Microscopic Mechanism for Precise Control of the Sizes of Molybdenum Blue Nanorings.

Li, Mu; Xue, Binghui; Yin, Panchao · Nano Lett · 2024

basic_science · Level V

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Abstract

Molybdenum blue (MB) nanorings with monodispersed, well-defined structures can be feasibly prepared via treatment of molybdate solutions with reducing agents at acidic conditions. However, the hidden constraints that control their ring sizes have been unknown for decades. Herein, the formation of 3.4 and 4.1 nm nanorings, {Mo<sub>154</sub>} and {Mo<sub>176</sub>}, is monitored using small-angle X-ray scattering (SAXS) with systematically varied synthetic conditions. Results suggest that {Mo<sub>154</sub>} forms quickly in solution and then undergoes slow transformation into {Mo<sub>176</sub>} when reducing agents are used, while {Mo<sub>176</sub>} can form directly with MoCl<sub>5</sub> supplied as reduced Mo<sup>V</sup>. These are attributed to {Mo<sub>154</sub>} being the kinetic product catalyzed by the template-effect while {Mo<sub>176</sub>} is the thermodynamic product due to its low ring tension. Our findings unravel one of the long-standing mysteries in MB and point out effective routes for the precise synthesis of nanorings.