BINA

Attempts to dope halide perovskites (HaPs) extrinsically have been mostly unsuccessful. Still, oxygen (O2) is an efficient p‐dopant for polycrystalline HaP films. To an extent, this doping is reversible, i.e., the films can be de‐doped by decreasing the O2 partial pressure. Here results are reported, aimed at understanding the mechanism of such reversible doping, as it has been argued that doping involves interaction of oxygen with defects inside bulk HaP. These experimental results clearly point out that O2‐surface interactions suffice to dope the bulk of the films. Such behavior fits what is known for other polycrystalline semiconductors, where surface charge transfer‐adducts can form and be removed. Thus, controlling the O2 partial pressure to which the HaP film is exposed, can, after proper encapsulation, achieve the desired bulk doping of the film.

Ion migration and subsequent accumulation at interfaces, driven by the built-in potential (Vbi), are intrinsic properties of halide perovskite solar cells (PVSCs), which mostly decrease device performance. To address this issue, we constructed favorable ion accumulation in perovskite solar cell by illumination to improve quasi-2D PVSCs performance. This design dramatically improves the photo-carrier collection and enables significant device performance improvement from 14.6% to 19.05%, one of the best results for quasi-2D PVSCs. We argue that the light-triggered favorable ion accumulation originates from 1) photo-induced quasi-fermi level splitting that compensates the Vbi, so as to avoid the ion accumulation that decreases Vbi, and 2) the light intensity distribution-induced uneven ion potential further drives the segregation of mobile ions towards favorable ion accumulation, decreasing any I- gradient between …

High‐Ni‐rich layered oxides [e.g., LiNixCoyMnzO2; x > 0.5, x + y + z = 1] are considered one of the most promising cathodes for high‐energy‐density lithium‐ion batteries (LIB). However, extreme electrode–electrolyte reactions, several interfacial issues, and structural instability restrict their practical applicability. Here, a shortened unconventional atomic surface reduction (ASR) technique is demonstrated on the cathode surface as a derivative of the conventional atomic layer deposition (ALD) process, which brings superior cell performances. The atomic surface reaction (reduction process) between diethyl‐zinc (as a single precursor) and Ni‐rich NMC cathode [LiNi0.8Co0.1Mn0.1O2; NCM811] material is carried out using the ALD reactor at different temperatures. The temperature dependency of the process through advanced spectroscopy and microscopy studies is demonstrated and it is shown that thin surface …

This chapter studies spontaneous scattering of light in single-mode fibers, due to the photoelastic perturbations associated with the oscillations of guided acoustic modes. The acoustic modes, in this case, are not stimulated by the optical fields being observed. Instead, they may be of thermal origin or driven by other optical field components than those monitored. Scattering is formulated in terms of nonlinear polarization terms and nonlinear wave equations for the evolution of the spectral sidebands of an input optical field. In the case of radial guided acoustic modes, photoelastic scattering of the optical field results in its phase modulation. By contrast, torsional-radial acoustic modes may induce phase modulation, coupling to the orthogonal polarization, or a combination of both, depending on the state of polarization of the input optical field. The strength of modulation is quantified in terms of a nonlinear coefficient …

A way of modulating the solid-state electron transport (ETp) properties of oligopeptide junctions is presented by charges and internal hydrogen bonding, which affect this process markedly. The ETp properties of a series of tyrosine (Tyr)-containing hexa-alanine peptides, self-assembled in monolayers and sandwiched between gold electrodes, are investigated in response to their protonation state. Inserting a Tyr residue into these peptides enhances the ETp carried via their junctions. Deprotonation of the Tyr-containing peptides causes a further increase of ETp efficiency that depends on this residue’s position. Combined results of molecular dynamics simulations and spectroscopic experiments suggest that the increased conductance upon deprotonation is mainly a result of enhanced coupling between the charged C-terminus carboxylate group and the adjacent Au electrode. Moreover, intra-peptide hydrogen …

