Color tuning of cationic pyrene derivatives on a clay nanosheet: Retardation of gradual redshift on clay

Light Energy Accumulation from Pyrene Derivative to Tris(bipyridine)ruthenium on Clay Surface

“…Thus, the same quenching efficiency was shown for An-Py 2+ as was found for Py 4+ in earlier studies, but using one-fifth the amount of Ru 2+ . , Furthermore, when the loading amount of Ru 2+ reached 12.5–25.0% CEC (An-Py 2+ :Ru 2+ = 2–1:1), near-quantitative emission quenching was observed, which was also confirmed by measurements of the emission lifetime (τ), as shown in Figure . In the absence of Ru 2+ (An-Py 2+ /SSA, [An-Py 2+ ] = 25% CEC), the decay of the emission from An-Py 2+ (monitored wavelength =425 nm) was fitted well to two components (τ 1 = 0.23 ns [75%] and τ 2 = 1.1 ns [25%]) owing to the formation of an excimer . However, in the presence of Ru 2+ at 25% CEC, no decay of the emission from An-Py 2+ was observed within our apparatus response time (pulse width =0.4 ns, full width at half-maximum).…”

“…In the absence of Ru 2+ (An-Py 2+ /SSA), a strong emission band was observed from An-Py 2+ on SSA. Fluorescence quantum yields (Φ f ) were measured by absolute emission quantum yield measurement systems equipped with a calibrated integrating sphere, ,,,, and Φ f of An-Py 2+ /SSA was estimated to be 27.0 ± 1.0% . In contrast, the emission intensities of An-Py 2+ drastically decreased with a very small amount of Ru 2+ , and a new broad emission band from Ru 2+ appeared in the region of 550–750 nm (Figure , inset).…”

“…The quantitative adsorption of both An-Py 2+ and Ru 2+ onto SSA was confirmed by filtration, i.e., neither dye was detected in the filtrate solutions by absorption measurements. Further experimental details, analytical methods, and materials have been reported in previous papers. ,, …”

“…Based on the this point of view, we have synthesized a novel pyrene derivative substituting trimethylanilinium groups (An-Py 2+ ; Figure 1b), which exhibits strong absorption (ε ≈ 2.6 × 10 4 L mol −1 cm −1 at 355 nm) and a high fluorescence quantum yield (Φ f ≈ 90%) in water. 30 Moreover, An-Py 2+ effectively suppresses red shifts in its absorption and emission spectra when adsorbed on the SSA surface in comparison to Py 4+ . 30 From this experimental result, improvements are expected in the value of J and the efficiency of light energy accumulation between pyrene and Ru 2+ on the SSA surface.…”

“…This flattening leads to the enhancement of electron withdrawing and apparent extension of the π-conjugate within the Py 4+ molecule. − To avoid the redshift of pyrene on the SSA surface, the π-conjugation between the pyridinium ring and the pyrene moiety should be severed. Based on the this point of view, we have synthesized a novel pyrene derivative substituting trimethylanilinium groups (An-Py 2+ ; Figure b), which exhibits strong absorption (ε ≈ 2.6 × 10 4 L mol –1 cm –1 at 355 nm) and a high fluorescence quantum yield (Φ f ≈ 90%) in water . Moreover, An-Py 2+ effectively suppresses red shifts in its absorption and emission spectra when adsorbed on the SSA surface in comparison to Py 4+ .…”