Write-erase and read paper memory transistor

Applied Physics Letters, Vol.93, issue 20

Electron driven reactions in complexes embedded in superfluid helium droplets

A thesis submitted to the University of Innsbruck for the doctor degree in Natural Sciences, Physics and New University of Lisbon for the doctor degree in Physics, Atomic and Molecular Physics

Perylene Diimide acceptors: Fabrication and characterization of electron-only, hole-only devices and solar cells

The thrust towards energy conservation and reduced environmental footprint has fueled intensive research for alternative low cost sources of renewable energy. Organic photovoltaic cells (OPVs), with their low fabrication costs, easy processing and flexibility, represent a possible viable alternative. Perylene diimides (PDIs) are promising electron-acceptor candidates for bulk heterojunction (BHJ) OPVs, as they combine higher absorption and stability with tunable material properties, such as solubility and position of the lowest unoccupied molecular orbital (LUMO) level. A prerequisite for trap free electron transport is for the LUMO to be located at a level deeper than 3.7 eV since electron trapping in organic semiconductors is universal and dominated by a trap level located at 3.6 eV. Although the mostly used fullerene acceptors in polymer:fullerene solar cells feature trap-free electron transport, low optical absorption of fullerene derivatives limits maximum attainable efficiency. In this thesis, we try to get a better understanding of the electronic properties of PDIs, with a focus on charge carrier transport characteristics and the effect of different processing conditions such as annealing temperature and top contact (cathode) material. We report on a commercially available PDI and three PDI derivatives as acceptor materials, and its blends with MEH-PPV (Poly[2-methoxy 5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) and P3HT (Poly(3-hexylthiophene-2,5-diyl)) donor materials in single carrier devices (electron-only and hole-only) and in solar cells. Space-charge limited current measurements and modelling of temperature dependent J-V characteristics confirmed that the electron transport is essentially trap-free in such materials. Different blend ratios of P3HT:PDI-1 (1:1) and (1:3) show increase in the device performance with increasing PDI-1 ratio. Furthermore, thermal annealing of the devices have a significant effect in the solar cells that decreases open-circuit voltage (Voc) and fill factor FF, but increases short-circuit current (Jsc) and overall device performance. Morphological studies show that over-aggregation in traditional donor:PDI blend systems is still a big problem, which hinders charge carrier transport and performance in solar cells.

A further investigation of the cytochrome b5–cytochrome c complex

J Biol Inorg Chem (2003) 8: 777–786

Electrochemical studies on small electron transfer proteins using membrane electrodes

Journal of Electroanalytical Chemistry 541 (2003) 153-162

In-situ X-ray diffraction studies during growth of Ni-Ti shape memory alloy films and their complementary ex-situ characterization

Shape Memory Alloy (SMA) Ni-Ti films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. Thus, the main challenge is not only the control of the microstructure, including stoichiometry and precipitates, but also the identification and control of the preferential orientation since it is a crucial factor in determining the shape memory behaviour. The aim of this PhD thesis is to study the optimisation of the deposition conditions of films of Ni-Ti in order to obtain the material fully crystallized at the end of the deposition, and to establish a clear relationship between the substrates and texture development. In order to achieve this objective, a two-magnetron sputter deposition chamber has been used allowing to heat and to apply a bias voltage to the substrate. It can be mounted into the six-circle diffractometer of the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France, enabling an in-situ characterization by X-ray diffraction(XRD) of the films during their growth and annealing. The in-situ studies enable us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters on the structural characteristics of the deposited film. Besides the in-situ studies, other complementary ex-situ characterization techniques such as XRD at a laboratory source, Rutherford backscattering spectroscopy(RBS), Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and electrical resistivity (ER) measurements during temperature cycling have been used for a fine structural characterization. In this study, mainly naturally and thermally oxidized Si(100) substrates, TiN buffer layers with different thicknesses (i.e. the TiN topmost layer crystallographic orientation is thickness dependent) and MgO(100) single crystals were used as substrates. The chosen experimental procedure led to a controlled composition and preferential orientation of the films. The type of substrate plays an important role for the texture of the sputtered Ni-Ti films and according to the ER results, the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation characteristics.

