The enhancement of excitonic emission crossing Saha equilibrium in trap passivated CH3NH3PbBr3 perovskite

Metal-halide semiconductor perovskites have received great attention for the development of stable and efficient light emitting diodes and lasers, since they combine high charge carrier mobility and light emission spectral-purity with low-cost fabrication methods. Nevertheless, the role of excitons, free carries and trap states in perovskite light emission properties is still unclear due to their interdependence. In this paper we selectively manage trapping and light emission mechanisms by a reversible laser-assisted trap-passivation process performed on a CH3NH3PbBr3 perovskite layer, coupled to the inner modes of a high-quality micro-cavity, which only affects the radiative recombination. We show that photoluminescence is dominated by exciton radiative decay process and that trap states passivation increases the exciton gemination rate by reducing coulombic scattering of free electrons due to the ionized impurities. This picture provides a more general description than the model based on trap states-free Saha thermodynamic equilibrium between photo-generated species. The interdependence of free carries, trap states and excitons in the light emission properties of CH3NH3PbBr3 perovskite thin films and their relationship to device performance is a subject of debate. Here, the authors investigate the role of non-radiative recombination and demonstrate that the photoluminescence is dominated by exciton radiative decay processes

Nanostructured Ni-Fe-P Alloy for Alkaline Electrolyzer

In recent years, the interest towards green hydrogen has drastically increased due to the global decarbonization process. Electrochemical water splitting is considered an attractive solution to convert and store the surplus energy from renewable energy sources. However, hydrogen production by water electrolysis is not economically sustainable. To reduce the cost of produced hydrogen, it is necessary to switch from noble-metal catalyst (Pt, Pd…) to cheap alternatives with a lower per unit energy cost but at the same time able to guarantee a high electrocatalytic activity for both oxygen and hydrogen evolution reactions. Among transition metals, nickel was selected as active material for its low cost and high chemical stability in alkaline media. Currently, the most investigated transition metal catalyst includes alloy of nickel with sulfide, phosphide, and nitride. In this work, a ternary alloy of Nickel-Iron-Phosphorus with nanowires morphology was investigated and compared to the binary alloy of Nickel-Iron. Ni-Fe-P NWs electrodes were obtained by potential-controlled pulse electrochemical deposition using polycarbonate membrane as template. Electrodes morphology and structure were studied by scanning electrode microscopy (SEM), energy diffraction spectroscopy (EDS) and X-ray diffraction (XRD). Electrodes were tested both as cathodes as anodes by Quasi Steady State Polarization (QSSP) and Galvanostatic Test. All the tests were performed in 30% w/w KOH aqueous solution at room temperature. Preliminary results showed better performance of the ternary alloy compared to the binary one

Ni-Fe-S alloy nanostructured electrodes for alkaline electrolyser

In recent years, renewable energy sources are becoming more and more relevant owing to the progressive decarbonization of energy processes to reduce CO2 emissions [1,2]. In this view, worldwide public authorities are encouraging the use of renewable energies by promoting laws and guidelines [3,4]. One of the main drawbacks of renewable sources is their unpredictability, consequently, interest in green hydrogen has drastically increased. One way to produce green hydrogen is by water electrolysis using only electricity from renewable sources. It is a viable strategy to take advantage of the surplus electricity from them. The most relevant part of the cost of electrochemical hydrogen comes from the electricity cost and catalysts. For this reason, research is focused on improving the performance of the electrolyzer, using more efficient and less expensive materials, such as transition metal alloys like Nickel-based alloy [5]. One way to improve the performance of electrolyzers is based on the development of nanostructured electrodes distinguishing for low cost and high electrocatalytic activity. The proposed technique for fabricating the electrodes is known as template electrosynthesis. The template used is a commercial porous polycarbonate membrane (PMC - Whatman, Cyclopore, 20 μm thick), which due to its morphology allows the formation of nanowire-shaped nanostructures, highly interconnected with each other, which have the advantage of possessing a high surface area (about two orders of magnitude higher than planar electrode with the same geometric area). To make the membrane conductive, a gold film of thickness around 20-30 nm is deposited on one of the template surfaces by a sputtering process. After sputtering, a compact nickel layer of thickness around 20 μm is electrodeposited on the gold side. This, in addition to ensuring adequate mechanical strength to the electrode, acts as a current collector. After the electrodeposition of the nickel collector, the next step is the electrodeposition of the NWs formed inside the template pores. In previous works, we have fabricated Ni nanowires by template electrosynthesis, featuring by very high surface area. Starting from the best-performing nickel-iron alloy previously studied [6], this work focuses on the fabrication of nickel-iron-sulfur electrodes. In an aqueous solution containing nickel and iron, a third element is added in different concentrations in order to obtain electrodes with different compositions. The chemical and morphological features of these nanostructured electrodes are carried out through scanning electrode microscopy (SEM) and energy diffraction spectroscopy (EDS) analyses, and those results will be presented and discussed. Subsequently, electrochemical and electrocatalytic tests (Cyclic Voltammetry (CV), Quasi Steady State Polarization (QSSP) and Galvanostatic Step) are carried to establish the best alloy composition and they are carried out for both hydrogen and oxygen evolution reactions. Then, a long-term test conducted at a constant current density in an aqueous solution of potassium hydroxide (30% w/w) will also be reported

