Search

TD-DFT quantum calculation was performed to predict and/or illustrate the electronic transition, the related absorption and emission maxima of some pyrrole-difluoroboron derivatives with different electron donor-acceptor unit or π-conjugated degree. Upon the calculated results, a new near infrared (NIR) fluorophore (abbreviated as TPBD-BP) was designed and fabricated through linking triphenylamine and pyrrole-difluoroboron units to benzothiadiazole (BTD) backbone. The fluorescence of TPBD-BP in solid state centered at 932 nm, which was 985 nm for TPBD-BP nanoparticles (TPBD-BP dots) encapsulated in PEG-6000. The fluorescence of TPBD-BP in both solid state and dots exhibited off-peak tail emission to NIR-II region (extended to 1300 nm). The TPBD-BP dots showed excellent water solubility, biocompatibility and aggregation induced emission (AIE), which was suitable to be applied in vivo imaging. NIR-II emission signal of TPBD-BP dots can be observed in the reproductive organ of normal nude mice after tail vein injection. This attractive combination of computational and experimental investigation would help to develop new-typed small-molecular NIR fluorophores., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Non-stoichiometric transition metal chalcogenides often have unexpectedly good semiconducting properties. In this paper, we focus on the seeking of potential semiconducting material in the ReSe system. The global and unbiased crystal structure searches were systematically conducted on ReSe material, using the advanced crystal structure prediction algorithms combined with the density functional theory. Three novel structures of ReSe were discovered within different pressures regions. The phase diagram of ReSe material was then constructed at pressure up to 200 GPa and temperature up to 2500 K, based on the quasi-harmonic approximation. We found ReSe possesses the trigonal P 3 ¯ m 1 symmetric structure at ambient pressure. Under further compression, it transits to the orthorhombic Pmmn structure at 87 GPa and then to the cubic P m 3 ¯ m structure at 129 GPa. The three new structures are all mechanically and thermodynamically stable within corresponding pressures regions. The low-pressure P 3 ¯ m 1 -ReSe manifests good semiconducting properties with the band gap of 0.162 eV, while the two high-pressure allotropes have metallic characteristics. The mechanical properties analyses suggest that special attention should be paid on the brittleness of the P 3 ¯ m 1 -ReSe structure, when it is used at high-stress conditions. This study sheds considerable light on the new structures and properties of the non-stoichiometric transition metal chalcogenides ReSe for future synthesis and further investigation. [ABSTRACT FROM AUTHOR]