Using the Quartz Crystal Microbalance to Monitor the Curing of Drying Oils.

Drying oils such as linseed oil form a polymer network through a complex free-radical polymerization process. We have studied polymerization in this challenging class of polymers using a quartz crystal microbalance (QCM). The QCM is able to measure the evolution of polymer mass and mechanical properties as the oil transitions from a liquid-like to a solid-like state. Measurements using bulk materials and thin films provide information about the initial polymerization phase as well as the evolution of the mass and mechanical properties over the first two years of cure. The temperature-dependent response of the cured linseed oil films was also measured. These results were combined with previously published results obtained from traditional dynamic mechanical analysis to give a unified picture of the properties of these materials across a very broad temperature range.

Thermo-temporal physisorption in metal-organic frameworks probed by cyclic thermo-ellipsometry.

Temperature-induced sorption in porous materials is a well-known process. What is more challenging is to determine how the rate at which temperature is varied affects these processes. To address this question, we introduce a methodology called "cyclic thermo-ellipsometry" to explore the thermo-kinetics of vapor physisorption in metal-organic framework films.

Programming crack patterns with light in colloidal plasmonic films.

Crack formation observed across diverse fields like geology, nanotechnology, arts, structural engineering or surface science, is a chaotic and undesirable phenomenon, resulting in random patterns of cracks generally leading to material failure. Limiting the formation of cracks or "programming" the path of cracks is a great technological challenge since it holds promise to enhance material durability or even to develop low cost patterning methods. Drawing inspiration from negative phototropism in plants, we demonstrate the capability to organize, guide, replicate, or arrest crack propagation in colloidal films through remote light manipulation. The key consists in using plasmonic photothermal absorbers to generate "virtual" defects enabling controlled deviation of cracks. We engineer a dip-coating process coupled with selective light irradiation enabling simultaneous deposition and light-directed crack patterning. This approach represents a rare example of a robust self-assembly process with long-range order that can be programmed in both space and time.

Multifunctional, Hybrid Materials Design via Spray-Drying: Much more than Just Drying.

Spray-drying is a popular and well-known "drying tool" for engineers. This perspective highlights that, beyond this application, spray-drying is a very interesting and powerful tool for materials chemists to enable the design of multifunctional and hybrid materials. Upon spray-drying, the confined space of a liquid droplet is narrowed down, and its ingredients are forced together upon "falling dry." As  detailed in this article, this enables the following material formation strategies either individually or even in combination: nanoparticles and/or molecules can be assembled; precipitation reactions as well as chemical syntheses can be performed; and templated materials can be designed. Beyond this, fragile moieties can be processed, or "precursor materials" be prepared. Post-treatment of spray-dried objects eventually enables the next level in the design of complex materials. Using spray-drying to design (particulate) materials comes with many advantages-but also with many challenges-all of which are outlined here. It is believed that multifunctional, hybrid materials, made via spray-drying, enable very unique property combinations that are particularly highly promising in myriad applications-of which catalysis, diagnostics, purification, storage, and information are highlighted.

High-Entropy-Alloy Nanocrystal Based Macro- and Mesoporous Materials.

High-entropy-alloy (HEA) nanoparticles are attractive for several applications in catalysis and energy. Great efforts are currently devoted to establish composition-property relationships to improve catalytic activity or selectivity. Equally importantly, developing practical fabrication methods for shaping HEA-based materials into complex architectures is a key requirement for their utilization in catalysis. However, shaping nano-HEAs into hierarchical structures avoiding demixing or collapse remains a great challenge. Herein, we overcome this issue by introducing a simple soft-chemistry route to fabricate ordered macro- and mesoporous materials based on HEA nanoparticles, with high surface area, thermal stability, and catalytic activity toward CO oxidation. The process is based on spray-drying from an aqueous solution containing five different noble metal precursors and polymer latex beads. Upon annealing, the polymer plays a double role: templating and reducing agent enabling formation of HEA nanoparticle-based porous networks at only 350 °C. The formation mechanism and the stability of the macro- and mesoporous materials were investigated by a set of in situ characterization techniques; notably, in situ transmission electron microscopy unveiled that the porous structure is stable up to 800 °C. Importantly, this process is green, scalable, and versatile and could be potentially extended to other classes of HEA materials.

