Size and Surface Effects in the Ultrafast Dynamics of Strongly Cooperative Spin-Crossover Nanoparticles

Identifier:  imarina:9392496

Handle: https://hdl.handle.net/20.500.11797/imarina9392496

Authors:  Haddock, TN; Delgado, T; Alías-Rodríguez, M; de de Graaf, C; Enachescu, C; van der Veen, RM

Abstract:
Cooperative photoinduced switching of molecular materials at the nanoscale is still in its infancy. Strongly cooperative spin-crossover nanomaterials are arguably the best prototypes of photomagnetic and volume-changing materials that can be manipulated by short pulses of light. Open questions remain regarding their non-equilibrium dynamics upon light excitation and the role of cooperative elastic interactions in nanoscale systems that are characterized by large surface/volume ratios. Femtosecond-resolved broadband spectroscopy is performed on nanorods of the strongly cooperative Fe-triazole, which undergoes a reversible low-spin to high-spin (HS) phase transition approximate to 360 K. Supported by density functional theory and mechano-elastic Monte Carlo simulations, a marked difference is observed in the photoswitching dynamics at the surface of the nanoparticles compared with the core. Surprisingly, under low excitation (