Morphological Studies of Composite Spin Crossover@SiO2 Nanoparticles.

Yue Zan,Azzedine Bousseksou,Lionel Salmon

doi:10.3390/nano11123169

Abstract

Spin crossover (SCO) iron (II) 1,2,4-triazole-based coordination compounds in the form of composite SCO@SiO2 nanoparticles were prepared using a reverse microemulsion technique. The thickness of the silica shell and the morphology of the as obtained core@shell nanoparticles were studied by modifying the polar phase/surfactant ratio (ω), as well as the quantity and the insertion phase (organic, aqueous and micellar phases) of the tetraethylorthosilicate (TEOS) precursor, the quantity of ammonia and the reaction temperature. The morphology of the nanoparticles was monitored by transmission electron microscopy (TEM/HRTEM) while their composition probed by combined elemental analyses, thermogravimetry and EDX analyses. We report that not only the particle size can be controlled but also the size of the silica shell, allowing for interesting perspectives in post-synthetic modification of the shell. The evolution of the spin crossover properties associated with the change in morphology was investigated by variable temperature optical and magnetic measurements.

Highlights

Since the first report in 2006 concerning the synthesis of spin crossover nanoparticles by a reverse micelle method [1], numerous other homogeneous and heterogeneous media approaches including the use of polymers, soft and hard templates, microfluidic, spray drying and flow chemistry have been developed [2]
In this paper we report on the effect of the experimental conditions of reverse micelle syntheses on the thickness of the silica shell and the morphology of the as-obtained
[Fe(H-trz)2]BF4 @SiO2 nanoparticles with lengths ranging from 250 to nm modifying well-known experimental parameters such assuch the temperature and theand waterwhile modifying well-known experimental parameters as the temperature the to-surfactant ratio

Summary

Introduction

Crossover@SiO2 Nanoparticles.Since the first report in 2006 concerning the synthesis of spin crossover nanoparticles by a reverse micelle method [1], numerous other homogeneous and heterogeneous media approaches including the use of polymers, soft and hard templates, microfluidic, spray drying and flow chemistry have been developed [2]. The reverse micelles technique is presently the more developed one for obtaining such nano-objects because it is easy to implement, and it is the technique of choice to obtain various sizes and shapes of nanoparticles in a controlled manner for the same compound, permitting the fine study of the relationship between size and spin crossover properties [3,4,5,6,7,8]. This method has been used to obtain hybrid or nanocomposite materials based on spin crossover complexes [2]. According to this strategy, fluorescent agents as well as metallic nanoparticles have been grafted onto the silica shell to obtain a useful

Methods

Results

Conclusion