Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition

Abstract

, W. M. M. (2015). Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition. Nanotechnology, 26(9), 094002-1/11. [094002]. DOI: 10.1088/0957-4484/26/9/094002 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Bimetallic core/shell nanoparticles (NPs) are the subject of intense research due to their unique electronic, optical and catalytic properties. Accurate and independent control over the dimensions of both core and shell would allow for unprecedented catalytic performance. Here, we demonstrate that both core and shell dimensions of Pd/Pt core/shell nanoparticles (NPs) supported on Al 2 O 3 substrates can be controlled at the sub-nanometer level by using a novel strategy based on atomic layer deposition (ALD). From the results it is derived that the main conditions for accurate dimension control of these core/shell NPs are: (i) a difference in surface energy between the deposited core metal and the substrate to obtain island growth; (ii) a process yielding linear growth of the NP cores with ALD cycles to obtain monodispersed NPs with a narrow size distribution; (iii) a selective ALD process for the shell metal yielding a linearly increasing thickness to obtain controllable shell growth exclusively on the cores. For Pd/Pt core/ shell NPs it is found that a minimum core diameter of 1 nm exists above which the NP cores are able to catalytically dissociate the precursor molecules for shell growth. In addition, initial studies on the stability of these core/shell NPs have been carried out, and it has been demonstrated that core/shell NPs can be deposited by ALD on high aspect ratio substrates such as nanowire arrays. These achievements show therefore that ALD has significant potential for the preparation of tuneable heterogeneous catalyst systems.S Online supplementary data available from stacks.iop.org/NANO/26/094002/mmedia

Review Article: Catalysts design and synthesis via selective atomic layer deposition

“…Weber et al demonstrated that when fabricating Pd@Pt core shell nanoparticles, the Pt shell thickness growth rate was 0.03 6 0.01 nm/cycle corresponding to $0.14 Pt atomic monolayer per cycle. 56 The results were similar to our findings. 13 In addition, the ALD methods are versatile since they allow for independent tuning of the core and shell diameter.…”

“…O 2 dissociation usually prefers to take place on a metal surface, leading to the formation of active oxygen atoms to decompose and activate MeCpPtMe 3 molecules for the following reactions. [55][56][57] Kessels and coworkers reported that when the O 2 partial pressure decreased to 7.5 mTorr, the growth of Pt on Al 2 O 3 was inhibited. 36 No Pt growth was observed on Al 2 O 3 surface even after 600 cycles.…”

“…In a following study, they demonstrated this selective ALD method enabled to prepare core shell nanoparticles on high surface area support. 56 The substrate was high density array of Al 2 O 3 covered GaP nanowires that were interest for fuel cells' or sensors' applications. Along with reducing the reactant partial pressure, the choice of coreactant could also facilitate selective ALD for core shell nanoparticles fabrication.…”

Core–Shell-Structured Low-Platinum Electrocatalysts for Fuel Cell Applications

“…This feature is especially attractive for the synthesis of heterostructured materials used in catalysis and nanodevices [362][363][364][365]. The ALD has also been explored as an alternative method for the preparation of advanced heterostructured and core-shell-structured electrocatalysts, such as Pd@Pt and Ni@Pt [368,374,[377][378][379][380]. For example, Cao et al [366] synthesized uniform Pd@Pt core-shell-structured electrocatalysts using the ALD technique with ODTS self-assembled monolayers as substrates (Fig.…”

Interfacial strain and defects in asymmetric Fe–Mn oxide hybrid nanoparticles

“…sputtering, 1 radiolysis, 2 atomic layer deposition 3 ) and chemical (e.g. sputtering, 1 radiolysis, 2 atomic layer deposition 3 ) and chemical (e.g.…”