Structural Colored Balloons Responsive to pH Change

Structural colored balloons (SCBs) composed of poly­(4-vinylpyridine-<i>co</i>-styrene) (P4VP-PS) exhibited a pH-controlled structural color change in the presence and absence of <i>p</i>-toluenesulfonic acid. The diameter of the SCBs increased and decreased under acidic and neutral conditions, respectively. The different colors exhibited at different pH values supposedly resulted from a change in the shell thickness not only due to the change in the diameter of the SCBs but also due to the uptake of <i>p</i>-toluenesulfonic acid to the pyridyl side chain of P4VP-PS

Photocatalytic Dehalogenation of Aromatic Halides on Ta₂O₅‑Supported Pt–Pd Bimetallic Alloy Nanoparticles Activated by Visible Light

Dehalogenation of aromatic halides is one important reaction for detoxification and organic synthesis. Photocatalytic dehalogenation with alcohol, a safe hydrogen source, is one promising method; however, systems reported earlier need UV irradiation. We found that Pt–Pd bimetallic alloy nanoparticles (ca. 4 nm) supported on Ta₂O₅ (PtPd/Ta₂O₅), on absorption of visible light (λ > 450 nm), efficiently promote dehalogenation with 2-PrOH as a hydrogen source. Catalytic dehydrogenation of 2-PrOH on the alloy in the dark produces hydrogen atoms (H) on the particles. Photoexcitation of d electrons on the alloy particles by absorbing visible light produces hot electrons (e_hot^–). They efficiently reduce the adsorbed H atoms and produce hydride species (H^–) active for dehalogenation. The catalytic activity depends on the Pt/Pd mole ratio; alloy particles consisting of 70 mol % of Pt and 30 mol % of Pd exhibit the highest activity for dehalogenation