L‐serine polymorphism controlled by optical trapping with high‐repetition‐rate femtosecond laser pulses

Abstract

This work first demonstrates polymorph control of amino acids by optical trapping with high-repetition-rate (80 MHz) femtosecond (fs) laser pulses. A saturated aqueous solution of L-serine (L-Ser) is irradiated by laser pulses to trigger crystallization, and the polymorphism of the resultant crystals is systematically investigated as a function of laser power and polarization. Irradiating near the contact line (three-phase point) of the solution triggers L-Ser crystallization, either at the laser focus or away from the laser focus. In-situ Raman spectroscopy for all the generated crystals reveals that fs laser irradiation yields two types of L-Ser polymorphs, which are identified as monohydrate and anhydrous forms (Form 1 and Form 2, respectively). When the average laser power is constant, only leftcircular polarization produces Form 1 with a 60% probability, whereas all other polarizations, linear and right-circular polarization, produce Form 2 with 100% probability. The dynamics of this unique polymorphism depending on the handedness of the circular polarization and the mechanism behind it are discussed in terms of the trapping efficiency of the pre-nucleation (liquid-like) clusters, which depends on the differences in refractive index and the arrangement of the liquidlike clusters reflecting the given laser polarization.

New Cocrystallization Method: Non-photochemical Laser-Induced Nucleation of a Cocrystal of Caffeine–Gallic Acid in Water

“…In this paper, we will use the abbreviation NPLIN, for all the laser-induced nucleation experiments, while their putative mechanism should be different depending, for example, on the laser type. According to this definition, all these published works correspond to almost 100 papers, up to now 18 . NPLIN has been applied to small organic species 1,19 as well as proteins 3,19 or inorganic compounds 20,21 .…”

“…According to this definition, all these published studies correspond to almost 100 papers, up to now. 18 NPLIN has been applied to small organic species 1,19 and proteins 3,19 or inorganic compounds. 20,21 Primary nucleation is stochastic by nature, so in general, it is not possible to control the time, location, and morphology of the new phase crystallizing.…”

“…Alexander and Camp limit the use of the NPLIN terms to the nucleation of supersaturated solutions or supercooled melts using unfocused millijoule nanosecond laser pulses. Sugiyama and Wang in a very recent paper have compiled all the experiments included in the Clair et al definition under the term laser-induced nucleation. In this paper, we will use the abbreviation NPLIN, for all the laser-induced nucleation experiments, while their putative mechanism should be different depending, for example, on the laser type.…”

“…In this paper, we will use the abbreviation NPLIN, for all the laser-induced nucleation experiments, while their putative mechanism should be different depending, for example, on the laser type. According to this definition, all these published studies correspond to almost 100 papers, up to now . NPLIN has been applied to small organic species , and proteins , or inorganic compounds. , Primary nucleation is stochastic by nature, so in general, it is not possible to control the time, location, and morphology of the new phase crystallizing.…”