Search

In this study, magnetic-optical properties of Zn1−xCoxO NCs were modulated with x-content. The optical, structural, morphological, and magnetic properties were investigated by optical absorption (OA), fluorescence (FL), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and electronic paramagnetic resonance (EPR). The XRD and Raman results confirm the growth of Zn1−xCoxO NCs, with x greater than 1.0 having occurred for the formation of the nanocomposite (Co-doped ZnO/ZnCo2O4). The formation of the nanocomposite allows new and exciting optical and magnetic properties. SEM images show inhibition in ZnO nanorod growth with Co-content and formation of ZnCo2O4 NCs. OA and FL spectra have changed with x-content in Zn1−xCoxO NCs. These changes are strongly related to the symmetric environment of the Co2+ ions within ZnO NCs and the formation of ZnCo2O4 NCs. A linear dependence of FL intensity was observed with the x-content in the red-green region. The symmetric environment and the nanocomposite formation also alter the magnetic properties confirmed by EPR. Therefore, Zn1−xCoxO NCs can be a material platform suitable for photonic devices, magnetic-optical devices, or spintronics.

Bayesian inference was used as a new approach to calculate of rare earth (RE) ion spectroscopic parameters within the Judd−Ofelt theory using the Li2O-B2O3-Al2O3 glass system doped with Nd2O3 and TiO2. This system was synthesized by the fusion method, and the physical properties of the as-synthesized material were investigated. Optical absorption, photoluminescence, micro-Raman, mass density, refractive index, and radiative lifetime calcuations were performed. We investigated the effects of crystal field changes on Nd3+-ions caused due to co-doping with increasing TiO2 content. We observed that co-doping with TiO2 altered the radiative transition rates A(J,J′), favored symmetry enhancement around the Nd3+-ions, and promoted the onset of vibrational modes, contributed to the attenuation of O-H bonds, and substantially increased the spectroscopic quality, χ.

Comparison of the Mossbauer spectra of the as-prepared native iron oxide nanoparticles (IONs) and the citrate-functionalized IONs demonstrates differences in the spectral shapes at room temperature and variations of the 57Fe hyperfine parameters at 80 K. The observed differences are claimed to result from capping the IONs with citrate, thus decreasing the particle-particle interaction while promoting interaction of the outer atomic layers of the IONs with the surface molecular coating.

This study reports on the synthesis and the physical characterization of a ternary boron-rich (B-rich) lithium–boron–aluminum (LBA: Li2O–B2O3–Al2O3) vitreous system successfully doped with increasing Nd2O3 content (xNd2O3:LBA) in the range 0 ≤ x ≤ 5 wt %. The as-produced samples were investigated using optical absorption, photoluminescence emission, Raman spectroscopy, and differential thermal analysis. The Judd–Ofelt (JO) theory was used to assess the intensity parameters (Ω λ ), transition probabilities (A(J, J')), branch ratios (β), emission cross-sections (σ), quantum efficiencies (Y), experimental (τ exp ) and calculated (τ rad ) radiative lifetimes, and the spectroscopic quality values (χ = Ω 4/Ω 6) as a function of the nominal Nd2O3 doping content. Over the range of our investigation (0 ≤ x ≤ 5 wt %), we found that the Ω 2 and Ω 6JO parameters monotonically increased from 0.17 to 1.26 × 10−20 and from 1.19 to 1.84 × 10−20, respectively. In contrast, over the same range of nominal Nd2O3 doping content we found that the Ω 4 JO parameter decreased monotonically from 4.12 to 2.05 × 1 0−20. Although the τ exp values increased at the low end of nominal Nd2O3 content (up to 2.5 wt %), nonradiative energy transfer mechanisms (e.g., energy migration, cross-relaxation, and losses from networked phonons and O–H vibrational modes) governed the process at the high end of the nominal Nd2O3 content. A competition mechanism was proposed to explain the observed behavior in the 4F3/2 ⟶ 4IJ’transition lifetime for hosted Nd3+ ions.

