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The new courses "Ethics and academic integrity" introduced in the curriculum of master's programs complete the educational process with its axiological dimension. In these courses, students and especially student-engineers are confronted with concepts such as morals, values, good conduct. Given the fact that higher education graduates will be part of a society that is developing in a sustainable way, there is an increasing need to identify bridges that link the purely technical training with the ethical aspects of technological development. respecting social and environmental values. This paper presents an argument for teaching the concept of environmental ethics in the new courses "Ethics and academic integrity" to students in the field of engineering, to create an opportunity for them to approach their knowledge from multiple ethical, social and environmental perspectives.

This study investigates the photocatalytic activity and long-term stability of a two layered Vis-active composite thin films ZnO/ZnO-GO: (a) under UV+VIS irradiation (55W/m2) and (b) under 100% UV (3W/ m2), for up to 48 h, using methylene blue (c = 10 ppm) as standard pollutant. The photocatalysts stability is discussed considering the variation in transmittance and roughness (RMS) before/after photocatalysis correlated with the processes affecting the photocatalyst surfaces. The photo-degradation efficiencies reach 98% after 48h under UV+VIS irradiation for the thin film sprayed on a thinner ZnO layer; that was also the mostly stable film, with low transmittance (

Environmental Education is essential to promote awareness and facilitate the development of environmental citizens. To contribute to the enhancement of environmental awareness, Iceland, Serbia, Bosnia and Herzegovina, and Romania have collaborated in joint educational projects which aim at building capacities on sustainable development, delivering environmental teaching lectures, and developing open educational resources. This article presents past and ongoing collaborations between the mentioned countries, assesses the status of environmental education, and highlights the benefits of international collaboration. For this purpose, information on environmental courses in representative universities from each country was collected, SWOT analyses were performed in each country, and a survey among potential students was carried out. The presented analysis reveals that international collaboration raises environmental awareness and increases the likelihood of becoming environmental citizens.

The study investigates the long term stability and photocatalytic activity (up to 72 h) of the Cu2ZnSnS4/TiO2 thin film heterostructures, under simulated solar radiation, at low irradiance values (34 W/m2), using phenol and imidacloprid (c = 10 ppm) as testing pollutants. High removal efficiencies correspond to both phenol (73%) and imidacloprid (57%) after 72 h of irradiation, while mineralization occurs slower, with efficiencies up to 42% for phenol, and less than 10% for imidacloprid, in agreement with the pollutant chemical structure. The stability of the photocatalysts in the aqueous pollutant solutions is investigated using VIS transmittance spectra, scanning electron microscopy, atomic force microscopy while photocatalyst leaching was evaluated based on surface composition analysis and atomic absorption spectroscopy. The processes affecting the photocatalyst surface and composition were discussed and the results were correlated with TiO2 layer morphology and porosity and pollutants' structure; promising results are outlined as low variation in the layers transmittance (after 72 h of testing: ΔT600 The results recommend the use of Cu2ZnSnS4/TiO2 thin film photocatalyst for large-scale applications, involving organic pollutants removal from wastewaters, even at very low concentrations.

The study investigates the self-cleaning and anti-reflectance properties of thin films based on tungsten oxide (WO3) and reduced graphene oxide (rGO) deposited by spraying stable dispersions of sol-gel powders. Two routes were employed: (Route 1) highly crystalline WO3 powder (annealed at 550 °C for 3 h) was mixed with commercial rGO powder in the dispersion and (Route 2) rGO was directly added to the WO3 precursor system to obtain a WO3-rGO sol-gel composite powder (further on annealed at 100 °C for 3 h). Both powders contain WO3 and rGO as confirmed by FTIR and XRD analyses. By milling the pristine WO3 (Route 1) with rGO, more stable dispersions could be obtained using sodium dodecylsulfate (SDS). The hydrophobic surfactant tail bonds to the rGO and the electrostatic repulsion between the anionic heads prevent the flakes agglomeration. In Route 2, the dispersions are not well stabilized by SDS as the anionic head and the WO3 “grafted” on the rGO are both negatively charged, thus repulsions can be expected. This leads to agglomerates formed on the thin films surface that affect the thin films’ UV-VIS transmittance and reflectance but increase their efficiency in methylene blue removal through adsorption. Overall, however, the films obtained following Route 1 proved more uniform, crystalline and superhydrophilic, while maintaining comparable stability in the photocatalysis conditions, and comparable efficiency in methylene blue removal: 25% after 8 h of irradiation with 10% UV + 90% VIS light, having the global irradiance of 34 W/m2.

