Pulsed laser ablation and incubation of nickel, iron and tungsten in liquids and air

Incubation effects in the nanosecond laser ablation of metals exhibit a strong dependence on the thermal and mechanical properties of both the target material and the background gas or liquid. The incubation in air is controlled mainly by thermal properties such as the heat of vaporization. In liquid, the correlation of the incubation and the ultimate tensile stress of the metals suggests that incubation may be related to the mechanical impact on the solid material by the cavitation bubble collapse, causing accumulation of voids and cracks in the subsurface region of the ablation craters. At high ultimate tensile stress, however, the low sensitivity to the environment suggests that the mechanical impact is likely to play a negligible role in the incubation. Finally, the correlation between the incubation and the carbon content of alcoholic liquids may be explained by an absorptivity increase of the cavity surfaces due to carbonaceous deposits generated by laser-induced pyrolysis, or by the mechanical impact of long-living bubbles at higher dynamic viscosity of liquids

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed

Ex vivo assessment of polyol coated-iron oxide nanoparticles for MRI diagnosis applications: toxicological and MRI contrast enhancement effects

et al.Polyol synthesis is a promising method to obtain directly pharmaceutical grade colloidal dispersion of superparamagnetic iron oxide nanoparticles (SPIONs). Here, we study the biocompatibility and performance as T2-MRI contrast agents (CAs) of high quality magnetic colloidal dispersions (average hydrodynamic aggregate diameter of 16-27 nm) consisting of polyol-synthesized SPIONs (5 nm in mean particle size) coated with triethylene glycol (TEG) chains (TEG-SPIONs), which were subsequently functionalized to carboxyl-terminated meso-2-3-dimercaptosuccinic acid (DMSA) coated-iron oxide nanoparticles (DMSA-SPIONs). Standard MTT assays on HeLa, U87MG, and HepG2 cells revealed that colloidal dispersions of TEG-coated iron oxide nanoparticles did not induce any loss of cell viability after 3 days incubation with dose concentrations below 50 μg Fe/ml. However, after these nanoparticles were functionalized with DMSA molecules, an increase on their cytotoxicity was observed, so that particles bearing free terminal carboxyl groups on their surface were not cytotoxic only at low concentrations (<10 μg Fe/ml). Moreover, cell uptake assays on HeLa and U87MG and hemolysis tests have demonstrated that TEG-SPIONs and DMSA-SPIONs were well internalized by the cells and did not induce any adverse effect on the red blood cells at the tested concentrations. Finally, in vitro relaxivity measurements and post mortem MRI studies in mice indicated that both types of coated-iron oxide nanoparticles produced higher negative T2-MRI contrast enhancement than that measured for a similar commercial T2-MRI CAs consisting in dextran-coated ultra-small iron oxide nanoparticles (Ferumoxtran-10). In conclusion, the above attributes make both types of as synthesized coated-iron oxide nanoparticles, but especially DMSA-SPIONs, promising candidates as T2-MRI CAs for nanoparticle-enhanced MRI diagnosis applications. © 2014 Springer Science+Business Media.This research was supported by ARAID Foundation (Regional Government of Aragon), and ‘‘Centro de Investigación Biomédica en Red—Bioingeniería, Biomateriales y Nanomedicina’’ (CIBER-BBN), through the intramural research projects IMAFEN (2008–2009) NANOMAG (2008–2009), PROGLIO (2010–2011), and PROGLIO2 (2012–2013). OBM thanks the financial support from the ‘‘Ramón y Cajal Program’’ of the Spanish Ministry of Economy and Competitiveness (MINECO). AGR would like to thank the funding of Spanish Ministerio de Educación, through Programa Nacional de Movilidad de Recursos Humanos 2011.Peer Reviewe

A facile synthetic route for the preparation of superparamagnetic iron oxide nanorods and nanorices with tunable surface functionality

A study was conducted to demonstrate a facile synthetic route for the preparation of superparamagnetic iron oxide nanorods and nanorices with tunable surface functionalities, comprising inorganic coating of different types. Some of the different coatings used in the study, include alumina and zirconia. The study demonstrated that alumina is a suitable coating for studying the dependence of the cellular uptake of nanoparticles, as a function of the surface charge. It was found that alumina has an isoelectric point around 9 and is positively charged at physiological pH. It was also observed that the ;preferential uptake of particles, with positively charged surfaces by negatively charged membranes occurs, as a result of alumina being positively charged at physiological pH.Peer Reviewe

Laser pyrolysis preparation of SiO2-coated magnetic nanoparticles for biomedical applications

Proceedings of the Joint European Magnetic Symposia (JEMS' 04)The encapsulation of magnetic particles into silica has been achieved efficiently in a single and continuous process by laser-induced pyrolysis of ferrocene and TEOS aerosols. This process results in rather homogeneous iron/magnetite particles smaller than 10 nm in diameter surrounded by a SiO2 coating of about 20 nm. Interactions between the metal core and the passivation layer dominates the coercivity at low temperature in these systems

Laser‐assisted synthesis of colloidal FeWxOy and Fe/FexOy nanoparticles in wWater and ethanol

