The nucleation of glycine from aqueous supersaturated solution has been studied using non-photochemical laser-induced nucleation (NPLIN), ultrasound (sonocrystallization), and mechanical shock of sample vials. It was found that at higher supersaturation, samples were more susceptible to nucleation and produced more of the γ-glycine polymorph. The results are described in terms of a mechanism common to all three nucleation methods, involving the induction of cavitation events and pressure shockwaves. The switch in preference from α- to γ-glycine was observed to occur over a narrower range of supersaturation values for NPLIN. We attribute this to induction of cavitation events with higher energies, which result in higher localized pressures and supersaturations. Experiments on NPLIN using circularly versus linearly polarized light showed no evidence for binary polarization switching control of glycine polymorphism.

A Z-scheme system In ₂ S ₃ /WO ₃ heterojunction was fabricated via a mild hydrothermal method and further applied for photocatalytic degradation of tetracycline (TCH) and Rhodamine B (Rh B) under visible light irradiation.

In a seminal report on laser-induced nucleation in aqueous supersaturated solutions (Phys. Rev. Lett., 1996, 77, 3475) it was noted that needle-shaped crystals of urea were aligned with the direction of the electric field of the linearly polarized laser pulse. The results gave rise to a new mechanism for control of crystal nucleation involving alignment of solute molecules (optical Kerr effect) now commonly known as non-photochemical laser-induced nucleation (NPLIN). Recent theoretical and experimental work has cast doubts on the optical Kerr effect mechanism. In the present letter we present results from digital imaging of urea-crystal growth immediately following laser-induced nucleation. Analysis of the data shows no statistically significant correlation between crystal angle and direction of linear polarization. The results overturn a long-held result that has shaped theoretical and experimental studies of NPLIN.

An approach to controlling morphology and size is presented through the combination of laser-induced nucleation and polymer additives. Here, we apply the technique of non-photochemical laser-induced nucleation to irradiate a supersaturated solution (S = 1.15) of cesium chloride (CsCl). The solution immediately responds to laser exposure, and spherical crystallites are produced along the laser pathway. The crystals gradually grow into snowflake-like crystals with different sizes. In this report, two types of acidic polymers including polyepoxysuccinic acid (PESA) and polyaspartic acid (PASA) were individually added in supersaturated CsCl solution to shape its crystalline morphology; we found that a particular property of this control from PESA is uniformity in modification of crystal sizes. Additionally, we observed that both PESA and PASA were able to decrease crystal growth velocity and the quantity of crystals after laser irradiation. With the effect of more than 0.2 wt % PESA in solution, spherical crystallites were initially induced by laser; after that, crystal growth velocities and sizes became slower and smaller with increase in mass fraction of PESA, which led to identical crystal sizes. With the effect of more than 5 wt % PESA, the resulting crystalline morphology obtained by laser was flower-like crystals, whilst cuboid-shaped crystals could be obtained by spontaneous nucleation. Classical nucleation theory, crystal growth rate, and additives as large-size impurities were discussed to analyze the underlying mechanism of the change in morphology.

The mechanism of non-photochemical laser-induced nucleation (NPLIN) was investigated through the crystallization of urea crystals in supersaturated (151%) aqueous solutions. To detect the role of impurities in NPLIN, the effect of filtration, doping and laser irradiation position on nucleation probability were studied, respectively. As particles larger than the filter pore size in the solution were almost removed by syringe filter with poly (ether sulfone) membrane, the NPLIN probability was evidently suppressed by filtration when the pore sizes of filter were used from 1 μm to 0.45 μm. The inhibition of NPLIN after filtration could be reversed to varying degrees by adding several kinds and concentrations of impurities into the filtered solution; as the solid particles were extra added, age after cooling for samples was no longer necessary. The increase in the NPLIN probability with the irradiation height decreases was observed when samples were irradiated at different vertical positions within the sample vial. The experimental results were analyzed with reference to the known mechanisms. As nucleation probability through NPLIN can be controlled by pore size of syringe filter, doping or laser irradiation position, several functions were established to analyze the nucleation probability distribution under the effect of these three factors. These experimental results were discussed with reference to the known mechanisms proposed for NPLIN.