Role of Kinks in Dyeing Crystals: Confocal Luminescence Microscopy from Single Molecules to Square Centimeters

Abstract

Large (1 cm3) potassium hydrogen phthalate (KAP) crystals grown in the presence of the fluorescent dye 2′,7′-dichlorofluorescein (DCF) show patterns of luminescence characteristic of selective inter- and intrasectoral zoning. Despite this selectivity, the polarization dependence of the luminescence of single DCF molecules inside the crystals indicated broad orientational distributions consistent with nonspecific mixed crystal growth mechanisms ( Wustholz K. Kahr B. Reid P. J. Wustholz K. Kahr B. Reid P. J. J. Phys. Chem. B20051091635716362). In an effort to reconcile this apparent discrepancy, KAP crystals were grown from 10−9 to 10−4 M DCF solutions and examined using confocal luminescence and polarized absorption microscopies, where possible. Single molecules and molecular ensembles were investigated. The fluorescence excitation dichroism was strongly dependent on the concentration of DCF, suggesting that different mixed crystal growth mechanisms were at work at different guest concentrations. Hottenhuis et al. (J. Cryst. Growth19861989) had earlier established that certain trivalent cations bind preferentially to distinct kink sites of KAP. By blocking particular kink sites with Fe3+ or Ce3+ at high DCF-solution concentrations, the orientation of DCF in the crystals was modulated, thus establishing that the dye not only recognizes some propagating steps as opposed to others but also preferentially chooses between kinks propagating in opposing directions on the same step, evidence that kink selectivity plays a vital role in the dyeing of crystals.

Photoluminescence Intermittency from Single Quantum Dots to Organic Molecules: Emerging Themes

“…Our group has been investigating the role of proton transfer in the PI exhibited by rhodamine-type chromophores isolated in single crystals of potassium acid phthalate (KAP) [102,109–113]. Comparative studies of violamine R (VR) emission in PVOH and KAP found that the temperature dependence of VR PI was markedly different in these two environments.…”

“…Proton transfer has not been a widely invoked hypothesis for organic luminophore PI since this process was considered to occur on a timescale significantly shorter than that typically explored in PI experiments. Our group has been investigating the role of proton transfer in the PI exhibited by rhodamine-type chromophores isolated in single crystals of potassium acid phthalate (KAP) [ 102 , 109 – 113 ]. Comparative studies of violamine R (VR) emission in PVOH and KAP found that the temperature dependence of VR PI was markedly different in these two environments.…”

Tailor‐Made Auxiliaries for Polar Growth from Melts

“…TMAs may modify the morphology of hillocks, but not the polyhedral shapes of crystals themselves. [47][48] Sometimes, more information is necessary such as the residence times [49][50][51] on surface sites relative to measured crystal growth step rates. [52][53][54][55] Given the complexity of crystal growth, some TMAs can behave like wolves in sheep's clothing.…”

Packing-induced solid-state fluorescence and thermochromic behavior of peptidic luminophores

“…Several reports have shown the inuences of packing on the uorescent colors of various synthetic organic dyes. 19,20 For example, Mei and co-workers have shown the mechanochromism triggered uorescent colour switching among polymorphs of emodin. 21 Wang et al explained the polymorphism and pseudo-polymorphism directed uores-cence switching of N,N-di(n-butyl)-quinacridone.…”