Single-walled carbon nanotubes theoretically possess ultimate intrinsic tensile strengths in the 100–200 GPa range, among the highest in existing materials. However, all of the experimentally reported values are considerably lower and exhibit a considerable degree of scatter, with the lack of structural information inhibiting constraints on their associated mechanisms. Here, we report the first experimental measurements of the ultimate tensile strengths of individual structure-defined, single-walled carbon nanotubes. The strength depends on the chiral structure of the nanotube, with small-diameter, near-armchair nanotubes exhibiting the highest tensile strengths. This observed structural dependence is comprehensively understood via the intrinsic structure-dependent inter-atomic stress, with its concentration at structural defects inevitably existing in real nanotubes. These findings highlight the target nanotube structures that should be synthesized when attempting to fabricate the strongest materials.

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Thermal radiation is the most primitive light emission phenomenon of materials. Broadband radiation from red-hot materials is well known as the kick-starter phenomenon of modern quantum physics in the early twentieth century; even nowadays, its artificial control plays a central role in modern science and technology. Herein, we report the fundamental thermal radiation properties of intrinsic one-dimensional semiconductors and metals, which have not been elucidated because of significant technical challenges. We observed narrow-band near-infrared radiation from semiconducting single-walled carbon nanotubes at 1000–2000 K in contrast to its broadband metallic counterpart. We confirm that the ultra-narrow-band radiation is enabled by the thermal generation of excitons that are hydrogen-like neutral exotic atoms comprising mutually bound electrons and holes. Our findings uncover the robust quantum correlations in intrinsic one-dimensional semiconductors even at 2000 K; additionally, the findings provide an opportunity for excitonic optothermal engineering toward the realization of efficient thermophotovoltaic energy harvesting.

The syntheses, X-ray structures, and homogeneous Lewis acid catalytic activities for the Mukaiyama–aldol reaction of four tetranuclear HfIV and ZrIV cluster cations, which are sandwiched between two 1,2-di-lacunary α-Keggin polyoxometalates (POMs) and between two 1,4-di-lacunary POMs, are described, i.e., [[{M(H2O)}2{M(H2O)2}2(µ-OH)3(µ3-OH)2](α-1,2-PW10O37)2]7− (M = Hf 1 and M = Zr 2) and [{M4(H2O)4(µ-OH)2(µ3-O)2}(α-1,4-PW10O37)2]8− (M = Hf 3 and M = Zr 4), respectively. Evaluated was homogeneous Lewis acid catalysis of the Mukaiyama–aldol reaction in aqueous/CH3CN mixed media at room temperature under air by water-soluble sodium or lithium salts of sandwich-structured Hf/Zr-containing Keggin and Dawson POMs. In particular, the sodium salts of tetranuclear Hf/Zr cluster cations sandwiched between two di-lacunary α-Keggin POMs, i.e., Na-1–Na-4, showed the highest activities, compared with other cluster cations. The present POM-based sandwich-structured compounds gave products with high stereoselectivity, i.e., high anti-selectivity, regardless of high or low activities. The excellent stabilities of Na-1–Na-4 as catalysts, i.e., with no reduced activities, were confirmed even after reusing several times.