纳米微粒尺寸的评估

纳米粉体材料简介纳米材料分为纳米粉体材料、纳米固体材料、纳米组装体系三类。

纳米粉体材料是纳米材料中最基本的一类。

纳米固体是由分体材料聚集，组合而成。

而纳米组装体系则是纳米粉体材料的变形。

纳米粉体也叫纳米颗粒，一般指尺寸在1-100nm之间的超细粒子，有人称它是超微粒子。

它的尺度大于原子簇而又小于一般的微粒。

按照它的尺寸计算，假设每个原子尺寸为1埃，那么它所含原子数在1000个-10亿个之间。

它小于一般生物细胞，和病毒的尺寸相当。

细微颗粒一般不具有量子效应，而纳米颗粒具有量子效应；一般原子团簇具有量子效应和幻数效应，而纳米颗粒不具有幻数效应。

纳米颗粒的形态有球形、板状、棒状、角状、海绵状等，制成纳米颗粒的成分可以是金属，可以是氧化物，还可以是其他各种化合物。

纳米粉体材料的基本性质它的性质与以下几个效应有很大的关系：（1）.小尺寸效应随着颗粒的量变，当纳米颗粒的尺寸与光波、传导电子德布罗意波长以及超导态的相干长度或透射深度等物理尺寸特征相当或更小时，周期边界性条件将被破坏，声、光、电、磁、热、力等特性均会出现质变。

由于颗粒尺寸变小所引起的宏观物理性质的变化成为小尺寸效应。

（2）.表面与界面效应纳米微粒尺寸小、表面大、位于表面的原子占相当大的比例。

由于纳米粒径的减小，最终会引起表面原子活性增大，从而不但引起纳米粒子表面原子输送和构型的变化，同时也引起表面电子自旋构象和电子能谱的变化。

以上的这些性质被称为“表面与界面效应”。

（3）量子尺寸效应当粒子尺寸下降到某一值时，金属费米能级附近的电子能级由准连续变成离散能级的现象成为量子尺寸效应。

具体从各方面说来有以下特性：（1）热学特性纳米微粒的熔点，烧结温度比常规粉体要低得多。

这是由于表面与界面效应引起的。

比如：大块的pb的熔点600k，而20nm球形pb微粒熔点降低288k，纳米Ag微粒在低于373k时开始融化，常规Ag的熔点远高于1173k。

还有，纳米TiO2在773k加热出现明显致密化，而大晶粒样品要出现同样的致密化需要再升温873k才能达到，这和烧结温度有很大关系。

纳米材料的结构特征一、概论纳米材料是新型结构材料的一种，主要是指材料的基本结构单元至少有一维处于纳米尺度范围(一般在11100 nm)，并由此具有某些新特性的材料。

纳米材料相对于其他材料而言有五大物理效应即：体积效应、表面效应、量子尺寸效应、量子隧道效应和介电限域效应，这五大效应成就了纳米材料的诸多优势，这里就不一一介绍了。

纳米材料相对于其他材料的优势正是因为其结构的特点，下面讲述纳米材料的结构特征。

二、自然界中存在的纳米材料早在宇宙诞生之初，纳米材料和纳米技术就已经存在了，比如，那些溶洞中的石笋就是一纳米一纳米的生长起来的，所以才千奇百怪；贝壳和牙齿也是一纳米一纳米的生长的，所以才那样坚硬；植物和头发是一纳米一纳米生长的，所以才那样柔韧；荷叶上有用纳米技术生长出来的绒毛，所以才能不沾水，就连人类的身体，也是一纳米一纳米生长起来的，所以才那样复杂。

在地球的漫长演化过程中，自然界的生物，从亭亭玉立的荷花、丑陋的蜘蛛，到诡异的海星，从飞舞的蜜蜂、水面的水黾，到海中的贝壳，从绚丽的蝴蝶、巴掌大的壁虎，到显微镜才能看得到细菌…应该说，它们个个都是身怀多项纳米技术的高手。

它们通过精湛的纳米技艺，或赖以糊口，或赖以御敌，一代一代，在大自然中地顽强存活着，不仅给人们留下了深刻的印象，而且给现代的纳米科技工作者带来了无数灵感和启示。

三、纳米材料的概论1、纳米材料：纳米材料是指三维空间尺度上至少有一维处于纳米量级或由它们作为基本单元构成的材料。

2、纳米科技：纳米科技(纳米科学技术)是指在纳米尺度上研究物质的特性和相互作用以及利用这种特性开发新产品的一门科学技术。

3、纳米结构单元：构成纳米材料的结构单元包括限定的团簇或人造原子团簇、纳米微粒、纳米管、纳米棒、纳米丝、同轴纳米电缆、纳米单层膜及多层膜等。

（1）原子团簇指几个至几百个原子的聚集体，如Fen，CunSm，CnHm（n和m都是整数）和碳簇（C60，C70和富勒烯等）等。

纳米材料小尺寸效应的应用引言：提起“纳米”这个词，可能很多人都听说过，但什么是纳米，什么是纳米材料，可能很多人并不一定清楚，本文主要对纳米及纳米材料的研究现状和发展前景做了简介，相信随着科学技术的发展，会有越来越多的纳米材料走进人们的生活，为人类造福。

