Spectroscopic and AFM Studies on the Structures of PseudoisocyanineJAggregates at a Mica/Water Interface

Abstract

J aggregates of a pseudoisocyanine dye (PIC) at a mica/solution interface were in situ observed in solution for the first time by atomic force microscopy (AFM), confirming formation of the aggregates showing a narrow J absorption band (peak, ∼580 nm; line width (HWHM), ∼120-125 cm -1 ) at room temperature. The J aggregates possessed the three-dimensional island structure with the height of about 3-6 nm, consisting of at least ∼10 6 PIC molecules, but not a two-dimensional monolayer structure. The growth processes of the J aggregates were discussed on the basis of the morphological changes of the islands with a dye concentration (i.e., Volmer-Weber type growth process), while the optical properties such as the absorption peak position, line width, or fluorescence lifetime (∼50 ps) were unchanged. These results indicated that the physical aggregation size observed was much larger than the coherence size of the J aggregate.

Methylene Blue Interactions with Reduced-Charge Smectites

“…Absorption spectra of J-aggregates are characterized by strong, narrow bands that are shifted to longer wavelengths with respect to absorption bands for the monomers. J-aggregates are a coherent head-to-tail coupling of dye cations, where the ions are inclined with the longitudinal axis at angles <55 ~ relative to the surface (Yao et aL, 1999), as was observed for MB orientation on the mica surface (H~ihner et aL, 1996). A less densely packed structure of J-aggregates, resulting from head-to-tail coupling (Yao et al, 1999), should prevail on lower charge density surfaces.…”

Fluorescent J-aggregates of cyanine dyes: basic research and applications review

“…Increasing the pH stimulates the formation of more regular J-aggregate structures with the increasing amount of participating molecules in the coherence domain, so that the formation of several pH-dependent forms was reported [130]. The J-aggregates are readily formed on different solid supports [131], as it will be seen below.…”

Chiral assembly of achiral pseudoisocyanine with D- and L-phenylalanine

“…Achiral J-aggregates of PIC were characterized by near-field scanning optical microscopy [16] , cryo-transmission electron microscopy [17,18] , atomic force microscopy [19] , absorption spectroscopy [20,21] , fluorescence spectroscopy [22] and other spectroscopic methods. Chiral J-aggregates of PIC determined by circular dichroism (CD) spectroscopy were also reported in some studies.…”