Magnetoelectrically driven catalytic degradation of organics

Here, we report the catalytic degradation of organic compounds by exploiting the magnetoelectric (ME) nature of cobalt ferrite-bismuth ferrite (CFO-BFO) core-shell nanoparticles. The combination of magnetostrictive CFO with the multiferroic BFO gives rise to a magnetoelectric engine that purifies water under wireless magnetic fields via advanced oxidation processes, without involvement of any sacrificial molecules or co-catalysts. Magnetostrictive CoFe2O4 nanoparticles are fabricated using hydrothermal synthesis, followed by sol-gel synthesis to create the multiferroic BiFeO3 shell. We perform theoretical modeling to study the magnetic field induced polarization on the surface of magnetoelectric nanoparticles. The results obtained from these simulations are consistent with the experimental findings of the piezo-force microscopy analysis, where we observe changes in the piezoresponse of the nanoparticles under magnetic fields. Next, we investigate the magnetoelectric effect induced catalytic degradation of organic pollutants under AC magnetic fields and obtained 97% removal efficiency for synthetic dyes and over 85% removal efficiency for routinely used pharmaceuticals. Additionally, we perform trapping experiments to elucidate the mechanism behind the magnetic field induced catalytic degradation of organic pollutants by using scavengers for each of the reactive species. Our results indicate that hydroxyl and superoxide radicals are the main reactive species in the magnetoelectrically induced catalytic degradation of organic compounds

Enhanced catalytic degradation of organic pollutants by multi-stimuli activated multiferroic nanoarchitectures

Smart catalysts that can simultaneously utilize multiple energy sources will have a significant positive impact on the inefficiencies of conventional environmental remediation approaches, and will address their high energy demands. In this work, we have manufactured multiferroic magnetoelectric photocatalysts that can be simultaneously activated using multiple energy sources for the degradation of organic pollutants. The catalysts are composed of CoFe2O4@BiFeO3 (CFO@BFO) nanooctahedrons (NOs), CFO@BFO nanocubes (NCs), and CFO@BFO nanowires (NWs), and were successful in harnessing energy from three different energy sources, including UV-vis light, acoustically mediated mechanical vibrations and magnetic fields. The CFO@BFO NOs displayed the most enhanced degradation, reaching 93%, 96%, and 99% degradation of RhB dye within 1 h under light, ultrasound, and magnetic fields, respectively. When these energy sources were used simultaneously, significantly increased reaction rates were observed compared to the single-energy source stimulation. Results of radical trapping experiments indicate that radical species i.e., OH· and O2·- play a dominant role in catalytic degradation of organic pollutant, RhB, under all three stimuli. These results will contribute significantly to the development of new environmental technologies that are highly versatile in nature and able to adapt to changing environments to deliver efficient environmental remediation.ISSN:1998-0000ISSN:1998-012

Simultaneous Localization and Actuation Using Electromagnetic Navigation Systems

ISSN:1552-3098ISSN:1042-296XISSN:1941-046

Magnetically Guided Catheters, Micro- and Nanorobots for Spinal Cord Stimulation

Spinal cord stimulation (SCS) is an established treatment for refractory pain syndromes and has recently been applied to improve locomotion. Several technical challenges are faced by surgeons during SCS lead implantation, particularly in the confined dorsal epidural spaces in patients with spinal degenerative disease, scarring and while targeting challenging structures such as the dorsal root ganglion. Magnetic navigation systems (MNS) represent a novel technology that uses externally placed magnets to precisely steer tethered and untethered devices. This innovation offers several benefits for SCS electrode placement, including enhanced navigation control during tip placement, and the ability to position and reposition the lead in an outpatient setting. Here, we describe the challenges of SCS implant surgery and how MNS can be used to overcome these hurdles. In addition to tethered electrode steering, we discuss the navigation of untethered micro- and nanorobots for wireless and remote neuromodulation. The use of these small-scale devices can potentially change the current standard of practice by omitting the need for electrode and pulse generator implantation or replacement. Open questions include whether small-scale robots can generate an electrical field sufficient to activate neuronal tissue, as well as testing precise navigation, placement, anchoring, and biodegradation of micro- and nanorobots in the in vivo environment

Piezoelectrically Enhanced Photocatalysis with BiFeO 3 Nanostructures for Efficient Water Remediation

Designing new catalysts that can efficiently utilize multiple energy sources can contribute to solving the current challenges of environmental remediation and increasing energy demands. In this work, we fabricated single-crystalline BiFeO3 (BFO) nanosheets and nanowires that can successfully harness visible light and mechanical vibrations and utilize them for degradation of organic pollutants. Under visible light both BFO nanostructures displayed a relatively slow reaction rate. However, under piezocatalysis both nanosheets and nanowires exhibited higher reaction rates in comparison with photocatalytic degradation. When both solar light and mechanical vibrations were used simultaneously, the reaction rates were elevated even further, with the BFO nanowires degrading 97% of RhB dye within 1 hr (k-value 0.058 min−1). The enhanced degradation under mechanical vibrations can be attributed to the promotion of charge separation caused by the internal piezoelectric field of BFO. BFO nanowires also exhibited good reusability and versatility toward degrading four different organic pollutants.ISSN:2589-004

