We report the fabrication of platinum nanoclusters with a narrow size distribution on TiO 2 nanoparticles using atomic layer deposition. With MeCpPtMe 3 and ozone as reactants, the deposition can be carried out at a relatively low temperature of 250 C. Our approach of working with suspended nanoparticles at atmospheric pressure gives precise control of the material properties, high efficiency of the use of the platinum precursor, and the possibility for large-scale production of the nanostructured particles.

Atomic layer deposition (ALD) is a gas‐phase method to grow layers of solid materials with subnanometer precision. It has been invented independently in the Soviet Union in the 1960s under the name molecular layering, and in the 1970s in Finland under the name atomic layer epitaxy. ALD relies on alternatingly exposing a surface to gaseous reactants—separated by a purge step—that react in a self‐terminating manner. This article introduces the fundamentals of the surface chemistry of ideal ALD, including saturating and irreversible reactions, growth per cycle, monolayer concepts relevant to ALD, typical surface reaction mechanisms, saturation‐limiting factors, growth modes, area‐selective ALD, growth kinetics, and conformality. It also discusses typical deviations from ideal ALD. Over the years, many different ALD process chemistries have been developed. A range of reactor systems is available, depending on the type of substrate and required productivity. ALD is broadly applicable in practice since it couples nanoscale precision with a good scalability and can be used to deposit a large variety of materials. In recent years, the interest in ALD has been growing strongly. The most important sector regarding commercial applications of ALD is currently the semiconductor industry.

Atmospheric pressure atomic layer deposition for tight ceramic nanofiltration membranes: synthesis and application in water purification,

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In this paper, the authors demonstrate a novel spatial atomic layer deposition (ALD) process based on pneumatic transport of nanoparticle agglomerates. Nanoclusters of platinum (Pt) of $1 nm diameter are deposited onto titania (TiO 2 ) P25 nanoparticles resulting to a continuous production of an active photocatalyst (0.12-0.31 wt. % of Pt) at a rate of about 1 g min À1 . Tuning the precursor injection velocity (10-40 m s À1 ) enhances the contact between the precursor and the pneumatically transported support flows. Decreasing the chemisorption temperature (from 250 to 100 C) results in more uniform distribution of the Pt nanoclusters as it decreases the reaction rate as compared to the rate of diffusion into the nanoparticle agglomerates. Utilizing this photocatalyst in the oxidation reaction of Acid Blue 9 showed a factor of five increase of the photocatalytic activity compared to the native P25 nanoparticles. The use of spatial particle ALD can be further expanded to deposition of nanoclusters on porous, micron-sized particles and to the production of core-shell nanoparticles enabling the robust and scalable manufacturing of nanostructured powders for catalysis and other applications.

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We demonstrate the deposition of crystalline palladium nanoparticles on graphene nanoplatelets (Pd/graphene) via atmospheric pressure atomic layer deposition (ALD) carried out in a fluidized bed reactor. The nucleation and growth of Pd nanoparticles on the inert graphene surface was enabled by applying an ozone pretreatment step, without significantly affecting the graphene crystalline structure. Uniform nucleation on both basal planes and edges of the graphene was obtained. The Pd loading and dispersion as well as the average particle size could be controlled by varying the number of ALD cycles. By analyzing the evolution of the particle size distribution and spatial density, we obtained insights into the nucleation and growth of Pd ALD on graphene. Furthermore, by shortening the pretreatment time, selective growth of Pd nanoparticles on the edges of the graphene was achieved. The Pd/graphene fabricated with our method showed a significantly lower level of impurities compared to the Pd/graphene synthesized by wet chemistry routes. Our approach provides a 100% solvent-free, controllable and scalable process for producing the bulk quantities of Pd/graphene required for practical applications in, for example, catalysis.

Core-shell nanoparticles and other nanostructured particles have high potential in applications such as heterogeneous catalysis and energy conversion and storage. However, a hurdle in their utilization is that typically, large amounts of such nanostructured materials are required. Gas-phase coating using atomic layer deposition (ALD, a variant of chemical vapour deposition) can be used to provide the surface of a particle with either an ultrathin continuous coating or a decoration of nanoclusters. When carried out in a fluidized bed, ALD is an attractive way of producing nanostructured particles with excellent scale-up potential. We demonstrate the fabrication of catalysts by deposition of the active phase (Pt) on fluidized nanoparticles (TiO 2 P25) at atmospheric pressure. We show that ALD is a technique that 1) guarantees efficient use of the precursor; 2) allows precise control of the size and loading; 3) can be used for low and medium loading of catalysts by adjusting the number of repeated cycles; 4) leads to high-quality (low impurities level) end-products.