Femtosecond Measurements Of Size-Dependent Spin Crossover In FeII(pyz)Pt(CN)4 Nanocrystals

D. M. Sagar, Frederick G. Baddour, Patrick Konold, Joel Ullom, Daniel A. Ruddy, Justin C. Johnson, Ralph Jimenez

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12 Scopus Citations


We report a femtosecond time-resolved spectroscopic study of size-dependent dynamics in nanocrystals (NCs) of Fe(pyz)Pt(CN)4. We observe that smaller NCs (123 or 78 nm cross section and <25 nm thickness) exhibit signatures of spin crossover (SCO) with time constants of ∼5-10 ps whereas larger NCs with 375 nm cross section and 43 nm thickness exhibit a weaker SCO signature accompanied by strong spectral shifting on a ∼20 ps time scale. For the small NCs, the fast dynamics appear to result from thermal promotion of residual low-spin states to high-spin states following nonradiative decay, and the size dependence is postulated to arise from differing high-spin vs low-spin fractions in domains residing in strained surface regions. The SCO is less efficient in larger NCs owing to their larger size and hence lower residual LS/HS fractions. Our results suggest that size-dependent dynamics can be controlled by tuning surface energy in NCs with dimensions below ∼25 nm for use in energy harvesting, spin switching, and other applications.

Original languageAmerican English
Pages (from-to)148-153
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number1
StatePublished - 7 Jan 2016

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-64263


  • femtosecond
  • High spin
  • Low spin
  • nanocrystals
  • spin-crossover
  • time-resolved spectroscopy
  • transient absorption


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