The energy retrofitting of heritage buildings is constrained by strict requirements on material compatibility, reversibility, and minimal intervention, limiting the use of conventional insulation systems. In this context, limebased rendering mortars incorporating phase change materials (PCMs) offer a promising solution for enhancing thermal performance while respecting conservation principles. This study investigates the suitability of PCMenhanced ternary lime-pozzolan-cement mortars through a combined laboratory and field-scale experimental approach, with particular emphasis on real-scale validation under outdoor conditions. Mortars incorporating microencapsulated PCMs were characterized in terms of microstructure, hygric and mechanical properties, thermal conductivity, and latent heat storage, alongside durability assessment under freeze-thaw and salt crystallization cycles. Thermal performance was evaluated using hot-box testing and monitored full-scale mock-ups exposed to real climatic conditions. The results show that PCM incorporation significantly reduces thermal conductivity (from ca. 0.63 to 0.30 W m- 1 & sdot;K- 1) while providing latent heat storage up to 2.7 J g- 1. Durability performance was maintained or improved compared to reference mortars. Both laboratory and field-scale results demonstrate the ability of PCMenhanced mortars to attenuate temperature fluctuations, leading to smoother internal temperature profiles and reduced thermal peaks under real environmental conditions. Overall, the findings confirm that PCM-enhanced ternary lime-based mortars can provide passive thermal buffering while maintaining compatibility with heritage substrates, supporting their application in conservationoriented energy retrofitting strategies.

We report the first incorporation of diverse lacunary polyoxometalate (POM) nanocluster materials as efficient interface modifiers in perovskite solar cells (PSCs). Devices utilizing POM-modified SnO2 electron transport layers demonstrated marked improvements in open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF), achieving power conversion efficiencies exceeding 21.6%. Transient photovoltage and photocurrent analyses revealed that the B1-type based device exhibited the longest carrier lifetime and most rapid charge extraction rate, indicating optimized charge transport and suppressed recombination losses. Stability assessments under ambient conditions confirmed that B1-type POM-modified devices retained higher efficiency over time with reduced hysteresis compared to control devices. Work function measurements indicated POM-induced energy level alignment shifts, facilitating efficient charge transport. Morphological and structural analyses via scanning electron microscopy and X-ray diffraction confirmed that POMs using tungsten (W) addenda (i.e., B1–W and B2–W) promoted superior perovskite crystallization, yielding larger grain sizes and enhanced crystallinity. These findings establish the potential for lacunary POMs to serve as effective interface modifiers for advancing the efficiency and durability of perovskite-based optoelectronic devices.

The deterioration of porous building materials in archeological monuments is often intensified by slow and cumulative compound climate events, including salt crystallization cycles. This research examines the spatial patterns of these damaging events across Greece using high-resolution climate simulations derived from ERA-Interim and ERA5 Reanalysis datasets, as well as EURO-CORDEX models. By analyzing both past conditions (1980–2004) and projected future scenarios (2025–2049) under RCP4.5 and RCP8.5, the study identifies regions at heightened risk and explores how climate change influences the occurrence and possibly alters the aggressiveness of such events. By mapping the total frequency of these events and their anticipated changes under future climate conditions, this study contributes to developing a climatology of compound events that affect porous building materials of cultural heritage importance.

The decay of porous materials in archaeological and built heritage is often accelerated by compound climate events, such as frost, salt crystallization, and prolonged rainfall. These processes threaten the definition of architectural surfaces, structural integrity and thus the heritage values of monuments built with porous inorganic materials. This study investigates the spatial and temporal distribution of these decay-inducing events across Greece, utilizing observational data and the Ensemble of five high-resolution climate simulations from EURO-CORDEX and EC-EARTH models. Focusing on the historical period (1980-2004) and future projections (2025-2049) under RCP4.5 and RCP8.5 scenarios and using a set of heritage climatology indicators, this work reveals regional vulnerabilities and highlights the impacts of climate change on the frequency of such events. The study revealed high vulnerability on most mountainous regions and most of Northern and Western Greece for the sum of annual events, exhibiting future reduction. Salt transitions yield no significant changes, while events of prolonged rainfall and frost show a declining trend. By mapping the pace of decay-inducing events across the Greek territory, this research makes a solid first step to assessing risk-prone areas, hence offering a layer new knowledge for better-informed, and more localized heritage preservation strategies.

