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Semiconducting heterostructures are considered promising candidates for meeting specific environmental challenges, such as greener or decarbonated production of energy. However, optimizing the performance of these hybrid systems largely depends on the fine understanding of the mechanisms by which they are formed in relation to their mode of preparation. We report herein the synthesis of nanosized semiconducting heterostructures of ZnS@ZnO shell-core nature; this is from well-controlled preformed ZnO nanoparticles (NPs) modified via anion exchange process using (TMS)2S. The formation of these ZnS@ZnO heterostructures has been investigated in depth, shedding light specifically on the sulfidation mechanism and its dynamics. Our study reveals the dynamic evolution of the nanomaterial in the sulfidation process, evidencing that it is both driven by the initial presence of oxygen vacancies─acting as gateways for sulfur atoms─and also by the action in the medium of (TMS)2S, which as a sulfurizing agent behaves also as an oxygen atom extractor. The structural modification of the preformed monocrystalline ZnO nanomaterial into a polycrystalline ZnS hollow nanostructure occurs via amorphization–crystallization steps, which clearly depends on the amount of (TMS)2S in the reaction. This morphological transition to a hollow structure has been followed by multinuclear NMR spectroscopy (1H, 13C, 17O), and notably oxygen atoms at the interfaces of ZnS@ZnO heterostructures have been identified and quantified. Consistently, our study clearly establishes the link between the preparation mode of the ZnS@ZnO heterostructures and the modification of their optical band gaps as a function of their composition. The variation in optical properties, and the bowing of the band gap, depends on the sulfidation level, and this mode of sulfidation is clarified step-by-step by a DFT computational approach of surface and interface processes that is fully supported by the experimental characterization (XRD, WAXS, EDX line-analysis, HRTEM, STEM-HAADF) of these materials.

Herein, we report the successful characterization of sulfur vacancies in ZnS nanoplatelets by in-depth high-field and DNP-enhanced solid-state NMR of 33S and 67Zn nuclei and DFT modeling. This two-dimensional 1 nm-thick nanomaterial was obtained by reacting a dicyclohexyl zinc complex, ZnCy2, with (TMS)2S as the S source under mild conditions (45 °C) in dodecylamine. The joint experimental and theoretical studies on these nanoplatelets evidenced that a large fraction of the Zn and S atoms are located near the surface covered by dodecylamine and that the deviation from stoichiometry (agreeing with energy gap and photoluminescence properties of non-stoichiometric material) is due to sulfur vacancies. Additionally, this work reports the first 33S DNP-NMR spectrum reported in the literature alongside several ultra-high-field 33S and 67Zn solid-state NMR spectra.

Maternal exposure to particulate air pollution during pregnancy has been linked to multiple adverse birth outcomes causing burden of disease later in the child's life. To date, there is a paucity of data on whether or not ambient particles can both reach and cross the human placenta to exert direct effects on fetal organ systems during gestation.

Epigenetic reprogramming during perinatal germ cell development is essential for genomic imprinting and cell differentiation; however, the actors of this key event and their dynamics are poorly understood in rats. Our study aimed to characterize the expression patterns of epigenetic modifiers and the changes in histone modifications in rat gonocytes at the time of de novo DNA methylation. Using transgenic rats expressing Green Fluorescent Protein (GFP) specifically in germ cells, we purified male gonocytes by fluorescent activated cell sorting at various stages of perinatal development and established the transcriptomic profile of 165 epigenetic regulators. Using immunofluorescence on gonad sections, we tracked six histone modifications in rat male and female perinatal germ cells over time, including methylation of histone H3 on lysines 27, 9, and 4; ubiquitination of histone H2A on lysine119; and acetylation of histone H2B on lysine 20. The results revealed the dynamics in the expression of ten-eleven translocation enzymes and DNA methyltransferases in male gonocytes at the time of de novo DNA methylation. Moreover, our transcriptomic data indicate a decrease in histone ubiquitination and methylation coinciding with the beginning of de novo DNA methylation. Decreases in H2AK119Ub and H3K27me3 were further confirmed by immunofluorescence in the male germ cells but were not consistent for all H3 methylation sites examined. Together, our data highlighted transient chromatin remodeling involving histone modifications during de novo DNA methylation. Further studies addressing how these dynamic changes in histone posttranslational modifications could guide de novo DNA methylation will help explain the complex establishment of the male germ cell epigenome.De novo DNA methylation in rat gonocytes is associated with a transient modulation of the transcription of epigenetic modifiers involved in DNA methylation and histone posttranslational modifications, indicating a dynamic chromatin remodeling.

