Crystals in Light

Abstract

We have made images of crystals illuminated with polarized light for almost two decades. Early on, we abandoned photosensitive chemicals in favor of digital electrophotometry with all of the attendant advantages of quantitative intensity data. Accurate intensities are a boon because they can be used to analytically discriminate small effects in the presence of larger ones. The change in the form of our data followed camera technology that transformed picture taking the world over. Ironically, exposures in early photographs were presumed to correlate simply with light intensity, raising the hope that photography would replace sensorial interpretation with mechanical objectivity and supplant the art of visual photometry. This was only true in part. Quantitative imaging accurate enough to render the separation of crystalloptical quantities had to await the invention of the solid-state camera. Many pioneers in crystal optics were also major figures in the early history of photography. We draw out the union of optical crystallography and photography because the tree that connects the inventors of photography is a structure unmatched for organizing our work during the past 20 years, not to mention that silver halide crystallites used in chemical photography are among the most consequential "crystals in light", underscoring our title. We emphasize crystals that have acquired optical properties such as linear birefringence, linear dichroism, circular birefringence, and circular dichroism, during growth from solution. Other crystalloptical effects were discovered that are unique to curiously dissymmetric crystals containing embedded oscillators. In the aggregate, dyed crystals constitute a generalization of single crystal matrix isolation. Simple crystals provided kinetic stability to include guests such as proteins or molecules in excited states. Molecular lifetimes were extended for the preparation of laser gain media and for the study of the photodynamics of single molecules. Luminophores were used as guests in crystals to reveal aspects of growth mechanisms by labeling surface structures such as steps and kinks. New methods were adopted for measuring and imaging the optical rotatory power of crystals. Chiroptical anisotropies can now be compared with the results of quantum chemical calculations that have emerged in the past 10 years. The rapid determination of the optical rotation and circular dichroism tensors of molecules in crystals, and the interpretation of these anisotropies, remains a subject of future research. Polycrystalline patterns that form far from equilibrium challenged the quantitative interpretation of micrographs when heterogeneities along the optical path and obliquely angled interfaces played large roles. Resulting "artifacts" were nevertheless incisive probes of polycrystalline texture and mesoscale chemistry in simple substances grown far from equilibrium or in biopathological crystals such as Alzheimer's amyloid plaques.

Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review

“…Some advanced optical microscopes, such as Polscope [16,17] and Mueller matrix microscope [18,19], can separate the birefringent retardation and the orientation of the slow optical axis. Polscope results of a poly(R-3-hydroxyvalerate) (PHV) banded spherulite containing an eye-like region are revealed in Figure 4 [17].…”

Bernauer′s Bands

“…[7][8][9] Atomic force and electron microscopies revealed PA did not grow by helical twisting. Rhythmic precipitation was a major feature of the concentric bands in PA.…”

GFP Facilitates Native Purification of Recombinant Perlucin Derivatives and Delays the Precipitation of Calcium Carbonate

“…Various crystals tend to incorporate small chemical dyes [24], [25], and also GFP incorporates into alpha-lactose monohydrate crystals in vitro [26], [27]. In a recent report, histidine-tagged GFP co-precipitated with a metastable vaterite phase and the fluorescent organic matrix became subsequently insoluble while the calcium carbonate dissolved.…”