Time-Resolved Study of the Photoswitching of Gold Nanorods Coated with a Spin-Crossover Compound Shell

Abstract

We investigate the spin-state photoswitching process in Au@SCO nanohybrids made of gold nanorods coated by a spin crossover (SCO) shell of polymeric triazole based Fe(II) complexes of [Fe(Htrz) 2 trz] (BF 4 ). Our research is performed exciting our samples with near-infrared quasi-continuous wave or nanosecond pulse, tunable from visible to near-infrared range. Time-resolved experiments ranging from millisecond down to nanosecond time-scales reveal the dynamics during the spin-state transition.Upon excitation, the thermal photoswitching of the sample happens within hundreds of milliseconds for quasi-continuous wave excitation. It happens within tens of nanoseconds for a nanosecond pulse. Compared to the SCO [Fe(Htrz) 2 trz] (BF 4 ) nanoparticles powder, the peak power of quasi-continuous wave or fluence of the nanosecond laser required to induce the spin state transition in the nanohybrid is reduced. A 1 simple model that well accounts for the experimental results is proposed. We show that the experiments performed using nanosecond pulses make it possible to analyze the photo-switching within individual nanoparticles whereas the ones performed with quasi-continuous wave excitation reveal the photo-switching within an ensemble of nanoparticles.

Bistable Spin‐Crossover Nanoparticles for Molecular Electronics

“…In this context, a photoconversion of the 55% of metallic centers from low-spin to high-spin upon light irradiation was achieved by Chastanet et al, in gold nanorods surrounded by a [Fe(Htrz) 2 (trz)](BF 4 ) shell. [60][61][62] Subsequently, we improved this result by employing gold nanostars as core, achieving a 60% photoconversion with light irradiation two orders of magnitude lower in intensity. [59] In Table 2, some of the most relevant SCO nanodevices are presented.…”

Rational Direct Synthesis of RbMnFe Nanoparticles (RbMnFe = RbxMn[Fe(CN)6](2+x)/3·nH2O Prussian Blue Analogue)

“…Among the numerous switchable systems, metal-to-metal charge transfer (MMCT) assemblies and spin crossover (SCO) molecules are intrinsically multifunctional candidates for devices, as they present a (possibly hysteretic) change between two electronic configurations under external stimuli (temperature, light, pressure, and electric field), leading to changes in their optical, electrical, magnetic, and mechanical properties. Optical control can be driven in the fs-ns time scale, particularly within the hysteresis region, , on nanosized systems, and even on individual nanoparticles, with very low photoswitching energy …”