2025
Autores
da Silva, PM; Mendes, JP; Coelho, LCC; de Almeida, JMMM;
Publicação
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS
Abstract
Reinforced concrete structures form the backbone of civil infrastructure due to their durability, longevity, affordability, and availability. However, aging concrete poses challenges, with decay often beginning internally and becoming visible only at advanced stages, leading to costly repairs, restricted functionality, and safety risks. To address these challenges, sensors are crucial for enhancing infrastructure resilience and optimizing repairs. This study employs multimode optical fibers to monitor concrete curing, water ingress, relative humidity (RH), cement paste carbonation, and rebar corrosion. Four sensors monitor changes in reflection at the fiber tip of a 600 mu m multimode fiber (MMF) using LEDs and photodiodes, connected via a fiber bundle containing two 200 mu m MMF. Variations in the refractive index around the fiber tip are used to monitor water throughout the concrete lifecycle, including curing, RH changes and water intrusion. Colorimetric changes in a cement paste layer and an iron-thin film are used to monitor carbonation and corrosion. The curing sensor is temperature-independent and correlates strongly with cumulative heat release from cement hydration (R=0.95). The RH sensor monitors up to and beyond 100% RH, detecting water intrusion. The corrosion sensor detects early corrosion stages and distinguishes between reflection losses from corrosion and mechanical changes. The layer of cement paste for carbonation monitoring increases reflected intensity by 17% due to carbonation, with 63% of the increase occurring in 80 minutes in a 3% CO2 atmosphere. The broad monitoring scope and low implementation cost make this sensor a unique option among commercially available solutions for structural health monitoring of reinforced concrete.
2025
Autores
R Pereira, L; Braçais, M; Capela, D; Silva, NA; Jorge, AS; Guerner, A; Silva, SO; Frazão, O; Guimarães, D;
Publicação
EPJ Web of Conferences
Abstract
A study of an Eocene fish fossil using portable XRF revealed distinct geochemical differences between the fossil and surrounding sediment. Elements like uranium, yttrium, arsenic, and phosphorus were found only in the fossil, while calcium and iron appeared in both regions. These patterns point to selective elemental incorporation during early fossilization and diagenesis processes. The results highlight XRF's usefulness in verifying fossil authenticity, provenance and understanding the chemical processes during fossilization. © 2025 Elsevier B.V., All rights reserved.
2025
Autores
Dias, F; Ribeiro, R; Gonçalves, F; Lima, A; Roda-Robles, E; Martins, T; Guimaraes, D;
Publicação
CANADIAN JOURNAL OF MINERALOGY AND PETROLOGY
Abstract
Inductively coupled plasma-mass spectrometry analysis was conducted to examine the geochemical composition of Kfeldspars from various aplite-pegmatites in the Barroso-Alv & atilde;o field, focusing on the differences between Li-rich and Li-barren aplite-pegmatites. The study revealed significant variations in the concentrations of minor and trace elements (Rb, Tl, Li, Ga, Pb, Cs, Ba, Be, Ta, and Sn) present in the K-feldspars of Li-barren, spodumene-rich, and petalite-rich aplite-pegmatites. The data also indicate a geographical trend in both mineralogy and geochemistry across the aplite-pegmatites of the Barroso-Alv & atilde;o field. Li-barren aplite-pegmatites are more concentrated in the southeast, spodumene-rich dominate the center, and petalite-rich varieties are more common in the northwest. Additionally, portable X-ray fluorescence analysis was performed on the crystals of the same samples to evaluate the feasibility of in situ geochemical analysis of K-feldspars, aiming to determine whether an aplite-pegmatite can be quickly identified as Li-rich. This approach seeks to provide a rapid field assessment of whether an aplite-pegmatite justifies further exploration for Li mining. Notably, the trace amounts of Li, Sn, P, and Ta found in K-feldspars are likely due to mineral inclusions of spodumene, cassiterite, apatite, and columbite-tantalite minerals, as observed petrographically in one of these Li-rich aplite-pegmatites.
