纳米颗粒的分散稳定性及其评估方法

纳米颗粒的分散和稳定对纳米尺寸效应的产生至关重要.在分析纳米颗粒在液体介质中的分散过程的基础上,从机理角度探讨了纳米颗粒的静电稳定机制、空间位阻稳定机制和静电位阻稳定机制及其影响.归纳总结了常用的4种分散稳定性评估方法(沉降法、粒度观测法、Zeta电位法、透光率法),并对这些评估方法进行了分析比较,最后对分散稳定性评估方法进行了展望.     

Cu-水纳米流体的分散行为及导热性能研究

通过测定Cu-水纳米悬浮液的Zeta电位和吸光度,采用Hotdisk热物性分析仪测量了其导热系数,探讨了不同pH值和分散剂浓度对Cu-水纳米悬浮液分散稳定性和导热性能的影响.结果表明,pH值和分散剂加入量是影响Cu-水纳米悬浮液分散稳定和导热系数的重要因素.最优化的pH值和分散剂加入量能显著提高水溶液中Cu表面Zeta电位绝对值,增大了颗粒间静电排斥力,悬浮液分散稳定性较好,导热系数较高.从分散稳定和导热系数提高两个方面来考虑,pH=9.5左右被选为最优化值,在0.1%Cu-H2O纳米流体中,0.07%SDBS被选为最优化浓度.另外,Cu-水纳米流体的导热系数随纳米粒子质量分数的增大而增大,呈非线性关系,且比现有理论(Hamilton-Crosser模型)预测值大.     

单分散Fe3O4@SiO2/Au复合纳米颗粒的制备

制备了尺寸为30nm,具有磁响应的单分散Fe3O4@SiO2/Au核壳纳米颗粒,并研究其光学性质。首先利用热分解法制备油酸修饰的Fe3O4纳米粒子,再用反相微乳法制备Fe3O4@SiO2纳米粒子,最后利用表面修饰的氨基还原性,获得Fe3O4@SiO2/Au核壳复合纳米颗粒。分别用TEM、XRD、Zeta电位与粒度分析仪对产物形貌、结构、表面电位和粒径分布进行表征,用紫外-可见分光光度计对光学性质进行了测试。     

纳米Al2O3在水相体系中的分散稳定性研究

主要研究了pH值、分散剂（SDBS、CTAB、GA）种类和分散剂的浓度对纳米Al2O3在水相体系中进行分散时的影响。实验结果表明：pH值在8左右，SDBS、GA作为分散剂时，纳米Al2O3悬浮液的Zeta电位绝对值较大，粒径较小；在pH值为2～3，CTAB作为分散剂时，Al2O3纳米悬浮液的Zeta电位绝对值较大，粒径较小。比较3种分散剂的分散效果，其中在pH为8左右，SDBS作为分散荆时，纳米氧化铝悬浮液的Zeta电位绝对值最大，粒径最小。在此基础上又讨论了最佳分散剂SDBS的浓度对纳米氧化铝悬浮液的影响，当SDBS分散剂的浓度为0.055％左右时，纳米Al2O3在水相体系中稳定分散性较好。     

氧化石墨烯纳米流体分散性及过冷特性研究

以质量分数为0.05%的氧化石墨烯纳米流体为实验对象,测量了不同超声分散时间下氧化石墨烯纳米流体的粒度和Zeta电位分布。同时测定了降温过程中氧化石墨烯纳米流体的过冷度和相变时间,探讨了超声时间对氧化石墨烯纳米流体分散性和过冷特性的影响。实验结果表明,超声分散时间越长,分散性能越好,但在150min后,粒径和Zeta电位大小趋于稳定;且超声分散时间为150min时,过冷度较小,相变时间较短,分别为5.2℃和4870s。     

表面活性剂对二氧化钛纳米流体分散性的影响

通过二步法将纳米二氧化钛分散到去离子水中,制备TiO2-水纳米流体。通过加入3种不同的表面活性剂作为分散剂,即阴离子表面活性剂十二烷基苯磺酸钠(SDBS)、非离子表面活性剂聚乙烯吡咯烷酮(PVP)和阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)制备出3种不同的纳米流体。用纳米粒度分析仪测定纳米流体中的纳米粒子的粒径和粒径分布,用Zeta电位分析仪测量纳米流体的电位,分析了不同浓度、不同种类的表面活性剂对水基TiO2纳米流体分散性的影响。     