Galvanic deposition of Chitosan-AgNPs as antibacterial coating

Thanks to mechanical properties similar human bones, metallic materials represent the best choice for fabrication of orthopedic implants. Although metals could be widely used in the field of biomedical implants, corrosion phenomena could occur, causing metal ions releasing around periprosthetic tissues leading, in the worst cases, to the development of infections. In these cases, patients need prolonged antibiotic therapies that may cause bacterial resistance. Preventing bacterial colonization of biomedical surfaces is the key to limiting the spread of infections. Antibacterial coatings have become a very active field of research, strongly stimulated by the increasing urgency of identifying alternatives to the traditional administration of antibiotics. Nowadays, the research was focused on coating science to deal with these issues. In particular, the development of the antibacterial composite coatings could be a viable way to provide not only a corrosion resistance but also an antibacterial action and biocompatibility. Chitosan is a great biomaterial used in medicine. It is a natural bioactive polymer and is the second most abundant in nature polysaccharide after cellulose. Chitosan comes from the deacetylation of chitin, a homopolymer of beta-(1-4)-N-acetyl-D-glucosamine, derived from exoskeleton of crustaceans. It is high biocompatible and it is also used in drug delivery. In addition, chitosan has chelating properties due to the amino groups of polysaccharide that are responsible of selective chelation with metal ions. In particular, the attention has been paid to silver nanoparticles for their high stability, low toxicity, biocompatibility and antibacterial properties. These ones are incorporated in polymeric matrix (e.g. chitosan) and they are capable to interact physically with cell walls of bacteria. In this study Chitosan-Silver nanoparticles composite coating on AISI 304L was investigated. These coatings were realized by an alternative method of deposition respect to traditional ones based on galvanic coupling. This process doesn’t request any external power supply and is very easy to carried out. The difference of the electrochemical redox potential between the substrate (cathode) and a sacrificial anode is the pivotal role of the process. Deposition rate is controlled by the ratio of cathodic and anodic area. In practice, electrons generated by anode corrosion flow towards to more noble metal thanks to a short-circuit. As soon electrons arrive to the cathode, the base electrogeneration reactions of nitrate ions and water molecules occur. Production of hydroxyl ions causes an increasing of pH at substrate/solution interface. Hence, deprotonation of amine group leads precipitation of chitosan (pKa=6.4) onto surface. At the same time, silver nanoparticles are incorporated in polymeric matrix of chitosan. Physical-chemical characterizations of the coatings were carried out in order to investigate morphology and chemical composition. In addition, corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were executed in a simulated body fluid to scrutinize the corrosion resistance. Furthermore, the release of silver nanoparticles from coating in SBF were studied

