Σε κλίμα βαθιάς συγκίνησης, την Πέμπτη, 31 Ιουλίου 2025, πραγματοποιήθηκε μονοήμερη εκδήλωση μνήμης προς τιμήν του εξαίρετου και πολυαγαπημένου συναδέλφου και φίλου μας, Κώστα Καλπούζου (https://beaver.iesl.forth.gr/), κατόπιν πρότασης του Επιστημονικού Συμβουλίου.

Ο Κώστας Καλπούζος σπούδασε στο Πανεπιστήμιο του Τορόντο Καναδά, από όπου έλαβε πτυχίο BASc από το τμήμα Εφαρμοσμένης Επιστήμης και Μηχανικών το 1975, πτυχίο BSc από το τμήμα Χημείας το 1978, μεταπτυχιακό πτυχίο ΜSc από το τμήμα Χημείας το 1981 και Διδακτορικό τίτλο (PhD) από το τμήμα Φυσικής το 1987. Τα έτη 1988-1990 εργάστηκε ως επιστημονικός συνεργάτης του ίδιου Πανεπιστημίου και της εταιρίας M.P.B. Technologies Inc., με υποτροφία του National Research Council of Canada.

Το 1990 επέστρεψε στην Ελλάδα και έως το 1992 εργάστηκε ως συμβασιούχος διδάσκων στο τμήμα Φυσικής του Πανεπιστημίου Κρήτης. Επί σειρά ετών, συνέχισε να προσφέρει εθελοντικά διδακτικό έργο και συν-επίβλεψε μία διδακτορική διατριβή. Το 1993 προσελήφθη στο ΙΤΕ-ΙΗΔΛ. Το 1995 εξελέγη ως Ειδικός Λειτουργικός Επιστήμονας Β’ βαθμίδας και το 1999 προήχθη στην Α’ βαθμίδα. Το έργο του, μεταξύ άλλων, περιλάμβανε την ανάπτυξη συστήματος laser οργανικής χρωστικής υπερβραχέων παλμών καθώς και την εγκατάσταση και λειτουργία συστήματος ενισχυτή λέιζερ υπερβραχέων παλμών και σταθμού εργασίας pump-probe μετρήσεων υπερταχέων δυναμικών φαινομένων. Σε ερευνητικό επίπεδο, εργάστηκε σε θέματα υπερταχείας δυναμικής ηλεκτρονίων σε στερεά σώματα και νανοϋλικά, στη επεξεργασία και νανοδόμηση επιφανειών με laser και στην επιστήμη και τεχνολογία αττοδευτερολέπτων.

Ο Κώστας Καλπούζος υπήρξε ακούραστος σύμβουλος, καθοδηγητής και συμπαραστάτης για φοιτητές, μεταδιδακτορικούς, ερευνητές, μέλη ΔΕΠ και διοικητικά στελέχη. Διαδραμάτισε κεντρικό ρόλο σε διοικητικά θέματα του ΙΗΔΛ και στη διαμόρφωση και λειτουργία της ομάδας λέιζερ, ασκώντας στην πράξη καθήκοντα διευθύνοντος συμβούλου. Η συνολική συμβολή του στη διοικητική οργάνωση του ΙΗΔΛ υπήρξε καθοριστική καθώς με τη βαθιά επιστημονική του κατάρτιση και την αφοσίωση του, συνέβαλε ουσιαστικά στη διαμόρφωση της φυσιογνωμίας του ινστιτούτου, αφήνοντας ένα ανεξίτηλο αποτύπωμα στην πορεία του.

Η εκδήλωση πραγματοποιήθηκε στην αίθουσα “Κώστας Φωτάκης” στο κεντρικό κτίριο του ΙΤΕ στις Βούτες Ηρακλείου περιλάμβανε επιστημονικές ομιλίες και διηγήσεις προσωπικών αναμνήσεων από συνεργάτες και φίλους του Κώστα.