纳米技术具有极大的理论和应用价值，纳米材料被誉为“21世纪最有前途的材料”。

关键词：纳米材料小尺寸效应性质分类发展前景一、纳米材料及其性质纳米材料是指在三维空间中至少有一维处于纳米尺度范围(1-100nm)或由它们作为基本单元构成的材料，这大约相当于10~100个原子紧密排列在一起的尺度。

从尺寸大小来说，通常产生物理化学性质显著变化的细小微粒的尺寸在０.１微米以下，即１００纳米以下。

因此，颗粒尺寸在１～１００纳米的微粒称为超微粒材料，也是一种纳米材料。

粒度分布均匀、纯度高、极好分散，其比表面高，具有耐高温的惰性，高活性，属活性氧化铝；多孔性；硬度高、尺寸稳定性好，具有较强的表面酸性和一定的表面碱性，被广泛应用作催化剂和催化剂载体等新的绿色化学材料。

可广泛应用于各种塑料、橡胶、陶瓷、耐火材料等产品的补强增韧，特别是提高陶瓷的致密性、光洁度、冷热疲劳性、断裂韧性、抗蠕变性能和高分子材料产品的耐磨性能尤为显著。

以上这些性能决定了纳米材料在表面效应、小尺寸、量子尺寸效应、量子隧道效应、电子信息领域、航天航空、环保能源等各方面均有应用，尤其是在小尺寸方面的应用。

二、纳米科技的发展现状著名科学家钱学森指出:“纳米科技是21世纪科技发展的重点，会是一次技术革命，而且还会是一次产业革命”。

随着世界发达国家对纳米研究的深入，我国对纳米材料和技术也非常重视，为推动我国纳米技术成果产业化．国家通过财政投资并带动社会投资．希望通过5—10年的努力．造就一批具有市场竞争力的纳米高科技骨干企业。

已先后安排了许多纳米科技的研究项目，并取得显著成绩，纳米技术在许多方面已达到国际领先水平。

综述纳米粒子的尺寸效应——纳米材料小尺寸效应的应用Abstract: The word "nano", many people may have heard of, but what is nano, what is Nano materials, many people may not know, this paper focuses on the nano and nano materials research and the development prospect of the introduction, believe that with the development of science and technology, nano materials will be more and more into the life of the people, for the benefit of mankind. Nanotechnology has great value in theory and application of nano materials, known as the "twenty-first Century's most promising material"关键词：纳米材料小尺寸效应性质分类发展前景1、纳米材料及其性质纳米材料是指在三维空间中至少有一维处于纳米尺度范围(1-100nm)或由它们作为基本单元构成的材料，这大约相当于10~100个原子紧密排列在一起的尺度。

从尺寸大小来说，通常产生物理化学性质显著变化的细小微粒的尺寸在０.１微米以下，即１００纳米以下。

因此，颗粒尺寸在１～１００纳米的微粒称为超微粒材料，也是一种纳米材料。

粒度分布均匀、纯度高、极好分散，其比表面高，具有耐高温的惰性，高活性，属活性氧化铝；多孔性；硬度高、尺寸稳定性好，具有较强的表面酸性和一定的表面碱性，被广泛应用作催化剂和催化剂载体等新的绿色化学材料。

纳米材料的种类和性质摘要：本文简述了纳米材料的基本概念、种类和性质。

关键词：纳米材料；概念；性质；种类正文：1纳米材料概念：从尺寸大小来说，通常产生物理化学性质显著变化的细小微粒的尺寸在0.1微米以下（注1米=100厘米，1厘米=10000微米，1微米=1000纳米，1纳米=10埃），即100纳米以下。

因此，颗粒尺寸在1～100纳米的微粒称为超微粒材料，也是一种纳米材料。

纳米级结构材料简称为纳米材料(nanometer material)，是指其结构单元的尺寸介于1纳米～100纳米范围之间。

由于它的尺寸已经接近电子的相干长度，它的性质因为强相干所带来的自组织使得性质发生很大变化。

并且，其尺度已接近光的波长，加上其具有大表面的特殊效应，因此其所表现的特性，例如熔点、磁性、光学、导热、导电特性等等，往往不同于该物质在整体状态时所表现的性质。

纳米颗粒材料又称为超微颗粒材料，由纳米粒子(nano particle)组成。

纳米粒子也叫超微颗粒，一般是指尺寸在1～100nm间的粒子，是处在原子簇和宏观物体交界的过渡区域，从通常的关于微观和宏观的观点看，这样的系统既非典型的微观系统亦非典型的宏观系统，是一种典型的介观系统，它具有表面效应、小尺寸效应和宏观量子隧道效应。

2纳米材料种类：纳米材料大致可分为纳米粉末、纳米纤维、纳米膜、纳米块体等四类。

其中纳米粉末开发时间最长、技术最为成熟，是生产其他三类产品的基础。

2.1纳米粉末：又称为超微粉或超细粉，一般指粒度在100纳米以下的粉末或颗粒，是一种介于原子、分子与宏观物体之间处于中间物态的固体颗粒材料。

可用于：高密度磁记录材料；吸波隐身材料；磁流体材料；防辐射材料；单晶硅和精密光学器件抛光材料；微芯片导热基片与布线材料；微电子封装材料；光电子材料；先进的电池电极材料；太阳能电池材料；高效催化剂；高效助燃剂；敏感元件；高韧性陶瓷材料（摔不裂的陶瓷，用于陶瓷发动机等）；人体修复材料；抗癌制剂等。

