Controllable Adsorption and Ideal H-Aggregation Behaviors of Phenothiazine Dyes on the Tungsten Oxide Nanocolloid Surface

Abstract

The monomer-aggregate equilibrium of four phenothiazine (PN) dyes, containing thionine (TH), methylene blue (MB), new methylene blue (NMB), and 1,9-dimethylmethylene blue (DMB), in the tungsten(VI) oxide (WO(3)) nanocolloid solution has been investigated by means of UV-vis spectroscopy. Addition of PN dye into the WO(3) nanocolloid solution brought about significant changes in the absorption spectrum, suggesting the formation of H-type (face-to-face fashion) trimer on the WO(3) nanocolloid surface. The adsorptivity of PN dyes onto the WO(3) nanocolloid surface was diminished by the raising the ionic strength, indicating the evidence of the electrostatic interaction between cationic PN dye and negatively charged WO(3) nanocolloids. The detail analysis of each spectral data provided insight into the effect of molecular structure of PN dyes on the adsorption and aggregation behaviors on the WO(3) nanocolloid surface. Moreover, in situ measurement of PN dye aggregation using the centrifugal liquid membrane (CLM) technique revealed that the aggregation of PN dyes on the WO(3) nanocolloid surface proceeded in a two-step three-stage (monomer --> dimer --> trimer) formation. The aggregation mechanism of PN dyes on the WO(3) nanocolloid surface was discussed on the basis of Kasha's exciton theory.

pH-Responsive Switchable Aggregation Phenomena of Xanthene Dyes Adsorbed on Tungsten(VI) Oxide Colloid Surface

“…A similar tendency has been previously reported by us for phenothiazine dye molecules adsorbed on the WO 3 colloid surface. 21 Moreover, in order to explicate the detail adsorption mechanism of the XN dyes onto the WO 3 colloid surface, the influence of ionic strength on the isotherm was also investigated under a constant XN dye concentration. As can be seen in Table S3 (see Supporting Information), the adsorption constants of XN dyes decreased with increasing in the sodium sulfate concentration.…”

Chirality induction and amplification in methylene blue H-aggregates viad- and l-phenylalanine pre-adsorbed on the tungsten oxide nanocolloid surface

“…[15,16] Their unique planar as well as rigid molecular geometry and aromatic electronic feature delocalized over the molecular frame enable them to be well investigated in the field 40 of constructing supramolecular assemblies by non-covalent interactions. In our previously reported work, [17] we found that the cationic MB dyes could form ideal H-type (face-to-face fashion) trimer on the negative charged tungsten(IV) oxide (WO 3 ) nanocolloid surface via the supramolecular self-assembly 45 process in the aqueous solution.Inspired by this finding, we have introduced the concept of "chirality" into the MB/WO 3 binary system by adding phenylalanine (Phe) which is one of the amino acids that are joined together to form proteins. Once the supramolecular 50 chirality in the MB/Phe/WO 3 ternary system has been achieved, one can expect that the system would show more important and more interesting optical active architectures from the viewpoints of chiral recognition mechanism and organic/inorganic hybrid material.…”

“…From TEM measurement, the resulting products are composed of almost spherical particles with diameters over the range 8-24 nm (average diameter: 17.6 nm). [17] 100…”

Molecular aggregates of Merocyanine 540 in aqueous suspensions containing natural and CTAB-modified bentonite

“…The dye aggregations occurring in various media are a common phenomenon producing dye aggregates. Although the dye aggregation occurs at higher dye concentrations in deionized (DI) water [5], it is observed at diluted dye concentration in the presence of polyelectrolytes [6], colloidal nanoparticles [7], and graphene oxide [8]. In this respect, two main aggregate types, which are called H and J-aggregates, are exited depending on their photophysical properties.…”