The study presents comparative results of the photocatalytic removal efficiency of methylene blue (MB), phenol and imidacloprid, using spray deposited thin film heterojunctions based on (SnO2)-Cu2ZnSnS4-TiO2. The addition of the SnO2 layer increased the samples roughness, but had limited effect on their overall photocatalytic efficiency. The thicker TiO2 layer did not limit the light penetration required to activate the p-type layer as comparable or slightly higher photocatalytic efficiency values were obtained using thicker TiO2 thin films compared to the samples containing thinner ones. Adsorption appears as the most important step in the degradation mechanism, for all the investigated pollutants. Promising photocatalytic efficiencies of 20–30% for methylene blue, 15–20% for phenol and 10–12% for imidacloprid under simulated solar radiation with low irradiance (34 W/m2) and low pollutant initial concentrations (10 ppm) were obtained using the multilayered structures. The addition of the Cu2ZnSnS4 extended to VIS the activation domain of the samples, leading to improved pollutant removal compared to the reference TiO2 thin films.

While the photocatalytic degradation of dyes and other pollutants from wastewater by titanium dioxide (TiO2) is recognized as a highly efficient process, the cost of using UV radiation still prevents it from large-scale application. One method of moving from the UV activation energy towards the visible (Vis) spectral range could be the use of n-p heterostructures, with an overall band gap lower than that of TiO2. In this paper, thin film heterostructures based on TiO2 as n-type semiconductor and copper zinc tin sulfide (Cu2ZnSnS4, CZTS) as p-type semiconductor were tested in the dye removal of methylene blue, under Vis and solar simulated radiation. The thickness of the outer, TiO2 layer was varied by changing the precursor concentration (TiCl4, 0.05 M and 0.1 M). It was found that a higher titania film thickness promotes enhanced crystallinity, which is useful in a photocatalyst. From a morphological point of view, both samples showed a continuous coverage of the CZTS thin film, with multiple TiO2 aggregates on the heterostructure surface. The sample containing TiO2 prepared from the 0.05 M solution, exhibits Cu-poor, Zn-rich composition which promotes a better charge carrier transport in the material. This is confirmed by the higher dye removal efficiency (27.6%) of this sample, under Vis irradiation, for 8 h. The addition of 3% UV to the Vis radiation (simulated solar radiation) leads to a further increase of nearly 7.7% in the dye removal efficiency.

Due to the lack of European Massive Open Online Courses (MOOCs) in the field of the Toxicology and the major differences in the styles of teaching and learning of this important subject in amongst various European life science-oriented institutions, the European Erasmus+ project “Learning Toxicology through Open Educational Resources (TOX-OER)” was developed and implemented. Considering the complexity and heterogeneity of the toxicology field, the TOX-OER project main objective was to develop and share toxicology-related knowledge and skills among students/ earners from seven countries, which promote the internationalization of Higher Education Institutions in Europe but also in countries from other continents. The project was coordinated by Universidad de Salamanca (Spain), and the partners were: Space Research and Technology Institute (Bulgaria), Univerzita Karlova V Praze (Czech Republic), South-Eastern Finland University of Applied Sciences (Finland), Università di Bologna (Italy), Universidade do Porto (Portugal) and Universitatea Transilvania din Brasov (Romania). One of the goals/ objectives of the project is the dissemination, popularizing the information and reaching potentially interested people who can benefit from the offered courses. The aim of this paper is to present and analyze part of the TOX-OER’s outcomes developed by the project’s partnership, especially the modules/ topics related to the drugs, gaseous and persistent organic pollutants, as the principal groups of xenobiotics.