Periodic Nanoporous Inorganic Patterns Directly Made by Self-Ordering of Cracks.

Solution-processed inorganic nanoporous films are key components for the vast spectrum of applications ranging from dew harvesting to solar cells. Shaping them into complex architectures required for advanced functionality often needs time-consuming or expensive fabrication. In this work, crack formation is harnessed to pattern porous inorganic films in a single step and without using lithography. Aqueous inks, containing inorganic precursors and polymeric latexes enable evaporation-induced, defect-free periodic arrays of cracks with tunable dimensions over several centimeters. The ink formulation strategy is generalized to more than ten inorganic materials including simple and binary porous oxide and metallic films covering a whole spectrum of properties including insulating, photocatalytic, electrocatalytic, conductive, or electrochromic materials. Notably, this approach enables 3D self-assembly of cracks by stacking several layers of different compositions, yielding periodic assemblies of polygonal shapes and Janus-type patterns. The crack patterned periodic arrays of nanoporous TiO2 diffract light, and are used as temperature-responsive diffraction grating sensors. More broadly, this method represents a unique example of a self-assembly process leading to long-range order (over several centimeters) in a robust and controlled way.

Deep X-ray lithography on "sol-gel" processed noble metal mesoarchitectured films.

Noble metal coordination xerogel films (mesostructured with block-copolymers) exhibit solubility switching with increasing X-ray irradiation. Different from other sol-gel systems, these are attributed to film deconstruction under irradiation. These materials can be used as recyclable negative tone resists for deep X-ray lithography that can be further converted into metallic nanoarchitectured films.

Block-Copolymers Enable Direct Reduction and Structuration of Noble Metal-Based Films.

Noble metal nanostructured films are of great interest for various applications including electronics, photonics, catalysis, and photocatalysis. Yet, structuring and patterning noble metals, especially those of the platinum group, is challenging by conventional nanofabrication. Herein, an approach based on solution processing to obtain metal-based films (rhodium, ruthenium (Ru) or iridium in the presence of residual organic species) with nanostructuration at the 20 nm-scale is introduced. Compared to existing approaches, the dual functionality of block-copolymers acting both as structuring and as reducing agent under inert atmosphere is exploited. A set of in situ techniques has allowed for the capturing of the carbothermal reduction mechanism occurring at the hybrid organic/inorganic interface. Differently from previous literature, a two-step reduction mechanism is unveiled with the formation of a carbonyl intermediate. From a technological point of view, the materials can be solution-processed on a large scale by dip-coating as polymers and simultaneously structured and reduced into metals without requiring expensive equipment or treatments in reducing atmosphere. Importantly, the metal-based films can be patterned directly by block-copolymer lithography or by soft-nanoimprint lithography on various substrates. As proof-of-concept of application, the authors demonstrate that nanostructured Ru films can be used as efficient catalysts for H2 generation into microfluidic reactors.

Metal-Organic Framework Photonic Balls: Single Object Analysis for Local Thermal Probing.

Due to their high porosity and chemical versatility, metal-organic frameworks (MOFs) exhibit physical properties appealing for photonic-based applications. While several MOF photonic structures have been reported, examples of applications thereof are mainly limited to chemical sensing. Herein, the range of application of photonic MOFs is extended to local thermal and photothermal sensing by integrating them into a new architecture: MOF photonic balls. Micrometric-sized photonic balls are made of monodispersed MOFs colloids that are self-assembled via spray-drying, a low-cost, green, and high-throughput method. The versatility of the process allows tuning the morphology and the composition of photonic balls made of several MOFs and composites with tailored optical properties. X-ray nanotomography and environmental hyperspectral microscopy enable analysis of single objects and their evolution in controlled atmosphere and temperature. Notably, in presence of vapors, the MOF photonic balls act as local, label-free temperature probes. Importantly, compared to other thermal probes, the temperature detection range of these materials can be adjusted "on-demand." As proof of concept, the photonic balls are used to determine local temperature profiles around a concentrated laser beam. More broadly, this work is expected to stimulate new research on the physical properties of photonic MOFs providing new possibilities for device fabrication.