In this study Surface Enhanced Raman Spectroscopy (SERS) data recorded from mouse mammary glands cancer cells (4T1 cell line) was used to assess information regarding differences between control, death and viable cells after Photodynamic Therapy (PDT) treatment. The treatment used nanoemulsions (NE/PS) loaded with different chloroaluminumphthalocyanine (ClAlP) photosensitizer (PS) contents (5 and 10 µmol × L−1) and illumination (660 nm wavelength) at 10 J × cm−2 (10 minutes). The SERS data revealed significant molecular alterations in proteins and lipids due to the PDT treatment. Principal Component Analysis (PCA) was applied to analyze the data recorded. Three-dimensional and well reproductive PCA scatter plots were obtained, revealing that two clusters of dead cells were well separated from one another and from control cluster. Overlap between two clusters of viable cells was observed, though well separated from control cluster. Moreover, the data analysis also pointed out necrosis as the main cell death mechanism induced by the PDT, in agreement with the literature. Finally, Raman modes peaking at 608 cm−1 (proteins) and 1231 cm−1 (lipids) can be selected for follow up of survival rate of neoplastic cells after PDT. We envisage that this finding is key to contribute to a quick development of quantitative infrared thermography imaging.

Study of maghemite nanoparticles, native and coated with DMSA as mag- netic fluid for biomedical applications, was carried out using Mossbauer spectroscopy with a high velocity resolution at 295 and 90 K. The obtained results demonstrated differences in Mossbauer hyperfine parameters for uncoated and DMSA-coated nanoparticles which were related to the interactions of DMSA molecules with Fe 3+ ions on maghemite nanoparticle's surface.

This paper reports on the synthesis of Zn1−x Mn x Te nanocrystals (NCs) (with 0 ≤ x ≤ 0.800) within a PZABP glass system (P2O5–ZnO–Al2O3–BaO–PbO) using the fusion method. The as-grown samples were investigated by optical absorption measurements, atomic force microscopy, X-ray diffraction, and Raman spectroscopy. The mean radius of the as-produced NCs (around R ≈ 2.2 nm) was well below the exciton Bohr radius of the bulk ZnTe (5.2 nm). All the characterization techniques employed in this report confirmed the successful inclusion of Mn2+ ions in the ZnTe-based NCs (Zn1−x Mn x Te NCs) up to the nominal solubility limit of x = 0.100. Above this solubility limit (around x = 0.100), one can observe the formation of MnO and α-MnO2 NCs, since the nucleation rate for the formation of these NCs is greater than that of Zn1−x Mn x Te NCs, at high x concentrations.

In this study we demonstrate the usefulness of the Photoacoustic Spectroscopy (PAS) in the investigation of copaiba oil obtained from Copaifera tree, located in a site within Rondonia State, Amazon region, Brazil. Pure copaiba oil sample was diluted in 98% ethanol providing 10 different samples at volume concentration in the range of 5 to 50% vv. The observed photoacoustic spectral features from pure copaiba oil and the corresponding diluted samples, in the 0.18 to 4.00 μm wavelength region, are discussed in terms of five distinct bands (C, S, L, K, and X bands). Photoacoustic peak intensity was investigated as a function of the copaiba oil concentration in the 5 to 50% v.v.

This paper describes how cobalt ferrite nanoparticles, suspended as ionic or biocompatible magnetic fluids, can be used as a platform to built complex nanosized magnetic materials, more specifically magnetic drug delivery systems. In particular, the paper is addressed to the discussion of the use of the Mossbauer spectroscopy as an extremely useful technique in supporting the investigation of key aspects related to the properties of the hosted magnetic nanosized particle. Example of the use of the Mossbauer spectroscopy in accessing information regarding the nanoparticle modification due to the empirical process which provides long term chemical stability is included in the paper.

Photoacoustic spectroscopy (PAS) was used to investigate samples produced from Baru (Dipteryx alata Vog.), a typical fruit from the Brazilian Cerrado, which is considered as a good source of nutrients. The photoacoustic (PA) spectra of samples prepared from Baru seeds present three different absorption bands in the wavelength range 0.3–1.0 μm, named Band-C, Band-S, and Band-L. We found that PAS can be useful for monitoring the strong absorption of visible light by Baru's seeds constituents mainly in the shorter wavelength measured range. This study is important from both agricultural and commercial point of view once it introduces PAS as a potential characterization technique allowing better control of fruit and seed selection, storage and transportation.

In this study we demonstrate the usefulness of the Photoacoustic Spectroscopy (PAS) in the investigation of water collected from a natural site located within the Amazon region, Brazil, during the wet to dry seasons transition (May/2006). The water samples were collected from different stages along a hydrologic pathway including precipitation water (Prec), groundwater (GW), through flow water (TF), overland flow water (OF), and stream flow water (SW). The observed photoacoustic spectral features, in the 0.3 to 1.0 μm wavelength region, fall within three distinct bands (C, S, and L). We found band-C, band-S and band-L occurring in the spectral range of 0.30 to 0.40 μm, 0.40 to 0.45 μm and 0.45 to 1.0 μm regions, respectively. The photoacoustic features shift peak positions and change intensities for all samples investigated, thus supporting the proposal of PAS as a useful technique to investigate water samples from natural environments.

