Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid

Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is reported. The hybrid network (named di-ureasil) is composed of poly(oxyethylene) chains of different average polymer molecular weights grafted to siloxane domains by means of urea cross-linkages and accommodates ferrihydrite nanoparticles. Magnetic measurements, Fourier transform infrared and nuclear magnetic resonance spectroscopy reveal that the controlled modification of the polymer molecular weight allows the fine-tuning of the ability of the hybrid matrix to assist and promote iron coordination at the organic-inorganic interface and subsequent nucleation and growth of the ferrihydrite nanoparticles whose core size (2-4 nm) is tuned by the amount of iron incorporated. The polymer chain length, its arrangement and crystallinity, are key factors on the anchoring and formation of the ferrihydrite particles.Comment: 7 pages, 6 figures. To be published in J. Mater. Che

Tailoring Ca3Co4O9 microstructure and performances using a transient liquid phase sintering additive

et al.A flexible, adaptable, economical and easily scalable processing route, allowing microstructural control, is presented. It involves classical solid state sintering method and addition of liquid promoting compound. Controlled porosity and high thermoelectric performance have been attained in CaCoO by KCO additions, drastically improving the sintering procedure. KCO behaves as transient liquid phase, providing microstructural benefits, vanishing during sintering. Electrical resistivity was improved by enhanced grains connectivity and growth. Significant increase in Seebeck coefficient at high temperatures has been produced while lattice thermal conductivity was unaffected. The best ZT value, estimated at 800°C, assuming the thermal conductivity value at 140°C, is 0.35 for 5wt.% KCO samples. These values are significantly higher than that obtained in highly-dense textured materials at the same temperature. The results suggest that this approach is very effective for preparing highly-performing CaCoO-based thermoelectric materials with relatively high porosity to control thermal conductivity.The authors wish to thank the MINECO-FEDER (MAT2013-46505-C3-1-R) and Gobierno de Aragón-Fondo Social Europeo (Research Groups T12 and T87) for financial support. This research was also partially supported by FCT, Portugal (IF/00302/2012 and PEst-C), project RECI/CTM-CER/0336/2012 co-financed by FEDER, QREN reference COMPETE: FCOMP-01-0124-FEDER-027465, and the projects financed by national funds through the FCT/MEC: UID/CTM/50025/2013, UID/CTM/50011/2013.Peer Reviewe

A luminescent molecular thermometer for long-term absolute temperature measurements at the nanoscale

El pdf del artículo es la versión post-print.A unique Eu3+/Tb3+ luminescent self-referencing nanothermometer allowing absolute measurements in the 10–350 K temperature range and sub-micrometer spatial resolution is reported (see Figure). It has up to 4.9%·K−1 temperature sensitivity and high photostability for long-term use. The combination of molecular thermometry, superparamagnetism and luminescence in a nanometric host matrix provides multifunctionality opening the way for new exciting applications.We acknowledge Fundação para a Ciência e a Tecnologia (FCT, Portugal), COMPETE and FEDER programs (PTDC/CTM/101324/2008) and Integrated Spanish-Portuguese Action PT2009–0131 for fi nancial support. The work in Zaragoza has been supported by the grants MAT2007–61621 and CONSOLIDER CSD2007–00010 from the Ministry of Education. CDSB (SFRH/BD/38472/2007) and PPL (SFRH/BPD/34365/2006) thank FCT for grants.Peer Reviewe

Giant Strain and Induced Ferroelectricity in Amorphous BaTiO3 Films under Poling

We report an effect of giant surface modification of a 5.6 nm thick BaTiO3 film grown on Si (100) substrate under poling by conductive tip of a scanning probe microscope (SPM). The surface can be locally elevated by about 9 nm under −20 V applied during scanning, resulting in the maximum strain of 160%. The threshold voltage for the surface modification is about 12 V. The modified topography is stable enough with time and slowly decays after poling with the rate ~0.02 nm/min. Strong vertical piezoresponse after poling is observed, too. Combined measurements by SPM and piezoresponse force microscopy (PFM) prove that the poled material develops high ferroelectric polarization that cannot be switched back even under an oppositely oriented electric field. The topography modification is hypothesized to be due to a strong Joule heating and concomitant interface reaction between underlying Si and BaTiO3. The top layer is supposed to become ferroelectric as a result of local crystallization of amorphous BaTiO3. This work opens up new possibilities to form nanoscale ferroelectric structures useful for various applications

