Self-Assembly of Au-Fe3O4 Hybrid Nanoparticles Using a Sol-Gel Pechini Method.

The Pechini method has been used as a synthetic route for obtaining self-assembling magnetic and plasmonic nanoparticles in hybrid silica nanostructures. This manuscript evaluates the influence of shaking conditions, reaction time, and pH on the size and morphology of the nanostructures produced. The characterization of the nanomaterials was carried out by transmission electron microscopy (TEM) to evaluate the coating and size of the nanomaterials, Fourier-transform infrared spectroscopy (FT-IR) transmission spectra to evaluate the presence of the different coatings, and thermogravimetric analysis (TGA) curves to determine the amount of coating. The results obtained show that the best conditions to obtain core-satellite nanostructures with homogeneous silica shells and controlled sizes (<200 nm) include the use of slightly alkaline media, the ultrasound activation of silica condensation, and reaction times of around 2 h. These findings represent an important framework to establish a new general approach for the click chemistry assembling of inorganic nanostructures.

Hybrid nanoparticles for magnetic and plasmonic hyperthermia.

The present manuscript reports the use of hybrid magneto-plasmonic nanoparticles (HMPNPs) based on iron oxide nanoparticles and Au nanorods as colloidal nanoheaters. The individual synthesis of the magnetic and plasmonic components allowed optimizing their features for heating performance separately, before they were hybridized. Besides, a detailed characterization and finite element simulations were carried out to explain the interaction effects observed between the phases of the HMPNPs. The study also analyzed the heating power of these nanostructures when they were excited with infrared light and AC magnetic fields, and compared this with the heating power of their plasmonic and magnetic components. In the latter case, the AC magnetization curves revealed that the magnetic dipolar interactions increase the amount of heat released by the hybrid nanostructures.

Synthesis of hybrid magneto-plasmonic nanoparticles with potential use in photoacoustic detection of circulating tumor cells.

This article describes a novel synthetic route to obtain hybrid nanostructures that combine the plasmonic properties of gold nanorods with the magnetic properties of iron oxide nanoparticles in a robust silica nanostructure. The silica matrix enhances the physico-chemical stability of the nanostructure and preserves its magneto-plasmonic properties by avoiding the interface between gold and iron oxide. In addition, the magneto-plasmonic features of the nanohybrids can be tuned due to the independent synthesis of each component. The magnetic and plasmonic properties of these nanostructures can potentially enhance the photoacoustic detection of circulating tumor cells. Graphical abstract Schematic presentation of a hybrid magneto-plasmonic nanoparticle with an Au@Fe3O4@SiO2 core-satellite-shell arrangement. The magnetic and plasmonic responses of this kind of nanostructure enable magnetic trapping and photoacoustic detection of circulating tumor cells.

A simple aqueous electrochemical method to synthesize TiO2 nanoparticles.

Here, a simple and rapid electrochemical approach to synthesize TiO2 nanoparticles in aqueous solution is reported. This method consists in the electro-oxidation of titanium foil in a tetrabutylammonium bromide aqueous solution, which acts as both an electrolyte and a surfactant. Amorphous TiO2 particles in the nanoscale (∼5 nm), well dispersed in aqueous solution, were directly formed by applying low current densities in a short reaction time. It was demonstrated that several experimental parameters influence the reaction yield; an increase in the current, temperature and reaction time augments the quantity of the obtained material. Then, the amorphous nanoparticles were completely crystallized into a pure anatase phase by thermal treatment under an air atmosphere as analyzed by X-ray diffraction and Raman spectroscopy. Besides, the size of the nanoparticles increased to approximately 12 nm in the calcination process. The band gap energies of the resulting TiO2 anatase nanoparticles were determined by diffuse reflectance measurements according to the Kubelka Munk theory, revealing low values between 2.95 and 3.10 eV. Therefore, the results indicate the success of this method to create TiO2 nanoparticles in aqueous medium with good optical properties.

Micromotors of MnO2 for the Recovery of Microplastics.

Plastics, primarily microplastics, are among the greatest pollutants in aquatic environments. Their removal and/or degradation in these environments are crucial to ensure an optimal future of these ecosystems. In this work, MnO2 particles were synthesized and characterized for the removal of polystyrene microplastics as a model. MnO2 catalyzes the peroxide reaction, resulting in the formation of oxygen bubbles that propel the pollutants to the surface, achieving removal efficiencies of up to 80%. To achieve this, hydrothermal synthesis was employed using various methods. Parameters such as MnO2, pH, microplastics, and H2O2 concentrations were varied to determine the optimal conditions for microplastics recovering. The ideal conditions for a low microplastic concentrations (10 mg L-1) are 0.2 g L-1 MnO2, 1.6% of H2O2 and 0.01 triton as a surfactant. In these conditions, the micromotors can recover approximately 80% of 300 nm sized polystyrene microplastic within 40 min.

Highly Efficient T2 Cobalt Ferrite Nanoparticles Vectorized for Internalization in Cancer Cells.

Uniform cobalt ferrite nanoparticles have been synthesized using an electrochemical synthesis method in aqueous media. Their colloidal, magnetic, and relaxometric properties have been analyzed. The novelty of this synthesis relies on the use of iron and cobalt foils as precursors, which assures the reproducibility of the iron and cobalt ratio in the structure. A stable and biocompatible targeting conjugate nanoparticle-folic acid (NP-FA) was developed that was capable of targeting FA receptor positivity in HeLa (human cervical cancer) cancer cells. The biocompatibility of NP-FA was assessed in vitro in HeLa cells using the MTT assay, and morphological analysis of the cytoskeleton was performed. A high level of NP-FA binding to HeLa cells was confirmed through qualitative in vitro targeting studies. A value of 479 Fe+Co mM-1s-1 of transverse relaxivity (r2) was obtained in colloidal suspension. In addition, in vitro analysis in HeLa cells also showed an important effect in negative T2 contrast. Therefore, the results show that NP-FA can be a potential biomaterial for use in bio medical trials, especially as a contrast agent in magnetic resonance imaging (MRI).

Improvement in Heavy Metal Removal from Wastewater Using an External Magnetic Inductor.

Magnetite nanoparticles (Fe3O4) of 12 ± 4 nm diameter are electrochemically synthesized for the adsorption and magnetic harvesting of Cr(VI) from contaminated simulated solutions. The removal of Cr(VI) from aqueous media follows pseudo-second-order kinetics. The adsorption efficiency is evaluated in three different scenarios. In standard conditions, i.e., at room temperature; in a thermal bath working at 60 °C, where the temperature could be considered homogeneous within the solution; and finally, under magnetic induction heating, while adjusting the frequency and magnetic field used to attain the same temperature as in the bath experiments. Two benefits of using a magnetic inductor are demonstrated. First, the removal efficiency is almost doubled in comparison to that of the room temperature experiments, and it is higher by 30% compared to that of the bath setup. At the same time as the adsorption occurs, a redox reaction occurs on the surface of the nanoparticles, and Cr(VI), the predominant species in the contaminated solution, is significantly reduced to Cr(III). Through X-ray photoelectron spectroscopy, it is shown that a greater reduction effect is achieved when working in induction conditions than at room temperature. This is the first time that this synergistic effect using magnetic induction heating has been demonstrated for heavy metal decontamination of wastewater.