Particle Metrix——生命科学领域多功能颗粒表征解决方案的开拓者

正Zeta View产品采用了激光光源照射纳米颗粒悬浮液,利用全黑背景可以观察到单个纳米颗粒的布朗运动和电泳现象,能够实现单个纳米颗粒的跟踪、粒度测量、Zeta电位测量、浓度测量等。Zetaview所具备的单一颗粒跟踪技术,结合经典微电泳     

超细CeO2粉体在醇水混合介质中的超声分散行为

通过测定20nm、200nm、500nm和5μmCeO2粉体在醇水混合介质中的粒度分布、表面电性及分散稳定性,研究了不同粒径级别超细CeO2粉体在体积比为1∶1的醇水系悬浮液中的超声分散行为。实验结果表明:在一定超声功率和超声频率下,不同粒径级别醇水系CeO2悬浮液均存在最佳超声时间。不同粒径级别醇水系CeO2悬浮液的表面电性各不相同;纳米级和亚微米级CeO2在醇水中所带Zeta电位为正值,微米级CeO2的Zeta电位为负值,悬浮液中CeO2粉体的平均粒度越大,其电位绝对值越小。不同粒径级别醇水系CeO2悬浮液的分散稳定性能各不相同;从超声结束后的分散效果来看,亚微米CeO2粉体在醇水混合介质中的分散性能最好;从多个沉降时间段内的稳定性来看,纳米CeO2粉体在醇水混合介质中的稳定性能最好。     

水基钻井液用碳酸钙微米颗粒的分散状况

为了研究水基钻井液用碳酸钙微米颗粒在水溶液中的分散状况,使用扫描电镜对碳酸钙微米颗粒的微观形貌进行了分析,而后在不同搅拌速度、不同p H、不同超声时间等物理分散因素下研究了碳酸钙微米颗粒在水溶液中的粒径分布与Zeta电位变化,又利用不同的分散剂对碳酸钙微米颗粒进行了化学分散.结果表明:长期放置的碳酸钙微米颗粒会发生团聚,中径达6~7μm;采用物理方法分散时,搅拌速度越高,分散效果越好,在10 000 r/min时可使中径达3~4μm;超声作用则使碳酸钙微米颗粒粒径先减小后增大,中径最小可达2.6μm,p H小于10时,粒径随p H的增大而增大,大于10时则随p H的增大而减小;化学分散剂对提高碳酸钙微米颗粒的分散具有显著的作用,其中,无机类分散剂六偏磷酸钠可使碳酸钙微米粒子中径达到1.5μm,并且Zeta电位绝对值显著提高.     

纳米铜粉在无水乙醇中的分散稳定性

为了实现纳米颗粒的分级,研究影响纳米铜粉在无水乙醇中分散稳定性的因素。通过测定纳米铜粉分散在无水乙醇中形成的悬浮液的Zeta电位和吸光度,探讨悬浮液中分散剂的加入量和pH值对纳米Cu粉末在无水乙醇中的分散稳定性的影响。结果表明:当质量分数为0.01%的纳米铜粉分散在无水乙醇中,当分散剂加入量为0.008%(质量分数)时,分散稳定性最好。在此条件下,调节pH将降低其分散稳定性。     

聚合物分散剂对纳米TiO_2水悬浮液分散稳定性的影响

纳米TiO2复合乳胶漆的制备一般要求预先分散纳米TiO2并制成水悬浮液。为了制备稳定分散的纳米TiO2水悬浮液,研究了乳胶漆中常用的分散剂SN5040和PEG对纳米TiO2在水溶液中分散稳定性的影响,并分析了分散剂的作用机理。实验结果表明:SN5040能有效分散纳米TiO2,按照先SN5040后PEG的方式添加一定比例的混合分散剂,PEG能在SN5040吸附层上嵌入式吸附,显著提高了纳米TiO2的Zeta电位值,更有利于纳米TiO2水悬浮液的分散稳定性。红外光谱分析(FT-IR)表明:SN5040主要是通过与表面裸露的Ti4+形成配位键而吸附到纳米TiO2粒子表面上的。     

