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Abstract Over the past decade, magnetoelectric nanoparticles (MENPs) have proven effective in generating local electric fields in response to stimulation with a magnetic field. The applications of such nanoparticles are many and varied, with examples of prior research including use for on-demand drug release, wireless modulation and recording of neural activity, and organic dye degradation. This study investigates the potential for organic dye degradation to be used as a rapid and efficient screening tool to detect the magnetoelectric effect of MENPs, and how the results of such a test mirror the antiproliferative effect of said nanoparticles. Trypan blue was selected as an azo dye to test for dye degradation. Vials of the dye were treated with CoFe2O4@BaTiO3 core-shell MENPs of varying characteristics, both with and without concurrent 1-kHz 250-Oe magnetic stimulation. Dye degradation was measured using ultraviolet (UV)-vis spectroscopy. Dye degradation efficacy varied with varying nanoparticle synthesis parameters. As controls, nanoparticles of the same composition, but with an insignificant magnetoelectric effect, were used. SKOV-3 ovarian cancer cells were then treated with the same nanoparticles, and viability was measured with an adenosine triphosphate (ATP) assay. These measurements show a decrease in cell viability up to 60.3% of control (p = 0.0052), which mirrored the efficacy of dye degradation of up to 69.8% (p = 0.0037) in each of the particle variants, demonstrating the value of azo dye degradation as a simple screening test for MENPs, and showing the potential of MENPs used as wirelessly controlled nanodevices to allow targeted electric field-based treatments. 

An overview of the MENP biological applications discussed in this paper, which have the potential to form theranostic systems in the treatment of various diseases. 

Magnetoelectric coefficient values of above 5 and 2 V cm–1 Oe–1 in 20 nm CoFe2O4–BaTiO3 and NiFe2O4–BaTiO3 core–shell magnetoelectric nanoparticles were demonstrated. These colossal values, compared to 0.1 V cm–1 Oe–1 commonly reported for the 0–3 system, are attributed to (i) the heterostructural lattice-matched interface between the magnetostrictive core and the piezoelectric shell, confirmed through transmission electron microscopy, and (ii) in situ scanning tunneling microscopy nanoprobe-based ME characterization. The nanoprobe technique allows measurements of the ME effect at a single-nanoparticle level which avoids the charge leakage problem of traditional powder form measurements. The difference in the frequency dependence of the ME value between the two material systems is owed to the Ni-ferrite cores becoming superparamagnetic in the near-dc frequency range. The availability of novel nanostructures with colossal ME values promises to unlock many new applications ranging from energy-efficient information processing to nanomedicine and brain–machine interfaces. 

Abstract Paper has remained the world's most‐widely accessible information medium even as sustainable and reusable paper replacements have attracted increasing attention. Here, an ink‐free rewritable paper concept is developed that combines recent developments in photonic crystals, shape memory polymers, and electroactive polymers in a nanocomposite that matches the benefits of paper as a zero‐energy, long‐term data storage medium, but provides the additional advantage of rewritability. The rewritable paper consists of a ferroferric oxide‐carbon (Fe₃O₄@C) core–shell nanoparticle (NP)‐based photonic crystal embedded in a bistable electroactive polymer (BSEP). Electrical actuation induces large deformation in the z‐axis of the nanocomposite, creating distinct color change in the actuated area. This nanocomposite stores high fidelity color images without inks, the images remain stable after more than a year of storage in ambient conditions, and the stored images can then be rewritten over 500 times without degrading. A seven‐segment numerical display is also demonstrated.