Facile synthesis of model polystyrene nanoparticles for nanoplastics research.

This study presents a simple and inexpensive surfactant-free method for the synthesis of polystyrene (PS) nanoparticles that are suitable for use as model nanoplastics in environmental research. PS nanoparticles were prepared using a two-step process: polystyrene was dissolved in acetone and rapidly injected into heated deionised water (the Ouzo effect). An injection rate of 1 mL of the PS solution per 1.7 s led to the formation of the smallest nanoparticles with the average size of 40 nm. The temporal stability of the resulting nanosuspensions was also investigated. The average hydrodynamic sizes of the PS nanoparticles ranged from 40 to 44 nm over the period from 1 h to 265 d, and the corresponding zeta potentials ranged from -19.6 to -22.8 mV. The PS nanoparticles prepared using this procedure are free of stabilisers, easily reproducible, and scalable, making them a suitable reference material for further studies on the behaviour of nanoplastics.•PS nanoprecipitation is driven by solvent polarity change.•Ouzo-effect-induces nucleation and growth of nanoparticles tuneable by injection speed.•Stabiliser-free, reproducible, and stable nanoplastic particles were obtained.