Reliable quantum channels, based on, for example, spin chains, are indispensable for achieving scalable and efficient quantum information processing and communication in systems with fixed qubit positions and finite-range interqubit interactions. We have studied several protocols for complete state or excitation transfer in static and dynamic spin chains and examined their speed and sensitivity to diagonal (Z) and off-diagonal disorder (XY). In particular, we have found that, for a given chain length and maximal achievable interspin exchange coupling strength, the optimal static spin-coupling protocol, implementing the fastest state transfer between the two ends of the chain, is more susceptible to off-diagonal disorder, as compared to a much slower but robust adiabatic transfer protocol with time-dependent coupling strengths. Our results have important implications for attaining scalability in many envisaged quantum information processing platforms.

The measurement of (single-pass) chiral optical rotation and circular dichroism is the most widely used method for chirality sensing, and is of fundamental importance to many fields. However, these chiral signals are typically very weak, and their measurement is limited by larger time-dependent backgrounds (such as spurious birefringence) and by imperfect and slow subtraction procedures. Using a novel bow-tie cavity with an intracavity Faraday Effect, we demonstrate three important improvements: (a) the enhancement of the chiral optical rotation angle by the number of the cavity passes (typically 1000); (b) the suppression of birefringent backgrounds; and (c) the ability to reverse the sign of the chiral signal rapidly, allowing the isolation of the chiral signal from backgrounds. Using chiral cavity ring-down polarimetry, we have demonstrated the measurement of chiral optical rotation in high-noise environments, such as for open-air gas samples, and for chiral liquids in the evanescent wave produced by total internal reflection at a prism surface. We discuss new fields of application of chiral sensing and of cavity ring-down ellispometry, and report progress towards the measurement of parity nonconserving optical rotation in atomic iodine at 1315 nm.

We describe the production of highly spin-polarized deuterium (SPD) atoms from the photodissociation of deuterium iodide (DI) using circularly-polarized 270-nm light. This source of SPD has the potential to surpass the production rates and densities of conventional methods of SPD production by many orders of magnitude, and we describe proposals to use this source to measure polarized laser fusion of D-T, D-3He, and D-D reactions.

The Attosecond Science and Technology laboratory focuses on the generation, characterization and applications of intense Extreme Ultraviolet (XUV) radiation emitted in the form of attosecond (I asec = 10-18 sec) pulses. It targets on the development, upgrades and running of a state of the art table top attosecond facility dedicated to the investigation of ultrafast dynamics in all states of matter, as well as non-linear and strong field phenomena induced solely by the XUV radiation. Here, we present an overview of the latest results on I) the physics underlying the XUV generation process in gas phase media; II) the generation of intense attosecond XUV pulses and III) the applications in 1-fs time scale dynamics of atoms and molecules.

At temperatures just a few tens of nano Kelvin above absolute zero, (-273.15 C) atoms can form a so-called Bose-Einstein Condensate (BEC), where many atoms join to form one single wave-like quantum state. These states are amongst the largest quantum objects that we can produce and precisely control to date.

At IESL, we are developing table-top matterwave interferometers. In this poster, we will present novel atom-traps and ultra-smooth waveguides to for these unique quantum states. We will also show, how we plan to use these to construct novel matter-wave lasers and perform matter-wave interferometry

Matter-Wave interferometers are already amongst the most precise measurement devices available to date. In this poster, we present our recent efforts use atom-interferometry to measure gravitational waves (ELGAR) and to test Einstein’s weak equivalence principle (STE-QUEST).

STE-QUEST: Einstein postulated that the accelerational and gravitational masses should be the same. Even tiny violations of this principle would result have profound impact on our understanding of physics. The proposed mission of the European Space Agency (STE-QUEST) will use two synchronous atom-interferometers on a satellite, to compare the gravitational and accelerational mass of Rubidium and Potassium atoms.

ELGAR : High-Frequency gravitational waves have recently been detected for the first time using a very large laser-interferometer. LISA will be able to detect these waves at very low frequencies. This poster will show, how we plan to use many coupled matter-wave interferometers to measure gravitational waves also at intermediate frequencies.