In this study cobalt ferrite nanoparticles were synthesized in a macroporous styrene–divinylbenzene copolymer template. Aqueous solutions containing Fe3 + and Co2 + ions (2:1 ratio) were retained in the template’s pores. The metal ions were precipitated inside the template using alkaline solution. In order to improve nanophase crystallinity samples were treated under different conditions; in air atmosphere and in nitrogen atmosphere, at 150°C or 300°C, for 2 or 4 h. All materials were characterized by chemical analysis, infrared spectroscopy, X-ray diffraction, and Mossbauer spectroscopy. We found improvement of the nanoparticles’ crystallinity only after thermal treatments in air atmosphere whereas the polymer structure was modified only in air atmosphere and at higher temperature.

Magnetic characterization of maghemite nanoparticles dispersed in a polymeric template and treated under different chemical processes is reported in this work. Particle size estimated from magnetic measurements, DM ≈ 10 nm, for the free-surfactant sample, is consistent with values determined from XRD analysis and TEM images. The magnetic collapse of sextets towards a quadrupole doublet as the temperature is increased reveals the thermal relaxation of smaller ψ-Fe203 nanoparticles. Magnetic measurements show a strong irreversibility between ZFC and FC curves suggesting the occurrence of particle-particle interaction.

Transmission electron microscopy, X-ray diffraction and Mossbauer spectroscopy were used in the characterization of a nanocomposite containing magnetic nanoparticles dispersed in a glycolic acid-based template. Maghemite nanoparticles were identified as the iron oxide phase dispersed in the polymeric template. From the low-temperature Mossbauer data the amount of the iron-based, non-magnetic material at the nanoparticle surface was estimated as roughly one monolayer in thickness.

Mossbauer spectroscopy was used in this study to investigate magnetite-based nanocomposites, using mesoporous styrene-divinylbenzene (Sty-DVB) microspheres as the hosting template. The magnetite content was increased in the polymeric template by performing several in situ chemical reactions (one to six cycles) in the hosting material. We found the Mossbauer linewidth associated to site-A increasing with the relative increase of iron in site-A. The Mossbauer linewidth associated to site-B decreases with the relative decrease of iron in site-B. We explain our findings by assuming local change in the homogeneity associated to changes in the relative iron population in sites A and B.

Transmission electron microscopy (TEM), Mossbauer spectroscopy and magnetization measurements were used in the present study to investigate a non-aqueous iron-nitride-based magnetic fluid (MF) sample containing about 2 × 1016 particle/cm3. The TEM micrographs indicated spherical-shaped iron nitride nanoparticles with an average diameter of 12.3 nm and diameter dispersity of 0.14. The 77 K Mossbauer spectrum of the frozen MF sample indicated the presence of about 95% of the γ′-Fe4N phase, with a residual 5% of the ɛ-Fe4N phase. The temperature dependence of the magnetization was investigated under zero-field-cooled (ZFC) condition, in the temperature range of 4 to 165 K. The ZFC-data were curve-fitted using a new approach that takes into account the particle size distribution and the temperature dependence of the magnetocrystalline anisotropy, making the description of the experimental situation more realistic.

The present study provides a comparative analysis of the size dispersity of magnetic nanoparticles (MNPs) within magnetic fluids as obtained from atomic force microscopy (AFM) and transmission electron microscopy (TEM). Whereas the mean particle diameter obtained from the AFM data presented a reduction of about 34% as compared to the value obtained from the TEM data, the standard deviation obtained from the AFM data is twice the value found from the TEM data. Similarities and differences in the size dispersity parameters are discussed in terms of sample preparation and tip characteristics. A two-dimensional mode for the deposition of the MNPs on top of the mica substrate is discussed as well.

This review intends to summarize some of the results achieved in the development of magnetic nanoparticles coated with anionic ligands, specifically dimercaptosuccinic acid applied in the biomedical area. We describe synthetic routes used to produce iron oxide-based magnetic nanoparticles, subsequently coated with DMSA as well as functionalization strategies for specific purposes with polymers, antibodies, and cytokines. Finally, we have collected data on biological interactions of DMSA-coated nanoparticles in vitro and in vivo, in particular cell interaction process, pharmacokinetics, and biodistribution in different animal models and their promising applications in drug delivery, NMR imaging, hyperthermia, nanothermometry, magnetic separation, and bioremediation., AR holds a predoctoral fellowship from a CSIC-CITMA collaborative project (B01CU2009; ICMM, 2011–2014) and a short-term fellowship from CNPq (DTI-2; 383934/2013-3). This work was partially supported by the Spanish Ministry of Economy and Competitiveness (Project MAT2011-23641).

