Measurement of the Density of Engineered Silver Nanoparticles Using Centrifugal FFF-TEM and Single Particle ICP-MS

Abstract

A methodology has been developed to measure nanoparticle mass and density, by combining centrifugal field-flow fractionation (CeFFF; more commonly called sedimentation FFF or SdFFF) and transmission electron microscopy (TEM). Particle effective mass obtained from CeFFF retention data and particle size obtained from the TEM images were used to calculate the nanoparticle density. The method was initially applied to measure the density of monodispersed polystyrene latex nanoparticles. Measured densities for latex nanoparticles of 160-300 nm in diameter were in the range of 1041-1063 kg m with standard deviations of 0.6-1.1%. Densities of engineered silver nanoparticles with nominal diameters of 30, 60, 75, and 100 nm were measured using this methodology. For all four silver nanoparticle samples, the measured densities were 18-24% lower than the nominal density of metallic silver, with an overall mean value of 7900 ± 675 kg m. Density values calculated using nanoparticle mass values obtained from single particle inductively coupled plasma-mass spectrometry (spICP-MS) measurements, corroborated the CeFFF-TEM results. The difference in the density of the silver nanoparticles compared to that of bulk silver suggests that the synthesis process could impart 20-37% porosity in silver nanoparticles. The data has important implications in the fields of nanomaterial, nanomedicine and nanotoxicology, where assumption of the bulk density for nanoparticles can result in erroneous estimation of parameters such as mass, size, porosity, and dosage. The presented methodology provides a straightforward and reproducible means for measurement of the density and porosity of engineered nanoparticles with a wide range of density and size.

Porosity determination of nano- and sub-micron particles by single particle inductively coupled plasma mass spectrometry

“…It is also difficult to correct for interparticle (interstitial) voids in this classical method. At the same time, spICP-MS measurements can easily provide density values in these cases as well, directly in dispersion form, thus without the need to dry the sample, as it was described by Tadjiki et al [40].…”

Development and Application of Nanoparticle-Nanopolymer Composite Spheres for the Study of Environmental Processes

“…In normal mode, smaller particles will elute the earliest being subject to higher velocity flow lines in the parabolic flow profile ( Giddings, 1993 ; Giddings, 1995 ). Sedimentation field flow fractionation (Sed-FFF) uses a centrifugal force instead of a cross-flow to force particles towards the accumulation wall; separating particles according to their buoyant mass, where less dense particles elute earliest ( Gimbert et al, 2005 ; Tadjiki et al, 2017 ). Taken together these techniques provide information on both the particle size (AF4) and particle density (Sed-FFF).…”

Field‐flow fractionation for nanoparticle characterization

“…A common combination to study inorganic and mixed organic/inorganic NPs involves UV-Vis and ICP-MS [26,39,41,47,48]. Sometimes ICP-MS analysis was performed on fractions collected after FFF [49]. In some works, MFD was combined with UV-Vis and ICP-MS to study QDs [11].…”

“…Transmission and electron microscopy (TEM) and SEM, as well as atomic force microscopy (AFM) are also detectors of choice combined with FFF separation; they visualize sample at the NP scale and/or a set of NPs, for dimensional and/or morphological characterization [11,44,45,[49][50][51]. Imaging is possibly in addition/ confirmation of coupling with MALS [6,8,9,24,40].…”