Component and morphology biases on quantifying the composition of nanoparticles using single-particle mass spectrometry

Considerable effort has been expended to develop the real-time single-particle mass spectrometry using the laser ablation/ionization technique. With a complete ionization technique, quantitative information about particle size and elemental stoichiometry for a single component particle can be obtained. However, it is more complex to deal with multi-component composite particles. The morphology and the composition of particles will change the thermal and optical properties of the particle and thus the laser-particle interaction. In this paper, multi-component particles of different morphologies are generated and used to examine the limitations of the complete ionization approach. The experimental results show that there are component and morphology biases, which can be related to the high non-linear properties of the laser-particle interaction. The relative laser absorbtivity of each component is found to have a significant impact on the particle heating and ion formation process. In addition, the ion distribution formed from the laser-particle interaction is in part a result of charge transfer, and electron-ion recombination. A qualitative explanation for the observed behavior is developed, which involves the characteristic time for laser heating and intraparticle heat conduction.