Electronic structure and interfacial features of triphenylamine- and phenothiazine-based hole transport materials for methylammonium lead iodide perovskite solar cells.

Recently, great research efforts have been devoted to perovskite solar cells (PSCs) leading to sunlight-to-power conversion efficiencies above 25%. However, several barriers still hinder the full deployment of these devices. Critical issues are related to PCE stability and device lifetimes, which could be improved by targeted engineering of the hole transport material (HTM). Indeed, the HTM is not only responsible for transporting holes and preventing direct contact between the photo-active perovskite and the charge collector layer, but it plays important structural and protective roles too. As alternatives to the widely used yet expensive and unstable Spiro-OMeTAD, organic HTMs based on triphenylamine (TPA) and phenothiazine (PTZ) moieties have been proposed. However, their performances in PSC devices, and in particular their interfacial properties with the most popular methylammonium lead iodide perovskite (MAPI) still need investigations to be fully determined. In this framework, here we report a first-principles study on the structural and the electronic properties of a recently designed TPA and PTZ-based HTM (HTM1) and its interface with the MAPI (001) surface, considering both the PbI2- and the MAI-terminations. We also addressed already known HTM molecular systems to allow for a direct comparison with the recently proposed HTM1: we characterized the molecular parameters and the MAPI/HTM interfacial properties for Spiro-OMeTAD, PTZ1, and PTZ2. Our results suggest that good adhesion properties do not ensure effective and efficient MAPI-HTM hole injection. Despite the theoretical good alignment between HTM1 HOMO and MAPI valence band edge, our results for the mutually polarized interface point out the lack of a sufficient driving force for hole transport. While the hole mobility of HTM1 outperforms those of the other HTM molecules, for this HTM molecule, our findings suggest the application of lead halide perovskite compositions other than MAPI, with substituents that lower its valence band maximum potential value.

The critical issue of using lead for sustainable massive production of perovskite solar cells: a review of relevant literature.

This work aims to review the most significant studies dealing with the environmental issues of the use of lead in perovskite solar cells (PSCs). A careful discussion and rationalization of the environmental and human health toxicity impacts, evaluated by life cycle assessment and risk assessment studies, is presented. The results of this analysis are prospectively related to the possible future massive production of PSC technology.

Environmental and economic optima of solar home systems design: A combined LCA and LCC approach.

This paper compares the economic and environmental optimal design of Solar Home Systems (SHSs) and explores the role of economic incentives (such as tariffs and technology costs) in approximating the two optima. To achieve that, we present a methodology for the environmental and economic evaluation of grid-connected SHSs: user-scale electric systems involving a photovoltaic (PV) power system and a battery energy storage system. The proposed methodology is based on a mixed integer linear programming (MILP) optimization, life cycle assessment and life cycle costing. This methodological framework is applied to a case study involving a typical SHS installation in Italy. The results of the environmental optimal design brought to the evaluation of a 3.25 kW PV assisted by 8.66 kWh of nickel cobalt manganese batteries, whereas the costs of the SHS are minimized by a small PV system (less than 1 kW). Results underline that the environmental optimal configurations rely on battery technologies, which entails a significant cost compared to the grid connection. In contrast, the economic optimal design solutions is less impactful than the grid mix both from an environmental and economic points of view. Thanks to a reduction of batteries and PV costs, the environmental impact of the economic optimal design is expected to decrease in the future.

Life Cycle Inventories datasets for future European electricity mix scenarios.

Datasets concerning the European electricity mix, built employing the Ecoinvent database v.3.3 processes, are reported in this paper. Foreseen future scenarios are modelled based on acknowledged projections for energy market in Europe in 2050. These electricity mix data inventories could be useful for any academic or stakeholder interested in performing long-term prospective assessment of innovative generation technologies in the future European energy market.

Combined LCA and Green Metrics Approach for the Sustainability Assessment of an Organic Dye Synthesis on Lab Scale.

New generation photovoltaic devices have attracted much attention in the last decades since they can be efficiently manufactured employing abundant raw materials and with less-energy intensive processes. In this context, the use of powerful environmental assessment is pivotal to support the fine-tuning of solar cells fabrication and hit the target of manufacturing effective sustainable technological devices. In this work, a mass-based green metrics and life cycle assessment combined approach is applied to analyze the environmental performances of an innovative synthetic protocol for the preparation of organic dye TTZ5, which has been successfully proposed as sensitizer for manufacturing dye sensitized solar cells. The new synthetic strategy, which is based on the C-H activation process, has been compared with the previously reported synthesis employing classic Suzuki-Miyaura cross-coupling chemistry. Results highlight the contribution of direct energy consumption and purification operations in organic syntheses at lab scale. Furthermore, they demonstrate the usefulness of the environmental multifaceted analytic tool and the power of life cycle assessment to overcome the intrinsic less comprehensive nature of green metrics for the evaluation of organic synthetic protocols.

