Particle size determination in aluminum hydroxide suspensions using near-infrared transmittance spectroscopy

A new method for particle size determination in polystyrene and aluminum hydroxide suspensions using near-infrared transmittance spectroscopy is described. Mono-dispersed polystyrene particle size standards were used to establish the calibration model. The particle sizes used in the study are similar to the wavelength range of 700-1300 nm, where light scattering is wavelength dependent. The wavelength dependency of near-infrared (NIR) absorbance is found to be linear with the particle size when the analysis is based on the same spectrum starting point (the same absorbance at 700 nm). Partial least squares regression (PLSR) is applied to model this linear relationship. Compared to laser diffraction (LD) the NIR method has similar accuracy and precision in the measurement of particles with a uniform size. For a sample containing multiple sizes of particles, the mean size measured by the NIR method is shown to be weighted by the particle mass. The application of the model to aluminum hydroxide suspension shows that the NIR method is suitable for the detection of particle size changes during the production process and storage. The advantages of the NIR method are that no knowledge of the refractive index and the concentration of a sample are necessary and that the method is fast and easy to operate.     

Measurement of 100 nm and 60 nm Particle Standards by Differential Mobility Analysis

The peak particle size and expanded uncertainties (95 % confidence interval) for two new particle calibration standards are measured as 101.8 nm ± 1.1 nm and 60.39 nm ± 0.63 nm. The particle samples are polystyrene spheres suspended in filtered, deionized water at a mass fraction of about 0.5 %. The size distribution measurements of aerosolized particles are made using a differential mobility analyzer (DMA) system calibrated using SRM^® 1963 (100.7 nm polystyrene spheres). An electrospray aerosol generator was used for generating the 60 nm aerosol to almost eliminate the generation of multiply charged dimers and trimers and to minimize the effect of non-volatile contaminants increasing the particle size. The testing for the homogeneity of the samples and for the presence of multimers using dynamic light scattering is described. The use of the transfer function integral in the calibration of the DMA is shown to reduce the uncertainty in the measurement of the peak particle size compared to the approach based on the peak in the concentration vs. voltage distribution. A modified aerosol/sheath inlet, recirculating sheath flow, a high ratio of sheath flow to the aerosol flow, and accurate pressure, temperature, and voltage measurements have increased the resolution and accuracy of the measurements. A significant consideration in the uncertainty analysis was the correlation between the slip correction of the calibration particle and the measured particle. Including the correlation reduced the expanded uncertainty from approximately 1.8 % of the particle size to about 1.0 %. The effect of non-volatile contaminants in the polystyrene suspensions on the peak particle size and the uncertainty in the size is determined. The full size distributions for both the 60 nm and 100 nm spheres are tabulated and selected mean sizes including the number mean diameter and the dynamic light scattering mean diameter are computed. The use of these particles for calibrating DMAs and for making deposition standards to be used with surface scanning inspection systems is discussed.     

Rapid removal of Hg(II) from aqueous solutions using thiol-functionalized Zn-doped biomagnetite particles

The surfaces of Zn-doped biomagnetite nanostructured particles were functionalized with (3-mercaptopropyl)trimethoxysilane (MPTMS) and used as a high-capacity and collectable adsorbent for the removal of Hg(II) from water. Fourier transform infrared spectroscopy (FTIR) confirmed the attachment of MPTMS on the particle surface. The crystallite size of the Zn-doped biomagnetite was ～17 nm, and the thickness of the MPTMS coating was ～5 nm. Scanning transmission electron microscopy and dynamic light scattering analyses revealed that the particles formed aggregates in aqueous solution with an average hydrodynamic size of 826 ± 32 nm. Elemental analyses indicate that the chemical composition of the biomagnetite is Zn(0.46)Fe(2.54)O(4), and the loading of sulfur is 3.6 mmol/g. The MPTMS-modified biomagnetite has a calculated saturation magnetization of 37.9 emu/g and can be separated from water within a minute using a magnet. Sorption of Hg(II) to the nanostructured particles was much faster than other commercial sorbents, and the Hg(II) sorption isotherm in an industrial wastewater follows the Langmuir model with a maximum capacity of ～416 mg/g, indicating two -SH groups bonded to one Hg. This new Hg(II) sorbent was stable in a range of solutions, from contaminated water to 0.5 M acid solutions, with low leaching of Fe, Zn, Si, and S (<10%).     

