SiO_2空心纳米微球的合成

为了改善聚合物粒子与SiO2粒子之间的亲和力及SiO2粒子在聚合物粒子表面的吸附,首先使用共单体4-乙烯基吡啶(4VP)功能化苯乙烯(PS)粒子,合成了聚(苯乙烯-共-4-乙烯基吡啶)(P(St-4VP))粒子。然后在NH4OH/乙醇介质中,将溶胶-凝胶法生成的SiO2粒子包覆在P(St-4VP)粒子表面,聚合物核被溶解得到SiO2空心纳米微球。随着P(St-4VP)粒子中共单体4VP含量以及正硅酸乙酯(TEOS)用量增加,SiO2空心纳米微球的壳层厚度增加,且壳层表面变得粗糙。随着PVP用量增加,SiO2空心纳米微球的平均尺寸下降,其壳层从松散粗糙变得致密光滑。NH4OH用量增加对SiO2空心纳米微球尺寸和形态的影响不大。     

溶胶-凝胶法制备核壳SiO2/Fe3O4复合纳米粒子的研究

采用溶胶-凝胶法,以尺寸约10nm的Fe3O4纳米粒子为种子,碱催化正硅酸已酯(TEOS)水解、缩合,制备了磁性可控的核壳结构SiO2/Fe3O4复合纳米粒子.系统研究了醇水比、NH4OH及TEOS的浓度对复合纳米粒子形貌和性能的影响,并分析了SiO2/Fe3O4复合纳米粒子的生成机理.结果表明,SiO2的生长主要是SiO2初级粒子在Fe3O4表面的聚集生长,醇水比为4∶1、NH4OH浓度为0.3mol/L和TEOS浓度低于0.02mol/L时,随TEOS浓度的增大,SiO2壳层增厚,复合粒子饱和磁化强度下降,矫顽力基本不变,仍具有良好的超顺磁性.     

钯纳米粒子/嵌段共聚物复合胶束的制备及催化性能

嵌段共聚物聚苯乙烯-b-聚4-乙烯吡啶(PS-b-P4VP)在酸水(pH=2)中自组装形成PS为核,P4VP为壳的核-壳胶束(约为30 nm)。在核-壳胶束酸水溶液(pH=2)中加入氯化钯,钯离子与P4VP络合形成聚苯乙烯为核、聚4-乙烯吡啶/钯离子为壳的胶束。进一步加入硼氢化钠(NaBH4)原位还原钯离子,得到钯纳米粒子(粒径约为3 nm)位于P4VP壳层的复合胶束。复合胶束对4-硝基苯酚还原为4-氨基苯酚的反应中表现出催化活性,动力学研究结果表明,反应为一级反应,反应速率随复合胶束浓度的增加及反应温度的升高而加快。     

通过嵌段共聚物自组装制备哑铃状Au-Fe304纳米粒子排列

通过嵌段共聚物自组装制备哑铃型Au-Fe3O4纳米粒子排列,先通过旋涂含有哑铃型纳米粒子（DBNPs）的聚苯乙烯-b-聚（2-乙烯基吡啶）（PS—b—P2VP）混合溶液得到复合薄膜,再将复合薄膜在高温下退火,实验发现,无论是预先合成的表面带有油酸基团,还是11-巯基十-烷酸修饰的哑铃型纳米粒子,都可以选择性的进入到PS—b—P2VP嵌段共聚物中的P2VP柱状微区中。实验结果表明,在退火过程中,哑铃型纳米粒子可以进入到嵌段共聚物中的一个微区中,并不取决于其表面的化学性质。     

纳米CaCO3/TiO2复合粒子的制备

首先制备出分散性能良好的Ti(OH)4胶体溶液,然后将胶体溶液加入到以十二烷基苯磺酸钠为分散剂的纳米CaCO3水性悬浮液中;通过改变体系的温度、pH值等参数破坏Ti(OH)4胶体粒子的稳定性,导致Ti(OH)4胶体粒子沉积在纳米CaCO3表面从而形成具有核-壳结构的纳米CaCO3/TiO2复合粒子,沉积过程中纳米CaCO3可起成核剂作用.所制备的纳米CaCO3/TiO2复合粒子以球形或近球形为主,粒度均一,且壳层TiO2粒子的尺寸为5～8nm.     