Combinatorial material science crucially depends on robust, high-throughput characterization methods. While X-ray photoelectron spectroscopy (XPS) may provide detailed information about chemical and electronic properties, it is a time-consuming technique and, therefore, is not viewed as a high-throughput method. Here we present preliminary XPS data of 169 measurement spots on a combinatorial 72 × 72 cm² CuₓNi₁₋ₓOy compositional library to explore how characterization and evaluation routines can be optimized to improve throughput in XPS for combinatorial studies. In particular, two quantification approaches are compared. We find that a simple integration (of XPS peak regions) approach is suited for fast evaluation of, in the example system, the [Cu]/([Cu] + [Ni]) ratio. Complementary to that, the time-consuming (XPS peak-) fit approach provides additional insights into chemical speciation and oxidation state changes, without a large deviation of the [Cu]/([Cu] + [Ni]) ratio. This insight suggests exploiting the fast integration approach for ‘real time’ analysis during XPS data collection, paving the way for an ‘on-the-fly’ selection of points of interest (i.e., areas on the sample where sudden composition changes have been identified) for detailed XPS characterization. Together with the envisioned improvements when going from laboratory to synchrotron-based excitation sources, this will shorten the analysis time sufficiently for XPS to become a realistic characterization option for combinatorial material science.

Lignin derived bimetallic platinum group metal-free electrocatalysts for the oxygen reduction reaction in acid and alkaline media IRIS IRIS Home Sfoglia Macrotipologie & tipologie Dipartimento Autore Titolo Tipologia Settore Scientifico Disciplinare IT Italiano Italiano English English LOGIN 1.IRIS 2.Pubblicazioni 3.02 - Intervento a convegno Muhyuddin, M., Poli, F., Petri, E., Basile, F., Fasolini, A., Elbaz, L., et al. (2022). Lignin derived bimetallic platinum group metal-free electrocatalysts for the oxygen reduction reaction in acid and alkaline media. Intervento presentato a: 73rd Annual Meeting of the International Society of Electrochemistry - 23 - 28 October 2022 Xiamen, Fujian, China, Virtual, online. Lignin derived bimetallic platinum group metal-free electrocatalysts for the oxygen reduction reaction in acid and alkaline media M. Muhyuddin; C. Santoro 2022 Scheda breve Scheda completa Scheda completa (DC) SFX …

Forward stimulated Brillouin scattering in standard single‐mode fibers draws increasing interest toward sensing and signal processing applications. The process takes place through two classes of guided acoustic modes: purely radial ones and torsional‐radial modes with twofold azimuthal symmetry. The latter case cannot be described in terms of scalar models alone. In this work, the polarization attributes of forward stimulated Brillouin scattering in single‐mode fibers are investigated in analysis and experiment. Torsional‐radial acoustic modes are stimulated by orthogonally polarized pump tones, a first such report in standard single‐mode fibers. The scattering of optical probe waves by torsional‐radial modes may take up the form of phase modulation, cross‐polarization coupling, or a combination of both, depending on polarization. Lastly, this analysis predicts that circular and orthogonal pump tones may …

Aerogels are a very interesting group of materials owing to their unique physical and chemical properties. In the context of electrocatalysis, the focus has been on their physical properties, and they have been used primarily catalyst supports so far. In this work, we synthesized porphyrin aerogels containing Ni and NiFe mixed metal materials and studied them as catalysts for the oxygen evolution reaction (OER). Different Ni:Fe ratios were synthesized and studied in electrochemical cells, and DFT calculations were conducted in order to gain insight into their behavior. The activity trends were dependent on the metal ratios and differ from known NiFeOOH materials due to the change of the oxidation states of the metals to higher numbers. Herein, we show that Ni and Fe have a synergistic effect for OER, despite being structurally separated. They are connected electronically, though, through a large organic aromatic …

