利用Cd(OH)_2选择性包覆与光分解腐蚀缩小CdS纳米微粒的尺寸分布的研究

提出结合Ｃｄ（ＯＨ）２ 选择性包覆与光分解腐蚀法缩小ＣｄＳ纳米微粒的尺寸分布, 并通过对ＣｄＳ纳米微粒发射光谱的研究证实了这一设计思想． 以多聚磷酸钠（ＨＭＰ）为稳定剂合成ＣｄＳ纳米微粒, 再通过Ｃｄ２＋ 与ＯＨ－ 的选择性包覆在大粒径的ＣｄＳ纳米微粒表面形成一层Ｃｄ（ＯＨ）２, 然后溶液置于日光下辐照处理, 数天后, 未经包覆的小粒径ＣｄＳ纳米微粒被日光腐蚀分解, 溶液中只剩下被Ｃｄ（ＯＨ）２ 包覆的大粒径ＣｄＳ纳米微粒, 这样即可达到缩小ＣｄＳ纳米微粒尺寸分布的目的．     

不同粒径金纳米微粒对荧光素钠的猝灭效应研究

采用柠檬酸盐合成法制备了不同粒径的金纳米微粒,用吸收光谱和透射电镜对金纳米微粒进行了表征。研究了不同粒径金纳米微粒与荧光素钠分子的相互作用。发现金纳米微粒对荧光素钠具有荧光猝灭效应, 并且其荧光猝灭程度与金纳米微粒的粒径大小有关。随着金纳米微粒粒径的减小,荧光猝灭程度增大。探讨了金纳米微粒对荧光素钠荧光猝灭的机理,表明该荧光猝灭为动态猝灭。     

自悬浮定向流技术中铜纳米微粒的粒度控制研究

 采用自悬浮定向流技术制备了金属铜纳米微粒，根据TEM的行貌像对样品平均粒度进行标定，并结合样品制备的条件对制备工艺进行了研究。结果表明，自悬浮定向流技术可以方便地制备出不同粒度的金属铜纳米微粒，微粒平均粒径随熔球温度的降低而减小，随冷却气体流速的增大而减小；在1 200℃下微粒平均粒径随惰性气体压强的增大而减小，而在1 300℃时惰性气体压强对微粒平均粒径的影响不再具有规律性。     

稀土纳米发光材料的燃烧法制备及光谱性质

用燃烧法制备了不同粒径的La2O3:Eu3 纳米微粒,研究了影响La2O3:Eu3 纳米微粒大小的实验条件,发现粒径大小随甘氨酸(Gly)与稀土离子比例的增大而减小.制备的纳米微粒由谢乐公式计算的粒径尺寸为12～28 nm.测量了样品的高分辨光谱.运用激光选择激发,研究了光谱在不同发光中心上的变化,表面态对于这些变化起着主要作用.     

用络合转化法在甲壳胺膜上制备CdS、ZnS纳米微粒

结构单元上带有配位基团的天然高分子甲壳胺与Cd2+和Zn2+络合后,通过络合转化方法可以在高分子膜上制备CdS、ZnS等纳米微粒。用这种方法所得微粒尺寸可控、粒径均一、表面缺陷少。     

Ag-Au二元纳米微粒吸收谱的计算

纳米微粒的光学性能与其表面等离子体共振关系密切.本文利用推广的Mie理论计算研究了Au-Ag体系单质、合金以及核壳结构纳米颗粒的消光、吸收和散射的性能(包括壳核结构Ag-Au微粒在紫外-可见光的吸收性能),计算结果与实验值相符合得很好.研究表明,随着粒径的增加,微粒表面等离子体共振偶极吸收峰出现红移,波峰位置与纳米微粒的尺寸具有线性关系.壳核结构中,粒径与核壳比决定了整个微粒的吸收性能.进一步研究表明,当Au壳层较薄时,可以获得具有可调光学性能的壳核纳米结构;而当Au壳层较厚时,其光学性能与同尺寸单质Au微粒一致.通过计算分析,本文还将Mie理论推广到具有空腔结构并且壳层厚度达到一定值的纳米微粒.另外,研究发现合金结构纳米微粒的吸收峰位置与合金成分有着线性关系.本研究表明,人们可以通过控制纳米微粒的尺寸、形貌和结构,调节其表面等离子体共振峰位,这大大拓展了纳米微粒的应用范围.     

