Use of ultramicroindentation to evaluate the degradation of sputtered coatings

The aim of this research work was to study the influence of chemical degradation on the mechanical properties of the non-degraded zones of sputtered W-N-Ti coatings. For this, an ultramicroindentation technique has been used before and after degradation, either on the zones between the pits in the corroded samples, or on the non-oxidised layers after removal of the top degraded layers. By using different applied loads it was possible to obtain results with and without the influence of the substrate. Thus, two types of results were obtained, those determined by using an empirical model, which eliminates the influence of the substrate, and those measured directly.Very small differences of less than 20% were obtained in the measured values before and after degradation, indicating that the non-degraded zones maintain their as-deposited mechanical properties.http://www.sciencedirect.com/science/article/B6TW4-3VGSFTN-Y/1/d6747ea11390bd13ea164c97933b791

Electrochemical vs antibacterial characterization of ZrCN-Ag coatings

Nowadays, antibacterial properties are becoming a viable feature to be introduced in biomaterials due to the possibility of modifying the materials' surface used in medical devices in a micro/nano metric scale. As a result, it is mandatory to understand the mechanisms of the antimicrobial agents currently used and their possible failures. In this work, the antibacterial activity of ZrCNAg films is studied, taking into consideration the ability of silver nanoparticles to be dissolved when embedded into a ceramic matrix. The study focuses on the silver release evaluated by glow discharge optical emission spectroscopy and the effect of the fluid composition on this release. The results revealed a very low silver release of the films, leading to non-antibacterial activity of such materials. The silver release was found to be dependent on the electrolyte composition. NaCl (8.9 g L? 1) showed the lowest spontaneously silver ionization, while introducing the sulfates in Hanks' balanced salt solution (HBSS) such ionization is increased; finally, the proteins incorporated to the (HBSS) showed a reduction of the silver release, which also explains the low ionization in the culture medium (tryptic soy broth) that contains high quantities of proteins.This research is partially sponsored by the FEDER funds through the program COMPETE - Programa Operacional Factores de Competitividade and by the Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT - PTDC/CTM/102853/2008 and in the framework of the Strategic Projects PEST-C/FIS/UI607/2011, PEST-C/EME/UI0285/2011 and SFRH/BD/80947/2011.This work has also been supported by the Ministerio de Ciencia e Innovacion of Spain through the Consolider-Ingenio 2010 Programme (CSD2008-00023) and through project RyC2007-0026

Optical properties and refractive index sensitivity of reactive sputtered oxide coatings with embedded Au clusters

The following article appeared in Journal of Applied Physics 115.6 (2014): 063512 and may be found at http://scitation.aip.org/content/aip/journal/jap/115/6/10.1063/1.4861136In the present study, nanocomposite coatings of Au clusters embedded in two different oxides, TiO2 and Al2O3, were synthesized using pulsed DC magnetron sputtering. The depositions were carried out in three steps, by depositing the oxide, the Au clusters, and again the oxide. The deposition time of the Au clusters was varied in order to achieve different cluster sizes, morphologies, and nanocomposite topographies. The structure, microstructure, morphology, and the optical properties of the coatings were studied. With the increase in Au content, red-shifted surface plasmon resonance (SPR) peaks with higher intensity and increased widths were observed due to changes in the metal clusters sizes and morphology and due to interparticle effects. In order to relate the peculiar SPR extinction bands with the different clusters shapes and distributions, a simulation of the optical properties of the nanocomposites was performed making use of the Renormalized Maxwell-Garnett approach. A theoretical study concerning the refractive index sensitivity was made in order to predict the optimal coatings parameters for sensing experiments. The increased surface area and the strong SPR extinction bands make these coatings suitable for gas sensing and also catalysis, albeit many other application fields can be envisaged.This research was sponsored by FEDER funds through the program COMPETE, Programa Operacional Factores de Competitividade, by national funds through FCT, Fundacao para a Ciencia e a Tecnologia, under the Projects PEst-C/EME/UI0285/2013 and CENTRO-07-0224-FEDER-002001 (Mais Centro SCT_2011_02_001_4637), and through the Spanish Ministry of Science and Innovation by Projects FUNCOAT CSD2008-00023 and AIB2010PT-00241. R.E.G. wishes also to thank the MCINN for the financial support within the Ramón y Cajal programme. Funding by the European Community through Project Nano4Color is gratefully acknowledged

