Centre de microcaractérisation Raimond Castaing

Abstract Tremendous efforts have been invested in the development of the internet of things during the past 10 years. Implantable sensors still need embedded miniaturized energy harvesting devices, since commercialized thin films and microbatteries do not provide sufficient power densities and suffer from limited lifetime. Therefore, micro‐supercapacitors are good candidates to store energy and deliver power pulses while providing non‐constant voltage output with time. However, multistep expensive protocols involving mask aligners and sophisticated cleanrooms are used to prepare these devices. Here, a simple and versatile laser‐writing procedure to integrate flexible micro‐supercapacitors and microbatteries on current‐collector‐free polyimide foils is reported, starting from commercial powders. Ruthenium oxide (RuO 2 )‐based micro‐supercapacitors are prepared by laser irradiation of a bilayered tetrachloroauric acid (HAuCl 4 · 3H 2 O)–cellulose acetate/RuO 2 film deposited by spin‐coating, which leads to adherent Au/RuO 2 electrodes with a unique pillar morphology. The as‐prepared microdevices deliver 27 mF cm −2 /540 F cm −3 in 1 m H 2 SO 4 and retain 80% of the initial capacitance after 10 000 cycles. This simple process is applied to make carbon‐based micro‐supercapacitors, as well as metal oxide based pseudocapacitors and battery electrodes, thus offering a straightforward solution to prepare low‐cost flexible microdevices at a large scale.

Abstract Layered ternary carbides and nitrides, also known as MAX phases, have attracted enormous attention for many applications, especially as precursors to produce 2D metal carbides and nitrides called MXenes. However, it is still challenging to tune and control the shape/morphology of MAX phase particles at the nanoscale, as they are typically manufactured as large grains using ceramic technology. Herein, nanostructured Ti‐Al‐C MAX phases with fine‐tuned morphology of nanofibers and nanoflakes are prepared by using 1D and 2D carbon precursors at a synthesis temperature of 900 °C. The nanostructured MAX phases are used as precursors to produce nanosized multilayered MXenes, with a considerably shorter etching time and a low reaction temperature. These nanosized MXenes exhibit good electrochemical lithium‐ion storage properties and a pseudocapacitive electrochemical signature. The obtained Ti 2 CT x MXene electrode can deliver delithiation capacity of 300 mAh g −1 at low rates and 100 mAh g −1 when the lithiation/delithiation cycle happens within 30 s. Availability of nanoscale MAX phases and MXene nanoflakes with small lateral size may open new opportunities for both classes of materials.

Bronze reacts with oxygen, humidity, and pollutants in the atmosphere so that a patina forms. Natural exposure to an outdoor atmosphere can be simulated and accelerated in order to achieve a patina that mimics outdoor ancient patina. In order to avoid the uncontrolled dissolving of either the natural or artificially formed patina, protection of the patina is needed.

Thermite multilayered films composed of alternating thin layers of metal/oxidizers have various uses in microelectromechanical systems (MEMS), microelectronics, and materials bonding applications. Recently, applied research especially on the microinitiator applications has engendered an urgent need to improve ignitability without changing the layering and reactant spacing that both affect the combustion characteristics. This work describes an innovative nanoengineering solution to reduce the energy barriers for mass transport, making it possible to substantially lower ignition energy of CuO/Al reactive multilayers without manipulating the fuel and oxide layers thickness. To that end, gold nanoparticles exhibiting high thermal diffusivity properties are in situ grown uniformly inside the first CuO layer to produce localized hot-spots and promote the Al + CuO reaction. The CuO/Al reactive films with embedded gold nanoparticles exhibit earlier and optimized reaction than standard ones. The effect of gold nanoparticles on the thermite ignition mechanisms and the detailed reaction pathways were characterized by a host of characterization techniques including microscopy, thermal analysis, spectroscopy, and X-ray diffractometry. Altogether, results show that the gold nanoparticles are seeding nodular defects with conical shapes provoking (under thermal stimulation) high stressed zones in the multilayer where the Al + CuO reaction is quickly triggered. The analysis of reaction products showed that the multilayers break the unreacted Al droplets early allowing them to burn into the environment. The results provide a behavioral baseline for future studies of interface engineering to tune internal stress-induced reaction in reactive thin films at large.