The parameters of the log‐normal size distribution of a MnFe2O4 ferrofluid powder sample have been determined by X‐ray diffraction. The mean blocking temperature was determined from the maximum of Xi . Mossbauer spectra at 4.2–300 K are interpreted by a new simple theory of superparamagnetism and taking a reduction of the internal magnetic field for small particles, a size dependence of the anisotropy constant, the size distribution and collective excitations into account.

Background: The increasing incidence of cancer and the search for more effective therapies with minimal collateral effects have prompted studies to find alternative new treatments. Among these, photodynamic therapy (PDT) has been proposed as a very promising new modality in cancer treatment with the lowest rates of side effects, revealing itself to be particularly successful when the photosensitizer is associated with nanoscaled carriers. This study aimed to design and develop a new formulation based on albumin nanospheres containing zinc-phthalocyanine tetrasulfonate (ZnPcS4-AN) for use in the PDT protocol and to investigate its antitumor activity in Swiss albino mice using the Ehrlich solid tumor as an experimental model for breast cancer. Methods: Ehrlich tumor’s volume, histopathology and morphometry were used to assess the efficacy of intratumoral injection of ZnPcS4-AN in containing tumor aggressiveness and promoting its regression, while the toxicity of possible treatments was assessed by animal weight, morphological analysis of the liver and kidneys, hemogram, and serum levels of total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (GGT), alkaline phosphatase, creatinine and urea. In order to evaluate the efficacy of PDT, groups of animals treated with intratumoral injection of doxorubicin (Dox) were also investigated. Results: Intratumoral injection of ZnPcS4-AN was found to be efficient in mediating PDT to refrain tumor aggressiveness and to induce its regression. Although tumor volume reduction was not significant, PDT induced a remarkable increase in the necrosis area seen in the tumor’s central region, as in other experimental groups, including tumor and Dox treated groups, but also in the tumor’s peripheral region. Further, PDT showed minimal adverse effects. Indeed, the use of ZnPcS4-AN in mediating PDT revealed anti-neoplastic activity similar to that obtained while using intratumoral Dox therapy. Conclusions: PDT mediated by the new formulation ZnPcS4-AN enhanced the inhibition of tumor growth while producing practically no adverse effects and thus emerges as a very promising nanotechnology-based strategy for solid cancer treatment.

In this study, we report on a new route of PEGylation of superparamagnetic iron oxide nanoparticles (SPIONs) by polycondensation reaction with carboxylate groups. Structural and magnetic characterizations were performed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The XRD confirmed the spinel structure with a crystallite average diameter in the range of 3.5–4.1 nm in good agreement with the average diameter obtained by TEM (4.60–4.97 nm). The TGA data indicate the presence of PEG attached onto the SPIONs’ surface. The SPIONs were superparamagnetic at room temperature with saturation magnetization (M S) from 36.7 to 54.1 emu/g. The colloidal stability of citrate- and PEG-coated SPIONs was evaluated by means of dynamic light scattering measurements as a function of pH, ionic strength, and nature of dispersion media (phosphate buffer and cell culture media). Our findings demonstrated that the PEG polymer chain length plays a key role in the coagulation behavior of the Mag-PEG suspensions. The excellent colloidal stability under the extreme conditions we evaluated, such as high ionic strength, pH near the isoelectric point, and cell culture media, revealed that suspensions comprising PEG-coated SPION, with PEG of molecular weight 600 and above, present steric stabilization attributed to the polymer chains attached onto the surface of SPIONs.

Structural and hyperfine properties of Er-doped SnO2 nanoparticles synthesized by a polymer precursor method are reported in this study. X-ray diffraction patterns of samples doped with erbium up to 10 mol % indicate the formation of the tetragonal rutile phase. The mean crystallite size shows a rapid decrease from ~12 nm for the undoped sample down to ~4 nm for the 10 mol % Er-doped sample. Structural changes as a function of the Er content, i.e., changes in the lattice constants, Sn–O bond distances and bond angles, strongly suggest the substitutional solution of Er3+ ions and the onset of oxygen vacancies throughout the SnO2 lattice. No dipolar-magnetic interaction is determined from the Mossbauer spectra which are well resolved by fitting with a distribution of electric-quadrupole doublets. Changes observed in the quadrupole splitting as a function of the Er content have been associated to the local strain induced by the cationic size mismatch and oxygen vacancies. This local strain affects the lattice contribution of the electric field gradient. The linear increase of the isomer shift is assigned to the enhancement of the oxygen vacancies as the Er content is increased. It is found that the oxygen vacancies provide with conduction electrons to the Er-doped SnO2 nanoparticulated system, therefore modifying its electronic properties.

