Si nanoparticles are synthesized at a high rate(400-500 mg/h) using the perpendicular pulsed laser ablation(PPLA) on the silicon target at room temperature in Ar atmosphere.The PPLA method can also be used to obtain Si nanocrystal films with large areas on the glass substrate.These particles are etched with a mixture of hydrofluoric acid(HF) and nitric acid(HNO3) to reduce their sizes and the surfaces of these particles are passivated by the high-pressure water vapor annealing(HWA).After treating the particles exhibit blue emission(with maximum photoluminescence(PL) intensity at 404 nm) at room temperature.
The bidentate phosphine oxide ligand 1,8-bis(diphenylphosphino) naphthalene oxide (NAPO) and its EuⅢ complex 1 Eu(TTA)3(NAPO) (TTA=2-thenoyltrifluoroacetonate) were chosen to study the effect of bidentate phosphine oxide ligand on the photophysical properties of the corresponding complex. The intramolecular energy transfer processes of 1 were studied. The investigation showed that with bidentate structure NAPO could suppress solvent-induced quenching by enforcing the ligand-ligand interaction and the rigidity of the complex. Contrasted with the monodentate triphenylphosphine oxide (TPPO), NAPO had a higher first triplet excited energy level (T1) and a lower first singlet excited energy level (S1), which fitted to the corresponding excited energy levels of anion ligand TTA much more and supported more efficient singlet and triplet energy transfer in its EuIII complex.
The electronic structures and optical properties of oligothiophene substituted spirofluorenes are investigated theoretically with semi-empirical quantum chemical calculations. A theoretical investigation of the interaction between two perpendicular π-systems of various oligothiophene substituted spirofluorenes is conducted. The results demonstrate that the interaction between two perpendicular branches is reduced by oligothiophene substitutions. Photoexcitation induced relaxation is mainly located on one of the equivalent branches or the branch with longer conjugation length. In addition to these benefits brought by 9,9-spirobifluorene center, the specific oligothiophene moieties linked to the spiro center also have properties of significant merit, such as the ability to tune energy levels and emission colors by controlling the conjugation length.
CHEN RunFeng MA Cong PAN JingFang ZHENG Chao HUANG Wei