Metal-sensitive and thermostable trypsin from the crevalle jack (Caranx hippos) pyloric caeca: purification and characterization

Background: Over the past decades, the economic development and world population growth has led to increased for food demand. Increasing the fish production is considered one of the alternatives to meet the increased food demand, but the processing of fish leads to by-products such as skin, bones and viscera, a source of environmental contamination. Fish viscera have been reported as an important source of digestive proteases with interesting characteristics for biotechnological processes. Thus, the aim of this study was to purify and to characterize a trypsin from the processing by-products of crevalle jack (Caranx hippos) fish.Results: A 27.5 kDa trypsin with N-terminal amino acid sequence IVGGFECTPHVFAYQ was easily purified from the pyloric caeca of the crevalle jack. Its physicochemical and kinetic properties were evaluated using N-alpha-benzoyl-(DL)-arginine-p-nitroanilide (BApNA) as substrate. in addition, the effects of various metal ions and specific protease inhibitors on trypsin activity were determined. Optimum pH and temperature were 8.0 and 50 degrees C, respectively. After incubation at 50 degrees C for 30 min the enzyme lost only 20% of its activity. K-m, k(cat), and k(cat)/K-m values using BApNA as substrate were 0.689 mM, 6.9 s(-1), and 10 s(-1) mM(-1), respectively. High inhibition of trypsin activity was observed after incubation with Cd2+, Al3+, Zn2+, Cu2+, Pb2+, and Hg2+ at 1 mM, revealing high sensitivity of the enzyme to metal ions.Conclusions: Extraction of a thermostable trypsin from by-products of the fishery industry confirms the potential of these materials as an alternative source of these biomolecules. Furthermore, the results suggest that this trypsin-like enzyme presents interesting biotechnological properties for industrial applications.Financiadora de Estudos e Projetos (FINEP/RECARCINE)Petroleo do Brasil S/A (PETROBRAS)Secretaria Especial de Aquicultura e Pesca (SEAP/PR)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundacao de Apoio a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)Univ Fed Pernambuco, Lab Enzimol LABENZ, Dept Bioquim CCB, BR-50670910 Recife, PE, BrazilUniv Fed Pernambuco, LIKA, BR-50670910 Recife, PE, BrazilUniversidade Federal de São Paulo, Dept Biofis, Escola Paulista Med, BR-04044020 São Paulo, BrazilUniv Fed Pernambuco, Lab Glicoprot, Dept Bioquim CCB, BR-50670910 Recife, PE, BrazilUniversidade Federal de São Paulo, Dept Biofis, Escola Paulista Med, BR-04044020 São Paulo, BrazilWeb of Scienc

Can contaminated waters or wastewater be alternative sources for technology-critical elements? The case of removal and recovery of lanthanides

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 reports the synthesis, characterization and application of hybrid nanostructures to remove and recover lanthanides from water, promoting the recycling of these high value elements. The nanocomposite combines the interesting properties of graphite nanoplatelets, with the magnetic properties of magnetite, and exhibits good sorption properties towards La(III), Eu(III) and Tb(III). The sorption process was very sensitive to solution pH, evidencing that electrostatic interactions are the main binding mechanism involved. Removal efficiencies up to 80% were achieved at pH 8, using only 50 mg/L of nanocomposite. In ternary solution, occurred a preferential removal of Eu(III) and Tb(III). The equilibrium evidenced a rare but interesting behaviour, and as a proof-of-concept the recoveries and reutilization rates, at consecutive cycles, highlight the recyclability of the composite without loss of efficiency. This study evidences that surface charge and the number of active sites of the composite controls the removal process, providing new insights on the interactions between lanthanoids and magnetic-graphite-nanoplatelets.publishe

