Advanced piezoresistance of extended metal/insulator core shell nanoparticle assemblies

Assembled metal/insulator nanoparticles with a core/shell geometry provide access to materials containing a large number (>106) of tunneling barriers. We demonstrate the production of ceramic coated metal nanoparticles exhibiting an exceptional pressure sensitive conductivity. We further show that graphene bi- and trilayers on 20 nm copper nanoparticles are insulating in such core/shell geometry and show a similar pressure dependent conductivity. This demonstrates that core/shell metal/insulator assemblies offer a route to alternative sensing materials.Comment: 14 pages, 3 figures, published in Physical Review Letter

Scalable photonic sources using two-dimensional lead halide perovskite superlattices

Miniaturized photonic sources based on semiconducting two-dimensional (2D) materials offer new technological opportunities beyond the modern III-V platforms. For example, the quantum-confined 2D electronic structure aligns the exciton transition dipole moment parallel to the surface plane, thereby outcoupling more light to air which gives rise to high-efficiency quantum optics and electroluminescent devices. It requires scalable materials and processes to create the decoupled multi-quantum-well superlattices, in which individual 2D material layers are isolated by atomically thin quantum barriers. Here, we report decoupled multi-quantum-well superlattices comprised of the colloidal quantum wells of lead halide perovskites, with unprecedentedly ultrathin quantum barriers that screen interlayer interactions within the range of 6.5 Å. Crystallographic and 2D k-space spectroscopic analysis reveals that the transition dipole moment orientation of bright excitons in the superlattices is predominantly in-plane and independent of stacking layer and quantum barrier thickness, confirming interlayer decoupling

Solid-State Lifshitz-van der Waals Repulsion through Two-Dimensional Materials

The van der Waals (vdW) force is a ubiquitous short-range interaction between atoms and molecules that underlies many fundamental phenomena. Early pairwise additive theories pioneered by Keesom, Debye, and London suggested the force to be monotonically attractive for separations larger than the vdW contact distance. However, seminal work by Lifshitz et al. predicted that quantum fluctuations can change the sign of vdW interactions from attractive to repulsive. Although recent experiments carried out in fluid environment have demonstrated the long-range counterpart the Casimir repulsion, it remains controversial whether the vdW repulsion exists, or is sufficiently strong to alter solid-state properties. Here we show that the atomic thickness and birefringent nature of two-dimensional (2D) materials, arising from their anisotropic dielectric responses, make them a versatile medium to tailor the many-body Lifshitz-vdW interactions at solid-state interfaces. Based on our theoretical prediction, we experimentally examine two heterointerface systems in which the vdW repulsion becomes comparable to the two-body attraction. We demonstrate that the in-plane movement of gold atoms on a sheet of freestanding graphene becomes nearly frictionless at room temperature. Repulsion between molecular solid and gold across graphene results in a new polymorph with enlarged out-of-plane lattice spacings. The possibility of creating repulsive energy barriers in nanoscale proximity to an uncharged solid surface offers technological opportunities such as single-molecule actuation and atomic assembly

Structure Sensitivity and Evolution of Nickel-Bearing Nitrogen-Doped Carbons in the Electrochemical Reduction of CO2

The emergence of nickel single atoms on nitrogen-doped carbons as high-performance catalysts amenable to rationalization due to their well-defined structure could lead to applicable technologies for the electrocatalytic CO2 reduction reaction (eCO2RR). However, real materials are unlikely to display a uniform site structure, which limits the scope of current efforts focused on idealized models for future implementation. Here, we prepare distinct nickel entities (single atoms or nanoparticles) on nitrogen-doped carbons and evaluate them in eCO2RR. Single atoms demonstrate a characteristic high selectivity to CO. However, this is not altered by the presence of metal nanoparticles formed upon reducing the nitrogen content of the carrier. In contrast, nanoparticles incorporated via a colloidal route promote the parasitic hydrogen evolution reaction. In these systems, the CO selectivity evolves upon repeated exposure to potential, reaching values comparable to single atoms. By introducing CO stripping voltammetry as a characterization tool for this class of materials, we identify a decreased metallic surface, suggesting that the nanoparticle surface is altered by CO. The findings highlight the critical role of dynamic effects in catalyst design for eCO2RR

Platinum–Vanadium Oxide Nanotube Hybrids

The present contribution reports on the features of platinum-based systems supported on vanadium oxide nanotubes. The synthesis of nanotubes was carried out using a commercial vanadium pentoxide via hydrothermal route. The nanostructured hybrid materials were prepared by wet impregnation using two different platinum precursors. The formation of platinum nanoparticles was evaluated by applying distinct reduction procedures. All nanostructured samples were essentially analysed by X-ray diffraction and transmission electron microscopy. After reduction, transmission electron microscopy also made it possible to estimate particle size distribution and mean diameter calculations. It could be seen that all reduction procedures did not affect the nanostructure of the supports and that the formation of metallic nanoparticles is quite efficient with an indistinct distribution along the nanotubes. Nevertheless, the reduction procedure determined the diameter, dispersion and shape of the metallic particles. It could be concluded that the use of H2PtCl6 is more suitable and that the use of hydrogen as reducing agent leads to a nanomaterial with unagglomerated round-shaped metallic particles with mean size of 6–7 nm

