Long-wavelength visible to near infrared photoluminescence from carbon-bridged styrylstilbene and thiadiazole conjugates in organic and aqueous media

Abstract

Efficient long-wavelength visible to NIR-emitting materials have been synthesized by use of rigid planar styrylstilbene as a donor component.

Water Fraction Dependence of the Aggregation Behavior of Hydrophobic Fluorescent Solutes in Water–Tetrahydrofuran

“…At f w = 40 vol %, the peak wavelength abruptly shifted back to 600 nm, and further increasing the water fraction at f w = 90 vol % induced a hypsochromic shift of the peak to 587 nm. This shift suggests a decrease in the ambient polarity of a fluorophore, which can be attributed to the formation of a hydrophobic environment as a result of the aggregation of solute molecules. ,, The significant decrease in the PLQY from 0.68 at f w = 30 vol % to 0.60 at f w = 40 vol % corroborates the occurrence of intermolecular interactions (blue dots in Figure b). The ACQ becomes more prevalent upon further increasing the water content, ultimately converging toward the PLQY value of the solid state (0.26).…”

“…The fluorescent material Cz-COPV2-BTz-COPV2-Cz was prepared according to literature procedures. 37 Perylene and tetraphenylethene were purchased from Fujifilm-Wako Pure Chemical Co. 1,1,2,3,4,5-Hexaphenylsilole and [[(3,5-dimethyl-1 H -pyrrol-2-yl)(3,5-dimethyl-2 H -pyrrol-2-ylidene)methyl]methane](difluoroborane) were purchased from Sigma-Aldrich and Tokyo Chemical Industry Co., respectively. These commercially available fluorescent materials were used without purification.…”

“…36 Here, we disclose the aggregation behavior of hydrophobic fluorescent molecules in water−THF mixtures in terms of the water fraction dependence and the role of THF as an amphiphilic solvent in such systems using physicochemical techniques, such as fluorescence spectroscopy and microscopy, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and wide-angle X-ray scattering (WAXS), by taking advantage of the distinct observational range of each method. As a hydrophobic fluorescent molecule, Cz-COPV2-BTz-COPV2-Cz 37,38 (Figure 1a), which is well-soluble in THF and insoluble in water, was selected as a model case because it forms stable aggregates and shows ACQ behavior while keeping a sufficient photoluminescence quantum yield (PLQY) over a broad range of solvent−mixture compositions, which facilitates the measurements. The behavior of other representative hydrophobic fluorescent materials was also examined by DLS, which revealed that their size change showed a similar solvent mixing ratio dependence, thus suggesting that the formation and size dependence of the hydrophobic solute aggregates follow a general mechanism.…”

Photophysical Properties of Donor–Acceptor−π Bridge–Acceptor Sensitizers with a Naphthobisthiadiazole Auxiliary Acceptor: Toward Longer-Wavelength Access in Dye-Sensitized Solar Cells

“…Since both of these properties are important properties to incorporate in future dye designs, we sought to explore the NTz unit in nonporphyrin organic dyes with a strong ICT character. NTz fragments are well known for applications in polymer solar cells with higher electron-accepting ability than BTD groups. − Additionally, the NTz unit is a rigid unit that can incorporate planarity while extending conjugation in the molecule to enhance ICT. Based on this observation, we have designed five different dyes by substituting the BTD unit with the NTz unit.…”