Size characterization

In the field of nanotechnology, inductively coupled plasma-mass spectrometry (ICP-MS) is commonly applied during the synthesis of nanoparticles. Moreover, several recent approaches have expanded the field of ICP-MS application to the size characterization of nanoparticles. More information about ICP-MS can be found in Chapter 4. 

Besides, neutron and X-ray scattering can also be used for the characterization of nanometallome. More information on neutron and X-ray scattering can be found in Chapter 7. The application of X-ray scattering in characterization of nanometallomes will be shown here later. 

Helfrich et al developed a reliable method for the size characterization of Au nanoparticles based on the combination of two different separation techniques (liquid chromatography and gel electrophoresis), coupled on-line to ICP-MS. Separation by liquid chromatography shows good reproducibility with size-dependent behavior for retention (RSD 1%). The results are in a good agreement with complementary methods like dynamic light scattering (DLS) and transmission electron microscopy (TEM). 

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Dunn C M, Robinson B FI and Leng F J 1990 Photon-correlation spectroscopy applied to the size characterization of water-in-oil microemulstion systems stabilized by aerosol-OT effect of change in the counterion Spectrochim. Acta. A 46 1017... 

When a sample of ca 100 g has been obtained, a representative sample for use in size characterization equipment must then be taken. Some of the more modem methods of size characterization require as Htde as 1 mg of powder, thus obtaining a representative sample can be quite difficult. If the powder flows weU and does not contain too many fines, a device known as the spinning riffler (Fig. 4c) can be used. A spinning riffler consists of a series of cups that rotate under the powder supply. The time of one rotation divided into the time of total powder flow should be as large a number as possible. Although this device has been shown to be very efficient, problems can be encountered on very small (1 mg) samples, and the powder must be processed several times. Moreover, in order to avoid cross-contamination, cleanup after each of the sampling processes can be quite difficult. Furthermore, if the powder is cohesive and does not flow weU, the equipment is not easy to use. A siUca flow agent can be added to the powder to enable the powder to flow... 

A. Hickey, Factors influencing aerosol desposition in inertial impactors and their effect on particle size characterization, Pharm, Tech. (Sept. 1990), pp. 118-120. 

Chiu, C. Y. Chiang, A. S. T. Chao, K. J. 2006. Mesoporous silica powders and films—Pore size characterization by krypton adsorption. Microporous Mesoporous Mater. 91 244-253. 

Woodle MC, Papahadjopoulos D. Liposome preparation and size characterization. Meth Enzymol 1989 171 193. 

Byers, R.L, Davis, J.W., White, E.W., and McMillan, R.E. (1971) A computerized method for size characterization of atmospheric aerosols by the scanning electron microscope. Environ. Sci. Technol, 5, 517-521. 

Chromatographic approaches have been also used to separate nanoparticles from samples coupled to different detectors, such as ICP-MS, MS, DLS. The best known technique for size separation is size exclusion chromatography (SEC). A size exclusion column is packed with porous beads, as the stationary phase, which retain particles, depending on their size and shape. This method has been applied to the size characterization of quantum dots, single-walled carbon nanotubes, and polystyrene nanoparticles [168, 169]. Another approach is hydro-dynamic chromatography (HDC), which separates particles based on their hydro-dynamic radius. HDC has been connected to the most common UV-Vis detector for the size characterization of nanoparticles, colloidal suspensions, and biomolecules [170-172]. 

An inner-sphere complex is formed between Lewis acids and bases, while an outer-sphere complex involves a water molecule interposed between the acid and the base. A hard Lewis acid is a molecular unit of small size, high oxidation state, high electronegativity, and low polarizability whereas a soft Lewis acid is a molecular unit of relatively large size, characterized by low oxidation state, low electronegativity, and high polarizability. Based on this characterization, hard bases prefer to complex hard acids, and soft bases prefer to complex soft acids, under similar conditions of acid-base strength. 

Model Membranes and Their Characteristics Liposome preparation and size characterization, 171, 193 preparation of microcapsules from human erythrocytes use in transport experiments of glutathione and its S-conjugate, 171, 217 planar lipid-protein membranes strategies of formation and of detecting dependencies of ion transport functions on membrane conditions, 171,... 

One algorithm for blindly approximating physical states has already been proposed [36], although the method requires the number of states to be input. In work to be reported soon, Zhang and Zuckerman developed a simple procedure for approximating physical states that does not require input of the number of states. In several systems, moreover, it was found that sample-size estimation is relatively insensitive to the precise state definitions (providing they are reasonably physical, in terms of the timescale discussion above). The authors are therefore optimistic that a "benchmark" blind, automated method for sample-size characterization will be available before long. 

A number of environmental applications [3] have been performed in order to size characterize colloids collected in rivers (riverbome particles, SPM, and sediments), clay samples and ground limestone (from soils), coal particles, diesel soot particles (from combustion processes), or airborne particles in urban areas (from waste incinerators, vehicles, household-heating systems, and manufacturing). In many of these cases, not only the size but also the particle size distribution was important and thus, in conjunction with the traditional UV detector, specific detectors such as ETAAS, ICP-MS, ICP-AES were used [40] in order to obtain more detailed, more specific compositional information. 

The extraction of more complex particle size distributions from PCS data (which is not part of the commonly performed particle size characterization of solid lipid nanoparticles) remains a challenging task, even though several corresponding mathematical models and software for commercial instruments are available. This type of analysis requires the user to have a high degree of experience and the data to have high statistical accuracy. In many cases, data obtained in routine measurements, as are often performed for particle size characterization, are not an adequate basis for a reliable particle size distribution analysis. 

