Aqueous-based synthesis is one of the most popular methods to prepare nanoparticles. In these procedures, surfactants are needed to regulate the growth and final particle size. While there are numerous evidence on the decisive role of surfactants, a quantitative description remains elusive. This study develops a theoretical model to correlate the surfactant activities to particle growth. In the model, the "penetrability" of ions within surfactant layer is used to combine surface reaction and adsorption/desorption processes. The penetrability was then directly correlated to surfactant size. The theory was verified by synthesis of iron oxide nanoparticles with series of cationic surfactants. Eight surfactants, with same headgroup and increasing hydrocarbon tail, were employed. The experimental data showed a deterministic correlation between surfactant tails and particle size. The experimental correlation between surfactant length and particle size was predicted by the model. The modeling results verify the role of surfactant as capping agent during particle growth. More importantly, it provides a theoretical framework to control particle size in wet synthesis.

Non-thermal catalytic plasma has unfolded novel routes for a circular economy, providing a powerful cost-effective alternative to produce valued-added fuels from plastic waste. In this work, non-thermal plasma-assisted deconstruction of high-density polyethylene (HDPE) over a ZSM-5 catalyst with different morphologies, i.e., microspheres and nanoparticles, is reported. Deconstruction of HDPE over thermal routes is presented to benchmark the plasma pathways. Experimental data revealed that the highest yield/selectivity toward hydrogen and light hydrocarbons such as methane, ethylene, acetylene, and ethane was obtained through the plasma route over the hollow ZSM-5 microspheres. The spherical morphology helps in securing better stability compared to that of the ZSM-5 nanoparticles. We observed the demarcation of two different regimes resulting from the products formed. In the plasma regime (low plasma power), the ethylene monomer is prevalent while hydrogen is dominant when employing high plasma power (endothermic zone). These findings provide a novel insight into the chemical upcycling of HDPE to value-added products to potentially help address the current global plastic contamination in an efficient and sustainable way.