Evidence of the Core-Shell Structure of (Photo)magnetic CoFe Prussian Blue Analogue Nanoparticles and Peculiar Behavior of the Surface Species

Amélie Bordage; Robinson Moulin; Emiliano Fonda; Giulia Fornasieri; Eric Rivière; Anne Bleuzen

doi:10.1021/jacs.8b06147

Evidence of the Core-Shell Structure of (Photo)magnetic CoFe Prussian Blue Analogue Nanoparticles and Peculiar Behavior of the Surface Species

J Am Chem Soc. 2018 Aug 15;140(32):10332-10343. doi: 10.1021/jacs.8b06147. Epub 2018 Aug 7.

Authors

Amélie Bordage¹, Robinson Moulin¹, Emiliano Fonda², Giulia Fornasieri¹, Eric Rivière¹, Anne Bleuzen¹

Affiliations

¹ Institut de Chimie Moléculaire et des Matériaux d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay , 91405 Orsay , France.
² Synchrotron SOLEIL, L'Orme des Merisiers , St Aubin, BP 48 , 91192 Gif sur Yvette , France.

PMID: 30036473
DOI: 10.1021/jacs.8b06147

Abstract

We report on a comparative study of 5.5 nm (embedded in an ordered mesoporous silica matrix) and 100 nm (free) (photo)magnetic CoFe Prussian blue analogue (PBA) particles. Co and Fe K-edge X-ray absorption spectroscopy, X-ray diffraction, infrared spectroscopy, and magnetic measurements point out a core-shell structure of the particles in their ground states. In the 5.5 nm particles, the 11.5 Å thick shell is made of Fe(CN)₆ entities and Co^II-NC-Fe^III linkages departing from the geometry usually encountered in PBA, whatever the oxidation state (Co^IIFe^III or Co^IIIFe^II) of the CoFe pairs in the core. In the photomagnetic particles, the photomagnetic effect in the core of the particles is due to the same photoinduced Co^III(LS)Fe^II → Co^II(HS)Fe^III electron transfer whatever the size of the particles. The shell of the nanoparticles exhibits a peculiar photoinduced structural rearrangement, and the nanoparticles in their photoexcited state exhibit a superparamagnetic behavior.