ZnS纳米微粒的形貌结构对其光学特性的影响

报道在聚乙烯醇（PVA）膜上采用离子络合法镶嵌的ZnS纳米微粒的形貌结构与光学特性。透射电子显微镜结果表明，在聚乙烯醇膜中的ZnS纳米微粒分布比较均匀，粒径可控制在2－7nm的范围内；电子衍射分析表明，ZnS纳米微粒具有类似于β－ZnS体材料的晶体结构。室温下的光发射峰的位置在414～440nm范围内。着重分析了ZnS纳米形貌结构与其发射波长和强度之间的关系，并探讨了其不同的发射机理。     

自悬浮定向流技术中铜纳米微粒的粒度控制研究

采用自悬浮定向流技术制备了金属铜纳米微粒,根据TEM的行貌像对样品平均粒度进行标定,并结合样品制备的条件对制备工艺进行了研究。结果表明,自悬浮定向流技术可以方便地制备出不同粒度的金属铜纳米微粒,微粒平均粒径随熔球温度的降低而减小,随冷却气体流速的增大而减小;在1 200℃下微粒平均粒径随惰性气体压强的增大而减小,而在1 300℃时惰性气体压强对微粒平均粒径的影响不再具有规律性。     

自悬浮定向流法制备纳米铜微粒及其结构表征

 采用自悬浮定向流法制备金属铜纳米微粒，并用TEM，XRD和AES等分析手段研究了铜纳米微粒的形貌、粒度、结构及其表面氧化层特性。结果表明，在一定的参数条件下采用自悬浮定向流法可制备出单晶纳米铜微粒，并且通过工艺参数的调控可达到对微粒粒度的控制。     

铅纳米微粒用作油性润滑的摩擦学性能研究

在石蜡油 聚乙二醇的混合溶剂中 ,通过液相分散法成功地制备出了铅纳米微粒 .其中 ,石蜡油是反应介质 ,聚乙二醇是抗氧化剂 .同时 ,对铅纳米微粒的形貌和结构进行了透射电镜 (TEM)和X光衍射 (XRD)表征 .结果表明 ,铅纳米微粒呈球形 ,平均粒径为 70nm ,具有与本体铅相同的晶体结构 .另外 ,在四球试验机上表征了铅纳米微粒作为润滑油添加剂的摩擦学性能 .摩擦试验表明 ,铅纳米微粒具有良好的减摩抗磨性能 ,并能够显著改善基础油的承载能力 .磨斑表面分析表明 ,铅纳米微粒的抗磨减摩机制不是形成金属沉积膜 ,可能是在摩擦接触面形成滑动 轴承系     

Size measurement of nanoparticles using the emission intensity distribution of laser-induced plasma

A two-dimensional optical imaging method is presented for monitoring the laser-induced breakdown events of aqueous nanoparticles. The method is based on measuring the light intensity distribution of plasma from spatially resolved breakdown events. The number of laser breakdown events as a function of the emission intensity follows the Gaussian distribution and its full-width at a half-maximum appears in direct correlation with the particle size. Hence the particle size can be determined by measuring the plasma emission intensity distribution. Calibration of the method is carried out with reference polystyrene particles dispersed in water. Application is demonstrated for measuring bentonite colloidal particles of different sizes in groundwater. PACS 42.62.Eh; 52.25.Rv; 52.70.Nc     

Taylor dispersion of nanoparticles

The ability to detect and accurately characterize particles is required by many fields of nanotechnology, including materials science, nanotoxicology, and nanomedicine. Among the most relevant physicochemical properties of nanoparticles, size and the related surface-to-volume ratio are fundamental ones. Taylor dispersion combines three independent phenomena to determine particle size: optical extinction, translational diffusion, and sheer-enhanced dispersion of nanoparticles subjected to a steady laminar flow. The interplay of these defines the apparent size. Considering that particles in fact are never truly uniform nor monodisperse, we rigorously address particle polydispersity and calculate the apparent particle size measured by Taylor dispersion analysis. We conducted case studies addressing aqueous suspensions of model particles and large-scale-produced “industrial” particles of both academic and commercial interest of various core materials and sizes, ranging from 15 to 100 nm. A comparison with particle sizes determined by transmission electron microscopy confirms that our approach is model-independent, non-parametric, and of general validity that provides an accurate account of size polydispersity—independently on the shape of the size distribution and without any assumption required a priori.     

Characterization of energy barrier and particle size distribution of lyophilized ferrofluids by magnetic relaxation measurements

The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Néel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy.     