The origin of the high electrochemical activity of pseudo-amorphous iridium oxides.

Combining high activity and stability, iridium oxide remains the gold standard material for the oxygen evolution reaction in acidic medium for green hydrogen production. The reasons for the higher electroactivity of amorphous iridium oxides compared to their crystalline counterpart is still the matter of an intense debate in the literature and, a comprehensive understanding is needed to optimize its use and allow for the development of water electrolysis. By producing iridium-based mixed oxides using aerosol, we are able to decouple the electronic processes from the structural transformation, i.e. Ir oxidation from IrO2 crystallization, occurring upon calcination. Full characterization using in situ and ex situ X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron microscopy allows to unambiguously attribute their high electrochemical activity to structural features and rules out the iridium oxidation state as a critical parameter. This study indicates that short-range ordering, corresponding to sub-2nm crystal size for our samples, drives the activity independently of the initial oxidation state and composition of the calcined iridium oxides.

Replacing Metals with Oxides in Metal-Assisted Chemical Etching Enables Direct Fabrication of Silicon Nanowires by Solution Processing.

Metal-assisted chemical etching (MACE) has emerged as an effective method to fabricate high aspect ratio nanostructures. This method requires a catalytic mask that is generally composed of a metal. Here, we challenge the general view that the catalyst needs to be a metal by introducing oxide-assisted chemical etching (OACE). We perform etching with metal oxides such as RuO2 and IrO2 by transposing materials used in electrocatalysis to nanofabrication. These oxides can be solution-processed as polymers exhibiting similar capabilities of metals for MACE. Nanopatterned oxides can be obtained by direct nanoimprint lithography or block-copolymer lithography from chemical solution on a large scale. High aspect ratio silicon nanostructures were obtained at the sub-20 nm scale exclusively by cost-effective solution processing by halving the number of fabrication steps compared to MACE. In general, OACE is expected to stimulate new fundamental research on chemical etching assisted by other materials, providing new possibilities for device fabrication.

Introducing cobalt as a potential plasmonic candidate combining optical and magnetic functionalities within the same nanostructure.

The control of magnetic properties at the nanoscale is a current topic of intense research. It was shown that combining both magnetic and plasmonic nanoparticles (NPs) led to the improvement of their magneto-optical signal. In this context, common strategies consist of the design of bimetallic NPs. However, the understanding of the physics leading to the coupling between magnetic and plasmonic NPs is lacking, preventing any significant progress for the development of future photonic devices. In this article, we propose to focus our attention on an efficient and commonly used magnetic metal, cobalt, and evaluate its plasmonic properties at the nanoscale through the use of NP regular arrays, as a potential candidate combining both optical and magnetic functionalities within the same metal. We show that such NPs display plasmonic properties within a large spectral range from the UV to the NIR spectral range, with efficient quality factors, when the inter-particle distance is properly selected. These as-fabricated simple materials could find applications in integrated photonic devices for telecommunications.

Endosonographic evaluation of the mediastinum through the i-gel O2 supraglottic airway device.

INTRODUCTION: Endobronchial ultrasound (EBUS) is an endoscopic diagnostic procedure combining flexible fibrobronchoscopy with ultrasound techniques; it allows transbronchial needle aspiration biopsy for the diagnosis and staging of mediastinal masses. We present our preliminary experience with the use of the i-gel O2 supraglottic airway device for management of EBUS procedures. METHODS: An observational study on 39 patients who underwent EBUS under general anesthesia was performed. Airways were managed with i-gel O2 by anesthesiologists unfamiliar with it. Data collected included patient characteristics, i-gel O2 positioning, mechanical ventilation, procedure, and complications occurring during and after the EBUS. RESULTS: The i-gel airway was successfully positioned during the first attempt in 34/39 cases (87.2%). No failed positioning was recorded. The EBUS scope easily passed through the i-gel in all patients and in 14 (35.6%) cases it was also inserted through the esophagus allowing the examination or fine needle aspiration of paraesophageal lymph nodes. In one case, during the EBUS procedure, the i-gel was dislocated but easily put in place again. During EBUS, air leakages were significant in 2 cases (5.1%) and minimal in 14 cases (35.9%). A brief self-solved laryngospasm and a bronchospasm during bronchoscopy were recorded. After recovery, no patients had dysphagia; mild odynophagia and pharyngodinia were referred by 2 (5.1%) and 12 (30.1%) patients, respectively. CONCLUSIONS: The i-gel O2 airway is easy to position and manage even for anesthesiologists unfamiliar with it. This supraglottic airway device is suitable for a complete endosonographic evaluation of the mediastinum.

