Formamidinium (FA)-based perovskites exhibit significant potential for highly efficient photovoltaics due to their promising optoelectronic properties and optimal bandgap. However, the undesired inactive phase arises from multiple crystal nucleation pathways formed by various intermediate phases during the film formation process, persistently accompanying it. FA-based perovskites frequently struggle to form uniform, highly crystalline films. This challenge complicates the development of reliable and highly reproducible crystallization processes for perovskites and the establishment of guidelines for controlling the α-phase formation. In this work, we investigate the role of poly(acrylonitril-co-methyl acrylate) (PAM) to simultaneously control nucleation and subsequent α-phase crystallization. This successfully demonstrates the regulation of oriented crystal growth through the creation of a PAM-PbI2 intermediate. Ultimately, PAM-modified p–i–n architecture devices obtain a promising power conversion efficiency (PCE) of 25.30%, with VOC (1.211 V), achieving 95% of the detailed balance limit. Additionally, PAM-modified devices maintain ≥90% of the initial efficiency for 1000 h under 1 sun and 65 °C operation.
Photodynamic inactivation of bacteria (PIB) proves to be an additional method to kill pathogenic bacteria. PIB requires photosensitizer molecules that effectively generate reactive oxygen species like singlet oxygen when exposed to visible light. To allow a broad application in medicine, photosensitizers should be safe when applied in humans. Substances like vitamin B2, which are most likely safe, are known to produce singlet oxygen upon irradiation. In the present study, we added positive charges to flavin derivatives to enable attachment of these molecules to the negatively charged surface of bacteria. Two of the synthesized flavin derivatives showed a high quantum yield of singlet oxygen of approximately 75%. Multidrug resistant bacteria like MRSA (Methicillin resistant Staphylococcus aureus), EHEC (enterohemorrhagic Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii were incubated with these flavin derivatives in vitro and were subsequently irradiated with visible light for seconds only. Singlet oxygen production in bacteria was proved by detecting its luminescence at 1270 nm. After irradiation, the number of viable bacteria decreased up to 6 log10 steps depending on the concentration of the flavin derivatives and the light dosimetry. The bactericidal effect of PIB was independent of the bacterial type and the corresponding antibiotic resistance pattern. In contrast, the photosensitizer concentration and light parameters used for bacteria killing did not affect cell viability of human keratinocytes (therapeutic window). Multiresistant bacteria can be safely and effectively killed by a combination of modified vitamin B2 molecules, oxygen and visible light, whereas normal skin cells survive. Further work will include these new photosensitizers for topical application to decolonize bacteria from skin and mucosa.
Experiments in the Fe–Ni–Cu–S system were performed to identify the role of the metal/S atomic ratio on monosulphide–melt partition coefficients and closed-system fractionation paths. In accord with previous work, DCu is ∼0·2 at all temperatures and all metal/S ratios. DNi is highly sensitive to temperature and metal/S, and changes from ∼0·6 at high metal/S and high temperature to >2 at low temperature and low metal/S. The temperature at which the cross-over in DNi occurs is sensitive to S2 fugacity. The monosulphide solid solution (mss)–melt partition coefficients of the platinum group elements (DPGE) are determined with laser-ablation inductively coupled plasma mass spectrometry calibrated on synthetic sulphide standards. At trace element concentration levels, the DPGE are largely insensitive to metal/S, contrary to previous experiments with PGE concentrations in the percentage range. Pt and Pd are highly incompatible with mss (D < 0·1) whereas Ir, Ru, and Rh are compatible, ranging from >3 to ∼10. The chemical differentiation paths of Fe–Ni–Cu–S sulphide melts experiencing mss fractionation are determined by the metal/S parent melt ratio. Oxidized sulphide melts with metal/S < 1 solidify in the stability field of intermediate solid solution (iss) whereas reduced sulphide melts with metal/S > 1 may fractionate past iss stability. The latter will accumulate Ni together with Cu down to solidus temperature. Toward the end of their fractionation path, they are too depleted in S to crystallize iss. Instead, they will precipitate a copper sulphide with monovalent Cu and presumably solidify at an iss–bornite–millerite eutectic. The dataset is applied to massive sulphide ores of the Sudbury Igneous Complex fractionated with respect to Ni/Cu and (Ni + Cu)/Σmetal ratios. It is shown that the change-over in DNi may be used to retrieve parent melt compositions, fractionation temperatures, and magmatic fractionation paths of these deposits.
Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms via oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might hamper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated using Staphylococcus aureus and Pseudomonas aeruginosa as model organisms. Both were inactivated in vitro at a low light exposure of 0.72 J cm - 2 . Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log 10 steps of cell counts in low ion concentrations. Using the constant radiation exposure of 0.72 J cm -2 , the inactivation efficacy decreased somewhat at medium ion concentrations but reached almost zero for high ion concentrations. Depending on the application of PDI, the presence of carbonate and phosphate ions is unavoidable. Only upon light irradiation such ions may attack the PS molecule and reduce the efficacy of PDI. Our results indicate concentrations for carbonate and phosphate, in which PDI can still lead to efficient reduction of bacterial cells when using flavin based PS.
Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions. However, their performance degrades drastically under harsh ageing conditions. This study reveals...
