Gallium nanoparticles colloids synthesis for UV bio-optical sensors

F. Nucciarelli, I. Bravo, L. Vázquez, E. Lorenzo, J. L. Pau, "Gallium nanoparticles colloids synthesis for UV bio-optical sensors", SPIE Optics + Optoelectronics Proc. SPIE 10231 (16 May 2017) Copyright 2017 Society of Photo Optical Instrumentation Engineers. 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 modification of the content of the paper are prohibited. Proceedings of the Optical Sensors Conference (Prague, Czech Republic) doi: https://doi.org/10.1117/12.2265883A new method for the synthesis of colloidal gallium nanoparticles (Ga NPs) based on the thermal evaporation of Ga on an expendable aluminum zinc oxide (AZO) layer is presented here. The growth of AZO layers was investigated on different substrates at room temperature and 300 °C. By means of physical evaporation process, nanoparticles were deposited with a distribution ranging from 10 nm to 80 nm in diameter. A study of their endurance in acidic environment was carried out in order to assure the NPs shape and size stability during the etching process. Smaller particles start to disappear between 1h and 2h immersion time in a pH=1 solution, while bigger particles reduce their dimension. The NPs were dispersed in tetrahydrofuran (THF) organic solvent and optically characterized, showing strong UV absorption with a band centered at 280 nm. The colloids size distribution of as-evaporated samples was compared with the distribution obtained in droplets of the solution after drop-casting. By Dipole Discrete Approximation simulations, a close relationship between the UV absorption and the NPs with diameter smaller than ∼40 nm was found. Because of the gallium oxide (Ga1-xOx) outer shell that surrounds the Ga NPs, an enhancement of their hydrophobicity occurs. Hence, the low agglomeration state between NPs in tetrahydrofuran allows to obtain narrow absorption band in the optical spectrumWe are also grateful to the international PROMIS project, framed in the Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 641899. This research is supported by the MINECO (CTQ2014-53334-C2-2-R and MAT2016-80394-R) and Comunidad de Madrid (NANOAVANSES ref. S2013/MIT-3029) Projec

Modelling and parameter estimation of gene expression and cell growth in batch cultures

Experimental procedure of CI857ts-controlled recombinant gene expression in bacterial batch cultures is mathematically modelled, and the corresponding minimum variance parameters are estimated from specific statistical or numerical methods, basically by using a global and recursive weighted least squares procedure under some constraints induced by the model. Moreover the numerical techniques proposed in this work act by accumulation of data coming from several runs of the experiment, so that more accuracy is obtained in the parameter estimation. In particular, for the production process, an extra-model parameter depending on an indicator vector is introduced for each run of the experiment in order to globalize the data. The analysis of obtained data leads to an integrated model for both cell growth and gene expression, which describes an asymmetric dynamics between culture growth and protein yield, and can serve to predict the maximal value of accumulated protein and the time required for it to be achieved at any stage of the preinducing cell growth.Postprint (published version

Tunable plasmonic resonance of gallium nanoparticles by thermal oxidation at low temperatures

This Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period provided that all the terms of the licence are adhered toThe effect of the oxidation of gallium nanoparticles (Ga NPs) on their plasmonic properties is investigated. Discrete dipole approximation has been used to study the wavelength of the out-of-plane localized surface plasmon resonance in hemispherical Ga NPs, deposited on silicon substrates, with oxide shell (Ga2O3) of different thickness. Thermal oxidation treatments, varying temperature and time, were carried out in order to increase experimentally the Ga2O3 shell thickness in the NPs. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed, barely affecting the intensity of the plasmon resonance. A controllable increase of the Ga2O3 thickness as a consequence of the thermal annealing is achieved. In addition, simulations together with ellipsometry results have been used to determine the oxidation rate, whose kinetics is governed by a logarithmic dependence. These results support the tunable properties of the plasmon resonance wavelength in Ga NPs by thermal oxidation at low temperatures without significant reduction of the plasmon resonance intensityThis research is supported by the MINECO (CTQ2014-53334-C2-2-R and MAT2016-80394-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029) projects. ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047). FN acknowledges support from Marie Sklodowska-Curie grant agreement No 641899 from the European Union’s Horizon 2020 research and innovation programm

Performance evaluation of secondary control policies with respect to digital communications properties in inverter-based islanded microgrids

A key challenge for inverted-based microgrids working in islanded mode is to maintain their own frequency and voltage to a certain reference values while regulating the active and reactive power among distributed generators and loads. The implementation of frequency and voltage restoration control policies often requires the use of a digital communication network for real-time data exchange (tertiary control covers the coordi- nated operation of the microgrid and the host grid). Whenever a digital network is placed within the loop, the operation of the secondary control may be affected by the inherent properties of the communication technology. This paper analyses the effect that properties like transmission intervals and message dropouts have for four existing representative approaches to secondary control in a scalable islanded microgrid. The simulated results reveals pros and cons for each approach, and identifies threats that properly avoided or handled in advance can prevent failures that otherwise would occur. Selected experimental results on a low- scale laboratory microgrid corroborate the conclusions extracted from the simulation study.Peer ReviewedPostprint (author's final draft