Paramagnetism and Relaxation Dynamics in Melanin Biomaterials.

Spectroscopical characterization of melanins is a prior requirement for the efficient tailoring of their radical scavenging, ultraviolet-visible radiation absorption, metal chelation, and natural pigment properties. Electron paramagnetic resonance (EPR), exploiting the common persistent paramagnetism of melanins, represents the elective standard for the structural and dynamical characterization of their constituting radical species. Although melanins are mainly investigated using X-band (9.5 GHz) continuous wave (CW)-EPR, an integration with the application of Q-band (34 GHz) in CW and pulse EPR for the discrimination of melanin pigments of different compositions is presented here. The longitudinal relaxation times measured highlight faster relaxation rates for cysteinyldopa melanin, compared to those of the most common dopa melanin pigment, suggesting pulse EPR spin-lattice relaxation time measurements as a complementary tool for characterization of pigments of interest for biomimetic materials engineering.

Life Cycle Inventory datasets for nano-grid configurations.

Datasets concerning some user-scale Smart Grids, named Nano-grids, are reported in this paper. First several Solar Home Systems composed of a photovoltaic plant, a backup generator and different types of lithium-ion batteries are provided. Then, the inventory analysis of hybrid Nano-grids integrating batteries and hydrogen storage is outlined according to different scenarios. These data inventory could be useful for any academic or stakeholder interested in reproducing this analysis and/or developing environmental sustainability assessment in the field of Smart Grids. For more insight, please see "Environmental analysis of a Nano-Grid: a Life Cycle Assessment" by Rossi F, Parisi M.L., Maranghi S., Basosi R., Sinicropi A. [1].

Environmental analysis of a nano-grid: A Life Cycle Assessment.

Renewable energy sources are fundamental to face the problem of climate changes. Unfortunately, some resources, such as wind and solar radiation, have fluctuations affecting the electrical grids stability. Energy storage systems can be used for a smart energy management to accumulate power from renewable sources. For such reason, these devices play a key role to achieve a sustainable electric system. On the other hand, they are affected by some environmental drawbacks mainly connected with the depletion of rare and expensive materials. Based on these considerations, in this study a nano-grid composed by a photovoltaic plant, a backup generator and an energy storage system is analysed by an environmental Life Cycle Assessment approach. A Solar Home System is designed, and its environmental profile is evaluated considering several Lithium-ion batteries. Among them, nickel-cobalt aluminium oxide cells resulted to be the most suitable solution for a Solar Home System (46.66 Pts/MWh). Moreover, a sensitivity analysis of the Solar Home System is performed and a hybrid energy storage plant integrating hydrogen and batteries is proposed to face the problem of seasonal solar radiation variability. Four scenarios having different gas pressure levels and lifespan of the devices are considered. Results show that currently the most sustainable configuration is represented by the Solar Home System, but in the future a hybrid nano-grid equipped with 700 bar hydrogen storage might be the best off-grid configuration for minimizing the impact on the environment (37.77 Pts/MWh). Extending the perspective of our analysis to future on-grid potential configurations, an efficient connection of the Solar Home System with a smart-grid is assessed as it looks more sustainable than other off-grid solutions (22.81 Pts/MWh).

Addition of new catalytic sites on the surface of versatile peroxidase for enhancement of LRET catalysis.

Versatile peroxidase (VP) from Bjerkandera adusta is an enzyme able to oxidize bulky and high-redox substrates trough a Long-Range Electron Transfer (LRET) pathway. In this study, the introduction of radical-forming aromatic amino acids by chemical modification of the protein surface was performed, and the catalytic implications of these additional surface active-sites on the oxidation of 2,6-dimethylphenol, Mn2+ and Remazol Brilliant Blue R (RBBR) were determined. These three different substrates are oxidized in different active-sites of enzyme molecule, of which the high redox RBBR the only one that is transformed by an external radical formed on the protein surface. Both catalytic constants kcat and KM were significantly affected by the chemical modifications. Tryptophan- and tyrosine-modified VP showed higher catalytic transformation than the unmodified enzyme for RBBR, while the Mn2+ oxidation was significantly reduced by all chemical modifications. Electron Paramagnetic Resonance studies demonstrated the formation of additional protein-based radicals after the chemical modification with radical-forming amino acids. In addition, the catalytic rate of the LRET-mediated transformation showed a good correlation with the ionization energy of the additional amino acid on the protein surface.

