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Plasmonic Cu nanoparticles were in-situ grown into a Cu$_2$O semiconductor matrix by using reactive magnetron sputtering and adjusting the amount of oxygen available during the synthesis in order to prevent the oxidation of part of copper atoms landed on the film surface. Varying only the oxygen flowrate (OFR) and using a single Cu target it was possible to observe the evolution in the simultaneous formation of metallic Cu and Cu$_2$O phases for oxygen-poor conditions. Suchformation is accompanied by the development of the surface plasmon band (SPB) corresponding to Cu, as evidenced by UV-Vis spectrophotometry and spectroscopic ellipsometry. The bandgap values of the elaborated composites containing embedded Cu plasmonic nanodomains were lower than the bandgap of single-phased Cu$_2$O films, likely due to the higher defect density associated to the nanocrystalline nature of films, promoted by the presence of metallic Cu. The resistivity of the thin films increased with more oxidative deposition conditions and was associated to an increase in Cu$_2$O/Cu ratio and smaller and more isolated Cu particles, as evidenced by high resolution transmission electron microscopy and X-ray diffraction. Photoconversion devices based on the studied nanocomposites were characterized by I-V and spectral photocurrent measurements, showing an increase in the photocurrent density under light illumination as consequence of the plasmonic particles excitation leading to hot carrier's injection in the nearby ZnO and Cu$_2$O semiconductors., Comment: ACS Applied Electronic Materials, American Chemical Society, 2022

Designing and manufacturing multifunctional nanoparticles (NPs) are of considerable interest for both academic and industrial research. Among NPs used in this field, iron oxide NPs show low toxicity compared to metallic ones and are thus of high interest for biomedical applications. In this work, superparamagnetic Fe3−δO4-based core/shell NPs were successfully prepared and characterized by the combination of different techniques, and their physical properties were investigated. We demonstrate the efficiency of the layer-by-layer process to graft polyelectrolytes on the surface of iron oxide NPs. The influence of the polyelectrolyte chain configuration on the magnetic properties of the Fe3−δO4/polymer core/shell NPs was enlightened. The simple and fast process described in this work is efficient for the grafting of polyelectrolytes from surfaces, and thus, derived Fe3−δO4 NPs display both the physical properties of the core and of the macromolecular shell. Finally, the cytotoxicity toward the human THP-1 monocytic cell line of the core/shell NPs was assessed. The results showed that the polymer-capped Fe3−δO4 NPs exhibited almost no toxicity after 24 h of exposure at concentrations up to 25 μg mL–1. Our results show that these smart superparamagnetic nanocarriers with stealth properties are promising for applications in multimodal cancer therapy, including drug delivery.

A new ternary phase with a composition Al1+xV2Sn2–x (x = 0.19) has been found during investigation of the Al–V–Sn ternary system. Single-crystal X-ray diffraction measurements reveal that this ternary phase crystallizes with an orthorhombic structure with a = 5.5931(1) A, b = 18.8017(5) A, and c = 6.7005(2) A (space group Cmce). This compound is thus isostructural to the GaV2Sn2 structure type, showing a layered structure composed of vanadium cluster bands formed with pentagonal faces intercalated by Sn atom layers. High-resolution transmission electron microscopy measurements confirm the orthorhombic structure. Regarding lattice perfection, no dislocation could be identified within the probed Al1.19V2Sn1.81 single-crystal lamella. Ab initio calculations reveal a reduction of the density of states at the Fermi level, which could be attributed to both a Hume–Rothery effect combined with strong spd hybridization.

International audience; Nanocomposite films consisting of gold nanoparticles embedded in zinc oxide (ZnO-Au) have been synthesized with different gold loadings by reactive magnetron sputtering at near-room temperature followed by ex situ annealing in air up to 300 °C. Using X-ray diffraction and high resolution transmission microscopy it is shown that during deposition gold substitutes zinc in ZnO as isolated atoms and in nanoparticles still exhibiting the structure of ZnO. Both situations degrade the crystalline quality of the ZnO matrix, but thermal annealing cures it from isolated gold atoms and triggers the formation of gold nanoparticles of size higher than 3 nm, sufficient to observe a strong activation of localized surface plasmon resonance (LSPR). The amplitude of LSPR absorption observed after annealing increases with the gold loading and annealing temperature. Moreover, UV and visible photoluminescence from the ZnO matrix is strongly enhanced upon activation of LSPR showing strong coupling with the gold nanoparticles. Finally, modeling of spectroscopic ellipsometry measurements unambiguously reveals how curing the defects increases the optical bandgap of the ZnO matrix and modifies the optical dielectric functions of the nanocomposite and ZnO matrix.

