Surface-Directed Adsorption in the Epitaxy Growth of Streptocyanine Dye Crystals

Abstract

The simple molecular structure, relatively high stability, and color variation with molecular packing structure make the streptopolymethine dyes an ideal candidate for the study of surface effects on the nucleation and growth of organic crystals at a liquid/solid interface. In situ optical and atomic force microscopy (AFM) experiments were conducted on amorphous glass and crystalline muscovite mica in order to correlate the crystal morphology and orientation with early molecular events during adsorption and nucleation. Bulk crystallization of the chloride salt of 1,7-bis(dimethylamino)heptamethinium (BDH + Cl -) in acetone yields prismatic crystals bound by the (001) and (110) faces. Optical study shows that, of all the substrates studied, mica has the highest selectivity toward the (001) face. The orientation of this face follows the 3-fold symmetry of the mica lattice. AFM measurements captured the early stages of BDH + Cl -dye crystallization on mica, such as the adsorption of single molecules, formation of rodlike aggregates, their organization into twodimensional brickwork aggregates/crystals, and three-dimensional crystal growth. For all stages, the dye molecules were oriented edge-on along the [100] direction of the mica, yielding the (001) BDH + Cl -crystal face. It is concluded that BDH + Cl -crystallizes epitaxially on mica despite the poor match in lattice symmetry and parameters. This is realized by the weak interlayer and strong intralayer interactions and the surfacedirected alignment of adsorbed BDH + molecules.

Dye Sensitization of Four Low Index TiO2 Single Crystal Photoelectrodes with a Series of Dicarboxylated Cyanine Dyes

“…The IPCE absorptance spectra in Figures and were simulated using a linear sum of the dicarboxylated cyanine dye monomer and H-aggregate absorbance spectra calculated in Figure b and d. Interestingly, in no case were J-aggregates observed in the IPCE spectra despite the well-known tendency for cyanine dyes to form J-aggregates. ,− The spectral fitting was in good agreement with the IPCE spectra for B4 (SI Figure S1), and G15 (SI Figure S2) dyes, however the spectral agreement was of lower quality for the B1 dye (Figure ). The B1 dye is unique among the four dicarboxylated cyanine dyes studied; the additional methylene spacer on the carboxylated appendage may afford the B1 dye more flexibility to bind to the TiO 2 surface.…”

Dye Sensitization of the Anatase (101) Crystal Surface by a Series of Dicarboxylated Thiacyanine Dyes

“…Many studies of noncovalently bound cyanine dyes on surfaces have shown red-shifted or J-aggregation. 16,[25][26][27][28] The observation of a blue-shifted or H-aggregate type is less well-reported, although at high concentrations in solution these and similar dyes exhibit H-dimerization. 24 The "isotherm" for G7 illustrated in Figure 4b shows the contributions of dye monomers, dimers, and total adsorbed dye obtained from the fitting of the photocurrent spectrum at the various surface coverages.…”

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

“…the hydrophobic or van der Waals interactions between the aliphatic carbon chains or aromatic rings. As was demonstrated impressively by Daehne et al, aggregation also occurs for pure dialkylamino-polymethine chains [33,34]. For most of the dyes forming J-aggregates in aqueous solutions, the morphology and structure of the aggregates are unknown.…”