The shift of colloidal impedance spectrum induced by the behavior of magnetic nanoparticles for potential application in biological detection

The variety of colloidal impedance can be a good indicator for nanoparticle -based sensing. Here a hollow solenoid was designed to measure the impedance spectrum from 40Hz to 110MHz of 1mL colloidal suspension. Colloidal dilution as well as conjugation of protein molecules was discovered to affect the position of specific peak on impedance spectrum. Moreover, we found both the real part and the imaginary part of AC impedance are crucial to reflect the behavioral variety of magnetic nanoparticles. Inductance fails to reflect the colloidal variety of adequate sensitivity. Our results will be valuable for developing novel point-of-care sensors.