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An eco-friendly process to recover valuable materials deriving from silicon based photovoltaic panels at end-of-life has been proposed. In particular, in this paper a new two-step process to separate and recover glass, Si and metals has been investigated and discussed. A preliminary mechanical treatment to remove fluorinated polymers allows to exclude dangerous emissions of hydrofluoric acid and fluorinated compounds coming out from conventional heat treatments. A subsequent thermal treatment allows the complete removal of the residual polymers and the separation of valuable materials. The influence of treatment time, temperature and atmosphere, during the polymers degradation has been evaluated and the by-products have been examined. The process efficiency has been assessed by determining the quantity and quality of the recovered materials. The results have shown that the combination of the two mechanical/thermal processes allows energy efficiency and environmental sustainability with respect to conventional recovery treatments. The optimal operating conditions for the thermal treatment have turned out 500 °C for 1 h in oxidizing atmosphere. The quality of the recovered materials has been determined by analysing the residual carbon content after the thermal treatment. The gaseous products of the polymeric degradation have been characterized by gas chromatography-mass spectrometry (GC–MS) analysis.

Self-assembled monolayers of 1H-indole-2,3-dione (isatin), 3-methyl 2-oxindole, and 7-fluoroisatin are observed on the Au(111) surface via scanning tunneling microscopy (STM). We observed that isatin forms pentamers with density functional theory providing support for a cyclic structure stabilized by both N–H···O and C–H···O hydrogen bonds between neighboring molecules. The C–H···O bond is made between the 7-position C–H acting as the hydrogen bond donor and the 3-position carbonyl as the hydrogen bond acceptor, and calculations show that the isatin pentamer structure is 12 kJ/mol more stable than the dimer. When the 3-position carbonyl is removed and replaced with a methyl group (3-methyl 2-oxindole), we observe a monolayer with a mixture of catemer chains and pentameric clusters that are qualitatively different from those of isatin. Pentamer formation is completely broken when the 7-position hydrogen is removed and replaced with fluorine; the monolayer of 7-fluoroisatin is composed of a mixture of close...

Although photovoltaic (PV) technology has been projected as one of the most promising candidates to replace conventional fossil based power generation, claims about the potential disadvantages of the PV panels end-of-life (EoL) deserve careful attention in order to fully establish a feasibility and viability baseline and support technological and implementation policies. The current challenge concerning PV technology resides in making them efficient and competitive in comparison with traditional power generation systems, without disregarding the appraisal of EoL impacts. The emergy analysis method proved to be a reliable approach for the evaluation of the efficiency, effectiveness and environmental friendliness of technological processes under a global scale perspective and may likely be applied to the EoL PV investigation as a complement of conventional energy and economic assessments. Therefore, this method was used in this study to evaluate the sustainability of a PV panel recycling process. In addition, this paper aims to explore the implications of methodological assumptions when Emergy Accounting (EMA) tackles waste management systems, in order to address the shortcomings in this field. Results show that the PV panel treatment can generate large environmental benefits not only at the local scale of the process, but also at the larger scale of the industrial manufacture and material recovery, as well as at the even larger scale of the biosphere where resources come from and pollution is released. The comparison between the emergy invested for electricity production via PV and fossil energy sources also including EoL resource and environmental costs, highlights that PV technology is competitive under both energy and environmental points of view. This comparison reveals that the solar technologies imply remarkable emergy savings (1.45E+12 sej/kWh for fossil sources versus 3.57E+11 sej/kWh for crystalline silicon photovoltaic down to 2.31E+11 sej/kWh for cadmium telluride photovoltaic). Results clearly show that PV solar power can be considered a mature technology and can favorably compete with other renewable and non-renewable options for electricity generation. However, efficiency improvements of PV panels thermal recovery are still possible and may lead to further decrease of still too large emergy costs of the treatment process, not to talk of potential recovery alternatives such as chemical treatment for silicon cells and better upstream industrial design.

