PbI Passivation of Three Dimensional PbS Quantum Dot Superlattices Toward Optoelectronic Metamaterials.

Lead chalcogenide colloidal quantum dots are one of the most promising materials to revolutionize the field of short-wavelength infrared optoelectronics due to their bandgap tunability and strong absorption. By self-assembling these quantum dots into ordered superlattices, mobilities approaching those of the bulk counterparts can be achieved while still retaining their original optical properties. The recent literature focused mostly on PbSe-based superlattices, but PbS quantum dots have several advantages, including higher stability.

On the Electrochemical Growth of a Crystalline p-n Junction From Aqueous Solutions.

Our society largely relies on inorganic semiconductor devices which are, so far, fabricated using expensive and complex processes requiring ultra-high vacuum equipment. Here we report on the possibility of growing a p-n junction taking advantage of electrochemical processes based on the use of aqueous solutions. The growth of the junction has been carried out using the Electrochemical Atomic Layer Deposition (E-ALD) technique, which allowed to sequentially deposit two different semiconductors, CdS and CuS, on an Ag(111) substrate, in a single procedure.

Effect of Anionic Lipids on Mammalian Plasma Cell Membrane Properties.

The effect of lipid composition on models of the inner leaflet of mammalian cell membranes has been investigated. Grazing incidence X-ray diffraction and X-ray and neutron reflectivity have been used to characterize lipid packing and solvation, while electrochemical and infrared spectroscopic methods have been employed to probe phase behavior in an applied electric field. Introducing a small quantity of the anionic lipid dimyristoylphosphatidylserine (DMPS) into bilayers of zwitterionic dimyristoylphosphatidylethanolamine (DMPE) results in a significant change in the bilayer response to an applied field: the tilt of the hydrocarbon chains increases before returning to the original tilt angle on detachment of the bilayer.

Templated electrodeposition as a scalable and surfactant-free approach to the synthesis of Au nanoparticles with tunable aspect ratios.

A high-throughput method for the fabrication of ordered arrays of Au nanoparticles is presented. It is based on pulsed electrodeposition into porous anodic alumina templates. In contrast to many synthesis routes, it is cyanide-free, prior separation of the alumina template from the aluminium substrate is not required, and the use of contaminating surfactants/capping agents often found in colloidal synthesis is avoided.

analysis of the nucleation of O- and Zn-polar ZnO nanowires using synchrotron-based X-ray diffraction.

The selection of the polarity of ZnO nanowires grown by chemical bath deposition offers a great advantage for their integration into a wide variety of engineering devices. However, the nucleation process of ZnO nanowires and its dependence on their polarity is still unknown despite its importance for optimizing their morphology and properties and thus to enhance the related device performances. To tackle this major issue, we combine an analysis of the nucleation process of O- and Zn-polar ZnO nanowires on O- and Zn-polar ZnO single crystals, respectively, using synchrotron radiation-based grazing incidence X-ray diffraction with transmission and scanning electron microscopy.

Quantitative powder diffraction using a (2 + 3) surface diffractometer and an area detector.

X-ray diffractometers primarily designed for surface X-ray diffraction are often used to measure the diffraction from powders, textured materials and fiber-texture samples in 2θ scans. Unlike in high-energy powder diffraction, only a fraction of the powder rings is typically measured, and the data consist of many detector images across the 2θ range. Such diffractometers typically scan in directions not possible on a conventional laboratory diffractometer, which gives enhanced control of the scattering vector relative to the sample orientation.

Studying the onset of galvanic steel corrosionusing thin films: film preparation, characterization and application to pitting.

This work reports about a novel approach for investigating surface processes during the early stages of galvanic corrosion of stainless steelby employing ultra-thin films and synchrotron x-radiation. Characterized by x-ray techniques and voltammetry, such films, sputter deposited from austenitic steel, were found representing useful replicas of the target material. Typical for stainless steel, the surface consists of a passivation layer of Fe- and Cr-oxides, a couple of nm thick, that is depleted of Ni.

Shedding light on membrane-templated clustering of gold nanoparticles.