SiO_2金纳米棒复合粒子的制备及其光学性质的研究

采用银离子介导的晶种生长法,制备出具有理想局域表面等离子共振(LSPR)吸收峰的金纳米棒(GNR)。通过碱催化正硅酸四乙酯(TEOS)的水解缩合,在GNR表面形成SiO_2壳层。利用透射电镜对其进行形貌表征,成功制备出壳层为15nm和30nm的SiO_2金纳米棒复合粒子(GNR-SiO_2),其中壳层为30nm的GNR-SiO_2呈规则的椭球形,具有明显的介孔特征。Zeta(电位)结果表明,SiO_2包埋使GNR的表面电位发生了剧烈反转,由35.6mV变为-14.5mV。其光学性质研究表面调节硝酸银的用量以及环境pH可以实现GNR局域表面等离子体共振吸收峰(LSPR)吸收峰在700~950nm内的调控,而且SiO_2包埋对复合粒子的LSPR吸收峰及光热转化效应没有明显影响。SiO_2包埋能够在改善GNR在生物毒性、稳定性及载药率等方面的不足的同时不影响其光学特性,极大的增加了GNR在生物检测和纳米药物领域的应用潜力。     

巯基表面修饰磁性复合纳米粒子用于重金属离子去除的研究

采用化学共沉淀法合成磁性Fe3O4纳米粒子,并且利用正硅酸乙酯（TEOS）的水解和凝聚作用在Fe3O4纳米粒子表面沉积包覆一层SiO2,合成核壳式的Fe3O4@SiO2复合纳米粒子。以Fe3O4@SiO2纳米粒子为基体,将（3-巯基丙基）三乙氧基硅烷嫁接到纳米粒子表面,制备出巯基功能化的纳米材料,将其应用于对重金属离子...     

聚苯乙烯/纳米SiO2复合颗粒制备与表征

为改善二氧化硅(SiO2)纳米粒子与聚合物基体间的亲和性,使SiO2表面功能化,将硅烷偶联剂KH-570引入C=C基团,采用乳液聚合方法在纳米SiO2粒子表面接枝苯乙烯(St)单体,实现了纳米二氧化硅表面的聚苯乙烯(PS)高分子包覆改性,制备了具有核/壳结构的SiO2-PS复合纳米粒子,产物的单体转化率和接枝效率在80%以上.研究了二氧化硅含量和偶联剂用量对聚合反应的单体转化率和接枝效率的影响,探讨了偶联剂的作用机理,利用FT-IR、TEM、TG对SiO2-PS复合粒子的表面结构进行了表征.结果表明,复合粒子具有明显的核壳结构,壳层厚度在20nm左右,乳液聚合过程可有效使二氧化硅的团聚体剥离呈纳米级颗粒.     

SiO2包覆Fe2O3纳米粒子的制备和性能

在近球形α-Fe2O3颗粒的悬浮液中,以正硅酸乙酯(TEOS)为硅源,氨水和尿素为催化剂,合成了Fe2O3-SiO2核-壳粒子.应用TEM.XRD对Fe2O3-SiO2核-壳粒子结构进行了测定.研究了TEOS.氨水的浓度对核-壳粒子结构的影响.UV-Vis吸收光谱表明,SiO2壳层消除了Fe2O3纳米粒子的表面悬挂键,产生增强的激子发射,使得核-壳粒子的吸收峰发生蓝移.根据带边吸收峰的波长计算出核-壳粒子中Fe2O3的禁带宽度为2.25 eV.     

