Open Access
A nanocomposite sol-gel film based on PbS quantum dots embedded into an amorphous host inorganic matrix
(MDPI, 2023) Mihail, Elisa; Sava, Bogdan Alexandru; Eftimie, Mihai; Nicoara, Adrian Ionut; Vasiliu, Ileana Cristina; Rusu, Madalin Ion; Bartha, Cristina; Enculescu, Monica; Kuncser, Andrei Cristian; Oane, Mihai; Elosúa Aguado, César; López Torres, Diego; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this study, a sol-gel film based on lead sulfide (PbS) quantum dots incorporated into a host network was synthesized as a special nanostructured composite material with potential applications in temperature sensor systems. This work dealt with the optical, structural, and morphological properties of a representative PbS quantum dot (QD)-containing thin film belonging to the Al2O3–SiO2–P2O5 system. The film was prepared using the sol-gel method combined with the spin coating technique, starting from a precursor solution containing a suspension of PbS QDs in toluene with a narrow size distribution and coated on a glass substrate in a multilayer process, followed by annealing of each deposited layer. The size (approximately 10 nm) of the lead sulfide nanocrystallites was validated by XRD and by the quantum confinement effect based on the band gap value and by TEM results. The photoluminescence peak of 1505 nm was very close to that of the precursor PbS QD solution, which demonstrated that the synthesis route of the film preserved the optical emission characteristic of the PbS QDs. The photoluminescence of the lead sulfide QD-containing film in the near infrared domain demonstrates that this material is a promising candidate for future sensing applications in temperature monitoring.
Open Access
Piezotronic, ZnO overlaid Bragg grating organic vapor sensors
(IEEE, 2023) López Torres, Diego; Elosúa Aguado, César; Pappas, Georgios A.; Konstantaki, Maria; Klini, Argyro; Lappas, Alexandros; Arregui San Martín, Francisco Javier; Pissadakis, Stavros; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a zinc oxide (ZnO) out-cladding, overlaid optical fiber Bragg grating sensor, for the detection of vapors of common alcohols and acetone at concentrations lower than 25 ppm while operating at room temperature (RT). The optical fiber sensing results indicate a chemostriction effect occurring in the ZnO layer when exposed to volatile organic compounds (VOCs), which in turn induces shifts in the cladding, and most importantly, in the core confined, Bragg mode. The sensor exhibits a maximum sensitivity of ∼1 pm/ppm to ethanol vapors, with exposure to other alcohol vapors (isopropanol and methanol) showing lower sensitivities; also, response to acetone vapors was traced at ∼0.5 pm/ppm. X-ray diffraction (XRD) measurements of the ZnO nanolayer revealed that, in saturated ethanol vapors atmosphere, the polycrystalline ZnO film undergoes a contraction by 0.6% of the interplanar distance corresponding to the (002) crystalline direction, denoting the chemostrictive effect through an underlying piezotronic mechanism. XRD measurements and optical fiber sensing data are further correlated by numerical simulations carried out, so to study the strain interactions of the ZnO layer with the silica glass optical fiber.
Open Access
Labescape and breakout: gamification for photonics students
(IATED, 2021) Pérez Herrera, Rosa Ana; Tainta Ausejo, Santiago; Elosúa Aguado, César; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Nowadays, the idea of using game mechanisms in non-gaming environments has become of great interest in different fields such as education or training. Not only for primary school but also in higher formal education, game-based learning appears to be an emerging trend in wide-ranging knowledge areas such as health, social policy, or engineering, among others. By employing this methodology, the process of learning becomes more motivating while reaching, in some cases, a competitive level. Game-based learning has been widely adopted in many engineering learning areas, such as for example electronics thanks to the ready availability of low-cost electronic equipment. The authors' extensive teaching experience in subjects related to electronics and photonics has led us to consider its implementation in more ambitious teaching fields. For instance, and despite the broad acceptance, its use in the field of photonics is still very scarce. The high cost of required equipment has hindered the expansion of these strategies, taking its implementation longer than desired and being too expensive at times. In the present work, the authors propose a planning and design scheme for a new gamification strategy based on an escape-room in which, all the tests to be passed will be related to the field of optics and photonics using low-cost equipment. The main field of application of this novel teaching strategy will be in the practical section of the subjects that is usually carried out in a laboratory and will be aimed at both undergraduate and master's degree students. The resolution of tests in different game sequences of the escape room is proposed, that is, linear, open, or multi-linear paths, adapting the degree of difficulty of the tests to the level of the group of students. Additionally, a co-evaluation method is suggested where the rest of the students will provide a valuable feedback to each one of their colleagues.