International audience; The electro-assisted self-assembly (EASA) of tetraethoxysilane (TEOS) and cetyltrimethylammonium bromide (CTABr) in hydro-alcoholic medium is now recognized to be a versatile method to generate highly ordered mesoporous silica films with unique orientation of mesopore channels normal to the underlying surface. In this work, we have evaluated the possibility to extend the method to aqueous media (i.e., without adding a cosolvent) and to determine the parameters affecting the EASA process and the resulting organization/orientation of the mesoporous framework by using electron microscopies and diffraction techniques. Contrary to water/cosolvent-based sols, the nature of the surfactant and supporting electrolyte counteranions (X-) was found to induce drastic variations on both the morphology and the mesostructural order of the deposits formed by electrochemically induced gelification (by pH increase) of CTAX/NaX-based silica sols. These changes are triggered by different surfactant assemblies arising from lower critical micellar concentration when passing from hydro-alcoholic to aqueous medium, and they are affected by the chaotropic-cosmotropic character of the counteranions. To be brief, cosmotropic anions (such as SO42-) promote the formation of thin films but suffering from poor or no ordering, whereas weakly bonded anions (such as Cl-) favor the mesostructuration but mainly in the form of particles or aggregates, while chaotropic anions (such as Br-) lead to rather thick deposits made of poorly organized aggregates. Mixing these anions, to get mixed micelles, enables compromises to be reached between these ``extreme'' behaviors and mesostructured thin films can be indeed obtained with the CTACl/Na2SO4 and CTABr/Na2SO4 media, exhibiting, respectively, some vertical or horizontal orientation of mesopore channels. This can be rationalized by taking into account the CTA(+), X- binding strength variations (Cl- < SO42- < Br-), thus affecting competitive binding of negatively charged silicate species, and sphere-to-rod transition abilities (SO42- approximate to Cl- < Br-) of the CTA(+)-based templates. Cyclic voltammetry was also used to characterize mass transport processes through the films. Finally, a preliminary work aiming at getting swelled pores of such electrogenerated films with mesitylene was carried out to evaluate the potential interest of the water-based EASA process for the entrapment of hydrophobic molecules inside the surfactant-silica phases.

International audience; Carbon nanotubes (CNTs) are difficult to process, and their assembly in macroscopic materials that allow us to benefit from the exceptional properties of the nanotubes is of crucial interest for applications. The developed CNT processing procedures usually involve additives that remain in the final product and are known to diminish the properties of the CNT-based material. Here, we propose a multistep approach to process single-walled carbon nanotubes (SWNTs) and obtain macroscopic additive-free SWNT materials. High-quality dispersion purified SWNTs is first induced in polar solvent due to their preceding reduction reaction with an alkali metal. The partial debundling process occurring at this stage leads to ramified SWNTs. They can then be self-assembled by attractive intermolecular forces through a controlled destabilization of the dispersions by a simple oxidation. Swollen gels of SWNTs are formed at an air/solvent interface. After freeze-drying, the additive-free SWNT material shows a hierarchical structure with highly interconnected SWNTs. Thanks to the obtained ramification of the SWNTs, these latter are able to well entangle what guarantees the robustness of the obtained additive-free SWNT material. Moreover, this integrated process offers an increase of the accessible surface compared to that of the raw bundled SWNTs. The obtained assembled SWNTs show an improved adsorption capacity.

International audience; Thermal dry oxidation treatment is a straightforward and commonly used technique in carbon nanotube (CNT) processing. Among its advantages, it plays a key role in guaranteeing the efficiency of numerous purification procedures. It also enables a chemical modification of the nanotube surface by covalent bonding of oxygen-containing functions. Nevertheless, a careful optimization of the experimental conditions used for the treatment is a crucial step in order to obtain the desired effect and avoid a strong damaging of the CNTs. Soft oxidation conditions are thus in particular of great interest. We report on the oxidation of CNTs in a large scale of oxidation conditions. The treated samples were characterized using several techniques including transmission electron microscopy, thermal gravimetric analysis, dispersion tests, and Raman spectroscopy to investigate both morphological and surface properties. We were thus able to discriminate between the behavior of the CNTs from that of other carbonaceous species. The problem of the selectivity of the oxidation treatment is especially discussed.