The iconic helical structure of DNA is stabilized by the solvation environment, where a change in the hydration state can lead to dramatic changes to the DNA structure. X-ray diffraction experiments at cryogenic temperatures have shown crystallographic water molecules in the minor groove of DNA, which has led to the notion of a spine of hydration of DNA. Here, chiral nonlinear vibrational spectroscopy of two DNA sequences shows that not only do such structural water molecules exist in solution at ambient conditions but that they form a chiral superstructure: a chiral spine of hydration. This is the first observation of a chiral water superstructure templated by a biomolecule. While the biological relevance of a chiral spine of hydration is unknown, the method provides a direct way to interrogate the properties of the hydration environment of DNA and water in biological settings without the use of labels., Using chiral nonlinear spectroscopy, we discover a chiral water superstructure surrounding DNA at ambient conditions. This chiral spine of hydration is templated by the helical structure and provides a direct label-free probe of the solvation shell.

A series of experiments and electronic structure calculations were performed to identify metastable 1,1′-ferrocenedicarboxylic acid supramolecular structures formed during solution deposition in a vacuum on a Au(111) substrate, as well as to observe their evolution into more stable species under mild annealing conditions. Electrospray ionization mass spectrometry measurments were performed to determine which species are likely to be present in the rapidly evaporating droplet, and these experiments found that a hexamer can exist in solution during deposition, albeit as a metastable species. The molecular clusters present after solution deposition were observed and analyzed using ultrahigh-vacuum scanning tunneling microscopy, and the initial monolayer contains four basic classes of structures: ordered dimer domains, tilted dimer rows, square tetramers, and rectangular chiral hexamers. Electronic structure calculations indicate that the chiral hexamers consist of a central dimer surrounded by four molecules...

The reduction of sperm motility and count, or oligoasthenozoospermia, is one of the major causes of reduced fertility or infertility in men. Lipid composition of spermatozoa is important in determining their functional characteristics, in particular on motility, acrosomal exocytosis or fusogenic properties of the sperm. Here we investigated the levels of semen lipids in 11 infertile patients with severe oligoasthenozoospermia and 9 normozoospermic subjects with normal motility values. Sperm polar and neutral lipids were analyzed by thin-layer chromatography (TLC) and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Semen of patients with oligoasthenozoospermia showed a reduction of the degree of fatty acid unsaturation in the phospholipids chains that might affect the membrane fluidity. Furthermore, a significant higher cholesterol sulfate/seminolipid ratio was found in semen of oligoasthenozoospermic patients than in subjects with normal motility values, suggesting a critical role of sulfolipids in semen quality. The results may facilitate the understanding of the role of lipids on male fertility and offer interesting perspectives to find innovative treatments for oligoasthenozoospermia.

The structure, dynamics, and vibrational spectroscopy of dilute HOD, methanol, and ethanol in the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][NTf2], ionic liquid (IL) are ...

In previous papers in the series, the vibrational spectroscopy of CO2 in ionic liquids (ILs) was investigated at ambient conditions. Here, we extend these studies to understand the temperature dependence of the structure, dynamics, and thermodynamics of CO2 in the 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], IL. Using spectroscopic mapping techniques, the infrared absorption spectrum of the CO2 asymmetric stretch mode is simulated at a number of temperatures, and the results are found to be consistent with similar experimental studies. Structural correlation functions are used to reveal the thermodynamics of complete CO2 solvent cage breakdown. The enthalpy and entropy of activation for solvent cage reorganization are found to be 6.9 and 7.6 (kcal/mol)/K, respectively, and these values are similar to the those for spectral, orientational, and translational diffusion. Caging times for CO2 are calculated, and it is shown that the short time dynamics of CO2 are unaffected by temperature, even though the long-time dynamics are highly sensitive to temperature.