Structural and magnetic studies in ferrihydrite nanoparticles formed within organic-inorganic hybrid matrices

6 pages, 6 figures, 1 table.We report detailed transmission electron microscopy, high resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy/energy dispersive x-ray spectroscopy (STEM/EDS) studies on ferrihydrite nanoparticles in an organic-inorganic matrix. The Fourier transform of HRTEM images indicates the existence of six-line ferrihydrite. Combined STEM and EDS studies give further confirmation of the presence of iron in the observed particles and its absence in the matrix. The derived mean particle size and size distribution is 4.7±0.2 nm with a lognormal deviation of s=0.4±0.1. These values were used for analysis of magnetic measurements, yielding the determination of the anisotropy constant Keff=4×105 erg/cm3 and the power relation between the number of iron ions per particle and the number of uncompensated ones p≈1/3. This value indicates that the uncompensated spins are mainly randomly distributed at the surface. According to this model, a shell thickness of about one ferrihydrite unit cell is estimated.The financial support from FCT, POCTI/ CTM/46780/02, research grant MAT2004-03395-C02-01 from the Spanish CICYT, and Acción Integrada Luso- Española E-105/04 is gratefully recognized. One of the authors (N.J.O.S.) acknowledges a grant from FCT (Grant No. SFRH/BD/10383/2002). Another author (L.M.L.-M.) acknowledges support from Xunta de Galicia (Grant No. PGIDIT03TMT30101PR).Peer reviewe

Organic-Inorganic Eu3+/Tb3+ codoped hybrid films for temperature mapping in integrated circuits

The continuous decrease on the geometric size of electronic devices and integrated circuits generates higher local power densities and localized heating problems that cannot be characterized by conventional thermographic techniques. Here, a self-referencing intensity-based molecular thermometer involving a di-ureasil organic-inorganic hybrid thin film co-doped with Eu3+ and Tb3+ tris (3-diketonate) chelates is used to obtain the temperature map of a FR4 printed wiring board with spatio-temporal resolutions of 0.42 mu m/4.8 ms

Seaweed essential oils as a new source of bioactive compounds for cyanobacteria growth control: Innovative ecological biocontrol approach

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). The application of natural compounds extracted from seaweeds is a promising eco-friendly alternative solution for harmful algae control in aquatic ecosystems. In the present study, the anti-cyanobacterial activity of three Moroccan marine macroalgae essential oils (EOs) was tested and evaluated on unicellular Microcystis aeruginosa cyanobacterium. Additionally, the possible anti-cyanobacterial response mechanisms were investigated by analyzing the antioxidant enzyme activities of M. aeruginosa cells. The results of EOs GC-MS analyses revealed a complex chemical composition, allowing the identification of 91 constituents. Palmitic acid, palmitoleic acid, and eicosapentaenoic acid were the most predominant compounds in Cystoseira tamariscifolia, Sargassum muticum, and Ulva lactuca EOs, respectively. The highest anti-cyanobacterial activity was recorded for Cystoseira tamariscifolia EO (ZI = 46.33 mm, MIC = 7.81 µg mL−1, and MBC = 15.62 µg mL−1). The growth, chlorophyll-a and protein content of the tested cyanobacteria were significantly reduced by C. tamariscifolia EO at both used concentrations (inhibition rate >67% during the 6 days test period in liquid media). Furthermore, oxidative stress caused by C. tamariscifolia EO on cyanobacterium cells showed an increase of the activities of superoxide dismutase (SOD) and catalase (CAT), and malondialdehyde (MDA) concentration was significantly elevated after 2 days of exposure. Overall, these experimental findings can open a promising new natural pathway based on the use of seaweed essential oils to the fight against potent toxic harmful cyanobacterial blooms (HCBs).This project received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 823860; Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to UIDB/04423/2020, UIDP/04423/2020 and UIDB/00690/2020 (CIMO), and also FCT, P.I., through the institutional scientific employment program-contract for L. Barros contract.info:eu-repo/semantics/publishedVersio