Fabrication of Ni-alloy nanostructured elecrodes for alkaline electrolizers

In last years, renewable energy sources are becoming more and more important owing to the progressive decarbonization of energy processes to reduce CO2 emissions [1,2]. In this view, governments and authorities all around the world are encouraging the use of renewable energies by promoting laws and initiatives for the most sustainable energy transition [3,4]. One of the main drawbacks of renewable sources is their unpredictability, consequently, interest in hydrogen has drastically increased. One way to produce green hydrogen is by water electrolysis using only electricity from renewable sources. It is a viable strategy to take advantage of the surplus electricity. The most relevant part of the cost of electrochemical hydrogen comes from the electricity cost and catalysts. For this reason, research is focused on improving the performance of the electrolyzer, using more efficient and less expensive materials, such as transition metal alloys like Nickel-based alloy [5]. One of the possible ways to improve the performance of electrolyzers is based on the development and fabrication of nanostructured electrodes with a low cost and high electrocatalytic activity. In previous works, Ni nanowires were fabricated by template electrosynthesis, featuring by very high surface area. Starting from the best-performing nickel-iron alloy previously studied [6], this work focuses on the fabrication of nickel-iron-sulfur electrodes. In an aqueous solution containing nickel and iron, a third element was added in different concentrations in order to obtain electrodes with different compositions. The chemical and morphological features of these nanostructured electrodes were studied through scanning electrode microscopy (SEM) and energy diffraction spectroscopy (EDS) analyses, and those results will be presented and discussed. Electrochemical and electrocatalytic tests (Cyclic Voltammetry (CV), Quasi Steady State Polarization (QSSP) and Galvanostatic Step) were carried out to establish the best alloy composition for both hydrogen and oxygen evolution reactions. Long-term tests performed at a constant current density in an aqueous solution of potassium hydroxide (30% w/w) will be also reported. Acknowledgments This research was funded by CNMS, Centro Nazionale per la Mobilità sostenibile (MUR, PNRR-M4C2, CN00000023), spoke 12 – innovative propulsion. References [1] A.T.D. Perera, R.A. Attalage, K.K.C.K. Perera, V.P.C.Dassanayake, “Designing standalone hybrid energy systems minimizing initialinvestment, life cycle cost and pollutant emission” Energy, 54, 2013, 237-248. [2] K. Bandara, T. Sweet, J. Ekanayake, “Photovoltaic applications for off-grid electrification using novel multi-level inverter technology with energy storage”, Renewable Energy, 37, 2012, 82-88 [3] P. Balcombe, D. Rigby, A. Azapagic, “Motivations and barriers associated with adopting microgeneration energy technologies in the UK”, Renewable and Sustainable Energy Reviews, 22, 2013, 655-666. [4] H. Meyar-Naimi, S. Vaez-Zadeh, “Sustainable development-based energy policy making frameworks, a critical review”, Energy Policy, 43, 2012, 351-361. [5] F. Safizadeh, E. Ghali, G. Houlachi, “Electrocatalysis developments for hydrogen evolution reaction in alkaline solutions – A Review”, International Journal of Hydrogen Energy, 40, 2015, 256–274. [6] B. Buccheri, F. Ganci, B. Patella, G. Aiello, P. Mandin, R. Inguanta, “Ni-Fe alloy nanostructured electrodes for water splitting in alkaline electrolyser”, Electrochimica Acta, Volume 388, 2021, 0013-4686

SERVIÇOS ECOSSISTÊMICOS NO PLANEJAMENTO INTEGRADO DO TERRITÓRIO METROPOLITANO: OFERTA, DEMANDA E PRESSÕES SOBRE A PROVISÃO DE ÁGUA NA REGIÃO METROPOLITANA DE CURITIBA

The search for the sustainability of human settlements, mainly urban areas, and of ecosystems as a whole, involves the adoption of integrating territorial strategies that take into account environmental, economic, social, and cultural aspects. The focus on ecosystem services can be an ally in strengthening the integrated vision of metropolitan territory and water as a key integrating element. In this context, this study aimed to propose a set of indicators for the assessment of natural capital and the supply and demand of the ecosystem water supply service for metropolitan regions, with the Metropolitan Region of Curitiba (MRC), Paraná, as the main focus. The set of indicators was selected from a theoretical basis based on literature review and subsequently validated by specialists using the Delphi method, with  electronic questionnaires sent in two rounds of validation. The validated indicators were later used to analyze the water supply in the MRC. Although the urban area concentrates the greatest demands for water resources, the surrounding municipalities are the largest real or potential providers of ecosystem services. Some municipalities, especially those located at the northern end of the MRC, stand out for their significant water availability. However, the analysis shows a trend of degradation of natural capital and consequent impairment of water supply in MCR. There is a need to broaden, in a large part of the region, the implementation of biodiversity protection policies, encourage the creation of new conservation units and strengthen the monitoring of land use and the search for innovative solutions to improve water management in the metropolis.A sustentabilidade dos assentamentos humanos, principalmente áreas urbanas, e dos ecossistemas como um todo envolve a adoção de estratégias territoriais integradoras, que levem em conta os aspectos ambientais, econômicos, sociais e culturais. O enfoque dos serviços ecossistêmicos pode ser aliado no fortalecimento da visão integrada do território metropolitano e da água como elemento-chave integrador. Nesse contexto, este estudo teve como objetivo a proposição de um conjunto de indicadores de avaliação de capital natural e da oferta e demanda do serviço ecossistêmico de provisão de água para regiões metropolitanas, tendo como recorte a Região Metropolitana de Curitiba (RMC) (PR). O conjunto de indicadores foi selecionado de uma base teórica pautada em levantamento bibliográfico e posteriormente validado por especialistas pelo método Delphi, com envio de questionários eletrônicos em duas rodadas de validação. Os indicadores validados foram utilizados posteriormente para análise da provisão de água na RMC. Embora a mancha urbana concentre as maiores demandas por recursos hídricos, os municípios do seu entorno são os maiores provedores reais ou potenciais de serviços ecossistêmicos. Alguns municípios, principalmente os localizados no extremo norte da RMC, destacam-se pela significativa disponibilidade hídrica. No entanto, a análise demonstra tendência de degradação do capital natural e consequente comprometimento na provisão de água na RMC. Há a necessidade de se ampliar, em grande parte da região, a implementação das políticas de proteção da biodiversidade, de se estimular a criação de novas unidades de conservação e de fortalecer o monitoramento do uso do solo e a busca por soluções inovadoras para melhorar a gestão da água na metrópole

