Odoi Michael Y, Hammer Nathan I, Rathnayake Hemali P, Lahti Paul M, Barnes Michael D
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Chemphyschem. 2007 Jul 16;8(10):1481-6. doi: 10.1002/cphc.200700133.
Single-molecule fluorescence measurements of 2,7-bis(3,4,5-trimethoxyphenylethenyl)fluorenone (OFOPV) reveal narrow emission spectra concentrated around 540 nm, with weak emission at longer wavelengths. The wide scattering of emission-maximum wavelengths is attributed to varying molecular environments, with dimers or higher-order aggregates contributing to the low-energy emission. This spectral distribution indicates that emission from monomers of this model fluorenone is mostly green, which is consistent with contaminant emission (g-bands) often observed in fluorene- and polyfluorene-based organic light emitting diode (OLED) devices. A histogram of center wavelengths from 118 single-molecule spectra shows good agreement with the green emission previously observed in thermally stressed 2,7-bis(3,4,5-trimethoxyphenylethenyl)-9,9-diethylfluorene (OFPV). Whereas bulk OFPV exhibits blue fluorescence at about 480 nm, OFOPV bulk thin film measurements reveal red luminescence shifted to 630 nm. This unexpected peak position for bulk OFOPV shifts to higher energies (ca. 540 nm) upon dilution in a solid-state matrix, suggesting that the bulk red emission finds its origins in interactions between fluorenone molecules. Explanations for this red emission include aggregate or excimer formation or intermolecular energy transfer between fluorenone molecules.
对2,7-双(3,4,5-三甲氧基苯乙烯基)芴酮(OFOPV)进行的单分子荧光测量显示，其发射光谱狭窄，集中在540nm左右，在较长波长处发射较弱。发射最大波长的广泛散射归因于不同的分子环境，二聚体或高阶聚集体导致了低能量发射。这种光谱分布表明，该芴酮模型单体的发射大多为绿色，这与在芴和聚芴基有机发光二极管(OLED)器件中经常观察到的污染物发射(g带)一致。118个单分子光谱中心波长的直方图与先前在热应力2,7-双(3,4,5-三甲氧基苯乙烯基)-9,9-二乙基芴(OFPV)中观察到的绿色发射吻合良好。虽然本体OFOPV在约480nm处呈现蓝色荧光，但OFOPV本体薄膜测量显示红色发光移至630nm。在固态基质中稀释后，本体OFOPV的这个意外峰位置向更高能量(约540nm)移动，这表明本体红色发射源于芴酮分子之间的相互作用。对这种红色发射的解释包括聚集体或准分子的形成或芴酮分子之间的分子间能量转移。
