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 Bsp(2) to Bsp(3), as manifested in B-11 NMR measurements, which impacted the intraparticle charge delocalization between the particle-bound acetylene moieties and hence the nanoparticle photoluminescence.