Abstract Light management is one of the main challenges to address when designing a sensor from a nanocrystal (NC) array. Indeed, the carrier diffusion length, limited by hopping mechanism, is much shorter than the absorption depth. Several types of resonators (plasmon, Bragg mirror, guided mode, Fabry–Perot cavity) have been proposed to reduce the volume where light is absorbed. All of them are inherently narrow bands, while imaging applications focus on broadband sensing. Here, an infrared sensor in the short and mid‐wave infrared (SWIR and MWIR) that combines three different photonic modes is proposed to achieve broadband enhancement of the light absorption. Moreover, it is shown that these three modes can be obtained from a simple structure where the NC film is coupled only to a grating and a top metallic layer. The obtained device achieves a high responsivity of >700 mA W –1 , a detectivity up to 2 × 10 10 Jones at 80 K, and a short response time of 11 µs.

This paper reports the synergetic effects of UV and visible light irradiation on the photocatalytic activity of well-defined nanostructures composed of TiO2 films and Au nanoparticles (NPs). New insights into electronic as well as chemical processes that drive water decomposition were obtained by varying the position of the NPs on top and at different depths inside the semiconductor film. This work highlights the synergetic effect of UV and visible light on the photocatalytic activity of all the Au-containing structures: hydrogen produced under UV + Vis light shows 100% enhancement compared to the net production obtained under either UV or visible light alone. The systems where Au NPs are embedded in TiO2 outperform the one where NPs are positioned on the surface, indicating that the water-splitting reaction occurs primarily on the TiO2 surface rather than on the metal. Photocurrent and photocatalytic activity measurements under UV (353–403 nm), visible (400–1100 nm), and UV + Vis (300–1100 nm) light revealed the synergetic contribution of UV and Vis light. Indeed, the plasmonic Au NPs create an intense oscillating electric field at the Au NPs/semiconductor interface (visible light contribution); this mechanism coupled with the Schottky barrier formation generates hot electrons resulting in a better photoexcited charge separation. In addition, contrary to what is generally assumed, charge injection by the plasmon from the metal into the semiconductor plays a marginal role in the hydrogen evolution reaction. Furthermore, this paper highlights the positive impact of the semiconductor crystallinity surrounding the metal particles to avoid the charge carrier recombination and the importance of a surface free of oxygen vacancies, whose presence can inhibit the water decomposition.

The whitening and opacifying agent titanium dioxide (TiO2) is used worldwide in various foodstuffs, toothpastes and pharmaceutical tablets. Its use as a food additive (E171 in EU) has raised concerns for human health. Although the buccal mucosa is the first area exposed, oral transmucosal passage of TiO2 particles has not been documented. Here we analyzed E171 particle translocation in vivo through the pig buccal mucosa and in vitro on human buccal TR146 cells, and the effects on proliferating and differentiated TR146 cells. In the buccal floor of pigs, isolated TiO2 particles and small aggregates were observed 30 min after sublingual deposition, and were recovered in the submandibular lymph nodes at 4 h. In TR146 cells, kinetic analyses showed high absorption capacities of TiO2 particles. The cytotoxicity, genotoxicity and oxidative stress were investigated in TR146 cells exposed to E171 in comparison with two TiO2 size standards of 115 and 21 nm in diameter. All TiO2 samples were reported cytotoxic in proliferating cells but not following differentiation. Genotoxicity and slight oxidative stress were reported for the E171 and 115 nm TiO2 particles. These data highlight the buccal mucosa as an absorption route for the systemic passage of food-grade TiO2 particles. The greater toxicity on proliferating cells suggest potential impairement of oral epithelium renewal. In conclusion, this study emphasizes that buccal exposure should be considered during toxicokinetic studies and for risk assessment of TiO2 in human when used as food additive, including in toothpastes and pharmaceutical formulations.