Assessment of climate change statistical downscaling methods: Application and comparison of two statistical methods to a single site in Lisbon

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia do Ambiente

Development of biocompatible and “smart” porous structures using CO2-assisted processes

Dissertação apresentada para a obtenção do grau de Doutor em Engenharia Química, especialidade Engenharia da Reacção Química, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

High-performance flexible hybrid field-effect transistors based on cellulose fiber paper

IEEE Electron Device Letters, VOL. 29, NO. 9,

Fully transparent ZnO thin-film transistor produced at room temperature

Advanced Materials, Vol. 17, nº 5

Electron and photon induced processes in SF5CF3

The photo-absorption cross section of trifluoromethyl sulphur pentafluoride, SF5CF3 has been measured using synchrotron radiation in the range of 4–11 eV (310 nm > l > 110 nm) and comparison made with electron energy loss spectroscopy (EELS). The measured VUV cross sections are used to derive the photolysis rate of SF5CF3 in the terrestrial atmosphere. It is estimated that the lifetime for this molecule is the order of a 1000 years and the calculated global warming potential (GWP) is found to be between 17000 and 18100, making it one of the most potent global warming gases in the terrestrial atmosphere.

Spectroscopic Studies and Characterization of a Novel Electron-Transfer Chain

A novel two-component enzyme system from Escherichia coli involving a flavorubredoxin (FlRd) and its reductase was studied in terms of spectroscopic, redox, and biochemical properties of its constituents. FlRd contains one FMN and one rubredoxin (Rd) center per monomer. To assess the role of the Rd domain, FlRd and a truncated form lacking the Rd domain (FlRd¢Rd), were characterized. FlRd contains 2.9 ( 0.5 iron atoms/subunit, whereas FlRd¢Rd contains 2.1 ( 0.6 iron atoms/subunit. While for FlRd one iron atom corresponds to the Rd center, the other two irons, also present in FlRd¢Rd, are most probably due to a di-iron site. Redox titrations of FlRd using EPR and visible spectroscopies allowed us to determine that the Rd site has a reduction potential of -140 ( 15 mV, whereas the FMN undergoes reduction via a red-semiquinone, at -140 ( 15 mV (Flox/Flsq) and -180 ( 15 mV (Flsq/Flred), at pH 7.6. The Rd site has the lowest potential ever reported for a Rd center, which may be correlated with specific amino acid substitutions close to both cysteine clusters. The gene adjacent to that encoding FlRd was found to code for an FAD-containing protein, (flavo)rubredoxin reductase (FlRd-reductase), which is capable of mediating electron transfer from NADH to DesulfoVibrio gigas Rd as well as to E. coli FlRd. Furthermore, electron donation was found to proceed through the Rd domain of FlRd as the Rd-truncated protein does not react with FlRd-reductase. In vitro, this pathway links NADH oxidation with dioxygen reduction. The possible function of this chain is discussed considering the presence of FlRd homologues in all known genomes of anaerobes and facultative aerobes.

The alternative complex III from Rhodothermus marinus - a prototype of a new family of quinol: electron acceptor oxidoreductase

Dissertation presented to obtain a PhD degree in Biochemistry at the Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

New fluorescent chemosensors based on bio-inspired ligands and macrocycles: from single molecules to nanoparticles

Dissertação apresentada para obtenção do grau de Doutor em Biotecnologia pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia. A presente dissertação foi preparada no âmbito do protocolo de acordo bilateral de educação avançada (ERASMUS) entre a Universidade de Vigo e a Universidade Nova de Lisboa

Development of 2-oxazoline-based hydrogels and porous polyester microparticles in scCO2

Thesis submitted to Faculdade de Ciências e Tecnologia from Universidade Nova de Lisboa in partial fulfillment of the requirements for the obtention of the degree of Master of Science in Biotechnology