A step forward to improve recombinant protein production in Pichia pastoris : from specific growth rate effect on protein secretion to carbon-starving conditions as advanced strategy

The recombinant protein production platform based on the GAP promoter and Pichia pastoris as a host has become a very promising system from an industrial point of view. The need for highly productive bioprocesses gives grounds for the optimization of fermentation strategies maximizing yields and/or productivities, which are often associated with cell growth. Coherent with previous studies, a positive effect of high specific growth rate (μ) on the productivity was observed in carbon-limited chemostat cultivations secreting an antibody fragment. Notably, no significant impact of this factor could be observed in the balance intra- and extracellular of the product. Accordingly, fed-batch cultures operating at a constant high μ were conducted. Furthermore, short carbon-starving periods were introduced along the exponential substrate feeding phase. Strikingly, it was observed an important increase of specific production rate (qP) during such short carbon-starving periods in relation to the exponential substrate feeding intervals. Therefore, the application of carbon-starving periods as an innovative operational strategy was proposed, resulting into increments up to 50% of both yields and total production. The implementation of the proposed substrate feeding profiles should be complementary to cell engineering strategies to improve the relation qP vs μ, thereby enhancing the overall bioprocess efficiency

Analytical simulation of RBS spectra of nanowire samples

Almost all, if not all, general purpose codes for analysis of Ion Beam Analysis data have been originally developed to handle laterally homogeneous samples only. This is the case of RUMP, NDF, SIMNRA, and even of the Monte Carlo code Corteo. General-purpose codes usually include only limited support for lateral inhomogeneity. In this work, we show analytical simulations of samples that consist of a layer of parallel oriented nanowires on a substrate, using a model implemented in NDF. We apply the code to real samples, made of vertical ZnO nanowires on a sapphire substrate. Two configurations of the nanowires were studied: 40 nm diameter, 4.1 μm height, 3.5% surface coverage; and 55 nm diameter, 1.1 μm height, 42% surface coverage. We discuss the accuracy and limits of applicability of the analysisAuthors thank funding from projects CTQ2014-53334-C2-2-R (MINECO, Spain) and NANOAVANSENS S2013/MIT 3029 (Comunidad de Madrid). A.R.C. acknowledges Juan de la Cierva program (under contract number JCI-2012-14509). This work was partially funded by Fundação para a Ciência e Tecnologia under grant UID/Multi/04349/201

Hands-on quantum sensing with NV- centers in diamonds

The physical properties of diamond crystals, such as color or electrical conductivity, can be controlled via impurities. In particular, when doped with nitrogen, optically active nitrogen-vacancy centers (NV), can be induced. The center is an outstanding quantum spin system that enables, under ambient conditions, optical initialization, readout, and coherent microwave control with applications in sensing and quantum information. Under optical and radio frequency excitation, the Zeeman splitting of the degenerate states allows the quantitative measurement of external magnetic fields with high sensitivity. This study provides a pedagogical introduction to the properties of the NV centers as well as a step-by-step process to develop and test a simple magnetic quantum sensor based on color centers with significant potential for the development of highly compact multisensor systemsThis research was funded by MICIN-AEI: Grants DETECTAc and EQC2018-005134-P Comunidad de Madrid: Grant TEC2SPACE-CM P2018/NMT-4291, ONR-G: G#N62909-19-1-2053 (DEFROST), MADE-MICINN: PID2019-105552RB-C44. Garantía Juvenil nº201701520868, R.B.-G. would like to thank Comunidad de Madrid for the funding through the grant 2019-T2/IND-1336

Zinc nitride thin films: Basic properties and applications

A. Redondo-Cubero, M. Gómez-Castaño, C. García Núñez, M. Domínguez, L. Vázquez, J. L. Pau , "Zinc nitride thin films: basic properties and applications", Oxide-based Materials and Devices VIII, Proc. SPIE 10105, 101051B (24 February 2017); doi: 10.1117/12.2253044. 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 modification of the content of the paper are prohibitedProceedings of VIII Oxide-based Materials and Devices Conference (San Francisco, California, United States)Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.This research is supported by the MINECO (CTQ2014-53334-C2-2-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029). ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047

The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles

S. Catalán-Gómez, M. Briones, A. Redondo-Cubero, F. J. Palomares, F. Nucciarelli, E. Lorenzo, J. L. Pau, "The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles", SPIE Optics + Optoelectronics Proc. SPIE 10231 (16 May 2017); doi: 10.1117/12.2265665; Copyright 2017 Society of Photo‑Optical Instrumentation Engineers. 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 modification of the content of the paper are prohibited.Plasmonic Ga nanoparticles (NPs) were thermally oxidized at low temperature in order to increase the native Ga 2 O 3 shell thickness and to improve their stability during the chemical functionalization. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed with the increasing annealing time due to the Ga 2 O 3 thickness increase, and barely affecting the intensity of the plasmon resonance. This oxide layer enhances the stability of the NPs upon immersion in ethanol or water. The surface sensitivity properties of the as-grown and oxidized NPs were investigated by linking a thiol group from 6-Mercapto-1-hexanol through immersion. Ellipsometric spectra at the reversal polarization handedness (RPH) condition are in agreement with the Langmuir absorption model, indicating the formation of a thiol monolayer on the NPs