Low pressure bottom-up synthesis of metal@oxide and oxide nanoparticles: control of structure and functional properties

Abstract

The experimental activity on core@shell, metal@oxide and oxide nanoparticles (NP) grown with physical synthesis, and more specifically by low pressure gas aggregation sources (LPGAS) is reviewed, through a selection of examples encompassing some potential application in nanotechnology. After an introduction on applications of NP, a brief description of the main characteristics of the growth process of clusters and NP in the LPGAS is given. Successively, some relevant case studies are reported: • Formation of native oxide shells around the metal cores in core@shell NP. • Experimental efforts to obtain magnetic stabilization in magnetic core@shell NP by controlling their structure and morphology. • Recent advancements in NP source design and new techniques of co-deposition, with relevant results in realization of NP with greater variety of functionalities. • Recent results on reducible oxides NP, with potentialities in nano-catalysis, energy storage and other applications. Although this list is far from being exhaustive, aim of the authors is to give the reader in a descriptive way some glimpse of the physics behind the growth and the studies of low pressure gasphase synthesized NP, with their ever-growing potentialities for a rational design of new functional materials.

Physical Synthesis and Study of Ag@CaF2 Core@Shell Nanoparticles: Morphology and Tuning of Optical Properties

“…The last method can make use of magnetron gas‐aggregation sources, and the NP properties can be finely tuned by varying their size distribution and structure, with a proper choice of parameters governing the growth conditions. Moreover, co‐deposition of different species with thermal evaporation sources is possible, in order to obtain core–shell geometry with different materials, or NPs embedded in a solid matrix . For instance, it was possible to study systematically the effect of non‐native oxide shell thickness and composition on the magnetic and structure properties of Ni@NiO, Ni@CoO, Ni@MgO, and FePt@MgO NP assemblies .…”

Adhesion, mobility and aggregation of nanoclusters at surfaces: Ni and Ag on Si, HOPG and graphene

“…Synthesis and manipulation of metal nanoparticles (NPs) is a research subject of tremendous impact in nanotechnology [1][2][3][4]. The bottom-up techniques for NP production includes the vast area of chemical synthesis [5], of self-assembling at surfaces [6], and of physical vapor deposition (PVD) techniques, like Molecular Beam Epitaxy (MBE) [7], pulsed laser ablation [8] and magnetron sputtering followed by gas aggregation [3,4,[9][10][11]. In all these cases, interaction of NP with surfaces is a crucial aspect, both of technological and scientific relevance [12][13][14][15].…”

Size control of Au nanoparticles from the scalable and solvent-free matrix assembly cluster source

“…Moreover, by decreasing the nanoparticle size down to 1 nm, 90% of the atoms of the particle are located at the surface and thus available to catalyze a reaction (Piella et al 2017). The effect of size on reactivity has been investigated for many different systems, both metals and oxides, including Cu (Reske et al 2014;Fernandez et al 2015), Ag (Boronat et al 2014), Ru (Antares Paoli et al 2016), Pt (Perez-Alonso et al 2012), Pd (Chen et al 2012), and CeO 2-x (Sun and Xue 2013, Spadaro et al 2015, D'Addato and Spadaro 2018. In the case of gold, it was reported in 1987 that this noble metal became catalytically active only when its size is below 5 nm (Masatake et al 1987;Ishida et al 2019).…”