"On-The-Fly" Synthesis of Self-Supported LDH Hollow Structures Through Controlled Microfluidic Reaction-Diffusion Conditions.

Layered double hydroxides (LDHs) are a class of functional materials that exhibit exceptional properties for diverse applications in areas such as heterogeneous catalysis, energy storage and conversion, and bio-medical applications, among others. Efforts have been devoted to produce millimeter-scale LDH structures for direct integration into functional devices. However, the controlled synthesis of self-supported continuous LDH materials with hierarchical structuring up to the millimeter scale through a straightforward one-pot reaction method remains unaddressed. Herein, it is shown that millimeter-scale self-supported LDH structures can be produced by means of a continuous flow microfluidic device in a rapid and reproducible one-pot process. Additionally, the microfluidic approach not only allows for an "on-the-fly" formation of unprecedented LDH composite structures, but also for the seamless integration of millimeter-scale LDH structures into functional devices. This method holds the potential to unlock the integrability of these materials, maintaining their performance and functionality, while diverging from conventional techniques like pelletization and densification that often compromise these aspects. This strategy will enable exciting advancements in LDH performance and functionality.

Filler-Enhanced Piezoelectricity of Poly-L-Lactide and Its Use as a Functional Ultrasound-Activated Biomaterial.

Poly-L-lactide (PLLA) offers a unique possibility for processing into biocompatible, biodegradable, and implantable piezoelectric structures. With such properties, PLLA has potential to be used as an advanced tool for mimicking biophysical processes that naturally occur during the self-repair of wounds and damaged tissues, including electrostimulated regeneration. The piezoelectricity of PLLA strongly depends on the possibility of controlling its crystallinity and molecular orientation. Here, it is shown that modifying PLLA with a small amount (1 wt%) of crystalline filler particles with a high aspect ratio, which act as nucleating agents during drawing-induced crystallization, promotes the formation of highly crystalline and oriented PLLA structures. This increases their piezoelectricity, and the filler-modified PLLA films provide a 20-fold larger voltage output than nonmodified PLLA during ultrasound (US)-assisted activation. With 99% PLLA content, the ability of the films to produce reactive oxygen species (ROS) and increase the local temperature during interactions with US is shown to be very low. US-assisted piezostimulation of adherent cells directly attach to their surface (such as skin keratinocytes), stimulate cytoskeleton formation, and as a result cells elongate and orient themselves in a specific direction that align with the direction of PLLA film drawing and PLLA dipole orientation.

When Identification of the Reduction Sites in Mixed Molybdenum/Tungsten Keggin-Type Polyoxometalate Hybrids Turns Out Tricky.

The mixed molybdenum/tungsten Keggin-type polyoxometalate (POM) hybrid (TBA)4[PW9Mo2O39{Sn(C6H4I)}] (TBA = tert-butylammonium) has been prepared by the reaction between [α-PW9Mo2O39]7- and [Cl3Sn(C6H4I)] in dried acetonitrile, in the presence of tetra-n-butylammonium bromide. A further coupling reaction affords the ferrocenyl derivative (TBA)4[PW9Mo2O39{Sn(C6H4)C≡C(C6H4)Fc}]. The POM hybrids have been thoroughly characterized by NMR and IR spectroscopies. Electrochemical analysis confirms their ease of reduction compared to the all-W analogue, albeit with a second reduction process occurring at a lower potential than in the all-Mo species. It is noteworthy that the second reduction is accompanied by an unusual red shift of the electronic absorption spectrum. Whereas there is no doubt that the first reduction deals with Mo, the location of the second electron in the bireduced species, on the second Mo or on W, has thus been the subject of a cross-investigation by spectroelectrochemistry, electron spin resonance, and theoretical calculations. Finally, it came out that the second reduction is also Mo-centered with two unpaired and antiferromagnetically coupled extra electrons.

Self-assembled monolayers on a ferromagnetic permalloy surface.

Self-assembled monolayers (SAMs) are nowadays broadly used as surface protectors or modifiers and play a key role in many technological applications. This has motivated the study of their formation in all kind of materials; however, and despite the current interest in molecular spintronics, the study of SAMs on ferromagnetic surfaces remains almost unexplored. In this paper, we report for the first time a methodology for the formation of SAMs of n-alkylphosphonic acids on permalloy in ambient conditions. The formed monolayers have been fully characterized by means of contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry, infrared reflection absorption spectroscopy, and X-ray reflectometry. Additionally, the magnetic stability of the modified permalloy after the solution process required for the SAM formation has been confirmed by magneto-optical Kerr effect magnetometry. Moreover, by means of microcontact printing lithography, very accurate SAM patterns have been transferred onto permalloy surfaces and used as resist mask in a chemical etching process giving rise to submicrometric permalloy surface patterns with potential interest in nanomagnetism, spintronics, and storage technologies.

Ready-to-be-addressed oxo-clusters: individualized, periodically organized and separated from the substrate.

Clusters and oxo-clusters are drawing attention for their amazing physical properties, especially at the scale of the single molecule. However, chemical methods to organize them individually on a surface are still lacking. In this study we show that it is possible to periodically organize individual polyoxometalates thanks to their ordering by a new supramolecular assembly.

Spontaneous growth of 2D coordination polymers on functionalized ferromagnetic surfaces.

The spontaneous growth of lamellar metal-alkanethiolates (LMAs) on reactive ferromagnetic surfaces as a result of surface oxidation has been observed. When alkanethiol self-assembled monolayers (SAMs) grown under an inert atmosphere over cobalt or permalloy (Ni80Fe20) are exposed to air, oxygen diffuses through the molecular layer. This induces an oxidation of metal atoms at the metal surface and a release of the resulting metal cations that migrate coordinated by the alkanethiol molecules to form lamellar structures over the SAMs. This process has been imaged in real-time, under ambient conditions, by means of different microscopy techniques. The influence of the alkyl chain length, the nature of the ferromagnet, the temperature and the atmospheric moisture on the number, area and height of the resulting features has been systematically evaluated. Remarkably, the possibility to follow the migration in real-time makes it a promising model system for the study of surface/molecule interface processes. Most importantly, the composition and crystallinity of these LMAs have been studied, evidencing that real 2D coordination polymers are formed on the surface. Hence, one could envision this strategy as a new method for the assembly of more complex low-dimensional (2D) magnetic materials based on coordination polymers.

Bottom-Up Fabrication of Semiconductive Metal-Organic Framework Ultrathin Films.

Though generally considered insulating, recent progress on the discovery of conductive porous metal-organic frameworks (MOFs) offers new opportunities for their integration as electroactive components in electronic devices. Compared to classical semiconductors, these metal-organic hybrids combine the crystallinity of inorganic materials with easier chemical functionalization and processability. Still, future development depends on the ability to produce high-quality films with fine control over their orientation, crystallinity, homogeneity, and thickness. Here self-assembled monolayer substrate modification and bottom-up techniques are used to produce preferentially oriented, ultrathin, conductive films of Cu-CAT-1. The approach permits to fabricate and study the electrical response of MOF-based devices incorporating the thinnest MOF film reported thus far (10 nm thick).