Carbon nanoparticle aggregates on films produced via electric field-assisted flame synthesis

The flame synthesis of carbon nanoparticle (CNP) films is a promising approach for fabricating advanced nanomaterials. This study investigates the compositional and optical properties of CNPs collected using electric field-assisted thermophoretic deposition in a laminar premixed ethylene-air flame. CNPs were sampled on substrates at varying electric potentials (0 kV,-2 kV,-3 kV) and subsequently characterized to assess the influence of the electric field on their features. CNPs were dissolved in N-methyl-pyrrolidone to obtain stable suspensions of primary aggregates to be analyzed via UV-Visible absorption, fluorescence spectroscopy, and size exclusion chromatography. Results indicate that the application of an electric field alters the size distribution of the CNPs, promoting the formation of aggregates with lower optical band gaps while the fraction of smaller CNPs (<20 nm) diminished. The in-depth analysis allows a comprehensive understanding of the size-dependent effects of electric fields on flame-formed CNPs. It was shown that the electric field not only enhances the deposition rate as reported in previous works but also impacts the compositional, optical and structural properties of the resulting films, favouring smaller particles aggregation and influencing the morphology of the primary aggregates with promising implications for applications requiring conductive and/or optically active carbon materials.