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

Abstract

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.