Plasmonic strain sensors based on Au-TiO2 thin films on flexible substrates

This study aimed at introducing thin films exhibiting the localized surface plasmon resonance (LSPR) phenomenon with a reversible optical response to repeated uniaxial strain. The sensing platform was prepared by growing gold (Au) nanoparticles throughout a titanium dioxide dielectric matrix. The thin films were deposited on transparent polymeric substrates, using reactive magnetron sputtering, followed by a low temperature thermal treatment to grow the nanoparticles. The microstructural characterization of the thin films’ surface revealed Au nanoparticle with an average size of 15.9 nm, an aspect ratio of 1.29 and an average nearest neighbor nanoparticle at 16.3 nm distance. The plasmonic response of the flexible nanoplasmonic transducers was characterized with custom-made mechanical testing equipment using simultaneous optical transmittance measurements. The higher sensitivity that was obtained at a maximum strain of 6.7%, reached the values of 420 nm/ε and 110 pp/ε when measured at the wavelength or transmittance coordinates of the transmittance-LSPR band minimum, respectively. The higher transmittance gauge factor of 4.5 was obtained for a strain of 10.1%. Optical modelling, using discrete dipole approximation, seems to correlate the optical response of the strained thin film sensor to a reduction in the refractive index of the matrix surrounding the gold nanoparticles when uniaxial strain is applied.This research was funded by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 and by the projects NANO4BIO: POCI01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/2017, and CO2Plasmon with FCT reference EXPL/CTM-REF/0750/2021

Enhancing the sensitivity of nanoplasmonic thin films for ethanol vapor detection

Nanoplasmonic thin films, composed of noble metal nanoparticles (gold) embedded in an oxide matrix, have been a subject of considerable interest for Localized Surface Plasmon Resonance (LSPR) sensing. Ethanol is one of the promising materials for fuel cells, and there is an urgent need of a new generation of safe optical sensors for its detection. In this work, we propose the development of sensitive plasmonic platforms to detect molecular analytes (ethanol) through changes of the LSPR band. The thin films were deposited by sputtering followed by a heat treatment to promote the growth of the gold nanoparticles. To enhance the sensitivity of the thin films and the signal-to-noise ratio (SNR) of the transmittance–LSPR sensing system, physical plasma etching was used, resulting in a six-fold increase of the exposed gold nanoparticle area. The transmittance signal at the LSPR peak position increased nine-fold after plasma treatment, and the quality of the signal increased six times (SNR up to 16.5). The optimized thin films seem to be promising candidates to be used for ethanol vapor detection. This conclusion is based not only on the current sensitivity response but also on its enhancement resulting from the optimization routines of thin films’ architectures, which are still under investigation.This research was funded by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the projects NANOSENSING: POCI-01-0145-FEDER-016902, with FCT reference PTDC/FIS-NAN/1154/2014, and NANO4BIO: POCI-01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/201

HPC Cloud for Scientific and Business Applications: Taxonomy, Vision, and Research Challenges

High Performance Computing (HPC) clouds are becoming an alternative to on-premise clusters for executing scientific applications and business analytics services. Most research efforts in HPC cloud aim to understand the cost-benefit of moving resource-intensive applications from on-premise environments to public cloud platforms. Industry trends show hybrid environments are the natural path to get the best of the on-premise and cloud resources---steady (and sensitive) workloads can run on on-premise resources and peak demand can leverage remote resources in a pay-as-you-go manner. Nevertheless, there are plenty of questions to be answered in HPC cloud, which range from how to extract the best performance of an unknown underlying platform to what services are essential to make its usage easier. Moreover, the discussion on the right pricing and contractual models to fit small and large users is relevant for the sustainability of HPC clouds. This paper brings a survey and taxonomy of efforts in HPC cloud and a vision on what we believe is ahead of us, including a set of research challenges that, once tackled, can help advance businesses and scientific discoveries. This becomes particularly relevant due to the fast increasing wave of new HPC applications coming from big data and artificial intelligence.Comment: 29 pages, 5 figures, Published in ACM Computing Surveys (CSUR

Revisiting context-aware component interconnection

Software connectors are external coordination devices which ensure the flow of data and enforce synchronization constraints within a component’s network. The specification of software connectors through which context dependent behaviour is correctly propagated remains an open, non trivial issue in their semantics. This paper, building on previous work by the authors, revisits this problem and introduces a model in which context awareness is suitably handled

NANOPTICS: in-depth analysis of NANomaterials for OPTICal localized surface plasmon resonance sensing

Thin films containing metal (gold, silver, etc.) nanoparticles are important platforms for molecularsensing based on the localized surface plasmon resonance (LSPR) phenomenon. To support their usein high-resolution LSPR spectroscopy systems, a software package, called NANOPTICS, was developed.It performs a statistical analysis of the LSPR band of the films, employing central moments of the normalized spectral distribution of optical transmittance. LSPR band parameters, signal-to-noise ratio and refractive index sensitivity are the outputs. It is shown that NANOPTICS can be a powerful tool to perform fast diagnostics of LSPR-based sensors’ sensitivity and to analyse their response to target analytes.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020; and by the projects NANOSENSING POCI-01-0145-FEDER-016902, with FCT reference PTDC/FIS-NAN/1154/2014; and project NANO4BIO POCI-01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/2017. Marco S. Rodrigues acknowledges FCT for his PhD Scholarship, SFRH/BD/118684/2016. Joel Borges acknowledges FCT for his Researcher Contract from project NANO4BIO