举例说明纳米微粒尺寸常用的方法纳米微粒尺寸的测量方法有很多种，下面将介绍常用的10种方法。

1. 透射电子显微镜（Transmission Electron Microscopy，TEM）TEM是一种常用的纳米微粒尺寸测量方法。

它通过透射电子束来观察样品的微观结构，可以直接测量纳米级颗粒的尺寸。

2. 扫描电子显微镜（Scanning Electron Microscopy，SEM）SEM是一种常用的纳米微粒尺寸测量方法。

它通过扫描电子束来观察样品的表面形貌，可以间接推测纳米级颗粒的尺寸。

3. 动态光散射（Dynamic Light Scattering，DLS）DLS是一种常用的纳米微粒尺寸测量方法。

它利用光散射的原理，通过测量散射光的强度和时间的变化，来推测颗粒的大小和分布。

4. X射线衍射（X-ray Diffraction，XRD）XRD是一种常用的纳米微粒尺寸测量方法。

它利用材料对X射线的衍射来推测颗粒的晶格结构和尺寸。

5. 原子力显微镜（Atomic Force Microscopy，AFM）AFM是一种常用的纳米微粒尺寸测量方法。

它通过探针与样品表面进行相互作用，测量力的变化来推测颗粒的尺寸。

6. 扫描隧道显微镜（Scanning Tunneling Microscopy，STM）STM是一种常用的纳米微粒尺寸测量方法。

它利用电子的隧穿效应，通过探针与样品表面的距离变化来推测颗粒的尺寸。

7. 粒度分析仪粒度分析仪是一种常用的纳米微粒尺寸测量方法。

它通过测量样品中颗粒的沉降速度、散射光强度等参数，来推测颗粒的尺寸。

8. 静态光散射（Static Light Scattering，SLS）SLS是一种常用的纳米微粒尺寸测量方法。

它利用光散射的原理，通过测量散射光的强度和角度的变化，来推测颗粒的大小和分布。

9. 红外光谱（Infrared Spectroscopy，IR）红外光谱是一种常用的纳米微粒尺寸测量方法。

Society Chem.Mater.2010,22,1567–15781567DOI:10.1021/cm902852hNanoparticle,Size,Shape,and Interfacial Effects on Leakage Current Density,Permittivity,and Breakdown Strength of MetalOxide-Polyolefin Nanocomposites:Experiment and TheoryNeng Guo,†Sara A.DiBenedetto,†Pratyush Tewari,‡Michael nagan,*,‡Mark A.Ratner,*,†and Tobin J.Marks*,††Department of Chemistry and the Materials Research Center,Northwestern University,Evanston, Illinois60208-3113and‡Center for Dielectric Studies,Materials Research Institute,The Pennsylvania State University,University Park,Pennsylvania16802-4800Received September11,2009.Revised Manuscript Received December2,2009A series of0-3metal oxide-polyolefin nanocomposites are synthesized via in situ olefin polymeriza-tion,using the following single-site metallocene catalysts:C2-symmetric dichloro[rac-ethylenebisindenyl]-zirconium(IV),Me2Si(t BuN)(η5-C5Me4)TiCl2,and(η5-C5Me5)TiCl3immobilized on methylaluminoxane (MAO)-treated BaTiO3,ZrO2,3-mol%-yttria-stabilized zirconia,8-mol%-yttria-stabilized zirconia, sphere-shaped TiO2nanoparticles,and rod-shaped TiO2nanoparticles.The resulting composite materials are structurally characterized via X-ray diffraction(XRD),scanning electron microscopy(SEM), transmission electron microscopy(TEM),13C nuclear magnetic resonance(NMR)spectroscopy,and differential scanning calorimetry(DSC).TEM analysis shows that the nanoparticles are well-dispersed in the polymer matrix,with each individual nanoparticle surrounded by polymer.Electrical measurements reveal that most of these nanocomposites have leakage current densities of∼10-6-10-8A/cm2;relative permittivities increase as the nanoparticle volume fraction increases,with measured values as high as6.1. At the same volume fraction,rod-shaped TiO2nanoparticle-isotactic polypropylene nanocomposites exhibit significantly greater permittivities than the corresponding sphere-shaped TiO2nanoparticle-isotactic polypropylene nanocomposites.Effective medium theories fail to give a quantitative description of the capacitance behavior,but do aid substantially in interpreting the trends qualitatively.The energy storage densities of these nanocomposites are estimated to be as high as9.4J/cm3.IntroductionFuture pulsed-power and power electronic capacitors will require dielectric materials with ultimate energy storage den-sities of>30J/cm3,operating voltages of>10kV,and milli-second-microsecond charge/discharge times with reliable operation near the dielectric breakdown limit.Importantly, at2and0.2J/cm3,respectively,the operating characteristics of current-generation pulsed power and power electronic capacitors,which utilize either ceramic or polymer dielectric materials,remain significantly short of this goal.1An order-of-magnitude improvement in energy density will require the development of dramatically different types of materials, which substantially increase intrinsic dielectric energy den-sities while reliably operating as close as possible to the die-lectric breakdown limit.For simple linear response dielectric materials,the maximum energy density is defined in eq1,U e¼12εrε0E2ð1Þwhereεr is the relative dielectric permittivity,E the dielec-tric breakdown strength,andε0the vacuum permittivity (8.8542Â10-12F/m).Generally,metal oxides have large permittivities;however,they are limited by low breakdown fields.While organic materials(e.g.,polymers)can provide high breakdown strengths,their generally modest permit-tivities have limited their application.1Recently,inorganic-polymer nanocomposite materials have attracted great interest,because of their potential for high energy densities.2By integrating the complementary*Authors to whom correspondence should be addressed.E-mail addresses: mxl46@(M.T.L.),ratner@(M.A.R.),and t-marks@(T.J.M.).(1)(a)Pan,J.;Li,K.;Li,J.;Hsu,T.;Wang,Q.Appl.Phys.Lett.2009,95,022902.(b)Claude,J.;Lu,Y.;Li,K.;Wang,Q.Chem.Mater.2008, 20,2078–2080.(c)Chu,B.;Zhou,X.;Ren,K.;Neese,B.;Lin,M.;Wang,Q.;Bauer,F.;Zhang,Q.M.Science2006,313,334–336.