A lock-in-based method to examine the thermal signatures of magnetic nanoparticles in the liquid, solid and aggregated states

Abstract

We propose a new methodology based on lock-in thermography to study and quantify the heating power of magnetic nanoparticles. Superparamagnetic iron oxide nanoparticles exposed to a modulated alternating magnetic field were used as model materials to demonstrate the potency of the system. Both quantitative and qualitative information on their respective heating power was extracted at high thermal resolutions under increasingly complex conditions, including nanoparticles in the liquid, solid and aggregated states. Compared to conventional techniques, this approach offers a fast, sensitive and non-intrusive alternative to investigate multiple and dilute specimens simultaneously, which is essential for optimizing and accelerating screening procedures and comparative studies.

Lock-In Thermography as an Analytical Tool for Magnetic Nanoparticles: Measuring Heating Power and Magnetic Fields

“…44−46 In a previous article we reported the use of this approach in investigating SPIONs and their heating power. 47 In this paper, we describe the theory behind the LIT method and use the lock-in technique to evaluate field inhomogeneity and ILP field dependency. As a first step, we derived the analytical relationship between the SAR and the signal amplitude resulting from the lock-in demodulation.…”

“…51 We recently proposed the use of lock-in thermal imaging (LIT) instead. 47,52 In this technique, the amplitude of the magnetic field is harmonically modulated at a defined frequency, while the resulting sample temperature is processed according to the digital lock-in principle. 46 Because of the averaging nature of the technique, this approach allows high sensitivity.…”

Lock-in thermography as a rapid and reproducible thermal characterization method for magnetic nanoparticles

“…The output of the LIT demodulation is a 2D image whereby every pixel can be related to the initial heating slope value. While the heating efficiency and its dependence on nanoparticle size [16,[26][27][28] has been described on multiple occasions, the aim of this study was to investigate the minimum limit of detection as a factor of nanoparticle size and concentration.…”

“…All thermal measurements were performed with a previously described lock-in thermal imaging setup [16]. SPIONs were exposed to an alternating magnetic field generated by a commercial coil system (Magnetherm™ V1.5, nanoTherics Ltd) consisting of a water cooled coil, a laboratory power supply (EA-PS 3032-20B, EA Elektro Automatic) and a function generator (SFG-2004, GW Instek).…”

“…As a result, experimentally assessing heating power in every synthetic batch is highly recommended as a means of quality control. This work presents a comparative screening of the thermal SPION characteristics via LIT as an extension to Monnier et al [16]. The lower detection limit of the LIT system as a function of different particle diameters was investigated by measuring thermal properties at decreasing concentrations.…”