Biomimetic strategies to help mediate the synthesis of nanoparticles have been extensively studied to show that biomolecules, such as DNA, proteins and peptides, are efficient facilitators at generating nanomaterials under benign conditions. Using a peptide, small monodisperse Pd nanoparticles have been generated and utilized as efficient catalysts for Stille and Suzuki coupling in water at room temperature. Unfortunately, these nanocatalysts have a marked lack of reactivity towards aryl chlorides, due to the strength of the C−Cl bond inhibiting the oxidative addition step of Pd0. Plasmonic catalysis represents an attractive solution to overcoming this barrier. In this manner, long aspect ratio (length/width greater than 15) Au nanorods (AuNR) were functionalized with the Pd-binding peptide, Pd4 (TSNAVHPTLRHL), to promote controlled growth of Pd nanoparticles on the nanorod surface. This functionalization was carried out by the addition of a cysteine to the N-terminus of Pd4 (now termed CPd4). Ligand exchange between the existing surfactant molecule and the CPd4 peptide was apparent through the shifting of the transverse surface plasmon absorbance in UV-Vis, where a red shift of 10 - 15 nm was noted (Figure 2a). Once functionalized, Pd2+ was added to the CPd4-AuNR and the colloids were reduced overnight. Electron microscopy characterization showed the formation of Pd nanoparticle clusters on the surface of the CPd4-AuNR (Figure 2b). Subsequently, control samples of Pd2+ reduced overnight with AuNR not functionalized with CPd4 showed no formation of Pd nanoparticles on the nanorod surface (Figure 2c). Further catalytic studies involving Suzuki coupling as the model reaction will be used as proof of concept that the attachment of these active Pd nanoparticles to the AuNR surface will activate the oxidative addition step for aryl chlorides, thus opening up the reactivity of these catalysts into a broad range of inexpensive and useful substrates.

Pd-decorated Au nanorods via biomimetic techniques for use as plasmonic catalysts in Suzuki coupling of aryl chlorides

255th National Meeting (2018)

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