Στο Ινστιτούτο Ηλεκτρονικής Δομής και Λέιζερ του ΙΤΕ, μελετούμε με μια διαφορετική προσέγγιση την γρήγορη καταγραφή των χαρακτηριστικών ουσιών που εμπεριέχονται σε δείγματα τροφίμων με ελάχιστη ή χωρίς επεξεργασία. Βασιζόμαστε στην τεχνογνωσία μας στον τομέα της αλληλεπίδρασης του φωτός με την υλη και στην ανάπτυξη εξειδικευμένων οπτικών φασματοσκοπικών μεθόδων ανάλυσης (όπως π.χ. τεχνικές απορρόφησης φωτός και φθορισμού). Έτσι, μπορούμε να καταγράψουμε το οπτικό φάσμα που αποτελεί το χαρακτηριστικό «αποτύπωμα» και αντικατοπτρίζει την χημική σύσταση ενός δείγματος. Διαφορετικά δείγματα έχουν διαφορετικό αποτύπωμα και αυτές οι διαφορές ή οι ομοιότητες χρησιμοποιούνται για:

Την ταυτοποίηση,
Τον έλεγχο προέλευσης και ποιότητας.

Οι τεχνικές αυτές είναι γρήγορες και κατά πολύ «φτηνότερες» από τις χρονοβόρες και υψηλού κόστους κλασικές αναλυτικές τεχνικές.

Μελετήσαμε:

Τοπικές Ποικιλίες Κρασιών
- Διερεύνηση και αξιολόγηση των παραγόντων παλαίωσης ερυθρών (Κοτσιφάλι, Μαντηλάρι) και λευκών (Βηλάνα, Δαφνί) οίνων από κρητικές ποικιλίες.

Κρητικό Ελαιόλαδο
- Διαχωρισμός δειγμάτων από κρητικές ποικιλίες Κορωνέικη, τσουνάτη, χοντρολιά
- Ταυτοποίηση ποιοτικού ελαιολάδου από κρητικές επιχειρήσεις
- Μελέτες νοθείας εξαιρετικά παρθένου ελαιολάδου με σπορέλαια

Nonlinear microscopy techniques are at the forefront of biomedical research over the last decade. These non destructive modalities offer improved resolution, high contrast images with increased penetration depth and complementary information while minimizing phototoxicity and photodamage effects on the biological samples. These properties characterize them as perfect imaging tools for revealing valuable and unique information of the specimen under investigation. These techniques are not limited to visualization since they also permit precise quantitative analysis and testing of specific mechanisms and biological processes. The imaging modalities of MPEF, SHG and THG have been successfully employed for the in vivo sub-cellular investigation of complex biological activities (embryogenesis, neuronal degeneration, aging, cell activation and differentiation) and the extraction of structural and morphological information from various samples (cancer cell lines, mouse embryos, C. elegans, BV-2 microglia cells, T cells, cancer tissue).

Micro- and nano- fabrication techniques provide the opportunity to develop novel 3D cell culture platforms, where the effect of various topographical cues on neuronal proliferation, orientation, adhesion and differentiation is studied. Biomaterial architecture can drive cellular response via physical and chemical extracellular signals (topographical and chemical cues at micro/nanoscale), mechanical properties of the substrate and adhesion ligands. Such tuning multiple cell instructive cues via micro/nano structuring is significant in Neural Tissue Engineering.
Our research focuses on the hierarchical micro/nano texturing on silicon (Si) via ultrashort-pulsed laser irradiation. We have demonstrated that microconical Si substrates of different roughness may influence the properties of multiple central (CNS) and peripheral (PNS) nervous system neurons and neuronal cell lines as well as direct the alignment of the neuronal network. In particular, it has been shown that the geometrical characteristics of the microcones alone inhibit neuronal differentiation in the PC12 (NGF-induced) and the Neuro-2a (retinoic acid-induced) cells. They also affect cell adhesion and proliferation of the N2a cells. Moreover, we have shown that both Schwann cells and axons of sympathetic neurons are parallel oriented onto micrcocone patterns of elliptical shape, while they exhibited a random orientation onto the microcones of arbitrary shape. This topography-induced guidance effect was also observed in more complex cell culture systems, such as the organotypic culture whole dorsal root ganglia (DRG) explants as well as in primary mouse cortical neuron cultures. In addition, the roughness of the microconical substrates appears to affect the growth and the proliferation of Neural Stem cells (NSCs) and concurrently delay the maturation of the derived neurons once differentiation is induced.

