雷射捕陷控制重水中L-苯丙胺酸之假多晶現象

Abstract

我們成功呈現出雷射捕陷控制重水中L-苯丙胺酸之假多晶現象，連續波長1064奈米雷射光聚焦在空氣和溶液間的介面，即使是在未飽和溶液中照射30分鐘之內，仍可產生針狀或片狀結晶。FT-IR測量顯示出生成的結晶分別屬於單水合和無水結晶，我們觀察到只有在焦點內會產生無水結晶，而在距離焦點幾百微米到一毫米間則產生單水合結晶。我們調控雷射強度和雷射極性影響假多晶現象，雷射捕陷在過飽和溶液和未飽和溶液中分別產生單水合和無水結晶;照射線性偏振雷射和圓性偏振雷射在飽和溶液中分別導致偏向單水合和無水結晶，我們從高濃度類液體叢集區域的觀點和此區域的成長與在焦點內高濃度叢集區域的增加，探討這獨特的雷射捕陷控制L-苯丙胺酸的假多晶現象。

We present laser trapping-controlled crystal pseudopolymorphism of L-phenylalanine in D2O. Upon focusing a continuous-wave 1064 nm-laser beam at an air/solution interface of the solution thin-film, either a whisker-like or a plate-like crystal is provided within 30 minutes of the irradiation even in unsaturated solution. FT-IR measurement reveals that the formed crystals are identified to monohydrate and anhydrous forms, respectively. Interestingly, only one anhydrous crystal is always formed at the focus, while a number of the monohydrate crystals are observed at an area ranging from a few hundred micrometers to a millimeter away from the focus. For its pseudopolymorphism depending on laser power and polarization, laser trapping in supersaturated and unsaturated solutions always provides the monohydrate and anhydrous crystals, respectively. On the other hand, in saturated solution, linearly- and circularly-polarized laser irradiation preferentially lead to monohydrate and anhydrous crystal formation, respectively. We discuss the dynamics and mechanism of this unique laser trapping-controlled pseudopolymorphism of L-phenylalanine from the viewpoints of a highly concentrated domain formation of the liquid-like clusters, the domain growth, and concentration increase at the focus of the domain.