Open Access
Digital escape room project: engaging electronics for university students
(IEEE, 2024-08-01) Urrutia Azcona, Aitor; Ruete Ibarrola, Leyre; López Torres, Diego; Andueza Unanua, Ángel María; Elosúa Aguado, César; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PINNE2022-UPNA
This work proposes the implementation of a project-based learning methodology for the practical part of digital electronics subjects in the first years of undergraduate studies. Through the project called Digital Escape Room, a series of challenges and exercises are developed in a modular way that the students must solve in order to create a final design in Quartus software and demonstrate it on an FPGA-based device. The implementation of this project has allowed us to see that the academic results and the satisfaction and motivation of the students have improved significantly compared to previous years.
Open Access
Gamification for photonics students: labescape
(MDPI, 2021) Pérez Herrera, Rosa Ana; Tainta Ausejo, Santiago; Elosúa Aguado, César; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The idea of utilizing game elements in non-gaming situations has sparked a lot of attention in recent years, especially in topics such as education and training. Game-based techniques appear to be an increasing trend in a wide range of learning areas, including health, social policy, and engineering, among others, not only in primary school but also in higher formal education. Using this methodology, the learning process becomes more stimulating while also reaching a competitive level in some circumstances. In the present work, the authors propose a new gamification strategy based on an escape-room in which all the puzzles to be passed are related to the area of optics and photonics and use readily available or low-cost equipment. The major field of application of this novel teaching strategy will be the practical section of a course, that is usually carried out in a laboratory, and will be aimed at both undergraduate and master's degree students. A coevaluation method is also proposed where the rest of the students will provide valuable feedback to each one of their colleagues and to the instructor.
Open Access
Straightforward nano patterning on optical fiber for sensors development
(Optical Society of America, 2020) Acha Morrás, Nerea de; Elia Lorente, Victor; Delgado Camón, Arantzazu; Arregui San Martín, Francisco Javier; Elosúa Aguado, César; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua, PI035 BINACS
A simple method to prepare a nano pattern along the surface of an optical fiber is applied in this Letter to develop a pH sensor. The template is made of a block copolymer that defines specific locations where gold nano particles are adsorbed on forming clusters. The average diameter of the resulting agglomerates is 121 nm, and the mean distance between the centers is 182 nm. The morphology of the gold cluster array produces localized surface plasmon resonance. The absorbance spectrum is affected by pH variations, and the ratio between the absorption at two different wavelengths is used to characterize the response, which is repetitive and reversible. This Letter highlights the potentiality of this type of chemical nano patterning for the development of optical fiber sensors.
Open Access
ZnO based, piezotronic optical fiber sensors for tracing volatile organic compounds
(IEEE, 2023-09-04) López Torres, Diego; Elosúa Aguado, César; Pappas, Georgios A.; Konstantaki, Maria; Klini, Argyro; Lappas, Alexandros; Arregui San Martín, Francisco Javier; Pissadakis, Stavros; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
The detection of volatile organic compounds (VOCs) is a major market and research domain, where optical sensing technologies have shown promising advances. Accordingly, ZnO has been extensively used as a transduction material in the sensing of VOCs in the vapour phase, while employing both resistive and optical detection methodologies. ZnO also exhibits significant piezoelectric properties, which in turn have been recently used in the development of piezotronic self-powered, sensing and actuating devices.