New Blue Donor-Acceptor Pechmann Dyes: Synthesis, Spectroscopic, Electrochemical, and Computational Studies.

The design, synthesis, and characterization of a new class of blue-colored thiophene-substituted Pechmann dyes are reported. Due to a distinguishing blue coloration and the capability to absorb light in one of the most photon-dense regions of the solar spectrum, such compounds are of great interest for application as photoactive materials in organic optoelectronics, in particular, in dye-sensitized solar cells. To achieve fine tuning of the optical and electrochemical properties, the electron-poor thiophene-bis-lactone moiety has been decorated with donor (D) and acceptor groups (A), targeting fully conjugated D-A-π-A structures. The designed structures have been investigated by means of DFT and time-dependent DFT calculations, and the most promising dyes have been synthesized. These molecules represent the very first preparation of unsymmetrical Pechmann derivatives. Optical and electrochemical properties of the new dyes have been studied by cyclic voltammetry and UV-vis and fluorescence spectroscopy. In two cases, test cells were built proving that a photocurrent can indeed be generated when using electrolytes especially formulated for narrow-band-gap dyes, although with a very low efficiency.

Data analysis of atmospheric emission from geothermal power plants in Italy.

Electric production from geothermal energy is still little exploited compared to its large potential and to the World renewable energy production from other sources. Some countries have exploited this energy source in order to enhance their transition to renewables. Today the largest geothermal energy producers in the world are New Zealand, U.S.A, Mexico, Philippines, Italy, Iceland, and, more recently, Turkey (Geothermal, 2012). Differently from other renewable sources, geothermal energy produces impacts on the environment that are very site-specific because of the nature of the resource and its geological characteristics Bravi et al.,2010; Parisi et al.,2013. In the same way, the atmospheric emissions associated to the activity of geothermal power plants for electric or heat production (mainly CO2, H2S, NH3, Hg, CH4) are also site-specific. In fact, due to technological and geographical differences among the geothermal installations operating all over the World, it is quite impossible to identify and attribute typical emission patterns, to perform forecasts valid for multiple sites or to collect universal data. Furthermore, it is virtually impossible the comparison among technologies located in different regions or countries. Definitively, inventories of primary data, as accurate and complete as possible, are essential to correctly evaluate the peculiarities of geo-thermoelectric energy production Parisi et al.,2018. Data reported here try to fill the gap in respect to the Italian situation. To this end, a complete survey of the atmospheric emissions from all the geothermal power plants in operation in the Tuscany Region is performed. In addition to data reporting, also some statistical analysis is performed to process data and to operate a further level of simplification which averages the emissions on the basis of geothermal sub-areas. The data collected is related to the research article "Life cycle assessment of atmospheric emission profiles of the Italian geothermal power plants" Parisi et al.,2019.

Spectroscopic Characterisation of the Naphthalene Dioxygenase from Rhodococcus sp. Strain NCIMB12038.

Polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, are potential health risks due to their carcinogenic and mutagenic effects. Bacteria from the genus Rhodococcus are able to metabolise a wide variety of pollutants such as alkanes, aromatic compounds and halogenated hydrocarbons. A naphthalene dioxygenase from Rhodococcus sp. strain NCIMB12038 has been characterised for the first time, using electron paramagnetic resonance (EPR) spectroscopy and UV-Vis spectrophotometry. In the native state, the EPR spectrum of naphthalene 1,2-dioxygenase (NDO) is formed of the mononuclear high spin Fe(III) state contribution and the oxidised Rieske cluster is not visible as EPR-silent. In the presence of the reducing agent dithionite a signal derived from the reduction of the [2Fe-2S] unit is visible. The oxidation of the reduced NDO in the presence of O2-saturated naphthalene increased the intensity of the mononuclear contribution. A study of the "peroxide shunt", an alternative mechanism for the oxidation of substrate in the presence of H2O2, showed catalysis via the oxidation of mononuclear centre while the Rieske-type cluster is not involved in the process. Therefore, the ability of these enzymes to degrade recalcitrant aromatic compounds makes them suitable for bioremediative applications and synthetic purposes.