(d) Cao,Y.;Irwin,P.C.;Younsi,K.IEEE Trans.Dielectr.Electr.Insul.2004,11,797–807.(e)Nalwa,H.S.,Ed.Handbook of Low and High Dielectric Constant Materials and Their Applications;Academic Press:New York,1999;V ol.2.(f)Sarjeant,W.J.;Zirnheld,J.;MacDougall,F.W.IEEE Trans.Plasma Sci.1998,26,1368–1392.(2)(a)Kim,P.;Doss,N.M.;Tillotson,J.P.;Hotchkiss,P.J.;Pan,M.-J.;Marder,S.R.;Li,J.;Calame,J.P.;Perry,J.W.ACS Nano 2009,3,2581–2592.(b)Li,J.;Seok,S.I.;Chu,B.;Dogan,F.;Zhang, Q.;Wang,Q.Adv.Mater.2009,21,217–221.(c)Li,J.;Claude,J.;Norena-Franco,L.E.;Selk,S.;Wang,Q.Chem.Mater.2008,20, 6304–6306.(d)Gross,S.;Camozzo,D.;Di 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suggesting that large inclusion-matrix interfacial areas should afford greater polarization levels,dielectric response,and breakdown strength.4 Inorganic-polymer nanocomposites are typically pre-pared via mechanical blending,5solution mixing,6in situ radical polymerization,7and in situ nanoparticle syn-thesis.8However,host-guest incompatibilities intro-duced in these synthetic approaches frequently result in nanoparticle aggregation and phase separation over largelength scales,9which is detrimental to the electrical prop-erties of the composite.10Covalent grafting of the poly-mer chains to inorganic nanoparticle surfaces has alsoproven promising,leading to more effective dispersionand enhanced electrical/mechanical properties;11how-ever,such processes may not be optimally cost-effective,nor may they be easily scaled up.Furthermore,thedevelopment of accurate theoretical models for the di-electric properties of the nanocomposite must be accom-panied by a reliable experimental means to achievenanoparticle deagglomeration.In the huge industrial-scale heterogeneous or slurryolefin polymerization processes practiced today,SiO2isgenerally used as the catalyst support.12Very large localhydrostatic pressures arising from the propagating poly-olefin chains are known to effect extensive SiO2particlefracture and lead to SiO2-polyolefin composites.12Based on this observation,composite materials with enhancedmechanical properties13have been synthesized via in situpolymerizations using filler surface-anchored Ziegler-Natta or metallocene polymerization catalysts.14There-fore,we envisioned that processes meditated by rationallyselected single-site metallocene catalysts supported onferroelectric oxide nanoparticles15might disrupt ubiqui-tous and problematic nanoparticle agglomeration,16toafford homogeneously dispersed nanoparticles within thematrix of a processable,high-strength commodity poly-mer,already used extensively in energy storage capaci-tors.17Moreover,we envisioned that 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(17)Rabuffi,M.;Picci,G.IEEE Trans.Plasma Sci.2002,30,1939–1942.Article Chem.Mater.,Vol.22,No.4,20101569polyolefin -ferroelectric permittivity contrast.If too large,such contrasts are associated with diminished breakdown strength and suppressed permittivity.18,19In a brief preliminary communication,we reported evidence that high-energy-density BaTiO 3-and TiO 2-isotactic polypropylene nanocomposites could be pre-pared via in situ propylene polymerization mediated by anchoring/alkylating/activating C 2-symmetric dichloro-[rac -ethylenebisindenyl]zirconium(IV)(EBIZrCl 2)on the MAO-treated oxide nanoparticles (see Scheme 1).20The resulting nanocomposites were determined to have rela-tively uniform nanoparticle dispersions and to support remarkably high projected energy storage densities ;as high as 9.4J/cm 3,as determined from permittivity and dielectric breakdown measurements.In this contribution,we significantly extend the inorganic inclusion scope to include a broad variety of nanoparticle types,to investi-gate the effects of nanoparticle identity and shape on the electrical/dielectric properties of the resulting nanocom-posites,and to compare the experimental results with theoretical predictions.We also extend the scope of metallocene polymerization catalysts (see Chart 1)and olefinic monomers,with the goal of achieving nanocom-posites that have comparable or potentially greater pro-cessability and thermal stability.Here,we present a full discussion of the synthesis,microstructural and electrical characterization,and theoretical modeling of these nano-composites.It will be seen that nanoparticle coating with MAO and subsequent in situ polymerization are crucial to achieving effective nanoparticle dispersion,and,simul-taneously,high nanocomposite breakdown strengths (as high as 6.0MV/cm)and high permittivities (as high as 6.1)can be realized to achieve energy storage densities as high as 9.4J/cm 3.Experimental SectionI.Materials and Methods.All manipulations of air-sensitive materials were performed with rigorous exclusion of O 2and moisture in flamed Schlenk-type glassware on a dual-manifold Schlenk line or interfaced to a high-vacuum line (10-5Torr),or in a dinitrogen-filled