Preparation of plasmonic Au-TiO2 thin films on a transparent polymer substrate

In this work, plasmonic thin films composed of Au nanoparticles embedded in a TiO2 matrix were prepared in a transparent polymer substrate of poly(dimethylsiloxane) (PDMS). The thin films were deposited by reactive DC magnetron sputtering, and then subjected to heat treatment up to 150 °C in order to promote the growth of the Au nanoparticles throughout the TiO2 matrix. The transmittance spectrum of the thin films was monitored in situ during the heat treatment, and the minimum time required to have a defined localized surface plasmon resonance (LSPR) band was about 10 min. The average size of Au nanoparticles was estimated to be about 21 nm—the majority of them are sized in the range 10–40 nm, but also extend to larger sizes, with irregular shapes. The refractive index sensitivity of the films was estimated by using two test fluids (H2O and DMSO), and the average value reached in the assays was 37.3 ± 1.5 nm/RIU, resulting from an average shift of 5.4 ± 0.2 nm. The results show that it is possible to produce sensitive plasmonic Au-TiO2 thin films in transparent polymer substrates such as PDMS, the base material to develop microfluidic channels to be incorporated in LSPR sensing systems.This research was funded by the Portuguese Foundation for Science and Technology (FCT), co-financed by European Regional Development Fund (ERDF), in the framework of the Strategic Funding, grant number UID/FIS/04650/2019; also by the project NANOSENSING, grant number POCI-01-0145-FEDER-016902 and FCT reference PTDC/FIS-NAN/1154/2014; and by the project NANO4BIO, grant number POCI-01-0145-FEDER-032299 and FCT reference PTDC/FIS-MAC/32299/2017.Joel Borges acknowledges the Portuguese Foundation for Science and Technology (FCT) for his Researcher Contract from project NANO4BIO (grant number POCI-01-0145-FEDER-032299 and FCT reference PTDC/FIS-MAC/32299/2017). Diana I. Meira acknowledges FCT for her PhD Scholarship, SFRH/BD/143262/2019. Marco S. Rodrigues acknowledges FCT for his PhD Scholarship, SFRH/BD/118684/2016. Cláudia Lopes acknowledges her post-doctoral fellowship from project NANOSENSING (POCI-01-0145-FEDER-016902 and FCT reference PTDC/FIS-NAN/1154/2014)

Traumatic experiences in a lifetime: impact on the connection with others and the role of emotions

Abstract in proceedings of the Fourth International Congress of CiiEM: Health, Well-Being and Ageing in the 21st Century, held at Egas Moniz’ University Campus in Monte de Caparica, Almada, from 3–5 June 2019.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.info:eu-repo/semantics/publishedVersio

Dry electrodes for surface electromyography based on architectured titanium thin films

Electrodes of silver/silver chloride (Ag/AgCl) are dominant in clinical settings for surface electromyography (sEMG) recordings. These electrodes need a conductive electrolyte gel to ensure proper performance, which dries during long-term measurements inhibiting the immediate electrode’s reuse and is often linked to skin irritation episodes. To overcome these drawbacks, a new type of dry electrodes based on architectured titanium (Ti) thin films were proposed in this work. The architectured microstructures were zigzags, obtained with different sputtering incidence angles (α), which have been shown to directly influence the films’ porosity and electrical conductivity. The electrodes were prepared using thermoplastic polyurethane (TPU) and stainless-steel (SS) substrates, and their performance was tested in male volunteers (athletes) by recording electromyography (EMG) signals, preceded by electrode-skin impedance measurements. In general, the results showed that both SS and TPU dry electrodes can be used for sEMG recordings. While SS electrodes almost match the signal quality parameters of reference electrodes of Ag/AgCl, the performance of electrodes based on TPU functionalized with a Ti thin film still requires further improvements. Noteworthy was the clear increase of the signal to noise ratios when the thin films’ microstructure evolved from normal growth towards zigzag microstructures, meaning that further tailoring of the thin film microstructure is a possible route to achieve optimized performances. Finally, the developed dry electrodes are reusable and allow for multiple EMG recordings without being replaced.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and Bilateral Project FCT/DAAD 2016/2017 “Sunshine” (No. 3340). Joel Borges acknowledges FCT for his Researcher Contract from project NANO4BIO POCI-01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/2017. Marco S. Rodrigues acknowledges FCT for his PhD Scholarship, SFRH/BD/118684/2016

Optimization of Au:CuO thin films by plasma surface modification for high-resolution LSPR gas sensing at room temperature

In this study, thin films composed of gold nanoparticles embedded in a copper oxide matrix (Au:CuO), manifesting Localized Surface Plasmon Resonance (LSPR) behavior, were produced by reactive DC magnetron sputtering and post-deposition in-air annealing. The effect of low-power Ar plasma etching on the surface properties of the plasmonic thin films was studied, envisaging its optimization as gas sensors. Thus, this work pretends to attain the maximum sensing response of the thin film system and to demonstrate its potential as a gas sensor. The results show that as Ar plasma treatment time increases, the host CuO matrix is etched while Au nanoparticles are uncovered, which leads to an enhancement of the sensitivity until a certain limit. Above such a time limit for plasma treatment, the CuO bonds are broken, and oxygen is removed from the film’s surface, resulting in a decrease in the gas sensing capabilities. Hence, the importance of the host matrix for the design of the LSPR sensor is also demonstrated. CuO not only provides stability and protection to the Au NPs but also promotes interactions between the thin film’s surface and the tested gases, thereby improving the nanocomposite film’s sensitivity. The optimized sensor sensitivity was estimated at 849 nm/RIU, which demonstrates that the Au-CuO thin films have the potential to be used as an LSPR platform for gas sensors.This research was sponsored by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 and by the project CO2Plasmon with reference EXPL/CTM-REF/0750/2021. M.P. acknowledges her Ph.D. Scholarship from FCT, with reference SFRH/BD/137076/2018. Diana I. Meira acknowledges her Ph.D. Scholarship from FCT, with reference SFRH/BD/143262/2019