The use of inorganic nanoparticles in biomedical and biotechnological applications requires a molecular-level understanding of interactions at nano-bio interfaces, such as cell membranes. Several recent reports have shown that gold nanoparticles (AuNP), in the presence of fluid lipid bilayers, aggregate at the lipid/aqueous interface, but the precise origin of this phenomenon is still not fully understood. Here, by challenging synthetic lipid membranes with one of the most typical classes of nanomaterials, citrate-coated AuNP, we addressed the cooperative nature of their interaction at the interface, which leads to AuNP clustering.

Biogenic supported lipid bilayers as a tool to investigate nano-bio interfaces.

Hypothesis: Extracellular Vesicles (EVs) are natural nanosized lipid vesicles involved in most intercellular communication pathways. Given their nature, they represent natural cell membrane models, with intermediate complexity between real and synthetic lipid membranes. Here we compare EVs-derived (EVSLB) and synthetic Supported Lipid Bilayers (SLBs) in the interaction with cationic superparamagnetic iron oxide nanoparticles (SPIONs).

Organothiol Monolayer Formation Directly on Muscovite Mica.

Organothiol monolayers on metal substrates (Au, Ag, Cu) and their use in a wide variety of applications have been extensively studied. Here, the growth of layers of organothiols directly onto muscovite mica is demonstrated using a simple procedure. Atomic force microscopy, surface X-ray diffraction, and vibrational sum-frequency generation IR spectroscopy studies revealed that organothiols with various functional endgroups could be self-assembled into (water) stable and adaptable ultra-flat organothiol monolayers over homogenous areas as large as 1 cm .

A novel 3D printed radial collimator for x-ray diffraction.

We demonstrate the use of a 3D printed radial collimator in X-ray powder diffraction and surface sensitive grazing incidence X-ray diffraction. We find a significant improvement in the overall signal to background ratio of up to 100 and a suppression of more than a factor 3 · 10 for undesirable Bragg reflections generated by the X-ray "transparent" windows of the sample environment. The background reduction and the removal of the high intensity signals from the windows, which limit the detector's dynamic range, enable significantly higher sensitivity in experiments within sample environments such as vacuum chambers and gas- or liquid-cells.

Nanoparticles at Biomimetic Interfaces: Combined Experimental and Simulation Study on Charged Gold Nanoparticles/Lipid Bilayer Interfaces.

The poor understanding of the interaction of nanomaterials with biologically relevant interfaces is recognized as one of the major issues currently limiting the development of nanomedicine. The central purpose of this study is to compare experimental (confocal microscopy, fluorescence correlation spectroscopy, X-ray reflectivity) and computational (molecular dynamics simulations) results to thoroughly describe the interaction of cationic gold nanoparticles (AuNPs) with mixed zwitterionic/anionic lipid membranes. The adhesion of AuNPs to the lipid membrane is investigated on different length scales from a structural and dynamical point of view; with this approach, a series of complex phenomena, spanning from lipid extraction, localized membrane disruption, lateral phase separation, and slaved diffusion, are characterized and interpreted from a molecular level to macroscopic observations.

Self-organization of porous anodic alumina films studied by grazing-incidence transmission small-angle X-ray scattering.

Self-ordered porous anodic alumina (PAA) films are studied extensively due to a large number of possible applications in nanotechnology and low cost of production. Whereas empirical relationships between growth conditions and produced oxides have been established, fundamental aspects regarding pore formation and self-organization are still under debate. We present structural studies of PAA films using grazing-incidence transmission small-angle X-ray scattering.

In-plane molecular organization of hydrated single lipid bilayers: DPPC:cholesterol.

Understanding the physical properties of cholesterol-phospholipid systems is essential to gain a better knowledge of the function of each membrane constituent. We present a novel, simple and user-friendly setup that allows for the straightforward grazing incidence X-ray diffraction characterization of hydrated individual supported lipid bilayers. This configuration minimizes the scattering from the liquid and allows the detection of the extremely weak diffracted signal of the membrane, enabling the differentiation of the coexisting domains in DPPC:cholesterol single bilayers.

Multiple timescales in the photoswitching kinetics of crystalline thin films of azobenzene-trimers.