MBraun glovebox with a high-capacity recirculator (<1ppm O 2and H 2O).Argon (Airgas,pre-purified),ethylene (Airgas,polymerization grade),and propy-lene (Matheson or Airgas,polymerization grade)were purified by passage through a supported MnO oxygen-removal column and an activated Davison 4A molecular sieve column.Styrene (Sigma -Aldrich)was dried sequentially for a week over CaH 2and then triisobutylaluminum,and it was freshly vacuum-transferred prior to polymerization experiments.The monomer 1-octene (Sigma -Aldrich)was dried over CaH 2and was freshly vacuum-transferred prior to polymerization experiments.To-luene was dried using activated alumina and Q-5columns,according to the method described by Grubbs,21and it was additionally vacuum-transferred from Na/K alloy and stored in Teflon-valve sealed bulbs for polymerization experiments.Ba-TiO 3and TiO 2nanoparticles were kindly provided by Prof.Fatih Dogan (University of Missouri,Rolla)and Prof.Thomas Shrout (Penn State University),respectively.20ZrO 2nanopar-ticles were purchased from Sigma -Aldrich.The reagents 3-mol %-yttria-stabilized zirconia (TZ3Y)and 8-mol %-yttria-stabilized zirconia (TZ8Y)nanoparticles were purchased from Tosoh,Inc.TiO 2nanorods were purchased from Reade Ad-vanced Materials (Riverside,RI).All of the nanoparticles were dried in a high vacuum line (10-5Torr)at 80°C overnight to remove the surface-bound water,which is known to affect the dielectric breakdown performance adversely.22The deuteratedScheme 1.Synthesis of Polyolefin -Metal OxideNanocompositesChart 1.Metallocene polymerization catalysts andMAO.(18)(a)Li,J.Y.;Zhang,L.;Ducharme,S.Appl.Phys.Lett.2007,90,132901/1–132901/3.(b)Li,J.Y .;Huang,C.;Zhang,Q.M.Appl.Phys.Lett.2004,84,3124–3126.(19)Cheng,Y.;Chen,X.;Wu,K.;Wu,S.;Chen,Y.;Meng,Y.J.Appl.Phys.2008,103,034111/1–034111/8.(20)Guo,N.;DiBenedetto,S.A.;Kwon,D.-K.;Wang,L.;Russell,M.T.;Lanagan,M.T.;Facchetti,A.;Marks,T.J.J.Am.Chem.Soc.2007,129,766–767.(21)Pangborn,A.B.;Giardello,M.A.;Grubbs,R.H.;Rosen,R.K.;Timmers,anometallics 1996,15,1518–1520.(22)(a)Hong,T.P.;Lesaint,O.;Gonon,P.IEEE Trans.Dielectr.Electr.Insul.2009,16,1–10.(b)Ma,D.;Hugener,T.A.;Siegel,R.W.;Christerson,A.;M artensson,E.;€Onneby,C.;Schadler,L.S.Nano-technology 2005,16,724–731.(c)Ma,D.;Siegel,R.W.;Hong,J.;Schadler,L.S.;M artensson,E.;€Onneby,C.J.Mater.Res.2004,19,857–863.1570Chem.Mater.,Vol.22,No.4,2010Guo et al. solvent1,1,2,2-tetrachloroethane-d2was purchased fromCambridge Isotope Laboratories(g99at.%D)and was usedas-received.Methylaluminoxane(MAO;Sigma-Aldrich)waspurified by removing all the volatiles in vacuo from a1.0Msolution in toluene.The reagents dichloro[rac-ethylenebisin-denyl]zirconium(IV)(EBIZrCl2),and trichloro(pentamethyl-cyclopentadienyl)titanium(IV)(Cp*TiCl3)were purchasedfrom Sigma-Aldrich and used as-received.Me2Si(t BuN)(η5-C5Me4)TiCl2(CGCTiCl2)was prepared according to publishedprocedures.23nþ-Si wafers(root-mean-square(rms)roughnessof∼0.5nm)were obtained from Montco Silicon Tech(SpringCity,PA),and aluminum substrates were purchased fromMcMaster-Carr(Chicago,IL);both were cleaned according to standard procedures.24II.Physical and Analytical Measurements.NMR spectra were recorded on a Varian Innova400spectrometer(FT400 MHz,1H;100MHz,13C).Chemical shifts(δ)for13C spectra were referenced using internal solvent resonances and are reported relative to tetramethylsilane.13C NMR assays of polymer microstructure were conducted in1,1,2,2-tetrachlor-oethane-d2containing0.05M Cr(acac)3at130°C.Resonances were assigned according to the literature for isotactic polypro-pylene,poly(ethylene-co-1-octene),and syndiotactic polystyr-ene,respectively(see more below).Elemental analyses were performed by Midwest Microlabs,LLC(Indianapolis,IN). Inductively coupled plasma-optical emission spectroscopy (ICP-OES)analyses were performed by Galbraith Laboratories, Inc.(Knoxville,TN).Powder X-ray diffraction(XRD)patterns were recorded on a Rigaku DMAX-A diffractometer with Ni-filtered Cu K R radiation(λ=1.54184A).Pristine ceramic nanoparticles and composite microstructures were examined with a FEI Quanta sFEG environmental scanning electron microscopy(SEM)system with an accelerating voltage of30 kV.Transmission electron microscopy(TEM)was performed on a Hitachi Model H-8100TEM system with an accelerating voltage of200kV.Samples for TEM imaging were prepared by dipping a TEM grid into a suspension of nanocomposite powder in acetone.Polymer composite thermal transitions were mea-sured on a temperature-modulated differential scanning calori-meter(TA Instruments,Model2920).Typically,ca.10mg of samples were examined,and a ramp rate of10°C/min was used to measure the melting point.To erase thermal history effects, all samples were subjected to two melt-freeze cycles.The data from the second melt-freeze cycle are presented here.III.Electrical Measurements.Metal-insulator-metal (MIM)or metal-insulator-semiconductor(MIS)devices for nanocomposite electrical measurements were fabricated by first doctor-blading nanocomposite films onto aluminum(MIM)or nþ-Si(MIS)substrates,followed by vacuum-depositing top gold electrodes through shadow masks.Specifically,a clean substrate was placed on a hot plate heated to just below the polymer-nanocomposite melting point.A small amount of the polymer nanocomposite powder was placed in the center of the substrate and left until the powder began to melt.Once in this phase,the polymer nanocomposite is spread over the center of the sub-strate using a razor blade.The sample was removed from the heat,cooled,and then pressed in a benchtop press to ensure uniform film thicknesses and smooth surfaces.Gold electrodes 500A thick were vacuum-deposited directly on the films through shadow masks that defined a series of different areas (0.030,0.0225,0.01,0.005,and0.0004cm2)at3Â10-6Torr(at 0.2-0.5A/s).Electrical properties of the films were character-ized by two probe current-voltage(I-V)measurements using a Keithley Model6430Sub-Femtoamp Remote Source Meter, operated by a local LABVIEW program.Triaxial and low triboelectric noise coaxial cables were incorporated with the Keithley remote source meter and Signatone(Gilroy,CA)probe tip holders to minimize the noise level.All electrical measure-ments were performed under ambient conditions.For MIS devices,the leakage current densities(represented by the symbol J,given in units of A/cm2)were measured with positive/negative polarity applied to the gold electrode to ensure that the nþ-Si substrate was operated in accumulation.A delay time of1s was incorporated into the source-delay-measure cycle to settle the source before recording currents.Capacitance measurements of the MIM and MIS structures were performed with a two-probe digital capacitance meter(Model3000,GLK Instruments,San Diego,CA)at(5and24kHz.Several methods have been developed to measure the dielectric breakdown strength of polymer and nanocomposite films.1a,25In this study,various methods were examined(e.g.,pull-down electrodes25),and the two-probe method was used to collect the present data because the top gold electrodes had already been deposited for leakage current and capacitance measurements.The dielectric break-down strength of the each type of composite film was measured in a Galden heat-transfer fluid bath at room temperature with a high-voltage amplifier(Model TREK30/20A,TREK,Inc., Medina,NY)with a ramp rate of1000V/s.26The thicknesses of the dielectric films were measured with a Tencor P-10step profilometer,and these thicknesses were used to calculate the dielectric constants and breakdown strengths of the film sam-ples(see Table2,presented later in this work).IV.Representative Immobilization of a Metallocene Catalyst on Metal Oxide Nanoparticles.In the glovebox,2.0g of BaTiO3 nanoparticles,200mg of MAO,and50mL of dry toluene were loaded into a predried100-mL Schlenk reaction flask,which was then attached to the high vacuum line.Upon stirring,the mixture became a fine slurry.The slurry was next subjected to alternating sonication and vigorous stirring for2days with constant removal of evolving CH4.Next,the nanoparticles were collected by filtration and washed with fresh toluene(50mLÂ4) to remove any residual MAO.Then,200mg of metallocene catalyst EBIZrCl2and50mL of toluene were loaded in the flask containing the MAO-coated nanoparticles.The color of the nanoparticles immediately became purple.The slurry mixture was again subjected to alternating sonication and vigorous Table1.XRD Linewidth Analysis Results for the Oxide-PolypropyleneNanocompositespowder2θ(deg)full width athalf maximum,fwhm(deg)crystallitesize,L(nm)a BaTiO331.4120.25435.6 BaTiO3-polypropylene31.6490.27132.8 TiO225.3600.31727.1 TiO2-polypropylene25.3580.36123.5a Crystallite size(L)is calculated using the Scherrer equation:L=0.9λ/[B(cosθB)whereλis the X-ray wavelength,B the full width at half maximum(fwhm)of the diffraction peak,andθB the Bragg angle.(23)Stevens,J.C.;Timmers,F.J.;Wilson,D.R.;Schmidt,G.F.;Nickias,P.N.;Rosen,R.K.;Knight,G.W.;Lai,S.Eur.Patent Application EP416815A2,1991.(24)Yoon,M.-H.;Kim,C.;Facchetti,A.;Marks,T.J.J.Am.Chem.Soc.2006,128,12851–12869.(25)Claude,J.;Lu,Y.;Wang,Q.Appl.Phys.Lett.2007,91,212904/1–212904/3.