Introduction: Cells in general take decisions on survival, proliferation, alignment and migration depending on the stimuli relative to their surrounding environment (cellular-substrate interface). The extracellular matrix (ECM) provides the necessary cues at micro and nano-scale for the cells phenotype maintenance (adhesion, orientation/alignment, proliferation and differentiation). In the tissue, which is a complex multilayer environment, there are important features to be considered in order to design and develop a structure in terms of topography, morphology, chemistry and scale. Ultrafast pulsed laser irradiation is considered as a simple and effective method to fabricate structures over a large area with the main advantage of the control in the structure geometry and pattern regularity.
Another significant issue to be taken into consideration is the role of static vs dynamic conditions at the cellular-substrate environment. Dynamic cultures realized with the aid of microfluidics reflect more appropriately the in vivo environment of cells in tissues such as the normal fluid flow within the body, consistent nutrient delivery, effective waste removal and mechanical stimulation due to fluid shear forces.
Objectives: In this study, a series of micropatterned silicon (Si) and PETG (polyethylene terephthalate glycol-modified) structures were fabricated by using the ultrashort laser irradiation in order to assess the selective cellular adhesion, proliferation and alignment. Positive replicas on different biodegradable polymers have been successfully reproduced via soft lithography. A comparison of the role of topography, chemistry and stiffness of the substrates (Si vs polymeric) on the cellular responses was achieved. Furthermore a novel microfluidic platform was fabricated in order to assess the combined effect of fluid shear forces and culture substrate morphology on cell proliferation and directionality.
Materials & Methods: Micropatterned Si and PETG structures were fabricated via ultrafast laser irradiation respectively at a range of fluences, resulting in different roughness and geometrical characteristics. Positive replicas on biodegradable polymer poly(lactide-co-glycolide) and a copolymer poly-lactide-co-caprolactone have been successfully reproduced via soft lithography. The morphological characterization of all the substrates was performed by Scanning Electron Microscopy (SEM). The cytocompatibility evaluation of all the substrates was firstly achieved with NIH 3T3 murine fibroblasts, and then with SW10s and N2a neuronal cell lines. Furthermore, dynamic cultures were performed on the PETG substrates for the study of the cytoskeleton, alignment and proliferation of cells.
Results & Discussion: A successful fabrication of the micropatterned substrates was accomplished via ultrafast laser irradiation and soft lithography. All the different cell types attached strongly and proliferated on the substrates. Surface topography affected Schwann cells and fibroblasts but not N2a cells. Moreover, cells appeared to be oriented along the direction of the lines and spikes. Finally, under flow conditions combined with the lines, Schwann cells appeared to be oriented along the direction of the lines and parallel to flow. The ability of this micropatterned strategy to control the cellular adhesion and growth and thus to engineer cell alignment in vitro could be potentially useful in the field of regenerative medicine and tissue engineering.

In the last decade or so, perovskite solar cells (PSCs) have gained remarkable scientific attention due to their rapidly boosted power conversion efficiency (PCE) and relatively low cost of device fabrication, while continuous research efforts are focused on further enhancing the photovoltaic characteristics of such devices. Based on this, we herein present recent findings on the fabrication of different perovskite-based complex systems in order to enhance photovoltaic performance and stability. According to this, three different perovskites-based systems are investigated in the ULMNP laboratory:
-Organometal Halide Perovskites in film form. Perovskite absorber films from this type of perovskites have been fabricated following laser-assisted crystallization techniques for photovoltaic applications. Laser annealing crystallization approach enhances further the PCE compared to typical thermal annealing procedures.
-All inorganic lead halide Nanocrystals. Nanocrystals of different morphologies have been synthesized by colloidal chemistry methods for the intercalation in the active layer. The nanoparticulate semiconducting structures are unique electronic materials, exhibiting electronic structures and optoelectronic properties that are size- and shape- dependent.
-Intercalation of all inorganic lead halide nanocrystals in polymeric matrixes. Nanocrystals of such semiconducting materials are homogeneous introduced in thin polymeric matrixes and gas doping procedures have been evaluated to modify the absorption spectrum in the spectral range suitable for photovoltaic applications.
The morphology, the size and the chemical structure are extracted from HRTEM experiments. Photoluminescence and pump probe techniques are employed also in these systems to understand the optoelectronic properties and the relaxation dynamics behind, in order to decide the more effective morphology for photovoltaic applications.