Orientador: Prof. Dr. Marcelo Luiz Curado Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Sociais Aplicadas, Programa de Pós-Graduação em Desenvolvimento Econômico. Defesa : Curitiba, 28/02/2019 Inclui referências: p.66-72 Área de concentração: Resumo: Durante os Governos Lula e o primeiro Governo Dilma os gastos tributários federais cresceram a taxas expressivas e ganharam representatividade na política fiscal, com diversos objetivos, dentre eles a busca por sustentar o crescimento econômico. O crescimento dos gastos tributários combinado à desaceleração do PIB no período pós-crise lançou a controvérsia sobre seus reais efeitos para a atividade. O objetivo do trabalho é fornecer subsídios a esta controvérsia pelo lado quantitativo a partir da estimação de um modelo que capte o efeito das desonerações para a taxa de crescimento do produto per capita de longo prazo. O trabalho constrói um modelo com dados em Painel adaptando Rocha e Giuberti (2007) e utiliza como principal fonte de dados para as desonerações tributárias os Demonstrativos dos Gastos Tributários, divulgados pela Receita Federal. Apesar das limitações, os resultados deram razão à hipótese de efeitos negativos e próximos de zero dos gastos tributários para a taxa de crescimento de longo prazo da economia. Quando elevado à valores extremos, os gastos tributários mantém ainda o efeito negativo e próximo de zero sugerindo uma relação linear. O resultados vão ao encontro do que já foi apontado na literatura sobre o tema que já sugeria a revisão dos atuais desenhos e das contrapartidas dos programas de incentivo fiscal em direção a estímulos ao investimento e inovação. Palavras chaves: gastos tributários, crescimento econômico Abstract: During Lula administrations and the first Dilma administration the Brazilian economy witnessed a significant increase in federal tax expenditures which gained prominence alongside a broad set of economic policy actions aimed at stimulating GDP growth. The tax expenditures growth also occurred alongside a deceleration of GDP in the post-crisis period. That fact has thrown controversy over the real effects of tax expenditures to foster growth rates in Brazil. The objective of the paper is to provide subsidies to this controversy on the quantitative side estimating a model that captures the effects of tax expenditures on the long-term growth rate of per capita GDP. A model with Panel data is constructed using the intuition of Rocha and Giuberti (2007) and data from the "Demonstrativos dos Gastos Tributários" which represents the officials reports with tax expenditures data published by the Brazilian's Revenue Service. Despite limitations, the main results of the paper gave rise to the hypothesis of negative and near-zero effects of tax expenditures on the economy's long-term growth rate. When raised to extreme values tax expenditures maintains the negative effect and close to zero effect suggesting a linear relationship. The results are in line with what has already been widely presented in the literature on the topic that suggested the revision of the shape and the counterparts of the current fiscal incentive programs putting them in direction of incentives to investiments and inovation. Key words: tax expenditures, economic growth

Unidad de excelencia María de Maeztu MdM-2015-0552 A key strategy towards sustainable urban development is designing cities for increased circular metabolism. The transformation of areas underused, such as urban rooftops, into productive spaces is being increasingly implemented as a result of associated multiple benefits. Rooftop greenhouses (RTGs) are an interesting option for exploiting urban rooftops with direct exposure to sunlight, reducing food miles and creating new agricultural spaces, while building-applied solar photovoltaic (BAPV) panels provide clean energy and reduce greenhouse gas emissions. However, a proper assessment of environmental costs and benefits related to both systems is vital for a successful implementation. By means of Life Cycle Assessment (LCA) method, modelled in the professional software SimaPro, this paper aims at comparing the environmental performance of different productive uses of rooftops under Mediterranean climatic conditions. The results showed that both systems are favourable and contribute to decreasing the environmental impacts thanks to the production of resources on-site. BAPV system shows the highest avoided burdens in comparison with RTG: for instance, the impacts generated by BAPV on climate change and fossil depletion categories, corresponding to - 430 kg CO₂ eq/m² and - 110 kg oil eq/m² respectively (versus - 22 kg CO₂ eq/m² and - 4.7 kg oil eq/m² in the RTG system), are around 20 times lower than RTG. Furthermore, a sensitivity analysis was performed through different scenarios, based on reductions or substitution of the most sensitive input flows, thus providing some useful tools for improved environmental performances. Attention to additional energy and material efficiency, in favour of the more environmentally sustainable choice, should remain a main point of investigation.