(26)Gadoum,A.;Gosse,A.;Gosse,J.P.Eur.Polym.J.1997,33,1161–1166.Article Chem.Mater.,Vol.22,No.4,20101571stirring overnight.The nanoparticles were then collected by filtration and washed with fresh toluene until the toluene remained colorless.The nanoparticles were dried on the high-vacuum line overnight and stored in a sealed container in the glovebox at-40°C in darkness.V.Representative Synthesis of an Isotactic Polypropylene Nanocomposite via In Situ Propylene Polymerization.In the glovebox,a250-mL round-bottom three-neck Morton flask, which had been dried at160°C overnight and equipped with a large magnetic stirring bar,was charged with50mL of dry toluene,200mg of functionalized nanoparticles,and50mg of MAO.The assembled flask was removed from the glovebox and the contents were subjected to sonication for30min with vigorous stirring.The flask was then attached to a high vacuum line(10-5Torr),the catalyst slurry was freeze-pump-thaw degassed,equilibrated at the desired reaction temperature using an external bath,and saturated with1.0atm(pressure control using a mercury bubbler)of rigorously purified propylene while being vigorously stirred.After a measured time interval,the polymerization was quenched by the addition of5mL of methanol,and the reaction mixture was then poured into800 mL of methanol.The composite was allowed to fully precipitate overnight and was then collected by filtration,washed with fresh methanol,and dried on the high vacuum line overnight to constant weight.VI.Representative Synthesis of a Poly(ethylene-co-1-octene) Nanocomposite via In Situ Ethyleneþ1-Octene Copolymeriza-tion.In the glovebox,a250-mL round-bottom three-neck Morton flask,which had been dried at160°C overnight and equip-ped with a large magnetic stirring bar,was charged with50mL of dry toluene,200mg of functionalized nanoparticles,and 50mg of MAO.The assembled flask was removed from the glo-vebox and the contents were subjected to sonication for30min with vigorous stirring.The flask was then attached to a high vacuum line(10-5Torr),the catalyst slurry was freeze-pump-thaw degassed,equilibrated at the desired reaction temperature using an external bath,and saturated with1.0atm(pressure control using a mercury bubbler)of rigorously purified ethylene while being vigorously stirred.Next,5mL of freshly vacuum-transferred1-octene was quickly injected into the rapidly stirred flask using a gas-tight syringe equipped with a flattened spraying needle.After a measured time interval,the polymerization was quenched by the addition of5mL of methanol,and the reaction mixture was then poured into800mL of methanol.The com-posite was allowed to fully precipitate overnight and was then collected by filtration,washed with fresh methanol,and dried on the high vacuum line overnight to constant weight.Film fabri-cation of the composite powders into thin films for MIS electrical testing was unsuccessful due to the high incorporation level of1-octene.VII.Representative Synthesis of a Syndiotactic Polystyrene Nanocomposite via In Situ Styrene Polymerization.In the glove-box,a250-mL round-bottom three-neck Morton flask,which had been dried at160°C overnight and equipped with a large magnetic stirring bar,was charged with50mL of dry toluene, 200mg of functionalized nanoparticles,and50mg of MAO.The assembled flask was removed from the glovebox and the con-tents were subjected to sonication for30min with vigorous stirring.The flask was then attached to a high vacuum line(10-5 Torr)and equilibrated at the desired reaction temperature usingTable2.Electrical Characterization Results for Metal Oxide-Polypropylene Nanocomposites aentry compositenanoparticlecontent b(vol%)melting temperature,T m c(°C)permittivity dbreakdownstrength e(MV/cm)energy density,U f(J/cm3)1BaTiO3-iso PP0.5136.8 2.7(0.1 3.1 1.2(0.1 2BaTiO3-iso PP0.9142.8 3.1(1.2>4.8>4.0(0.6 3BaTiO3-iso PP 2.6142.1 2.7(0.2 3.9 1.8(0.2 4BaTiO3-iso PP 5.2145.6 2.9(1.0 2.7 1.0(0.3 5BaTiO3-iso PP 6.7144.8 5.1(1.7 4.1 3.7(1.2 6BaTiO3-iso PP13.6144.8 6.1(0.9>5.9>9.4(1.37s TiO2-iso PP g0.1135.2 2.2(0.1>2.8>0.8(0.1 8s TiO2-iso PP g 1.6142.4 2.8(0.2 4.1 2.1(0.2 9s TiO2-iso PP g 3.1142.6 2.8(0.1 2.8 1.0(0.1 10s TiO2-iso PP g 6.2144.8 3.0(0.2 4.7 2.8(0.211r TiO2-iso PP h 1.4139.7 3.4(0.3 1.00.40(0.35 12r TiO2-iso PP h 3.0142.4 4.1(0.70.90.22(0.09 13r TiO2-iso PP h 5.1143.7 4.9(0.40.90.23(0.0814ZrO2-iso PP 1.6142.9 1.7(0.3 1.50.1815ZrO2-iso PP 3.9145.2 2.0(0.4 1.90.3216ZrO2-iso PP7.5144.9 4.8(1.1 1.00.2017ZrO2-iso PP9.4144.4 6.9(2.6 2.0 1.02(0.7318TZ3Y-iso PP 1.1142.9 1.1(0.1N/A N/A19TZ3Y-iso PP 3.1143.5 1.8(0.2N/A N/A20TZ3Y-iso PP 4.3143.8 2.0(0.2N/A N/A21TZ3Y-iso PP 6.7144.9 2.7(0.2N/A N/A22TZ8Y-iso PP0.9142.9 1.4(0.1 3.8 1.07(0.04 23TZ8Y-iso PP 2.9143.2 1.8(0.1 2.80.5924TZ8Y-iso PP 3.8143.2 2.0(0.2 2.00.4125TZ8Y-iso PP 6.6146.2 2.4(0.4 2.20.61a Polymerizations performed in50mL of toluene under1.0atm of propylene at20°C.b From elemental analysis.c From differential scanning calorimetry(DSC).d Derived from capacitance measurements.e Calculated by dividing the breakdown voltage by the film thickness,which is measured using a Tencor p10profilometer.f Energy density(U)is calculated from the following relation:U=0.5ε0εr E b2,whereε0is the permittivity of a vacuum,εr the relative permittivity,and E b the breakdown strength.g The superscripted prefix“s”denotes sphere-shaped TiO2nanoparticles.h The superscripted prefix“r”denotes rod-shaped TiO2nanoparticles.。