Flower-like ZnIn₂S₄/NiAl-LDH/Pt Heterostructures Boost Solar Hydrogen Production

Efficient, Stable, and Scalable Photocatalyst for Clean H₂ Evolution

Researchers at the Institute of Electronic Structure and Laser (IESL–FORTH) and the Department of Environmental Technology, Faculty of Chemistry, University of Gdansk have developed a highly efficient photocatalyst based on ZnIn₂S₄ nanosheets integrated with 3D flower-like NiAl-layered double hydroxide (LDH) and decorated with platinum nanoparticles. This innovative heterostructure demonstrates exceptional performance in photocatalytic hydrogen production under UV-vis and visible light irradiation, providing a green and cost-effective method for solar-driven hydrogen generation.

Performance and Innovation

The catalyst, synthesized via in situ growth of NiAl-LDH microflowers followed by photodeposition of Pt, achieves hydrogen evolution rates up to 1665 μmol g⁻¹ h⁻¹, outperforming pristine ZnIn₂S₄ by nearly 10-fold. The optimized Pt content (1.95 wt%) acts as an active site and electron sink, improving charge separation and enhancing photocatalytic activity.

Experimental techniques, including XRD, HRTEM, PL, XPS, and photoelectrochemical measurements, confirm the formation of a stable and well-contacted heterojunction. A proposed type-II n–n heterojunction mechanism describes efficient charge transfer from NiAl-LDH to ZnIn₂S₄ and subsequent H⁺ reduction on Pt surfaces. The material also demonstrates excellent stability over multiple cycles, with minimal Pt leaching and superior structural resilience.

Future Impact

This research paves the way for the development of low-cost, high-performance photocatalysts using earth-abundant, lead-free materials for sustainable hydrogen production. The ZnIn₂S₄/NiAl/Pt composite holds great promise for applications in solar fuels, green energy technologies, and photocatalytic water splitting systems.

Research and Publication Details

This study was the result of an international collaboration between the Institute of Electronic Structure and Laser – FORTH (Greece), the University of Gdansk (Poland), the Gdansk University of Technology (Poland), and the Institute of Physical Chemistry – Polish Academy of Sciences (Poland).

This work was carried out by Anna Souri (first author), Maria Zografaki at the TCMD laboratory – IESL-FORTH, and Leila Zouridiunder the supervision of Prof. Vassilios Binas (TCMD laboratory – IESL-FORTH). Prof. Binas also holds a position at the Aristotle University of Thessaloniki.

The TCMD – IESL team collaborated closely with Tomasz Klimczuk (Gdansk University of Technology), Kostiantyn Nikiforow (Institute of Physical Chemistry – Polish Academy of Sciences), and Prof. Anna Malankowska (University of Gdansk), combining expertise in material synthesis, structure, and performance evaluation. The project was jointly supervised by Prof. Anna Malankowska and Prof. Vassilios Binas.

Corresponding author from IESL: Prof. Vassilios Binas

Read the full paper:
Dalton Transactions, 2025, 54, 11246–11261
https://doi.org/10.1039/d5dt01018g

Published: July 4, 2025
Journal:Dalton Transactions (RSC Publishing)

Researchers of Transparent and Conductive Materials and Devices Laboratory in IESL/FORTH have developed p-Cu(OH)₂/n-SrTiO₃ heterojunctions for efficient photocatalytic hydrogen production. According to available literature, this is the first study to utilize an STO catalyst decorated with Cu(OH)₂ via a simple photodeposition method as a photocatalyst for hydrogen production under solar iradiation.

Photocatalytic activity and innovation

Flower-like SrTiO₃ photocatalysts decorated with different weight percentages of Cu(OH)₂ (0.1–5 wt.%) were synthesized via a simple solvothermal and photodeposition method. The optimized 1 wt.% Cu(OH)₂/STO exhibited the highest H₂ evolution rate (∼139 μmol h⁻¹; ∼6950 μmol g⁻¹ h⁻¹) under λ> 360 nm, along with excellent stability. The remarkable performance enhancement is attributed to the formation of a well-integrated p–n heterojunction at the Cu(OH)₂/STO interface, which facilitates efficient charge separation and transfer.  This study highlights Cu(OH)₂/STO as an effective photocatalyst for hydrogen production and provides deeper insight into the complex charge-transfer dynamics at these interfaces.