Particle formation in ambient MALDI plumes

The ablated particle count and size distribution of four solid matrix materials commonly used for matrix-assisted laser desorption ionization (MALDI) were measured with a scanning mobility particle sizer (SMPS) combined with a light scattering aerodynamic particle sizer (APS). The two particle sizing instruments allowed size measurements in the range from 10 nm to 20 μm. The four solid matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), 4-nitroaniline (NA), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapic acid (SA). A thin film of the matrix was deposited on a stainless steel target using the dried droplet method and was irradiated with a 337 nm nitrogen laser at atmospheric pressure. The target was rotated during the measurement. A large number of nanoparticles were produced, and average particle diameters ranged from 40 to 170 nm depending on the matrix and the laser fluence. These particles are attributed to agglomeration of smaller particles and clusters and/or hydrodynamic sputtering of melted matrix. A coarse particle component of the distribution was observed with diameters between 500 nm and 2 μm. The coarse particles were significantly lower in number but had a total mass that was comparable to that of the nanoparticles. The coarse particles are attributed to matrix melting and spallation. Two of the compounds, CHCA and SA, had a third particle size distribution component in the range of 10 to 30 nm, which is attributed to the direct ejection of clusters.     

多角度动态光散射法的纳米颗粒精确测量

基于动态光散射原理,采用自主研发的多角度动态光散射装置,对纳米及亚微米颗粒粒径准确测量方法进行了探究。自研装置采用带有光阑组的精密入射光路设计,以及匹配液池及Beam-stop设计,极大提高了信噪比;同时避免了测量角度的互补方向上,由于样品池与空气界面折射率不同导致的反射光信号对有效信号的干扰。在此基础上,对不同浓度、粒径的聚苯乙烯(PS)颗粒溶液进行了测定及不确定度分析。结果表明,对同一粒径的PS颗粒,增加颗粒浓度时,多重散射首先发生于大、小测量角度,越接近90°,发生多重散射的浓度越高;随着粒径增大,受不可忽略的颗粒间相互作用的影响,粒径测量结果表现出了强烈的角度依赖性,甚至波动性。     

Laser-induced incandescence: excitation intensity

Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J/cm(2) at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J/cm(2) at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields self-similar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions (f(v)) derived by light extinction validates LII for quantitative determination of f(v) upon calibration for laser fluences ranging from 0.09 to 0.73 J/cm(2).     

Small-angle neutron scattering measurement of silicon nanoparticle size

We have determined the particle size distribution profiles of octane-terminated silicon nanoparticle suspensions, produced using the sonication of electrochemically etched Si wafers. Small-angle neutron scattering data was analyzed separately in high (0.4?nm(-1)相似文献   

自组装制备PEG接枝聚苯乙烯微球的粒径控制

用苯乙烯封端的聚乙二醇(St—PEG)大单体与苯乙烯(St)进行接枝共聚，将得到的双亲性接枝共聚物(PEG—g—PSt)逐步滴加到各种比例的甲醇／水的混合溶剂中，通过该聚合物在混合溶剂中的自组装，制得了PEG—g—PSt微球。用透射电子显微镜(TEM)和激光光散射(LLS)对微球的形态和粒径进行了表征。实验结果表明，改变接枝液组成、接枝液浓度、滴加速度以及混合溶剂组成等反应条件可有效地控制所得微球的粒径及其分布。     

单分散纳米聚苯乙烯微球的制备及在多孔炭材料中的应用

在超声波辅助下通过微乳液聚合法制备出纳米PS微球,利用重力沉降法制备出聚苯乙烯胶晶阵列,以该阵列为大孔模板制备出大孔一介孔分级炭材料,利用激光粒度仪、场发射扫描电镜、红外和N2物理吸附及解吸附技术对产品的形貌、微观结构及性能进行表征与研究,结果表明,采用超声波辅助微乳液聚合可实现粒径在50nm-500nm范围内聚苯乙烯纳米球的可控制备,增大KPS和PVP用量,PS粒径均会变小,St／SDSN要有适合的比例才能保证PS粒径小且单分散均一。     

种子溶胀法合成微米级单分散聚苯乙烯微球

采用种子溶胀法合成1~10μm单分散聚苯乙烯微球,研究单体与种子微球的不同质量比、聚合温度、分散介质中乙醇浓度以及搅拌速度对聚苯乙烯微球粒径和粒径分布的影响。结果表明,随着单体与种子质量比的增大和聚合温度的升高,微球粒径越大,粒径分布变宽;合成聚苯乙烯微球的适宜条件是单体与种子的质量比范围为0.5~3.5,聚合温度为70~75℃,搅拌速率为150~350 r/min,乙醇在分散介质中的质量分数为10%~15%;合成的粒径分别为6、7、8μm的聚苯乙烯微球的球形度大于96%,粒径相对标准偏差小于5%。     

