微粒团聚的尺度效应及其分形表征

利用全自动激光粒度分析仪,研究了乙醇分散液中羟基磷灰石微粒团聚过程中粒径分布、微粒的平均团聚粒径和比表面积随微粒团聚时间的变化关系,以及微粒质量分数对平均团聚粒径和比表面积的影响,对微粒团聚平均粒径、比表面积及团聚速率与微粒质量分数及微粒团聚时间的关联性进行了分形表征。结果表明：随微粒团聚时间的延长,所测微纳米微粒的最大分布粒径值、最小分布粒径值逐渐增大,分布曲线有逐渐向正态分布发展的趋势;随团聚时间增加,或微粒质量分数的增大,微粒团聚平均粒径逐渐增大,而比表面积逐渐减小,并都在一定的时间内达到动态平衡;微粒团聚速率分形维数可以客观地描述微粒团聚基本规律,当微粒质量分数一定时,微粒团聚分形维数越大,其团聚速度越大,当微粒团聚分形维数一定时,微粒质量分数越大,团聚速率越大。     

纳米粒子的分散机理、方法及应用进展

分析了纳米粒子团聚机理,并介绍了纳米粒子分散理论、方法,包括机械法和表面改性法,尤其详细地介绍了表面改性的方法,如：无机物改性纳米粒子表面、有机物改性纳米粒子表面、有机．无机复合改性纳米粒子表面,并介绍了相应的应用成果。     

Nano-Particles Carried by Multiple Dynein Motors Self-Regulate Their Number of Actively Participating Motors

Intra-cellular active transport by native cargos is ubiquitous. We investigate the motion of spherical nano-particles (NPs) grafted with flexible polymers that end with a nuclear localization signal peptide. This peptide allows the recruitment of several mammalian dynein motors from cytoplasmic extracts. To determine how motor–motor interactions influenced motility on the single microtubule level, we conducted bead-motility assays incorporating surface adsorbed microtubules and combined them with model simulations that were based on the properties of a single dynein. The experimental and simulation results revealed long time trajectories: when the number of NP-ligated motors N_m increased, run-times and run-lengths were enhanced and mean velocities were somewhat decreased. Moreover, the dependence of the velocity on run-time followed a universal curve, regardless of the system composition. Model simulations also demonstrated left- and right-handed helical motion and revealed self-regulation of the number of microtubule-bound, actively transporting dynein motors. This number was stochastic along trajectories and was distributed mainly between one, two, and three motors, regardless of N_m. We propose that this self-regulation allows our synthetic NPs to achieve persistent motion that is associated with major helicity. Such a helical motion might affect obstacle bypassing, which can influence active transport efficiency when facing the crowded environment of the cell.     

丙烯酸酯核壳纳米粒子的合成及其改性环氧树脂

以丙烯酸丁酯(BA)为软单体、甲基丙烯酸甲酯(MMA)为硬单体和甲基丙烯酸缩水甘油脂(GMA)为官能单体,采用乳液聚合法合成出具有活性结构的BA/MMA/GMA核壳纳米粒子,并以此作为环氧树脂(EP)的增韧改性剂。研究结果表明:当w(核壳粒子)=10%、m(BA):m(MMA):m(GMA)=80:20:10时,与纯EP体系相比,改性EP体系的断裂伸长率提高了42.5%,剥高强度提高了近3倍,25℃和150℃时的剪切强度分别提高了48.6%和31.2%,坡璃化转变温度变化不大;红外光谱(FT-IR)证实,该核壳纳米粒子具有典型的特征吸收峰;透射电镜(TEM)观察结果表明,合成粒子具有纳米级核壳结构。     

Surface modification of TiO2 nano-particles with silane coupling agent and investigation of its effect on the properties of polyurethane composite coating

Surface modification and characterization of TiO₂ nano-particles as an additive in a polyurethane clear coat were investigated. For the improvement of nano-particles dispersion and increasing possible interactions between nano-particles and polymeric matrix, the surface of the nano-particles was modified with amino propyl trimethoxy silane (APS). Equivalent amount of APS for monolayer formation on the nano-particles surface was determined by means of elemental analysis (CHN). The grafting of APS on the TiO₂ nano-particles surface was characterized with TGA and FTIR techniques. Mechanical properties of coatings containing various amount of TiO₂ nano-particles were evaluated with DMA technique and tensile strength measurement. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance of the nano-TiO₂ composite coatings in the wavelength range of 230–700 nm.     

