3,165 research outputs found
Electrochemical and photo-electrochemical processes of Methylene blue oxidation by Ti/TiO2 electrodes modified with Fe-allophane
Indexación: Scopus.This work reports the degradation of methylene blue (MB) on Ti/TiO2 and Ti/TiO2/Fe-allophane electrodes in a pH 3 using 0.1 M Na2SO4 as support electrolyte. SEM micrographs show a homogeneous distribution of TiO2 over the whole electrode surface forming nanotubes and nanopores. Fe-allophane modified electrode shows the formation of large-grains agglomerate on the electrode surface due to allophane, which provides a greater surface area to the electrode due to meso and micropore structures. Preliminary cyclic voltammetry show that Ti/TiO2 has the typical voltammetric response due to Ti(III)/Ti(IV) pair. Diffusional problems were observed through of the film when the electrode is modified with Fe-allophane modifying the quasi-reversible process Ti(III)/Ti(IV). Different kind of methodologies in the degradation process were used: Electrochemistry (EC), Photochemistry (PC), Photoelectrochemistry (PEC) and Adsorption (Ads). These methods were developing to discard any reaction or interaction that is not of interest. On Ti/TiO2 with PC and Ads methodologies was not observed any activity to MB degradation showing that is not photosensitive and that the interaction between this and surface electrode is low. But with EC and PEC degradation to 55% is reached after 3 hours of electrolysis. With Ti/TiO2-Fe-allophane electrodes are observed a higher activity for all methodologies. The PC and Ads methods show that the MB degradation reaches to ∼20 % of the initial concentration. As mentioned above, the PC and Ads processes no show degradation on Ti/TiO2, therefore the degradation it only due to the adsorption of MB in/on allophane coat behaving as concentrator matrix. A lower improvement is observed with EC process when is incorporated Ti/TiO2-Fe-allophane is due to the barrier of the electrode surface by oxidation products. With PEC is reached the higher degradation value of ∼88 %, showing an improvement of the degradation with the presence of Fe-allophane. The results indicate that the main role of Fe-allophane on the electrode is similar to a concentrator matrix.http://ref.scielo.org/shz7t
Non-linear optics with two trapped atoms
We show theoretically that two atomic dipoles in a resonator constitute a
non-linear medium, whose properties can be controlled through the relative
position of the atoms inside the cavity and the detuning and intensity of the
driving laser. We identify the parameter regime where the system operates as a
parametric amplifier, based on the cascade emission of the collective dipole of
the atoms, and determine the corresponding spectrum of squeezing of the field
at the cavity output. This dynamics could be observed as a result of
self-organization of laser-cooled atoms in resonators.Comment: 11 pages, 8 figure
Transformation Optics Approach to Plasmon-Exciton Strong Coupling in Nanocavities
We investigate the conditions yielding plasmon-exciton strong coupling at the
single emitter level in the gap between two metal nanoparticles. A
quasi-analytical transformation optics approach is developed that makes
possible a thorough exploration of this hybrid system incorporating the full
richness of its plasmonic spectrum. This allows us to reveal that by placing
the emitter away from the cavity center, its coupling to multipolar dark modes
of both even and odd parity increases remarkably. This way, reversible dynamics
in the population of the quantum emitter takes place in feasible
implementations of this archetypal nanocavity.Comment: 5 pages, 4 figure
Super-Planckian far-field radiative heat transfer
We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevicesWe acknowledge funding from
the Spanish MINECO (FIS2015-64951-R, MAT2014-53432-
C5-5-R, FIS2014-53488-P, FIS2017-84057-P), the Comunidad
de Madrid (S2013/MIT-2740), the European Union
Seventh Framework Programme (FP7-PEOPLE-2013-CIG-
630996, FP7-PEOPLE-2013-CIG-618229), and the European
Research Council (ERC-2011-AdG-290981 and ERC-2016-
STG-714870). V.F.-H. acknowledges support from “la Caixa”
Foundation and J.C.C. thanks the DFG and SFB767 for
sponsoring his stay at the University of Konstanz as Mercator Fello
High-temperature superconducting fault current microlimiters
High-temperature superconducting microbridges implemented with
YBa(2)Cu(3)O(7-delta) thin-films are shown to be possible fault current
limiters for microelectronic devices with some elements working at temperatures
below the superconducting critical temperature and, simultaneously, under very
low power conditions (below 1W). This is the case in the important applications
of superconductors as SQUID based electronics, and technologies for
communication or infrared detectors. In this paper it is shown that the good
thermal behavior of these microlimiters allows working in a regime where even
relatively small faults induce their transition to highly dissipative states,
dramatically increasing their limitation efficiency. The conditions for optimal
refrigeration and operation of these microlimiters are also proposed.Comment: 10 pages, 3 figures. LaTeX and EPS file
Photon statistics in collective strong coupling: Nanocavities and microcavities
