Search

Cu2O has been deposited on m-, r-, and a-Al2O3 by reactive sputtering of Cu using Ar with different contents of O2 followed by annealing under carefully optimized conditions at 500 °C under Ar:H2 in order to prevent the oxidation and reduction of the Cu2O layers, which have a cubic crystal structure and are bulk-relaxed. We find that the content of O2 influences the structural and optical properties of the Cu2O layers that exhibited a detailed spectral structure and distinct peaks at 2.75, 2.54, and 2.17 eV corresponding to the indigo, blue, and yellow direct gap transitions of Cu2O as observed by ultrafast pump–probe spectroscopy at room temperature. However, we also observed a transition at 1.8 eV that is related to the occurrence of states ∼0.4 eV below the conduction band minimum of Cu2O. We discuss the controversial origin of these states, which are usually attributed to donor-like oxygen vacancy states, and suggest that the origin of these states may be related to traps at the interfaces of CuO/Cu2O nanostructures, which is important in the context of energy conversion pertaining to solar cells and photocatalysis.

Glucocorticoids prescribed to limit inflammation, have significant adverse effects. Here the authors show that co-administration of AZD4017 with prednisolone in men is a potential strategy to limit adverse glucocorticoid effects.

Strong coupling of a confined optical field to the excitonic or vibronic transitions of a molecular material results in the formation of new hybrid states called polaritons. Such effects have been extensively studied in Fabry–Pèrot microcavity structures where an organic material is placed between two highly reflective mirrors. Recently, theoretical and experimental evidence has suggested that strong coupling can be used to modify chemical reactivity as well as molecular photophysical functionalities. However, the geometry of conventional microcavity structures limits the ability of molecules "encapsulated" in a cavity to interact with their local environment. Here, we fabricate mirrorless organic membranes that utilize the refractive index contrast between the organic active material and its surrounding medium to confine an optical field with Q-factor values up to 33. Using angle-resolved white light reflectivity measurements, we confirm that our structures operate in the strong coupling regime, with Rabi-splitting energies between 60 and 80 meV in the different structures studied. The experimental results are matched by transfer matrix and coupled oscillator models that simulate the various polariton states of the free standing membranes. Our work demonstrates that mechanically flexible and easy-to-fabricate free standing membranes can support strong light–matter coupling, making such simple and versatile structures highly promising for a range of polariton applications. [ABSTRACT FROM AUTHOR]

Cu3N with a cubic crystal structure is obtained in this paper by the sputtering of Cu under N2 followed by annealing under NH3: H2 at 400 °C, after which it was doped with iodine at room temperature resulting into p-type Cu3N with hole densities between 1016 and 1017 cm−3. The Cu3N exhibited distinct maxima in differential transmission at ~2.01 eV and 1.87 eV as shown by ultrafast pump-probe spectroscopy, corresponding to the M and R direct energy band gaps in excellent agreement with density functional theory calculations, suggesting that the band gap is clean and free of mid-gap states. The Cu3N was gradually converted into optically transparent γ-CuI that had a hole density of 4 × 1017 cm−3, mobility of 12 cm2/Vs and room temperature photoluminescence at 3.1 eV corresponding to its direct energy band gap. We describe the fabrication and properties of γ-CuI/TiO2/Cu3N and γ-CuI/Cu3N p-n heterojunctions that exhibited rectifying current-voltage characteristics, but no photogenerated current attributed to indirect recombination via shallow states in Cu3N and/or deep states in the γ-CuI consistent with the short (ps) lifetimes of the photoexcited electrons-holes determined from transient absorption–transmission spectroscopy.

Abstract A bulk scale process is implemented for the production of nanostructured film composites comprising unary or multi-component metal oxide nanoparticles dispersed in a suitable polymer matrix. The as-received nanoparticles, namely Al $$_2$$ 2 O $$_3$$ 3 , SiO $$_2$$ 2 and TiO $$_2$$ 2 and binary combinations, are treated following specific chemical and mechanical processes in order to be suspended at the optimal size and composition. Subsequently, a polymer extrusion technique is employed for the fabrication of each film, while the molten polymer is mixed with the treated metal oxide nanoparticles. Transmission and reflection measurements are performed in order to map the optical properties of the fabricated, nanostructured films in the UV, VIS and IR. The results substantiate the capability of the overall methodology to regulate the optical properties of the films depending on the type of nanoparticle formation which can be adjusted both in size and composition.