几种纳米固体润滑添加剂热稳定性及其对基础油黏度的影响

采用综合热分析仪测试纳米铜、镍、锡和SiO2粉以及超细蛇纹石粉的差热分析曲线,研究了常用固体润滑添加剂的热稳定性,并用平氏毛细管黏度法研究了含不同质量分数纳米金属Cu-Ni-Sn粉、纳米SiO2粉和超细蛇纹石粉对基础油黏度及黏度指数的影响.结果表明:纳米铜、镍、锡和SiO2粉以及超细蛇纹石粉等几种固体润滑添加剂的热学性质比较稳定,在200 ℃以前不发生氧化现象,其对基础油的黏度和黏度指数没有影响,具备作为润滑油添加剂的条件.     

脲酶诱发均匀沉淀法室温制备纳米CdS

采用脲酶诱发均匀沉淀法制备CdS纳米微粒。向反应体系中同时加入EDTA和甘氨酸,成功消除了Cd^2＋离子对脲酶的抑制作用,使产生沉淀的化学环境更均匀。XRD显示得到的样品为闪锌矿结构的CdS,平均粒径为9nm;TEM表明CdS样品的晶粒呈单一的球形,大小较均匀,有团聚现象;选区电子衍射照片显示,纳米CdS的结晶程度良好。     

多元醇还原制备纳米Co粉及其磁性的研究

采用二价钴盐为前驱物,1,2-丙二醇为还原剂,用液相还原法制备了晶粒尺寸约为10～13nm、具有面心立方(β相)结构的纯度高、粒度均匀的纳米钴粉,运用XRD、TEM等分析方法对制备的纳米钴粉进行物相和结构形貌的表征,初步研究了多元醇法还原Co纳米粉的反应机理.采用VSM对纳米钴粉进行磁学性能的表征.结果表明,所制备的纳米Co粉在室温下具有铁磁性,并且矫顽力不高(6.282×103A/m).     

燃烧法快速合成轻质纳米氧化铈及其脱色性能

以硝酸铈为氧化剂,抗坏血酸为燃烧剂,采用燃烧法快速合成纳米氧化铈,并用X射线衍射、傅立叶变换红外光谱、紫外-可见光谱、扫描电子显微镜等技术进行表征;利用所制备的纳米氧化铈对酸性品红进行脱色实验,考察不同样品、氧化铈的用量、双氧水用量、离心机转数、脱色温度、脱色时间对酸性品红脱色效果的影响。结果表明,脱色剂选用氧化剂与燃烧剂的物质的量比为1∶2时制备的氧化铈,脱色剂用量为0.6 g/L,双氧水用量为20 mL/L,转速为3 000 r/min,脱色温度为70℃,在最佳实验条件下,90 min酸性品红脱为无色。     

硬脂酸改性纳米ZnO的研究

采用酯化反应法,以水为溶剂,采用硬脂酸对纳米ZnO的表面进行改性,对改性效果进行测试表征。其最佳工艺条件为:硬脂酸质量分数为6%,反应温度为90℃,反应时间为90 min。结果表明,改性后的ZnO粒子呈纳米级的分散,亲油化度值达到72.31%,吸水率达到3.04%;经表面改性的纳米ZnO表现了很好的亲油疏水性;改性后的纳米ZnO表面引入了硬脂酸的官能团,使其表面羟基的数目明显减少,其改性机理为纳米ZnO表面羟基与硬脂酸分子中的羧基发生了类似醇和酸的酯化反应。