Influence of the gold nanoparticles electrodeposition method on Hg(II) trace electrochemical detection

Gold nanoparticles (AuNPs) were deposited on Glassy Carbon (GC) substrate by using three electrochemical techniques: Cyclic Voltammetry (CV), Chronoamperometry (CA) and Potentiostatic Double-Pulse (PDP). For each electrodeposition method, the resulting AuNPs-modified electrodes were characterized by CV in H2SO4 and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). CA was found to be the best electrodeposition mode for controlling the morphology and the density of AuNPs. The modified electrodes were used for low Hg(II) concentration detection using Square Wave Anodic Stripping Voltammetry (SWASV). AuNPs obtained by CA afforded the best amperometric response while involving the lowest amount of charge during the electrodeposition step (QAu(III)). This analytical response is correlated to both the smallest particle size (ca. 17 nm in diameter) and the highest particle density (332 particles μm−2), thus displaying high electrode effective surface area. In these optimal conditions, using a Hg(II) preconcentration time of 300 s, the nanosensor array exhibited a linearity range from 0.80 to 9.9 nM with a sensitivity of 1.16 μA nM−1. A detection limit of 0.40 nM (s/n = 3) was reached

PPH dendrimers grafted on silica nanoparticles: surface chemistry, characterization, silver colloids hosting and antibacterial activity

Polyphosphorhydrazone (PPH) dendrimers have been grafted on silica nanoparticles, and the surface functions of the dendrimers have been derivatized to phosphonates with lateral poly(ethyleneglycol) (PEG) chains. All materials have been thoroughly characterized by MAS NMR, FT-IR, electron microscopy, TGA and elemental analysis. These materials successfully hosted silver and silver oxide nanoparticles. The resulting composites exhibit antibacterial activity

Antischistosomal Activity of Trioxaquines: In Vivo Efficacy and Mechanism of Action on Schistosoma mansoni

Schistosomiasis is among the most neglected tropical diseases, since its mode of spreading tends to limit the contamination to people who are in contact with contaminated waters in endemic countries. Here we report the in vitro and in vivo anti-schistosomal activities of trioxaquines. These hybrid molecules are highly active on the larval forms of the worms and exhibit different modes of action, not only the alkylation of heme. The synergy observed with praziquantel on infected mice is in favor of the development of these trioxaquines as potential anti-schistosomal agents

Straightforward synthesis of gold nanoparticles by adding water to an engineered small dendrimer

International audienceA small water-soluble phosphorus-containing dendrimer was engineered for the complexation of gold(I) and for its reduction under mild conditions. Gold nanoparticles were obtained as colloidal suspensions simply and only when the powdered form of this dendrimer was dissolved in water, as shown by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analyses. The dendrimers acted simultaneously as mild reducers and as nanoreactors, favoring the self-assembly of gold atoms and promoting the growth and stabilization of isolated gold nanoparticles. Thus, an unprecedented method for the synthesis of colloidal suspensions of water-soluble gold nanoparticles was proposed in this work

Platinum N-heterocyclic carbene nanoparticles as new and effective catalysts for the selective hydrogenation of nitroaromatics

1867-3899In this communication, we report the first synthesis of Pt NPs stabilized with NHC ligands and their investigation as catalysts in the chemoselective hydrogenation of nitroarenes. The results in catalysis show that by a proper choice of the NHC stabilizer and the adjustment of the NHC/metal ratio, these NHC-capped Pt NPs exhibit high levels of activity and selectivity in the hydrogenation reactions. In particular, Pt NPs stabilized with 2 equiv. of IPr carbene (PtIPr0.2) catalyze the chemoselective reduction of a series of functionalized nitroarenes under mild conditions (1bar H2, 30°C). This catalyst tolerates the presence of a range of functional groups including hydroxyl, benzyloxy, carbonyl and olefinic moeities as well as halogens

Ligand-Capped Ru Nanoparticles as Efficient Electrocatalyst for the Hydrogen Evolution Reaction