On-the-fly catalytic degradation of organic pollutants using magneto-photoresponsive bacteria-templated microcleaners

Increasing accumulation of highly persistent and non-biodegradable organic pollutants in our fresh water sources imposes a threat to human health. Designing novel catalytic materials that can efficiently harness energy from their surroundings to degrade such problematic pollutants is essential. In this work, we fabricated core–shell microhelical robots composed of iron oxide@titanium dioxide (Fe3O4@TiO2) for UV-visible light driven degradation of organic pollutants in a cost-effective manner. Bio-templating and sol–gel synthesis were employed for a simplified approach to batch-fabricate magnetic photocatalysts. These hybrid microrobots removed 97% of RhB dye from contaminated water in 75 minutes using UV-visible light (k-value of 0.047 min−1). Furthermore, when photocatalytic degradation was performed under continuous magnetic field driven propulsion, 99% of RhB dye degraded in 40 minutes with a k-value of 0.108 min−1. We also observed a strong correlation between the hybrid microhelices' swimming characteristics and their subsequent photocatalytic degradation efficiency. These results were further corroborated using COMSOL simulations.ISSN:2050-7488ISSN:2050-749

Piezoelectrically enhanced photocatalysis with BiFeO3 nanostructures for efficient water remediation

Designing new catalysts that can efficiently utilize multiple energy sources can contribute to solving the current challenges of environmental remediation and increasing energy demands. In this work, we fabricated single-crystalline BiFeO3 (BFO) nanosheets and nanowires that can successfully harness visible light and mechanical vibrations and utilize them for degradation of organic pollutants. Under visible light both BFO nanostructures displayed a relatively slow reaction rate. However, under piezocatalysis both nanosheets and nanowires exhibited higher reaction rates in comparison with photocatalytic degradation. When both solar light and mechanical vibrations were used simultaneously, the reaction rates were elevated even further, with the BFO nanowires degrading 97% of RhB dye within 1 hr (k-value 0.058 min−1). The enhanced degradation under mechanical vibrations can be attributed to the promotion of charge separation caused by the internal piezoelectric field of BFO. BFO nanowires also exhibited good reusability and versatility toward degrading four different organic pollutants

Magnetoelectric 3D scaffolds for enhanced bone cell proliferation

Regulation of cellular functions by an exogenous and non-invasive approach has the means of revolutionizing the field of tissue engineering. In this direction, use of electric fields has garnered significant interest due to its positive influence on cell adhesion, proliferation, and differentiation. Recently, this has been achieved by placing electrodes in direct contact with cells, or through a non-contact approach by inducing deformation of piezoelectric membranes. In this work, we have developed 3D magnetoelectric inverse opal scaffolds that can generate localized electric fields upon the application of magnetic fields. These scaffolds were composed of biodegradable poly(l-lactic acid), and cobalt ferrite@bismuth ferrite magnetoelectric nanoparticles and were designed to mimic the natural micro-environment of cancellous bone by endowing them with piezoelectric properties and porosity. The effect of magnetic field induced electric stimulation on the proliferation of human-derived MG63 osteoblast cells, a model for primary osteoblast cells, was investigated on 2D membranes and 3D scaffolds by applying a magnetic field of 13 mT at 1.1 kHz. During this study, a 134% increase in cell proliferation was achieved on stimulated 3D scaffolds in comparison to non-stimulated ones, and in case of 2D membranes, we have obtained an increase of 43% of stimulated 2D membranes in comparison to non-stimulated ones. These findings showcase the importance of designing scaffolds with 3D characteristics that provide a suitable micro-environment for host cells. The results obtained from this work further demonstrate the beneficial influence that the magnetoelectric effect has on regulating cellular functions and draws light on the possibility of exploiting this effect for tissue engineering and regenerative medicine in the future

Magnetoelectric effect in hydrogen harvesting: magnetic field as a trigger of catalytic reactions

Magnetic fields have been regarded as an additional stimulus for electro- and photocatalytic reactions, but not as a direct trigger for catalytic processes. Multiferroic/magnetoelectric materials, whose electrical polarization and surface charges can be magnetically altered, are especially suitable for triggering and control of catalytic reactions solely with magnetic fields. Here, we demonstrate that magnetic fields can be employed as an independent input energy source for hydrogen harvesting by means of the magnetoelectric effect. Composite multiferroic CoFe2O4-BiFeO3 core-shell nanoparticles act as catalysts for the hydrogen evolution reaction (HER) that is triggered when an alternating magnetic field is applied to an aqueous dispersion of the magnetoelectric nanocatalysts. Based on density functional calculations, we propose that the hydrogen evolution is driven by changes in the ferroelectric polarization direction of BiFeO3 caused by the magnetoelectric coupling. We believe our findings will open new avenues towards magnetically induced renewable energy harvesting