The quest for up-scaled photocatalytic processes asks for the development of Vis- or solar-active catalysts used in technologies without additional expensive steps. This chapter reports on novel heterostructured thin films mimicking a solar cell with the structure glass/CZTS/TiO2 deposited by spray pyrolysis (SPD), to be used for advanced wastewater treatment, at low concentration of organic pollutants. The deposition of the photocatalytic plates is comparatively analyzed with that of the small platelets (2.25 cm2), and the results outline that there is no need for reoptimizing the SPD deposition to obtain 100 cm2 plates. Photocatalytic experiments were developed using a continuous flow photocatalytic reactor and three different solutions having as pollutant methylene blue, imidacloprid, and phenol at an initial concentration of 10 ppm. The experimental results outline that the removal efficiency significantly depends on the pollutant molecular structure, as the size and the flexibility of this molecule had a direct influence on its adsorption efficiency—the first (key-step) in the photocatalytic mechanism. The influence of the radiation type (UV, UV + Vis, or Vis) and its irradiance value were investigated, and it was outlined that a higher irradiance leads to higher removal efficiency for the pollutants that are not strongly adsorbed on the photocatalyst surface. The removal efficiency observed in the continuous flow regime was comparatively analyzed with that in static regime (no flow) at a similar ratio of the pollutant solution volume and the photocatalytic surface area. The results showed that, in the continuous flow regime, the efficiencies are significantly reduced as a possible result of the “wash out” effect that limits the pollutant adsorption and thus supports the deactivation of the photocatalytic species before involving them in oxidation processes. The results are promising and can be extended to self-cleaning photocatalytic surfaces, applied on the outer walls of the buildings.

Although Open Educational Resources (OERs) and Massive Open On-line Courses (MOOCs) are more and more developed and available in European educational systems, there is a lack of MOOCs in the field of toxicology and environmental sciences. Starting from this fact, the “Learning Toxicology through Open Educational Resources – TOX-OER” project was granted and run between 2015 and 2018. Seven European High Education Institutions shared knowledge and skills and created seven toxicology-related OERs. The challenges and the experience gained during development of these OERs, especially the video presentations, supporting texts, additional documentation, and evaluation tests, are presented in the present paper. Our outstanding experience gathered during TOX-OER project, contributed to the decision to extend our initiative to a subsequent project, “Environmental Education – OERs for Rural Citizens” (EnvEdu – OERs). The new project aims to develop new OERs targeting rural citizens’ life-long learning focusing on environmental quality. The lessons learned from the TOX-OER project are presented not only for an effective transfer to the new EnvEdu – OER project, and for an efficient rural community acceptance, but also for other audience facing similar challenges and experience in creating OERs.

The sudden shift from the lecture theatres and laboratories to a laptop or smart phone screen due to the restrictions caused by the pandemic 2020 crisis, changes the students’ way of working in the academic environment. The present paper investigated the engineering students’ perception of the changes occurred during this period. The investigation was based on a questionnaire, aiming to point out evidences on premises which can be used in designing new learning environment in the future. Promising premises regarding students’ willingness for learning in on-line environment exist, and this can push the on-line learning to become a consistent part of the curriculum. There will be necessary a special focus on courses design and also on remedial consultancy for students for their personal development.

Individual TiO 2 and WO 3 , as well as stacked TiO 2 /WO 3 thin films with self-cleaning properties were sprayed onto a solar glass substrate. The composite thin film exhibits superhydrophilicity (water contact angle 10.2°) due to the use of WO 3 as outer layer. In spite of its high carbon content, which delays its photocatalytic activation, it exhibited higher efficiency in the methylene blue removal than the individual TiO 2 or WO 3 layers after 6 h of irradiation (solar simulated radiation at low irradiance, G=34 W/m2). The high VIS-transmittance (>80%) recommends the films for self-cleaning coatings on glazing and on other transparent substrates.