In a complementary way, Raman and Mossbauer spectroscopy were successfully employed to assess the cations’ distribution among the tetrahedral (A-site) and octahedral (B-site) sites of nonosized ZnxMg1−xFe2O4 (0 ≤ x ≤ 1) cubic ferrite structure, synthesized by combustion reaction method. Nanoparticles with little change in size distributions, in the 40 nm (x = 0.0) up to 42 nm (x = 1.0) were obtained. Mossbauer data indicated that as the Zn-content (x) increases in the range 0 ≤ x ≤ 1, the Fe3+ ion monotonically increases (decreases) the A-site (B-site) occupancy up to nearly equal values at the highest end x value. Analysis of the Raman data, however, confirms that the three highest energy modes around 650, 668 and 710 cm−1 are assigned to Zn–O (B-site), Fe–O (A-site) and Mg–O (A-site) vibrations, respectively. Additionally, in agreement with the Mossbauer data, the Raman data show that as the Zn-content (x) increases in the range 0 ≤ x ≤ 1, the occupancy of A-sites by Mg2+ ions monotonically reduces with concomitant increase of A- and B-sites occupancy by Fe3+ and Zn2+ ions, respectively. Indeed, combination of the two sets of spectroscopic data (Raman and Mossbauer) provides an effective protocol for assessing the cations’ distribution within the crystal structure of nanosized quaternary cubic ferrite samples running for instance from \( \left[ {{\text{Fe}}_{0.42}^{3 + } {\text{Mg}}_{0.58}^{2 + } } \right]^{A} \left[ {{\text{Zn}}_{0.20}^{2 + } {\text{Mg}}_{0.22}^{2 + } {\text{Fe}}_{1.58}^{3 + } } \right]^{B} O_{4}^{2 - } \) at x = 0.2 up to \( \left[ {{\text{Fe}}_{1.0}^{3 + } } \right]^{A} \left[ {{\text{Zn}}_{0.60}^{2 + } {\text{Mg}}_{0.40}^{2 + } {\text{Fe}}_{1.0}^{3 + } } \right]^{B} {\text{O}}_{4}^{2 - } \) at x = 0.6.

The internal morphology and magnetic properties of layer-by-layer assembled nanofilms of polyaniline (PANI) and maghemite (γ-Fe2O3—7.5-nm diameter) were probed with cross-sectional transmission electron microscopy (TEM) and magnetization measurements (magnetic hysteresis loops, magnetization using zero-field cooled/field-cooled protocols, and ac magnetic susceptibility). Additionally, simulations of the as-produced samples were performed to assess both the nanofilm’s morphology and the corresponding magnetic signatures using the cell dynamic system (CDS) approach and Monte Carlo (MC) through the standard Metropolis algorithm, respectively. Fine control of the film thickness and average maghemite particle–particle within this magnetic structure was accomplished by varying the number of bilayers (PANI/γ-Fe2O3) deposited onto silicon substrates or through changing the concentration of the maghemite particles suspended within the colloidal dispersion sample used for film fabrication. PANI/γ-Fe2O3 nanofilms comprising 5, 10, 25 and 50 deposited bilayers displayed, respectively, blocking temperatures (T B) of 30, 35, 39 and 40 K and effective energy barriers (ΔE/k B) of 1.0 × 103, 2.3 × 103, 2.8 × 103 and 2.9 × 103 K. Simulation of magnetic nanofilms using the CDS model provided the internal morphology to carry on MC simulation of the magnetic properties of the system taking into account the particle–particle dipolar interaction. The simulated (using CDS) surface–surface particle distance of 0.5, 2.5 and 4.5 nm was obtained for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm, respectively. The simulated (using MC) T B values were 33.0, 30.2 and 29.5 K for nanofilms with thicknesses of 36.0, 33.9 and 27.1 nm, respectively. We found the experimental (TEM and magnetic measurements) and the simulated data (CDS and MC) in very good agreement, falling within the same range and displaying the same systematic trend. Our findings open up new perspectives for fabrication of magnetic nanofilms with pre-established (simulated) morphology and magnetic properties.