Squeezed-Out Technique To Prepare High-Quality PbBr-Based Layered Perovskite Langmuir-Blodgett Films Applicable to Cavity Polariton Devices.

We propose a promising preparation technique to construct optically high-quality Langmuir-Blodgett (LB) films of lead bromide-based layered perovskites having an organic-inorganic quantum-well structure called "squeezed-out technique." Using this technique, we successfully prepared PbBr-based layered perovskite LB films whose average roughness is small enough to apply them for cavity polariton devices. The small roughness reveals that one can prepare microcavities having a high quality factor by using the technique. In addition, optical simulation of a cavity using the LB film demonstrated that the cavity polariton device has a large Rabi splitting of 116 meV, suggesting a stable polariton formation in the cavity even at room temperature.

Thermoluminescence of coral skeletons: a high-sensitivity proxy of diagenetic alteration of aragonite.

Diagenetic alteration of aragonite coral skeletons causes changes in their chemical and isotopic compositions. Such altered coral samples are unsuitable for age dating or paleoclimate reconstructions. Recently developed microanalysis techniques have elucidated secondary aragonite precipitation and calcite overgrowth on primary aragonitic coral skeletons, but an effective screening method for bulk samples is still desirable. Although powder X-ray diffraction (XRD) analysis is widely used for this purpose, its detection limit for calcite (1-2% at best) is not sufficient to detect very small amounts of diagenetic calcite. Here, we propose that thermoluminescence (TL) spectra can be used to detect the presence of tiny amounts of secondary calcite in coral skeletons. We used a TL spectrometer with a Fourier-transform detector to detect the calcite component in TL spectra of powdered skeletons of modern and fossil corals (from 127 ka and 3.5 Ma) in which calcite was not detectable by XRD. The key element is manganese, because the TL emission efficiency and the partition coefficient of Mn are greater for calcite than for aragonite. As a result, the calcite spectral component becomes evident. Thus, the TL spectroscopic technique is a highly sensitive tool for screening fossil corals for diagenetic alteration.

Phthalimide Compounds Containing a Trifluoromethylphenyl Group and Electron-Donating Aryl Groups: Color-Tuning and Enhancement of Triboluminescence.

Trifluoromethylphenyl-substituted phthalimide derivatives favorably form triboluminescence (TL) active noncentrosymmetric crystals. Oligothienyl-, oligophenyl-, and naphthyl-substituted phthalimide derivatives were successfully developed as a series of metal free TL compounds. X-ray crystal structure analyses of bithienyl and naphthyl derivatives revealed noncentrosymmetric layer structures in the same direction. Introduction of suitable electron rich π-units such as thienyl groups enhances their photoluminescence and TL characteristics, and the colors can be also controlled in the visible region. A rigid naphthyl-substituted imide derivative exhibits extremely high TL performance.