Pyrazinacene luminescence enhancement by heat-activated surface adsorption and de-aggregation in a saponite colloidal system

Adsorption of Dye Molecules and Its Potential for the Development of Photoactive Hybrid Materials Based on Layered Silicates

“…Locking of the excited state conformation, however, is not only possible in molecular aggregates but could also happen in homogeneous dye solutions via steric hindrance or through associating individual dye molecules with ions or macromolecules 39 or entrapping them within hydrogels or inclusion complexes. 40 Our recent studies 14,17,41 together with the relevant papers of Takagi and his co-workers 42 43 for the adsorption of methylviologen monomers on the surfaces of layered silicates and it was named at first as surfacefixation-induced emission (S-FIE). 42,44 However, it should be noted that S-FIE includes two different phenomena: the adsorption-induced emission (AdIE) and the intercalationinduced emission (InIE) as well.…”

“…For instance, to prepare photoactive heterogeneous systems based on a pyrazinacene derivative, it was necessary to combine its adsorption on the applied silicate particles with a subsequent thermal treatment. 41 Without this treatment, only pyrazinacene aggregates with reduced photoactivity were formed in both aqueous solutions and in silicate colloidal dispersions at constant temperature. Although the usage of organic liquids increased the luminescence of the dye, the applications of these solvents is highly disadvantageous from an environmental point of view.…”

“…Adsorption of the pyrazinacene dye on layered silicate particles followed by thermal treatment was the only way to achieve luminescence comparable to that of the dye solutions in organic solvents. 41 The phenomenon of InIE or AdIE is also observable for other types of structures or materials. For instance, encapsulation of a dye conjugated to curcumin within halloysite nanotubes (a tubular layered silicate) was found to largely boost its fluorescence.…”