AbstractHalide organic–inorganic perovskites (HOIPs) are a promising class of materials for neuromorphic computing and processing systems demonstrating a variety of resistive switching (RS) mechanisms. HOIPs have been used as active layers in two‐ and three‐terminal synaptic devices reporting high performance in metrics of speed and energy consumption. Nevertheless, halide perovskites suffer from poor ambient stability and reproducibility. In this work, a highly robust double memristor based on two active layers forming a stacking heterojunction is demonstrated. In particular, the functional layer consists of a molybdenum oxide‐molybdenum sulfide compound (MoO3‐MoS2) and a quadruple cation perovskite (RbCsMAFA) deposited on top showing favorable band alignment for the specific application. The double memristor based on the MoO3‐MoS2/RbCsMAFA heterojunction exhibits impressive and stable resistive switching behavior with endurance of 100 cycles, high retention of 2 × 104 s, high environmental stability maintaining its memristive behavior for 1 month, and excellent artificial synaptic functions. The robust device also exhibits good thermal stability maintaining the memristive characteristics at 85 °C, as well as good photonic memristive behavior with an improved ON/OFF ratio under constant illumination. Here it is proven that the proposed double memristor is a promising candidate for artificial synapses and neuromorphic computing systems.

The aim of the present article is to investigate the sustainability of the production of different carbonnanostructures that can be used to reinforce lime-based mortars for structural health monitoring of the restoration areas in Monuments of Cultural Heritage. Aspects like manufacturing cost, environmental impact, mechanical properties, and piezo-resistive response were investigated to select a sustainable carbon nanostructure to reinforce lime-based mortars under different, multi-decision criteria. A quantitative cost assessment methodology for five (5) different carbon nanostructures (graphene-G and multi-wall carbon nanotubes-MWCNTs) in laboratory-scale was adopted. The results were interpreted against the respective enhancement on the mechanical properties resulted on the end-products, e.g., the nano-reinforced lime-based pastes. The mechanical tests results showed that the modified MWCNTs enhanced flexural strength by 109 % due to increased anchoring of the reinforcing nanostructures in the paste, while compressive strength was not essentially affected. On the contrary, the modified graphene nanostructures enhanced only the compressive strength of the paste by 29 % due to their platelet geometry and their respective load transfer capability. The high manufacturing cost of reduced graphene (rGO) 2.62 /g is related to the high cost of raw materials utilized, while graphene oxide (GO) has a manufacturing cost of 1.37 /g, mainly due to the balanced contribution of material and labour cost, respectively. These nanostructures were calculated to have the lowest environmental impact (0.10 kg CO2eq/g), while the carboxylation process increased essentially the equivalent carbon footprint by approximately (8 x) eight times (0.83 kg CO2eq/g). In most cases, GO excel among the different carbon nanostructures studied, due to its low values in several criteria, like mechanical properties per manufacturing cost or mechanical properties per carbon footprint, as well as showed the best piezo-resistive response to cyclic compressive mechanical loads. To this end, it proved to be the most sustainable carbon nanostructure to be exploited in relevant applications.

Although organic light-emitting diodes (OLEDs) are considered a mature technology, further enhancements in their efficiency are of paramount importance for advancing their incorporation in high-quality displays and flexible, wearable, electronic devices. In this regard, we propose an innovative approach, focusing on strategic modifications to the hole transport layer (HTL) through the integration of core-shell nanoparticles. Silver nanoparticles (Ag-NPs) encapsulated in a tungsten polyoxometalate compound (POM) are embedded within the prototype poly(3,4-ethylenedioxythiophene)-poly(styrenesulphonate) (PEDOT:PSS) to form the modified HTL. Our work reveals the pivotal plasmonic role of Ag-NPs in enhancing OLED device performance based on commercially available conjugated polymers. Comprehensive analyses, including UV-Vis absorption spectroscopy, atomic force microscopy, photoluminescence spectroscopy, and electrical measurements, confirm the influence of the POM encapsulated Ag-NPs on improving the device efficiency. This is attributed to the synergistic influence of enhanced hole injection and conductivity and beneficial optical effects (i.e. the Localized Surface Plasmon Resonance (LSPR) and, likely, light scattering of the POM-Ag NPs in the core-shell configuration, depending on their diameter), contributing to enhanced carrier balance and exciton recombination rate. Comparison with POM gold NPs (POM-Au NPs) highlights the distinct advantages of POM-Ag NPs. Our work reveals the potential of this innovative approach to contribute to the evolution of high-performance OLEDs, ensuring a visually compelling and efficient future.

