No abstract

Pyrene-conjugated monomeric (2) and dimeric (5) shaped-silsesquioxane (SQ) cages, as chemical sensors for detecting fluoride and polycyclic aromatic hydrocarbons (PAHs), were prepared by Heck-coupling reactions between vinyl-functionalized SQ cages and bromo-substituted pyrenes. These sensors give a remarkable deep-blue fluorescence, which could be quenched in the presence of fluoride and electron-withdrawing PAHs. Interestingly, both sensors 2 and 5 show a rapid detection toward PAHs, while a high number of vinylic silicon atoms in a monomeric cage-based sensor 2 detected fluoride relatively faster than a bulky dumbbell sensor 5. In addition, these sensors also provide a naked-eye color of fluoride detection through an intramolecular charge-transfer presenting in yellow and pink (λ max ∼ 495 and 520 nm) for mono and dumbbell sensors, respectively. The limit of detection for fluoride and PAH (e.g., 1pyrenecarboxaldehyde and 1-nitropyrene) detections is approximately 1−3 μM. The computational calculation for the further mechanistic study of PAHs detection revealed that an emission of SQ was absorbed by PAHs, thereby resulting in aggregationcaused quenching.

The catalytic performance of Mo 8 V 2 Nb 1 -based mixed-oxide catalysts for ethane partial oxidation is highly sensitive to the doping of elements with redox and acid functionality. Specifically, control over product distributions to ethylene and acetic acid can be afforded via the specific pairing of redox elements (Pd, Ni, Ti) and acid elements (K, Cs, Te) and the levels at which these elements are doped. The redox element, acid element, redox/acid ratio, and dopant/host ratio were investigated using a three-level, four-factor factorial screening design to establish relationships between catalyst composition, structure, and product distribution for ethane partial oxidation. Results show that the balance between redox and acid functionality and overall dopant level is important for maximizing the formation of each product while maintaining the structural integrity of the host metal oxide. Overall, ethylene yield was maximized for a Mo 8 V 2 Nb 1 Ni 0.0025 Te 0.5 composition, while acetic acid yield was maximized for a Mo 8 V 2 Nb 1 Ti 0.005 Te 1 catalyst.

Silsesquioxane cages or POSS can be used as crosslinkers in the superfast 15 minute synthesis of silicone elastomers. The elastomers show high mechanical strength, good thermal stability, and good superhydrophobic properties.