Open Access
Optical fiber sensors based on microstructured optical fibers to detect gases and volatile organic compounds: a review
(MDPI, 2020) López Torres, Diego; Elosúa Aguado, César; Arregui San Martín, Francisco Javier; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Estadística, Informática y Matemáticas
Since the first publications related to microstructured optical fibers (MOFs), the development of optical fiber sensors (OFS) based on them has attracted the interest of many research groups because of the market niches that can take advantage of their specific features. Due to their unique structure based on a certain distribution of air holes, MOFs are especially useful for sensing applications: on one hand, the increased coupling of guided modes into the cladding or the holes enhances significantly the interaction with sensing films deposited there; on the other hand, MOF air holes enhance the direct interaction between the light and the analytes that get into in these cavities. Consequently, the sensitivity when detecting liquids, gasses or volatile organic compounds (VOCs) is significantly improved. This paper is focused on the reported sensors that have been developed with MOFs which are applied to detection of gases and VOCs, highlighting the advantages that this type of fiber offers.
Open Access
Nanostructured PbS-doped inorganic film synthesized by sol-gel route
(MDPI, 2022) Nicoara, Adrian Ionut; Eftimie, Mihai; Mihail, Elisa; Vasiliu, Ileana Cristina; Bartha, Cristina; Enculescu, Monica; Filipescu, Mihaela; Elosúa Aguado, César; López Torres, Diego; Sava, Bogdan Alexandru; Oane, Mihai; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
IV-VI semiconductor quantum dots embedded into an inorganic matrix represent nanostructured composite materials with potential application in temperature sensor systems. This study explores the optical, structural, and morphological properties of a novel PbS quantum dots (QDs)- doped inorganic thin film belonging to the Al2O3 -SiO2 -P2O5 system. The film was synthesized by the sol-gel method, spin coating technique, starting from a precursor solution deposited on a glass substrate in a multilayer process, followed by drying of each deposited layer. Crystalline PbS QDs embedded in the inorganic vitreous host matrix formed a nanocomposite material. Specific investigations such as X-ray diffraction (XRD), optical absorbance in the ultraviolet (UV)-visible (Vis)-near infrared (NIR) domain, NIR luminescence, Raman spectroscopy, scanning electron microscopy– energy dispersive X-ray (SEM-EDX), and atomic force microscopy (AFM) were used to obtain a comprehensive characterization of the deposited film. The dimensions of the PbS nanocrystallite phase were corroborated by XRD, SEM-EDX, and AFM results. The luminescence band from 1400 nm follows the luminescence peak of the precursor solution and that of the dopant solution. The emission of the PbS-doped film in the NIR domain is a premise for potential application in temperature sensing systems.
Open Access
Peculiarities of the structural and optical properties of rare-earth-doped phosphate glasses for temperature sensing applications
(Elsevier, 2021) Elisa, M.; Iordache, S.M.; Iordache, A.M.; Vasiliu, Ileana Cristina; Grigorescu, C.E.A.; Sava, Bogdan Alexandru; Boroica, L.; Filip, A.V.; Dinca, M. C.; Bartha, Cristina; Acha Morrás, Nerea de; Elosúa Aguado, César; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Eu, Er, Yb-Er, and Dy-doped phosphate glasses were prepared by a wet-route processing of chemical precursors followed by melt-quenching and annealing. XRD measurements highlighted the amorphous nature of the investigated glasses. UV-Vis absorption spectra revealed peaks specific to f-f electronic transitions of the doping ions whereas FTIR and Raman spectroscopy proved the vitreous network forming role of phosphorous pentoxide. Luminescence spectra in the Vis domain, at RT, showed emission bands characteristic to the ion transitions from the excited states to the ground state. The luminescence spectra collected in the 25-160°C range exhibited a decrease of the emission intensity with temperature rise. In the case of Eu and Dy-doped glasses a relatively small decrease of the emission intensity with temperature is observed by comparison with Er and, respectively, Yb-Er-doped glass where a significant change of the emission intensity is noticed, which recommends the latter as promising candidate for sensing devices.