Influence of Nanoparticle Properties on Non-Photochemical Laser-Induced Nucleation

In nonphotochemical laser-induced nucleation (NPLIN), an unfocused nanosecond laser pulse with low intensity (≈MW/cm2) triggers nearly instantaneous nucleation in supersaturated solutions, a process that would typically take days or weeks when the solution is left undisturbed. Previous studies have shown that the introduction of nanoparticles into supersaturated solutions enhances the probability of NPLIN measured during a fixed time window, compared to undoped control experiments. However, the precise mechanisms driving this enhancement remain unclear hampering industrial implementation of NPLIN. In this study, we systematically investigate how the properties of doped nanoparticles─specifically their concentration and chemical composition─affect the NPLIN probability in supersaturated urea solutions. We observed that higher laser intensities resulted in elevated NPLIN probabilities at a fixed pegylated gold nanoparticle (AuNP) concentration and supersaturation, while increasing concentrations of AuNPs at a fixed laser intensity and supersaturation interestingly led to higher NPLIN probabilities. Moreover, supersaturated solutions doped with gold nanoparticles exhibited significantly higher NPLIN probabilities compared to silica nanoparticle doped solutions at comparable nanoparticle size and concentration. We interpret these experimental results based on the impurity heating hypothesis as well as recent results highlighting the role of thermocavitation. We furthermore propose a helicopter-view model based on a thermodynamic equilibrium stage sequence. Our findings highlight the significance of nanoparticle properties in the design of heteronucleants optimized for NPLIN applications.