超细二氧化钛在水溶液中分散性研究

采用沉降法研究了不同分散剂对超细二氧化钛粉末在水溶液中分散性的影响。结果表明:SDS、TPB、聚丙烯酸钠、乙二醇是超细二氧化钛粉末的有效分散剂。通过测定颗粒表面Zeta电位、悬浮体系粘度,分析了分散剂的作用机理。实验结果表明:SDS、TPB、聚丙烯酸钠能显著提高水溶液中二氧化钛表面Zeta电位绝对值,增大了颗粒间静电排斥力,改善了悬浮液稳定性,降低了体系的粘度。而乙二醇能在颗粒表面形成良好的溶剂化层,提高了二氧化钛在水溶液中的分散稳定性。     

纳米TiO2表面吸附聚乙二醇及其分散稳定性的研究

通过四氯化钛水解法制备纳米TiO2，讨论聚乙二醇(PEG)在其水悬浮体系中的吸附行为．IR和吸附实验结果表明：纳米TiO2通过氢键吸附PEG，其表面吸附行为与PEG浓度、PEG分子量、pH值和晶粒尺寸等因素相关．吸附PEG以后，纳米TiO2颗粒的表面电荷和(电位发生变化．悬浮体系吸光度的变化和TEM分析表明：纳米TiO2吸附PEG后，增加了颗粒间的空间位阻作用，有效地阻止了纳米TiO2的团聚；但若PEG加入量达到过饱和，反而会破坏纳米TiO2的分散稳定性．     

Dispersion characteristics of TiO2 particles coated with the SiO2 nano-film by atomic layer deposition

Deposition of SiO2 nanofilm on TiO2 particles using atomic layer deposition method is reported. The SiO2 film was prepared at the room temperature using the chemicals Si(OC2H5)4, C2H5N and H2O as precursor, catalyst and reactant gas, respectively. The thickness, composition and uniformity of the SiO2 coating on TiO2 surface were characterized by FESEM, HRTEM, EDS and XPS measurements. In HRTEM analysis, the growth rate was about 0.33 angstroms/cycle. EDS and XPS analysis showed the surface composition of TiO2 nanoparticles was silicon oxide. Zeta potential, particle size distribution and sedimentation test results indicated that dispersibility of coated nanoparticles was higher than that of uncoated nanoparticles because of the electrostatic repulsion between the SiO2-coated layers on the surface of TiO2 nanoparticles. These results suggested that the SiO2 coating could modify the surface characteristics of the TiO2 nanoparticles and improve the dispersibility of the TiO2 primary nanoparticles.     

用于电泳沉积的TiO2悬浮液分散性能研究

为了制备适合电泳沉积用的稳定悬浮液,在TiO2水基悬浮液中添加了聚乙烯亚胺(PEI)作为分散剂,对TiO2水基悬浮液进行Zeta电位、黏度、粒径以及稳定性测试,研究了PEI分散剂对TiO2分散性能的影响.结果表明通过添加相对于悬浮液中TiO2粉体质量分数0.6%～3.0%的分散剂可以获得高稳定、高分散、低黏度的悬浮液.     

Fluoroalkylsilane treatment of TiO2 nanoparticles in difference pH values: Characterization and mechanism

In this research, TiO₂ nanoparticles were treated with hydrophobic 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (fluorosilane) in acidic, neutral and alkaline conditions. The treated nanoparticles were characterized using FTIR spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction spectroscopy. Reflectance spectra were obtained using UV–vis diffuse reflectance spectroscopy and band gap energy of the various nanoparticles was determined. Zeta potential measurements were used to evaluate colloidal stability of nanoparticles in aqueous media. The mechanism of fluorosilane adsorption on the surface of TiO₂ nanoparticles was investigated using ATR-FTIR spectroscopy and turbidimetric technique.The characterization results revealed that the amorphous fluorosilane adsorbs on the surface of TiO₂ nanoparticles in both neutral (pH 6) and alkaline (pH 11) solutions. The values of the band gap energy for all treated nanoparticles were almost the same, in the range of 3.10–3.18 eV. Zeta potential measurements showed that isoelectric point of the TiO₂ nanoparticles shifts from 6.8 for untreated TiO₂ to 4.4 for treated one. Based on the zeta potential measurement results, it is expected that treated TiO₂ nanoparticles in neutral or alkaline conditions have higher colloidal stability and better dispersion in the aqueous solutions. Hydrophobic character of fluoro specious on the surface of nanoparticles leads the treated nanoparticles migrate towards the suspension surface. Therefore, these treated nanoparticles may be useful for developing self-cleaning coatings with minimal destructive effect on the polymeric matrix.     