This chapter describes the experimental setups and measurement protocols used in the characterization of forward Brillouin scattering processes in optical fibers. The methods can be broadly classified in three categories: techniques in which forward Brillouin scattering is accumulated and integrated over the entire length of a fiber under test, point measurements at specific locations, and spatially distributed analysis of the scattering spectra as functions of position. Specific examples include the spontaneous scattering of probe waves within fiber interferometer loops, polarization rotation of probe waves, photoelastic perturbations of fiber Bragg gratings, coupling of power between forward Brillouin pump tones, and spatially distributed mapping of auxiliary backscattering processes such as Rayleigh or backward Brillouin. Lastly, the spatially distributed analysis of inter-modal scattering over polarization-maintaining …

The papers in this volume were part of the technical conference cited on the cover and title page. Papers were selected and subject to review by the editors and conference program committee. Some conference presentations may not be available for publication. Additional papers and presentation recordings may be available online in the SPIE Digital Library at SPIEDigitalLibrary. org.

Adding a 2D character to halide perovskite (HaP) active layers in ambient‐protected cells can improve their stability drastically, which is not obvious from the hydrophobicity of the large cations that force the HaP into a 2D structure. Results of two‐photon confocal microscopy are reported to study inherent photo‐stability of 2D Pb iodide HaPs in the interior of single crystals. Compared to 3D HaP crystals, 2D ones have higher photo‐stability and, under a few sun‐equivalent conditions, self‐heal efficiently after photo‐damage. Using both photoluminescence (PL) intensities (as function of time after photo‐damage) and spectra, self‐healing dynamics of 2D HaP (C4H9NH3)2PbI4, 2D/3D (C4H9NH3)2(CH3NH3)2Pb3I10 and 3D MAPbI3 are compared. Differences in response to photo‐damage and self‐healing ability from different degrees of photo‐damage are found between these HaPs. Based on the findings, a …

Electron paramagnetic resonance (EPR) spectroscopy has emerged as an ideal biophysical tool to study complex biological processes. EPR spectroscopy can follow minor conformational changes in various proteins as a function of ligand or protein binding or interactions with high resolution and sensitivity. Resolving cellular mechanisms, involving small ligand binding or metal ion transfer, is not trivial and cannot be studied using conventional biophysical tools. In recent years, our group has been using EPR spectroscopy to study the mechanism underlying copper ion transfer in eukaryotic and prokaryotic systems. This mini-review focuses on our achievements following copper metal coordination in the diamagnetic oxidation state, Cu(I), between biomolecules. We discuss the conformational changes induced in proteins upon Cu(I) binding, as well as the conformational changes induced in two proteins involved in Cu(I) transfer. We also consider how EPR spectroscopy, together with other biophysical and computational tools, can identify the Cu(I)-binding sites. This work describes the advantages of EPR spectroscopy for studying biological processes that involve small ligand binding and transfer between intracellular proteins.

Epithelial-mesenchymal Transition (EMT) is a multi-step process that involves cytoskeletal rearrangement. Here, using a novel image quantification tool, Statistical Parametrization of Cell Cytoskeleton (SPOCC), we have identified an intermediate EMT state with a specific cytoskeletal signature. We have been able to partition EMT into two steps:(1) initial formation of transverse arcs and dorsal stress fibers and (2) their subsequent conversion to ventral stress fibers with a concurrent alignment of fibers. Using the Orientational Order Parameter (OOP) as a figure of merit, we have been able to track EMT progression in live cells as well as characterize and quantify their cytoskeletal response to drugs. SPOCC has improved throughput and is non-destructive, making it a viable candidate for studying a broad range of biological processes. Further, owing to the increased stiffness (and by inference invasiveness) of the intermediate EMT phenotype compared to mesenchymal cells, our work can be instrumental in aiding the search for new treatment strategies that combat metastasis by specifically targeting the fiber alignment process.

