Maghemite γ-Fe2O3 Nanoparticles Research Articles

Functionalized maghemite nanoparticles for enhanced adsorption of uranium from simulated wastewater and magnetic harvesting

Maghemite (γ-Fe2O3) nanoparticles (MNPs) were functionalized with 3-aminopropyltriethoxysilane (APTES) to give APTES@Fe2O3 (AMNP) which was then reacted with diethylenetriamine-pentaacetic acid (DTPA) to give a nanohybrid DTPA-APTES@Fe2O3 (DAMNP). Nano-isothermal titration calorimetry shows that DTPA complexation with uranyl ions in water is exothermic and has a stoichiometry of two DTPA to three uranyl ions. Density functional theory calculations indicate the possibility of several complexes between DTPA and UO22+ with different stoichiometries. Interactions between uranyl ions and DAMNP functional groups are revealed by X-photoelectron and Fourier transform infrared spectroscopies. Spherical aberration-corrected Scanning Transmission Electron Microscopy visualizes uranium on the particle surface. Adsorbent performance metrics were evaluated by batch adsorption studies under different conditions of pH, initial uranium concentration and contact time, and the results expressed in terms of equilibrium adsorption capacities (qe) and partition coefficients (PC). By either criterion, performance increases from MNP to AMNP to DAMNP, with the maximum uptake at pH 5.5 in all cases: MNP, qe = 63 mg g−1, PC = 127 mg g−1 mM−1; AMNP, qe = 165 mg g−1, PC = 584 mg g−1 mM−1; DAMNP, qe = 249 mg g−1, PC = 2318 mg g−1 mM−1 (at 25 °C; initial U concentration 0.63 mM; 5 mg adsorbent in 10 mL of solution; contact time, 3 h). The pH maximum is related to the predominance of mono- and di-cationic uranium species. Uptake by DAMNPs follows a pseudo-first-order or pseudo-second-order kinetic model and fits a variety of adsorption models. The maximum adsorption capacity for DAMNPs is higher than for other functionalized magnetic nanohybrids. This adsorbent can be regenerated and recycled for at least 10 cycles with less than 10% loss in activity, and shows high selectivity. These findings suggest that DAMNP could be a promising adsorbent for the recovery of uranium from nuclear wastewaters.

Movement of giant lipid vesicles induced by millimeter wave radiation change when they contain magnetic nanoparticles.

Superparamagnetic iron oxide nanoparticles are used in a rapidly expanding number of research and practical applications in biotechnology and biomedicine. Recent developments in iron oxide nanoparticle design and understanding of nanoparticle membrane interactions have led to applications in magnetically triggered, liposome delivery vehicles with controlled structure. Here we study the effect of external physical stimuli-such as millimeter wave radiation-on the induced movement of giant lipid vesicles in suspension containing or not containing iron oxide maghemite (γ-Fe2O3) nanoparticles (MNPs). To increase our understanding of this phenomenon, we used a new microscope image-based analysis to reveal millimeter wave (MMW)-induced effects on the movement of the vesicles. We found that in the lipid vesicles not containing MNPs, an exposure to MMW induced collective reorientation of vesicle motion occurring at the onset of MMW switch "on." Instead, no marked changes in the movements of lipid vesicles containing MNPs were observed at the onset of first MMW switch on, but, importantly, by examining the course followed; once the vesicles are already irradiated, a directional motion of vesicles was induced. The latter vesicles were characterized by a planar motion, absence of gravitational effects, and having trajectories spanning a range of deflection angles narrower than vesicles not containing MNPs. An explanation for this observed delayed response could be attributed to the possible interaction of MNPs with components of lipid membrane that, influencing, e.g., phospholipids density and membrane stiffening, ultimately leads to change vesicle movement.

Formation of magnetoliposomes using self-assembling 1,4-dihydropyridine derivative and maghemite γ-Fe2O3 nanoparticles

This work demonstrates studies of ferromagnetic nanoparticle functionalization by a lipid-like compound, cationic pyridine amphiphile derived from 1,4-dihydropyridine, 1,1'-{[3,5-bis(dodecyloxycarbonyl)-4-phenyl-1,4-dihydropyridine-2,6-diyl]dimethanediyl}dipyridinium dibromide, and determination of optimal conditions for the production of magnetoliposomes. The following methodologies, such as sonication, spontaneous swelling, and reverse-phase evaporation, were used for the preparation of liposomes. Ferrofluid containing γ-Fe2O3 nanoparticles with a positively charged surface was used for the preparation of magnetoliposomes. The obtained soft matter objects were studied by optical microscopy, transmission electron microscopy, and dynamic light scattering techniques. The optimal conditions for the production of magnetoliposomes were found by spontaneous swelling and reverse-phase evaporation methods using ferrofluid with positively charged γ-Fe2O3 nanoparticles and cationic 1,4-dihydropyridine derivative.