Tunas off northwest Africa: The epipelagic diet of The Bigeye and Skipjack tunas

Tunas are among the most exploited top predators worldwide, with negative impacts on some of their stocks. Changes in their population abundance can impact marine food-webs and have the potential to alter entire ecosystems. To better understand the impacts of the exploitation of tuna stocks in the most critical habitats, basic knowledge on the diet of these species in each region is required. Here, we describe the diet of the two most fished tuna species in the archipelago of Madeira, the Bigeye tuna Thunnus obesus and the Skipjack tuna Katsuwonus pelamis, based on stomach contents analysis. To gain further insights into the diet, and also better assess the possible bias caused by the occurrence of live bait in stomachs, we compared tuna mercury values with those of two other predators with similar diets that are not directly targeted by fisheries, and with Bigeye and Skipjack tunas from other ocean basins. Bigeye tunas fed mostly on Atlantic chub mackerel Scomber colias and mackerel Trachurus sp., which together contributed with 85% of total prey weight. Only 7.5% of prey weight was constituted by mesopelagic prey, including myctophids and cephalopods. Skipjack tunas had an epipelagic diet (NF = 97%), with the Atlantic chub mackerel representing half of the total prey weight, despite Longspine snipefish Macroramphosus scolopax and Sand smelt Atherina sp. accounting for 62.9% of the total number of prey. There were interannual variations in diet likely linked to interannual pelagic community shifts. Bait did not bias the results of the stomach analysis of these tunas and bait species were observed to be part of the natural diet of both tuna species. Baseline data provided by this study should allow for more informed decisions for an efficient ecosystem-based fisheries management.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Ag+ release inhibition from ZrCN–Ag coatings by surface agglomeration mechanism : structural characterization

Published 17 July 2013New multifunctional materials based on well-established materials to which functional properties are added, such as antibacterial performance, have become a relevant research topic, in order to meet the requirements of today's technological advances. This paper reports the results of a detailed structural and chemical characterization study of ZrCN–Ag coatings produced by reactive magnetron sputtering, as well as the release of silver after immersion in a simulated body fluid (Hank's balanced salt solution), which mimic the material behaviour within the human body. The chemical composition was evaluated by electron probe microanalysis, x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy, whereas the structure was assessed by Raman spectroscopy and x-ray diffraction. The material exhibits a homogeneous distribution of the elements throughout the films, with a (C + N)/Zr ratio of around 1.3 and 15 at% of silver. A mixture of amorphous (a-C and CNx) and crystalline phases (ZrCN) was identified. In addition, the silver was detected to be released in less than 0.7% of the total silver in the films, occurring during the first two hours of immersion; no further release was evidenced after this period of time.This research is partially sponsored by FEDER funds through the program COMPETE-Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT-PTDC/CTM/102853/2008. This work has also been supported by the Ministerio de Ciencia e Innovacion of Spain through the Consolider-Ingenio 2010 programme (CSD2008-00023) and through project RyC2007-0026

Hydrocarbon toxicity towards hydrogenotrophic methanogens in oily waste streams

Hydrocarbon-containing wastes and wastewaters are produced worldwide by the activities of the oil and gas industry. Anaerobic digestion has the potential to treat these waste streams, while recovering part of its energy potential as biogas. However, hydrocarbons are toxic compounds that may inhibit the microbial processes, and particularly the methanogens. In this work, the toxicity of hexadecane (030 mM) towards pure cultures of hydrogenotrophic methanogens (Methanobacterium formicicum and Methanospirillum hungatei) was assessed. Significantly lower (p 30 mM for M. formicicum and M. hungatei, respectively, suggesting that toxic effects from aliphatic hydrocarbons towards hydrogenotrophic methanogens may not occur during anaerobic treatment. Hydrocarbon toxicity towards hydrogenotrophic methanogens was further assessed by incubating an anaerobic sludge with H2/CO2 in the presence of a complex mixture of hydrocarbons (provided by the addition of an oily sludge from a groundwater treatment system). Specific methanogenic activity from H2/CO2 decreased 1.2 times in the presence of the hydrocarbons, but a relatively high methane production (~30 mM) was still obtained in the assays containing the inoculum and the oily sludge (without H2/CO2), reinforcing the potential of anaerobic treatment systems for methane production from oily waste/wastewater.This research was funded by the Portuguese Foundation for Science and Technology (FCT) under the scope of project MORE (POCI-01-0145-FEDER-016575) and by the strategic funding of UIDB/04469/2020 unit.info:eu-repo/semantics/publishedVersio