New mineral and bulk-rock analyses, as well as Nd, Sr and Pb isotope compositions are presented for lavas from Grande Comore, Moheli and Mayotte, thru of the four main islands of the Comores Archipelago in the western Indian Ocean, and these data an used to evaluate the petrogenesis, evolution and mantle source region characteristics of Comorean lavas. The typically silica-undersaturated, alkaline lavas from all three islands can be grouped into two distinct types: La Grille-type (LGT) lavas, which display strong relative depletions in K, and Karthala-type (KT) lavas, which do not. With the exception of the lavas erupted by La Grille volcano on Grande Comore, which exhibit the petrographic and geochemical characteristics expected of primary mantle-derived magmas, all Comorean lavas analysed have experienced compositional modifications after they segregated from their source regions. Much of this variation can be explained quantitatively by fractional crystallization processes dominated by the fractionation ofolivine and clinopyroxene. Semi-quantitative modelling shows that the consistent and fundamental difference in composition between K-depleted LGT lavas and normal KT lavas can be attributed to partial melting processes, provided amphibole is a residual mantle phase after extraction of LGT magmas at low degrees of melting. Low absolute abundances of the heavy rare earth elements in LGT magmas are interpreted to reflect partial melting within the garnet stability field In contrast, KT magmas, which do not show relative K depletions, are considered to be the products of somewhat larger degrees of partial melting of an amphibolefree source at comparatively shallower depths. Whereas the Nd and Sr isotopic compositions of Comorean lavas (which show a significant range: 87Sr/86Sr = 0.70319–0.70393; 143Nd/Nd = 0.51263–0.51288) bear evidence for a time-averaged depletion in incompatible elements, the high incompatible element abundances of the lavas are interpreted to reflect the effects of a recent mantle enrichment event. At depths well within the garnet stability field this mantle enrichment is interpreted to have taken the form of modal metasomatism with the introduction of amphibole (giving rise to the source of LGT magmas), whereas cryptic metasomatism took place at shallower levels (giving rise to the source of KT lavas). The Nd, Sr and Pb isotope signature of the majority of Comorean lavas (both LGT and KT) is proposed to be the result of predominant4 contributions from a somewhat heterogeneous source4 4 4 presentative of the ambient sub-Comorean mantle, comprising a mixture between a HIMU component and a component on the depleted portion of the mantle array (possibly the source of Indian Ocean MORB), with only limited contributions from an EM I plume component. The lavas erupted by Karthala volcano (the youngest Comorean lavas), however, have significantly different isotopic compositions from all other Comorean lavas (lower 143Nd/144Nd and higher 87Sr/86Sr), suggesting increased contributions from the EM I component.
New U‐Pb zircon ages and geochemical data for felsic intrusive and extrusive rocks from the Richtersveld Igneous Complex (RIC) and related rocks in the westernmost part of the 1.03–1.06‐Ga Namaqua‐Natal metamorphic belt, South Africa, indicate that this complex is not related to post‐Namaqua orogenic collapse but is the product of mantle‐derived alkaline magmatism in an extensional stress field that led to the breakup of a Neoproterozoic supercontinent. The oldest age obtained for the crystallization of granitic to syenitic melts is $$833\pm 2$$ Ma. Continued thinning of the crust is reflected by the intrusion of bostonite dikes and a related extrusive phase dated at $$801\pm 8$$ Ma. Magmatism in this igneous province, which stretches for about 200 km along a southwest‐northeast linear trend, lasted at least until $$771\pm 6$$ Ma, which is now the best constraint on the beginning of rifting. Subsequent rift sediment deposition was accompanied by the emplacement of regionally extensive mafic dikes and bimodal, predominantly felsic volcanism along growth faults in the evolving rift basin at $$741\pm 6$$ Ma. Consistent lower intercept ages on concordia diagrams (mean: $$282\pm 28$$ Ma) suggest uplift and possible exposure to groundwater flow in response to late Paleozoic tectonism in the Cape Fold Belt farther south. The genesis of the RIC is in accordance with crustal thinning above a mantle plume that contributed to a mantle‐derived magma addition to the crust over a prolonged period of some 100 m.yr. Comparison with existing geochronological and petrological/geochemical data from elsewhere invites speculation as to the existence of a superplume stretching from southeastern Africa to South China in the heart of a supercontinent Palaeopangea.
Geochemical data are presented for primitive alkaline lavas from the Chyulu Hills Volcanic Province of southern Kenya, situated some 100 km east of the Kenya Rift Valley. In addition to their primitive compositions, a striking and ubiquitous feature is a strong but variable depletion in K relative to other highly incompatible elements when normalized to primitive mantle values. Semi-quantitative models are developed that best explain the petrogenesis of these lavas in terms of partial melting of a source that contained residual amphibole (but not phlogopite). The presence of amphibole implies a source in the subcontinental lithosphere rather than the asthenosphere. It is suggested that the amphibole is of metasomatic origin and was precipitated in the lithospheric mantle by infiltrating fluids and/or melts derived from rising mantle plume material. A raised geotherm as a consequence of the continued ascent of the plume material led to dehydration melting of the metasomatized mantle and generation of the Chyulu Hills lavas. It is proposed that the Chyulu Hills Volcanic Province represents an analogue for the earliest stages of continental rift initiation, during which interaction between a plume and initially refractory lithosphere may lead to the generation of lithospheric melts.
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