Galvanic synthesis of AgPd bimetallic catalysts from Ag clusters dispersed in a silica matrix

Abstract

While bottom-up synthetic strategies for the formation of near-monodisperse clusters have attracted much attention, top-down synthetic strategies in which metals are dispersed into clusters can also be viable. In this...

Atom-Precise Ag Clusters as Precursors for Selective Bimetallic AgPd Heterogeneous Catalysts

“…44−46 Notably, lower CN values are seen for Ag−M than Pd−M for samples with low Pd loadings, which suggests that Pd atoms are predominantly in subsurface locations in these clusters (despite being reduced onto the Ag) and Ag atoms dominate the surface in these samples. 40 This is consistent with the observation made recently by Gedara et al that Ag atoms can migrate to cover Pd islands on Ag(111) in minutes at room temperature. 47 However, this trend reverses at higher Pd loadings, and much lower Pd-M CNs are seen for Pd-rich AgPd clusters which suggests most Pd is on the surface of such clusters (Scheme 1).…”

“…Meanwhile, the Pd 3d 5/2 peak initially shows a slight decrease in binding energy going from the 12:1-Ag:Pd/carbon to the 2:1-Ag:Pd/carbon sample, and then increases for samples with higher Pd loadings to a value that is similar to Pd metal (335.4 eV) . The red-shift of both the Pd and Ag data in the AgPd samples with moderate Pd loadings is consistent with previous work by our group while making Pd subsurface alloys via galvanic reactions . Abrikosov et al have attributed such changes in AgPd alloys in terms of interatomic charge redistribution of valence electrons and final state effects .…”

“…Similarly, the modeled Pd–M distances show an increase from the typical Pd–Pd bond distance of 2.75 Å in standard Pd fcc foils. These differences in bond distance strongly indicate the presence of heteroatomic bonding in the SD- x : y -Ag:Pd/carbon samples. − Notably, lower CN values are seen for Ag–M than Pd–M for samples with low Pd loadings, which suggests that Pd atoms are predominantly in subsurface locations in these clusters (despite being reduced onto the Ag) and Ag atoms dominate the surface in these samples . This is consistent with the observation made recently by Gedara et al that Ag atoms can migrate to cover Pd islands on Ag(111) in minutes at room temperature .…”

“…39 The red-shift of both the Pd and Ag data in the AgPd samples with moderate Pd loadings is consistent with previous work by our group while making Pd subsurface alloys via galvanic reactions. 40 Abrikosov et al have attributed such changes in AgPd alloys in terms of interatomic charge redistribution of valence electrons and final state effects. 41 These results suggest that the Pd atoms in samples with low Pd loading are in a very different chemical environment than the Pd atoms in samples with high Pd loadings.…”

Applications of Iron Oxide Nanoparticles against Breast Cancer

“…The biological method exploits the bottom-up approach, i.e., assembling atoms and molecules to make nanostructures. Although this process is safe and economical, it is prolonged and lacks a desirable control over the particle size [33]. Early detection of breast cancer, which is crucial to limit progression to the metastatic phase, is routinely achieved using mammography, ultrasound, and MRI [34,35].…”