Homogeneous polycrystalline FexOy nanoparticles were generated by ablation of iron targets in water by nanosecond laser pulses at 532 nm. In ethanol, crystalline core‐shell Fe/FexOy structures with size medians around 20 nm were produced. The ablation of FeWxOy targets in water resulted in crystalline hollow shells and homogeneous FeWxOy nanoparticles. In contrast, amorphous core‐shell FeWxOy nanoparticles with a median size of 17 nm were produced in ethanol. The size distribution of both the FexOy and the FeWxOy particles showed a slight dependence on fluence and pulse number. This may be related to primary and secondary ablation and modification mechanisms.Partial financial support by the H2020 Action MSCA‐IF 656908‐NIMBLIS‐ESR is acknowledged. Further partial funding came from the National Science Foundation through Grant CMMI‐1301298, and the MAT2015‐67354‐R project of the Spanish Ministry of Economy and Competitiveness (MINECO).Peer reviewe

Core-shell iron-iron oxide nanoparticles synthesized by laser-induced pyrolysis

Passivated iron nanoparticles (10-30 nm) have been synthesized by laser pyrolysis of a mixture of iron pentacarbonyl and ethylene vapors followed by controlled oxidation. The nanoparticles show a well-constructed iron-iron oxide core-shell structure, in which the thickness and nature (structure similar to maghemite, γ-Fe2O3) of the shell is found to be independent of the initial conditions. On the other hand, the composition of the core is found to change with the particle size from the α-Fe structure to a highly disordered Fe phase (probably containing C atoms in its structure). The dependence of the magnetic properties on the particle size, iron oxide fraction, and temperature was also investigated. In the case of smaller particles, the magnetic data indicate the existence at low temperature of a large exchange anisotropy field, the magnitude of which increases with decreasing temperature in correspondence with the freezing of magnetic moments in the oxide shell. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.Peer Reviewe

The growth of cobalt oxides on HOPG and SiO2 surfaces: A comparative study

The growth of cobalt oxides by reactive thermal evaporation of metallic cobalt on highly oriented pyrolytic graphite (HOPG) and SiO2 (X cut quartz surface), in an oxygen atmosphere at room temperature, has been chemically and morphologically studied by means of X-ray photoelectron spectroscopy and atomic force microscopy. The chemical analysis, which also includes cluster calculations, reveals that for the early deposition stages on both substrates, Co2 + species are stabilized at the surface up to a coverage which depends on the substrate. Further coverages lead to the formation of the spinel oxide Co3O4. The results are discussed in terms of the dependence of the surface energy on the size of the CoO deposited moieties. On the other hand, it has been found that the initial way of growth of cobalt oxides on HOPG is of Stranski-Krastanov mode whereas on SiO2 the growth is of Volmer-Weber mode. The differences in the growth morphology have been discussed in terms of the surface diffusivity of the CoO deposits on the substrates. © 2014 Elsevier B.V.This investigation has been funded by the MINECO of Spain through the CONSOLIDER projects CSD2008-00023 and CSD2007-41 and projects ENE2010-21198-C04-04 and MAT2011-26534. One of the authors (O.B.M.) thanks the financial support from the “Ramón y Cajal” Program of MINECO.Peer Reviewe

Nanopatterning on highly oriented pyrolytic graphite surfaces promoted by cobalt oxides

In this work we present a method to produce nanopatterning on graphite surfaces via carbon gasification reaction, with oxygen as reactant gas, catalyzed by cobalt oxides (CoO) instead of metallic cobalt nanoparticles as most usual methods. This reaction is produced at 400 °C, temperature which is much lower than that used in conventional methods. The chemical analysis of the cobalt species have been performed with X-ray photoemission and X-ray absorption spectroscopies, which are supported by theoretical cluster model and multiplet calculations of the spectra. The changes in the morphology of the surfaces after each process have been followed by atomic force microscopy. The defects produced after the gas reaction on the graphite surface have also been analyzed by combining atomic force microscopy and confocal micro-Raman spectroscopy. The presence of oxygen in the initial CoO wetting-layer has been identified as responsible of the weakening of the graphite bonds at the surface.This investigation has been funded by the MINECO of Spain through the CONSOLIDER CSD2008-00023, AYA2012-39832-C02-02, FIS2013-40667-P and MAT2011-26534 projects and the Comunidad de Madrid through the NANOFRONTMAG-CM P2013/MIT2850 project. Authors R.J.O.M. and M.A. thank the financial support of Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil). One of the authors (O.B.M.) thanks the financial support from the “Ramón y Cajal” Program of MINECO

Continuous production of inorganic magnetic nanocomposites for biomedical applications by laser pyrolysis

International audienceMagnetic composites of Fe-based nanoparticles encapsulated in carbon/silica (C/SiO2@Fe) or carbon (C@Fe) matrices were prepared by laser-induced pyrolysis of aerosols. The powders were dispersed in aqueous solutions at pH 7 resulting in biocompatible colloidal dispersions with a high resistance to biodegradation. Structural and magnetic properties and the suitability of aqueous dispersions as contrast agent for MRI were analyzed. The results of these characterizations and the NMR relaxivity data are very encouraging for application of laser pyrolysis products in the field of living tissues