Multistep Galvanic Exchange Synthesis Yielding Fully Reduced Pt Dendrimer-Encapsulated Nanoparticles

Abstract

Here we outline a new method for synthesizing fully reduced Pt dendrimer-encapsulated nanoparticles (DENs). This is achieved by first synthesizing Cu DENs of the appropriate size through sequential dendrimer loading and reduction steps, and then galvanically exchanging the zerovalent Cu DENs for Pt. The properties of Pt DENs having an average of 55, 140, and 225 atoms prepared by direct chemical reduction and by galvanic exchange are compared. Data obtained by UV–vis spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and high-resolution electron microscopy confirm only the presence of fully reduced Pt DENs when synthesized by galvanic exchange, while chemical reduction leads to a mixture of reduced DENs and unreduced precursor. These results are significant because Pt DENs are good models for developing a better understanding of the effects of finite size on catalytic reactions. Until now, however, the results of such studies have been complicated by a heterogeneous mixture of Pt catalysts.

Electron Transfer Facilitated by Dendrimer-Encapsulated Pt Nanoparticles Across Ultrathin, Insulating Oxide Films

“…Prior to immobilization atop Al 2 O 3 -modified PPF electrodes, the free G6OH(Pt 55 ) DENs were characterized using UV−vis spectroscopy and STEM ( Figures S6 and S7, respectively). The results are fully consistent with prior reports, 51,63 and they indicate the presence of Pt 55 DENs having a size of 1.3 ± 0.2 nm.…”

“…We have previously shown that Pt DENs prepared by galvanic exchange are confined within their dendrimer hosts. 63,64 It is important, however, to demonstrate that they remain confined following immobilization onto the …”

Direct electrochemical detection of individual collisions between magnetic microbead/silver nanoparticle conjugates and a magnetized ultramicroelectrode

“…The magnetic UME used here consists of a Ni wire with a thin layer of Au deposited on its tip using galvanic exchange. 41 , 42 Specifically, a 50 μm Ni UME was prepared by sealing a Ni wire in a glass capillary. As shown in Scheme 2 , the Ni UME was then sealed in an acrylic plate using epoxy glue.…”

Precise localization of metal nanoparticles in dendrimer nanosnakes or inner periphery and consequences in catalysis

“…Although the encapsulation of MNPs inside dendrimers has been demonstrated by Crooks'groups 18 , the exact localization of MNPs in DENs still remained elusive 32 33 . Given the properties of MNPs 1 2 3 4 33 34 35 36 37 , the knowledge and understanding of this localization are important to optimize MNP engineering towards specific applications, and in particular catalysis. Here we report the relationship between the MNP localization and catalytic activity in 4-nitrophenol reduction (4-NP) to 4-aminophenol (4-AP) by NaBH 4 (refs 38 , 39 , 40 , 41 , 42 ) and CuNP-catalysed AAC reactions 43 of MNPs stabilized by either triazole-containing or triazole-free dendrimers.…”