This work elucidates the molecular binding mechanism of CO2 in [C4C1IM][PF6] ionic liquid (IL) and its interplay with the CO2 asymmetric stretch frequency ν3, and establishes computational protocols for the reliable construction of spectroscopic maps for simulating ultrafast 2D-IR data of CO2 solvated in ILs. While charge transfer drives the static frequency shift between different ionic liquids (J. Chem. Phys. 2015, 142, 212425), we find here that electrostatic and Pauli repulsion effects dominate the dynamical frequency shift between different geometries sampled from the finite-temperature dynamics within a single ionic liquid. This finding is also surprising because dispersion interactions dominate the CO2–IL interaction energies, but are comparably constant across different geometries. An important practical consequence of this finding is that density functional theory is expected to be sufficiently accurate for constructing potential energy surfaces for CO2 in [C4C1IM][PF6], as needed for accurate an...

The primary challenge for connecting molecular dynamics (MD) simulations to linear and two-dimensional infrared measurements is the calculation of the vibrational frequency for the chromophore of interest. Computing the vibrational frequency at each time step of the simulation with a quantum mechanical method like density functional theory (DFT) is generally prohibitively expensive. One approach to circumnavigate this problem is the use of spectroscopic maps. Spectroscopic maps are empirical relationships that correlate the frequency of interest to properties of the surrounding solvent that are readily accessible in the MD simulation. Here, we develop a spectroscopic map for the asymmetric stretch of CO2 in the 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]) ionic liquid (IL). DFT is used to compute the vibrational frequency of 500 statistically independent CO2-[C4C1im][PF6] clusters extracted from an MD simulation. When the map was tested on 500 different CO2-[C4C1im][PF6] clusters, the c...

Rheumatoid arthritis is a chronic disease that results in a disabling and painful condition as it progresses to destruction of the articular cartilage and ankylosis of the joints. Although the cause of the disease is still unknown, evidence argues that autoimmunity plays an important part. There are increasing but contradictory views regarding serotonin being associated with activation of immunoinflammatory pathways and the onset of autoimmune reactions. We studied serotonin's involvement during collagen-induced arthritis in wild-type and Tph1(-/-) mice, which have markedly reduced peripheral serotonin levels. In wild-type mice, induction of arthritis triggered a robust increase in serotonin content in the paws combined with less inflammation. In Tph1(-/-) mice with arthritis, a marked increase in the clinical and pathologic arthritis scores was noticed. Specifically, in Tph1(-/-) mice with arthritis, a significant increase in osteoclast differentiation and bone resorption was observed with an increase in IL-17 levels in the paws and in Th17 lymphocytes in the draining lymph nodes, whereas T-regulatory cells were dampened. Ex vivo serotonin and agonists of the 5-HT2A and 5-HT2B receptors restored IL-17 secretion from splenocytes and Th17 cell differentiation in Tph1(-/-) mice. These findings indicate that serotonin plays a fundamental role in arthritis through the regulation of the Th17/T-regulatory cell balance and osteoclastogenesis.

In contrast with conventional liquids, ionic liquids have solvation dynamics with more rate dispersion and with average times that do not agree with dielectric measurements. A kinetic analog of multidimensional spectroscopy is introduced and used to look for heterogeneity in simulations of coumarin 153 in [Im12][BF4]. Strong heterogeneity is found in the diffusive solvation rate. An unanticipated heterogeneity in the amplitude of the inertial solvation is also seen. Both heterogeneities exchange at the same rate. This rate is similar to the mean diffusive solvation time, putting it in the intermediate-exchange region. Overall, there are multiple violations of the assumptions usually invoked in the theory of reaction dynamics.

