Formation of Highly Oriented Domains of a Thiacarbocyanine Dye in a Monolayer at the Air−Water Interface

Abstract

Polarized fluorescence microscopy was used to investigate the organization of domains of J-aggregates formed upon adsorption of the thiacarbocyanine dye THIATS (3,3‘-disulfopropyl-5,5‘-dichloro-9-ethyl-thiacarbocyanine) onto a Langmuir film of the oppositely charged amphiphile dioctadecyldimethylammonium bromide at the air−water interface. When combined with the measurement of the spectral properties of this film at the air−water interface, it was possible to propose a model for the orientation and packing of the aggregated dye molecules in these domains. The aggregates of THIATS formed circular domains with an average diameter of approximately 35 μm. Linear polarization of the excitation light beam led to fluorescence from two opposing quadrants of these circular domains. Upon rotation of the polarizer by 90°, the two other opposing quadrants became fluorescent whereas the fluorescence from the former fluorescent quadrants was extinguished. The orientation of the overall transition moment of these aggregates was found to be radial with relation to the large circular domains. Therefore, we proposed a model of radial growth of aggregated THIATS molecules, from a nucleation site into circular domains where the dye molecules adopt a brickstone arrangement.

The effect of neutral helper lipids on the structure of cationic lipid monolayers

“…Electronic supplementary material, figure S2 gives an example of an isotherm showing the collapse of a DODAB monolayer on an aqueous subphase containing 10 mM NaCl. As previously noted by Vranken et al [9], published isotherms of DODAB vary in terms of collapse surface pressure, lift-off area, and position and length of the plateau, owing to the sensitivity of the lipid to temperature and subphase salt concentration, and the isotherm reported here, although qualitatively similar, differs in terms of the aforementioned features from those presented for DODAB on pure water (see [8,9,11,25 -28]). Isotherms of the monolayers formed by the head group (d 3 -) and chain (d 74 -) deuterated versions of DODAB were also examined (figure 1) in order to verify that deuteration of the DODAB molecule did not cause any significant deviation in surface behaviour, particularly at the surface pressures of interest here, namely 5, 20, 30 and 40 mN m 21 .…”

“…Electronic supplementary material, figure S2 gives an example of an isotherm showing the collapse of a DODAB monolayer on an aqueous subphase containing 10 mM NaCl. As previously noted by Vranken et al [9], published isotherms of DODAB vary in terms of collapse surface pressure, lift-off area, and position and length of the plateau, owing to the sensitivity of the lipid to temperature and subphase salt concentration, and the isotherm reported here, although qualitatively similar, differs in terms of the aforementioned features from those presented for DODAB on pure water (see [8,9,11,25 -28]). …”

In-situ observation of the aggregated morphology and interaction of dialkyldimethylammonium bromide with DNA at air/water interface by Brewster angle microscopy

“…More in general, any impurities existing in the sample or the subphase could influence the shape of the isotherm and phase transition pressure when the spreading amount is large enough. However, neither have DODAÁBr in our samples nor any others from the related literatures been presented details on the definite amount of impurities, which affect the results [10]. So we measure the k -A isotherms of DODAÁBr several times under preset experiment conditions.…”

J-aggregates of thiacyanine dye organized in LB films: Effect of irradiation of light

“…Vranken et al [21] investigated the domains of J-aggregates formed upon adsorption of the thiacarbocyanine dye THIATS ( 3,3′ -disulfopropyl-5,5′ -dichloro-9-thylthiacarbocyanine) onto a Langmuir film of the oppositely charged amphiphile dioctadecyldimethylammonium bromide at the airwater interface. They proposed a model of radial growth of aggregated THIATS molecules, from a nucleation site into circular domains where the dye molecules adopt a brickstone arrangement.…”