Electrical interactions dominate this cooling interface.
A TiO₂ particle cools rapidly in water—until electrostatic interactions are removed from the model. That comparison reveals a much larger effect than the changes caused by particle size or surface wettability.
Journal of Molecular Liquids · 2022 · M Roodbari, M Abbasi, S Arabha, A Gharedaghi, A Rajabpour
The boundary is part of the heat-transfer problem
A nanoparticle can transfer heat only as fast as energy crosses its boundary into the surrounding liquid. At that scale, particle size and the strength of contact with water can both change the cooling response.
Which particle and surface conditions most strongly control heat transfer across a TiO₂–water interface?
Watching a heated particle relax
Transient non-equilibrium molecular dynamics measured interfacial conductance while the authors varied TiO₂ particle diameter, initial particle temperature, and the Lennard–Jones interaction strength that represents surface wettability. The molecular results were also compared with a continuum cooling description.
Transient non-equilibrium molecular dynamics heats the TiO₂ particle and follows its relaxation into water. An energy-versus-integrated-temperature-difference fit gives the interface conductance. Size comparisons span 4–9 nm and average five simulation results; temperature and wettability are varied separately. The electrostatic comparison uses a 6 nm particle. It is a comparison of interaction models, and removing electrostatics also changes interfacial water structure.
Key findings
Dominant interaction
Removing Coulomb interactions drops the modeled conductance by almost two orders of magnitude for the 6 nm TiO₂ particle.
Geometry and cooling
Across 4–9 nm, conductance per unit interface area decreases modestly while the total relaxation takes longer.
Contact and vibrations
Temperature and wettability produce smaller tuning effects, supported by the interfacial vibrational spectra.
Model the contact as carefully as the particle
The interface itself is an important design variable: warmer particles and stronger particle–water coupling improve heat exchange in these simulations.
The simulations connect an interface-scale property to the particle’s cooling transient. They show why surface coupling and the representation of electrical interactions deserve attention when predicting heat release into water.