Carlos de Oliveira Amorim

University of Aveiro | UA · Physics department & CICECO

We report polycrystalline BaTiO3 with cooperative magnetization behavior associated with the scarce presence of about 113 atomic ppm of Fe ions, clearly displaying magnetoelectric coupling with significant changes in magnetization (up toδM/M ≈32%) at the ferroelectric transitions. We find that Fe ions are segregated mostly at the interfaces between...

We present an ultra sensitive method to quantify the uptake of Hg by dithiocarbamate functionalized magnetic nanoparticles using radioactive tracker spectroscopy. We show a lower limit of detection of about 10fg L- 1, much lower than any other known techniques used to determine the uptake of Hg (about 10⁴ more sensitive), without the need of digest...

In this review we present examples of using radioactive isotopes as probes to study functional materials of fundamental and applied interest presenting colossal magnetoresistance, multiferroic effects, and magnetostructural coupling. Most of the works exploit the hyperfine properties, Electric Field Gradient (EFG) and Hyperfine Magnetic Field (HMF)...

In this study, multicore-like iron oxide (Fe3O4) and manganese ferrite (MnFe2O4) nanoparticles were synthesized and combined with nanogels based on chitosan and alginate to obtain a multimodal drug delivery system. The nanoparticles exhibited crystalline structures and displayed sizes of 20 ± 3 nm (Fe3O4) and 11 ± 2 nm (MnFe2O4). The Fe3O4 nanopart...

Ferrites have been widely studied for their use in the biomedical area, mostly due to their magnetic properties, which gives them the potential to be used in diagnostics, drug delivery, and in treatment with magnetic hyperthermia, for example. In this work, KFeO2 particles were synthesized with a proteic sol-gel method using powdered coconut water...

Rigid polyurethane foams (RPUFs) were synthesized using exclusively lignin-based polyol (LBP) obtained via the oxyalkylation of kraft lignin with propylene carbonate (PC). Using the design of experiments methodology combined with statistical analysis, the formulations were optimized to obtain a bio-based RPUF with low thermal conductivity and low a...

Superparamagnetic nanoparticles are of high interest for therapeutic applications. In this work, nanoparticles of calcium-doped manganese ferrites (CaxMn1−xFe2O4) functionalized with citrate were synthesized through thermally assisted oxidative precipitation in aqueous media. The method provided well dispersed aqueous suspensions of nanoparticles t...

Chemical analyses in the field using surface enhanced Raman scattering (SERS) protocols are expected to be part of several analytical procedures applied to water quality monitoring. To date, these endeavors have been supported by developments on SERS substrate nanofabrication, instrumentation portability and the internet of things. Here, we report...

The magnetocaloric effect of a given material is typically assessed through indirect estimates of the isothermal magnetic entropy change, ΔSM. While estimating the adiabatic temperature difference, ΔTad, is more relevant from the standpoint of refrigeration device engineering, this requires specialized experimental setups. We here present an approa...

Self-assembled short peptide-based gels are highly promising drug delivery systems. However, implementing a stimulus often requires screening different structures to obtain gels with suitable properties, and drugs might not be well encapsulated and/or cause undesirable effects on the gel's properties. To overcome this challenge, a new design approa...

Multifunctional lipid nanocarriers are a promising therapeutic approach for controlled drug release in cancer therapy. Combining the widely used liposome structure with magnetic nanoparticles in magnetoliposomes allies, the advantages of using liposomes include the possibility to magnetically guide, selectively accumulate, and magnetically control...

We examined the interaction between adatoms and graphene for Ag, Cd, In and Hg by density functional theory. We establish a relation between the binding energy and the electric-field gradient tensor (EFG) for each atom, which indicates that hyperfine interactions can be used to probe the binding and stability of adatoms on graphene. The EFG is also...

The search for magnetoelectric materials typically revolves around the struggle to make magnetic and ferroelectric orders simultaneously coexist in the same material, using either an intrinsic or an extrinsic/composite approach. Via ab initio calculations of a prototypical Fe/BaTiO3 interface, we predict that it is possible to tune the magnitude of...

In this study, magnetic nanosorbents consisting of magnetite (Fe3O4) cores coated with trimethyl chitosan (TMC)-silica hybrid shells were synthesized using a one-step coating procedure, and their application in the adsorptive removal of glyphosate (GLY) from artificial (ultra-pure) and real water (wastewater) samples was investigated. In synthetic...

The interest in understanding the interaction between graphene and atoms that are adsorbed on its surface (adatoms) spans a wide range of research fields and applications, for example, to controllably change the properties of graphene in electronic devices or to detect those changes in graphene-based sensors. We present a density functional theory...