Functional materials that exhibit photoinduced structural phase transitions are highly interesting for applications in optomechanics and mechanochemistry. It is, however, still not fully understood how photochemical reactions, which are often accompanied by molecular motion, proceed in confined and crystalline environments. Here we show that thin films of azobenzene trimers exhibit high structural order and determine the crystallographic unit cell.

Simultaneous scanning tunneling microscopy and synchrotron X-ray measurements in a gas environment.

A combined X-ray and scanning tunneling microscopy (STM) instrument is presented that enables the local detection of X-ray absorption on surfaces in a gas environment. To suppress the collection of ion currents generated in the gas phase, coaxially shielded STM tips were used. The conductive outer shield of the coaxial tips can be biased to deflect ions away from the tip core.

Operando SXRD study of the structure and growth process of CuS ultra-thin films.

Electrochemical Atomic Layer Deposition (E-ALD) technique has demonstrated to be a suitable process for growing compound semiconductors, by alternating the under-potential deposition (UPD) of the metallic element with the UPD of the non-metallic element. The cycle can be repeated several times to build up films with sub-micrometric thickness. We show that it is possible to grow, by E-ALD, CuS ultra-thin films on Ag(111) with high structural quality.

In situ studies of NO reduction by H over Pt using surface X-ray diffraction and transmission electron microscopy.

In situ surface X-ray diffraction and transmission electron microscopy at 1 bar show massive material transport of platinum during high-temperature NO reduction with H. A Pt(110) single-crystal surface shows a wide variety of surface reconstructions and extensive faceting of the surface. Pt nanoparticles change their morphology depending on the gas composition: They are faceted in hydrogen-rich environments, but are more spherical in NO-rich environments, indicating the formation of vicinal surfaces.

Structural Reorganization of Pt(111) Electrodes by Electrochemical Oxidation and Reduction.

The surface restructuring of Pt(111) electrodes upon electrochemical oxidation/reduction in 0.1 M HClO was studied by in situ grazing-incidence small-angle X-ray scattering and complementary scanning tunneling microscopy measurements. These methods allow quantitative determination of the formation and structural evolution of nanoscale Pt islands during potential cycles into the oxidation region.

Controlling the growth of Bi(110) and Bi(111) films on an insulating substrate.

We demonstrate the controlled growth of Bi(110) and Bi(111) films on an α-AlO(0001) substrate by surface x-ray diffraction and x-ray reflectivity using synchrotron radiation. At temperatures as low as 40 K, unanticipated pseudo-cubic Bi(110) films are grown with thicknesses ranging from a few to tens of nanometers. The roughness at the film-vacuum as well as the film-substrate interface, can be reduced by mild heating, where a crystallographic orientation transition of Bi(110) towards Bi(111) is observed at 400 K.

Influence of C co-deposition on the growth kinetics of diindenoperylene-From rapid roughening to layer-by-layer growth in blended organic films.

We investigated the growth of the two phase-separating materials diindenoperylene (DIP) and buckminsterfullerene C with different mixing ratio in real-time and in situ by X-ray scattering experiments. We found that at room temperature, mixtures with an excess of DIP show a growth mode which is very close to the perfect layer-by-layer limit with DIP crystallites forming over the entire film thickness. An unexpected increase in the island size is observed for these mixtures as a function of film thickness.

Structure and Nanomechanics of Model Membranes by Atomic Force Microscopy and Spectroscopy: Insights into the Role of Cholesterol and Sphingolipids.

Biological membranes mediate several biological processes that are directly associated with their physical properties but sometimes difficult to evaluate. Supported lipid bilayers (SLBs) are model systems widely used to characterize the structure of biological membranes. Cholesterol (Chol) plays an essential role in the modulation of membrane physical properties.

Combined scanning probe microscopy and x-ray scattering instrument for in situ catalysis investigations.

We have developed a new instrument combining a scanning probe microscope (SPM) and an X-ray scattering platform for ambient-pressure catalysis studies. The two instruments are integrated with a flow reactor and an ultra-high vacuum system that can be mounted easily on the diffractometer at a synchrotron end station. This makes it possible to perform SPM and X-ray scattering experiments in the same instrument under identical conditions that are relevant for catalysis.