溶胶／凝胶法制备纳米TiO2／Al2O3

采用溶胶-凝胶法制备纳米TiO2／Al2O3，考察了陈化温度及络舍比对TiO2／Al2O3比表面积及孔结构参数的影响。结果表明，TiO2／Al2O3平均粒径〈70nm，比表面积超过210m^2／g，平均孔径0．8-1．4nm。适当降低陈化温度及加络合剂有利于TiO2／Al2O3粒子的分散。Al2O3的存在提高了TiO2／Al2O3的热稳定性。     

Characterization of gold nanoparticles in organic or inorganic medium (ethanol/water) fabricated by spark discharge method

In this paper a method of spark discharge method (SDM) for producing gold nanoparticles in organic or inorganic medium (pure ethanol/deionized water) is proposed. The microstructure of SDM-produced gold nanoparticles was examined by Transmission Electron Microscopy. The crystal structure and surface plasmon resonance of the nanoscale gold particles were studied using X-ray diffraction and UV-Visible spectroscopy. Zeta potential analysis showed that negative charges on the particle surface may be contributing to the stability of the suspension. The experiment's results revealed that SDM is an alternative process to synthesize gold nanoparticle suspension with different particle sizes and shapes in different media without any surfactant.     

Optimized method for preparation of TiO2 nanoparticles dispersion for biological study

The objective of the present study was to develop a practical method to prepare a stable dispersion of TiO2 nanoparticles for biological studies. To address this matter a variety of different approaches for suspension of nanoparticles were conducted. TiO2 (rutile/anatase) dispersions were prepared in distilled water following by treated with different ultrasound energies and various dispersion stabilizers (1.0% carboxymethyl cellulose, 0.5% hydroxypropyl methyl cellulose K4M, 100% fetal bovine serum, and 2.5% bovine serum albumin). The average size of dispersed TiO2 (rutile/anatase) nanoparticles was measured by dynamic light scattering device. Agglomerate sizes of TiO2 in distilled water and 100% FBS were estimated using TEM analysis. Sedimentation rate of TiO2 (rutile/anatase) nanoparticles in dispersion was monitored by optical absorbance detection. In vitro cytotoxicity of various stabilizers in 16-HBE cells was measured using MTT assay. The optimized process for preparation of TiO2 (rutile/anatase) nanoparticles dispersion was first to vibrate the nanoparticles by vortex and disperse particles by ultrasonic vibration in distilled water, then to add dispersion stabilizers to the dispersion, and finally to sonicate the nanoparticles in dispersion. TiO2 (rutile/anatase) nanoparticles were disaggregated sufficiently with an ultrasound energy of 33 W for 10 min. The formation of TiO2 (rutile/anatase) agglomerates in distilled water was decreased obviously by addition of 1.0% CMC, 0.5% HPMC K4M, 100% FBS and 2.5% BSA. For the benefit of cell growth, FBS is the most suitable stabilizer for preparation of TiO2 (rutile/anatase) particle dispersions and subsequent investigation of the in vivo and in vitro behavior of TiO2 (rutile/anatase) nanoparticles. This method is practicable to prepare a stable dispersion of TiO2 (rutile/anatase) nanoparticles for at least 120 h.     

非离子表面活性剂对石墨-H2O分散液稳定性的影响

选用非离子表面活性剂(TX-100)作为分散剂,制备了稳定性较好的石墨-H2O分散液.通过测定石墨-H2O分散液的吸光度和Zeta电位,探讨了不同TX-100添加量、pH值、电解质对石墨-H2O分散液稳定性的影响,并分析了作用机理.结果表明,TX-100的添加量存在一个最佳值,以石墨质量为基准,TX-100用量为25%时,分散液稳定性最好;分散液受pH值影响较小,在较宽的pH值范围内都能达到稳定,在pH=3的强酸性环境下,由于电荷中和及分散剂吸附状态的变化导致分散液稳定性下降;电解质的加入严重破坏了体系稳定性;该体系中,主要通过空间斥力使石墨粒子稳定,同时静电斥力也是不可忽略的因素;石墨-H2O分散液的粒径分布及粘度曲线表明,石墨粒子在水中达到良好的分散.