Size Determination of Au Aerosol Nanoparticles by Off-Line TEM/STEM Observations

Determination of particle size distributions of Au aerosol nanoparticles has been performed by a TEM/STEM investigation. The particles are generated by an evaporation/condensation method and are size-selected by differential mobility analyzers (DMA) based on their electrical mobility. Off-line TEM measurements resulted in equivalent projected area diameters assuming that the particles are spherical in shape. In this paper critical factors such as magnification calibration, sampling, image analysis, beam exposure and, particle shape are treated. The study shows that the measures of central tendency; mean, median and mode, are equal as expected from a narrow size distribution. Moreover, the correlation between TEM/STEM and DMA are good, in practice 1:1. Also, STEM has the advantage over TEM due to enhanced contrast and is proposed as an alternative route for determination of particle size distributions of nanoparticles with lower contrast.     

Thermomagnetic determination of Fe3O4 magnetic nanoparticle diameters for biomedical applications

The utility and promise of magnetic nanoparticles (MagNPs) for biomedicine rely heavily on accurate determination of the particle diameter attributes. While the average functional size and size distribution of the magnetic nanoparticles directly impact the implementation and optimization of nanobiotechnology applications in which they are employed, the determination of these attributes using electron microscopy techniques can be time-consuming and misrepresentative of the full nanoparticle population. In this work the average particle diameter and distribution of an ensemble of Fe₃O₄ ferrimagnetic nanoparticles are determined solely from temperature-dependent magnetization measurements; the results compare favorably to those obtained from extensive electron microscopy observations. The attributes of a population of biocompatible Fe₃O₄ nanoparticles synthesized by a thermal decomposition method are obtained from quantitative evaluation of a model that incorporates the distribution of superparamagnetic blocking temperatures represented through thermomagnetization data. The average size and size distributions are determined from magnetization data via temperature-dependent zero-field-cooled magnetization. The current work is unique from existing approaches based on magnetic measurement for the characterization of a nanoparticle ensemble as it provides both the average particle size as well as the particle size distribution.     

多分散Au-Ag合金纳米球的光谱消光法反演

贵金属纳米颗粒具有局域表面等离子体共振特性而引起了广泛的关注,其中Au-Ag合金纳米颗粒具有良好的结构稳定性、光热性能以及潜在的抗癌功效而得到普遍研究。在众多应用中的特性与其粒径和浓度密切相关,然而目前常用的电子显微镜观察法和动态光散射法不能同时获得粒径和浓度信息,因此采取有效手段测量颗粒粒径和浓度信息至关重要。基于光谱消光法,利用非负的Tikhonov正则化方法解决反演问题,并根据Mie理论计算消光矩阵。针对噪声问题,采取两种情况研究多分散Au-Ag合金纳米球粒径分布与浓度的反演问题。未添加噪声情况下,颗粒系Ⅰ的反演相对误差小于颗粒系Ⅱ,在波长范围300～500 nm之间的反演相对误差最小,对应平均粒径、粒径标准差和颗粒数浓度的反演相对误差分别为0%,-0.03%和0%。添加随机噪声情况下,将0.5%和1.0%的随机噪声添加进颗粒系Ⅰ中的消光谱,经过数据比较发现在波长范围200～600 nm之间的反演相对误差最小。当添加0.5%的随机噪声时,粒径分布、粒径标准差和颗粒数浓度的变化范围分别为79.76～80.15 nm, 5.60～6.61 nm和0.995 8×1010～1.005 9×1010个·cm-3;当添加1.0%的随机噪声时,粒径分布、粒径标准差和颗粒数浓度的变化范围分别为78.87～80.27 nm, 5.36～9.00 nm和0.992 4×1010～1.027 7×1010个·cm-3。反演结果随着随机噪声的增大,变化范围也明显增大即反演相对误差增大,并且每次添加相同随机噪声后的反演结果不同。为了减少随机噪声导致的不稳定性,对100次反演结果进行平均得到平均粒径、粒径标准差和颗粒数浓度。当随机噪声从0.5%增大至1.0%时,其反演结果的相对误差均增大,但是反演得到的粒径分布、粒径标准差和颗粒数浓度相对误差均小于6%,这说明通过反演算法得到的反演结果具有较好的稳定性。研究表明,光谱消光法为反演多分散Au-Ag合金纳米球粒径分布与浓度提供了一种简单、快速的表征手段,也对研究非球形纳米颗粒有启示作用。     