Heterogeneous photocatalysis represents an efficient method for organic pollutants degradation from wastewaters or from the atmosphere, at low concentrations (at ppm level or lower), but exceeding the discharge limits. Despite the good results reported at the laboratory and at pilot scale, its extended application is limited by the costs of UV radiation required to activate the semiconductor mono-material photocatalyst. This chapter presents an overview of the results obtained in developing composite thin films, resembling the third generation of PV cells that can be used as efficient, VIS-active photocatalytic materials for different environmental applications, including wastewaters treatment, air depollution or self-cleaning surfaces. The challenges in developing composite photocatalysts are discussed, considering the prerequisites on the structural (suitable bandgap alignment, allowing VIS activation and fast charge separation) and surface properties (specific surface and surface charge), the stability (mechanical and chemical stability in the working environment), the photocatalyst recovery after the process (thin films vs powders). Sustainable solutions are presented in terms of materials composition and deposition technologies. The results obtained in the photocatalytic degradation of methylene blue (reference pollutant), imidacloprid or acetaldehyde on composite thin film photocatalysts containing TiO2 or ZnO and sulfides (CIS, CZTS, CuxS) and/or oxides (SnO2, CuO) or graphene derivatives, under various types of irradiation (VIS, UV + VIS, simulated solar radiation), in static and/or in continuous flow regime are discussed. The factors influencing the process efficiency are presented and outline the need for optimizing the working pH to insure both, the efficient pollutant adsorption at low concentrations and the photocatalyst stability. The results show good removal/mineralization of the organic pollutants and allow recommendations on the use of composite thin films in the photocatalytic applications.

The increasing need to develop a sustainable built environment asks for the integration of solar energy conversion technologies in the new or existing building elements. The integration must meet basic requirements on functionality, cost, environmental protection and last but not least social acceptance. This involves efforts to find novel, competitive solutions, to slow down (or stop) climate change and also to answer the increasing needs of the social system. The paper presents flat plate solar thermal collectors (FPSTC) with nontraditional shapes and colour, suitable for facades’ integration. The coloured absorber plates (red, green and yellow-orange) were integrated at demonstrator level, and the recorded nominal efficiencies reached promising values.

Responding to the increasing concern for preserving a clean environment, the development of self-cleaning coatings attracts growing interest, since they already demonstrated efficiency in pollutants removal. Considering the fundamental materials’ properties, the target is to develop materials demonstrating enhanced photoactivity under visible light irradiation, corroborated with controlled hydrophilic character. Two major conditions attract the research interest to provide promising, viable solutions: the material should be earth-abundant, non-toxic for humans and environment and the deposition technology should be affordable in terms of costs and energy, and does not lead to environmental risks. This paper presents the development of two types of materials: ZnO, obtained by spray pyrolysis and the ZnO–GO composite, deposited by combined sol–gel and spraying technique. The as-prepared samples proved promising self-cleaning properties. Both hydrophilicity and photodegradation efficiencies were enhanced by a surface pre-activation, consisting of samples’ exposure in dark and UV irradiation.

The paper presents a study on the structural, surface and photocatalytic properties of the ultrasound assisted sol-gel titanium dioxide particles, as part of stable photocatalytic ink formulations deposited on fabrics. The photocatalytic activity was validated using methylene blue as reference pollutant, under UV, VIS and combined UV+VIS radiation and allowed selecting the optimum TiO 2 samples for inks preparation. To minimize the particles agglomeration stabilizing agents were added and the stability was quantitatively evaluated considering the relative increase in the VIS transmittance for a pre-set period of 30 min. Further on, the ink(s) were deposited by cold spraying on cotton woven fabrics and a removal efficiency higher than 95% was observed in the degradation of the highly toxic mustard gas, after 30 min of UV irradiation.

This study presents the results obtained in tailoring thin films of alumina, deposited onto aluminium substrates by spray pyrolysis, at 250.C, using AlCl3 solutions (0.15M) in a water:ethanol (1:1) solvent mixture. As morphology controlling agents, acetylacetone and maleic acid based copolymers are added in the precursors solutions. The precursors systems are analyzed by FTIR spectroscopy and the surface morphology of alumina thin films is investigated by atomic force microscopy. The addition of hydrophilic copolymer in precursors solution favors the development of regular open structures, while fractured large open structures are obtained when hydrophobic copolymer is used. The addition of acetylacetone in spraying solution leads to irregular large open structures. Combined additive systems (acetylacetone and hydrophylic/hydrophobic copolymers) have a complex influence and can be a tool in tailoring the morphology of the alumina thin films, as suitable matrix for further infiltration of red (Fe2O3) and gray-green (CuxS) pigments and development of colored solar selective absorber coatings with promising optical performances. Thus, spectral selectivities (S) of 3.4 - 4.07 are obtained for red absorber coatings, while for gray-green absorber coatings spectral selectivities are slightly lower (S = 2.35 - 2.7).

