Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid

TL;DR

This study demonstrates a method to synthesize ferrihydrite nanoparticles within a siloxane/poly(oxyethylene) hybrid matrix, with core size controlled by polymer molecular weight and iron content, revealing key factors for nanoparticle formation.

Contribution

It introduces a novel matrix-assisted synthesis approach for ferrihydrite nanoparticles in a hybrid organic-inorganic material, with tunable core size and controlled formation.

Findings

Nanoparticle core size (2-4 nm) is tunable by iron amount.

Polymer chain length influences nanoparticle anchoring and growth.

Controlled polymer molecular weight affects iron coordination and nucleation.

Abstract

Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is reported. The hybrid network (named di-ureasil) is composed of poly(oxyethylene) chains of different average polymer molecular weights grafted to siloxane domains by means of urea cross-linkages and accommodates ferrihydrite nanoparticles. Magnetic measurements, Fourier transform infrared and nuclear magnetic resonance spectroscopy reveal that the controlled modification of the polymer molecular weight allows the fine-tuning of the ability of the hybrid matrix to assist and promote iron coordination at the organic-inorganic interface and subsequent nucleation and growth of the ferrihydrite nanoparticles whose core size (2-4 nm) is tuned by the amount of iron incorporated. The polymer chain length, its arrangement and crystallinity, are key factors on the anchoring and formation of the ferrihydrite particles.