Future impact

This work paves the way for developing highly efficient, stable, and scalable photocatalytic systems for sustainable hydrogen production.

Research and Publication Details

This research work was carried out as part of the postdoctoral research of Evangelia Skliri (first author), in collaboration with Anna P. Souri (PhD), Dr. Ioannis Vamvasakis, Dr. Evangelos Andreou, Prof. Gerasimos Armatas (Department of Materials Science and Engineering), and Prof. Vassilios Binas (Transparent and Conductive Materials and Devices Laboratory – IESL-FORTH; Chemistry Department, Aristotle University of Thessaloniki).

Corresponding authors from IESL: Dr. Evangelia Skliri and Prof. Vassilios Binas

For more details:  https://doi.org/10.1002/adsu.202500127

Cs2AgBiBr6 Perovskites: Designing Stable, Sensitive and Selective Eco-friendly Ozone Sensors

Researchers at the Institute of Electronic Structure and Laser (IESL) have developed a highly selective, eco-friendly ozone sensor, overcoming the critical challenges of selectivity and lead toxicity common in gas sensor technology. The breakthrough involves using lead-free double perovskites (Cs_2​AgBiBr₆​) as the ozone-sensing element, offering a "green" alternative to conventional sensors containing harmful lead.

Performance and Innovation

The new sensor operates efficiently at room temperature with minimal power consumption (0.1 V). It exhibits excellent sensitivity down to a few hundred ppb, a fast response time, and unprecedented selectivity for ozone over other common gases. The research, which merges experimental data with theoretical calculations, provides deep insights into the sensor's active sites and sensing mechanisms. It also highlights the device's remarkable stability over time and its resilience under harsh humidity and temperature conditions.

Future Impact

This work paves the way for developing reliable, low-cost, and environmentally safe sensors for air quality monitoring. It holds significant potential for applications in industrial safety and the Internet of Things (IoT).

Research and Publication Details

This work was part of Aikaterini Argyrou's PhD (first author), in collaboration with Rafaela Maria Giappa and Prof. Ioannis Remediakis (QTM group - University of Crete) for theoretical calculations, and Dr Emmanouil Gagaoudakis and Prof. Vassilios Binas (TCMD laboratory – IESL-FORTH; Prof. Binas also holds a position at the Aristotle University of Thessaloniki) for the gas sensing measurements.

Corresponding authors from IESL: Dr. Konstantinos Brintakis, Dr. Athanasia Kostopoulou, and Dr. Emmanuel Stratakis.

For more details: https://doi.org/10.1002/adsr.202500018

We’re excited to share our latest publication “Spin-Valley Polarization Control in WSe₂ Monolayers using Photochemical Doping”, in Advanced Optical Materials. This outstanding work was carried out by researchers from the Institute of Electronic Structure and Laser (IESL/FORTH) - Eirini Katsipoulaki, Georgios Kopidakis, Emmanuel Stratakis, George Kioseoglou and Ioannis Paradisanos - in collaboration with Konstantinos Mourzidis, Vishwas Jindal, Delphine Lagarde, Xavier Marie from INSA-CNRS (France), Takashi Taniguchi and Kenji Watanabe from the National Institute for Materials Science (Japan), and Mikhail M. Glazov from the Ioffe Institute (Russia).

Summary

This recent study advances our understanding of the exciton spin relaxation in the limit of strong scattering with carriers and control of the spin-valley polarization degree in transition metal dichalcogenide (TMD) monolayers, a key step toward developing valleytronic and optoelectronic applications.

First time observations:

1. New tuning mechanism of spin-valley polarization: a precise, single-shot photochemical doping method eliminates the complexities of electrostatically-gated devices, offering a practical approach for studying valleytronic properties in TMDs.