Origin of transparency in scattering biomimetic collagen materials.

Living tissues, heterogeneous at the microscale, usually scatter light. Strong scattering is responsible for the whiteness of bones, teeth, and brain and is known to limit severely the performances of biomedical optical imaging. Transparency is also found within collagen-based extracellular tissues such as decalcified ivory, fish scales, or cornea. However, its physical origin is still poorly understood. Here, we unveil the presence of a gap of transparency in scattering fibrillar collagen matrices within a narrow range of concentration in the phase diagram. This precholesteric phase presents a three-dimensional (3D) orientational order biomimetic of that in natural tissues. By quantitatively studying the relation between the 3D fibrillar network and the optical and mechanical properties of the macroscopic matrices, we show that transparency results from structural partial order inhibiting light scattering, while preserving mechanical stability, stiffness, and nonlinearity. The striking similarities between synthetic and natural materials provide insights for better understanding the occurring transparency.

Nanoconfined water vapour as a probe to evaluate plasmonic heating.

Engineering photothermal effects in plasmonic materials is of paramount importance for many applications, such as cancer therapy, chemical synthesis, cold catalysis and, more recently, metasurfaces. The evaluation of plasmonic heating at the nanoscale is challenging and generally requires sophisticated equipments and/or temperature-sensitive probes such as fluorescent molecules or materials. Here, we propose to use water vapor as a probe to evaluate the local heating around plasmonic nanoparticles. We demonstrate the concept for the case of a plasmonic colloidal film characterized by bi-modal nanoporosity. In particular, we exploit the thermal and light water liquid-vapor phase transitions taking place in the nanoporous medium that can be triggered by external stimuli, such as heating or irradiation, to obtain structural and optical variations in the film. The local temperature is then estimated using spectroscopic ellipsometry data acquired by a multimodal chamber. More generally, this method offers a simple and general approach to determine the local temperature that only requires a nanoporous material and water vapor, such as environmental humidity. In addition, this approach can be further generalized to other materials, vapor molecules or optical techniques.

Following in Situ the Degradation of Mesoporous Silica in Biorelevant Conditions: At Last, a Good Comprehension of the Structure Influence.

Mesoporous silica nanoparticles (MSNs) have seen a fast development as drug delivery carriers thanks to their tunable porosity and high loading capacity. The employ of MSNs in biomedical applications requires a good understanding of their degradation behavior both to control drug release and to assess possible toxicity issues on human health. In this work, we study mesoporous silica degradation in biologically relevant conditions through in situ ellipsometry on model mesoporous nanoparticle or continuous thin films, in buffer solution and in media containing proteins. In order to shed light on the structure/dissolution relationship, we performed dissolution experiments far from soluble silicate species saturation. Via a complete decorrelation of dissolution and diffusion contributions, we proved unambiguously that surface area of silica vectors is the main parameter influencing dissolution kinetics, while thermal treatment and open mesoporous network architecture have a minor impact. As a logical consequence of our dissolution model, we proved that the dissolution lag-time can be promoted by selective blocking of the mesopores that limits the access to the mesoporous internal surface. This study was broadened by studying the impact of the organosilanes in the silica structure, of the presence of residual structuring agents, and of the chemical composition of the dissolution medium. The presence of albumin at blood concentration was found affecting drastically the dissolution kinetics of the mesoporous structure, acting as a diffusion barrier. Globally, we could identify the main factors affecting mesoporous silica materials degradation and proved that we can tune their structure and composition for adjusting dissolution kinetics in order to achieve efficient drug delivery.