Idiopathic scoliosis (IS) is the deformation and/or abnormal curvature of the spine that develops progressively after birth. It is a very common condition, affecting approximately 4% of the general population, yet the genetic and mechanistic causes of IS are poorly understood. Turner syndrome (TS) is caused by haploinsufficiency for a subset of genes within the pseudoautosomal region (PAR) at the tip of the short arm of the X chromosome thereby defining a critical interval for TS pathogenesis. Patients with TS present with a number of clinical features that individually represent common diseases, including an increased risk of developing IS. It is therefore important to assign genes within the TS critical interval to each of these disorders. Here, we focus on one gene within this interval, PPP2R3B, which encodes a protein phosphatase 2A regulatory subunit that interacts with the origin of replication component, CDC6, and has been linked to regulation of autophagy. We found that PPP2R3B is expressed at sites of chondrogenesis within human foetuses, including the vertebrae. We also demonstrated prominent expression in myotome and muscle fibres in human foetuses, and zebrafish embryos and adolescents. As there is no rodent orthologue of PPP2R3B, we used CRIPSR/Cas9-mediated gene-editing to generate a frameshift mutation in zebrafish ppp2r3b. Adolescent zebrafish that were homozygous for this mutation exhibited a fully penetrant kyphoscoliosis phenotype which became progressively worse over time, mirroring IS in humans. These defects were associated with reduced mineralisation of vertebrae, resembling osteoporosis. Electron microscopy demonstrated abnormal mitochondria adjacent to muscle fibres, a feature which is associated with muscular dystrophy. Collectively, our data support a role for PPP2R3B haploinsufficiency in human IS pathogenesis in TS, establish a new animal model of this condition and provide a basis to investigate the underlying mechanisms. Author Summary Abnormal curvature of the spine is extremely common, often developing as people age. The causes of this are not well understood and a major focus of active research is to identify the underlying genetic causes of this. In this study, we used gene-editing to create zebrafish carrying a mutation in the gene PPP2R3B. This is a gene linked to Turner syndrome in which patients develop spinal curvature, however, it has never been implicated in skeletal tissue maintenance before. Adolescent mutant zebrafish developed spinal curvature which became progressively worse, mirroring the human condition. This was associated with reduced formation of mineralised bone including an osteoporosis-like presentation within vertebrae. This was associated with prominent ppp2r3b expression in axial muscle and a muscular dystrophy-like phenotype. This work provides an experimental starting point to investigate the molecular and cellular mechanisms underlying spinal tissue integrity in future.

Idiopathic scoliosis (IS) is the deformation and/or abnormal curvature of the spine that develops progressively after birth. It is a very common condition, affecting approximately 4% of the general population, yet the genetic and mechanistic causes of IS are poorly understood. Turner syndrome (TS) is caused by haploinsufficiency for a subset of genes within the pseudoautosomal region (PAR) at the tip of the short arm of the X chromosome thereby defining a critical interval for TS pathogenesis. Patients with TS present with a number of clinical features that individually represent common diseases, including an increased risk of developing IS. It is therefore important to assign genes within the TS critical interval to each of these disorders. Here, we focus on one gene within this interval, PPP2R3B , which encodes a protein phosphatase 2A regulatory subunit that interacts with the origin of replication component, CDC6, and has been linked to regulation of autophagy. We found that PPP2R3B is expressed at sites of chondrogenesis within human foetuses, including the vertebrae. We also demonstrated prominent expression in myotome and muscle fibres in human foetuses, and zebrafish embryos and adolescents. As there is no rodent orthologue of PPP2R3B , we used CRIPSR/Cas9-mediated gene-editing to generate a frameshift mutation in zebrafish ppp2r3b . Adolescent zebrafish that were homozygous for this mutation exhibited a fully penetrant kyphoscoliosis phenotype which became progressively worse over time, mirroring IS in humans. These defects were associated with reduced mineralisation of vertebrae, resembling osteoporosis. Electron microscopy demonstrated abnormal mitochondria adjacent to muscle fibres, a feature which is associated with muscular dystrophy. Collectively, our data support a role for PPP2R3B haploinsufficiency in human IS pathogenesis in TS, establish a new animal model of this condition and provide a basis to investigate the underlying mechanisms. Author Summary Abnormal curvature of the spine is extremely common, often developing as people age. The causes of this are not well understood and a major focus of active research is to identify the underlying genetic causes of this. In this study, we used gene-editing to create zebrafish carrying a mutation in the gene PPP2R3B . This is a gene linked to Turner syndrome in which patients develop spinal curvature, however, it has never been implicated in skeletal tissue maintenance before. Adolescent mutant zebrafish developed spinal curvature which became progressively worse, mirroring the human condition. This was associated with reduced formation of mineralised bone including an osteoporosis-like presentation within vertebrae. This was associated with prominent ppp2r3b expression in axial muscle and a muscular dystrophy-like phenotype. This work provides an experimental starting point to investigate the molecular and cellular mechanisms underlying spinal tissue integrity in future.