Workplace air measurements and likelihood of exposure to manufactured nano-objects,agglomerates, and aggregates

Workplace exposure to nanoparticles from gas metal arc welding (GMAW) process in an automobile manufacturing factory was investigated using a combination of multiple metrics and a comparison with background particles. The number concentration (NC), lung-deposited surface area concentration (SAC), estimated SAC and mass concentration (MC) of nanoparticles produced from the GMAW process were significantly higher than those of background particles before welding (P < 0.01). A bimodal size distribution by mass for welding particles with two peak values (i.e., 10,000–18,000 and 560–320 nm) and a unimodal size distribution by number with 190.7-nm mode size or 154.9-nm geometric size were observed. Nanoparticles by number comprised 60.7 % of particles, whereas nanoparticles by mass only accounted for 18.2 % of the total particles. The morphology of welding particles was dominated by the formation of chain-like agglomerates of primary particles. The metal composition of these welding particles consisted primarily of Fe, Mn, and Zn. The size distribution, morphology, and elemental compositions of welding particles were significantly different from background particles. Working activities, sampling distances from the source, air velocity, engineering control measures, and background particles in working places had significant influences on concentrations of airborne nanoparticle. In addition, SAC showed a high correlation with NC and a relatively low correlation with MC. These findings indicate that the GMAW process is able to generate significant levels of nanoparticles. It is recommended that a combination of multiple metrics is measured as part of a well-designed sampling strategy for airborne nanoparticles. Key exposure factors, such as particle agglomeration/aggregation, background particles, working activities, temporal and spatial distributions of the particles, air velocity, engineering control measures, should be investigated when measuring workplace exposure to nanoparticles.     

Estimation of the upper limit of aerosol nanoparticles penetration through inhomogeneous fibrous filters

The fully segregated flow model (FSFM) was formulated to describe filtration of aerosol nanoparticles in polydisperse fibrous filters made of fibers with different diameters. The model is capable of predicting significantly higher penetration of nanoparticles through polydisperse filters than it may be expected from the classical theory applied to a mean fiber diameter. The model was solved numerically in the case of the log-normal fiber size distribution, and a simple correlation between the actual penetration through a polydisperse filter and the one calculated for the geometric mean fiber diameter was proposed. Equivalent fiber diameter for deposition due to Brownian diffusion was determined and it was found to be dependent on particle size and filter’s polydispersity degree, being significantly greater than any mean fiber diameter. It was noted that it is impossible to select any one universal mean fiber diameter to describe penetration of nanoparticles with different sizes. It was also shown that in the case of a polydisperse fibrous filter the apparent exponent of the Peclet number based on the mean fiber diameter is greater than the expected value of −2/3 for diffusional deposition in a monodisperse filter. This prediction is in agreement with the available experimental data. The FSFM is expected to give the estimation of the upper limit of nanoparticles penetration in polydisperse fibrous filters.     

Microencapsulation of TiO2 Nanoparticles with Polymer by Rapid Expansion of Supercritical Solution

A novel preparation method is reported for the microencapsulation of TiO₂ nanoparticles by rapid expansion of supercritical solution with a nonsolvent. A suspension of TiO₂ nanoparticles in carbon dioxide containing a cosolvent and dissolved polymer is sprayed through a nozzle to atmospheric pressure. After rapid expansion, polymer microspheres were obtained. The microspheres do not tend to agglomerate, since the pure cosolvent is a nonsolvent for the polymer. The structure and morphology of microspheres were investigated by SEM, TEM and XRD. The obtained polymer microspheres are microcapsules of TiO₂ nanoparticles. The mean particle diameter and particle size distribution of microcapsules, could be controlled by changing the polymer concentration, pre-expansion pressure, temperature and injection distance. The polymer feed compositions are more effective than other factors on the control of particle size.     

微乳液法制备纳米银粒子的结构及其荧光现象研究

采用微乳液法合成了不同粒径的纳米银粒子,考察了环己烷和甲苯作为油相对制备纳米银的影响.对纳米银粒子的尺寸与结构进行了表征,观察到近球形多晶粒子,并有孪晶结构存在,对晶体结构的分析表明银粒子存在不同程度的点阵畸变,晶面间距增大.不同粒径的纳米银粒子氯仿体系可呈现荧光光谱,而纳米银甲苯体系则无荧光发射.结合紫外—可见吸收光谱和电子自旋共振谱对该体系的荧光发射机理进行了分析 关键词： 微乳液 纳米银粒子 纳米晶结构 荧光