Purpose: Nanotechnology applied to cancer treatment is a growing area of research in nanomedicine with magnetic nanoparticle-mediated anti-cancer drug delivery systems offering least possible side effects. To that end, both structural and chemical properties of commercial cobalt metal nanoparticles were studied using label-free confocal Raman spec...

The search for better and inexpensive magnetoelectric materials is now commonplace in solid state physics. An intense coupling between technologically viable electric and magnetic properties, embedded in a single material, is still an attribute greatly pursued by the scientific community. Following this line of thought, using DFT, the study of a sp...

The sensitivity and automation capabilities of modern superconducting quantum interference device (SQUID) magnetometers are currently unmatched. The measured moment values are, however, prone to deviations from their actual value due to geometric effects, namely sample size, shape, and radial offset. This is well known, and a knowledgeable operator...

Despite the promising pharmacological properties of curcumin, the transport and effective release of curcumin is still a challenge. The advances in functionalized nanocarriers for curcumin have also been motivated by the anticancer activity of this natural compound, aiming at targeted therapies. Here, stealth (aqueous and solid) magnetoliposomes co...

Mn-Zn ferrite nanoparticles have been subject of increasing research due to their desired properties for a wide range of applications. These properties include nanometer particle size control, tunable magnetic properties and low toxicity, providing these ferrites with the necessary requirements for cancer treatment via magnetic hyperthermia. Powder...

Heusler compounds are one of the most versatile families of materials, showing a wide range of technological applications. Here we present a pure in‐silico approach to fully study the physical properties of this promising family of materials as potential competitive magnetocalorics. The temperature and field dependence of the magnetization of three...

The usage of heterostructures of ferromagnetic and ferroelectric materials, as a means of achieving magnetoelectric multiferroic coupling, is a widely used approach which has been showing promising results. Along this line of thought, the deposition of BaTiO3 and Fe multilayers on LaAlO3, MgO, Al2O3 and SrTiO3 substrates using RF-magnetron sputteri...

Doxorubicin is one of the most widely used anti-cancer drugs, but side effects and selectivity problems create a demand for alternative drug delivery systems. Herein we describe a hybrid magnetic nanomaterial as a pH-dependent doxorubicin release carrier. This nanocarrier comprises magnetic iron oxide cores with a diameter of 10 nm, enveloped in a...

Supramolecular hydrogels are highly promising for biomedical materials owing to the wide array of properties that can be tailored and modulated. The combination with plasmonic/magnetic nanoparticles into plasmonic magnetogels further improve its potential in biomedical applications, through the combination of complementary strategies, such as photo...

Magnetic nanoparticles of zinc/calcium ferrite and decorated with silver were prepared by coprecipitation method. The obtained nanoparticles were characterized by UV/Visible absorption, XRD, TEM and SQUID. The mixed zinc/calcium ferrites exhibit an optical band gap of 1.78 eV. HR-TEM imaging showed rectangular nanoplate shapes with sizes of 10 ± 3...

Magnetoliposomes containing calcium ferrite (CaFe2O4) nanoparticles were developed and characterized for the first time. CaFe2O4 nanoparticles were covered by a lipid bilayer or entrapped in liposomes forming, respectively, solid or aqueous magnetoliposomes as nanocarriers for new antitumor drugs. The magnetic nanoparticles were characterized by UV...

Water contamination with antibiotics is a serious environmental threat. Ciprofloxacin (CIP) is one of the most frequently detected antibiotics in water. Herein, silica-based magnetic nanosorbents prepared using three seaweed polysaccharides, alginic acid, κ- and λ-carrageenan, were developed and evaluated in the uptake of ciprofloxacin. The sorbent...

Technology critical elements (TCE) are considered the vitamins of nowadays technology. Factors such as high demand, limited sources and geopolitical pressures, mining exploitation and its negative impact, point these elements as new emerging contaminants and highlight the importance for removal and recycling TCE from contaminated waters. This paper...

A series of first-row transition-metals combined with ethylenediamine tetraacetic acid (EDTA), as metal-based N,O-chelating ligands, at the surface of ferrite magnetic nanoparticles (MNPs) was prepared by a co-precipitation method. Those EDTA functionalized MNPs with general formula Fe3O4@EDTA-M2+ [M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (...

A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn²⁺ (1), Fe²⁺ (2), Co²⁺ (3), Ni²⁺ (4), Cu²⁺ (5) or Zn²⁺ (6)] were prepared by the co-precipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope - energy dispersive X-ray...

Since the discovery of giant magnetocaloric materials, it has become clear that magnetovolume coupling can lead to a large increase to a material's magnetocaloric effect, and so, to high-performance magnetic refrigerants. A simple and computationally inexpensive approach to gauge magnetovolume effects is via the Bean-Rodbell model, where a Curie te...