Two heterojunctions based on CU2ZnSnS4 were obtained as thin films, on FTO glass, by spray pyrolysis deposition. The choice of the n-type layer (TiO2 or ZnO) has impacted the nucleation and growth of the CZTS layers deposited on top. Crystalline thin films were obtained with drastically different morphologies. Small spherical grains promoted a better match at the interface between TiO2 and CZTS, while the hexagonal plates of ZnO promoted discontinuations. Both junctions proved photosensitive and gave good rectifying behavior but efficiencies lower than 0.01% suggest charge recombination at the interface or in the CZTS layer.

Tandem structures involving CuInS2, TiO2 and SnO2 thin films were prepared by Robotic spray pyrolysis and were optimized in terms of composition and deposition temperatures. The compounds have structural compatibility (crystalline structures and crystallites sizes) and good homogeneity. The crystalline structures were investigated by X-ray diffraction and the morphology by atomic force microscopy and scanning electron microscopy. The wettability properties and the surface energy were calculated based on contact angle measurements using two liquids with different polarities (glycerol and ethylene glycol). The components in the tandem systems have suitably positioned the energy of the conduction and valance bands, limiting charge recombination, therefore, the sample containing all three semiconductors has the highest mineralization efficiency (95.3% removal of total organic carbon) under UV + Vis irradiation, mimicking solar radiation. Long term use of the photocatalytic films (up to 36 h) proved the need to design the process with interim washing steps for preserving the photocatalytic efficiency by avoiding surface clogging.

The paper presents a study on the parameters that influence the stability of photocatalytic ink formulations, to be further deposited on textile substrates. The main features are discussed based on the analysis (composition, structure, rheological parameters) of four commercial inks used in the digital printing on fabrics, outlining the stability as key factor. Further on, to obtain photocatalytic inks, TiO2 nanoparticles (Degussa P25, sol–gel) were dispersed in water, water–alcohol, and alcohol; the stability was evaluated using the transmittance spectra. The ink stability was improved and controlled by optimizing the type and amount of various stabilizers: dodecyltrimethylammonium bromide (DTAB), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and 2-[2-(2-methoxyethoxy)ethoxy] acetic acid (TODA). The surface modifications and interactions at the particle/continuous medium/stabilizer interfaces are comparatively discussed. The stabilization mechanisms are proposed considering the influence of the particle concentration, type/dimension and surface charge, and the continuous medium composition and pH. The photocatalytic activity of the sol–gel TiO2 was investigated, as dispersed powder and thin film, and comparatively discussed with Degussa (as reference). Based on these results, recommendations on the preparation, characterization and use of titania-based inks were done, outlining PEG and TODA as potential stabilizers.

A clean and efficient process for producing hydrogen using renewable energy sources is an important requirement for a future Hydrogen Economy. The production of hydrogen from water and solar energy is attracting widespread attention. In particular, research is focused on novel materials, or improving existing materials for the splitting of water using photocatalysis and photoelectrolysis. In this paper we highlight several recent developments in photocatalysts and we illustrate how engineering of properties on an atomic scale can be achieved by cation and anion doping, deviations from stoichiometry and in case of ternary or more complex materials, by deviations from molecularity. The defect chemistry of I-III-VI2 ternary semiconductors with the chalcopyrite structure is presented and used to construct a 3D-Brouwer diagram.

Recent research on heterogeneous photocatalysis is focused on producing new efficient TiO2 - based photocatalysts deposited on fabrics with increased adaptability and facile implementation as self-cleaning/self-decontamination, antimicrobial fabrics or in other photocatalytic applications as wastewaters treatment or air purification. This paper gives an overview on the R&D results obtained within the Renewable Energy Systems and Recycling Centre on the development of stable photocatalytic dispersions for fabrics coating, based on sol-gel TiO2. The challenges in the components development - the photocatalytic nanoparticles, the dispersion and the coated fabric are discussed considering TiO2 Degussa P25 based products as reference. Sustainable, optimized solutions in terms of stability and functionality (photocatalytic properties) are provided. Photocatalytic fabrics deposited at room temperature by spraying from polyethylene glycol or chitosan stabilized dispersions based on ultrasound assisted sol-gel TiO2 best meet the stability criteria and the photocatalytic properties (efficiency higher that 75% in methylene blue removal and over 95% in mustard gas decomposition) Recommendations in the design of self-cleaning/self-decontamination fabrics are provided.

