In-situ characterization of metal nanoparticles and their organic coatings using laser-vaporization aerosol mass spectrometry

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.

Characterization of a copper spark discharge plasma in argon atmosphere used for nanoparticle generation

“…By comparing the calculated values with experimentally determined intensity ratios the plasma parameters can be deduced. The measured intensity ratios of two Cu-Ar line pairs (Cu I 521.82 nm/Ar I 738.40 nm and Cu I 515.32 nm/Ar I 751.53 nm) were used to find solutions of (6)- (9). In order to find the best possible solution Saha-Boltzmann plots were constructed incorporating atomic emission lines of both argon and copper.…”

“…In order to find the best possible solution Saha-Boltzmann plots were constructed incorporating atomic emission lines of both argon and copper. This requires the modification of (4) by weighting the left side with the concentration of the given species (denoted as n) calculated from (6)- (9). It is expected that if both Saha and Boltzmann equilibrium conditions are met the points belonging to argon and copper lines lie on the same linear.…”

“…Several aspects of NP generation in spark discharges have been investigated in the literature. Most of these studies focused on the physical and chemical characterization of the produced particles [5,[8][9][10][11][12][13] and potential particle formation mechanisms [14][15][16], but only a couple of attempts have been made to describe the characteristics of the plasma in the SDG during NP generation (e.g. [17,18]).…”

Laboratory evaluation of nanoparticle penetration efficiency in a cylindrical counter flow denuder for non-specific removal of trace gases

“…Recently, aerosol mass spectrometry employing the Aerodyne aerosol mass spectrometer (AMS; Canagaratna et al 2007) has been widely used for real-time characterization of the size, chemical composition, and in situ measurement of aerosol nanoparticles without filter sampling technique, which has been used during field observation of oxygenated organic aerosol nanoparticles from secondary sources (Ahlm et al 2012). Laser-vaporization AMS has been used for the measurement of metal nanoparticles (Nilsson et al 2015). The AMS has an inlet system that comprises an aerodynamic lens for preconcentration of aerosol particles during removal of gases.…”

Characterization of trace metals on soot aerosol particles with the SP-AMS: detection and quantification

“…Cross et al (2012) and Dallmann et al (2014) used the SP-AMS to detect the relative concentrations of trace elements Ca, Zn, Mg, and P in the emissions of a laboratory-based diesel engine and onroad diesel truck engines, respectively. Nilsson et al (2015) used the SP-AMS to characterize metal nanoparticles (Ag, Au, Pd, Fe, Ni and Cu) in the aerosol phase.…”