Imaging the Thermal Hysteresis of Single Spin-Crossover Nanoparticles

Abstract

The magnetic hysteresis property during the spin transition of spin-crossover (SCO) materials holds great promise for their applications in spin electronics, information storage, thermochromic, and nanophotonic devices. Existing studies often measured the averaged property of a bulk sample consisting of lots of individuals. When considering the significant heterogeneity among different individuals and the inevitable interparticle interactions, ensemble measurement not only blurred the structure−property relationship but also compromised the intrinsic hysteresis property and cyclability. Herein, we employed a recently developed surface plasmon resonance microscopy (SPRM) method to measure the thermal hysteresis curve of single isolated SCO nanoparticles. The thermal-induced spin transition was found to alter the optical contrast of single SCO nanoparticles, which was optically readout using SPRM in a quantitative, nonintrusive, and high-throughput manner. Single nanoparticle measurements revealed an intrinsic transition temperature that was independent of the temperature scan rate and superior stability after over 11 000 cycles of single SCO nanoparticles. Correlations between the hysteresis and the size and morphology of the same individuals further uncovered the significant nanoparticle-to-nanoparticle heterogeneity with implications for the size−property relationship and rational design of SCO materials with improved performance.

Photo‐Thermal Switching of Individual Plasmonically Activated Spin Crossover Nanoparticle Imaged by Ultrafast Transmission Electron Microscopy

“…Indeed, the knowledge of the exact volume change of a single SCO particle, its time scale upon photo-switching and its repeatability is of importance to understand the transport mechanisms, the occurrence of percolation effect (when the increase of volume induces nanoparticles to be in contact) and the fatigue of the devices. A recent study has shown the thermal hysteresis loop and LS to HS switching kinetic at the second time scale on individual nanoparticles through optical methods without providing information on the volume change 44 . In a previous investigation [45,46] , ultrafast TEM has already shown shape changes of SCO particles after laser irradiation, but details of this transformation and the influence of embedded plasmonically active particles remain unexplored.…”

Influence of the ultra-slow nucleation and growth dynamics on the room-temperature hysteresis of spin-crossover single crystals

“…Here we primarily refer to OM in bright-field, transmission mode, which probes local absorbance changes and allows for quantitative spatiotemporal studies of the spin-state transformation. It should be noted, however, that OM has been also used to probe refractive index and luminescence intensity changes, enabling to detect the spin transition in single SCO micro-nano-particles [6][7][8]).…”

The Localized Enhancement of Surface Plasmon Standing Waves Interacting with Single Nanoparticles

“…Single nanoparticles induce the localized enhancement of SPPs, and transforms to far field via leakage radiation for fast and label-free detection [5,6]. This method has been widely applied to chemistry and biology, such as bidirectional electron transfers visualizing [7], local activation energy barrier measuring [8], thermal hysteresis imaging of single spin-crossover nanoparticles [9], and single liposomes and virus detection [10][11][12].…”