Intrafamilial oocyte donation in classic galactosemia: ethical and societal aspects

Classic galactosemia is a rare inherited disorder of galactose metabolism. Primary ovarian insufficiency (POI) with subfertility affects > 80% of female patients and is an important concern for patients and their parents. Healthcare providers are often consulted for subfertility treatment possibilities. An option brought up by the families is intrafamilial oocyte donation (mother-to-daughter or sister-to-sister). In addition to POI, galactosemia patients can also present varying cognitive and neurological impairments, which may not be fully clear at the time when mother-to-daughter oocyte donation is considered. Ethical and societal aspects arise when exploring this option. This study aimed to provide guidance in aspects to consider based on the views of different groups involved in the oocyte donation process. A qualitative study using in-depth semi-structured interviews with > 50 participants (patients, family members, and healthcare providers) was conducted. From these interviews, themes of concern emerged, which are illustrated and reviewed: (1) family relations, (2) medical impact, (3) patients’ cognitive level, (4) agreements to be made in advance and organization of counseling, (5) disclosure to the child, and (6) need for follow-up. We conclude that discussing and carrying out intrafamilial oocyte donation in galactosemia patients requires carefully addressing these themes. This study adds value to the already existing recommendations on intrafamilial oocyte donation in general, since it highlights important additional aspects from the perspectives of patients and their families

Persistence of engineered nanoparticles in a municipal solid-waste incineration plant

More than 100 million tonnes of municipal solid waste are incinerated worldwide every year1. However, little is known about the fate of nanomaterials during incineration, even though the presence of engineered nanoparticles in waste is expected to grow2. Here, we show that cerium oxide nanoparticles introduced into a full-scale waste incineration plant bind loosely to solid residues from the combustion process and can be efficiently removed from flue gas using current filter technology. The nanoparticles were introduced either directly onto the waste before incineration or into the gas stream exiting the furnace of an incinerator that processes 200,000 tonnes of waste per year. Nanoparticles that attached to the surface of the solid residues did not become a fixed part of the residues and did not demonstrate any physical or chemical changes. Our observations show that although it is possible to incinerate waste without releasing nanoparticles into the atmosphere, the residues to which they bind eventually end up in landfills or recovered raw materials, confirming that there is a clear environmental need to develop degradable nanoparticles

Rab27a and Rab27b control different steps of the exosome secretion pathway

Exosomes are secreted membrane vesicles that share structural and biochemical characteristics with intraluminal vesicles of multivesicular endosomes (MVEs). Exosomes could be involved in intercellular communication and in the pathogenesis of infectious and degenerative diseases. The molecular mechanisms of exosome biogenesis and secretion are, however, poorly understood. Using an RNA interference (RNAi) screen, we identified five Rab GTPases that promote exosome secretion in HeLa cells. Among these, Rab27a and Rab27b were found to function in MVE docking at the plasma membrane. The size of MVEs was strongly increased by Rab27a silencing, whereas MVEs were redistributed towards the perinuclear region upon Rab27b silencing. Thus, the two Rab27 isoforms have different roles in the exosomal pathway. In addition, silencing two known Rab27 effectors, Slp4 (also known as SYTL4, synaptotagmin-like 4) and Slac2b (also known as EXPH5, exophilin 5), inhibited exosome secretion and phenocopied silencing of Rab27a and Rab27b, respectively. Our results therefore strengthen the link between MVEs and exosomes, and introduce ways of manipulating exosome secretion in vivo

Hepatitis B screening in the Turkish-Dutch population in Rotterdam, the Netherlands; qualitative assessment of socio-cultural determinants

Background. Hepatitis B is an important health problem in the Turkish community in the Netherlands. Increased voluntary screening is necessary in this community, to detect individuals eligible for treatment and to prevent further transmission of the disease. Methods. We investigated socio-cultural determinants associated with hepatitis B screening in male and female, first and second generation Turkish migrants, by means of Focus Group Discussions. Results. Socio-cultural themes related to hepatitis B screening were identified; these were social norm, social support, sensitivity regarding sexuality, reputation, responsiveness to authority, religious responsibility, cleanliness and religious doctrine regarding health and disease, and the perceived efficacy of Dutch health care services. Motivating factors were the (religious) responsibility for one's health, the perceived obligation when being invited for screening, and social support to get tested for hepatitis B. Perceived barriers were the association of hepatitis B screening with STDs or sexual activity, the perception of low control over one's health, and the perceived low efficacy of the Dutch health care services. Reputation could act as either a motivator or barrier. Conclusion. This study identified relevant socio-cultural themes related to hepatitis B screening, which may serve to customize interventions aimed at the promotion of voluntary hepatitis B screening in the Turkish-Dutch population in the Netherlands