(317c) Thermal Atomic Layer Deposition of Gold Nanoparticles for Catalysis: High-Precision & Scalable Production

Atomic layer deposition (ALD) has become an established technique for the growth of conformal, ultrathin films in, for example, semiconductor applications. However, it is also an attractive technique for the controlled growth of nanoparticles (NPs). As such, it can play an important role in the synthesis of nanostructured catalysts with high precision. Gold nanoparticles have been extensively studied for their applications in catalysis. For Au nanoparticles to be catalytically active, controlling the particle size is crucial [1,2]. While for several catalytic materials ALD precursors have been available already for a long time, only recently ALD precursors for gold have been developed [3, 4]

Here we present a low temperature (105 °C) thermal atomic layer deposition approach for depositing gold nanoparticles on TiO₂ with controlled size and loading using trimethylphosphino-trimethylgold (III) and two co-reactants (ozone and water) in a fluidized bed reactor. We show that the exposure time of the precursors is a variable that can be used to decouple the Au particle size from the Au loading. Longer exposures of water broaden the particle size distribution while longer exposures of ozone narrow it [5]. By studying the photocatalytic activity of Au/TiO2 nanocomposites we show how the ability to control particle size and loading independently can be used not only to enhance performance but also to investigate structure-property relationships. This study provides insights into the mechanism underlying the formation and evolution of Au nanoparticles prepared for the first time via vapor phase atomic layer deposition. Employing a vapor deposition technique for the synthesis of Au/TiO₂ nanocomposites eliminates the shortcomings of conventional liquid-based processes opening up the possibility of highly controlled synthesis of materials at large scale [6].

[1] Valden, M., Lai, X., & Goodman, D. W. (1998). Onset of catalytic activity of gold clusters on titania with the appearance of nonmetallic properties. science, 281(5383), 1647-1650.

[2] Li, L., Larsen, A. H., Romero, N. A., Morozov, V. A., Glinsvad, C., Abild-Pedersen, F., Greeley, J., Jacobsen, K.W & Nørskov, J. K. (2013). Investigation of catalytic finite-size-effects of platinum metal clusters. The journal of physical chemistry letters, 4(1), 222-226.

[3] Griffiths, M. B., Pallister, P. J., Mandia, D. J., & Barry, S. T. (2016). Atomic layer deposition of gold metal. Chemistry of Materials, 28(1), 44-46.

[4] Makela, M., Hatanpaa, T., Mizohata, K., Raisanen, J., Ritala, M., & Leskela, M. (2017). Thermal atomic layer deposition of continuous and highly conducting gold thin films. Chemistry of Materials, 29(14), 6130-6136.

[5] Hashemi, F. S. M., Grillo, F., Ravikumar, V., Benz, D., Shekhar, A., Griffiths, M., Barry, S. & van Ommen, J. R. (2020). Thermal Atomic Layer Deposition of Gold Nanoparticles: Controlled Growth and Size Selection for Photocatalysis. Nanoscale, accepted.

[6] van Ommen, J. R., & Goulas, A. (2019). Atomic layer deposition on particulate materials. Materials Today Chemistry, 14, 100183.