Photoswitchable 11 nm CsCoFe Prussian Blue Analogue Nanocrystals with High Relaxation Temperature
Résumé
Photoswitchable 11 nm nanocrystals with the coordination network Cs{Co[Fe(CN)6]} were obtained using a template-free method. The nanocrystals were recovered from the colloidal solutions as solid materials surrounded by cetyltrimethylammonium (CTA) cations or embedded in the organic polymer polyvinylpyrrolidone (PVP). Complementary magnetic, spectroscopic, and structural techniques, including EPR spectroscopy, reveal a majority (∼70%) of the low-spin and photoactive diamagnetic CoIIIFeII pairs located in the core of the nanocrystals and a mixture of CoIIFeII and CoIIFeIII species present mainly within the shell of the objects. While bulk compounds with similar vacancy concentration do not exhibit noticeable photoinduced charge transfer, the observed photoactivity of the nanocrystals is ascribed to their nanometric size. The relaxation temperature of the photoinduced state shifts upward by ∼55 K when PVP is replaced by CTA. This is ascribed to the larger rigidity of the dense CsCoFe_CTA material, whose metastable state is lower than that for CsCoFe_PVP, leading to a larger relaxation energy barrier and, therefore, to a higher relaxation temperature.
Mots clés
Charge transfer
Cobalt alloys
Cobalt metallography
Electron spin resonance spectroscopy
Iron alloys
Nanocrystals
Organic polymers
Sols
Ternary alloys
Cetyltrimethylammonium
Coordination networks
Photoinduced charge transfer
Polyvinyl pyrrolidone
Prussian blue analogues
Relaxation temperature
Structural techniques
Vacancy concentration
Iron metallography
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Trinh et al-2020-Photoswitchable 11 nm CsCoFe Prussian Blue.pdf (4.46 Mo)
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