Gold nanoparticles have been extensively studied for their applications in catalysis. For Au nanoparticles to be catalytically active, controlling the particle size is crucial. 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 loading. Longer exposures of ozone narrow the particle size distribution, while longer exposures of water broaden it. 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.

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Water-soluble polyacrylamides have often been used to modify flow response in various water-based technologies and industrial processes, including paints, water treatment, paper manufacturing, and chemical enhanced oil recovery. Polymers are susceptible to degradation at combined high salinity and elevated temperature conditions which limits their overall performance. Hybrid mixtures of hydrophobically modified polyacrylamide (HMPAM) with hydrophobically modified silica nanoparticles (NPs) emerged as a promising strategy for achieving enhanced stability and high viscosity in brines having a high total dissolved solids (TDS) content and high hardness at elevated temperatures (>20 wt% TDS, including >1.5 wt% divalent cations at T > 70 °C). The rheological response of the hybrids at various concentrations of HMPAM and NPs was examined to investigate the synergic effects. Hybridization of HMPAM with NPs led to a higher viscosity at high salinity and elevated temperature. The viscosity improvement was more pronounced when the concentration of HMPAM was in the semi-dilute regime and concentration of NPs was higher than a critical threshold where the viscosity increased roughly by a factor of 1.5. Here we present the mechanisms of improved viscosity behaviour. The rheological data suggest the role of NPs in the bridging between HMPAM molecules, which in turn increases the hydrodynamic radius and consequently the viscosity of the hybrids.@en

Due to the safety challenges associated with the use of trimethylaluminum as a metal precursor for the deposition of alumina, different chemicals have been investigated over the years to replace it. The authors have investigated the use of aluminum tri-isopropoxide (TIPA) as an alternative alkoxide precursor for the safe and cost-effective deposition of alumina. In this work, TIPA is used as a stable Al source for atomic layer deposition (ALD) of Al₂O₃ when different oxidizing agents including water, oxygen plasma, water plasma, and ozone are employed. The authors have explored the deposition of Al₂O₃ using TIPA in ALD systems operating in vacuum and atmospheric pressure conditions. For thermal and plasma processes in vacuum ALD, a growth rate of 1.1-2 Å/cycle achieved over a range of 140-300 °C is shown. Film density, roughness, and composition have been tested using various characterization techniques confirming comparable film properties to the thermal ALD of trimethylaluminum and water. The thermal water process at atmospheric pressure ALD (AP-ALD) resulted in a growth rate of up to 1.1 Å/cycle with residual carbon below the XPS detection limit. AP-ALD on nanoparticles shows different growth modes on TiO₂ versus SiO₂ nanoparticle surfaces confirmed by transmission electron microscopy analysis. Using TIPA as an ALD precursor would open up the possibility for a safer and cost-effective process for deposition of Al₂O₃ in various applications.

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