Lin Meijuan,Tang Qiang,Zeng Huijuan,Xing Guang,Ling Qidan
Several new Ir(III) complexes with 2-(4-bromophenyl)-1 H -benzo[d]imidazole or 2-(4-bromophenyl)- 1-methyl-benzo[ d ]imidazole ligands as cylcometalated ligand and acetylacetonate or picolinate as the ancillary ligand were synthesized and their structures and photophysical properties were characterized. HOMO and LUMO energy levels and the molecular structures of Ir(III) complexes were scrutinized by DFT calculations. The complexes exhibited green luminescence at the maximum emission peaks at ca 495–522 nm. The methyl group substituent and replacing of acetylacetonate with picolinate complex can enhance the complex thermal stability. HOMO energy levels of the complexes vary from –4.99 to –5.44 eV, the LUMO energy levels are between –1.52 and –1.97 eV.
Huanhuan Sun,Hongyan Yu,Boyang Han,Junjie Ma,Rensheng Wang,Yanping Song
Pressure-induced surface-enhanced Raman spectroscopy (PI-SERS) is among the foremost achievements of high-pressure fields, benefiting from the advantage that pressure-modulated interactions between substrates and molecules overcome the weakness of individual substrates or molecules. However, the pressure corresponding to PI-SERS enhancement is currently still at a low-pressure stage within 8 GPa. Therefore, how to realize PI-SERS enhancement under higher or ultrahigh pressure remains a huge challenge. Here, we applied few-layer WS2 (FL-WS2) nanosheets as PI-SERS substrates and selected 4-mercaptobenzoic acid (4-MBA) molecules with a big energy gap as probes to explore PI-SERS enhancement in more depth. The experimental results indicate that the PI-SERS signals increase gradually as pressure increases and reaches a maximum at 18 GPa, which has set a pressure record for the PI-SERS field so far. Different from the C exciton resonance-induced SERS intensities at ambient conditions, the charge-transfer transition between FL-WS2 and 4-MBA is strengthened via the pressure-induced increase in the band gap of FL-WS2 and decrease in the highest-occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gap of 4-MBA, thus enhancing PI-SERS signals accordingly. Therefore, this strategy will be beneficial for practical applications in the field of optoelectronics and for the design of other PI-SERS sensors for trace detection in complex and extreme environments.
Rechargeable magnesium batteries are a potential selection for large-scale energy storage technologies, but development of cathode materials is the major difficulty at present. Organic polyimides are promising magnesium battery cathodes with the open and amorphous frameworks as well as enhanced charge delocalization. However, only two carbonyls are redox-active out of four for each imide unit, which largely limits the capacity. Herein, a new polyimide containing disulfide bond is fabricated and studied as cathode for rechargeable magnesium batteries. This polyimide shows a high capacity beyond the traditional two-electron principle. A mechanism study demonstrates that carbonyl enolization and disulfide bond break/formation occur in the redox process, leading to formation/break of sulfur-oxygen bond. This sulfur-oxygen bond enhances enolization and electron delocalization, resulting in an improved capacity. Further theoretical computation indicates a charge transfer within this sulfur-oxygen bond. The two-electron reduction state exhibits quite low HOMO and LUMO energy levels, which makes the disulfide bonded polyimide have a higher tendency to accept more electrons and a higher oxidation stability after reduction.
危险品化学品经营许可证（带存储）