Platinum Nanoparticles Functionalized with Ethynylphenylboronic Acid Derivatives: Selective Manipulation of Nanoparticle Photoluminescence by Fluoride Ions

Platinum nanoparticles functionalized with 4-ethynylphenylboronic acid pinacol ester (Pt–EPBAPE) were successfully synthesized by a simple chemical reduction procedure. Because of the formation of conjugated metal–ligand interfacial linkages, the resulting nanoparticles exhibited apparent photoluminescence arising from the nanoparticle-bound acetylene moieties that behaved analogously to diacetylene derivatives. Interestingly, the nanoparticle photoluminescence was markedly quenched upon the addition of fluoride ions (F^–). In contrast, significantly less or virtually no change was observed with a variety of other anions such as Cl^–, Br^–, I^–, NO₃^–, HSO₄^–, H₂PO₄^–, ClO₄^–, BF₄^–, and PF₆^–. The high selectivity toward fluoride ion is most probably because of the strong specific affinity of the boronic acid moiety to fluoride. The formation of B–F bonds led to the conversion of Bsp² to Bsp³, as manifested in ¹¹B NMR measurements, which impacted the intraparticle charge delocalization between the particle-bound acetylene moieties and hence the nanoparticle photoluminescence.