小林 範久

Circularly polarized luminescence (CPL) has significantly increased the interest in biological fields. In this research, a water-soluble Eu(iii) complex with a helical complex structure, EuLCOOH, was incorporated in chiral DNA in aqueous solutions. The photoluminescence performance of this DNA/EuLCOOH hybrid system was investigated. Compared to EuLCOOH alone, emission intensity and emission lifetime were effectively improved in the presence of DNA. The major binding between EuLCOOH and DNA was proven to be the electrostatic interaction. Owing to this interaction, the chiral environment provided by DNA successfully induced CPL from EuLCOOH

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu3+ and Eu2+. Initially, the intrinsically stable Eu3+ complex showed intense red photoluminescence (PL) induced by f-f transitions. After the electrochemical reduction of Eu3+ to Eu2+, broad blue PL was observed attributed to the d-f transitions in the Eu2+ complex. This distinct blue luminescence from the Eu2+ complex was attributed to the effective stabilization of the Eu2+ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices.

We have demonstrated a multicolor electrochromic device (ECD) with a novel architecture. Different typical ECDs featuring commonly two flat transparent electrodes, a double electrical layer electrode is applied to the device as the counter electrode. By this architecture, even two EC molecules with different polarities mixed in the same ECD can display their unique color, respectively. This paper reports the effect of several commonly-used quaternary ammonium salts as electrolytes on color properties of the ECD featuring a hybrid capacitor architecture. The aim is to select the suitable electrolyte to fabricate multicolor ECD with excellent color performance. Among them, the electrolyte tetraethylammonium tetrafluoroborate performs most satisfactorily attributed to its small ion size and high conductivity. This novel, easily-fabricated, and high EC performance multicolor device provides an opportunity that will develop color ECDs and expand the potential of EC technology.

A solvent-free mechanochemical treatment is used to synthesize an Eu(III) hybrid material containing Eu(D-facam)3 and tetramethylammonium acetate (TMAOAc), mechEu(D-facam)3TMAOAc. The synthesis method is efficient and the reaction occurs within 10 s. Mechanochemically prepared mechEu(Dfacam)3-TMAOAc is proven to be a bimetallic compound, in which TMAOAc functions as a bridging molecule between multiple Eu(III) complexes. Compared with Eu(D-facam)3mechEu(D-facam)3-TMAOAc exhibits ultra-high luminescence, excellent circular polarization activity and thermal stability.