The aim of this work is the development of cementitious macro-capsules for self-healing cement and concrete materials. Emphasis is placed on shell properties, including size, thickness, strength, and volume to active component ratio. This enhancement is aimed at protecting the healing agent and ensuring adequate reactivity upon crack formation, surpassing survivability considerations. To this direction, core/shell particles have been produced following the pan-coating method, while different types and concentrations of setting acceleration solutions for the shell stabilization were studied. The formation of core-shell capsules encompasses the formation a spherical core through agglomeration, followed by simultaneous spraying of cement powder and a setting acceleration solution for the shell formation, under continuous rotation. The microstructural characteristics of the shell were studied through scanning electron microscopy (SEM), while the reactivity of the protected core (reactive agent) inside the hardened mortar mixtures was evaluated using thermogravimetric analysis (TGA). Moreover, the crushing load of the capsules under compression and their survivability during mixing process were examined and interpreted in relation to their diameter, circularity, and shell thickness.The results revealed the ability of the encapsulation methodology proposed to tailor the shell properties and modify the capsule properties so as satisfy the requirements of different applications. The use of setting accelerators during shell formation proved essential for enhancing the density and the strength of the shell layer. As a consequence, this leads to macro-scale capsules with elevated survivability rate and core reactivity.

This paper combines simulation and experimental studies on the healing efficiency of spherical macrocapsules incorporated in cement mortars. A Monte Carlo simulation was applied to investigate the potential of capsules to heal cracks of different widths, depending on their size and concentration. Spherical cement-based macrocapsules were integrated in cement specimens aiming to examine experimentally their distribution in cement mixtures, their impact on mechanical properties and on the healing efficiency of cement. Interpretation of simulation and experimental results exhibited great coincidence, revealing the beneficial effect of the capsules developed. By using a 10% vol. of capsules with diameter of 3 +/- 0.3 mm, an adequate amount of healing agent for healing cracks up to c. 500 mu m is provided, resulting in a significant decrease of the water permeability after 28 d of healing, while simultaneously contribute in load regain of the cementitious matrix under flexural stress.

Weather conditions affect the microclimate of architectural monuments. The alteration of microclimate conditions may create risks for monuments, accelerating their weathering process. For Greece, hosting numerous monuments, the identification of the risks that climate change possess is essential for planning mitigation actions. The main soluble salts that affect archaeological materials are halite and the system of thenardite/mirabilite. The thermodynamics of the salts’ equilibrium are affected by atmospheric conditions. We study the climatology of these conditions, adopting modeled data produced by high-resolution simulations. Possible climate change impacts are investigated, aiming at mapping monuments’ vulnerability in Greece.

Encapsulated healing agents is a promising solution for extending the service life of critical infrastructure, providing long-term healing efficiency. This research focuses on the shell properties of cement-based spherical macro-capsules, aiming to achieve increased survivability during mixing of mortar mixtures and efficient triggering upon crack propagation. In this framework, the pan coating technique was examined for the production of capsules with a cementitious shell, developed for the protection of powder healing agents. The main properties that were studied included the crushing load as a function of capsules size and the shell hydration facilitated by different setting accelerators, and their consequent effect on the survivability and the triggering efficiency of the capsules. The results show that the use of setting accelerators allows the rapid densification of the shell microstructure and improves the crushing load of capsules, resulting in high survivability during mixing process. The enhanced compatibility of capsules with the matrix allowed the efficient triggering of capsules during crack propagation, initiating the autonomous healing process.

