Size analysis of large-sized gold nanoparticles using single particle ICP-mass spectrometry

Abstract

Single particle ICP-mass spectrometry (spICP-MS) has been used to define the size and number concentration of nanoparticles (NPs). In this study, we have developed a new analytical approach to extend the analytical size range of NPs toward a larger region. To achieve this, the signal intensities of Au related polyatomic ions such as ¹⁹⁷Au¹²C⁺, ¹⁹⁷Au¹⁴N⁺, ¹⁹⁷Au¹⁶O⁺, and ¹⁹⁷Au⁴⁰Ar⁺, instead of ¹⁹⁷Au⁺, were used for the size calibration of Au NPs. With the ¹⁹⁷Au⁴⁰Ar⁺ signal, the signal intensities emanating from the Au NPs can be reduced to the 10⁻⁵ level, and thus, the resulting signal intensity for 400 nm Au NPs was about 1 000 000 cps, which was well within the analytical range. For the size analysis of Au NPs of size 200–400 nm, the intensity of the ¹⁹⁷Au⁴⁰Ar⁺ signal was used, whilst, the ¹⁹⁷Au⁺ signal was used for the size calibration for Au NPs of size 10–100 nm. The reliability of the technique can be evaluated from the slope of the regression line defined by NPs of three sizes (200, 300, and 400 nm). The wider analytical range achieved here (i.e., 10–400 nm) shows that this technique can be applied for the size analysis of NPs present in nature.