Microbubble-enhanced cold plasma activation (MB-CPA) for surface functionalization of polymer nanoparticles from nanoprecipitation

Cold plasma activation has been considered as a green and effective technological approach for functionalization of solid surfaces. In the current study, we introduce a versatile technique known as microbubble-enhanced cold plasma activation (MB-CPA) for surface modification of polymer plates and nanoparticles in flowing liquid phase. Corona plasma is generated at the inlet of a venturi tube, thereby creating a highly excited state in the air. Reactive nitrogen and oxygen species (RNOS) are transferred from the gas phase to the suspension flow in the form of plasma microbubbles. Two types of polymer-based nanoparticles in the suspension, namely polymethyl methacrylate (PMMA) of 16–154 nm and polycaprolactone (PCL) of 30–225 nm, are synthesized using nano-precipitation method. Through the degradation of model compounds, the polar organic solvent, acetone and ethanol, is found to promote or suppress the production of active species. In addition, the efficiency of the MB-CPA treatment depends on the solvent composition, making this technology a controllable and efficient strategy for the surface modification of nanoparticles. The findings indicate that plasma activation effectively reduces the negative surface zeta-potentials and induces aggregation and separation in the suspensions. The infrared spectra of the treated nanoparticles reveal that plasma activation leads to the formation of N[sbnd]H and C[sbnd]N bonds situated on the surface of PMMA. Our work demonstrates that organic-solvent involved MB-CPA emerges as a promising method for the surface modification of nanoparticles in the flow condition.