This work presents the methodological approach followed for the study of the interaction of natural stone monuments with the local microclimate (exposure to RH, temperature alterations, wind, marine aerosol). This was implemented with the documentation of the associated weathering phenomena and the study of historic climate data of the area. The paper is focused on the main weathering mechanisms of the marly limestone at the Hellenistic theater of Zea in Piraeus, Greece. Based on the weathering phenomena identified, the development of the appropriate mitigation strategy was based on the physical, chemical and mechanical characterization of the natural stones, along with the evaluation of different conservation treatments, considering the characteristics of the coastal environment. Considering the mineralogy of marly limestones, silane-based materials were selected for providing both consolidation and water repellency effects. The evaluation of the conservation treatments was based on the modification of microstructural and water-related properties of natural stone samples, along with their consequent effect on their durability against accelerated aging tests. The results indicated that the design of migration actions proved to be multivariable parameter, depending on the intrinsic stone properties, the environmental parameters and the conservation efficacy of the treatments.

Two gallium porphyrins, a tetraphenyl GaCl porphyrin, termed as (TPP)GaCl, and an octaethylporphyrin GaCl porphyrin, termed as (OEP)GaCl, were synthesized to use as an electron cascade in ternary organic bulk heterojunction films. A perfect matching of both gallium porphyrins’ energy levels with that of poly(3-hexylthiophene-2,5-diyl) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) polymer donor and the 6,6-phenyl C71 butyric acid methyl ester (PCBM) fullerene acceptor, forming an efficient cascade system that could facilitate electron transfer between donor and acceptor, was demonstrated. Therefore, ternary organic solar cells (OSCs) using the two porphyrins in various concentrations were fabricated where a performance enhancement was obtained. In particular, (TPP)GaCl-based ternary OSCs of low concentration (1:0.05 vv%) exhibited a ~17% increase in the power conversion efficiency (PCE) compared with the binary device due to improved exciton dissociation, electron transport and reduced recombination. On the other hand, ternary OSCs with a high concentration of (TPP)GaCl (1:0.1 vv%) and (OEP)GaCl (1:0.05 and 1:0.1 vv%) showed the poorest efficiencies due to very rough nanomorphology and suppressed crystallinity of ternary films when the GaCl porphyrin was introduced to the blend, as revealed from X-ray diffraction (XRD) and atomic force microscopy (AFM). The best performing devices also exhibited improved photostability when exposed to sunlight illumination for a period of 8 h than the binary OSCs, attributed to the suppressed photodegradation of the ternary (TPP)GaCl 1:0.05-based photoactive film.

Lime based restoration mortars reinforced with multi-walled carbon nanotubes (MWCNTs) exhibit advanced mechanical strength, piezo-resistive properties and probably their main advantage is that they can be used as self-sensors for on-site health monitoring purposes of the restoration areas of traditional / historic structures. The present study assesses their economic viability via a comparison of innovative vs. conventional restoration treatments, based on Activity Based Cost (ABC) modeling and evaluation. ABC was applied to a hypothetical restoration scenario, which includes three restoration intervention ratio sub-cases (expected, optimistic and pessimistic), in relation to the structural part that will require re-treatment in more than 20 years life cycle time frame. The advantages of the application of the innovative material are portrayed in all investigated three-service life intervention sub-cases. In particular, the innovative approach method presents economic risk–benefit advantages from 1 % up to 14.6 % (depending on the sub-case) in comparison to the conventional approach.

Earth-abundant transition metal oxides deposited at room temperature with low-cost methods suitable for large area manufacturing can offer advances in many fields of energy related devices. Here we report the room-temperature deposition of a fluorine-doped tantalum pentoxide using a home-made, low-cost hot-wire deposition system. This novel tantalum oxyfluoride material is super hydrophobic, ultra-transparent within the visible spectrum, and possesses adequate conductivity and suitable valence band and conduction band extrema for acting as efficient hole extraction and electron blocking layer in organic solar cells with the forward architecture. By inserting this material in the form of nanoparticles deposited on top of the commonly used as hole transport layer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, higher efficiencies compared to the reference cells without the nanoparticles were demonstrated in solar cells based on blends of polymer donors with either a fullerene (where maximum achieved efficiency was improved from 6.07% to 7.90%) or a non-fullerene acceptor (reaching values of 13.48% compared to 11.32% of the reference cell). Moreover, significant improvement in device stability was achievd in unencapsulated devices continuously exposed in a humid environment for 500 h. This work demonstrates the unambiguous potential of well-designed metal oxide materials as charge transport and blocking interlayers and protective buffers in organic solar cells and beyond.