2. Optical emission readout of the impact of both electrons and holes in the spin-valley relaxation process.

3. Strong tunability of exciton’s circular polarization degree: a threefold modulation was achieved in the carrier density range studied.

Reference

E. Katsipoulaki, K. Mourzidis, V. Jindal, D. Lagarde, T. Taniguchi, K. … & I. (2025). Paradisanos, Spin-Valley Polarization Control in WSe₂ Monolayers using Photochemical Doping. Adv. Optical Mater. 2025, e00575. https://doi.org/10.1002/adom.202500575

Σε κλίμα βαθιάς συγκίνησης πραγματοποιήθηκε σήμερα στο ΙΤΕ, το Επιστημονικό Συμπόσιο «From electrons to elastic and electromagnetic waves” αφιερωμένο στον Καθηγητή Ελευθέριο Ν. Οικονόμου, Προέδρο επί Τιμή του ΙΤΕ, για τη συμπλήρωση των 85 χρόνων του.
 

Ο Καθηγητής Ελευθέριος Οικονόμου υπήρξε πρωτοπόρος, οραματιστής και καθοριστική φυσιογνωμία για την ακαδημαϊκή και ερευνητική κοινότητα της Κρήτης. Από τους δύο πρώτους καθηγητές του Τμήματος Φυσικής και πρώτος Πρόεδρός του, συνέβαλε στην ίδρυση του Τμήματος Επιστήμης και Μηχανικής Υλικών, αλλά και στην ίδρυση του ΙΤΕ, διαμορφώνοντας με ήθος, όραμα και συνέπεια την ταυτότητα της επιστημονικής αριστείας στην Κρήτη και στη χώρα.

Στην εκδήλωση, χαιρετισμό απηύθυναν: ο κ. Γιώργος Ματαλλιωτάκης, Αντιπεριφερειάρχης Διασύνδεσης με Ερευνητικά και Ακαδημαϊκά Ιδρύματα, ο κ. Νίκος Κονταράκης, Εντεταλμένος Σύμβουλος για τη Διασύνδεση με τα Πανεπιστημιακά και Ερευνητικά Ιδρύματα, ο Πρόεδρος του ΙΤΕ καθ. Βασίλης Χαρμανδάρης, η Αντιπρύτανης Ακαδημαϊκών Υποθέσεων, Δια Βίου Μάθησης και Ερευνητικής Πολιτικής Πανεπιστημίου Κρήτης κα Μαρία Βαμβακάκη, και ο Αν. Διευθυντής ΙΗΔΛ, Δρ. Εμμανουήλ Στρατάκης, ενώ η κα Μαρία Καφεσάκη, Καθηγήτρια Τμήματος Επιστήμης και Μηχανικής Υλικών ΠΚ, έκανε ιστορική αναδρομή της σταδιοδρομίας του καθηγητή. Την εκδήλωση συντόνισε ο καθ. Σπύρος Αναστασιάδης, Διακεκριμένο Μέλος του ΙΤΕ και τ. Διευθυντής του ΙΗΔΛ.

Όλοι οι ομιλητές εξήραν το έργο, την ακεραιότητα και το ήθος του Καθηγητή και μίλησαν με θαυμασμό για έναν αληθινό Δάσκαλο – μέντορα, που ενέπνευσε γενιές φοιτητών και συνέβαλε ουσιαστικά στην καθιέρωση της Κρήτης ως κέντρου εκπαίδευσης και έρευνας διεθνούς επιπέδου.
Οι φοιτητές του, με αγάπη και δέος, τον αποκαλούσαν «Θεό», χαρακτηρισμός που υποδηλώνει έναν ακαδημαϊκό δάσκαλο αφοσιωμένο στο έργο του, με βαθύτατη και σφαιρική γνώση του αντικειμένου του, πάντοτε πρόθυμου να τους καθοδηγήσει.
 