Strong coupling between light and matter in a microcavity can produce quasi‐particle states termed cavity‐polaritons. In cavity architectures containing more than one excitonic species, the photon mode can simultaneously couple to the different excitons, generating new ʻhybrid‐polaritonʼ states. It is demonstrated that such hybrid polariton states can energetically connect different molecular species, even when their intermolecular distance is much larger than the Förster transfer radius. Here, this mechanism is unveiled and observed in the time domain energy delocalization in a strongly coupled cavity containing two layers of donor and acceptor molecules, separated by an inert spacer layer of 2 µm thickness. 2D electronic spectroscopy is used, a technique that provides simultaneously high spectral and temporal resolution, to probe the dynamics of the energy flow processes following ultra‐fast excitation. It shows that energy is almost instantaneously delocalized among the polariton states, providing a direct connection between very highly separated donor and acceptor molecules. The results are of potential significance for light‐harvesting devices, optoelectronics, and bio‐photonic systems. [ABSTRACT FROM AUTHOR]

Background and aims: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver condition. It is tightly associated with an adverse metabolic phenotype (including obesity and type 2 diabetes) as well as with obstructive sleep apnoea (OSA) of which intermittent hypoxia is a critical component. Hepatic de novo lipogenesis (DNL) is a significant contributor to hepatic lipid content and the pathogenesis of NAFLD and has been proposed as a key pathway to target in the development of pharmacotherapies to treat NAFLD. Our aim is to use experimental models to investigate the impact of hypoxia on hepatic lipid metabolism independent of obesity and metabolic disease. Methods: Human and rodent studies incorporating stable isotopes and hyperinsulinaemic euglycaemic clamp studies were performed to assess the regulation of DNL and broader metabolic phenotype by intermittent hypoxia. Cell-based studies, including pharmacological and genetic manipulation of hypoxia-inducible factors (HIF), were used to examine the underlying mechanisms. Results: Hepatic DNL increased in response to acute intermittent hypoxia in humans, without alteration in glucose production or disposal. These observations were endorsed in a prolonged model of intermittent hypoxia in rodents using stable isotopic assessment of lipid metabolism. Changes in DNL were paralleled by increases in hepatic gene expression of acetyl CoA carboxylase 1 and fatty acid synthase. In human hepatoma cell lines, hypoxia increased both DNL and fatty acid uptake through HIF-1α and -2α dependent mechanisms. Conclusions: These studies provide robust evidence linking intermittent hypoxia and the regulation of DNL in both acute and sustained in vivo models of intermittent hypoxia, providing an important mechanistic link between hypoxia and NAFLD.

Retrograde BMP signaling and canonical pMad/Medea-mediated transcription regulate diverse target genes across subsets of Drosophila efferent neurons, to differentiate neuropeptidergic neurons and promote motor neuron terminal maturation. How a common BMP signal regulates diverse target genes across many neuronal subsets remains largely unresolved, although available evidence implicates subset-specific transcription factor codes rather than differences in BMP signaling. Here we examine the cis-regulatory mechanisms restricting BMP-induced FMRFa neuropeptide expression to Tv4-neurons. We find that pMad/Medea bind at an atypical, low affinity motif in the FMRFa enhancer. Converting this motif to high affinity caused ectopic enhancer activity and eliminated Tv4-neuron expression. In silico searches identified additional motif instances functional in other efferent neurons, implicating broader functions for this motif in BMP-dependent enhancer activity. Thus, differential interpretation of a common BMP signal, conferred by low affinity pMad/Medea binding motifs, can contribute to the specification of BMP target genes in efferent neuron subsets.

Background and Purpose: 11β‐Hydroxysteroid dehydrogenase‐1 (11β‐HSD1) catalyses the oxoreduction of cortisone to cortisol, amplifying levels of active glucocorticoids. It is a pharmaceutical target in metabolic disease and cognitive impairments. 11β‐HSD1 also converts some 7oxo‐steroids to their 7β‐hydroxy forms. A recent study in mice described the ratio of tauroursodeoxycholic acid (TUDCA)/tauro‐7oxolithocholic acid (T7oxoLCA) as a biomarker for decreased 11β‐HSD1 activity. The present study evaluates the equivalent bile acid ratio of glycoursodeoxycholic acid (GUDCA)/glyco‐7oxolithocholic acid (G7oxoLCA) as a biomarker for pharmacological 11β‐HSD1 inhibition in humans and compares it with the currently applied urinary (5α‐tetrahydrocortisol + tetrahydrocortisol)/tetrahydrocortisone ((5αTHF + THF)/THE) ratio. Experimental Approach: Bile acid profiles were analysed by ultra‐HPLC tandem‐MS in blood samples from two independent, double‐blind placebo‐controlled clinical studies of the orally administered selective 11β‐HSD1 inhibitor AZD4017. The blood GUDCA/G7oxoLCA ratio was compared with the urinary tetrahydro‐glucocorticoid ratio for ability to detect 11β‐HSD1 inhibition. Key Results: No significant alterations were observed in bile acid profiles following 11β‐HSD1 inhibition by AZD4017, except for an increase of the secondary bile acid G7oxoLCA. The enzyme product/substrate ratio GUDCA/G7oxoLCA was found to be more reliable to detect 11β‐HSD1 inhibition than the absolute G7oxoLCA concentration in both cohorts. Comparison of the blood GUDCA/G7oxoLCA ratio with the urinary (5αTHF + THF)/THE ratio revealed that both successfully detect 11β‐HSD1 inhibition. Conclusions and Implications: 11β‐HSD1 inhibition does not cause major alterations in bile acid homeostasis. The GUDCA/G7oxoLCA ratio represents the first blood biomarker of pharmacological 11β‐HSD1 inhibition and may replace or complement the urinary (5αTHF + THF)/THE ratio biomarker. [ABSTRACT FROM AUTHOR]