In recent years, interest in carbon capture and sequestration has led to numerous investigations of the ability of ionic liquids to act as recyclable CO2-sorbent materials. Herein, we investigate the structure and dynamics of a model physisorbing ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1Im][PF6]), from the perspective of CO2 using two-dimensional (2D) IR spectroscopy and molecular dynamics simulations. A direct comparison of experimentally measured and calculated 2D IR line shapes confirms the validity of the simulations and spectroscopic calculations. Taken together, the simulations and experiments reveal new insights into the interactions of a CO2 solute with the surrounding ionic liquid and how these interactions manifest in the 2D IR spectra. In particular, higher CO2 asymmetric stretch vibrational frequencies are associated with softer, less populated solvent cages and lower frequencies are associated with tighter, more highly populated solvent cages. The CO2 interacts most...

The absorption of CO

Time-dependent Stokes shift (TDSS) measurements provide crucial insights into the dynamics of liquids. The interpretation of TDSS measurements is often aided by molecular dynamics simulations, where solvent response functions are computed either with an equilibrium or nonequilibrium approach. In the nonequilibrium approach, the solvent is at equilibrium with the ground electronic state of the solute and its charge distribution is instantaneously changed to that of the first excited state. The solvation response function is then calculated as a nonequilibrium average of the subsequent evolution of the solvent influence on the electronic energy gap. In the equilibrium approach, the normalized time correlation function of the fluctuations of the solvent-perturbed electronic energy gap is calculated. If the linear response approximation is valid, then the nonequilibrium solvation response function is identical to the equilibrium time correlation function. The nonequilibrium methodology conceptually mimics the experiment, but it is significantly more computationally expensive than the equilibrium approach. In multicomponent systems such as ionic liquids, it is natural to inquire how the various components affect the observed relaxation dynamics. When utilizing the nonequilibrium methodology, the solvation response naturally decomposes into a sum of responses for each component present in the system. However, the equilibrium time correlation function does not decompose unambiguously. Here, we have evaluated a decomposition strategy that is consistent with the linear response approximation for the study of solvation dynamics of coumarin 153 (C153) in the 1-ethyl-3-methyl imidazolium tetrafluoroborate, [emim][BF

Molecular dynamics (MD) simulations validated against two-dimensional infrared (2D-IR) measurements of CO

Traditionally, the goal of self-assembly and supramolecular chemistry is to engineer an equilibrium structure with a desired geometry and functionality; this is achieved through careful choice of molecular monomers, growth conditions, and substrate. Supramolecular assemblies produced under nonequilibrium conditions, in contrast, can form metastable structures with conformations quite different from those accessible in equilibrium self-assembly. The study of nonequilibrium growth of clusters potentially impacts the study of nucleation in atmospheric aerosols, nucleation in organic crystallization, and mesoscale organization for systems ranging from biological molecules to molecular electronics. In our experiments, we prepare surface monolayers of small organic and organometallic molecules through direct injection of a solution onto a substrate in high vacuum. During this process, the rapid evaporation of small solution droplets in high vacuum can lead to nonequilibrium growth conditions. The resulting structures are then characterized by scanning tunneling microscopy. Among the features observed in these experiments are cyclic, hydrogen-bonded pentamers. For carboxylic acids, the two-molecule ring dimer is the common binding motif. Large, cyclic hydrogen-bonded systems are uncommon, especially so for rings with five members. Despite this, pentagonal clusters appear to be a general phenomenon for systems containing adjacent strong and weak hydrogen-bonding elements on five-member aromatic rings. Regular pentamers have been observed as metastable structures for ferrocenecarboxylic acid, indole-2-carboxylic acid, and isatin (1-H-indole-2,3-dione). Electronic structure calculations confirm the relative stability of these structures with respect to the dimer or catemer conformations which are observed in the solid-state crystal structures. For ferrocenecarboxylic acid, cyclic pentamers undergo further self-assembly, resulting in long-range order in conjunction with local 5-fold rotational symmetry. This system is the first reported self-assembled molecular quasicrystal, and it remains the only example of a hydrogen-bonded quasicrystal. This supramolecular structure forms as a result of the cocrystallization of hydrogen-bonded cyclic pentamers with intercalated molecular dimers. The shared bonding to a single dimer is responsible for locking the adjacent pentamers in specific distances and orientations, which produces the quasicrystal. Careful analysis of experimental data provides evidence that, in some cases, metastable clusters are formed in solution and then subsequently adsorb on the surface. This is a unusual mechanism for supramolecular assembly, and it has important implications for understanding questions in crystal growth, namely: what the initial stages of crystal growth are as molecules are first precipitating from solution; what role the solvent plays in determining crystal structure; and whether solvent-mediated clustering is important in the broader phenomenon of solid-state polymorphism.

