Anisotropic Growth of J Aggregates of Pseudoisocyanine Dye at a Mica/Solution Interface Revealed by AFM and Polarization Absorption Measurements

Abstract

We investigated the J-aggregation process of pseudoisocyanine chloride at a mica/solution interface by using tapping mode atomic force microscopy (TM-AFM) and polarization absorption measurements. At a mica/solution interface, pseudoisocyanine chlorides form J aggregates that have three-dimensional leaf-like island structures. The islands are anisotropically oriented with respect to the lattice of a mica substrate. This anisotropic alignment may result from the epitaxial interaction between the positively charged N atoms of the molecules and the regularly aligned negative holes left by the dissociating K+ ions. On the basis of both the orientation of islands to the lattice of a mica and the epitaxial interaction, we proposed that in the internal structure of the J aggregate, the long axis of the dye molecules is parallel to the long axis of the islands.

Aggregation and Decomposition of a Pseudoisocyanine Dye in Dispersions of Layered Silicates

“…Therefore, the dye cations are adsorbed heterogeneously at the surface, forming islands of aggregates of partially covered silicate particles and leaving some silicate particles uncovered. Heterogeneous distribution of the dye aggregates forming islands has been already proven directly by atomic forced microscopy for PIC/mica reaction systems (32). Therefore, in some cases the size and the type of the aggregates are not much affected by the dye/silicate ratio and the aggregation takes place also at very low dye loadings, as proven recently (42).…”

“…This study revealed the specific orientation of PIC J-aggregates, controlled by the symmetry of ditrigonal holes at the mica surface. This indicates that the positively charged nitrogen atoms of the PIC cations are oriented to the holes in the mica basal planes, with the dye cation axis almost parallel to the surface (32). The interaction of PIC with various layered silicates has been investigated in other works, with the J-aggregation of the dyes being interpreted as dependent on silicate particle size (33,34).…”

Self-assembly of acridine orange dye at a mica/solution interface: Formation of nanostripe supramolecular architectures

“…PIC is a delocalized π -electron system with a nonplanar chemical structure, and head-to-tail intermolecular interactions between these molecules bring about J aggregation. In addition, optical properties of the interfacial J aggregate are found to be significantly different from those of the solution-phase aggregates [26][27][28][29]. Because mica has a planar surface with periodic ionexchange sites that allow the biding of cationic molecules, interfacial J aggregation of PIC was induced also by the electrostatic interaction between the dye cations and regularly aligned anionic sites on mica [26][27][28][29].…”

“…We have been interested in interfacial aggregation phenomena of cationic dye molecules represented by pseudoisocyanine (PIC), because this dye forms self-assembled J aggregates (ordered aggregates) at the mica/solution interface [26][27][28][29]. PIC is a delocalized π -electron system with a nonplanar chemical structure, and head-to-tail intermolecular interactions between these molecules bring about J aggregation.…”

Probing Nanoscale Domains of J-Aggregates Deposited on a Mica Surface

“…A growth scenario for aggregation on the solution/ mica interface was proposed based on AFM measurements. 18 At the end, we discuss the adsorption of TTBC molecules on a mica surface. How are TTBC molecules arranged on the surface?…”