Plasmonic Heating-Assisted Laser-Induced Crystallization from a NaClO₃ Unsaturated Mother Solution

We provide a novel laser-induced crystallization mechanism which explains crystallization induced by visible laser trapping of silver nanoparticles (AgNPs) at the air/unsaturated mother solution interface from the focal spot [Niinomi et al.CrystEngComm 2016, 18, 7441–7448]. Simultaneous in situ microscopic observation of Raman scattering and polarized-light image revealed that the optical trapping of nanoparticles that exhibit surface-enhanced Raman scattering (SERS) triggers the crystallization, showing the excitation of localized surface plasmon resonance (LSPR) significantly promotes the crystallization. Numerical analysis of temperature distribution based on the combination of finite-difference time-domain electromagnetic and finite-difference heat transfer calculations shows that temperature reaches 390 °C at the focal spot because of plasmonic heating, the energy dissipation of the plasmon-enhanced electromagnetic field as heat. A conceivable mechanism of the crystallization is local increment of supersaturation caused by local solvent evaporation via the Plasmonic heating. This plasmonic heating assisted laser-induced nucleation process has the possibility to provide not only a novel approach for spatiotemporal control of crystallization but also a novel nucleation field based on nonlinear light–matter interaction originating from the plasmon-enhanced electromagnetic near field through heterogeneous nucleation on the surface of plasmonic particles.