The pH-induced surface speciation of organic surfactants such as fatty acids and phospholipids in monolayers and coatings is considered to be an important factor controlling their interfacial organization and properties. Yet, correctly predicting the surface speciation requires the determination of the surface dissociation constants (surface pKa) of the protic functional group(s) present. Here, we use three independent methods - compression isotherms, surface tension pH titration, and infrared reflection-absorption spectroscopy (IRRAS) - to study the protonation state of dipalmitoylphosphatidic acid (DPPA) monolayers on water and NaCl solutions. By examining the molecular area expansion at basic pH, the pKa to remove the second proton of DPPA (surface pKa2) at the aqueous interface is estimated. In addition, utilizing IRRAS combined with density functional theory calculations, the vibrational modes of the phosphate headgroup were directly probed and assigned to understand DPPA charge speciation with increasing pH. We find that all three experimental techniques give consistent surface pKa2 values in good agreement with each other. Results show that a condensed DPPA monolayer has a surface pKa2 of 11.5, a value higher than previously reported (∼7.9-8.5). This surface pKa2 was further altered by the presence of Na+ cations in the aqueous subphase, which reduced the surface pKa2 from 11.5 to 10.5. It was also found that the surface pKa2 value of DPPA is modulated by the packing density (i.e., the surface charge density) of the monolayer, with a surface pKa2 as low as 9.2 for DPPA monolayers in the two-dimensional gaseous phase over NaCl solutions. The experimentally determined surface pKa2 values are also found to be in agreement with those predicted by Gouy-Chapman theory, validating these methods and proving that surface charge density is the driving factor behind changes to the surface pKa2.

Solar photovoltaic (PV) electricity has the potential to be a major energy solution, sustainably suitable for urban areas of the future. However, although PV technology has been projected as one of the most promising candidates to replace conventional fossil based power plants, the potential disadvantages of the PV panels end-of-life (EoL) have not been thoroughly evaluated. The current challenge concerning PV technology resides in making it more efficient and competitive in comparison with traditional fossil powered plants, without neglecting the appraisal of EoL impacts. Indeed, considering the fast growth of the photovoltaic market, started 30 years ago, the amount of PV waste to be handled and disposed of is expected to grow drastically. Therefore, there is a real need to develop effective and sustainable processes to address the needed recycle of the growing number of decommissioned PV panels. Many laboratory-scale or pilot industrial processes have been developed globally during the years by private companies and public research institutes to demonstrate the real potential offered by the recycling of PV panels. One of the tested up lab-scale recycling processes – for the crystalline silicon technology – is the thermal treatment, aiming at separating PV cells from the glass, through the removal of the EVA (Ethylene Vinyl Acetate) layer. Of course, this treatment may entail that some hazardous components, such as Cd, Pb, and Cr, are released to the environment, therefore calling for very accurate handling. To this aim, the sustainability of a recovery process for EoL crystalline silicon PV panels was investigated by means of Life Cycle Assessment (LCA) indicators. The overall goal of this paper was to compare two different EoL scenarios, by evaluating the environmental advantages of replacing virgin materials with recovered materials with a special focus on the steps and/or components that can be further improved. The results demonstrate that the recovery process has a positive effect in all the analyzed impact categories, in particular in freshwater eutrophication, human toxicity, terrestrial acidification and fossil depletion indicators. The main environmental benefits arise from the recovery of aluminum and silicon. In particular, the recovered silicon from PV waste panels would decrease the need for raw silicon extraction and refining in so lowering the manufacturing costs, and end-of-life management of PV panels. Moreover, the amount of the recovered materials (silicon, aluminum and copper, among others) suggests a potential benefit also under an economic point of view, based on present market prices.