The interest in two-dimensional (2D) materials has been steadily increasing since the discovery of graphene, a material with fascinating properties and great potential for various applications. Transition metal dichalcogenides (TMDs) with the form MX2 (M=Mo, W, Ti, etc., and X=S, Se, Te) exhibit a structure very similar to that of graphene and have attracted significant attention of the scientific community due to their extraordinary physical properties.
Here, we report on the extraordinary photoluminescence (PL) and Raman properties, not only of the physical but also of intentionally created via femtosecond laser ablation, boundaries of mechanically exfoliated WS2 monolayers. Specifically, the PL emission is significantly enhanced at the monolayer’s edges compared to their inner parts. Such a PL Enhancement is attributed to the pronounced oxygen chemisorption and physisorption at the edges, which affects the spatial distribution between different exciton complexes (i.e. neutral excitons and trions) in monolayer WS2, giving rise to spatial non-uniformity of the electron density across the monolayer surface. Besides excitons and trions, we report on the existence of bound quasiparticles that individually consist of two electron-hole pairs, known as biexcitons, in WS2 flakes from 78K up to room temperature.
In addition, a fast photochemical doping technique that can sufficiently control the carrier density and consequently the PL emission of WS2 single layers by incorporating Cl atoms on the monolayer’s surface, is demonstrated. Controllable irradiation of WS2 monolayers with UV nanosecond pulses in rich Cl2 environment, can affect the emission energy of the excitons. Specifically, a maximum red shift of 15meV for the neutral exciton (X0) can be achieved. This is an indication that Cl2 acts as a p-type dopant in WS2 and results to a reduction of its Fermi level. The results represent unique prospects towards engineering of specialized electronic devices based on WS2 and other TMD monolayers.
Furthermore, we use nonlinear laser-scanning optical microscopy in atomically thin transition-metal dichalcogenides (TMDs) to reveal, with high-resolution, information about the orientational distribution of armchair directions and their degree of organization in the two-dimensional (2D) crystal lattice.  In particular, polarization resolved second harmonic generation (PSHG) imaging in monolayer WS2 reveal with high-precision the orientation of the main crystallographic axis (armchair), from every pixel of the 2D material. By performing, for the first time, a pixel-by-pixel mapping of the armchair orientations of WS2 triangular islands on a large CVD-grown sample area, we are able to distinguish between different domains, locate their boundaries and reveal their fine structure. To do that, we fit experimental PSHG images of sub-micron resolution into a generalized theoretical model and we acquire the armchair orientation for every pixel of the material. This allows us to measure the mean orientational average of armchair angle distributions from specific regions of interest and consequently to define the standard deviation (σ) as a crystal quality factor. Small values of σ reflect a crystal of high quality.
Finally, the synthesis of WS2 and MoS2 nanostructures (such as MoS2 fullerene-like NPs and WS2 INTs) through ultrashort-pulse laser irradiation of the bulk material under ambient conditions is demonstrated. The presented method is performed in ambient air and without use of any toxic precursor gases, making it a simple and environmentally friendly approach to obtaining high-quality inorganic nanostructures. Our results suggest that one can use a scanning laser beam for the formation of inorganic nanostructures at any preselected location and on temperature-sensitive plastic substrates, which is destined to numerous applications, including formation of miniaturized electronic devices or tips for electron emission and scanning probe microscopy.

Nature has always provided a plethora of functional surfaces exhibiting unique, complex hierarchical morphologies with dimensions of features ranging from the macroscale to the nanoscale. Such morphologies are always behind the superior properties exhibited by the natural surfaces, including extreme wetting, floatation, adhesion, friction and mechanical strength. 
In principle, femtosecond laser induced surface structuring has been demonstrated to produce numerous biomimetic structures for a range of applications, including microfluidics, tribology, tissue engineering and advanced optics.  The complex structure of most of the natural surfaces has been proven to be extremely difficult to mimic. 
In this poster, we present a summary of the research activities by the ULMNP group towards producing biomimetic self-assembled structures of variable shape and periodicity (i.e. ripples, grooves, spikes, more complex structures, etc.) on various types of materials (metals, semiconductors, dielectrics). The primary objectives of the research work aims to (i) enhance our knowledge of the physical mechanisms that are related to the development of the aforementioned complex structures through a combined experimental/theoretical approach of the fundamental mechanisms that characterise lasermatter interaction, (ii) allow a systematic investigation of the laser conditions (i.e. fluence, wavelength, irradiation dosage, pulse duration, polarisation) that lead to structures with application-based and preferential opto-wetting features (i.e. antireflection and extreme wetting properties) and tribological properties, (iii) provide an analytical exploration of the opto-wetting properties and correlate these features with the morphological characteristics of the induced structures.
A key element of the research work is the development of a novel multi-scale theoretical model that describes fundamental physical processes after laser irradiation of the solid. The model incorporates components related to: electrodynamics, surface plasmon excitation, relaxation mechanisms, phase transitions, fluid dynamics and thermomechanical effects. The model does not only allow the development of state-of-the art experimental designs dictated by theoretical predictions but it can also be regarded as an important predictive tool for laser-based manufacturing.
Our results demonstrate that the fs-based processing of solids constitutes an efficient and robust technique towards the production of highly-ordered, multidirectional, and complex biomimetic structures. Furthermore, the fabrication of a plethora of complex structures by varying the laser beam parameters brings about a new concept in laser structuring and it can be considered as an emerging laser based fabrication technique.