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44−, Ca2+, PO43−, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. A novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

In this study, we demonstrate the effect of change of the sputtering power and the deposition pressure on the ignition and the combustion properties of Al/CuO reactive thin films. A reduced sputtering power of Al along with the deposition carried out at a higher-pressure result in a high-quality thin film showing a 200% improvement in the burn rate and a 50% drop in the ignition energy. This highlights the direct implication of the change of the process parameters on the responsivity and the reactivity of the reactive film while maintaining the Al and CuO thin-film integrity both crystallographically and chemically. Atomically resolved structural and chemical analyzes enabled us to qualitatively determine how the microstructural differences at the interface (thickness, stress level, delamination at high temperatures and intermixing) facilitate the Al and O migrations and impact the overall nano-thermite reactivity. We found that the deposition of CuO under low pressure produces well-defined and similar Al-CuO and CuO-Al interfaces with the least expected intermixing. Our investigations also showed that the magnitude of residual stress induced during the deposition plays a decisive role in influencing the overall nano-thermite reactivity. Higher is the magnitude of the tensile residual stress induced, stronger is the presence of gaseous oxygen at the interface. By contrast, high compressive interfacial stress aids in preserving the Al atoms for the main reaction while not getting expended in the interface thickening. Overall, this analysis helped in understanding the effect of change of deposition conditions on the reactivity of Al/CuO nanolaminates and several handles that may be pulled to optimize the process better by means of physical engineering of the interfaces.

There is a miscibility gap in the CoFe₂O₄–Co₃O₄ phase diagram in which the oxides can be subjected to a spinodal transformation.

A variety of iodine-based one-dimensional (1-D) nanocrystals were introduced into double-wall carbon nanotubes (DWCNTs) using the molten phase method, as an intermediate step for ultimately obtaining encapsulated metal nanowires. Based on high-resolution transmission electron microscopy (HRTEM) observations using different imaging modes (bright field, dark field, and scanning TEM) and associated analytical tools (electron energy loss spectroscopy), it is revealed that the reality of nanotube filling is much more complex than expected. For some iodides (typically NiI 2), earlier decomposition during the filling step was observed, which could not be anticipated from the known data on the bulk material. Other filling materials (e.g., iodine) show a variety of atomic structuration inside and outside the CNTs, which is driven by the available space being filled. Most of the encapsulated structures were confirmed by modeling.

Carbonated Biomimetic Nanocrystalline Apatite (BNAc) coatings are obtained for the first time by Cold Spray. The coatings are characterized by FTIR, Raman, XRD, and SEM and compared to the powders. No significant chemical and structural changes are detected and the nanostructure features of these very reactive BNAc are preserved in the coating. These results and preliminary mechanical assays show that Cold Spray can produce an operational biomimetic coatings offering a high potential for implants functionalization and osseointegration. However, these first results need further studies in order to understand the mechanism of adhesion and the interactions at the coating–substrate interface.

Abstract The dream to produce green, clean, and sustainable hydrogen from earth‐abundant and free resources such as seawater and sunlight is highly motivating because of the interest for desirable economical and societal applications in energy. However, it remains challenging to develop an efficient and unassisted photocatalytic device to split seawater molecules with just sunlight without any external bias. For the first time, a such novel hierarchical material has been developed, based on thin film technology that integrates TiO 2 semiconductor layers, embedded gold nanoparticles, and a photosensitive carbo‐benzene layer. The design of the triptych device placing the photocatalyst in be‐to‐be increases the photoactive surface area by a factor 2. Its stability (>120 successive hours of hydrogen production and >5 days in a day/night representative alternation) and efficiency (Soler‐to‐Hydrogen 0.06%) are measured in NaCl‐salted water. The chloride ions act as hole scavengers and induce an increase of pH increasing in turn the sun‐driven hydrogen production rate.

