How to characterize Magnetically Tunable Colloidal Photonic Crystals easily and quickly

Characterisation of Magnetically Tunable Colloidal Photonic Crystals Using the Zetasizer Nano

Introduction

Recently, a magnetically tuneable photonic crystal system has been developed by assembling highly charged Fe3O4 colloidal nanocrystal clusters (CNCs) [1,2]. They have attracted much attention because of their optoelectronic applications such as photonic components in tele-communication devices, lasers, sensors, drug delivery system (DDS) and MRI contrast agents [1,2].

Stabilized by the balance of attractive (magnetic) and repulsive(electrostatic) forces, the colloids form ordered structures along the direction of the external magnetic field with a regular interparticle spacing on the order of hundreds of nanometers. As a result, the solutions strongly diffract visible light [1,2]. CNCs can tune the diffraction wavelength throughout the entire visible spectrum by changing the strength of the external field [1,2]. The tuning range of the diffraction wavelength is related to the average size of the colloidal nanocrystal clusters. In general, crystals of large clusters (160-180 nm) preferentially diffract red light in a relatively weak magnetic field. Small clusters (60-100 nm) form ordered structures only when the magnetic field is strong and the crystals preferentially diffract blue light [1,2].