Abstract
The development of methods to produce nanoparticles with unique properties via the aerosol route is progressing rapidly. Typical characterization techniques extract particles from the synthesis process for subsequent offline analysis, which may alter the particle characteristics. In this work, we use laser-vaporization aerosol mass spectrometry (LV-AMS) with 70-eV electron ionization for real-time, in-situ nanoparticle characterization. The particle characteristics are examined for various aerosol synthesis methods, degrees of sintering, and for controlled condensation of organic material to simulate surface coating/functionalization. The LV-AMS is used to characterize several types of metal nanoparticles (Ag, Au, Pd, PdAg, Fe, Ni, and Cu). The degree of oxidation of the Fe and Ni nanoparticles is found to increase with increased sintering temperature, while the surface organic-impurity content of the metal particles decreases with increased sintering temperature. For aggregate metal particles, the organic-impurity content is found to be similar to that of a monolayer. By comparing different equivalent-diameter measurements, we demonstrate that the LV-AMS can be used in tandem with a differential mobility analyzer to determine the compactness of synthesized metal particles, both during sintering and during material addition for surface functionalization. Further, materials supplied to the particle production line downstream of the particle generators are found to reach the generators as contaminants. The capacity for such in-situ observations is important, as it facilitates rapid response to undesired behavior within the particle production process. This study demonstrates the utility of real-time, in-situ aerosol mass spectrometric measurements to characterize metal nanoparticles obtained directly from the synthesis process line, including their chemical composition, shape, and contamination, providing the potential for effective optimization of process operating parameters.
Highlights
The field of nanotechnology developed significantly during the past decade, and the current potential for the creation of materials with novel characteristics has facilitated the realization of almost unlimited numbers of nanomaterial and nanoparticle applications [1, 2]
The 107Ag isotope can be separated from the main organic ion (C8H+11), which is found at the same nominal m/z in this example. This facilitates the characterization of any non-refractory particulate matter that may exist on metal particles
We have demonstrated that the laser-vaporization aerosol mass spectrometry (LV-AMS) can be used to characterize metal nanoparticles in the aerosol phase
Summary
The field of nanotechnology developed significantly during the past decade, and the current potential for the creation of materials with novel characteristics has facilitated the realization of almost unlimited numbers of nanomaterial and nanoparticle applications [1, 2]. As a result of the growing demand for such products, there is currently a need for new production methods with increased throughput and high reliability. Aerosol production methods are attractive, as they can be performed in a continuous manner and particles with high purity and tailored morphologies can be synthesized [3]. Aerosol synthesis, methods are based on the formation of particles from a gas, liquid, or solid material. The optimal synthesis method for a given product depends on the desired characteristics of the resultant particles and the required quantity. The synthesized particles can be subjected to various degrees of post-treatment in order to alter their characteristics; methods to study the effects and performance of such particle treatments are necessary [3]
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