氮掺杂空心TiO2纳米粒子的制备与研究

采用一种简便的方法合成了氮掺杂空心TiO:纳米粒子.以聚苯乙烯(PS)纳米粒子为模板、氨水为催化剂、三乙醉胺为抑制剂,采用溶胶-凝胶方法合成了PS/TiOZ(核/壳)纳米复合粒子.考察了氨水、三乙醉胺和钛酸正丁酯用量对TiO:壳层表面形态和厚度的影响.氨水用量3.OOg时TiO2壳层表面较光滑,氨水用量6.OOg时其表...     

Stimuli‐Responsive,Shape‐Transforming Nanostructured Particles

Development of particles that change shape in response to external stimuli has been a long‐thought goal for producing bioinspired, smart materials. Herein, the temperature‐driven transformation of the shape and morphology of polymer particles composed of polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) block copolymers (BCPs) and temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAM) surfactants is reported. PNIPAM acts as a temperature‐responsive surfactant with two important roles. First, PNIPAM stabilizes oil‐in‐water droplets as a P4VP‐selective surfactant, creating a nearly neutral interface between the PS and P4VP domains together with cetyltrimethylammonium bromide, a PS‐selective surfactant, to form anisotropic PS‐b‐P4VP particles (i.e., convex lenses and ellipsoids). More importantly, the temperature‐directed positioning of PNIPAM depending on its solubility determines the overall particle shape. Ellipsoidal particles are produced above the critical temperature, whereas convex lens‐shaped particles are obtained below the critical temperature. Interestingly, given that the temperature at which particle shape change occurs depends solely on the lower critical solution temperature (LCST) of the polymer surfactants, facile tuning of the transition temperature is realized by employing other PNIPAM derivatives with different LCSTs. Furthermore, reversible transformations between different shapes of PS‐b‐P4VP particles are successfully demonstrated using a solvent‐adsorption annealing with chloroform, suggesting great promise of these particles for sensing, smart coating, and drug delivery applications.     

SiO2纳米壳的厚度对羰基铁/SiO2核壳复合粒子的性能影响

以聚乙烯毗咯烷酮作表面改性剂，用溶胶-凝胶法，通过控制反应时间，在羰基铁粒子表面均匀快速地包覆不同厚度的SiO2纳米壳层，并研究了SiO2纳米壳层厚度对羰基铁／SiO2核壳复合粒子的抗热氧化性能、静磁性能、微波介电常数和吸波性能的影响．结果表明：增加SiO2纳米壳层的厚度，羰基铁／SiO2核壳复合粒子的抗热氧化能力提高，比饱和磁化强度出现最大值，矫顽力和剩余磁化强度出现最小值，微波介电常数单调降低；用其制备的吸波涂层材料在壳层厚度为15nm时，反射损耗≤-8dB的带宽达到最大值，超过10GHz，     

SiO_2包覆羰基铁的微波吸收性能研究

以硅溶胶为前驱体,快速制备出SiO2包覆羰基铁吸收剂,研究了SiO2包覆对其热性能、电磁和吸波性能的影响。热分析结果表明,SiO2包覆羰基铁的抗氧化性能显著提高。与未包覆羰基铁相比,SiO2包覆羰基铁的介电常数和磁导率都有所下降。反射率结果表明,包覆后羰基铁在X波段内具有较好的吸波效果,当包覆后羰基铁质量分数为70%、涂层厚度为1.8mm时,涂层在8.2～12.4GHz频率范围内的反射率均小于-10dB。     

Synthesis and characterization of novel Ag-polypyrrole@poly(styrene-co-methacrylic acid) nanocomposite particles

Novel raspberry-like Ag-polypyrrole/poly(styrene-co-methacrylic acid) (Ag-PPy/P(St-co-MAA)) colloidal nanocomposite particles were prepared by aqueous oxidative polymerization of pyrrole using AgNO₃ as the oxidant. The polymerization was carried out in the pre-synthesized polymer-emulsion of P(St-co-MAA) with emulsifier-free P(St-co-MAA) latex particles serving as both the templates and the stabilizers. Without any extra surfactants or polymer stabilizers, the polymerization proceeded steadily with the in-situ produced Ag-PPy nanocomposites depositing on the surface of the template particles. The obtained product is typical of raspberry-like morphology, whose nanostructures and compositions were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and electron dispersive X-ray spectrometer (EDS), respectively. The results confirmed that the surface of the P(St-co-MAA) latex was coated by Ag-PPy nanocomposite particles with a size range from 2 nm to 50 nm. Most of Ag nanoparticles are encapsulated by the PPy sheath or dispersed in the PPy layer.     