细乳液聚合制备聚苯乙烯包覆溶剂蓝36的纳米色料

通过细乳液聚合成功制备了聚苯乙烯包覆溶剂蓝36的纳米色料乳胶液。系统研究了憎水剂的种类、乳化剂的浓度、染料浓度以及均化时间对纳米色料微观形貌的影响。结果表明,当乳化剂马来酸酐单十六酯羧酸钠(HEC16)浓度控制在13.3mmol/L～20mmol/L之间,均化时间控制在20min,染料加入量控制在单体质量的10%左右的时候,采用十二烷基硫醇作为憎水剂,可以制备出粒径小于100nm、粒径分布窄且具有核壳结构的高颜色亮度的纳米色料乳胶粒子。     

Commercial spectrophotometer for particle sizing

Particle-size distribution and the concentration of polystyrene particles suspended in water were accurately recovered from the inversion of spectral extinction data measured with a commercial spectrophotometer. The instrument was modified by placing a spatial filter in the collection optics to prevent low-angle scattered light from affecting the measurement of transmitted power. The data were inverted by use of a nonlinear iterative algorithm. When the extinction coefficient is measured in the lambda range of 0.3-1.1 mum, the particle distributions can be retrieved over a diameter range of 0.6-2.8 mum for a wide interval of sample concentrations. The average diameters are recovered with a precision of better than +/-1% and with accuracies consistent with the uncertainties by which the nominal diameters are known. The relative standard deviations of distributions corresponding to monodisperse samples are +/-5-10%, whereas the accuracy on the measured concentrations is ~5%.     

Metal nanoparticles generated by laser ablation

We study a new method for producing ultrafine metal particles (nanopartides) that employs Laser Ablation of Microparticles (LAM). Pulsed excimer laser radiation at 248 nm wavelength was used to ablate ~2 μm feedstock of silver, gold, andpermalloy (Ni₈₁%:Fe_19%) under both normal atmospheric conditions and in other gases and pressures. A model for nanoparticle formation by LAM is proposed that includes plasma breakdown and shock-wave propagation through the initial microparticle. Behind the shock a large fraction of the original microparticle mass is converted to nanoparticles that diffuse to silicon substrates and TEM grids for collection and analysis. Nanoparticle morphologies are spherical except for gold nanoparticles >100 nm that are generally cubes. Electron micrographs of the samples were analyzed by computer-aided image processing to determine the effect of irradiation conditions on the nanoparticle size distribution. The results showed that mean particle diameters were normally in the range from 10 to 100 nm and that the particle size distributions were generally log-normal, with dispersion (diameter/standard deviation) ranging from 0.2 to 0.5. For metallic microparticle feedstock, the mean size of the produced nanoparticles generally increased with increasing laser fluence and were smallest for fluences not too far above the breakdown threshold.     

微米、纳米颗粒国家标准测量装置的研究

研究的目标是建立一套可溯源至激光波长的微米、纳米颗粒国家标准测餐装置,它用扫描电子显微镜高倍数放大、对准和定位颗粒影像,采用纳米位移扫描工作台和激光干涉仪测量微米、纳米量级的标准颗粒直径,其测量标准不确定度可优于5 nm+5×10~(-3).通过文中测量认证的标准颗粒校准各类不同原理和测量范围的颗粒测量仪器,达到各型颗粒测量仪器的量值准确和统一,并溯源至激光光波波长.     

Quantitative sizing of nano/microparticles with a tunable elastomeric pore sensor

The use of a "size-tunable" polyurethane resistive pulse sensor for quantitative sizing of nano- and microparticles is presented. A linear relationship, as first suggested by Maxwell, between particle volume and change in electric resistance across the pore was observed. Particle sizes were quantified for a given size-tunable membrane, by first creating a linear calibration curve to a series of monodisperse carboxylated polystyrene particles of various diameters and then applying this curve to calculate the size of "unknown" nanoparticles. The diameters of a selection of synthetic and biological particles, being PMMA and nonfunctionalized polystyrene particles, along with biological nanoparticles (adenovirus) were calculated using this methodology. Calculated particle diameters and coefficients of variation were shown to be in good agreement with both transmission electron microscopy and dynamic light scattering results.     