Spectroscopic Characterization of Natural Melanin from a Streptomyces cyaneofuscatus Strain and Comparison with Melanin Enzymatically Synthesized by Tyrosinase and Laccase.

An actinobacteria strain was isolated from Algerian Sahara soil and assigned to Streptomyces cyaneofuscatus Pridham et al. 1958 species. This strain was selected for its ability to produce melanin exopigments in liquid and solid media. Melanin synthesis was associated with tyrosinase activity and the enzyme from this strain was isolated and biochemically characterized. Synthetic melanin was then enzymatically produced using the S. cyaneofuscatus Pridham et al. 1958 tyrosinase. As this enzyme showed a higher diphenolase activity, a synthetic melanin from the enzymic oxidation of 3,4-dihydroxyphenylalanine (dopa) was obtained by the use of a Trametes versicolor (L.) Lloyd laccase for comparison. The natural and synthetic pigments were physico-chemically characterized by the use of ultraviolet (UV)-Visible, and Fourier transform infrared (FT-IR) and multifrequency electron paramagnetic resonance (EPR) spectroscopies. All the melanin samples displayed a stable free radical when analyzed by X-band EPR spectroscopy. Once the samples were recorded at Q-band EPR, a copolymer derived from a mixture of different constituents was evident in the natural melanin. All radical species were analyzed and discussed. The use of water-soluble melanin naturally produced by S. cyaneofuscatus Pridham et al. 1958 represents a new biotechnological alternative to commercial insoluble pigments.

Photoinduced excitation and charge transfer processes of organic dyes with siloxane anchoring groups: a combined spectroscopic and computational study.

Dye-sensitized solar cells (DSSCs) have attracted significant interest in the last few years as effective low-cost devices for solar energy conversion. We have analyzed the excited state dynamics of several organic dyes bearing both cyanoacrylic acid and siloxane anchoring groups. The spectroscopic properties of the dyes have been studied both in solution and when adsorbed on a TiO2 film using stationary and time-resolved techniques, probing the sub-picosecond to nanosecond time interval. The comparison between the spectra registered in solution and on the solid substrate evidences different pathways for energy and electron relaxation. The transient spectra of the TiO2-adsorbed dyes show the appearance of a long wavelength excited state absorption band, attributed to the cationic dye species, which is absent in the spectra measured in solution. Furthermore, the kinetic traces of the samples adsorbed on the TiO2 film show a long decay component not present in solution which constitutes indirect evidence of electron transfer between the dye and the semiconductor. The interpretation of the experimental results has been supported by theoretical DFT calculations of the excited state energies and by the analysis of molecular orbitals of the analyzed dye molecules.

Tyrosine or Tryptophan? Modifying a Metalloradical Catalytic Site by Removal of the Cys-Tyr Cross-Link in the Galactose 6-Oxidase Homologue GlxA.

The concerted redox action of a metal ion and an organic cofactor is a unique way to maximize the catalytic power of an enzyme. An example of such synergy is the fungal galactose 6-oxidase, which has inspired the creation of biomimetic copper oxidation catalysts. Galactose 6-oxidase and its bacterial homologue, GlxA, possess a metalloradical catalytic site that contains a free radical on a covalently linked Cys-Tyr and a copper atom. Such a catalytic site enables for the two-electron oxidation of alcohols to aldehydes. When the ability to form the Cys-Tyr in GlxA is disrupted, a radical can still be formed. Surprisingly, the radical species is not the Tyr residue but rather a copper second-coordination sphere Trp residue. This is demonstrated through the introduction of a new algorithm for Trp-radical EPR spectra simulation. Our findings suggest a new mechanism of free-radical transfer between aromatic residues and that the Cys-Tyr cross-link prevents radical migration away from the catalytic site.

Life Cycle Assessment of second generation bioethanol produced from low-input dedicated crops of Arundo donax L.

This work presents a Life Cycle Assessment (LCA) of bioethanol (EtOH) from perennial Arundo donax L. feedstock. A "cradle-to-wheel" approach was applied considering primary data for the cultivation of dedicated crops on hilly marginal lands and innovative "second generation technologies" for feedstock conversion into EtOH. The goals of the study were to: (i) quantify impacts of lignocellulosic EtOH production/use chain, (ii) identify hotspots and (iii) compare the environmental performance of different bioethanol-gasoline vehicles, E10 (10% EtOH and 90% gasoline) and E85 (85% EtOH and 15% gasoline), with a conventional gasoline passenger car. Results for E85 underlined that the feedstock production and the use phase were the prevailing contributors, whilst for E10 the gasoline production phase shared the largest part of impacts. The comparison showed that vehicles using lignocellulosic bioethanol have potentially significant benefits on global warming, ozone depletion, photochemical oxidant formation and fossil depletion in respect to conventional passenger car.

