Solid-state Fluorescence Enhancement Research Articles

クラスレート形成能を有する複素環キノール系蛍光色素の固体光物性と機能性

Organic fluorescent hosts which can exhibit sensitive color and fluorescence changes upon formation of host-guest inclusion complexes in the crystalline state can be one of the most promising materials for the construction of desirable solid-state fluorescent system and are attractive materials for their potential applications in analytical and material sciences. For this purpose, we have designed and synthesized several kind of heterocyclic quinol-type fluorescent hosts, (benzofurano[1,2-d]naphthoquionl-type, benzo[kl]xanthenol-type, benzofurano[3,2-b]naphthoquinol-type, and imidazo[5,4-a]anthraquinol-type fluorophores) whose crystals exhibit a dramatic fluorescence enhancement upon inclusion of various kinds of organic solvent molecules. The magnitude of the solid-state fluorescence enhancement is greatly dependent on the enclathrated guest molecules. It is confirmed from the spectral data and the X-ray crystal structures that the destruction of the host-host π-π interactions by the enclathrated guest molecules is the main reason for the guest-dependent fluorescence enhancement behavior. Furthermore, we found that these heterocyclic quinol-type fluorescent clathrands exhibit color and fluorescence changes upon exposure to various solvent vapors both in the crystalline state and thin-film state. We believe that these results are useful for the development of new solid-emissive chemosensors and for the improvement of pigmentary solid-state fluorescence in the applied field of optoelectronic devices.

Enantioselective Precipitation and Solid‐State Fluorescence Enhancement in the Recognition of α‐Hydroxycarboxylic Acids

Unusually sensitive: A chiral sensor based on 1,1′-bi-2-naphthol was prepared, which can provide visual enantioselective discrimination of α-hydroxycarboxylic acids. When the sensor and the acid have matched configurations, an enantioselective precipitation occurs, which is accompanied by a dramatic (over 950-fold) solid-state fluorescence enhancement (see picture).

Drastic solid-state fluorescence enhancement behaviour of imidazo[4,5- a]naphthalene-type fluorescent hosts upon inclusion of polyethers and tert-butyl alcohol

As one of the most promising materials for the construction of desirable solid-state fluorescent system, new solid-state fluorescent host–guest system, which consists of the imidazo[4,5- a]naphthalene-type fluorescent hosts 2 and sterically hindered guest molecules were designed and prepared. The crystals of 2 exhibit sensitive colour change and drastic fluorescence enhancement behaviour upon polyethers (diethylene glycol dimethyl ether (DGDM), diethylene glycol diethyl ether (DGDE) and diethylene glycol dibutyl ether (DGDB)) or tert-butyl alcohol. A comparison of the X-ray crystal structures of the guest-free and polyether- and tert-butyl alcohol-inclusion compounds indicates that the enclathrated polyether or tert-butyl alcohol molecule decrease the π-stacking between hosts and enlarge the distance between the host–host aromatic planes. On the bases of the spectral data and the crystal structures, the effects of the enclathrated sterically hindered guest on the drastic solid-state fluorescence enhancement behaviour of the host–guest crystals are discussed.

Solid-state fluorescence enhancement of organic dyes by photonic crystals

Photonic crystal (PC) films were fabricated by self-assembly of colloidal crystals using a vertical deposition method at invariant temperature and humidity. Organic dyes, whose emission wavelengths overlap the photonic stopbands of selected PCs, were deposited on the surface of PC films by thermal evaporation under vacuum. The fluorescence of organic dyes deposited on PCs is obviously enhanced in comparison with that on aluminium films and glass surfaces. There were 41-fold and 20-fold fluorescence enhancements when Rhodamine B base was deposited on the surface of a yellow PC film, compared with that on glass surface and aluminium film respectively, where PCs were utilized as a Bragg reflection mirror. The results show that the PCs are more effective and selective reflection mirrors than aluminium, and have potential applications in optoelectronic and lighting devices.

Dramatic Effects of the Substituents on the Solid-state Fluorescence Properties of Structural Isomers of Novel Benzofuro[2,3-c]oxazolocarbazole-type Fluorophores

Abstract Structural isomers of novel benzofuro[2,3-c]oxazolocarbazole-type fluorophores have been synthesized and their photophysical properties in solution and in the solid state were investigated; remarkable differences in the absorption and fluorescence spectra were observed between structural isomers in both states, and a drastic solid-state fluorescence enhancement was found to be caused by N-alkylation of fluorophores.

A novel strategy for fluorescence enhancement in the solid-state: affording rigidity to fluorophores packing

Solid-state fluorescence enhancement was achieved by preparation of rigid packing that was afforded by disposition of benzylamine into tubulate spaces, serving as a powerful and useful strategy for the enhancement.

Heterocyclic quinol-type fluorophores. Dramatic solid-state fluorescence enhancement behaviour of imidazoanthraquinol-type clathrate hosts upon inclusion of various kinds of organic solvent molecules

The crystals of novel imidazoanthraquinol-type clathrate hosts exhibit sensitive colour change and fluorescence enhancement behaviour upon enclathration of various kinds of organic solvent molecules. The optical changes are greatly dependent on the identity of the enclathrated guest molecules. To elucidate the enclathrated guest effects on the fluorescence properties of the crystals, the X-ray crystal structures of the guest-free and guest-inclusion compounds have been determined. On the basis of the spectral data and the crystal structures, the effects of the enclathrated guest on the solid-state photophysical properties of the clathrate compounds are discussed.

Guest specific solid-state fluorescence rationalised by reference to solid-state structures and specific intermolecular interactions

Guest specific solid-state fluorescence enhancement in 2,7-bis-(3-hydroxy-3,3-diphenylprop-1-ynyl)fluoren-9-one host:guest complexes may be ascribed to changes in the packing modes and hence host–host intermolecular interactions leading to excimer formation in the solid-state and the occurrence (or lack thereof) of specific intermolecular interactions.