Optical properties of HgTe colloidal quantum dots

Room temperature photodetection with HgTe colloidal quantum films is reported between 2 and 5 μm for particles of sizes between ~5 and ~12 nm diameter, and photodetection extends to 7 μm at 80 K. The size-tuning of the absorption of HgTe colloidal quantum dots, their optical cross section and the infrared absorption depth of films are measured. The tuning with radius is empirically given by [see formula in text] where R is in nm. The optical cross section of the colloidal dots at 415 nm is approximately proportional to their volume and given by σ(Hg)(415) = 2.6 ± 0.4 10(-17) cm(2)/mercury atom. The size-dependent optical cross section at the band edge ~1.5 10(-15) cm(2) is consistent with the expected oscillator strength of the quantum dots. The absorption depth of HgTe colloidal dot films is short, about 1-2 μm, which is an advantage for thin film devices. These properties agree rather well with the expectation from the k · p model. HgTe colloidal quantum dot thin films show a strong tuning with temperature with a large positive thermal shift between 0.4 and 0.2 meV K(-1), decreasing with decreasing size within the size range studied and this is attributed primarily to electron-phonon effects.     

Muller matrix measurements of small spherical particles deposited on a c-Si wafer

Müller matrix ellipsometry measurements are performed on accurately sized polystyrene latex and silicon oxide spherical particles deposited on a crystalline silicon surface. The mean particle diameter ranges from 0.2 to 1.5 microm. An argon laser beam (wavelength, 515 nm) impinges on the sample at a fixed near-grazing-incidence angle. The Müller matrix of the diffuse light scattered by the particles is measured in the plane of incidence as a function of the scattering angle. Results are presented and compared with Bobbert and Vlieger's theory. In particular the validity range of Videen's model is estimated.     

Synthesis of ultra-small silicon nanoparticles by femtosecond laser ablation of porous silicon

We report a detailed study on the synthesis of ultra-small (1–10 nm) colloidal silicon nanoparticles (Si NPs) by ablating porous silicon (pSi) in acetone using femtosecond laser pulses. Porous silicon is considered as a target material for ablation because it contains a large number of light emitting silicon nanoparticles. The pSi samples were prepared by anodic etching of silicon in aqueous HF solution for different etching current densities. Transmission electron microscope measurements confirmed the successful formation of well-isolated spherical silicon nanoparticles. The average size of spherical NPs were estimated to be ~7.6, ~7, and ~6 nm when anodic etching current densities of 5, 10, and 20 mA/cm² were used respectively for preparing pSi targets. The crystallinity of these Si NPs was confirmed by selective area electron diffraction and Raman spectroscopy measurements. The observed blue shift in the absorption and emission spectra are attributed to reduction in the average particle size with increase in etching current density. These Si NPs may be useful for fabricating low-dimensional microelectronic compatible photonic devices.     

Integration of zinc oxide nanoparticles into transparent poly(butanediolmonoacrylate) via photopolymerisation

A new method for the preparation of transparent ZnO/PBDMA nanocomposites (PBDMA = poly(butanediolmonoacrylate)) is reported. Zinc oxide nanocrystals (4-10 nm) were synthesized in ethanol and then transferred into butanediolmonoacrylate (BDMA) to obtain a transparent and stable colloidal suspension. No further growth or aggregation of the particles could be observed, after dispersing the particles in the monomer. Effective size control in the range of 6-10 nm and concentrations up to 10 wt% zinc oxide were demonstrated for these systems. The particles and suspensions were characterized by transmission electron microscopy, X-ray diffraction, UV-VIS spectroscopy and dynamic light scattering. The addition of trimethylolpropane triacrylate (TMPTA) and a photoinitiator to the ZnO/BDMA suspension lead to a UV-curable liquid. Photoinduced polymerization was used to produce transparent nanocomposites containing the nanoparticles. The material exhibits a strong UV absorption below 360 nm, a high transmission (90%) in the visible spectral range and a green photoluminescence.     

Investigation of charging behavior of PS particles in nonpolar solvents

The charging behavior of PS (polystyrene) particles dispersed in nonpolar solvent containing surfactant AOT (sodium di-2-ethylhexylsulfosuccinate) was researched by phase angle light scattering (PALS). The effects of the AOT concentration, the particle concentration and the particle size on the zeta potential of the particles were analyzed systemically. The results showed, at different particle concentrations (expressed in the volume fraction of 10(-5)-10(-3)), that the zeta potential could be adjusted by surfactant AOT over a wide concentration range of 0.001-100 mM. An obvious difference of zeta potential on particle concentration was revealed between the high AOT concentrations (beyond 10 mM) and the low ones (below 1 mM). Meantime, it was found that the relationship of particle size to zeta potential showed a great discrepancy between the dilute particle concentrations (below 10(-4)) and the concentrated ones (beyond 6 × 10(-4)). These findings were consistent with the mechanism of preferential adsorption of the charged micelles in nonpolar solvent.