Abstract
Aluminum nanoclusters (Aln NCs), particularly Al13− (n = 13), exhibit superatomic behavior with interplay between electron shell closure and geometrical packing in an anionic state. To fabricate superatom (SA) assemblies, substrates decorated with organic molecules can facilitate the optimization of cluster–surface interactions, because the molecularly local interactions for SAs govern the electronic properties via molecular complexation. In this study, Aln NCs are soft-landed on organic substrates pre-deposited with n-type fullerene (C60) and p-type hexa-tert-butyl-hexa-peri-hexabenzocoronene (HB-HBC, C66H66), and the electronic states of Aln are characterized by X-ray photoelectron spectroscopy and chemical oxidative measurements. On the C60 substrate, Aln is fixed to be cationic but highly oxidative; however, on the HB-HBC substrate, they are stably fixed as anionic Aln− without any oxidations. The results reveal that the careful selection of organic molecules controls the design of assembled materials containing both Al13− and boron-doped B@Al12− SAs through optimizing the cluster–surface interactions.
Highlights
IntroductionAluminum nanoclusters (Aln NCs) are soft-landed on organic substrates pre-deposited with n-type fullerene (C60) and p-type hexa-tert-butyl-hexa-peri-hexabenzocoronene (HB-HBC, C66H66), and the electronic states of Aln are characterized by X-ray photoelectron spectroscopy and chemical oxidative measurements
Aluminum nanoclusters (Aln NCs), Al13− (n = 13), exhibit superatomic behavior with interplay between electron shell closure and geometrical packing in an anionic state
D, the corresponding O 1 s component can be observed in the lower trace of Fig. 1c even without O2 exposure. These results show that the Al13 NCs present on the C60 substrate are so reactive that the nascent NCs are oxidized after deposition by some residual gas in the vacuum chamber (
Summary
Aln NCs are soft-landed on organic substrates pre-deposited with n-type fullerene (C60) and p-type hexa-tert-butyl-hexa-peri-hexabenzocoronene (HB-HBC, C66H66), and the electronic states of Aln are characterized by X-ray photoelectron spectroscopy and chemical oxidative measurements. The substrate acidity has been reported to control the catalytic activity of size-selective platinum (Pt) clusters[10] In these studies, localized cluster–surface interactions are enhanced using metal oxide substrates[8,9] to avoid the generation of weakly bound nanoclusters (NCs) on a clean surface, because these NCs generally behave as a two-dimensional gas, resulting in aggregation[6]. Interactions that take place through charge transfer (CT), or more explicitly, electron transfer[11], are important in chemical reactions between two reactant molecules since they lead to the formation of intermolecular CT complexes that exhibit a new electronic transition known as a CT band[12] Their segregated stacking can lead to molecular electrical conductivity, including superconductivity[13,14]. Spectroscopic characterization by X-ray photoelectron spectroscopy (XPS) and oxidative reaction measurements of the Al13− and B@Al12− SAs on the organic substrates are conducted to reveal that superatomic behavior can be observed on the p-type organic substrates through CT interactions
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