Recent developments in solar-thermal energy conversion systems are focused on obtaining solar selective absorber materials with high selectivity and durability and asked for cost-effective and environmentally friendly synthesis techniques (e.g. sol-gel and chemical spray pyrolysis). In this context, the paper gives an overview on the state-of-the-art of the research reported till now on different types of black and colored absorber coatings for solar thermal collectors obtained world-wide. Some results obtained by the group active in the R&D Centre Renewable Energy Systems and Recycling are also reported and they are related to the development and optimization of black (NiSx) and red (Fe2O3) absorber coatings, as active components in solar thermal collectors. These results are considered promising for novel, market-competitive solar-thermal collectors, with increased architectural acceptance, for facades integration in Nearly Zero Energy Buildings.

a b s t r a c t Zinc oxide thin films were obtained by spray pyrolysis deposition using three surfactants with linear C12 tails as soft templating agents: anionic sodium dodecylsulfate (SDS), cationic dodecyltrimethy- lammonium bromide (DTAB) and nonionic dodecanol (DD). The influence of the surfactants' type and concentration (above and below critical micelle concentration in the precursor system) on the thin film formation was investigated and was correlated with their photocatalytic efficiency in methylor- ange removal, under visible and UV iradiation. The surfactants influence both the nucleation and growth stages, mainly through the Zn-surfactant interactions at the droplet border and/or on the micelles. In situ doping with Na+ (in SDS) improves the removal efficiency up to 19.88% under VIS irradiation, while the highest removal efficiencies in ZnO thin films obtained using DTAB and DD are 16.27% and 15.44%, respec- tively. Under UV irradiation the highest efficiencies are 45.28% (SDS), 51.59% (DTAB) and 49.43% (DD).

Sursele de energie sustenabila ce pot fi folosite pentru a genera electroni, cum ar fi de exemplu celulele solare si miniturbinele eoliene din mediul urban pot fi conectate la infrastructura energetica pentru a comtribui direct la reducerea emisiilor de CO2 provenite din arderea combustibililor fosili. Utilizarea descentralizata a acestor surse de energie sustenabila necesita sisteme de stocare. Pentru stocarea energiei electrice, sunt studiate materiale pentru acumulatoare, in special pentru baterii litiu-ion. Cu toate acestea, stocarea energiei electrice poate fi de asemenea realizata sub forma de hidrogen, ca purtator de energie. In consecinţa, au fost dezvoltate sisteme ce combina celulele solare si electrolizoarele comerciale pentru obţinerea hidrogenului si oxigenului din apa. O abordare mai promiţatoare este fotoelectroliza directa a apei folosind fotoanozi, materiale ce sub acţiunea parţii vizibile a radiaţiei solare pot genera oxigen, iar la contraelectrod hidrogen. Astazi, prin diminuarea dimensiunilor la scara nanometrica a materilalelor funcţionale, producerea fotoelectrochimica a hidrogenului atrage atenţia din ce in ce mai mult. Pentru obţinerea de nanotuburi, de suprafeţe cu structura de nano-fulgi si suprafeţe cu morfologie fractala, pentru fotoanozi o mare varietate de metode de sinteza au fost puse la punct. Optimizarea ulterioara a foto-anozilor este posibila prin combinarea lor cu celulele fotovoltaice pentru a forma un dispozitiv monolitic in tandem. Aceasta lucrare prezinta o trecere in revista a materialelor avansate utilizate pentru fotoanozi, impreuna cu modelele inovatoare pentru celulele fotoelectrochimice si fotoelectrozi. Sustainable energy sources that can be used to produce electrons, i.e., solar cells and small-scale wind turbines for the built environment, can be connected to the electricity infrastructure to directly contribute to the reduction of CO2 emissions from fossil fuel combustion. The decentralized utilization of these sustainable energy sources requires storage. For the storage of electrical energy materials are being developed for rechargeable batteries, in particular, for lithium-ion batteries. However, storage of electrical energy can also be achieved in the form of the energy carrier hydrogen. Hereto, the combination of solar cells and commercial electrolyzers to split water into oxygen and hydrogen has been developed. A more promising development is the direct photo-electrolysis of water using photo-anode

