Real time investigation of solvent swelling induced β phase formation in poly(9-9-dioctyl fluorene)

The physical processes leading to solvent swelling induced glassy- to beta-phase transition in poly(9,9-dioctylfluorene) thin films are investigated in real time by photoluminescence and confocal spectroscopy. We show that the vapor solvent swelling induced beta-phase formation takes place in much shorter times (few minutes) than the one usually employed in literature (several hours). Moreover, we show that the swelling is faster if the solvent mainly interacts with the PF8 aromatic rings (toluene) than with the octyl chains (isooctane). On the contrary, no swelling is caused by nonsolvents such as n-butylic alcohol. Finally, we demonstrate that the beta-phase formation is due to athermal (simultaneous) nucleation followed by diffusion controlled one dimensional crystallization

Early application of ipsilateral cathodal-tDCS in a mouse model of brain ischemia results in functional improvement and perilesional microglia modulation

Early stroke therapeutic approaches rely on limited options, further characterized by a narrow therapeutic time window. In this context, the application of transcranial direct current stimulation (tDCS) in the acute phases after brain ischemia is emerging as a promising non-invasive tool. Despite the wide clinical application of tDCS, the cellular mechanisms underlying its positive effects are still poorly understood. Here, we explored the effects of cathodal tDCS (C-tDCS) 6 h after focal forelimb M1 ischemia in Cx3CR1GFP/+ mice. C-tDCS improved motor functionality of the affected forelimb, as assessed by the cylinder and foot-fault tests at 48 h, though not changing the ischemic volume. In parallel, histological analysis showed that motor recovery is associated with decreased microglial cell density in the area surrounding the ischemic core, while astrocytes were not affected. Deeper analysis of microglia morphology within the perilesional area revealed a shift toward a more ramified healthier state, with increased processes' complexity and a less phagocytic anti-inflammatory activity. Taken together, our findings suggest a positive role for early C-tDCS after ischemia, which is able to modulate microglia phenotype and morphology in parallel to motor recovery

Microscopic investigation of the poly(9,9-dioctylfluorene) photoluminescence dependence on the deposition conditions by confocal laser microscopy

We studied the microscopic dependence of poly(9,9-dioctylfluorene) photoluminescence (PL) on the deposition conditions. We show that in films spin coated from chloroform phase separation of β and glassy phases is present, with micrometric β phase clusters covering about 6% of the sample surface. The exposure to toluene vapors leads to the disappearance of the β phase clusters, but increases the β phase content in the films due to swelling induced polyfluorene chain planarization. The deposition from toluene solution leads to nonuniform PL intensity, dominated by the β phase emission, attributed to an interplay between aggregation during the solvent evaporation and solvent swelling induced chain planarization

White light emission from blends of blue-emitting organic molecules: A general route to the white organic light-emitting diode?

We show that all possible binary combinations of molecules from four different families of organics - a diamine derivative, N,N′-bis(3methylphenyl)-N,N′-diphenylbenzidine, an oxidiazole derivative, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, a substituted thiophene dioxide, 2,5-bis(trimethylsilyl thiophene)-1,1-dioxide, and poly(9-vinylcarbazole) - produce white or near-white emission. We suggest that this is due to exciplex formation, and that this is likely to be a general phenomenon for blends of blue-emitting aromatic organics. This implies that films of spin-coated blends of blue-emitting organics represent a general, simple, and cheap route to white-emitting organic light-emitting diodes

Environment-Induced Reversible Modulation of Optical and Electronic Properties of Lead Halide Perovskites and Possible Applications to Sensor Development: A Review

none4siLead halide perovskites are currently widely investigated as active materials in photonic and optoelectronic devices. While the lack of long term stability actually limits their application to commercial devices, several experiments demonstrated that beyond the irreversible variation of the material properties due to degradation, several possibilities exist to reversibly modulate the perovskite characteristics by acting on the environmental conditions. These results clear the way to possible applications of lead halide perovskites to resistive and optical sensors. In this review we will describe the current state of the art of the comprehension of the environmental effects on the optical and electronic properties of lead halide perovskites, and of the exploitation of these results for the development of perovskite-based sensors.openDe Giorgi, ML; Milanese, S; Klini, A; Anni, MDe Giorgi, Ml; Milanese, S; Klini, A; Anni,

