剂.透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征结果指出,团聚Pt纳米粒子的平均尺寸约为400 nm.运用电化学循环伏安法(CV)和原位傅立叶变换红外反射光谱（in situ FTIRS）研究甲醇的氧化过程，发现团聚Pt纳米粒子电极具有较高的电催化活性.原位FTIRS研究结果检测到甲醇在所制备的电催化剂上氧化的中间体为线型吸附态CO物种，其红外吸收给出异常红外效应的光谱特征.     

聚合物负载金属纳米粒子型核壳结构催化剂的研究

核壳结构聚合物负载型催化剂因其载体材料独特的结构、形貌和性质而具有优异的催化活性,成为了催化化学领域研究的热点。本文综述了聚合物负载金属纳米粒子型核壳结构催化剂,包括球形聚合物刷负载金属纳米粒子、聚合物中空微球负载金属纳米粒子、聚合物实心微球表面包覆金属纳米粒子等类型催化剂的制备及其相应的催化性能,强调了各类载体的组成和结构特点对催化活性及其稳定性的影响。最后总结了该类催化材料的优势和不足,并对其性能和应用进行了展望。     

Thermal and DMA Characterization of PTFE-PMMA Nanocomposites from Core-Shell Nanoparticles

The thermal and dynamic-mechanical characteristics of three PTFE/PMMA nanoparticle samples are described. The shell forming PMMA, once isolated from the PTFE cores, exhibits a lower thermal stability than the PMMA component in the corresponding nanocomposite under both thermal and oxidative degradation conditions thus indicating a definite, though moderate, thermal reinforcement due to the morphology of the nanocomposites. An increase in the thermal stability under nitrogen atmosphere was observed as the PTFE amount increases. However under air, no difference is observed in the various systems. These observations suggest that only a physical shield can be exerted by the PTFE cores to the PMMA matrix possibly due to a weak interface between PTFE and the PMMA. This hypothesis is also substantiated by the DMA analysis.     

核壳结构CdS/ZnS纳米微粒的制备与光学特性

CdS and CdS/ZnS core-shell structure nano particles were synthesized in micro emulsion, and characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM), UV absorption spectra and PL. The average diameter of CdS was about 3.3 nm, and CdS/ZnS core-shell structure was confirmed by XRD and UV. Considering the optical properties of CdS/ZnS core-shell structure nanoparticles which have different ZnS shell thickness, the UV absorption edge of CdS/ZnS becomes as lightred-shift with the thickness of ZnS layer increasing, and the absorption of shortwave band is strongly enhanced at the same time. The PL spectra indicate that ZnS shell layer can greatly eliminate surface defects of CdS nanoparticles and make its band-edge directed recombination increased, and the luminous efficiency of CdS is improved greatly when it has appropriate shell thickness.     

含5-氟尿嘧啶的复合结构纳米颗粒的合成及其光谱研究

合成了包覆有5-氟尿嘧啶的银/二氧化硅复合结构纳米颗粒.用透射电子显微镜、红外光谱和拉曼光谱对合成的化合物进行了表征.讨论了药物分子在银表面的拉曼增强效应以及二氧化硅壳层对它的影响.     

Pt@Au/Al2O3核壳纳米粒子的制备和表征及其在催化氧化甲苯中的应用

Customizing core-shell nanostructures is considered to be an efficient approach to improve the catalytic activity of metal nanoparticles. Various physiochemical and green methods have been developed for the synthesis of core-shell structures. In this study, a novel liquid-phase hydrogen reduction method was employed to form core-shell Pt@Au nanoparticles with intimate contact between the Pt and Au particles, without the use of any protective or structure-directing agents. The Pt@Au core-shell nanoparticles were prepared by depositing Au metal onto the Pt core; AuCl⁴⁻ was reduced to Au(0) by H₂ in the presence of Pt nanoparticles. The obtained Pt@Au core-shell structured nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM, fast Fourier transform, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and H₂-temperature programmed reduction (H₂-TPR) analyses. The EDX mapping results for the nanoparticles, as obtained from their scanning transmission electron microscopy images in the high-angle annular dark-field mode, revealed a Pt core with Au particles grown on its surface. Fourier transform measurements were carried out on the high-resolution structure to characterize the Pt@Au nanoparticles. The lattice plane at the center of the nanoparticles corresponded to Pt, while the edge of the particles corresponded to Au. With an increase in the Au content, the intensity of the peak corresponding to Pt in the FTIR spectrum decreased slowly, indicating that the Pt nanoparticles were surrounded by Au nanoparticles, and thus confirming the core-shell structure of the nanoparticles. The XRD results showed that the peak corresponding to Pt shifted gradually toward the Au peak with an increase in the Au content, indicating that the Au particles grew on the Pt seeds; this trend was consistent with the FTIR results. Hence, it can be stated that the Pt@Au core-shell structure was successfully prepared using the liquid-phase hydrogen reduction method. The catalytic activity of the nanoparticles for the oxidation of toluene was evaluated using a fixed-bed reactor under atmospheric pressure. The XPS and H₂-TPR results showed that the Pt₁@Au₁/Al₂O₃ catalyst had the best toluene oxidation activity owing to its lowest reduction temperature, lowest Au 4d & 4f and Pt 4d & 4f binding energies, and highest Au⁰/Au^δ+ and Pt⁰/Pt²⁺ proportions. The Pt₁@Au₂Al₂O₃ catalyst showed high stability under dry and humid conditions. The good catalytic performance and high selectivity of Pt@Au/Al₂O₃ for toluene oxidation could be attributed to the high concentration of adsorbed oxygen species, good low-temperature reducibility, and strong interaction.     

担载型纳米金的制备参数优化及电催化性能探索

纳米尺度的金由于常表现出有趣的尺寸效应和物理化学特性而被大量应用于催化反应中,但是其在电催化反应中的应用却十分有限. 本文以水为溶剂、HAuCl₄为前驱体、十二烷基聚乙二醇醚（Brij 35）等为软模板剂、NaBH₄为还原剂、活性炭或石墨烯为载体,在温和反应条件下获得担载型金纳米电催化剂. 本文考察并优化了关键制备参数和样品纯化方法,最终确定NaBH₄的最佳浓度区间为5 ~ 10mmol•L^-1,Brij 35的最佳浓度约为1 mmol•L^-1,在3 ~ 16 ^oC下金纳米颗粒的尺寸容易控制,石墨烯和活性炭（EC600）是金纳米颗粒的良好载体. 在优化的反应条件下,金纳米颗粒的粒径可以被控制在1 ~ 4 nm. 热处理法可以有效去除表面活性剂,纯化后的担载型纳米金电催化剂在醇类小分子的氧化反应中表现出良好的性能.