Hydrogels are widely used as scaffolds for cell growth due to their chemical and physical properties, which mimic the extracellular matrix of natural tissue. Control of the microarchitecture in hydrogels scaffolds for tissue engineering (TE) applications is crucial point which can be achieved through direct laser writing (DLW) with two photon polymerization (TPP). The DLW technique is based on the localized cross-linking of the photosensitive materials induced by femtosecont laser pulses. Generally, in TPP the presence of the photoinitiator (PI) is necessary to initiate the polymerization. The use of PI, has toxic side effects, for biological applications, as several studies have demonstrated the cytotoxicity, at various rates, of PI and their derived radicals.
In the present work, to our best knowledge, we firstly report PI free TPP of chemically modified photosensitive gelatin (GelMA). We synthesized the photosensitive gelatin, and fabricated three dimensional structures. In vitro cell cultivation shows the excellent biocompatibility of GelMA, as was expected, and the creation of 3D cell culture.

EXPERIMENTAL METHODS:
Gelatin was chemically modified using methacrylic anhydride (MAA) to introduce photosensitive methacrylamide groups along the polymer chain. In order to characterize the synthesized material, 1H NMR spectroscopy and ninhydrin assay, were used.
Three-dimensional structuring of the GelMA was carried out by two photon polymerization using a femtosecond laser at 520 nm and a repetition rate of 1 MHz, in the absence of a photoinitiator.
Finally, the NIH-3T3 cells behavior on the 3D scaffolds was studied by an immunocytochemistry assay.

RESULTS AND DISCUSSION:
The successful modification of gelatin to bear the methacrylamide groups was verified by 1H NMR spectroscopy. The appearance of new signals in the spectrum of the modified polymer, verify the successful functionalization of the gelatin molecules.
The degree of substitution, defined as the percentage of modified ε-amino groups and it calculated at 70%
The absorption spectrum of gelatin, which exhibits maximum peak at 260nm, enabled the PI-free polymerization. After chemicaly modifying the gelatin with MAA, the absorption spectrum increases, at the certain wavelength. To confirm that the peak’s increase is due to acrylamide groups, the absorption spectrum of N-isopropylacrylamide was measured and found to absorb at the same wavelength range. Therefore, enriching gelatin with methacrylamide groups increases the absorption at 260nm. Since the laser’s operation is at 520nm, we believe that the peptide bond is stimulated upon the absorption of the two photons and hence the energy transfer causes the double bond to break and induces polymerization.
Figure 2 shows the 3D structures fabricated by two photon polymerization using modified gelatin as the photosensitive material without a photoinitiator. Well-defined structures with all details and dimensions imprinted in the structures were obtained.
Finally, cell adhesion and proliferation on the 3D scaffolds was assessed by immunocytochemistry using actin and nucleus staining. The cells were cultured in all three dimensions on the scaffolds and were uniformly distributed on the structures.

CONCLUSION:
In summary, photopolymerizable gelatin with a high degree of modification has been prepared. We report for the first time the 3D photopolymerization of the modified gelatin without a photoinitiator to fabricate well defined 3D scaffolds for tissue engineering. The material is not toxic and supports an excellent cell adhesion and proliferation on the 3D scaffolds.

An overview of several types of optical fibre sensors targeting medical applications that have been developed in the Photonic Materials and Devices Laboratory (PMDL) of IESL will be presented. Examples include, a compact, flexible shear sensing pad, based on the fusion of microstructured optical fibers and magneto fluidic technologies, for tracing shear skin deformations underlying pressure ulcers. The sensor can detect 1D and 2D shear stress displacements in the range between 100 μm to 4.25 mm, in static and dynamic mode up to 5Hz. Additionally, results will be presented on the laser inscription and dissolution study of advanced Bragg gratings in a bioresorbable, phosphate glass optical fiber. Such phosphate glass fiber Bragg gratings could be instrumental in the development of single-use, photonic sensing probes, for the efficient monitoring of vital mechanical or chemical parameters while being implemented into-the-human-body. Furthermore, the performance enhancement of a new all-optical applicator for tumor laser ablation treatment, through the incorporation of built in temperature Bragg grating sensors, will be described. Finally, it will be shown how the combination of long period gratings and engineered over layers can lead to specific sensing probes with medically related application in humidity sensing, vapors detection and UV dosage monitoring.

