3 research outputs found
Multiplying Magnetic Hyperthermia Response by Nanoparticle Assembling
The
oriented attachment of magnetic nanoparticles is recognized
as an important pathway in the magnetic-hyperthermia cancer treatment
roadmap, thus, understanding the physical origin of their enhanced
heating properties is a crucial task for the development of optimized
application schemes. Here, we present a detailed theoretical analysis
of the hysteresis losses in dipolar-coupled magnetic nanoparticle
assemblies as a function of both the geometry and length of the array,
and of the orientation of the particlesā magnetic anisotropy.
Our results suggest that the chain-like arrangement biomimicking magnetotactic
bacteria has the superior heating performance, increasing more than
5 times in comparison with the randomly distributed system when aligned
with the magnetic field. The size of the chains and the anisotropy
of the particles can be correlated with the applied magnetic field
in order to have optimum conditions for heat dissipation. Our experimental
calorimetrical measurements performed in aqueous and agar gel suspensions
of 44 nm magnetite nanoparticles at different densities, and oriented
in a magnetic field, unambiguously demonstrate the important role
of chain alignment on the heating efficiency. In low agar viscosity,
similar to those of common biological media, the initial orientation
of the chains plays a minor role in the enhanced heating capacity
while at high agar viscosity, chains aligned along the applied magnetic
field show the maximum heating. This knowledge opens new perspectives
for improved handling of magnetic hyperthermia agents, an alternative
to conventional cancer therapies
Tetravalent Manganese Feroxyhyte: A Novel Nanoadsorbent Equally Selective for As(III) and As(V) Removal from Drinking Water
The
development of a single-phase Fe/Mn oxy-hydroxide (Ī“-Fe<sub>0.76</sub>Mn<sub>0.24</sub>OOH), highly efficient at adsorbing both
AsĀ(III) and AsĀ(V), is reported. Its synthesis involves the coprecipitation
of FeSO<sub>4</sub> and KMnO<sub>4</sub> in a kilogram-scale continuous
process, in acidic and strongly oxidizing environments. The produced
material was identified as a manganese feroxyhyte in which tetravalent
manganese is homogeneously distributed into the crystal unit, whereas
a second-order hollow spherical morphology is favored. According to
this structuration, the oxy-hydroxide maintains the high adsorption
capacity for AsĀ(V) of a single Fe oxy-hydroxide combined with enhanced
AsĀ(III) removal based on the oxidizing mediation of MnĀ(IV). Ion-exchange
between arsenic species and sulfates as well as the strongly positive
surface charge further facilitate arsenic adsorption. Batch adsorption
tests performed in natural-like water indicate that MnĀ(IV)-feroxyhyte
can remove 11.7 Ī¼g AsĀ(V)/mg and 6.7 Ī¼g AsĀ(III)/mg at equilibrium
pH 7, before residual concentration overcomes the regulation limit
of 10 Ī¼g As/L for drinking water. The improved efficiency of
this material, its low cost, and the possibility for scaling-up its
production to industry indicate the high practical impact and environmental
importance of this novel adsorbent
Fe<sub>3</sub>O<sub>4</sub>@NiFe<sub><i>x</i></sub>O<sub><i>y</i></sub> Nanoparticles with Enhanced Electrocatalytic Properties for Oxygen Evolution in Carbonate Electrolyte
The
design and engineering of earth-abundant catalysts that are both cost-effective
and highly active for water splitting are crucial challenges in a
number of energy conversion and storage technologies. In this direction,
herein we report the synthesis of Fe<sub>3</sub>O<sub>4</sub>@NiFe<sub><i>x</i></sub>O<sub><i>y</i></sub> coreāshell
nanoheterostructures and the characterization of their electrocatalytic
performance toward the oxygen evolution reaction (OER). Such nanoparticles
(NPs) were produced by a two-step synthesis procedure involving the
colloidal synthesis of Fe<sub>3</sub>O<sub>4</sub> nanocubes with
a defective shell and the posterior diffusion of nickel cations within
this defective shell. Fe<sub>3</sub>O<sub>4</sub>@NiFe<sub><i>x</i></sub>O<sub><i>y</i></sub> NPs were subsequently
spin-coated over ITO-covered glass and their electrocatalytic activity
toward water oxidation in carbonate electrolyte was characterized.
Fe<sub>3</sub>O<sub>4</sub>@NiFe<sub><i>x</i></sub>O<sub><i>y</i></sub> catalysts reached current densities above
1 mA/cm<sup>2</sup> with a 410 mV overpotential and Tafel slopes of
48 mV/dec, which is among the best electrocatalytic performances reported
in carbonate electrolyte