Abstract Abundant silica-undersaturated potassic lavas are found in the centre of the Turkish–Iranian plateau (NW Iran) as flows, pillows and dykes. They display abundant zoned clinopyroxene macrocrysts and xenoliths of igneous cumulates. We determined four types of zoned crystals (Type-I, -II, -III and -IV) on the basis of their composition and zoning patterns. Use of in situ compositional data, together with whole-rock major and trace elements and the isotopic signatures of the host lavas provided evidence for the derivation of the different types of zoned clinopyroxenes from at least two contrasting parental melts. Our findings are consistent with an origin of the ultrapotassic and sodic alkaline melts from the deep-seated compaction pockets inferred from our previous studies of the alkaline magmatism throughout the Turkish–Iranian plateau. The ultrapotassic melt, which accumulated at the top of the compaction pockets, eventually ponded close to the spinel–garnet mantle transition and generated colourless antecrysts (Type-I and Type-II) and clinopyroxenite cumulates. When the compaction pocket impinged on the continental lithosphere, interstitial melts segregated and flowed inside dykes where grass green antecrysts (Type-III) and zoned phenocrysts (Type-IVa) crystallized from a melt having a geochemical signature of sodic alkaline melt. Later, at the crustal level, melt crystallization processes produced Type-IVb zoned phenocrysts. Our results are at odds with the paradigm of potassic magmas in NW Iran being derived strictly from a single mantle source.

AIMS: This study explored the lateral crest structures of adult cardiomyocytes (CMs) within healthy and diseased cardiac tissue. METHODS AND RESULTS: Using high-resolution electron and atomic force microscopy, we performed an exhaustive quantitative analysis of the three-dimensional (3D) structure of the CM lateral surface in different cardiac compartments from various mammalian species (mouse, rat, cow, and human) and determined the technical pitfalls that limit its observation. Although crests were observed in nearly all CMs from all heart compartments in all species, we showed that their heights, dictated by the subsarcolemmal mitochondria number, substantially differ between compartments from one species to another and tightly correlate with the sarcomere length. Differences in crest heights also exist between species; for example, the similar cardiac compartments in cows and humans exhibit higher crests than rodents. Unexpectedly, we found that lateral surface crests establish tight junctional contacts with crests from neighbouring CMs. Consistently, super-resolution SIM or STED-based immunofluorescence imaging of the cardiac tissue revealed intermittent claudin-5-claudin-5 interactions in trans via their extracellular part and crossing the basement membrane. Finally, we found a loss of crest structures and crest-crest contacts in diseased human CMs and in an experimental mouse model of left ventricle barometric overload. CONCLUSION: Overall, these results provide the first evidence for the existence of differential CM surface crests in the cardiac tissue as well as the existence of CM-CM direct physical contacts at their lateral face through crest-crest interactions. We propose a model in which this specific 3D organization of the CM lateral membrane ensures the myofibril/myofiber alignment and the overall cardiac tissue cohesion. A potential role in the control of sarcomere relaxation and of diastolic ventricular dysfunction is also discussed. Whether the loss of CM surface crests constitutes an initial and common event leading to the CM degeneration and the setting of heart failure will need further investigation.

The physico-chemical characteristics of particulate matter (PM) in African cities remain poorly known due to scarcity of observation networks. Magnetic parameters of PM are robust proxies for the emissions of Fe-bearing particles. This study reports the first magnetic investigation of PM2.5 (PM with aerodynamic size below 2.5 μm) in Africa performed on weekly PM2.5 filters collected in Abidjan (Ivory Coast) and Cotonou (Benin) between 2015 and 2017. The magnetic mineralogy is dominated by magnetite-like low coercivity minerals. Mass normalized SIRM are 1.65 × 10−2 A m2 kg−1 and 2.28 × 10−2 A m2 kg−1 for Abidjan and Cotonou respectively. Hard coercivity material (S-ratio = 0.96 and MDF = 33 mT) is observed during the dry dusty season. Wood burning emits less iron oxides by PM2.5 mass when compared to traffic sources. PM2.5 magnetic granulometry has a narrow range regardless of the site or season. The excellent correlation between the site-averaged element carbon concentrations and SIRM suggests that PM2.5 magnetic parameters are linked to primary particulate emission from combustion sources.