2025
Autores
Capela, D; Manso, M; Lopes, T; Cavaco, R; Teixeira, J; Jorge, PAS; Silva, NA; Guimaraes, D;
Publicação
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS
Abstract
Heritage preservation requires innovative sensing technologies to analyze their chemical composition while minimizing damage. This study introduces a Laser-induced Breakdown Spectroscopy (LIBS) system featuring a fiber laser source and optical fiber-based collection system for the analysis of heritage ceramics. Comparative experiments with a conventional Nd:YAG laser LIBS system highlight the advantages and trade-offs of the fiber laser system in terms of ablation capability, spectral mapping, and depth profiling. Results were validated against X-ray Fluorescence (XRF). Experiments demonstrate minimal surface alteration and high-quality spectral data for elements such as Pb, Fe, Zn, Sb, Mn, Ti Na, Ba and Ca. The compact design and good results position this system as a transformative tool for heritage conservation.
2025
Autores
Almeida, MAS; Pires, AL; Ramirez, JL; Malik, SB; de la Flor, S; Llobet, E; Pereira, AT; Pereira, AM;
Publicação
ADVANCED SCIENCE
Abstract
In recent advancements within sensing technology, driven by the Internet of Things (IoT), significant impacts are observed on health sector applications, notably through wearable electronics like electronic tattoos (e-tattoos). These e-tattoos, designed for direct contact with the skin, facilitate precise monitoring of vital physiological parameters, including body heat, a critical indicator for conditions such as inflammation and infection. Monitoring these indicators can be crucial for early detection of chronic conditions, steering toward proactive healthcare management. This study delves into a thermoelectric sensor e-tattoo designed for detailed skin temperature mapping. Utilizing a novel design, this sensor detects temperature variations across thermoelectric stripes, leveraging screen-printed films of p-type Bi0.35Sb1.65Te3, n-type Bi2Te2.8Se0.2, and poly(vinyl alcohol) (PVA) for enhanced thermoelectric and flexible properties. The application of a prototype printed thermoelectric device on temporary tattoo paper, a pioneering development in wearable health technology is demonstrated. This device, validated through numerical simulations, exhibits significant potential as a non-invasive tool for temperature monitoring, highlighting its value in health diagnostics and management.
2025
Autores
Monteiro, M; Figueiredo, R; Silva, T; Pereira, M; Azenha, M; Ribeiro, A;
Publicação
Microchemical Journal
Abstract
The development of simple, selective, and cost-effective methods for quantification of bovine serum albumin (BSA) is currently very important for assessing milk quality (and safety). In this work, a new surface plasmon resonance (SPR) sensor was developed, consisting of imprinted hydrogel-based nanoparticles (nanoMIPs) immobilized on gold platforms, to quantify BSA in bovine milk. The nanoMIPs prepared for recognition of BSA were synthesized by the precipitation polymerization approach, using a synthetic BSA epitope (VVSTQTALA) as template. The spherical MIP nanoparticles (NPs) had an average size of 60 nm. The binding studies performed revealed that the binding affinity of the prepared nanoMIPs to BSA (KD = 7.1 × 10-6 mol L-1) was comparable to that obtained by a natural BSA antibody (KD = 2.5 × 10-6 mol L-1). The plasmonic sensor incorporating the MIP nanomaterials achieved a limit of detection (LOD) of 1.02 × 10-6 mol L-1 (0.068 mg mL-1) and a limit of quantification (LOQ) of 3.39 × 10-6 mol L-1 (0.225 mg mL-1), over a linear range from 2.0 × 10-6 mol L-1 to 1.5 × 10-5 mol L-1. Moreover, the selectivity studies revealed a significant sensor response towards casein and a negligible response towards vancomycin. In the end, the optical sensor was tested against commercial milk samples, showing promising viability for detection of BSA as the value reported by the plasmonic sensor ((1.0 ± 0.1) × 10-4 mol L-1) was very close to that obtained by size exclusion-high-performance liquid chromatography (SEC-HPLC). © 2025 The Author(s)
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