Supramolecular structure of TTBC J-aggregates in solution and on surface

Hans v Berlepsch, Christoph Böttcher
Langmuir: the ACS Journal of Surfaces and Colloids 2013 April 23, 29 (16): 4948-58
The aggregation behavior of cationic 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidacarbocyanine with chloride (TTBC-Cl) or iodide counterions (TTBC-I) in aqueous solution is investigated by absorption, linear dichroism, and fluorescence spectroscopies, as well as cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM). TTBC-Cl is found to form J-aggregates with a classical Davydov-split absorption band (type I spectrum) even under different preparation conditions. These aggregates remain stable for months. Unlike the chloride salt, the iodide salt TTBC-I forms two different types of J-aggregates depending on the pH of the aqueous solution. The TTBC-I aggregates prepared in pure water (pH = 6) are characterized by a single redshifted absorption band (type III spectrum), whereas those prepared in alkaline solution at pH = 13 show a typical Davydov-split (type I) absorption band. Despite differences in counterions, preparation method, stability, and spectroscopic behavior, cryo-TEM reveals an identical tubular architecture for all these J-aggregates. Among the new structure models discussed here is a cylindrical brickwork layer of dye molecules for single-banded J-aggregates (type III). For Davydov-split aggregates (type I), a molecular herringbone-like pattern is proposed instead. Moreover, absorption spectra have revealed an additional single redshifted absorption band (type II spectrum) that is assigned to a surface aggregate and is induced by a specific interaction of the dye cation with the negatively charged cuvette wall. AFM measurements of analogous preparations on negatively charged mica surfaces have supported this interpretation and revealed the formation of monolayered sheet structures.

Full Text Links

Find Full Text Links for this Article


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read

Save your favorite articles in one place with a free QxMD account.


Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"