An environmental evaluation of carbonaceous aerosols in PM10 at micro- and nano-scale levels reveals the formation of carbon nanodots

Carbonaceous aerosols play significant roles in air quality and the climate; their oxidation at the nanoscale level may possibly increase the reactivity and toxicity of atmospheric particulates. In the present study, a laboratory experiment on the atmospheric carbonaceous aerosol was done by using H2O2 as an oxidizing agent. An extensive study made with advanced analytical tools revealed the formation of photoluminescent carbon nanoparticles (carbon nanodots) in the carbonaceous aerosol. The carbon nanoparticles are mostly at the sp(2) hybridization state and contain various surface functional groups such as carboxyl and carbonyl groups. The properties of these carbon nanoparticles resemble the engineered carbon nanoparticles such as carbon dots (CDs). The carbon nanoparticles, mainly less than 10 nm, are composed of carbon nanocrystals containing a few other elements such as Ca and Fe. Fluorescence spectroscopy revealed the characteristic excitation-dependent emission spectra of blue fluorescent carbon nanoparticles. The results indicate the presence of characteristic carbon nanoparticles in the carbonaceous aerosol in PM10, opening a new road for predicting environmental processes occurring in the atmospheric environment. (C) 2019 Elsevier Ltd. All rights reserved.