An overview of several types of optical fibre sensors targeting industrial applications that have been developed in the Photonic Materials and Devices Laboratory (PMDL) of IESL will be presented. Examples include, several types of magnetic field meters developed in D-shaped optical fibers, silica glass microstructured optical fibers and in PMMA polymer microstructured optical fibers. All magnetic field meters developed exhibit azimuthal sensitivity to magnetic field, being capable of measuring not only the flux of the magnetic field (from few Gauss to KGauss range) but also the direction of its application. Applications include electrical power transmission devices and electrical transformation plans. Other examples of advanced optical fiber sensors include miniaturized optical fiber endface probes developed using non-linear laser lithography for the selective sensing of both gas (organic vapors) and oily samples, with applications in ambient air quality control, industrial safety and food industry, respectively. Sensitivities of the last devices reach minimum levels of 2ppm into the detection of chlorinated ethanes.

A novel, non-invasive methodology based on the photoacoustic effect is introduced in the context of artwork diagnostics with emphasis on the uncovering of hidden features in paintings, as well as, the on-line monitoring of laser cleaning processes in stonework. According to the photoacoustic effect, when light of time-variable intensity (e.g. a laser pulse) is absorbed by a material, the thermoelastic expansion of the medium will give rise to a rapid pressure change, which propagates in the form of acoustic waves into the surrounding environment. A piezoelectric detector is typically used to detect a part of the emitted acoustic energy, usually in the MHz regime, to reveal the optical absorption magnitude for the selected irradiation wavelength.
The first part of this work focuses on the capabilities of photoacoustic imaging in artwork diagnostics, by demonstrating the detection of hidden underdrawings in miniature oil paintings on canvas. Having over three orders of magnitude higher transmission through strongly scattering media, compared to light in the visible and near infrared, the photoacoustic signal offers substantially improved detection sensitivity and achieves excellent optical absorption contrast at high spatial resolution. On the other hand, the second part of this work presents the high potential of photoacoustic signal detection on the monitoring of laser cleaning in terms of material removal and determination of the substrate’s damage threshold. To investigate this possibility, a simple and straightforward case application of laser cleaning has been considered; namely the removal of black graffiti from medium coarse white marble.
It is anticipated that photoacoustic diagnosis will further attract the interest of the cultural heritage science community, paving the way for more relative contributions in this new research field.

The chemical composition of carbonate shell from palaeoecological and archaeological assemblages is laborious to analyse, yet the information that is locked within the tens of thousands of shell deposits worldwide contains valuable insights on past environments and human ecology. At present, studies struggle with the acquisition of sufficient amounts of data to make robust interpretations. Large amounts of information is inaccessible due to costly and time-intensive techniques, resulting in small, unrepresentative studies and a lack of comparability between them. Here we develop the technique of Laser Induced Breakdown Spectroscopy (LIBS), which will allow rapid chemical analyses of carbonates, increasing the cost efficiency by a factor of 20, resulting in more comprehensive datasets. We apply the technique to various molluscan species around the world, to develop a rapid and affordable method and to globally advance the reconstruction of climate change, exploitation of coastal resources and human-landscape interactions. Similarly, the lower costs and higher speed of sample acquisition enables an extensive multi elemental analysis of shell structures of a larger set of mollusc specimens and may give insights into the mechanisms of shell carbonate precipitation. ACCELERATE (www.accelerate-project.com) is a Marie Skłodowska Curie IF-Project.

In recent years complex diagnostic and restoration problems have been efficiently approached by means of laser techniques. In fact a number of laser material processing and spectroscopic methods has been specifically adapted with exceptional success to the requirements of a wide range of demanding archaeometric questions and conservation challenges.
An overview of the latest advances related to laser analytical, diagnostic and cleaning research and applications undertaken by the “Photonics for Cultural Heritage” group of IESL-FORTH will be presented. Specifically, cleaning methodologies involving innovative or prototype laser systems investigated and applied with the aim to approach delicate conservation challenges (multicomponent and/or ultrathin objects) will be discussed, together with versatile, user-friendly, compact and portable analytical instrumentation exploited and developed in order to enable chemical analysis of cultural heritage materials in-situ at Museum or excavation site environments. In parallel research towards reliable and effective assessment and monitoring of the ablation process using innovative optical and laser spectroscopic imaging and diagnostics will be also shown. Final, the OPTO-CH series of summer workshops, established in 2012, with the aim to offer young scientists and conservators specialised training on the use of these novel tools and methodologies, will be also presented.
The above activities are a major component (IPERION-CH.gr) of the cross-disciplinary National Research Infrastructure (RI) “Hellas-CH”, with the mission to offer access to versatile integrated tools and technologies for addressing demanding research challenges in the field of CH science. In this respect, the participation of the “Photonics for Cultural Heritage” group of IESL-FORTH to the EU RIs “IPERION-CH” and “E-RIHS” significantly enhances its role as regards research and applications in the field.

