Efficient Two-Photon Absorption Materials Consisting of Cationic Dyes and Clay Minerals

Abstract

We systematically investigated enhancement of the molecular two-photon absorption (TPA) cross sections (σ (2) ) of organic dyes confined in the interlayer space of clay films. Several possible mechanisms have been proposed to explain the enhanced TPA of dyes in the interlayer spaces of clays. The present study comprehensively investigates two of these mechanisms, namely, (1) enhanced molecular planarity and the consequent extension of the π-electron system and (2) enhanced molecular orientation. We fabricated transparent dyeÀclay films consisting of a synthetic saponite clay and four cationic dyes. Two of these dyes are expected to have enhanced planarity when they are hybridized with a clay mineral. The other two dyes are considered to retain the planarity of their conjugated π-electron systems when they are in solution or in the interlayer space of a clay. We experimentally measured the σ (2) of these dyes in a clay film and in solution and found that the σ (2) of all four dyes is enhanced in a clay film but that this enhancement is greater for the former two dyes. These results are explained in terms of the effects of (a) extension of the π-conjugated system due to the enhanced planarity, (b) reduced detuning energy due to the enhanced planarity, (c) enhanced molecular orientation, and (d) the occasionally hydrophobic environment of the interlayer space of clay minerals. The highest enhancement of σ (2) was observed for a porphyrin derivative, tetrakis(1-methylpyridinium-4-yl)porphyrin ptoluenesulfonate, for which σ (2) in a hybrid film was 13 times greater than that in a dimethyl sulfoxide solution. Therefore, hybridization of cationic dyes with a clay mineral is an effective design strategy for TPA materials.

Tunable High-Pressure Field Operating on a Cationic Biphenyl Derivative Intercalated in Clay Minerals

“…BP was assumed to be incorporated in the smectite with its π-plane almost parallel to the clay-layer surface. Space occupancy is defined as the percentage of the interlayer space that is occupied homogeneously by BP molecules 10 . Because the partial exchange of cations in smectites always occurs in a segregated manner and produces random interstratification 13 , a large variation in the space occupancy occurs at each interlayer space in the hybrid films.…”

“…For example, the Raman spectrum of oxygen molecules that are adsorbed in a metal–organic framework corresponds to that observed at 2 GPa 9 . In addition, tetrakis(1-methylpyridinium-4-yl)porphyrin is flattened in the smectite interlayer space, whereas the pyridinium ring is twisted with respect to the plane of the porphyrin ring in solution because of steric hindrance 10 , 11 . The interlayer space thus causes molecules to adopt a similar flattened conformation to that observed in a high-pressure field.…”

Silafluorene as a promising core for cell-permeant, highly bright and two-photon excitable fluorescent probes for live-cell imaging

“…Measures were also performed in DMSO in order to compare them with reported cross-section of analogous fluorenes. [31] All data are summarized in Table 2. SiFluo-L exhibits outstanding absorption cross-sections, up to 2150 GM regardless of the solvent used, with a maximum around 750 nm (Figure 3).…”

Hybrid systems based on organic dyes and clay minerals: Fundamentals and potential applications

“…Hybrid materials composed of clay minerals and organic dyes with non-linear optical properties have been studied by several research groups (Jehnichen et al, 2008;Kawamata et al, 2010;Suzuki et al, 2012;Epelde-Elezcano et al, 2014). Those authors used clay-mineral carriers for the restricted confinement of dye molecules to achieve a suitable molecular alignment and orientation for the optimization of NLO materials (Kawamata & Hasegawa, 2006;Suzuki et al, 2011). Another problem to be solved to fabricate composites that exhibit the properties of a real applicable optical material is perfect light transparency, low light scattering and homogeneity (Kawamata et al, 2010).…”