细乳液法合成单核核壳结构氧化硅/聚苯乙烯复合微球

采用细乳液聚合法,以3-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)表面改性的直径50nm的氧化硅粒子为核,在乳化剂、助乳化剂、引发剂存在的情况下制备了小粒径、单核核壳结构氧化硅/聚苯乙烯纳米复合微球.研究表明,苯乙烯的浓度、超声细乳化时间,是制备这种小粒径、单分散、单核核壳结构的氧化硅/聚苯乙烯纳米复合微球的关键因素.透射电镜(TEM)的观察显示,在优化的实验条件下,可以制得平均粒径95nm,壳厚20nm,粒径均一、球形规整度较好、单核核壳结构的氧化硅/聚苯乙烯纳米复合微球.其平均粒径远低于用其它聚合方法制备的复合微球.     

SiO2-Ag纳米复合颗粒自组装的制备与表征

利用自组装法在空气-水界面制备了SiO2薄膜粒子,将所制薄膜粒子先后用AgNO3溶液与Na2S2O3溶液浸泡,并充分曝光,形成了一种形状如"西瓜"的SiO2-Ag纳米复合颗粒.采用X射线衍射(XRD)、透射电子显微镜(TEM)、紫外可见吸收光谱(UV-Vis)对其结构进行了表征和分析,并初步探讨了其结构的形成机理.结果表明,纳米Ag"瓜子"均匀地分散于SiO2"瓜瓤"颗粒中,形成的复合颗粒呈球形,粒径均匀.     

Spark plasma sintering of silicon nitride using nanocomposite particles

The spark plasma sintering (SPS) of silicon nitride (Si₃N₄) was investigated using nanocomposite particles composed of submicron-size α-Si₃N₄ and nano-size sintering aids of 5 wt% Y₂O₃ and 2 wt% MgO prepared through a mechanical treatment. As a result of the SPS, Si₃N₄ ceramics with a higher density were obtained using the nanocomposite particles compared with a powder mixture prepared using conventional wet ball-milling. The shrinkage curve of the powder compact prepared using the mechanical treatment was also different from that prepared using the ball-milling, because the formation of the secondary phase identified by the X-ray diffraction (XRD) method and liquid phase was influenced by the presence of the sintering aids in the powder compact. Scanning electron microscopy (SEM) observations showed that elongated grain structure in the Si₃N₄ ceramics with the nanocomposite particles was more developed than that using the powder mixture and ball-milling because of the enhancement of the densification and α-β phase transformation. The fracture toughness was improved by the development of the microstructure using the nanocomposite particles as the raw material. Consequently, it was shown that the powder design of the Si₃N₄ and sintering aids is important to fabricate denser Si₃N₄ ceramics with better mechanical properties using SPS.     

Nanoscale graft copolymer templates decorated by silver bromide nanoparticles arrays

A novel amphiphilic poly(4-vinyl pyridine)-graft-poly(lauryl methacrylate) (P4VP-g-PLMA) graft copolymer at 29:71 wt% was synthesized via free radical polymerization, as confirmed by nuclear magnetic resonance (1H NMR). This self-assembled copolymer was used to template the in-situ growth of silver bromide (AgBr) nanoparticles, producing a solid-state nanocomposite film. Interestingly enough, AgBr nanoparticles with a bimodal size distribution were selectively grown within the copolymer matrix. Large nanoparticles with diameters of 30-40 nm were formed in the center of the hydrophilic P4VP spherical domains whereas smaller particles with diameters of 8-10 nm were decorated in hydrophobic PLMA domains. To the best of our knowledge, this is the first report on the nanoscale decoration of amphiphilic copolymer by AgBr nanoparticles with a size-selective, bimodal size distribution.