Ligand exchange performed during or after the colloidal synthesis of nanocrystals (NCs) provides an efficient way to produce conductive NC solids for optoelectronics. Herein, a post‐synthetic ligand washing process is developed and applied to two different combinations of ligands and perovskite NCs, namely robust green CsPbBr3 NCs capped by didodecyldimethylammonium bromide and near‐infrared FAPbI3 NCs decorated by weakly bound oleic acid ligands. The impact of such processes on the morphological and optoelectronic NC properties is examined while exploring parameters such as the reaction time and the influence of oxygen and humidity. For the FAPbI3 NCs, ligand washing results in extended NC aggregation and substantial photoluminescence loss, with the treatment becoming more aggressive for air‐exposed films. For the CsPbBr3 NCs, the process is insensitive to the environmental conditions and results in partial ligand shell loss and NC close packing rather than bulk‐like aggregation while affecting less the optical properties. Upon ligand removal, the photoconductance increases by up to ≈90% and ≈60% for FAPbI3 NCs and CsPbBr3 NCs, respectively. THz spectroscopy produces qualitatively similar trends of the conductivity with ligand removal time, with THz mobility values as high as 30 and 6 V−1s−1cm2 for glove box prepared FAPbI3 and CsPbBr3 NCs, respectively. [ABSTRACT FROM AUTHOR]

Cu2O has been deposited on m-, r-, and a-Al2O3 by reactive sputtering of Cu using Ar with different contents of O2 followed by annealing under carefully optimized conditions at 500 °C under Ar:H2 in order to prevent the oxidation and reduction of the Cu2O layers, which have a cubic crystal structure and are bulk-relaxed. We find that the content of O2 influences the structural and optical properties of the Cu2O layers that exhibited a detailed spectral structure and distinct peaks at 2.75, 2.54, and 2.17 eV corresponding to the indigo, blue, and yellow direct gap transitions of Cu2O as observed by ultrafast pump–probe spectroscopy at room temperature. However, we also observed a transition at 1.8 eV that is related to the occurrence of states ∼0.4 eV below the conduction band minimum of Cu2O. We discuss the controversial origin of these states, which are usually attributed to donor-like oxygen vacancy states, and suggest that the origin of these states may be related to traps at the interfaces of CuO/Cu2O nanostructures, which is important in the context of energy conversion pertaining to solar cells and photocatalysis. [ABSTRACT FROM AUTHOR]

Ultrafast carrier dynamics in copper nitride (Cu3N) have been investigated using femtosecond pump-probe spectroscopy. Cu3N films were prepared on fused SiO2 substrates coated with thin Cu layers under NH3:O2 flow. The obtained differential transmission data revealed discrete maxima in the spectra at different probing energies. Lower energy maxima are attributed to direct bandgap transitions, while transient transmission peaks at higher energies are due to probing defect state transitions in the material. These states originate from crystalline structure defects and are energetically located close to the conduction and valence bands. The recombination times extracted from the data were of the order of few picoseconds which raises the question of how suitable this material is for energy conversion applications. Ultrafast pump-probe spectra obtained at a low temperature of 78 K revealed almost no shifting of the transition energies compared to room temperature spectra, although small differences in decay times were observed due to the absence of thermal effects. Measurements using longer probing wavelengths in the infrared region indicated state filling of defect states within the bandgap for wavelengths between 800 nm and 1400 nm while probing at longer wavelengths (1400–1600 nm) revealed initial free-carrier absorption and re-excitation of carriers to higher energy defect states above the conduction band. In addition, copper oxynitride layers were produced and studied in a similar fashion to investigate the effects of oxygen on the band structure and recombination times. [ABSTRACT FROM AUTHOR]

We investigate the employment of carefully selected solvent additives in the processing of a commercial perovskite precursor ink and analyze their impact on the performance of organometal trihalide perovskite (CH3NH3PbI3−xClx) photovoltaic devices. We provide evidence that the use of benzaldehyde can be used as an effective method to preserve the stoichiometry of the perovskite precursors in solution. Benzaldehyde based additive engineering shows to improve perovskite solid state film morphology and device performance of CH3NH3PbI3−xClx based solar cells.