LCA of 1,4-Butanediol Produced via Direct Fermentation of Sugars from Wheat Straw Feedstock within a Territorial Biorefinery.

The bio-based industrial sector has been recognized by the European Union as a priority area toward sustainability, however, the environmental profile of bio-based products needs to be further addressed. This study investigated, through the Life Cycle Assessment (LCA) approach, the environmental performance of bio-based 1,4-butanediol (BDO) produced via direct fermentation of sugars from wheat straw, within a hypothetical regional biorefinery (Campania Region, Southern Italy). The aim was: (i) to identify the hotspots along the production chain; and (ii) to assess the potential environmental benefits of this bio-based polymer versus the reference conventional product (fossil-based BDO). Results identified the prevailing contribution to the total environmental load of bio-based BDO in the feedstock production and in the heat requirement at the biorefinery plant. The modeled industrial bio-based BDO supply chain, showed a general reduction of the environmental impacts compared to the fossil-based BDO. The lowest benefits were gained in terms of acidification and eutrophication, due to the environmental load of the crop phase for feedstock cultivation.

Redox-Active Sites in Auricularia auricula-judae Dye-Decolorizing Peroxidase and Several Directed Variants: A Multifrequency EPR Study.

Peroxide-activated Auricularia auricula-judae dye-decolorizing peroxidase (DyP) forms a mixed Trp377 and Tyr337 radical, the former being responsible for oxidation of the typical DyP substrates (Linde et al. Biochem. J., 2015, 466, 253-262); however, a pure tryptophanyl radical EPR signal is detected at pH 7 (where the enzyme is inactive), in contrast with the mixed signal observed at pH for optimum activity, pH 3. On the contrary, the presence of a second tyrosine radical (at Tyr147) is deduced by a multifrequency EPR study of a variety of simple and double-directed variants (including substitution of the above and other tryptophan and tyrosine residues) at different freezing times after their activation by H2O2 (at pH 3). This points out that subsidiary long-range electron-transfer pathways enter into operation when the main pathway(s) is removed by directed mutagenesis, with catalytic efficiencies progressively decreasing. Finally, self-reduction of the Trp377 neutral radical is observed when reaction time (before freezing) is increased in the absence of reducing substrates (from 10 to 60 s). Interestingly, the tryptophanyl radical is stable in the Y147S/Y337S variant, indicating that these two tyrosine residues are involved in the self-reduction reaction.

EPR and LC-MS studies on the mechanism of industrial dye decolorization by versatile peroxidase from Bjerkandera adusta.

The mechanisms of industrial dye transformation by versatile peroxidase were elucidated. Purified versatile peroxidase from Bjerkandera adusta was able to decolorize different classes of dyes including azo and phthalocyanines, but unable to transform any of the anthraquinones tested. Kinetic constants for selected dyes were determined and the transformation products were analyzed by EPR spectroscopy and mass spectrometry. The EPR and MS analyses of the enzymatic decolorization products showed the cleavage of the azo bond in azo dyes and the total disruption of the phthalocyaninic ring in phthalocyanine dyes. The EPR analysis on two copper-containing dyes, reactive violet 5 (azo) and reactive blue 72 (phthalocyanine), showed that the transformation can or not break the metal-ion coordination bond according the dye nature. The role of the catalytic Trp172 in the dye transformation by a long-range electron transfer pathway was confirmed and the oxidation mechanisms are proposed and discussed.

Spectroscopic and computational characterization of laccases and their substrate radical intermediates.

Laccases are multicopper oxidases which oxidize a wide variety of aromatic compounds with the concomitant reduction of oxygen to water as by-product. Due to their high stability and biochemical versatility, laccases are key enzymes to be used as eco-friendly biocatalyst in biotechnological applications. The presence of copper paramagnetic species in the catalytic site paired with the substrate radical species produced in the catalytic cycle makes laccases particularly attractive to be studied by spectroscopic approaches. In this review, the potentiality of a combined multifrequency electron paramagnetic spectroscopy /computational approach to gain information on the nature of the catalytic site and radical species is presented. The knowledge at molecular level of the enzyme oxidative process can be of great help to model new enzymes with increased efficiency and robustness.