Increased expression of autophagy-related genes in Alzheimer's Disease-Type 2 Diabetes Mellitus comorbidity models in cells

The association between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) has been extensively demonstrated, but despite this, the pathophysiological mechanisms underlying it are still unknown. In previous work, we discovered a central role for the autophagy pathway in the common alterations observed between AD and T2DM. In this study, we further investigate the role of genes belonging to this pathway, measuring their mRNA expression and protein levels in 3xTg-AD transgenic mice, an animal model of AD. Moreover, primary mouse cortical neurons derived from this model and the human H4Swe cell line were used as cellular models of insulin resistance in AD brains. Hippocampal mRNA expression showed significantly different levels for Atg16L1, Atg16L2, GabarapL1, GabarapL2, and Sqstm1 genes at different ages of 3xTg-AD mice. Significantly elevated expression of Atg16L1, Atg16L2, and GabarapL1 was also observed in H4Swe cell cultures, in the presence of insulin resistance. Gene expression analysis confirmed that Atg16L1 was significantly increased in cultures from transgenic mice when insulin resistance was induced. Taken together, these results emphasise the association of the autophagy pathway in AD-T2DM co-morbidity, providing new evidence about the pathophysiology of both diseases and their mutual interaction

Investigation of the Role of the Environment on the Photoluminescence and the Exciton Relaxation of CsPbBr3 Nanocrystals Thin Films

In this work, we present a detailed optical investigation of the effects of the environment on the photoluminescence (PL) spectra and the relaxation dynamics of pristine and aged CsPbBr 3 nanocrystal (NC) thin films. We demonstrate that, contrary to previous results on similar NCs, the PL intensity of pristine NCs is higher when the sample is in wet air than in vacuum, due to the passivation of defects reducing the free exciton trapping and the bound excitons non-radiative relaxation. The aged NCs show a PL intensity increase in wet air nine times stronger than the pristine ones, due to an interplay between static and dynamic effects, increasing the number of emitting NCs and reducing the non-radiative recombination rate of free excitons. These results improve the understanding of the possible interactions between perovskite NCs and the environment, which could be relevant for the development of optical gas sensors exploiting perovskite NCs

Picosecond photoluminescence decay time in colloidal nanocrystals : The role of intrinsic and surface states

Picosecond time-resolved photoluminescence measurements were performed on CdSe core and CdSe/ZnS core/shell colloidal quantum dots (QDs). Photoluminescence (PL) emission is observed to originate from intrinsic ±1U and ±1L bright states with lifetimes of 60 and 450 ps, respectively, and from a long living component with nanosecond lifetimes. The latter is attribuited to the emission from surface states (ss) approximately 16 and 13 meV below the ±1L state for core and core/shell QDs, respectively. We show that in the temperature range between 15 and 70 K the three recombination processes compete and they are thermally populated through different pathways (±1L → ±1U and ss → ±1L)

Photoluminescence efficiency of Substituted Quaterthiophene Crystals

none8The photoluminescence (PL) efficiency of substituted α-conjugated quaterthiophene crystals shows marked differences depending on crystal packing and molecular geometry. This effect is studied by evaluating the role of the intermolecular interactions and the effects of the single molecule conformation on the intersystem crossing (ISC) rate. The comparison of these calculations with absolute quantum efficiency measurements and with the experimental temperature dependence of the PL decay time, indicates that the differences in PL efficiency are not inherent to crystal packing effects but they are determined by the ISC rate.G.GIGLI; F.DELLA SALA; M.LOMASCOLO; M.ANNI; G.BARBARELLA; A.DI CARLO; P.LUGLI; R. CINGOLANIGigli, Giuseppe; F., DELLA SALA; M., Lomascolo; Anni, Marco; G., Barbarella; A., DI CARLO; P., Lugli; Cingolani, Robert

Bicolor Pixels from a Single Active Molecular Material by Surface-Tension-Driven Deposition†

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