Direct methane oxidation into oxygen-containing chemicals under mild conditions has sparked increasing interest. Here, we report Pd@Pt core–shell nanoparticles that efficiently catalyse the direct oxidation of CH4to CH3OH in water using H2O2as an oxidant under mild conditions. The catalyst presents a methanol productivity of up to 89.3 mol kgcatalyst−1h−1with a high selectivity of 92.4% after 30 min at 50 °C, thus outperforming most of the previously reported catalysts. Electron-enriched Pt species in the Pd@Pt nanoparticles were identified by structural and electronic analysis. Pd in the core donates electrons to Pt, leading to higher rates of methane activation. Based on the results of control experiments and kinetic analysis, a consecutive oxidation pathway viaa radical mechanism is proposed, which includes initial formation of CH3OOH and CH3OH followed by further oxidation of CH3OH to HCHO, HCOOH, and CO2.

The synthesis of metal nanoparticle (NP) assemblies stabilized by functional molecules is an important research topic in nanoscience, and the ability to control interparticle distances and positions in NP assemblies is one of the major challenges in designing and understanding functional nanostructures. Here, two series of functionalized adamantanes, bis-adamantanes, and diamantanes, bearing carboxylic acid or amine functional groups, were used as building blocks to produce, via a straightforward method, networks of ruthenium NPs. Both the nature of the ligand and the Ru/ligand ratio affect the interparticle distance in the assemblies. The use of 1,3-adamantanedicarboxylic acid allows the synthesis of three-dimensional (3D) networks of 1.7–1.9 nm Ru NPs presenting an interparticle distance of 2.5–2.7 nm. The surface interaction between Ru NPs and the ligands was investigated spectroscopically using a 13C-labeled ligand, as well as theoretically with density functional theory (DFT) calculations. We found that Ru species formed during the NP assembly are able to partially decarbonylate carboxylic acid ligands at room temperature. Decarbonylation of a carboxylic acid at room temperature in the presence of dihydrogen usually occurs on catalysts at much higher temperatures and pressures. This result reveals a very high reactivity of ruthenium species formed during the network assembly. The Ru NP networks were found to be active catalysts for the selective hydrogenation of phenylacetylene, reaching good selectivity toward styrene. Overall, we demonstrated that catalyst activity, selectivity, and NP network stability are significantly affected by Ru NP interparticle distance and electronic ligand effects. As such, these materials constitute a unique set that should allow a better understanding of the complex surface chemistry in carbon-supported metal catalysts.

The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (–Me, –OMe, –Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.

Among the inorganic compounds, many oxides and sulfides are known to be semiconductors. At the crossroads of these two families, oxysulfide MxOySzcompounds were much less investigated because they are scarce in nature and complex to synthesize. Among them, lanthanide oxysulfide Ln2O2S (Ln = lanthanide) are indirect band gap semiconductors, with wide gaps, except for Ce2O2S. (Gd,Ce)2O2S anisotropic nanoparticles with a hexagonal structure were obtained over the whole composition range and exhibit colors varying from white to brown with increasing Ce concentration. Band gap engineering is thus possible, from 4.7 eV for Gd2O2S to 2.1 eV for Gd0.6Ce1.4O2S, while the structure is preserved with a slight lattice expansion. Surprisingly, because of the limited thickness of the lamellar nanoparticles, the band gap of the nanoparticles is direct as validated by density functional theory on slabs. The fine control of the band gap over a wide range, solely triggered by the cation ratio, is rarely described in the literature and is highly promising for further development of this class of compounds. We propose a multiregime mechanism to rationalize the band gap engineering over the whole composition range. This should inspire the design of other bimetallic nanoscaled compounds, in particular, in the field of visible light photocatalysis.

Europium-doped gadolinium carbonates particles have been prepared via urea-assisted precipitation. The reaction has been followed step by step with the investigations of the precipitate by transmission electron microscopy and wide-angle X-ray scattering, in relation with infrared absorption and thermal analyses. It has been observed that spherical particles of (Gd0.95Eu0.05)(OH)CO3, monodispersed in size and amorphous, precipitate first and then transform to agglomerated platelike crystals of (Gd0.95Eu0.05)2(CO3)3·2H2O as the precipitation continues. The Eu3+5D0→ 7FJemission spectrum and the 5D0lifetime in the two carbonate matrices have been measured. Selected hydroxycarbonate nanoparticles (NPs), with diameters of 164 ± 20 nm, have been then transformed to oxide NPs having the cubic crystalline structure C-(Gd0.95Eu0.05)2O3, with the same shape and size. The photoluminescence (PL) properties of hydroxycarbonate and oxide NPs, and of their colloidal suspensions in water, have been investigated. The hydroxycarbonate and the oxide NPs exhibit same PL intensities when excitation is achieved in one of the Eu3+(4f6) levels. Tests of in vitro fluorescence imaging have been performed. The luminescent NPs have been observed after their internalization by human cervical carcinoma (HeLa) cells. It is concluded that the controlled (urea-assisted) precipitation is appropriate to synthesize Gd(OH)CO3:Eu3+and Gd2O3:Eu3+nanoparticles having adequate characteristics for biolabeling.