Myasthenia gravis imitating pituitary apoplexy in macroprolactinoma.

Myasthenia gravis (MG) is an autoimmune disease affecting neuromuscular transmission that manifests with muscle weakness and typically involves the eye muscles, often producing diplopia and ptosis. Recent studies suggest that hyperprolactinaemia may have a role in the development of MG, although its association with prolactinoma is extremely rare. We report the unusual case of a 71-year-old male affected with macroprolactinoma, who presented at our Center 2 weeks after starting cabergoline treatment because of acute onset of headache, diplopia, and ptosis. On admission, he presented with drowsiness, dropped head, swallowing impairment and bilateral ptosis, which rapidly worsened. Based on clinical manifestation and history, emergency surgery was performed on suspicion of pituitary apoplexy (PA), the typical complication occurring in patients with macroadenomas who present these symptoms. No pituitary haemorrhage was found. The symptoms initially resolved after surgery, but soon returned and worsened day by day, especially in the evening, despite the increase of cortisone replacement doses. MG was thus suspected and confirmed by the detection of antibodies to the acetylcholine receptor. Pyridostigmine was started with prompt improvement of neurological symptoms. In conclusion, although very rare, MG should be considered in the differential diagnosis of patients with macroprolactinomas and suggestive neurological symptoms in order to provide early and appropriate treatment. The role of hyperprolactinaemia in MG onset and evolution is also discussed.

Dynamic Shaping of Femtoliter Dew Droplets.

Herein, we show that wetting properties such as giant wetting anisotropy and dynamic shaping can be observed when femtoliter (submicron scale) dew droplets are condensed on nanopatterned mildly hydrophilic surfaces. Large-scale, optically transparent, nanopatterned TiO2 surfaces were fabricated by direct nanoimprinting lithography of sol-gel-derived films. Square, infinitely elongated, or circular droplets were obtained with square, line, or concentric patterns, respectively, and were visualized in situ during formation and recession using optical microscopy and environmental scanning electronic microscopy. We first describe how extremely elongated droplets could form on mildly hydrophilic surfaces, naturally contaminated in real environmental conditions. In this configuration, the dew droplet shape can be dynamically and reversibly varied by controlling the out-of-equilibrium conditions associated with condensation/evaporation kinetics. As an example of the application, we propose a "morphological" sensor that exploits the shape of the dew droplets as a transduction mode for detecting organic vapors in the outer atmosphere. Importantly, this study is underlining that environmentally stable, purely hydrophilic surfaces can be smartly engineered to induce wetting phenomena at very small scale never observed so far for hydrophobic or heterogeneous surfaces. Our versatile approach based on nanoimprinted, transparent sol-gel films could open great perspectives for the implementation of environmentally stable, mildly hydrophilic materials for "dew engineering" applications such as open microfluidics, fuming for fingerprints, vapor sensing, or water harvesting on glass windows, for instance.

Environment-controlled sol-gel soft-NIL processing for optimized titania, alumina, silica and yttria-zirconia imprinting at sub-micron dimensions.

Metal oxide (MOX) surface nanopatterns can be prepared using Soft-Nano-Imprint-Lithography (soft-NIL) combined with sol-gel deposition processing. Even if sol-gel layers remain gel-like straight after deposition, their accurate replication from a mould remains difficult as a result of the fast evaporation-induced stiffening that prevents efficient mass transfer underneath the soft mould. The present work reports a detailed investigation of the role of the xerogel layer conditioning (temperature and relative humidity) prior to imprinting and its influence on the quality of the replication. This study is performed on four different systems namely titania, alumina, silica and yttria-stabilised zirconia. We demonstrate that the quality of the replica can be considerably improved without the use of sacrificial stabilising organic agents, but by simply applying an optimal aging at controlled temperature and relative humidity specific to each different reported MOX. In each case this condition corresponds to swelling the initial xerogels of around 30%vol by water absorption from humidity. We show that this degree of swelling represents the best compromise for sufficiently increasing the xerogel fluidity while limiting the shrinkage upon final thermal curing.