Performance of Nickel-Iron nanostructured electrodes at different temperatures

In recent years, the whole world has been trying to reduce CO2 emissions through the global decarbonization of energy processes. In this view, the interest towards green hydrogen has drastically increased. One way to produce green hydrogen is by water electrolysis using only electricity from renewable sources. The storage of renewable solar or wind electricity is a major challenge to build a sustainable future energy system. The electrochemical production of hydrogen, through electrolysers, is a viable strategy to take advantage of the surplus electricity coming from renewable energy sources. Its production is pollution-free but is not economically viable. The development of more efficient electrolysers with low-cost electrode materials plays a key role. Catalysts must have such as good electrocatalytic properties, high conductivity, high availability, low cost, and good chemical stability. Nowadays, research is focused on improving the Alkaline Water Electrolysis (AE) to reduce the cost of electrode production. In alkaline environment it was demonstrated that, transition metals, and in particular Nickel or nickel based alloy nanostructured electrodes, have good and stable performances. Furthermore, industrial alkaline electrolysers work at temperatures between 40 and 90°C. Therefore, electrodes must be mechanically and chemically stable at these temperatures. An approach to improve AE performance consists on the fabbrication of nanostructured electrodes because they are characterized by high electrocatalytic activity due to the very high surface area. Starting from the results obtained in a previous work, the nanostructured alloy of NiFe was tested both as cathode and anode at three different temperatures (25 °C, 40 °C, 60 °C). Nanostructured electrodes were obtained through a simple and cheap method, template electrosynthesis, using a polycarbonate membrane as a template. NiFe electrodes morphology was studied by scanning electrode microscopy (SEM) and their composition was evaluated by energy diffraction spectroscopy (EDS) analyses. Later, the electrodes were characterized using various electrochemical techniques: Cyclic Voltammetry (CV), Quasi Steady State Polarization (QSSP) and Galvanostatic Step. To evaluate the mid-term behavior of the electrodes, especially at high temperatures, a constant current density was applied for 6 hours. In particular, -50 mA cm-2 for Hydrogen Evolution Reaction (HER) and 50 mA cm-2 for Oxygen Evolution Reaction (OER). All the tests were performed in 30% w/w KOH aqueous solution. Temperature increase plays a key role in increasing the efficiency of both anode and cathode reactions. As expected, the best result was obtained at 60 °C. Acknowledgments This research was funded by MUR, CNMS Centro Nazionale per la Mobilità sostenibile grant number CN0000002

SERVIÇOS ECOSSISTÊMICOS NO PLANEJAMENTO INTEGRADO DO TERRITÓRIO METROPOLITANO: OFERTA, DEMANDA E PRESSÕES SOBRE A PROVISÃO DE ÁGUA NA REGIÃO METROPOLITANA DE CURITIBA

