Exciton dissociation in 2D layered metal-halide perovskites

: Layered 2D perovskites are making inroads as materials for photovoltaics and light emitting diodes, but their photophysics is still lively debated. Although their large exciton binding energies should hinder charge separation, significant evidence has been uncovered for an abundance of free carriers among optical excitations. Several explanations have been proposed, like exciton dissociation at grain boundaries or polaron formation, without clarifying yet if excitons form and then dissociate, or if the formation is prevented by competing relaxation processes. Here we address exciton stability in layered Ruddlesden-Popper PEA2PbI4 (PEA stands for phenethylammonium) both in form of thin film and single crystal, by resonant injection of cold excitons, whose dissociation is then probed with femtosecond differential transmission. We show the intrinsic nature of exciton dissociation in 2D layered perovskites, demonstrating that both 2D and 3D perovskites are free carrier semiconductors and their photophysics is described by a unique and universal framework

Targeting CD34(+) cells of the inflamed synovial endothelium by guided nanoparticles for the treatment of rheumatoid arthritis

Despite the advances in the treatment of rheumatoid arthritis (RA) achieved in the last few years, several patients are diagnosed late, do not respond to or have to stop therapy because of inefficacy and/or toxicity, leaving still a huge unmet need. Tissue-specific strategies have the potential to address some of these issues. The aim of the study is the development of a safe nanotechnology approach for tissue-specific delivery of drugs and diagnostic probes. CD34 + endothelial precursors were addressed in inflamed synovium using targeted biodegradable nanoparticles (tBNPs). These nanostructures were made of poly-lactic acid, poly-caprolactone, and PEG and then coated with a synovial homing peptide. Immunofluorescence analysis clearly demonstrated their capacity to selectively address CD34 + endothelial cells in synovial tissue obtained from human, mouse, and rat. Biodistribution studies in two different animal models of rheumatoid arthritis (antigen-induced arthritis/AIA and collagen-induced arthritis/CIA) confirmed the selective accumulation in inflamed joints but also evidenced the capacity of tBNP to detect early phases of the disease and the preferential liver elimination. The therapeutic effect of methotrexate (MTX)-loaded tBNPs were studied in comparison with conventional MTX doses. MTX-loaded tBNPs prevented and treated CIA and AIA at a lower dose and reduced administration frequency than MTX. Moreover, MTX-loaded tBNP showed a novel mechanism of action, in which the particles target and kill CD34 + endothelial progenitors, preventing neo-angiogenesis and, consequently, synovial inflammation. tBNPs represent a stable and safe platform to develop highly-sensitive imaging and therapeutic approaches in RA targeting specifically synovial neo-angiogenesis to reduce local inflammation

Genetic loci linked to Type 1 Diabetes and Multiple Sclerosis families in Sardinia

<p>Abstract</p> <p>Background</p> <p>The Mediterranean island of Sardinia has a strikingly high incidence of the autoimmune disorders Type 1 Diabetes (T1D) and Multiple Sclerosis (MS). Furthermore, the two diseases tend to be co-inherited in the same individuals and in the same families. These observations suggest that some unknown autoimmunity variant with relevant effect size could be fairly common in this founder population and could be detected using linkage analysis.</p> <p>Methods</p> <p>To search for T1D and MS loci as well as any that predispose to both diseases, we performed a whole genome linkage scan, sequentially genotyping 593 microsatellite marker loci in 954 individuals distributed in 175 Sardinian families. In total, 413 patients were studied; 285 with T1D, 116 with MS and 12 with both disorders. Model-free linkage analysis was performed on the genotyped samples using the Kong and Cox logarithm of odds (LOD) score statistic.</p> <p>Results</p> <p>In T1D, aside from the HLA locus, we found four regions showing a lod-score ≥1; 1p31.1, 6q26, 10q21.2 and 22q11.22. In MS we found three regions showing a lod-score ≥1; 1q42.2, 18p11.21 and 20p12.3. In the combined T1D-MS scan for shared autoimmunity loci, four regions showed a LOD >1, including 6q26, 10q21.2, 20p12.3 and 22q11.22. When we typed more markers in these intervals we obtained suggestive evidence of linkage in the T1D scan at 10q21.2 (LOD = 2.1), in the MS scan at 1q42.2 (LOD = 2.5) and at 18p11.22 (LOD = 2.6). When all T1D and MS families were analysed jointly we obtained suggestive evidence in two regions: at 10q21.1 (LOD score = 2.3) and at 20p12.3 (LOD score = 2.5).</p> <p>Conclusion</p> <p>This suggestive evidence of linkage with T1D, MS and both diseases indicates critical chromosome intervals to be followed up in downstream association studies.</p