An experimental and theoretical study on the crystal structure and elastic properties of Ta1-xOx coatings

The production of Ta1-xOx coatings has attracted a lot of attention due to their wide variety of industrial applications. Nonetheless, to properly control the functional properties of these coatings, a good understanding of their structural properties must be achieved. Ta1-xOx phases have structural similarities since they are formed by the distortion of the body centered cubic (bcc) Ta structure and, therefore, a clear and unequivocal identification of the crystalline phases is not trivial. In this regard, this work proposes a theoretical and experimental study to understand the evolution of the structural and the elastic properties of Ta-based coatings. The coatings were deposited by magnetron sputtering as a function of oxygen content and characterized by EPMA (electron probe microanalysis), XRD (X-ray diffraction), STEM (scanning transmission electron microscopy) and SAW (surface acoustic waves). The results demonstrate the formation of a bcc alpha-Ta phase in the non-reactive Ta coating, which transitions to a mixture of crystalline tantalum and tantalum oxide phases for low oxygen concentrations while amorphous phases are observed for high oxygen levels. Ab-initio calculations of different Ta-O phases are in good agreement with the experimental results and reveal that the oxygen addition to the metallic Ta phase, leads to a distortion of the Ta crystal structure, causing a decrease in density and an increase of the elastic constants.- This research is sponsored by FEDER funds through the program COMPETE -Programa Operacional Factores de Competitividade and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and UID/EMS/00285/2013 and with a PhD fellowship SFRH/BD/98199/2013. The authors also thank the financial support in the framework of ERA-SIINN/0004/2013 and PTDC/CTM-NAN/4242/2014 projects

Immobilization of streptavidin on a plasmonic Au-TiO2 thin film towards an LSPR biosensing platform

Optical biosensors based on localized surface plasmon resonance (LSPR) are the future of label-free detection methods. This work reports the development of plasmonic thin films, containing Au nanoparticles dispersed in a TiO2 matrix, as platforms for LSPR biosensors. Post-deposition treatments were employed, namely annealing at 400 °C, to develop an LSPR band, and Ar plasma, to improve the sensitivity of the Au-TiO2 thin film. Streptavidin and biotin conjugated with horseradish peroxidase (HRP) were chosen as the model receptor–analyte, to prove the efficiency of the immobilization method and to demonstrate the potential of the LSPR-based biosensor. The Au-TiO2 thin films were activated with O2 plasma, to promote the streptavidin immobilization as a biorecognition element, by increasing the surface hydrophilicity (contact angle drop to 7°). The interaction between biotin and the immobilized streptavidin was confirmed by the detection of HRP activity (average absorbance 1.9 ± 0.6), following a protocol based on enzyme-linked immunosorbent assay (ELISA). Furthermore, an LSPR wavelength shift was detectable (0.8 ± 0.1 nm), resulting from a plasmonic thin-film platform with a refractive index sensitivity estimated to be 33 nm/RIU. The detection of the analyte using these two different methods proves that the functionalization protocol was successful and the Au-TiO2 thin films have the potential to be used as an LSPR platform for label-free biosensors.Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020, UIDB/04050/2020, and UID/EMS/00285/2020, and by the projects NANO4BIO: POCI-01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/2017, and CO2Plasmon, with FCT reference EXPL/CTM-REF/0750/2021. Patrícia Pereira-Silva, Diana I. Meira, and Diogo Costa acknowledge FCT for their Ph.D. scholarships, 2020.08235.BD, SFRH/BD/143262/2019, and SFRH/BD/136279/2018, respectively. Augusto Costa-Barbosa also acknowledges FCT for his Ph.D. scholarships SFRH/BD/133513/2017 and COVID/BD/152169/2021. The authors would like to express their gratitude to Nuno P. Barradas (C2TN, University of Lisbon) and Eduardo Alves (IPFN, University of Lisbon) for RBS measurements and analysis