Creating Genetic Materials of Metal Clusters
While the preceding chapters present the reactivity of metal clusters, elucidating the chemistry of condensed matter, studies of cluster reactivity also serve to reveal the microscopic aspects such as nucleation phenomena, formation of highly dispersed me
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Creating Genetic Materials of Metal Clusters
14.1 Introduction While the preceding chapters present the reactivity of metal clusters, elucidating the chemistry of condensed matter, studies of cluster reactivity also serve to reveal the microscopic aspects such as nucleation phenomena, formation of highly dispersed media like ultrafine particles and nanoscale materials/surfaces. It has been outlined in aforementioned chapters how the potential use of metal clusters, particularly the reaction products in initiating cluster-assembled materials, has generated reasonable research interest in the activity of clusters on surfaces [1–4]. Unique properties of abundant metal clusters were found to give rise to promising potential use, such as the catalytic properties of noble metal clusters [5, 6], the oxygen-etching resistance of certain aluminum clusters and the energetic materials production by cluster reactions [7–9], or the selectivity of band gap and optical properties based on specific precise clusters [10]. However, due to the free-electron characteristics of metal clusters and thus their corresponding reactivity, precisely controlled deposition onto surfaces proves to be difficult. Even assuming a cluster can be successfully soft-landed without implanting, embedding or fragmenting, in many cases the cluster on surfaces may deform thus losing its desirable electronic and geometric structure [11, 12]. Furthermore, even though a successful soft-landing onto a surface, clusters may still diffuse unless they bind to defect sites, step edges, or reactive sites; and depending on the abundance, they can agglomerate into large islands that no longer exhibit the original properties regarding the strongly size-dependent properties of small individuals [13]. In the gas phase, small clusters have been shown to exhibit substantially different properties compared with bulk materials, and also differ from each other even if just a single atom or electron is added or removed [14, 15]. Even the all-known challenges, extensive investigations have been undertaken on studying the deposited cluster systems which display so interesting characteristics that they have prompted the growth of an entire sub-field of cluster science [16–28]. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2020 Z. Luo and S. N. Khanna, Metal Clusters and Their Reactivity, https://doi.org/10.1007/978-981-15-9704-6_14
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14 Creating Genetic Materials of Metal Clusters
The electronic and geometric structures of the deposited clusters were investigated although a notable difference from the nascent clusters in gas phase [17, 19, 29, 30]. The deposition clusters can be a size distribution or a mass-selected species having an exact number of atoms, feasibly grown on diverse surfaces composed of metals, metal oxides, graphite and silicon etc. generally with controlled defect sites [31– 33]. Because of the small sizes, high specific surface area, likely fluorescence and flexible chemistry of the
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