Given the complexity of particle size distributions in the atmosphere (see Chapter 9.A), as well as the large number of chemical components (Chapter 9.C) that are not distributed equally throughout the various sizes, characterizing a typical collection of particles in the atmosphere is not possible. However, some indication of particle levels in the atmosphere is provided by mass measurements of PMm (i.e., total mass less than 10 gm in diameter), for which extensive measurements have been made for regulatory purposes. 

Transmission electron microscopy (TEM) has been an underutilized yet valuable too in particle size characterization of MC particles in LB films. Monolayer films of trioctylphosphine oxide-capped CdSe (18), spread as a monolayer on an aqueous subphase, were transferred to a TEM grid. A close-packed hexagonal arrangement of 5.3-nm (cr —4%) crystallites was found. TEM images were also obtained for HMP-stabilized CdS incorporated in BeH/octadecylamine films (79) and for CdS formed under an amine-based surfactant monolayer and transferred to a TEM grid (14). In one study, direct viewing of CdS and CdSe particles made from Cd2+-FA films on TEM grids was not possible due to poor phase contrast between the particles and the film (30). Diffraction patterns were observed, however, that were consistent with crystalline (3-CdS or CdSe. Approximately spherical particles of CdSe could... 

Two kernels of theoretical isotherms in cylindrical channels have been constructed corresponding to the adsorption and desorption branches. For a series of samples [2-4], we show that the pore size distributions calculated from the experimental desorption branches by means of the desorption kernel satisfactory coincide with those calculated from the experimental adsorption branches by means of the adsorption kernel This provides a convincing argument in favor of using the NLDFT model for pore size characterization of nanoporous materials provided that the adsorption and desorption data are processed consistently,... 

Laser diffraction is the most commonly used instrumental method for determining the droplet size distribution of emulsions. The possibility of using laser diffraction for this purpose was realized many years ago (van der Hulst, 1957 Kerker, 1969 Bohren and Huffman, 1983). Nevertheless, it is only the rapid advances in electronic components and computers that have occurred during the past decade or so that has led to the development of commercial analytical instruments that are specifically designed for particle size characterization. These instruments are simple to use, generate precise data, and rapidly provide full particle size distributions. It is for this reason that they have largely replaced the more time-consuming and laborious optical and electron microscopy techniques. 

C. Nondestructive Physical Tests for Pore Size Characterization... 

Jillavenkatesa A, Dapkunas SJ, Lum HLS. 2001. Special Publication 960-1 Particle size characterization. Washington, DC NIST 165. 

Ravikovitch PI, Vishnyakov A, Russo R, and Neimark AV. Unified approach to pore size characterization of microporous carbonaceous materials from N2, Ar, and C02 adsorption isotherms. Langmuir, 2000 16(5) 2311-2320. 

Separation and Size Characterization of Colloidal Particles in River Water by Sedimentation Field-Flow Fractionation, R. Beckett, G. Nicholson, B. T. Hart, M. Hansen, and J. C. Giddings, Wat. Res., 22, 1535 (1988). 

High-Speed Size Characterization of Chromatographic Silica by Flow/Hyperlayer Field-Flow Fractionation, S. K. Ratanathanawongs and J. C. Giddings, J. Chromatogr., 467, 341 (1989). 

A gradual and regular change in size may appear by itself, that is, without being part of a spiral. A regular change in size characterizes, for example, homologous series, such as the alkanes, C H2 +2,... 

S-FFF has been compared with analytical ultracentrifugation (AUC) with respect to the fractionation of a 10-component latex standard mixture with narrow particle size distribution, known diameters (67-1220 nm) and concentration [ 127]. With an analytical ultracentrifuge, the particle sizes as well as their quantities could be accurately determined in a single experiment whereas in S-FFF deviations from the ideal retention behavior were found for particles >500 nm resulting in smaller particle size determination in the normal as well as in the programmed operation. It was concluded that, without a modified retention equation which accounts for hydrodynamic lift forces and steric exclusion effects, S-FFF cannot successfully be used for the size characterization of samples in that size range. 

Wittgren B (1997) Size characterization of water-soluble polymers using asymmetrical flow field-flow fractionation. PhD Thesis, Lund University, Sweden... 

Giddings JC, Myers MN, Moon MH, Barman BN (1991) Particle separation and size characterization by sedimentation field-flow fractionation. In Provder T (ed) Particle size distribution. American Chemical Society, Washington, DC, pp 198-216... 

Heffel, C., Heitzmann, D., Kramer, H., and Scarlett, B. (1995), paper presented at the 6th European Symp. Particle Size Characterization, Partec 95, Nurenberg, Germany. 

Biocatalyst particle shape and size characterization before and after treatment in the two selected media was examined in order to ascertain the role of the solvent on enzyme structure. The cmde biocatalyst preparation consisted of spherical micro-granules with a mean particle size of about 500 i.m. No particle size modifications were observed by SEM when the biocatalyst was treated by SC-CO2. After treatment in [bmim][PF6] a lower mean particle size of about 430 gm was observed, probably due to partial carrier dissolution. Conversely, by exposing the biocatalyst... 

Wahlund, K.G., MacRitchie F., Nylander T., and Wannerberger, L. (1996). Size characterization of wheat proteins, particularly glutenin, by asymmetrical flow field flow fractionation. 

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