Ångström‐Sensitive Imaging Nephelometry for Real‐Time Characterization of Secondary Aerosols in Non‐Thermal Plasma VOC Degradation

ABSTRACT Secondary aerosol formation during non‐thermal plasma (NTP) degradation of volatile organic compounds (VOCs) complicates mechanistic interpretation and compromises reactor stability. Here, an imaging nephelometer was developed for in situ, real‐time characterization of plasma‐generated secondary aerosols. Stray light suppression through optical trapping and chamber expansion enabled sub‐nanometer sensitivity, validated by agreement between measured and theoretical Rayleigh scattering phase functions of N 2 . Using toluene degradation in a dielectric barrier discharge (DBD) reactor as model system, the effects of reaction operation conditions were systematically investigated. Aerosol mode diameters (40–100 nm) decreased with increasing discharge power and residence time, but increased with higher initial toluene concentration. This diagnostic approach provides a direct evaluation of aerosol evolution and supports mitigation of plasma‐induced fouling and catalyst deactivation.