Polarization independence of laser-induced nucleation in supersaturated aqueous urea solutions

Liu, Yao; Ward, Martin R.; Alexander, Andrew J.

doi:10.1039/c6cp07997k

Cited by 19 publications

(34 citation statements)

References 24 publications

(39 reference statements)

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“…Theoretical considerations suggest that thermal fluctuations should overwhelm molecular alignment by the optical electric field. 37,38 Recent work on NPLIN of urea shows no correlation between the direction of polarization of the light and the direction of the initial crystallite needles, 39 contrary to the original report. 40 Polarization switching of glycine polymorphs by NPLIN has so-far not been reproduced.…”

contrasting

confidence: 46%

Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock

Liu

Berg

Alexander

2017

Phys. Chem. Chem. Phys.

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The nucleation of glycine from aqueous supersaturated solution has been studied using nonphotochemical 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 g-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 a-to g-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.

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confidence: 46%

Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock

Liu

Berg

Alexander

2017

Phys. Chem. Chem. Phys.

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“…These methods include the application of Cr(VI) reduction via the use of chemical reductants as well as photocatalytic routes. Both the methodologies have advantages and disadvantages in the reduction process . Moreover, our reported bimetallic CuPd alloy NPs showed intriguing catalytic activity in both reduction reactions e. g. reduction of 4‐NP and toxic Cr(VI) compared to the monometallic counterparts .…”

Section: Cu−m (M=pd Ag Pt Au) Nanoparticle Catalystsmentioning

confidence: 90%

Cu‐Based Nanoparticles as Emerging Environmental Catalysts

Deka

Borah

Saikia

et al. 2018

The Chemical Record

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This account provides an overview of current research activities on nanoparticles containing the earth-abundant and inexpensive element copper (Cu) and Cu-based nanoparticles, especially in the field of environmental catalysis. The different synthetic strategies with possible modification of the chemical/ physical properties of these nanoparticles using such strategies and/or conditions to improve catalytic activity are presented. The design and development of support and/or bimetallic systems (e. g., alloys, intermetallic, etc.) are also included. Herein, we report synthetic approaches of Cu and Cu-based nanoparticles (monometallic copper, bimetallic copper and copper (II) oxide nanoparticles/nanostructures) and impregnation of such nanoparticles onto support material (e. g., Co O nanostructure), along with their applications as environmental catalyst for various oxidation and reduction reactions. Finally, this account provides necessary advances and perspectives of Cu-based nanoparticles in the environmental catalysis.

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“…Laser-induced crystal-nucleation experiments in the past have been carried out on metastable (super-saturated) solutions. 2,3,9,22,23 In order to demonstrate that laser-induced nucleation can be caused by a laser-tweezing effect, we attempted to carry out experiments in the metastable region between the binodal and spinodal in the liquid-liquid phase-separation diagram. Unfortunately, because this metastable region is very narrow, such experiments proved very difficult due to the spontaneous nucleation of phase separation complicated by heating and Marangoni effects.…”

Section: Resultsmentioning

confidence: 99%

Control over phase separation and nucleation using a laser-tweezing potential

Walton

Wynne

2018

Nature Chem

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Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallisation engineering by varying physicochemical parameters, controlling which polymorph crystallises or whether a molecule crystallises or forms an amorphous precipitate is still a black art. Although there are now numerous examples of control using laserinduced nucleation, a physical understanding is absent and preventing progress. Here we show that the proximity of a liquid-liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation through a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.The nucleation of new phases such as crystals from solution is of enormous technological importance but poorly understood. Although the vast majority of pharmaceutical products and most fine and speciality chemical products are made in crystalline form, industrial crystallisation has changed little in the past 350 years and suffers from an embarrassing lack of control with sometimes unexpected and severe financial consequences.1 Therefore, a deeper understanding of and control over (crystal) nucleation is of great importance.Two decades ago, it was shown that nanosecond pulsed lasers can nucleate crystals in a supersaturated solution through a non-photochemical process.2 Most significantly, it was shown that the crystal polymorph could be selected by the polarisation state of the laser.3 Subsequent work has shown that laser pulses can induce nucleation of various crystals, 4,5 liquid crystals, 6,7 and bubbles. 8 It was initially suggested that the Kerr effect was responsible for laser-induced nucleation 2 but subsequent work has shown that the data are inconsistent with it. 9 Most disconcertingly, the reproducibility of polarisation-control over polymorph selection has been questioned while pulsedlaser induced nucleation appears to require impurity particles.10 However, a laser-induced nucleation experiment using CW lasers did reliably show polarisation-control over polymorph selection.11 Thus, it is fair to say that a physical understanding of these phenomena is still sorely lacking.In a supersaturated solution, the crystal is the thermodynamically most stable state but is difficult to access in the absence of heterogeneous nucleation sites. In the simplest case, random fluctuations lead to the formation of a critical nucleus and ultimately a macroscopic crystal. As suggested by Frenkel for proteins 12 and more generally in non-classical nucleation theories, 13-15 the concentration fluctuations leading to nucleation may well be enhanced by...

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Polarization independence of laser-induced nucleation in supersaturated aqueous urea solutions

Cited by 19 publications

References 24 publications

Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock

Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock

Cu‐Based Nanoparticles as Emerging Environmental Catalysts

Control over phase separation and nucleation using a laser-tweezing potential

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