Το επιστημονικό μέρος του Συμποσίου εστίασε σε θεματικές σχετικές με την ακαδημαϊκή και ερευνητική σταδιοδρομία του καθηγητή, με συμμετοχή καταξιωμένων επιστημόνων από το εξωτερικό.
 

A new scientific study titled “Laser 3D Micro-/Nano-Structurization of Luminescent Materials”, published in Advanced Optical Materials, presents exciting new findings. The research was led by scientists from the Institute of Electronic Structure and Laser (IESL – FORTH), Elmina Kabouraki, and Maria Farsari, in collaboration with Artūr Harnik, Greta Merkininkaitė, Dimitra Ladika, Arūnas Čiburys, Simas Šakirzanovas, and Mangirdas Malinauskas from Vilnius University.

Overview

The researchers explored various 3D printing techniques for microstructures, focusing particularly on luminescent materials used in applications like bioimaging, microlasers, and micro-LEDs. They noted that traditional manufacturing methods, such as monocrystal growth, tend to be expensive and time-consuming, often involving extensive post-processing. In contrast, laser direct writing was highlighted for its ability to significantly reduce both production time and costs. This method also enables two-photon polymerization, which improves the quality of 3D-printed structures and allows modification of the phosphors’ emission spectrum, thereby expanding their application range. Additionally, the researchers pointed out that laser writing can sometimes be used as a synthesis technique for new compounds. The review covered different 3D printing approaches, types of materials (organic, hybrid, and inorganic), and the fabrication of luminescent microstructures. It emphasized how laser direct writing and 3D lithography open new possibilities for both altering existing luminescent materials and creating novel ones. Overall, the study aimed to highlight successful 3D printing strategies and their potential outcomes, underscoring the innovative applications enabled by these advancements in luminescent materials.

Reference:  Harnik, A. et al. Laser 3D Micro-/Nano-Structurization of Luminescent Materials. Advanced Optical Materials (2025). https://doi.org/10.1002/adom.202500316

The groundbreaking research, titled “Emerging Ta4C3 and Mo2Ti2C3 MXene Nanosheets for Ultrafast Photonics,” published in Advanced Optical Materials, was carried out by scientists at the Institute of Electronic Structure and Laser (IESL – FORTH) - Michalis Stavrou, Maria Farsari, and David Gray - in collaboration with Benjamin Chacon, and Yury Gogotsi from Drexel University, as well as Anna Maria Pappa and Lucia Gemma Delogu from Khalifa University of Science and Technology.

Overview

The researchers found that Ta₄C₃Tₓ and Mo₂Ti₂C₃Tₓ MXenes exhibit exceptional ultrafast nonlinear optical (NLO) properties and carrier dynamics, as investigated using Z-scan and pump-probe optical Kerr effect techniques with femtosecond laser pulses in the visible and infrared ranges. They reported that the NLO responses of these materials surpass those of all previously studied MXenes and most other 2D nanomaterials, reaching remarkably high third-order susceptibility (χ⁽³⁾) values on the order of 10⁻¹³ esu. It was observed that Mo₂Ti₂C₃Tₓ demonstrated the strongest NLO response under both excitation regimes, which was attributed to charge transfer between the Mo and Ti layers in its structure. Under visible excitation, the MXenes showed pronounced saturable absorption, while under infrared excitation, they exhibited strong reverse saturable absorption, enabling effective optical limiting. Additionally, the pump-probe experiments revealed two distinct relaxation processes: a fast one occurring on the sub-picosecond timescale and a slower one a few picoseconds after photoexcitation. The researchers concluded that these MXenes rank among the most powerful NLO materials known, highlighting their significant potential for use in advanced photonic and optoelectronic applications, such as laser technologies, optical protection, telecommunications, and optical or quantum computing.