Lime-based binders have been extensively used for restoration interventions and have successfully addressed different performance and compatibility requirements. Lime (aerial or hydraulic) is commonly used in combination with pozzolanic admixtures or cement, to comply with both, chemical/mineralogical and mechanical compatibility criteria. The goal of the present investigation is the production of binder matrices with tailored mechanical properties according to the above criteria. The first binder was a binary paste consisting of natural hydraulic lime and metakaolin and the second was a ternary matrix consisting of hydrated lime, cement and metakaolin. The flexural and the compressive strength of the binary paste were 1.6 MPa and 6.1 MPa, respectively, while the use of cement in the ternary mixture increased the flexural and the compressive strength at the values of 2.5 and 8.5 MPa, respectively. Mechanical properties of several lime/metakaolin binders and lime/cement binders were collected from the literature to establish approximations correlating the binder composition to the mechanical response. The proposed approximations can be used as guidelines for facilitating the design of modern conservation binders based on mechanical compatibility and binder composition parameters, according to the requirements of the individual restoration project.

Encapsulated healing agents comprise an emerging technology that aim to extend the service life of critical infrastructure and reduce the environmental impact of the construction industry. This paper focuses on the development and characterization of cement-based macro-capsules, made by the pan-coating technique, consisted of a reactive OPC core and a durable shell produced by the reaction of OPC with sodium silicate (SS). Two types of capsules in the range of 2-5 mm were produced in order to evaluate the effect of SS concentration on the microstructure and mechanical performance of the shell. Both types of capsules were integrated in cement mortar mixtures in different fractions (5-20%) by replacing equal sand volume. The fresh properties of the mixtures, the mechanical performance of the hardened specimens and the self-healing efficiency by means of water sorptivity were assessed and compared to the reference mixture of plain cement mortar. The results show that the addition of sodium silicate improves the crushing load of capsules under compression loading, yielding up to 75% survivability during the mixing process. The integration of capsules did not affect the rheology of the fresh mortar mixtures, while it became clear that the shell properties play a significant role on the mechanical performance of the composite mixtures. Healing assessment revealed that the addition of 20% capsules can reduce the sorptivity coefficient up to 80% after a 28 days healing period.

In the present study, graphene oxide (GO), reduced graphene oxide (rGO) and carboxylated graphene (GCOOH) have been incorporated in lime-pozzolan-cement pastes, aiming to develop self-sensing binders that would be used for restoration applications. Τhe mechanical and electrical properties of the newly-developed nanocomposite pastes were examined and compared against the respective properties of a reference paste. The incorporation of the different types of graphene nanostructures significantly increased the compressive strength of all the investigated pastes, while the highest increase was noted for the rGO reinforced paste (+33%). The addition of GO and rGO increased by 14 % and 7 %, respectively the flexural strength of the pastes, while no improvement was noticed for the GCOOH addition. On the contrary, the GCOOH addition enabled the paste to exhibit excellent piezoresistive properties. In fact, a 70 % fractional change in electrical resistance was noticed under cyclic loading – unloading at a level of 50 % of the compressive strength. The rest of the mixtures investigated, showed lower fractional electrical resistance change under the same loading protocol.

Self-healing cement composites are considered to be an effective solution towards the enhancement of sustainability and service-life of cement and concrete structures, as well as the reduction of repair and maintenance cost. Among the several self-healing technologies, encapsulated healing agents present benefits that include healing of larger cracks and timeless healing potential upon damage. This paper presents a critical overview of the progress made in the development of encapsulated healing agents, along with the main achievements related to their integration in the cement mixtures. Encapsulated healing agents were classified according to their size in two main categories: (i) spherical microcapsules up to 1 mm, and (ii) macrocapsules that include larger spherical capsules (>1 mm) and/or tubular capsules up to 100 millimeters long. The review emphasizes on the performance characteristics of the shell material and the capsule system that are necessary in order to protect the different types of healing agents in the long-term, to provide even distribution and survivability and finally, to ensure efficient triggering and release of the healing agent during crack propagation. The relevant literature is analyzed and discussed according to the above thematic priorities, aiming to locate research gaps and best practices and thus, to enable and facilitate the development of effective encapsulated healing agents that could be scaled-up. To this end, particular emphasis is given on the effect of capsules integration on the properties of both fresh mixtures and hardened cement specimens.