Six SnO2–TiO2 tandem semiconductor samples were prepared by spray pyrolysis deposition using different precursor compositions and deposition temperatures. By tailoring the indium doped tin oxide layer (morphology, crystallinity) the tandem properties can be modified according to the targeted application, insuring enhanced charge separation, higher photosensitivity and reduced recombination. On the SnO2 layer, the TiO2 growth was proved to be almost twice faster when starting from halide precursor, compared to organo-metallic ones, at a fixed deposition temperature (400 °C). The samples were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, contact angle, reflectance, current density–voltage (J–V) and photocurrent measurements. The photocatalytic efficiency of the tandem systems was tested on methylene blue reference solutions and was evaluated based on the variations in the organic carbon and total nitrogen content. The result were compared with bleaching measurements, showing that mineralization could be reached up to 90% and carbon removal is more efficient compared with nitrogen compounds.

Novel coloured solar-thermal absorber coatings are obtained as thin films of alumina infiltrated with pigment oxides (Fe2O3 and V2O5) and sulfides (CuS). The coatings are stepwise obtained in successive spray pyrolysis depositions, using inorganic precursors. The composite layers have good crystallinity degree and develop various morphologies, with very different matrix- pigment infiltration; the addition of gold nanoparticles differently influences the properties, depending on the interactions with the precursor species: it can strongly decrease the thermal emittance, when embedded in the layers structure (Fe2O3) or it can form large aggregates on the matrix (V2O5) without significant effect on the optical properties. Bright red spectral selective coatings, with spectral selectivity of 12 were obtained using Fe2O3 hematite pigments.

In recent years, chalcopyrite semiconductor thin films are being intensively investigated for low-cost terrestrial phovoltaic applications. One prerequisite for solid state solar cells is the strong interface to allow the intimate contact between semiconductors. The paper studied the possibilities of CuInS2 thin film surface control by using sodium dodecyl sulfate as additive in precursors’ solution in concentration below and above the critical micelle concentration of the surfactant in solution. The sample with the amount of surfactant lower than the critical micelle concentration in precursors’ solution has the highest surface energy value. The use of surfactant conducted to increased preference for formation of thin films with peaks, the higher peaks being obtained for the thin films obtained from solutions with surfactant concentration higher than critical micelle concentration.

The paper presents research concerning the synthesis and characterization of some new nanocomposite used as wood coating nanomaterials, consisting of a hybrid of organic (functionalized acrylic copolymers with iron lignosulfonate) and inorganic nanomaterials (ZnO nanoparticles obtained by sol-gel process). The presence of acrylic copolymers in water emulsion (based on monomers ethyl acrylate, butyl acrylate, acrylonitrile and the lignin derivative iron lignosulfonate) and ZnO nanoparticles enables the formation of a crosslinked nanometric network of inorganic and organic domains, emphasized by AFM analysis. The interphase characterization of the nanostructured materials synthesized was performed using FT-IR analysis. Considering the biocide activity for the acrylic copolymers, the lignin derivative iron lignosulfonate and ZnO nanoparticles, the obtained nanocomposites were biologically investigated and proposed as wood preservation agents.

A clean and efficient process for producing hydrogen using renewable energy sources is an important requirement for a future Hydrogen Economy. The production of hydrogen from water and solar energy is attracting widespread attention. In particular, research is focused on novel materials, or improving existing materials for the splitting of water using photocatalysis and photoelectrolysis. In this paper we highlight several recent developments in photocatalysts and we illustrate how engineering of properties on an atomic scale can be achieved by cation and anion doping, deviations from stoichiometry and in case of ternary or more complex materials, by deviations from molecularity. The defect chemistry of I-III-VI2 ternary semiconductors with the chalcopyrite structure is presented and used to construct a 3D-Brouwer diagram.