The search for the sustainability of human settlements, mainly urban areas, and of ecosystems as a whole, involves the adoption of integrating territorial strategies that take into account environmental, economic, social, and cultural aspects. The focus on ecosystem services can be an ally in strengthening the integrated vision of metropolitan territory and water as a key integrating element. In this context, this study aimed to propose a set of indicators for the assessment of natural capital and the supply and demand of the ecosystem water supply service for metropolitan regions, with the Metropolitan Region of Curitiba (MRC), Paraná, as the main focus. The set of indicators was selected from a theoretical basis based on literature review and subsequently validated by specialists using the Delphi method, with  electronic questionnaires sent in two rounds of validation. The validated indicators were later used to analyze the water supply in the MRC. Although the urban area concentrates the greatest demands for water resources, the surrounding municipalities are the largest real or potential providers of ecosystem services. Some municipalities, especially those located at the northern end of the MRC, stand out for their significant water availability. However, the analysis shows a trend of degradation of natural capital and consequent impairment of water supply in MCR. There is a need to broaden, in a large part of the region, the implementation of biodiversity protection policies, encourage the creation of new conservation units and strengthen the monitoring of land use and the search for innovative solutions to improve water management in the metropolis.A sustentabilidade dos assentamentos humanos, principalmente áreas urbanas, e dos ecossistemas como um todo envolve a adoção de estratégias territoriais integradoras, que levem em conta os aspectos ambientais, econômicos, sociais e culturais. O enfoque dos serviços ecossistêmicos pode ser aliado no fortalecimento da visão integrada do território metropolitano e da água como elemento-chave integrador. Nesse contexto, este estudo teve como objetivo a proposição de um conjunto de indicadores de avaliação de capital natural e da oferta e demanda do serviço ecossistêmico de provisão de água para regiões metropolitanas, tendo como recorte a Região Metropolitana de Curitiba (RMC) (PR). O conjunto de indicadores foi selecionado de uma base teórica pautada em levantamento bibliográfico e posteriormente validado por especialistas pelo método Delphi, com envio de questionários eletrônicos em duas rodadas de validação. Os indicadores validados foram utilizados posteriormente para análise da provisão de água na RMC. Embora a mancha urbana concentre as maiores demandas por recursos hídricos, os municípios do seu entorno são os maiores provedores reais ou potenciais de serviços ecossistêmicos. Alguns municípios, principalmente os localizados no extremo norte da RMC, destacam-se pela significativa disponibilidade hídrica. No entanto, a análise demonstra tendência de degradação do capital natural e consequente comprometimento na provisão de água na RMC. Há a necessidade de se ampliar, em grande parte da região, a implementação das políticas de proteção da biodiversidade, de se estimular a criação de novas unidades de conservação e de fortalecer o monitoramento do uso do solo e a busca por soluções inovadoras para melhorar a gestão da água na metrópole

Gold nanowires-based sensor for quantification of H2O2 released by human airway epithelial cells

Hydrogen peroxide (H2O2) is a biomarker relevant for oxidative stress monitoring. Most chronic airway diseases are characterized by increased oxidative stress. To date, the main methods for the detection of this analyte are expensive and time-consuming laboratory techniques such as fluorometric and colorimetric assays. There is a growing interest in the development of electrochemical sensors for H2O2 detection due to their low cost, ease of use, sensitivity and rapid response. In this work, an electrochemical sensor based on gold nanowire arrays has been developed. Thanks to the catalytic activity of gold against hydrogen peroxide reduction and the high surface area of nanowires, this sensor allows the quantification of this analyte in a fast, efficient and selective way. The sensor was obtained by template electrodeposition and consists of gold nanowires about 5 high and with an average diameter of about 200 nm. The sensor has excellent properties in terms of reproducibility, repeatability and selectivity. The sensor was validated by quantifying the hydrogen peroxide released by human airways A549 cells exposed or not to the pro-oxidant compound rotenone. The obtained results were validated by comparing them with those obtained by flow cytometry after staining the cells with the fluorescent superoxide-sensitive Mitosox Red probe giving a very good concordance

Nanostructured Ni-Fe-S Based Electrode for Hydrogen Production by Water Electrolysis

Green hydrogen is a real alternative to change the current energy system. Electrochemical water splitting is considered an attractive solution to convert and store the surplus of renewable energy sources. However, hydrogen production by water electrolysis is not economically sustainable due to the use of high noble metals as catalysts (generally platinum or palladium). In order to reduce costs, in this work we have synthesized a ternary alloy of nickel, iron and sulfur and used it as the cathode in an alkaline electrolyzer to produce hydrogen from water. Furthermore, to increase the features of the proposed alloy, this material was synthesized into the pore of a polycarbonate membrane to obtain a nanostructured electrode that exposes a very high surface area to the solution and consequently a large number of electrocatalytic active sites. The electrode fabrication was carried out by potential-controlled pulsed electrochemical deposition where the potential switch from -0.45 V to -1.3 V vs. SCE for 60 cycles. The electrode was characterized by SEM and EDS showing the nanostructured nature and the composition of the electrode. Then it was tested as the cathode in an alkaline electrolyzer (30% KOH) at room temperature. Preliminary results show that the addition of sulfur to the alloy permits to increase in the electrode features compared to the binary alloy of nickel and iron