Formation of a superatom monolayer using gas-phase-synthesized Ta@Si₁₆nanocluster ions

Abstract

The controlled assembly of superatomic nanocluster ions synthesized in the gas phase is a key technology for constructing a novel series of functional nanomaterials. However, it is generally difficult to immobilize them onto a conductive surface while maintaining their original properties owing to undesirable modifications of their geometry and charge state. In this study, it has been shown that this difficulty can be overcome by controlling the donor-acceptor interaction between nanoclusters and surfaces. Cations of Ta-atom-encapsulated Si(16) cage nanoclusters (Ta@Si(16)) behaving as rare-gas-like superatoms are synthesized in the gas phase and deposited on conductive surfaces terminated with acceptor-like C(60) and donor-like α-sexithiophene (6 T) molecules. Scanning tunneling microscopy and spectroscopy have demonstrated that Ta@Si(16) cations can be densely immobilized onto C(60)-terminated surfaces while retaining their cage shape and positive charge, which is realized by creating binary charge transfer complexes (Ta@Si(16)(+)-C(60)(-)) on the surfaces. The Ta@Si(16) nanoclusters exhibit excellent thermal stability on C(60-)terminated surfaces similar to those in the gas phase, whereas the nanoclusters destabilize at room temperature on 6 T-terminated surfaces owing to the loss of electronic closure via a change in the charge state.

Charge Transfer Complexation of Ta-Encapsulating Ta@Si16 Superatom with C60

“…The estimated intensity ratio was 1:1.93 between F and T by accounting for the inelastic mean free path of electron in solid C 60 (2.15 nm), in good agreement with the evaluated ratio. This suggests that the two-layered structure of C 60 is formed as shown in Figure , consistent with the STM measrements …”

Development and Functionalization of Visible-Light-Driven Water-Splitting Photocatalysts

“…Considering the mechanism of water-splitting photocatalysis ( Figure 3 ), researchers in the fields of catalytic chemistry, ceramic (semiconductor) materials chemistry, electrochemistry, metal NP/nanocluster (NC) chemistry [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ], surface spectroscopy [ 69 , 70 , 71 ], and theoretical chemistry [ 72 ] must be employed to create highly functional Vis-light-driven water-splitting photocatalysts. Actually, we specialize in the chemical composition/structure control of metal NCs and have succeeded in enhancing the functionality of some UV-light-driven water-splitting photocatalysts by applying these techniques to water-splitting photocatalysts [ 73 , 74 , 75 , 76 , 77 , 78 , 79 ].…”

Revisit of large‐gap Si16 clusters encapsulating group‐IV metal atoms (Ti, Zr, Hf)

“…Recently, Nakajima's group have synthesized the Ti@Si 16 and Ta@Si 16 clusters in a large scale (100 mg) by scaling up the clean dry‐process with a high‐power impulse magnetron sputtering . Moreover, the Ta@Si 16 clusters were deposited on highly oriented pyrolytic graphite or C 60 terminated surface, which exhibited excellent thermal and chemical stabilities; the latter system formed a heterojunction with spontaneous polarization and can serve as charge separation layers in nanoscale devices …”