There exists a growing interest in the properties of the light generated by hybrid systems involving a mesoscopic number of emitters as a means of providing macroscopic quantum light sources. In this work, the quantum correlations of the light emitted by a collection of emitters coupled to a generic optical cavity are studied theoretically using an effective Hamiltonian approach. Starting from the single-emitter level, we analyze the persistence of photon antibunching as the ensemble size increases. Not only is the photon blockade effect identifiable, but photon antibunching originated from destructive interference processes, the so-called unconventional antibunching, is also present. We study the dependence of these two types of negative correlations on the spectral detuning between cavity and emitters, as well as its evolution as the time delay between photon detections increases. Throughout this work, the performance of plasmonic nanocavities and dielectric microcavities is compared: despite the distinct energy scales and the differences introduced by their respectively open and closed character, the bunching and antibunching phenomenology presents remarkable similarities in both types of cavitiesThis work has been funded by the European Research
Council under Grant Agreements No. ERC-2011-AdG 290981
and No. ERC-2016-STG-714870, the EU Seventh Framework
Programme (Grants No. FP7-PEOPLE-2013-CIG-630996
and No. FP7-PEOPLE-2013-CIG-618229), and the Spanish
MINECO under Contracts No. MAT2014-53432-C5-5-R and
No. FIS2015-64951-R, as well as through the “María de
Maeztu” programme for Units of Excellence in R&D (Grant
No. MDM-2014-0377)
Organic polaritons enable local vibrations to drive long-range energy transfer
Long-range energy transfer in organic molecules has been experimentally obtained by strongly coupling their electronic excitations to a confined electromagnetic cavity mode. Here, we shed light into the polariton-mediated mechanism behind this process for different configurations: donor and acceptor molecules either intermixed or physically separated. We numerically address the phenomenon by means of Bloch-Redfield theory, which allows us to reproduce the effect of complex vibrational reservoirs characteristic of organic molecules. Our findings reveal the key role played by the middle polariton as the nonlocal intermediary in the transmission of excitations from donor to acceptor molecules. We also provide analytical insights on the key physical magnitudes that help to optimize the efficiency of the long-range energy transferThis work has been funded by the European Research Council under
Grant Agreements No. ERC-2011-AdG 290981 and No. ERC-
2016-STG-714870, the EU Seventh Framework Programme
(FP7-PEOPLE-2013-CIG-630996 and FP7-PEOPLE-2013-
CIG-618229), and the Spanish MINECO under Contracts No.
MAT2014-53432-C5-5-R and No. FIS2015-64951-R, as well
as through the “María de Maeztu” programme for Units of
Excellence in R&D (MDM-2014-0377)
Enhancing photon correlations through plasmonic strong coupling
© 2017 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibitedThere is an increasing scientific and technological interest in the design and implementation of nanoscale sources of quantum light. Here, we investigate the quantum statistics of the light scattered from a plasmonic nanocavity coupled to a mesoscopic ensemble of emitters under low coherent pumping. We present an analytical description of the intensity correlations taking place in these systems and unveil the fingerprint of plasmon-exciton-polaritons in them. Our findings reveal that plasmonic cavities are able to retain and enhance excitonic nonlinearities, even when the number of emitters is large. This makes plasmonic strong coupling a promising route for generating nonclassical light beyond the single-emitter levelFP7 Ideas: European Research Council (IDEASERC)
(ERC-2011-AdG 290981, ERC-2016-STG-714870,
FP7-PEOPLE-2013-CIG-618229, FP7-PEOPLE-2013-CIG630996);
Ministerio de Economía y Competitividad
(MINECO) (FIS2015-64951-R, MAT2014-53432-C5-5-R,
MDM-2014-0377
Atomtronics with holes: Coherent transport of an empty site in a triple well potential
We investigate arrays of three traps with two fermionic or bosonic atoms. The
tunneling interaction between neighboring sites is used to prepare multi-site
dark states for the empty site, i.e., the hole, allowing for the coherent
manipulation of its external degrees of freedom. By means of an ab initio
integration of the Schr\"odinger equation, we investigate the adiabatic
transport of a hole between the two extreme traps of a triple-well potential.
Furthermore, a quantum-trajectory approach based on the de Broglie-Bohm
formulation of quantum mechanics is used to get physical insight into the
transport process. Finally, we discuss the use of the hole for the construction
of a coherent single hole diode and a coherent single hole transistor.Comment: 9 pages, 6 figure
On the Relationship between Mechanical Properties and Crystallisation of Chemically Post-Processed Additive Manufactured Polylactic Acid Pieces
Nowadays, improvement of the surface finish of parts manufactured by fused deposition modelling is a well-studied topic. Chemical post-treatments have proven to be the best technique in terms of time consumption and smoothness improvement. However, these treatments modify the structure of the material and, consequently, its mechanical properties. This relationship was studied in this work. In this case, on the basis of a previous study on crystallisation, polylactic acid pieces were subjected to different post-treatments to evaluate their effects on the sample's mechanical properties, i.e., tensile strength and hardness. Models were obtained according to their percentage of crystallisation, which was related to the different treatments, as well as immersion time. Dramatic changes were obtained within a wide range of material behaviour with some treatments. Specifically, changes were obtained in the maximum stress (from 55 to 20 MPa), in elongation (from 3% to 260%), and in the hardness scale (Shore D to A)
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