The Sub‐Nanometer Scale as a New Focus in Nanoscience

Abstract

Size is one of the central issues in nanoscience. The practical meaning of the term "sub-nanometric material (SNM)" requires two aspects: (1) its size should be at the atomic level; (2) it shows unique (size-related) properties compared to its nano-counterparts with larger sizes. Here, SNMs in the form of wires (SNWs) and the unique properties arising from their special size are reviewed. First, their polymer-like behavior, including rheological behavior and self-assembly, is dicussed. Their origins may stem from the special size and the ligands around the wire. Even a slight increase in diameter would risk the polymer-like behavior. Meanwhile, the ligands on SNWs are proportional to the inorganic entity at this scale. Consequently, surface ligands should have a profound impact on the properties, like catalysis, self-assembly, optics, etc. To reveal more potential applications, their applications in energy conversion are comprehensively reviewed. To some extent, characterization can greatly influence the way things are observed. Thus, some appropriate characterization techniques are briefly introduced. Finally, another emerging part of SNWs (atomic chain material) is briefly introduced. It is hoped that this review can provide new insights to this special scale.

The Synthesis of Sub-Nano-Thick Pd Nanobelt–Based Materials for Enhanced Hydrogen Evolution Reaction Activity

“…We observed that the generated he NBs were inclined to bend, twist, entangle, and form large bundles ( Figure 2, Supporting Information Figure S10). These observations might be due to the flexible nature of these sub-nanometric materials, 8 Figure S11), which suggested that the exposed basal planes were {110} facets, identical to those in eePtPd NBs. However, while {111} reflections were found in the Pd(0.9) NBs, 1/3(422) fringes were absent in the corresponding FFT patterns (Figure 2h, i) Thus we inferred that their exposed lateral facets could be {110}.…”

“…Moreover, the large ΔG tot difference of different nanocrystal morphologies would compensate for ΔG* if such a 1D structure could not be well-stabilized under proper conditions. We were able to satisfy the criterion by introducing ascorbic acid (AA), PVP, Hexacarbonylmolybdenum [Mo(CO) 6 , or dicobalt octacarbonyl [Co 2 (CO) 8 ] as a carbon monoxide (CO) source instead of CO gases, to ensure safety, and ethylenediamine (EN) into the synthesis. Mo(CO) 6 or Co 2 (CO) 8 release CO molecules at appropriate temperatures, which could be influenced by the reaction environment, such as water or ligands.…”

“…We were able to satisfy the criterion by introducing ascorbic acid (AA), PVP, Hexacarbonylmolybdenum [Mo(CO) 6 , or dicobalt octacarbonyl [Co 2 (CO) 8 ] as a carbon monoxide (CO) source instead of CO gases, to ensure safety, and ethylenediamine (EN) into the synthesis. Mo(CO) 6 or Co 2 (CO) 8 release CO molecules at appropriate temperatures, which could be influenced by the reaction environment, such as water or ligands. The inductively coupled plasma optical emission spectrometry (ICP-OES) results of different introduced compounds under the same reaction conditions showed that the highest percentage of Mo or Co in the products was 0.21% or 0.5%, respectively.…”

“…A reaction temperature at the lowest end of the optimal range (∼ 120°C) could aid in obtaining more favored products, that is, thinner belts. However, since Mo(CO) 6 had a relatively high decomposition temperature (150°C), we used Co 2 (CO) 8 , which featured a much lower decomposition temperature (50°C), to substitute for Mo(CO) 6 , to enable the reaction to proceed at lower temperatures (∼ 70°C). The results showed that the thickness and width of NBs were further attenuated (Supporting Information Figure S24).…”

Subnano Surface Engineering of TiO2 Nanoparticles by PET Molecular Layer Deposition: Tuning Photoactivity and Dispersibility

“…Subnano films allow a more efficient use of resources, and do not affect the geometry of even high-aspect-ratio nanostructured substrate materials (3). Furthermore, the controlled growth of subnano films may allow the fabrication of novel materials with unprecedented properties for several potential applications in energy conversions such as electrocatalysis and photocatalysis (4). Organic coatings are of interest due to the advantages they hold over their inorganic analogues, such as biocompatibility (5,6), lower raw material costs, and reduced environmental impact (7).…”