Altres ajuts: UAB and "Euroregió Pirineus Mediterrànea" PhD grants ; Serra Húnter ProgramMultielectron reductions such as the hydrogen evolution reaction (HER) play an important role in the development of nowadays energy economy. Herein, the application of the organometallic approach as synthetic method allows obtaining very small, ligand-capped but also highly active ruthenium nanoparticles (RuNPs) for the HER in both acidic and basic media. When deposited onto glassy carbon, the catalytic activity of this nanomaterial in 1 M H2SO4 solution is highly dependent on the oxidation state of the NPs surface, with metallic Ru sites being clearly more active than RuO2 ones. In sharp contrast, in 1 M NaOH as electrolyte, the original Ru/RuO2 mixture is maintained even under reductive conditions. Estimation of surface active sites and electrochemically active surface area (ECSA) allowed benchmarking this catalytic system, confirming its leading performance among HER electrocatalysts reported at both acidic and basic pH. Thus, in 1 M NaOH condition, it displays lower overpotentials (η0 ≈ 0 mV, η10 = 25 mV) than those of commercial Pt/C and Ruthenium black (Rub), and also fairly outperforms them in short- and long-term stability tests. In 1 M H2SO4 solution, it clearly outdoes commercial Rub and is competitive or even superior to commercial Pt/C, working at very low overpotentials (η0 ≈ 0 mV, η10 = 20 mV) with a Tafel slope of 29 mV·dec-1, achieving TOFs as high as 17 s-1 at η = 100 mV and reaching a current density of |j| = 10 mA·cm-2 for at least 12 h without any sign of deactivation

Controlled Growth of Ag Nanocrystals in a H‐Bonded Open Framework

International audienceA procedure that enabled rational access to the first example of hybrid material made of NPs grown within a H-bonded framework is reported. To avoid competitive reactions with the framework units, the metal precursor was chemically trapped in the porous structure and subsequently photo-reduced to afford the hybrid material Ag@SPA-2, which consists of Ag NPs of nanometric sizes (<15 nm) homogeneously distributed in the crystals of the host material. In a subsequent step, taking advantage of the porous matrix the silver NPs have been transformed in situ to Ag2S NP by simple infiltration of H2S. The supramolecular network is shown to play an important role in stabilizing the inorganic nanomaterials and thus in controlling their growth

Synthesis of composite ruthenium-containing silica nanomaterials from amine-stabilized ruthenium nanoparticles as elemental bricks

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Fe doping effects on the structural, magnetic, and magnetocaloric properties of nano-sized Pr0.6Bi0.4Mn1−x FexO3 (0.1 ≤ x ≤ 0.3) manganites

International audienceThe structural, magnetic, and magentocaloric properties are systematically investigated for Pr0.6Bi0.4Mn1−x Fe x O3 (0.1 ≤ x ≤ 0.3) manganites. The samples have been synthesized by sol–gel method. X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy were employed to investigate the crystalline structure. Magnetization measurements were used to investigate the magnetic properties. All the samples crystallize in the orthorhombic Pnma space group as expected for manganite compounds. The presence of a PrMn2O5 compound is also evidenced by XRD. The average size of the manganite particles is about 50–60 nm. Particle characterizations at the atomic level turn to be of paramount importance. Magnetic measurements versus temperature under an applied magnetic field of 0.01 T show that all samples exhibit a paramagnetic–ferromagnetic transition. Temperature-dependent magnetization measurements and Arrott analysis reveal second-first order ferromagnetic transitions for (x = 0.1 and x = 0.2). The magnetic entropy change |ΔS M| was estimated using Maxwell relation method and is found to reach maximum values of 0.47 and 0.37 J/kg/K under an applied magnetic field of 5 T for x = 0.1 and x = 0.2, respectively

Self-Assembly of ZnO Nanoparticles - An NMR Spectroscopic Study

International audienceThe role of ligands (i.e. hexadecylamine, dodecylamine, or octylamine associated with oleic acid) on the formation of ZnO nanoparticle superlattice structures (NSSs) was investigated by NMR spectroscopy in C7D8. This full study demonstrates that ion‐paired ammonium carboxylates play a crucial role in NSS formation. Using different NMR spectroscopic experiments, such as 1H NMR, pulsed field gradient spin‐echo (PGSE) NMR, and NOESY, we evidenced that the introduction of long‐alkyl‐chain carboxylic acid molecules into a colloidal solution of ZnO nanoparticles (NPs) stabilized by amine ligands leads to rearrangement of the amines on the surface of the NPs with the formation of ammonium carboxylate. This NMR spectroscopic study evidences the dependence of the nature of the ligands adsorbed on the NP surface on the colloid concentration. At high concentration, several ligand shells with a lot of ion‐paired ammonium carboxylate and inclusion of amine are observed. At low concentration, the ion‐paired ammonium carboxylate shells are replaced by amine shells. This NMR spectroscopic study suggests that the driving force of NSS formation is the presence of ion‐paired ammonium carboxylate shells around the nanoparticle