Optical detection of magnetic nanoparticles in colloidal suspensions

•A simple route to characterize magnetic nanowire suspension is proposed.•Studied concentration as low as 2 ng/mL compares with more complex techniques.•Transmission and scattering modes allow full characterization of nanoparticles.

This study reports the change of light transmittance and light scattering dispersion by colloidal suspensions of magnetic nanoparticles. Optical changes were observed during the application of transversal magnetic fields to magnetic nanoparticles and nanowires at concentrations spanning from 20 µg/mL to 2 ng/mL. Results show that light scattering modulation is a simple, fast and inexpensive method for detection of magnetic nanoparticles at low concentrations. Frequency and time response of the optical modulation strongly depends on the geometry of the particles. In this regard, light transmittance and scattering measurements may prove useful in characterizing the morphology of suspended nanoparticles.