Photon-HDF5 is an open-source and open file format for storing photon-counting data from single molecule microscopy experiments, introduced to simplify data exchange and increase the reproducibility of data analysis. Part of the Photon-HDF5 ecosystem, is phconvert, an extensible python library that allows converting proprietary formats into Photon-HDF5 files. However, its use requires some proficiency with command line instructions, the python programming language, and the YAML markup format. This creates a significant barrier for potential users without that expertise, but who want to benefit from the advantages of releasing their files in an open format. In this work, we present a GUI that lowers this barrier, thus simplifying the use of Photon-HDF5. This tool uses the phconvert python library to convert data files originally saved in proprietary data formats to Photon-HDF5 files, without users having to write a …

Many organisms have an elastic skeleton that consists of a closed shell of epithelial cells that is filled with fluid, and can actively regulate both elastic forces in the shell and hydrostatic pressure inside it. In this work we introduce a simple network model of such pressure-stabilized active elastic shells in which cross-links are represented by material points connected by non-linear springs of some given equilibrium lengths and spring constants. We mimic active contractile forces in the system by changing the parameters of randomly chosen springs and use computer simulations to study the resulting local and global deformation dynamics of the network. We elucidate the statistical properties of these deformations by computing the corresponding distributions and correlation functions. We show that pressure-induced stretching of the network introduces coupling between its local and global behavior: while the network …

In a wide spectrum of neurodegenerative diseases, self-assembly of pathogenic proteins to cytotoxic intermediates is accelerated by the presence of metal ions such as Cu2+. Only low concentrations of these early transient oligomeric inter-mediates are present in a mixture of species during fibril formation, and hence information on the extent of structuring of these oligomers is still largely unknown. Here, we investigate dimers as the first intermediates in the Cu2+-driven aggrega-tion of a cyclic D,L-α-peptide architecture. The unique structural and functional properties of this model system recapitu-late the self-assembling properties of amyloidogenic proteins including β-sheet conformation and cross-interaction with pathogenic amyloids. We show that a histidine-rich cyclic D,L-α-octapeptide binds Cu2+ with high affinity and selectivity to generate amyloid-like cross-β-sheet structures. By taking advantage of …

Practical implementation of anion exchange membrane fuel cells mainly relies on the choice of highly active and stable oxygen reduction reaction (ORR) catalysts. Transition metal oxides based on Group 4 and 5 are well known for their chemical stability and corrosion‐resistance and they are earth‐abundant too. Among them, zirconia (ZrO2) has exceptional chemical stability, but its poor conductivity and less active sites hinder the application of zirconia‐based materials toward ORR. In order to bring out the best activity from ZrO2, careful site engineering without losing the phase purity and chemical stability is essential. In this context, nitrogen doping on tetragonal zirconia (t‐ZrO2) as a viable method to obtain a highly active ORR catalyst is adopted. The temperature for the phase pure synthesis of t‐ZrO2 is optimized by crystallographic study. The nitrogen doping in the zirconia lattice is confirmed by various …

The parasite Trypanosoma brucei causes African sleeping sickness that is fatal to patients if untreated. Parasite differentiation from a replicative slender form into a quiescent stumpy form promotes host survival and parasite transmission. Long noncoding RNAs (lncRNAs) are known to regulate cell differentiation in other eukaryotes. To determine whether lncRNAs are also involved in parasite differentiation, we used RNA sequencing to survey the T. brucei genome, identifying 1428 previously uncharacterized lncRNA genes. We find that grumpy lncRNA is a key regulator that promotes parasite differentiation into the quiescent stumpy form. This function is promoted by a small nucleolar RNA encoded within the grumpy lncRNA. snoGRUMPY binds to messenger RNAs of at least two stumpy regulatory genes, promoting their expression. grumpy overexpression reduces parasitemia in infected mice. Our analyses suggest that T. brucei lncRNAs modulate parasite-host interactions and provide a mechanism by which grumpy regulates cell differentiation in trypanosomes.