Reference: Stavrou, M. et al. Emerging Ta4C3 and Mo2Ti2C3 MXene Nanosheets for Ultrafast Photonics. Advanced Optical Materials 13 (2025). https://doi.org/10.1002/adom.202403277

The pioneering study titled “3D micro-devices for enhancing the lateral resolution in optical microscopy” conducted by researchers from the Institute of Electronic Structure and Laser (IESL – FORTH) - Gordon Zyla, Dimitra Ladika, Vasileia Melissinaki, and Maria Farsari - in collaboration with Göran Maconi, Anton Nolvi, Ari Salmi and Ivan Kassamakov from the University of Helsinki, as well as Jan Marx from Ruhr University Bochum, was selected as Outstanding Paper by Light: Advanced Manufacturing in 2024.

Overview

The researchers found that optical microscopy, while widely utilized, faces intrinsic limitations in lateral resolution due to light diffraction. To overcome this, they developed a novel 3D micro-device incorporating a dielectric micro-sphere, which is known to enhance resolution through photonic nanojets. They explained that their device consisted of a micro-sphere supported by a cantilever above a micro-hole in a modified coverslip, making it compatible with standard optical microscopes.

They reported using femtosecond laser ablation to create the micro-hole and multi-photon lithography to fabricate the micro-sphere and cantilever with high precision. According to their findings, a Zr-based hybrid photoresist enabled the creation of a nearly perfect micro-sphere with a surface roughness of λ/8. The team evaluated the performance of the micro-device using Mirau-type coherence scanning interferometry and white light illumination at 600 nm. They observed that the device significantly improved lateral resolution beyond the diffraction limit while preserving the axial resolution, as confirmed through calibration and simulations.

Reference: Gordon Zyla, Göran Maconi, Anton Nolvi, Jan Marx, Dimitra Ladika, Ari Salmi, Vasileia Melissinaki, Ivan Kassamakov, Maria Farsari. 3D micro-devices for enhancing the lateral resolution in optical microscopy[J]. Light: Advanced Manufacturing 5, 17(2024). doi: 10.37188/lam.2024.019

The theoretical and experimental study, titled "Double-Pulse Femtosecond Laser Fabrication of Highly Ordered Periodic Structures on Au Thin Films Enabling Low-Cost Plasmonic Applications," published in ACS Nano, showcases pioneering research carried out by scientists from the Institute of Electronic Structure and Laser (IESL) at FORTH - Fotis Fraggelakis, Panagiotis Lingos, George D. Tsibidis, and Emmanuel Stratakis - in collaboration with  Emma Cusworth, Nicholas Kay, Laura Fumagalli, Vasyl G. Kravets, and Alexander N. Grigorenko from Manchester University and Andrei V. Kabashin from Aix Marseille University.

Overview and Results

The researchers proposed a novel technique involving double femtosecond pulse (~170 fs) laser-assisted structuring to fabricate periodic plasmonic arrays on thin (~32 nm) gold films deposited on glass substrates. These arrays enable the excitation of surface lattice resonances (SLRs) or quasi-resonant features, which are highly valuable for biosensing and other applications. Traditional methods for producing such structures over large areas, such as electron beam lithography, are typically expensive and time-consuming, limiting their practical use.

In their study, the team demonstrated a single-step process that produces homogeneous and highly ordered laser-induced periodic surface structures (LIPSS) over large areas. Their experimental findings highlighted the critical role of the interpulse delay between the two laser pulses, identifying it as the key parameter that determines the uniformity and order of the resulting structures.

Theoretical modeling supported the experimental observations and provided important insights into the underlying mechanism of structure formation. Furthermore, ellipsometric measurements revealed that these LIPSS exhibit strong plasmonic behavior, including ultranarrow resonances linked to diffraction-coupled SLRs—features particularly important for biosensing and other applications.

Overall, the researchers demonstrated that femtosecond double-pulse laser structuring offers a promising, low-cost approach for large-scale fabrication of highly ordered and functional plasmonic structures.

Corresponding authors from IESL: Dr. Fotis Fraggelakis - Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH),

Dr. Emmanuel Stratakis - Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH) & Department of Physics, University of Crete

More details: https://doi.org/10.1021/acsnano.5c06177