Characterization of Silver Nanoparticle Products Using Asymmetric Flow Field Flow Fractionation with a Multidetector Approach - a Comparison to Transmission Electron Microscopy and Batch Dynamic Light Scattering

Due to the already prevalent and increasing use of silver-nanoparticle (Ag-NP) products and the raised concerns in particular for the aquatic environment, analytical techniques for the characterization of such products are of need. However, because Ag-NP products are of different compositions and polydispersities, analysis especially of the size distribution is challenging. In this work, an asymmetric flow field flow fractionation (A4F) multidetector system (UV/vis, light scattering, inductively coupled plasma mass spectrometry - ICPMS), in combination with a method to distinguish and quantify the particle and dissolved Ag fractions (ICPMS after ultracentrifugation), for the characterization of Ag-NP products with different degrees of polydispersities is presented. For validation and to outline benefits and limitations, results obtained from batch dynamic light scattering (batch-DLS) and transmission electron microscopy (TEM) were compared. With the developed method a comprehensive understanding in terms of dissolved Ag and Ag-NP concentration as well as an element selective, mass- and number particle size distribution (PSD) was obtained. In relation to batch-DLS, the reliability of the data was improved significantly. In comparison to TEM, faster measurement times and the ability to determine the samples directly in dispersions are clearly advantageous. The proposed setup shows potential for a rapid- and reliable characterization method of virtually any polydisperse metallic NP dispersion, many of them available on the market already.

Size-fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles

Harald Hagendorfer, Christian Ludwig, Andrea Ulrich

This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size < 100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.

Springer Verlag2010

Application of an asymmetric flow field flow fractionation (AF4) multi-detector approach for metallic ENP characterization - prospects and limitations demonstrated on Au nanoparticles

Harald Hagendorfer, Christian Ludwig, Andrea Ulrich

In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system.

Elsevier2011

A hyphenated SMPS-ICPMS coupling setup: Size-resolved element specific analysis of airborne nanoparticles

Adrian Hess, Christian Ludwig, Mohamed Tarik

Physical and chemical characterization of gas borne particles in the nanometer to sub micrometer size range includes knowledge about particle size distribution and chemical composition, possibly with a high time resolution. However, most of the available techniques are offline methods and/or not able to provide such physical and chemical information simultaneously. Scanning Mobility Particle Sizer (SMPS) is a well established and widely used technique for determining size distribution and number concentration of such particles, within scan durations of a few minutes. Inductively Coupled Plasma Mass Spectrometry (ICPMS) is a highly sensitive multi element technique, allowing the determination of elemental composition with excellent defection limits and a wide dynamic concentration range. In this work, SNIPS and ICPMS were coupled to one hyphenated system which allows achieving on-line and simultaneously size and chemical information with SMPS-Lypical time resolutions. A Rotating Disk Diluter was used as sample introduction interface, and the SMPS flow concept was re designed to fulfill the requirements of both different analytical methods. The developed setup was successfully tested with a model aerosol containing airborne silver nanoparticles. Proper SMPS operation under argon atmosphere instead of air was validated. The presented setup was applied to scan the particle size range from 7 to 156 um within 120s, Similar sensitivities and efficiencies compared to that of state-of-the-art SMPS and ICPMS instruments were achieved. (C) 2015 Elsevier Ltd. All rights reserved.

Elsevier Sci Ltd2015