Formation, characterization and magnetic properties of maghemite γ-Fe2O3 nanoparticles in borate glasses

A new type of nanocomposite materials based on maghemite, γ-Fe2O3, nanoparticles dispersed in borate glasses co-doped with low contents of iron together with the larger radius element combinations: Y and Bi, or Sm and Pb, or Y and Pb is studied. Nanoparticles arise as a result of heat treatment of the glasses which gives them properties characteristic of magnetically ordered substances. Transmission electron microscopy and XRD show that only one magnetic phase, namely γ-Fe2O3 nanoparticles, occurs in glasses subjected to the thermal treatment at 540°C during 24h independently on the doping element nature. At the same time doping element and their concentrations ratio in every combination affect the particles average size and glass magnetic properties, such as magnetization temperature dependences, Faraday rotation value and electron magnetic resonance spectrum characteristics.

Multifunctional hybrid silica nanoparticles based on [Mo6Br14]2− phosphorescent nanosized clusters, magnetic γ-Fe2O3 and plasmonic gold nanoparticles

We report on the synthesis, characterization and photophysical study of new luminescent and magnetic hybrid silica nanoparticles. Our method is based on the co-encapsulation of single maghemite γ-Fe2O3 nanoparticles and luminescent molybdenum cluster units [Mo6Bri8Bra6]2− through a water-in-oil (W/O) microemulsion technique. The as-prepared core–shell [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles (45–53nm) possess a single magnetic core (6, 10.5 or 15nm) and the cluster units are dispersed in the entire volume of the silica sphere. The [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles have a perfect spherical shape with a good monodispersity and they display red and near-infrared (NIR) emission in water under UV excitation, whose intensity depends on the magnetic core size. The hybrid nanoparticles have been characterized by transmission electron microscopy (TEM), high annular angular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), UV–Vis–NIR spectroscopy and magnetometer SQUID analysis. Small gold nanoparticles were successfully nucleated at the surface of the hybrid silica nanoparticles in order to add plasmonic properties.

Magnetically responsive polypyrrole nanotubes using Ce(III)-stabilized maghemitenanoparticles

Nanocomposites (NCs) that are made magnetically responsive in controlled conditionsattract continuing interest for their added magnetic properties. In this study, we report onthe preparation and full characterization of a multifunctional NC composed of magneticγ-Fe2O3 nanoparticles (NPs) covalently attached to the surface of polyaminated (polyNH2) poly(2,6-di-pyrrol-1-yl-hexanoic acid) (pDPL) nanotubes(NTs). Such a hybrid conducting polymer iron oxide maghemiteγ-Fe2O3@pDPL NC built specifically on covalent bonding has never been reported. The maghemiteγ-Fe2O3 NPs were prepared using an innovative ultrasound-assistedCe3 + doping process, resulting in polycarboxylation of the NP surface useful for control ofaggregation and derivatization of functionality. The second component of the NC, i.e. polyNH2-modified pDPL NTs, was prepared from an acid functional pyrrolespecies followed by amine modification. The resulting innovativeγ-Fe2O3@pDPL NC can be viewed as a multifunctional nanomaterial since itpossesses both types of derivatization, i.e. polyCOOH (NPs) andpolyNH2 (NTs) combined with magnetic responsivity.

Hydrolysis and amine-capping in a glycol solvent as a route to soluble maghemite gamma-Fe2O3 nanoparticles.

The preparation of capped metal oxide nanoparticles through the hydrolysis of metal salts is made arduous by the difficulty of dissolving long organic chain capping agents in water; by performing the reaction in propylene glycol under reflux, instead of water, we are able to hydrolyse FeCl3 in the presence of n-octylamine to obtain (repeatedly) soluble, monodisperse approximately 5 nm gamma-Fe2O3 particles that display a tendency to aggregate into superlattices.

A solvothermal route to capped nanoparticles of γ-Fe2O3 and CoFe2O4

The decomposition of single or multiple transition metal cupferron complexes in organic solvents under solvothermal conditions and in the presence of long chain amines yields the corresponding oxide nanoparticles. The examples presented here are maghemite γ-Fe2O3 nanoparticles from an FeIII–cupferron complex and spinel CoFe2O4 nanoparticles starting from CoII–cupferron complex and FeIII–cupferron complex taken in suitable proportions. The nanoparticles are capped with n-octylamine or n-dodecylamine. The presence of amine in the reaction is found to be essential for the formation of the product. The magnetic behavior of pressed pellets of these nanoparticles is presented.