Optimized Substrates for Single-Particle Analysis with Multiple Microscopy and Spectroscopy Techniques

KATHERINE KOLOZSVARI, Emily Costa, Holly Lawson, Andrew P. Ault, University of Michigan

     Abstract Number: 402
     Working Group: Instrumentation and Methods

Abstract
Heterogeneity within the atmospheric aerosol is a key factor which adds to uncertainties in the global impact of aerosols on climate and health. There are many analytical techniques capable of offline single-particle analysis, and multiple complementary techniques are often used to determine the elemental composition, functional group information, morphology, and phase state of atmospheric particles. However, as each technique has different requirements for analysis, using multiple methods often requires samples to be collected onto multiple different substrates. This means that limited information can be collected from each individual particle, and cross comparison is limited to the population as opposed to the single-particle level. This is especially relevant for field samples, which often have high particle-to-particle heterogeneity, and also are unique snapshots of a specific time and place and therefore cannot be replicated. Herein, we present the fabrication of a gridded Ni-coated Si substrate with no background interferences for Raman microspectroscopy, photothermal infrared (PTIR) spectroscopy, and atomic force microscopy (AFM). For scanning electron microscopy coupled to energy dispersive x-ray (SEM-EDX) spectroscopy, the atmospherically-relevant background interference is minimal, and the overall background signal is lower in intensity than for Si substrates. The alphanumeric gridded pattern allows the location of the same particle across multiple analytical techniques. This enables a comprehensive insight into the identity of a single particle, allowing for the disambiguation of broad particle categories such as “carbon-containing,” as well as allowing for in-depth study of particle types of interest collected during field research.