Rod-shaped particles are ideal anisotropic systems for studying the isotropic-nematic-smectic phase transitions. Micron-sized silica rods have been extensively employed as model particles in the investigation of such colloidal phase transitions, because of their facile synthesis which also enables their labelling with fluorescent dyes and the ability to visualize them using an optical microscope. However, one of the main drawbacks of these particles is their high density (d ~ 2 g/mL) which leads to the fast sedimentation of the colloids in common solvents such as ethanol, water, etc and renders the density matching of the system very challenging.
In this work, we describe the synthesis of core shell rods, using a template-assisted hydrolysis-condensation method to grow a titanium dioxide shell onto silica rod particles. The challenge of this synthesis is to obtain only individual coated rods, without any particle aggregation or side-nucleation. The importance of the surface state for the success of the reaction is highlighted, and the key parameters controlling the coating thickness are identified.
The silica core is then etched with a concentrated sodium hydroxide aqueous solution, to yield hollow titanium dioxide shells of significantly lower density compared to the bulk density of titanium dioxide. The success of the synthesis is assessed using electron microscopy. The porosity and density of the titanium dioxide shell are investigated, as well as the sedimentation behaviour of the hollow rods.

Polymer materials are often filled with inorganics to improve their properties. The cases in which the additive exist in the form of a fine nm-sized dispersion within the polymeric matrix, thus producing a nanocomposite, allow the investigation of basic scientific problems. At the same time, these materials are utilized in a variety of applications. The control of the structure in polymer-inorganic nanocomposites by understanding and/or altering the interactions between the chains and the surfaces has been demonstrated. Further than the dispersion and the structure of the inorganic material within the nanohybrid, the polymer structure, morphology, crystallinity and chain conformation in the presence of the inorganic material and/or in the proximity of the surfaces is of equal importance. Different additives of varying size and geometry, as well as different compositions have been utilized to probe the effect of the interactions and of the confining length. Moreover, polymer dynamics close to surfaces or when chains are restricted in space can be very different from that in the bulk. Different polymer relaxation processes from the very local methyl rotation or the dielectrically active β and γ relaxations, to the phenyl flip and up to the segmental motion in the bulk and in the close proximity of an inorganic surface or under severe confinement have been investigated. Polymers with different hydrophillicity, functional groups and / or different architectures as well as different inorganic additives have been utilized to investigate the influence of the interactions between the constituents and the geometry and size of the additive on the dynamics.

The isolation of atomically thin sheets from layered materials has generated enormous interest in two-dimensional (2D) crystals. Single layers cleaved from materials such as graphite, boron nitride, and molybdenum disulfide (MoS2) have been studied extensively, both experimentally and theoretically. 2D MoS2 and other semiconducting Transition Metal Dichalgogenides (TMDs) exhibit novel optoelectronic properties, different from their bulk counterparts. Similar to graphite, TMDs layered 3D structure allows for the extraction of single or few layers but unlike gapless graphene, 2D TMDs possess a direct electronic energy bandgap. Their unique optoelectronic properties depend on composition, dimensionality, strain, defects, chemical modification and nanostructuring, so that they can be engineered for specific applications. When combined with graphene and/or other materials, TMDs offer new possibilities in nanotechnology. Transistors, solar cells, light-emitting devices, sensors, and inexpensive catalysts are some of the technological applications currently explored using these materials. Great progress in a relatively short period of time has created many fundamental and practical issues and a lot of effort is being put into resolving them. In this effort, theory, modelling and simulation play a crucial role. Detailed understanding of the atomic structure, electronic properties and their manifestation in observable quantities, provides interpretation to experiments and predictions for the functionality of 2D materials and nanostructures. We present theoretical results based on Density Functional Theory calculations for the modification of the electronic and dielectric properties of TMD monolayers under strain for nanoribbons and nanoflakes with metallic edge states for hybrid TMD/graphene nanostructures and the substrate induced changes of their optoelectronic and catalytic properties and for TMD alloys in order to examine the possibility of continuously tuning the bandgap. Engineering the electronic properties of these materials may enable their widespread use in applications.