As part of a study on nucleation and growth of graphite in spheroidal graphite irons, systematic transmission electron microscopy observations are carried out. For this, focused ion beam is used to prepare thin foils that are precisely located and present an even thickness thus allowing high quality characterization. In this work, a nucleus with an overall elongated shape that was found in a perfectly round graphite spheroid is investigated by scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy. The acquisition of STEM images at different tilt of this nucleus is achieved which allows illustrating the precipitation process of the many phases constituting it. For the first time, a remaining of inoculant could be identified within the nucleus. Furthermore, the elongated shape of the nucleus is a definitive proof that the shape of nucleus does not determine that of the emerging graphite precipitate.

Topological insulators (TIs) are known as promising materials for new nanoelectronics and spintronics applications thanks to their unique physical properties. Among these TIs, bismuth antimony alloys (Bi1–xSbx) remain the most interesting because their electronic band structure can be controlled by changing the stoichiometry, the thickness, or the temperature. However, integrating these materials on an industrial substrate remains a challenge. Here, we investigate the growth, structural, and electrical properties of BiSb materials epitaxially deposited on industrial GaAs(001) substrates. We report the influence of key growth parameters such as temperature, antimony composition, thickness, and growth rate on the crystal quality. We manage to optimize the growth conditions while keeping the Bi1–xSbx composition within the TI range. Despite the large lattice mismatch and different crystalline matrices between the deposited material and the substrate, we successfully grow high-quality BiSb(0001) films. For optimized growth conditions, n-type semiconductor behavior of the BiSb layer is demonstrated at temperatures above 100 K. The material band gap calculated from our transport measurements corresponds to that mentioned in the literature. A change of the carrier type from bulk electrons to surface holes is observed when decreasing the temperature below 55 K. Hole mobilities up to 7620 cm2/(V·s) are extracted. This is, to our knowledge, the first demonstration of TI integrated on an industrial substrate keeping its protected surface states.

Recent results have demonstrated an exceptionally high permittivity in the range 200–330 K in crystalline titanium oxide Rb 2 Ti 2 O 5 . In this article, the possibility of a structural transition giving rise to ferroelectricity is carefully inspected. In particular, X-ray diffraction, high-resolution transmission electron microscopy and Raman spectroscopy are performed. The crystal structure is shown to remain invariant and centrosymmetric at all temperatures between 90 K and 450 K. The stability of the C 2/ m structure is confirmed by density functional theory calculations. These important findings allow the existence of a conventional ferroelectric phase transition to be ruled out as a possible mechanism for the colossal permittivity and polarization observed in this material.

Using localized surface plasmon resonance (LSPR) as an optical probe we demonstrate the presence of free carriers in phosphorus doped silicon nanocrystals (SiNCs) embedded in a silica matrix. In small SiNCs, with radius ranging from 2.6 to 5.5 nm, the infrared spectroscopy study coupled to numerical simulations allows us to determine the number of electrically active phosphorus atoms with a precision of a few atoms. We demonstrate that LSP resonances can be supported with only about 10 free electrons per nanocrystal, confirming theoretical predictions and probing the limit of the collective nature of plasmons. We reveal the appearance of an avoided crossing behavior linked to the hybridization between the localized surface plasmon in the doped nanocrystals and the silica matrix phonon modes. Finally, a careful analysis of the scattering time dependence versus carrier density in the small size regime allows us to detect the appearance of a new scattering process at high dopant concentration, which can be explained by P clustering inside the SiNCs.