New quantum dots (QDs) were fabricated with a core/shell/shell structure consisting of CdTe core/CdS shell/ZnO shell. Despite the high lattice mismatch between CdS and ZnO, a ZnO shell was successf...

The description and understanding of the intercalation mechanism of electron donors or acceptors in single-walled carbon nanotube (SWNT) bundles are of critical interest for optimization and improvement of transport properties for future applications of SWNTs in electronics or energy storage. Here, we propose a novel approach based on the analysis of the state of debundling for SWNT bundles, used as a feedback for occupation sites of alkali metal atoms within the SWNT host material. Heterogeneity of the structure might be the origin of the complexity of the intercalation process in SWNTs.

Takovites are nickel-based layered double hydroxides (LDH) with a general formula that can be written as Ni(1-x)Al(x)(OH)2, A(z-)(x/z), yH(2)O, where A is a compensating interlayer anion. As in some other LDH samples, the positive charge of the layer can be adjusted upon synthesis and various anions can be exchanged in the interlayer region. It is then important to understand the synthesis pathway of these materials. We then undertook a study on the hydrolytic behavior of pure Ni salts and mixtures of Ni and Ga salts. This paper focuses on the hydrolysis of Ni(2+) and Ga(3+) ions, together in solution, carried out by base addition. The samples will be defined by their hydrolysis ratio R = [OH(-)]/([Ni(2+)] + [Ga(3+)]). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used to obtain information on the colloidal species size and shape on a large scale. Each hydrolyzed sample was also studied by Ni K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS) to obtain information on the local structure of the species in suspension. SAXS curves reveal the presence of bidimensional objects whatever the R values. The platelets formed for R values/=1.1 are slightly thicker and smaller in size, which may be linked to their different natures. Complementary information is provided by TEM analysis: the first colloids formed have a structure very close to that of alpha-GaOOH, as shown by electronic diffraction. Those structures are progressively replaced by Ni-Ga LDH platelets with increasing hydrolysis ratio, which are the only species in suspension for R = 2.0, as shown by XRD. EXAFS results confirm the complete hydrolysis of gallium before the formation of Ni-Ga LDH phases.

Takovites are nickel-based layered double hydroxides (LDHs) with a general formula that can be written as Ni1-xAlx(OH)2, Az-x/z, yH2O, where A is a compensating interlayer anion. As in some other LDH samples, the positive charge of the layer can be adjusted upon synthesis and various anions can be exchanged in the interlayer region. It is then important to understand the synthesis pathway of these materials. We then undertook a study on the hydrolytic behavior of pure Ni salts and mixtures of Ni and Ga salts. This paper focuses only on the hydrolysis of Ni2+ ions carried out by base addition. The samples will be defined by their hydrolysis ratio R = [OH-]/[Ni2+]. For all R values, colloids are observed in the final suspensions. Each hydrolyzed sample was studied by Ni K-edge extended X-ray absorption fine structure (EXAFS) to obtain information on the local structure of the colloids. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) are also used to obtain concomitant informat...

To reach a better understanding of the behavior of suspensions of charged colloidal platelets, takovite samples with a general formula Ni1-x, Alx(OH)2, Anz-x/z, yH2O, where An is an interlayer anion, were synthesized. These materials belong to the family of layered double hydroxides (also referred to as anionic clays). They can be easily prepared in the laboratory by coprecipitating mixed nickel and aluminum salts by NaOH. Their charge can be adjusted by changing the synthesis conditions, while the hydration properties can be modified by using various interlayer anions. On the basis of oscillatory measurements, rheological phase diagrams were obtained by plotting the sol−gel transition as a function of solid content and ionic strength for three monovalent anions: F-, Cl-, and NO3-. In all cases, the phase diagrams exhibit a negative slope, i.e., the sol−gel transition shifts toward lower solid contents for increasing ionic strength. The nature of the interlayer anion has a strong influence, the sol−gel l...

Hydrotalcite compounds have been successfully prepared by successive infiltrations into the interstices of an ordered array of polystyrene spheres, subsequently removed by either dissolution or the...