Enhancing visibility of graphene on arbitrary substrates by microdroplet condensation

In order to take advantage of the enormous potential of graphene for future electronic micro-circuits and other applications it is necessary to develop reliable, rapid and widely applicable methods to visualize graphene based structures. We report here on a micro-droplet condensation technique, which allows for quick visual identification of graphene on a variety of substrates, including some which were previously considered unsuitable for the visualization of carbon layers. The technique should also be applicable to visualize artificially patterned graphene structures which are expected to be key technologically enabling components in electronic micro-circuits and other applications.Comment: 12 pages, 3 figure

Tubular carbonate concretions as hydrocarbon migration pathways? Examples from North Island, New Zealand

Cold seep carbonate deposits are associated with the development on the sea floor of distinctive chemosyn¬thetic animal communities and carbonate minerali¬sation as a consequence of microbially mediated anaerobic oxidation of methane. Several possible sources of the methane exist, identifiable from the carbon isotope values of the carbonate precipitates. In the modern, seep carbonates can occur on the sea floor above petroleum reservoirs where an important origin can be from ascending thermogenic hydrocar¬bons. The character of geological structures marking the ascent pathways from deep in the subsurface to shallow subsurface levels are poorly understood, but one such structure resulting from focused fluid flow may be tubular carbonate concretions. Several mudrock-dominated Cenozoic (especially Miocene) sedimentary formations in the North Island of New Zealand include carbonate concretions having a wide range of tubular morphologies. The concretions are typically oriented at high angles to bedding, and often have a central conduit that is either empty or filled with late stage cements. Stable isotope analyses (δ13C, δ18O) suggest that the carbonate cements in the concretions precipitated mainly from ascending methane, likely sourced from a mixture of deep thermogenic and shallow biogenic sources. A clear link between the tubular concretions and overlying paleo-sea floor seep-carbonate deposits exists at some sites. We suggest that the tubular carbonate concretions mark the subsurface plumbing network of cold seep systems. When exposed and accessible in outcrop, they afford an opportunity to investigate the geochemical evolution of cold seeps, and possibly also the nature of linkages between subsurface and surface portions of such a system. Seep field development has implications for the characterisation of fluid flow in sedimentary basins, for the global carbon cycle, for exerting a biogeochemical influence on the development of marine communities, and for the evaluation of future hydrocarbon resources, recovery, and drilling and production hazards. These matters remain to be fully assessed within a petroleum systems framework for New Zealand’s Cenozoic sedimentary basins

Production and photoactivity spectrum of Ni/TiO2 core shell nanoparticles

In this work, Ni nanoparticles were obtained by laser ablation of a Nickel target with femtosecond pulses from a Ti-Sapphire laser in an aqueous media. Subsequently, these nanoparticles were isolated and covered with TiO2.FCT, FEDER, COMPETE/QREN/EU for financial support to CFUM (Strategic Project PEst-C/FIS/UI0607/2011

Self-assembled dextrin nanogel as curcumin delivery system

Curcumin is a natural polyphenol with anti-oxidative, anti-inflammatory and anti-cancer properties. Its therapeutic potential is substantially hindered by the rather low water solubility and bioavailability, hence the need for suitable carriers. In this study, we show that self-assembled nanogels obtained from hydrophobically modified dextrin are effec-tive curcumin nanocarriers. The stability and loading efficiency of curcumin-loaded nanogel depends on the nano-gel/curcumin ratio. Higher stability of the formulation is achieved in water than in PBS buffer, as evaluated by dynamic light scattering and fluorescence measurements. The in vitro release profile, using sink conditions, indicates that dextrin nanogel may perform as a suitable carrier for the controlled release of curcumin. Biological activity of curcumin-loaded nanogel in HeLa cell cultures was assessed using the MTS assay

Design, synthesis and characterization of the electrochemical, nonlinear optical properties and theoretical studies of novel thienylpyrrole azo dyes bearing benzothiazole acceptor groups

Two series of related donor-acceptor conjugated heterocyclic azo dyes based on the thienylpyrrole system, functionalized with benzothiazol-2-yl (5-6) or benzothiazol-6-yl acceptor groups (7) through an N=N bridge, have been synthesized by azo coupling using 1-alkyl(aryl)thienylpyrroles (1) and benzothiazolyl diazonium salts (2-4) as coupling components. Their optical (linear and first hyperpolarizability), electrochemical and thermal properties have been examined. Optimized ground-state molecular geometries and estimates of the lowest energy single electron vertical excitation energies in dioxane solutions were obtained using density functional theory (DFT) at the B3LYP/6-31+G(d,p) level. Hyper-Rayleigh scattering (HRS) in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. Of these systems, the benzothiazol-2-yl-diazenes 5-6 exhibit the largest first hyperpolarizabilities ( = 460 - 660 x 10-30 esu, T convention) compared to benzothiazol-6-yl-diazenes 7 ( = 360 - 485 x 10-30 esu, T convention). Good to excellent thermal stabilities were also obtained for all azo dyes (235 - 317 oC). This multidisciplinary study showed that modulation of the optical and electronic properties can be achieved by introduction of the benzothiazole acceptor group in the thienylpyrrole system through position 2 or 6 of the benzothiazole heterocycle.Thanks are due to the Fundacao para a Ciencia e Tecnologia (Portugal) and FEDER for financial support through the Centro de Quimica and Centro de Fisica- Universidade do Minho, Project FTDC/QUI/66251/2006 (FCOMP-01-0124-FEDER-007429), Project PTDC/CTM/105597/2008 with funding from COMPETE/FEDER and a research grant to M. C. R. Castro (UMINHO/BI/142/2009). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT.We acknowledge the computational support of the Project SeARCH (Services and Advanced Research Computing with HTC/HPC clusters), funded by FCT under contract CONC-REEQ/443/EEI/2005