La regione storica del Sarcidano (Sardegna centro-meridionale) e la Valle del Duero (España) durante l’età del bronzo: Cenni di confronto e parallelismi

This research talks about a comparison between the region of Sarcidano (Sardinia) and Duero Valley (Valle del Duero-Spain). The work’s aim is to develop a framework about the settlement modalities during the Bronze Age. The presence of nuraghi is the main diff erence observed between the Duero Valley and Sardinia. These basalt structures characterize the protohistoric sardinian landscape and culture and are located around the highlands in the Flumendosa river. This paper point out the relationship between nuraghi and nuragic structures in the space around. The Bronze Age is carachterized by radical social and economic developments, that lead to new forms of social complexity. To understand all those dynamics is necessary to do a research about the diff erent types of settlement in Sarcidano and the Duero Valley.La ricerca riguarda un raff ronto tra la regione sarda del Sarcidano e la Valle spagnola del Duero con l`obiettivo di elaborare un quadro delle realtà insediative attive nell’Età del Bronzo. La presenza, in ambito sardo, dei nuraghi è la fondamentale diff erenza che si osserva tra Valle del Duero e la Sardegna. Tali strutture, peculiari del paesaggio e della cultura protostorica sardi, sono numerosi anche negli altopiani basaltici che circondano il Flumendosa. Con il presente lavoro si è cercato di mettere in evidenza la relazione tra i nuraghi e le strutture di varia natura, dislocati nel territorio. L’età del Bronzo è, infatti, caratterizzata da radicali sviluppi di carattere socio-economico dai quali scaturisce una società articolata e in espansione, nell’ambito della quale divengono sempre più manifeste le distinzioni di status. Per meglio comprendere tali meccanismi, si è reputato indispensabile eff ettuare un’indagine sulla distinzione delle tipologie di insediamento nel Sarcidano in relazione alla Valle del Duero

Exciton dissociation in 2D layered metal-halide perovskites

Layered 2D perovskites are making inroads as materials for photovoltaics and light emitting diodes, but their photophysics is still lively debated. Although their large exciton binding energies should hinder charge separation, significant evidence has been uncovered for an abundance of free carriers among optical excitations. Several explanations have been proposed, like exciton dissociation at grain boundaries or polaron formation, without clarifying yet if excitons form and then dissociate, or if the formation is prevented by competing relaxation processes. Here we address exciton stability in layered Ruddlesden-Popper PEA2PbI4 (PEA stands for phenethylammonium) both in form of thin film and single crystal, by resonant injection of cold excitons, whose dissociation is then probed with femtosecond differential transmission. We show the intrinsic nature of exciton dissociation in 2D layered perovskites, demonstrating that both 2D and 3D perovskites are free carrier semiconductors and their photophysics is described by a unique and universal framework.</p

Comparison of the effect of valsartan and lisinopril on autonomic nervous system activity in chronic heart failure.

BACKGROUND: In chronic heart failure (CHF), the derangement of autonomic nervous system activity has a deep impact on the progression of the disease. It has been demonstrated that modulation of the renin-angiotensin aldosterone system (RAAS) increases autonomic control of heart rate and reduces adrenergic activity. We sought to evaluate, in CHF, the different effects of an ACE inhibitor (lisinopril) and of an AT1 receptor antagonist (valsartan) on heart rate variability, baroreflex sensitivity and norepinephrine plasma levels. METHODS: Ninety patients (61 +/- 10 years, 2.3 +/- 0.5, New York Heart Association class) with CHF and left ventricular ejection fraction <40\% were randomly assigned in a double-blind fashion to receive lisinopril (uptitrated to 20 mg/d) or valsartan (uptitrated to 160 mg/d) therapy for 16 weeks. Heart rate variability (evaluated by measuring standard deviation of normal R-R intervals on 24-hour ECG recordings), spontaneous baroreflex sensitivity and aldosterone and norepinephrine plasma levels were assessed before and after drug therapy. RESULTS: There were no significant differences between valsartan and lisinopril in their effects on left ventricular function, arterial pressure, aldosterone plasma levels and autonomic control of heart rate. Both lisinopril and valsartan significantly reduced plasma norepinephrine levels, but the reduction induced by valsartan was significantly greater than that observed for lisinopril (27\% vs 6\%, P <.05). CONCLUSIONS: This study shows a comparable effect of ACE inhibition (lisinopril) and of AT1 receptor antagonism (valsartan) on cardiac vagal control of heart rate, whereas valsartan has shown a more effective modulation of sympathetic activity measured by plasma norepinephrine levels