纳米颗粒尺寸表面电荷特征参量-概述说明以及解释1.引言1.1 概述纳米颗粒是一种具有特殊尺寸范围的微小粒子，其尺寸通常在1至100纳米之间。

与传统的微粒相比，纳米颗粒具有独特的物理、化学和生物学特性，因此在许多领域都得到了广泛的应用与研究。

纳米颗粒的尺寸是指其三维空间维度的线性度量，即直径或半径。

由于纳米颗粒的尺寸在纳米级别，约为原子和分子的尺寸，因此纳米颗粒与宏观物质之间存在显著的尺寸效应。

这种尺寸效应导致了纳米颗粒的许多独特性质和行为，例如表面积增加、光学性质变化、磁性增强等。

纳米颗粒的表面电荷也是其另一个重要特征。

表面电荷是指纳米颗粒表面的带电状况，可以通过溶液中溶质的电离状态来描述。

由于纳米颗粒相对较小的尺寸，其表面积与体积之比较大，表面带电状况对纳米颗粒的物理、化学和生物学特性具有重要影响。

例如，表面电荷的变化可以影响纳米颗粒的稳定性、相互作用以及在生物体内的吸附和转运等。

特征参量是用来描述和表征纳米颗粒的重要参数和性质的指标。

常见的特征参量包括表面积、体积、形状、晶体结构、光学性质、磁性等。

这些参量可以通过各种实验方法和理论计算来获取和分析，从而揭示纳米颗粒的特性和行为。

本文旨在探讨纳米颗粒的尺寸、表面电荷和特征参量对其性质和应用的重要性和影响因素。

通过对这些方面的综合了解，我们可以更好地理解纳米颗粒的特性，并为其在材料科学、生物医学、环境科学等领域的应用提供理论和实验基础。

本文将依次介绍纳米颗粒尺寸的概念和定义、影响纳米颗粒尺寸的因素，以及纳米颗粒表面电荷的含义和影响因素。

最后，我们将讨论纳米颗粒的特征参量的定义、应用和重要性，并对未来的研究方向进行展望。

1.2文章结构文章结构部分是对整篇文章内容的组织和安排进行介绍的部分。

在本文中，我们将按照以下结构来展开讨论纳米颗粒的尺寸、表面电荷和特征参量的相关内容：2. 正文部分2.1 纳米颗粒尺寸在这一部分，我们将会详细讨论纳米颗粒尺寸的含义和定义，以及影响纳米颗粒尺寸的因素。