Synthesis and photophysical studies of new pyrenylamino acids

Two new pyrenylamino acid derivatives were synthesized from beta-bromodehydroalanine derivatives in good yields using addition and elimination reactions. The photophysical properties of the two new pyrenylamino acids were studied in several solvents. Steady-state and time-resolved fluorescence measurements revealed that the bipyrenylamino acid undergoes excimer formation, this process being solvent dependent. Rate constants for excimer formation and dissociation were calculated. The monopyrenylamino acid exhibits a photophysical behavior similar to that of pyrene, including the sensitivity to solvent polarity. The results point to a potential use of these new pyrenyl derivatives as fluorescent probes for peptides and proteins.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Projects of CFUM [PEst-C/FIS/UI0607/2011 (F-COMP-01-0124-FEDER-022711)] and CQ/UM [PEst-C/QUI/UI0686/2011 (FCOMP-01-0124-FEDER-022716)] and through the research project PTDC/QUI/81238/2006 (FCOMP-01-0124-FEDER-007467). The NMR spectrometer Bruker Avance II 400 is part of the National NMR Network and was acquired with funds from FCT and FEDER. FCT is also acknowledged for the PhD grant of G.P. (SFRH/BD/38766/2007)

Design, synthesis and evaluation of redox, second order nonlinear optical properties and theoretical DFT studies of novel bithiophene azo dyes functionalized with thiadiazole acceptor groups

Two series of novel thermally stable second-order nonlinear optical (NLO) heterocyclic azo dyes 4-5 have been designed and synthesized. The two series of compounds were based on different combinations of acceptor groups (thiadiazole or arylthiadiazole electron-deficient heterocycles) linked to bithiophene which acts at the same time as a donor group and as a pi-conjugated bridge. The solvatochromic behavior of azo dyes 4-5 was investigated in several solvents of different polarity, while their thermal stability was evaluated using thermogravimetric analysis. Optimized ground-state molecular geometries and an estimation of the lowest energy single electron vertical excitation energies in DMF solutions were obtained using density functional theory (DFT). Their redox properties were studied by cyclic voltammetry, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The measured molecular first hyperpolarizabilities and the observed electrochemical behavior showed variations for the different acceptor systems used (thiadiazole or arylthiadiazole) and were also sensitive to the electronic acceptor strength of the substituents (R) linked to thiadiazole or arylthiadiazole heterocycles. Donor-acceptor arylthiadiazole-bithienyl diazenes exhibit the most promising thermal (Td = 237-305 ºC) and solvatochromic (beta = 1117-2503 cm-1) properties and second order nonlinear optical response (136-226 x 10-30 esu).Fundação para a Ciência e a Tecnologia (FCT

Exciton migration in self-assembled dendrite-type fractal superstructures of monodisperse Quantum Dots

We investigated dendrite shaped superstructures made of two different QDs, namely CdSe/ZnS and CdTe. Due to the dense packing of QDs, Förster resonance energy transfer (FRET) may compete with deexcitation, and the specific dendrite shaped structure suggests the possibility of funneling of excitation from the edges of the structure to the center.Financial support from the Portuguese Foundation for Science and Technology (FCT) and FEDER through Projects PTDC/FIS/113199/2009 and PEst-C/FIS/UI0607/2013 is gratefully acknowledged

Energy transfer via exciton transport in quantum dot based self-assembled superstructures

We fabricated dendrite-type superstructures of fractal dimension consisting of CdSe/ZnS & CdTe capped nanodots. These structures were studied using microscopic fluorescence intensity imaging as well as spectral and lifetime mapping.FCT Concurso "Ciência 2007"; MAP-Fis Doctoral Programme (Doutoramento FCT)info:eu-repo/semantics/publishedVersio

A versatile fluorescence lifetime imaging system for scanning large areas with high time and spatial resolution

"Published in SPIE Proceedings Vol. 9286"We present a flexible fluorescence lifetime imaging device which can be employed to scan large sample areas with a spatial resolution adjustable from many micrometers down to sub-micrometers and a temporal resolution of 20 picoseconds. Several different applications of the system will be presented including protein microarrays analysis, the scanning of historical samples, evaluation of solar cell surfaces and nanocrystalline organic crystals embedded in electrospun polymeric nanofibers. Energy transfer processes within semiconductor quantum dot superstructures as well as between dye probes and graphene layers were also investigated.This work was financially supported by the European Regional Development Fund (ERDF) through Programa Operacional Factores de Competitividade (COMPETE: FCOMP-01-0124-FEDER-014628) and the Portuguese Fundacao para a Ciencia e Tecnologia (FCT) through the projects "Functional structuring, inter-particle interaction and energy transfer in ensembles of nanocrystal dots" (PTDC/FIS/113199/2009), Ultra-fast spectroscopy on the dynamics and relaxation of Dirac electrons in graphene" (PTDC/FIS/101434/ 2008) and "Low dimensional nanostructures for nonlinear optical applications" PTDC/CTmNAN/114269/2009