Influence of Crosslink Density on Electrical Performance and Rheological Properties of Crosslinked Polyethylene.

To investigate the influence of the crosslinked polyethylene (XLPE) structure on electrical performance, various analytical methods were employed to study polyethylene structures with different degrees of crosslinking. Dynamic rheological analysis was conducted to determine material shear viscosity, dynamic viscosity, storage modulus (G'), loss modulus (G″), and other rheological parameters. Additionally, the electrical performance of the material was analyzed by studying the phenomenon of space charge accumulation under direct current voltage. The results indicate that with an increasing mass fraction of the crosslinking agent, the crosslink density of crosslinked polyethylene initially increases and then decreases. When the dicumyl peroxide (DCP) content exceeds 1.0 wt.%, there is an accumulation of like-polarity space charges. The best rheological processing performance of crosslinked polyethylene is observed when the DCP content is in the range of 1.0-1.5 wt.%.

Synthesis and Spectroscopic Properties of Selenophene[3, 2-b]-Fused BODIPYs.

Fusion selenophene endows the chromophore with more intrinsic and special functions. Herein, nonsymmetric selenophene-fused BODIPYs were designed and synthesized starting from the selenophene unit. The fused ring of selenophene not only maintains the rigid structure of BODIPY but also further modulates its spectral properties. The newly prepared dyes possessed many promising properties including large molar extinction coefficients, low fluorescence quantum yields, and moderate singlet oxygen generation. Quantum calculations affirmed that the smaller singlet-triplet energy gap and larger spin-orbit coupling cause efficient intersystem crossing, thus enhancing the singlet oxygen generation yield. Furthermore, selenophene-fused BODIPY exhibited significant phototoxicity with negligible dark cytotoxicity, based on the fluorescence imaging of the reactive oxygen species detection experiment.

A Colormetric and Fluorescence Probe for Highly Specific Cu2+ and its Application in Live Cell Imaging.

Fluorescent probes are intriguing material for ion detection. In this study, 4,4-difluoro-4-bora3a,4a-diaza-s-indacene (BODIPY) containing a dipicolylethylenediamine unit was developed as a colorimetric and fluorescence "turn-off" probe for Cu2+. The probe exhibited higher selectivity for Cu2+ than other common metal ions with a detection limit of 8.49 µM. With increasing Cu2+ concentration, the probe showed a red-shift in the absorption spectrum as well as fluorescence quenching, possibly due to the intramolecular charge transfer effect of the probe-Cu(II) complex. Furthermore, the probe was used for imaging Cu2+ in living cells based on confocal fluorescence imaging. The results show that the probe is an effective tool for detection copper ions.

Nonsymmetric Benzo[a]fused and Thiophene/Thieno[3,2-b]thiophene[b]fused BODIPYs: Synthesis and Photophysical Properties.

The fusion of sufficient-electron heterocycle rings into the[a]/[b]-position of the BODIPY core would result in a large redshift wavelength, thus achieving red or near infrared emission. In this paper, we described the synthesis of nonsymmetric benzo[a]fused and thiophene/thieno[3,2-b]thiophene[b]fused BODIPY derivatives 2-3 while containing a reactive site, and then, 4-7 were developed by nucleophilic substitution reactions of 3 with various nucleophilic agents in high yields. X-ray crystallographic analysis of 2-7 revealed that the core structure adopted a planar geometry and π-π interactions were observed in the packing structure. BODIPYs 4 and 6-7 displayed a hypochromic shift in the absorption and bathochromic shift in the emission with increasing solvent polarity because of the formation of resonance structures resulting from the change of the C-N distance, which was rationalized by density functional theory (DFT)/time-dependent-DFT calculations.

Lysosome-targeting turn-on red/NIR BODIPY probes for imaging hypoxic cells.

A small series of fluorescent lysosome-targeting probes based on the BODIPY fluorophore and containing morpholine and nitro groups were rationally designed. These probes emitted light from green to NIR wavelengths, and provided specificity for imaging the lysosomes of hypoxic cells. The electron-withdrawing nitrophenyl group at the meso position was found to lead to highly efficient nonradiative decay of the S1 state, and hence a recovery of fluorescence when reduction of the nitro group occurred under hypoxic conditions.