Pressure response of decylammonium-containing 2D iodide perovskites

Manipulation by external pressure of the optical response of 2D Metal Halide Perovskites (MHPs) is a fascinating route to tune their properties and promote the emergence of novel features. We investigate here DA(2)PbI(4) and DA(2)GeI(4) (DA = decylammonium) perovskites in the pressure range up to similar to 12 GPa by X-ray powder diffraction, absorption, and photoluminescence spectroscopy. Although the two systems share a similar structural evolution with pressure, the optical properties are rather different and influenced by Pb or Ge. DA(2)PbI(4) shows a progressive red shift from 2.28 eV (P = 0 GPa) to 1.64 eV at 11.5 GPa, with a narrow PL emission, whereas DA(2)GeI(4), changes from a non-PL system at ambient pressure to a clear broadband emitter centered around 730 nmwith an intensity maximum at about 3.7GPa. These results unveil the role of the central atom on the nature of emission under pressure in 2D MHPs containing a long alkyl chain

Reaction Mechanism of Hydrogen Generation and Nitrogen Fixation at Carbon Nitride/Double Perovskite Heterojunctions

Photocatalytically active heterojunctions based on metal halide perovskites (MHPs) are drawing significant interest for their chameleon ability to foster several redox reactions. The lack of mechanistic insights into their performance, however, limits the ability of engineering novel and optimized materials. Herein, we report on a composite system including a double perovskite, Cs2AgBiCl6/g-C3N4, used in parallel for solar-driven hydrogen generation and nitrogen reduction. The composite efficiently promotes the two reactions, but its activity strongly depends on the perovskite/carbon nitride relative amounts. Through advanced spectroscopic investigation and density function theory modelling we studied the H2 and NH3 production reaction mechanisms, finding perovskite halide vacancies as the primary reactive sites for hydrogen generation, withstanding a positive contribution of low loaded g-C3N4, in reducing carrier recombination. For nitrogen reduction, instead, the active sites are g-C3N4 nitrogen vacancies, and the heterojunction best performs at low perovskites loadings, as the composites maximizes light absorption and reduced carrier losses. We believe these insights are important add-ons towards universal exploitation of MHPs in contemporary photocatalysis

White light emission with unity efficiency from Cs2Na1−xAgxIn1−yBiyCl6 double perovskites: the role of bismuth and silver

Double perovskites Cs2Na1−xAgxIn1−yBiyCl6 can emit warm white light with almost unity quantum efficiency and are thus among the most promising materials for solid-state lighting. The emission spectrum is reproducible and the materials themselves are robust against degradation, as well as fabricated from earth-abundant, non-toxic precursors. The emission efficiency is however sensitive to the materials composition, with small variations modifying the photoluminescence quantum yield by more than an order of magnitude. We provide here a comprehensive, systematic study of the optical properties as a function of composition and identify the microscopic mechanism linking the presence of Bi and Ag to the high emission quantum yield. A 0.1% minimum fraction of Bi and Ag is found to trigger efficient emission of warm white light. Ag alloying is fundamental to obtain high emission yields. Continuous-wave spectroscopy measurements are complemented with ab initio computation of the electronic band structure in demonstrating that Bi strengthens optical absorption at the band gap edge of the double perovskites. In addition, it is found by combining time-resolved photoluminescence and transient absorption spectroscopy that Ag and Bi promote the formation of bright (radiative) self-trapped excitons, while inhibiting exciton relaxation into long-lived dark states