Interaction Range for Photoexcitations in Luminescent Conjugated Polymers

Abstract

on the structure in the c-direction has not been obtained yet. The diameter of a PW 11 O 39 7± anion is assumed to be 1.09 nm, which is the same as that of a PW 12 O 40 3± Keggin anion. [14] The unit cell has 5 PW 11 O 39 7± anions, 30 C 12 TMA + cations, and 5 Na + cations. The expected pore diameter and wall thickness calculated from this model are 2.76 and 1.09 nm, respectively.In summary, a hexagonally ordered mesostructured material constructed with lacunar heteropoly anions and surfactant cations, WP, was synthesized by hydrothermal reaction of Na 2 WO 4 ×2H 2 O with H 3 PO 4 and C 12 H 25 N(CH 3 ) 3 Br at 403 K for 6 h. The chemical formula of WP obtained was [CH 3 (CH 2 ) 11 N(CH 3 ) 3 ] 6 NaPW 11 O 39 ×5.7H 2 O and a hexagonal superstructural model of the WP was proposed. Although heteropoly acids with a large pore structure have been of interest in catalysts and proton conductors with high performance, at present, the hexagonal structure of WP collapsed upon calcination. [15] Experimental The solution of surfactant and phosphate was prepared by dissolving 6.17 g of C 12 H 25 N(CH 3 ) 3 Br and 10 mL of 1 M H 3 PO 4 in 20 mL of deionized water. Subsequently 6.60 g of Na 2 WO 4 ×2H 2 O was added to the solution with vigorous stirring. Immediately a white gel precipitated. The molar composition of the resulting mixture was 1.0 Na 2 WO 4 ×2H 2 O : 0.5 H 3 PO 4 : 1.0 C 12 H 25 N(CH 3 ) 3 Br : 83.3 H 2 O. After being stirred at room temperature for 1 h, the mixture (ca. pH 8.3) was placed in a 40 mL Teflon bottle mounted in an autoclave and hydrothermally treated at 403 K for 6 h. The white solid product obtained (denoted by WP) was filtered, washed with deionized water, and dried at 353 K for 6 h. (NH 4 ) 3 PW 12 O 40 ×3H 2 O (PW 12 ) was purchased from Wako Pure Chemical Co. and Na 7 PW 11 O 39 ×nH 2 O (PW 11 ) and Na 8 HPW 9 O 34 ×nH 2 O (PW 9 ) were prepared according to the literature [9,16].

Direct observation of a time-delayed intermediate state generated via exciton-exciton annihilation in polyfluorene

“…[11][12][13][14][15][16] Higher excitation density usually results in an additional ultrafast decay channel ͑bimolecular decay͒, the importance of which diminishes as the excitation density decreases. Figure 1 shows the excitation-intensity-dependent pumpprobe results obtained from PFO with the probe wavelength at 480 nm.…”

Phosphorescence from iridium complexes doped into polymer blends

“…Förster energy transfer has been widely used to explain energy transfer phenomena in molecular dye systems, 24 photosynthetic aggregates, 25 polymer-polymer systems, 26,27 and more recently it has been applied to the polymerorganometallic emitter systems. 8,14 -16 Dexter energy transfer has also been studied in doped and undoped OLEDs.…”

Effects of π-Conjugation Attenuation on the Photophysics and Exciton Dynamics of Poly(p-phenylenevinylene) Polymers Incorporating 2,2‘-Bipyridines

“…Many discussions have focused on whether a π-conjugated polymer should be viewed as a one-dimensional semiconductor or a collection of oligomers with different conjugation lengths − Three major changes in the optical spectra of PPV derivatives have been observed following photoexcitation: ground-state bleaching, stimulated emission, and photoinduced absorption. There have been numerous debates on the origins of these spectral characteristics.…”

“…There have been numerous debates on the origins of these spectral characteristics. The origin of photoinduced absorption has been assigned to singlet excitons, triplet excitons, polarons, and photooxidized products. − The origin of stimulated emission has been assigned to a relaxed singlet exciton, a pair of tightly bound polarons, or localized singlet excitons. − ,− …”