Tailoring water freezing kinetics with nanobubbles: A gas-dependent modulatory effect on water solidification

The experimental results revealed that NBs do indeed alter the completion time of water solidification. Specifically, air NBs delayed solidification by up to 8.7 ± 1.9 %, while CO₂ NBs accelerated it by up to 11.4 ± 2.5 % at an ambient temperature of -20 °C. This alteration can be explained by numerous OH^- ions and the Hofmeister-like behaviour of CO₃^2-. The numerical simulations corroborated these findings, showing that the observed changes in solidification time are comparable to an increase of +8 ± 2 % in the overall apparent energy released for air NBs and a decrease of -10 ± 2 % for CO₂ NBs. These findings suggest that NBs, depending on the gas species, offer a promising "green" nanomaterial for controlling water freezing and anti-freezing processes.