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Size-controlled liquid phase synthesis of colloidally stable Co 3 O 4 nanoparticles.

Johannes KießlingSabine RosenfeldtAnna S Schenk
Published in: Nanoscale advances (2023)
Spinel cobalt(ii,iii) oxide (Co 3 O 4 ) represents a p-type semiconductor exhibiting promising functional properties in view of applications in a broad range of technological fields including magnetic materials and gas sensors as well as sustainable energy conversion systems based on photo- and electrocatalytic water splitting. Due to their high specific surface area, nanoparticle-based structures appear particularly promising for such applications. However, precise control over the diameter and the particle size distribution is required to achieve reproducible size-dependent properties. We herein introduce a synthetic strategy based on the decomposition of hydroxide precursors for the size-controlled preparation of purified Co 3 O 4 nanoparticles with narrow size distributions adjustable in the range between 3-13 nm. The particles exhibit excellent colloidal stability. Their dispersibility in diverse organic solvents further facilitates processing ( i.e. ligand exchange) and opens exciting perspectives for controlled self-assembly of the largely isometric primary particles into mesoscale structures. In view of potential applications, functional properties including absorption characteristics and electrocatalytic activity were probed by UV-Vis spectroscopy and cyclic voltammetry, respectively. In these experiments, low amounts of dispersed Co 3 O 4 particles demonstrate strong light absorbance across the entire visible range and immobilized nanoparticles exhibit a comparably low overpotential towards the oxygen evolution reaction in electrocatalytic water splitting.
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