The paper is a review on the state-of-the-art on colored materials (absorbers and glazings) for solar thermal flat plate collectors obtained world-wide. The best results obtained by the group active in the R&D Centre Renewable Energy Systems and Recycling are also reported and they are related to the steps followed in developing and optimizing the absorber plate (substrate, the alumina matrix, the colored coatings and the anti-reflexion layer) and the glazing (as anti-reflexive coating and/or as colored component). These results represent a promising input for novel, market-acceptable flat plate solar-thermal collectors, with increased architectural acceptance, for facades integration in Nearly Zero Energy Buildings.

One main reason that limits their large scale application is the cost of the photocatalytic processes, mainly related to the costs of the UV radiation that activates most of the highly efficient photocatalytic materials and therefore, VIS-active photocatalysts are intensively studied; additionally, in industrial processes, fine powders are to be avoided although they have the advantage of larger specific areas, thus potential larger activity. This paper presents a review of the results obtained in the research group in optimizing photocatalysts used as thin films; doctor blade and spray pyrolysis deposition are comparatively analyzed. In situ doping using templating agents (surfactants) represented a viable path to extend the optoelectronic response towards VIS in wide band gap semiconductors. An additional advantage is morphology control reached when using surfactants. By associating two semiconductor photocatalysts as n-n tandems or n-p diode type materials, VIS-activated thin films can be obtained and the step-wise development of a novel family of VIS-active photocatalysts is presented for composite materials containing two or three components from the group of TiO2, WO3, SnO2, ZnO, CuxS.

Extensive research has been conducted on the removal of organic pollutants in water using heterogeneous photocatalysis. This study reviews some of the recent reports on TiO2 photocatalysis applied for degradation of pesticides. The role of the operating parameters in the optimization of the process, the strategies used to develop visible active titania based photocatalysts and various ways to increase the cost-effectiveness of the photocatalytic processes are discussed. From the papers reviewed it can be concluded that under optimal conditions high efficiency in the photodegradation of pesticides can be reached.

The paper presents the defect chemistry of CuInS2 (CIS) in relation to deviations from stoichiometry and molecularity. The Kroger-Vink notation is used for the point defect description. A first approach for the construction of a qualitative three-dimensional Brouwer diagram is presented. In the case of ternary materials, like CIS, the deviation from molecularity is expressed in the 3D-Brouwer diagram by the variation of the activity of the metal sulfide and the deviation from stoichiometry by the variation of the sulfur partial pressure. This model can be used as an important tool for tailoring the material synthesis in order to obtain desired opto-electrical properties.

Nernst-type chemical gas sensors comprise a reference electrode, a sensing electrode, and a functional solid electrolyte, which determines the high selectivity of this type of sensor. Taguchi-type chemical gas sensors have as the active material a mixed ionic-electronic conductor (MIEC) with two metallic electrodes, and this type of sensor exhibits a high sensitivity, but a poor selectivity. In order to optimize the electrical properties of the functional materials, usually doping is applied. Dopants will influence the defect chemistry of these materials by introducing ionic and/or electronic defects. After an introduction of intrinsic and extrinsic disorder and the Kroger-Vink defect notation, the defect chemistry of selected chemical gas sensor materials is presented in detail. In addition, electrodes for the electrochemical determination of organic pollutants in aqueous environments are presented.

Thin films of undoped and Al- and Ag-doped ZnO thin films have been obtained by spray pyrolysis deposition. The optimised parameters of deposition for the thin films to be used in optoelectronic applications are presented in the paper. The addition of low amounts of Al and Ag ions influences the film crystallinity and morphology. Based on the experimental results it is concluded that aluminium and silver act as dopants and reduce the band gap value of the host oxide, ZnO.

The CuSbS2 exhibits adequate properties as absorber material in solar cell applications. This paper describes the defect chemistry of the CuSbS2 using lattice reactions combined with electroneutrality conditions and equilibrium constants for each intrinsic defect formation mechanism. From the proposed reactions the conductivity type of the material is indicated: ionic conduction if the deviation from molecularity is the predominant defect formation mechanism and mixed ionic-electronic conductivity in the case of a deviation from stoichiometry, and in the case of the simultaneous occurrence of a deviation from molecularity and from stoichiometry.