The last decades have been characterized by immense industrial advances, leading to a demand for effectual treatment methods capable of removing hazardous substances from wastewater. Towards this direction, heterogeneous photocatalysis is a promising alternative to conventional treatments, demonstrating high efficacy for oxidizing pollutants. TiO2 has been the catalyst of choice for a wide range of photocatalytic applications, however, the maximization of its efficiency is inhibited by its low band gap that limits the exploitation of solar energy and its high recombination rate of photoinduced charge carriers. Numerous efforts have been conducted for the improvement of its performance and among them coupling with other semiconductors has been the subject of intensive research.
In this context, the modification of TiO2 with graphitic carbon nitride (g-C3N4) has been proposed. g-C3N4 is a graphene-like, polymeric type material, with high thermal and chemical stability and response to visible light due to its large optical band gap (2.7 eV). However, the key issue that limits its performance is its fast charge recombination rate, which can be addressed by loading its surface with a co-catalyst, such as TiO2. Therefore, the hybrid TiO2/g-C3N4 material combines the merits of the two semiconductors, while overcoming their disadvantages.
In this work, we propose the synthesis of hollow TiO2 nanospheres and their loading with g-C3N4, by the in-situ thermal decomposition of urea, to obtain hybrid TiO2/g-C3N4 materials with different g-C3N4 loadings. The photocatalytic activity of the synthesized materials was evaluated in the decolorization of the methylene blue dye under visible light irradiation. The hybrid photocatalysts displayed superior performance compared to the individual semiconductors. This enhanced photoactivity was ascribed to the higher absorption in the visible light range and the reduced recombination of the photoinduced hole-electron pairs in the TiO2/g-C3N4 hybrids.

Electronic structure calculations, typically at the level of Density-Functional Theory (DFT), play a key role in the design of new materials, including complex ones such as nanocomposites, heterostructures and nanoparticles. Such complicated structures often demand for multi-scale simulation schemes where DFT is coupled to a classical atomistic or even continuous model in order to link energies and wavefunctions of electrons to macroscopic properties of materials.
We present results from multi-scale simulations for the equilibrium shape and properties of metal nanoparticles. Shape of nanoparticles is calculated by combining the Wulff theorem and surface energies obtained from DFT calculations; such atomistic models allo for detailed calculations of the number of active sites for catalysis. We present applications of this idea to gold silver and platinum nanoparticles as well as encapsulated metal nanoparticles and self-assembled monolayers (SAMS) on complex surfaces.  Changes in nanoparticle shape induced by adsorption on its surfaces has an important effect in its electronic structure. Although Wulff theorem predicts only convex shapes for nanoparticles, recent advances allow for the simulation of concave nanoparticles polyhedra, too.

The flammability of conventional organic liquid electrolytes hinders the integration of large-scale lithium-ion batteries in today’s emerging sustainable landscape as zero-emission transportation (e.g. fully electric cars), as backup power in aircrafts and smart grid applications. Despite the considerable research effort in solid-state electrolytes (SPEs) that hold the promise to eliminate the safety issues associated with liquid electrolytes, their poor performance at room temperature has been the main drawback for their realization in operating batteries. We have developed a facile new approach for the synthesis of all-polymer nanostructured solid electrolytes that exhibit an unprecedented combination of high modulus and ionic-conductivity at room temperature. Novel nanostructured polymer particles were synthesized and utilized as additives to liquid electrolytes. These materials because of their molecular design constitute the first example of nanostructured polymeric materials of precise size and dimensions designed from the bottom-up. The mechanical properties of the resulting SPEs are dramatically improved compared to the pure liquid electrolyte while the ionic conductivity was maintained close to that of the pure liquid electrolyte. Key to their performance is their morphology that stems from the ability of the nanostructured nanoparticles to self-assembly in highly interconnected structures within the liquid electrolytes host. Our strategy offers tremendous potential for the design of all-polymer nanostructured materials with optimized mechanical properties and ionic conductivity over a wide temperature window for advanced lithium battery technology. The technology we envisage could bring a breakthrough also in many diverse applications as the design of mechanical robust electrolytes with superior ion conductivity at room temperature has been the subject of research for other energy-related applications, like anion exchange membranes for fuel cells, or efficient active layers in dye-sensitized solar cells.