Journal ArticleDOI
Nonphotochemical, Polarization-Dependent, Laser-Induced Nucleation in Supersaturated Aqueous Urea Solutions
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In this article, it was shown that 1.06 mm pulses from a Q-switched Nd:YAG laser induce crystallization in supersaturated solutions of urea in water.Abstract:
We report a new photophysical phenomenon in which 1.06 mm pulses from a Q-switched Nd:YAG laser induce crystallization in supersaturated solutions of urea in water. Because the solutions are transparent at the incident wavelength, a photochemical mechanism is unlikely. The needle-shaped crystals that initially form tend to be aligned parallel to the electric field vector of the light, suggesting a Kerr-like field-induced alignment of urea molecules that aids in organizing prenucleating clusters. The effect has application to pump-probe nucleation studies and to clean nucleation in sealed systems. [S0031-9007(96)01456-1] PACS numbers: 81.10.Dn, 42.50.Vk The study of the light-induced condensation of supersaturated vapors dates back to the work of Tyndall in 1869 [1]. More recent interest has centered on the formation of atmospheric aerosols [2], laser-induced chemical vapor deposition [3], and laser-induced clustering in atomic and molecular systems [4]. The mechanism typically involves the photochemical generation of a nonvolatile product that acts as a nucleus for the growth of the condensed phase [5]. Nucleation in liquid solutions is a more complex problem involving two components, and, to our knowledge, there have been no reports of light-induced nucleation from supersaturated solutions. Nevertheless, this problem is of great theoretical and commercial importance, such as in industrial crystallization processes [6]. Recently, while attempting to observe second harmonic generation in supersaturated solutions of urea in water, we have noticed that pulses from a Q-switched Nd:YAG laser can induce nucleation in such solutions. Because the incident light source is near infrared, a photochemical mechanism is unlikely. The orientation of the crystallites that are formed depends on the plane of polarization of the incident radiation, suggesting an electric-field-induced effect. Aqueous urea solutions, with concentrations, c, in the range of 11.5 -13.5M, were prepared by combining solid urea and water in a 1.3-cm diameter pyrex test tube, which was then heat sealed with a torch. Great care was taken to exclude dust from samples. Supersaturated solutions were generated and regenerated by heating the tubes to 45 ‐ C and holding them at that temperature forread more
Citations
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Journal ArticleDOI
High-throughput crystallization: polymorphs, salts, co-crystals and solvates of pharmaceutical solids
Sherry L. Morissette,Orn Almarsson,Matthew Peterson,Julius F. Remenar,Michael Read,Anthony V. Lemmo,Steve Ellis,Michael J. Cima,Colin R. Gardner +8 more
TL;DR: The impact of form diversity encompasses issues of stability and bioavailability, as well as development considerations such as process definition, formulation design, patent protection and regulatory control.
Journal ArticleDOI
General principles of pharmaceutical solid polymorphism: a supramolecular perspective.
Barbara Rodríguez-Spong,Christopher P. Price,Adivaraha Jayasankar,Adam J. Matzger,Naír Rodríguez-Hornedo +4 more
TL;DR: Current understanding of pharmaceutical solids in terms of molecular recognition and complementarity provides new insights into the design and function of single and fully miscible, multiple-component solids with varying degrees of order, and in this way is leading the path to supramolecular pharmaceutics.
Journal ArticleDOI
Polymorph control: past, present and future.
TL;DR: There is a large armoury of methods that can be used to tackle the appearance and disappearance of polymorphs, and the methods and their successes over the last few years are surveyed.
Journal ArticleDOI
The non-classical nucleation of crystals: microscopic mechanisms and applications to molecular crystals, ice and calcium carbonate
TL;DR: In this paper, a review of experiments and simulations that find nucleation behaviour that cannot be described by the classical theory of nucleation is presented. But the authors focus on the first step in crystallization and do not discuss the evolution of the nucleation process.
Journal ArticleDOI
A practical guide to pharmaceutical polymorph screening & selection
TL;DR: This review introduces the basic concepts of polymorphism, addresses a fundamental question of “Why do polymorphs form?”, and provides practical guidelines of how to prepare polymorphs and how to evaluate the relative thermodynamic stability between polymorphs.
References
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Book
Nonlinear optical properties of organic molecules and crystals
Daniel S. Chemla,Joseph Zyss +1 more
Book
Handbook of nonlinear optical crystals
TL;DR: In this article, the authors provide a complete description of the properties and applications of all non-linear crystals reported in the literature up to the beginning of 1990, including the most important equations for calculating parameters of nonlinear frequency converters.
Journal ArticleDOI
Isotonic Solutions. I. The Chemical Potential of Water in Aqueous Solutions of Sodium Chloride, Potassium Chloride, Sulfuric Acid, Sucrose, Urea and Glycerol at 25°1
Journal ArticleDOI
Prediction of Crystal-Growth Morphology Based on Structural-Analysis of the Solid-Fluid Interface
TL;DR: In this article, a theoretical approach was proposed to predict needle-like shape of growing urea crystals from aqueous solution, which is consistent with experimental observations. But this approach was only applied to the case of urea crystal grown from urea.