Polymer-Grafted Silicon Nanoparticles Obtained Either via Peptide Bonding or Click Chemistry

International audiencePegylated silicon nanoparticles (SiNPs) are of great interest for applications in bio-imaging as fluorescent tracers. Poly(ethylene glycol) (PEG) covalently attached to SiNPs may improve the (bio)compatibility, solubility in water and stability of SiNPs, without inhibiting their optical properties. SiNPs are first coated with silica followed by a silanization of the surface. Then, two versatile "grafting to" methods are used to provide pegylated SiNPs. Both peptide type coupling and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) are conducted and compared to graft PEG of different chain lengths. Infra-red spectroscopy, thermogravimetric analysis and transmission electron microscopy prove that theses methodologies are simple and efficient for the preparation of functional inorganic nanoparticles with luminescent properties

CeO2 Nanocrystals from Supercritical Alcohols: New Opportunities for Versatile Functionalizations?

The fast and controlled synthesis of surface-modified cerium oxide nanoparticles was carried out in supercritical {ethanol + alcohol derivative} mixtures. The newly found ability of supercritical alcohols to graft onto cerium oxide nanocrystals (CeO2 NCs) during their synthesis was exploited to control their surface chemistry via the addition of three aminoalcohols: ethanolamine, 3-amino-1-propanol and 6-amino-1-hexanol. Although the ethanol to aminoalcohol ratio was consistent (285:1), the successful grafting of these alcohol derivatives onto CeO2 NCs was identified based on Fourier transform infrared (FTIR) and thermogravimetric analysis-mass spectrometry (TGA-MS) measurements. Smaller crystallite size of CeO2 NCs synthesized in the presence of aminoalcohols, compared to those synthesized in supercritical ethanol alone, were also noticed and attributed to a possible intervention of amine groups helping the grafting of the alcohols, allowing one to stop the growth of the CeO2 NCs faster. The use of supercritical alcohol mixture-ethanol with hexanol, dodecanol, or octadecanol, with a 285:1 ratio-was also investigated. Such mixtures allow accessing a finer control in CeO2 NCs crystallite size compared to pure alcohols, according to calculation made from X-ray diffraction measurements. Finally, fluorescent molecules (fluorescein isothiocyanate) were grafted onto amine-modified CeO2 NCs. The powders displayed a fluorescent behavior under UV light, confirming the suitability and interest of CeO2 NCs surface modification by such technique

Highly Reactive Pd NCs by Versatile Continuous Supercritical Fluids Synthesis for the Preparation of Metal–Nonmetal Pd-Based NCs

International audienceNanostructured palladium is of huge importance for a large range of applications, especially in the field of catalysis. Therefore, the development of synthetic procedures to gain control over palladium physicochemical properties is of paramount importance. Lately, the attention has been focused on combining Pd with other elements, even metal or nonmetal, because of enhanced or new properties arising from synergetic effects, diversity in composition, structures, along with others. Of interest for catalysis, nanoscaled materials made of Pd and a nonmetal part such as C, P, B, or N are envisioned. In the present work, we present the possibility of nonmetal (C or H) atom incorporation into the Pd lattice under ambient conditions as the subsequent step to nucleation and growth of highly reactive crude palladium nanocrystals in supercritical fluids. The as-modified Pd NCs present different physicochemical properties, allowing us to envision the possibilities of other materials preparation, for example, phosphides or borides, by this chemical colloidal approach

Hydrogen-Enriched Reduced Graphene Oxide with Enhanced Electrochemical Performance in Lithium Ion Batteries

Hydrogen-enriched reduced graphene oxide (RGO) was achieved using double-oxidized graphene oxide (GO(2)) as an anode in high-performance lithium batteries is reported. GO(2) exhibited a much lower carbon-to-oxygen ratio, lower crystallinity, higher Brunauer-Emmett-Teller surface area, higher pore volume, and higher porosity as compared to graphene oxides produced using the typical modified Hummers method (GO(1)). The two forms of GO were reduced using two different reduction methods: supercritical isopropanol (scIPA) and heat treatment. The four types of RGOs synthesized using GO(1)/GO(2) and scIPA/heat treatment exhibited significantly different chemical, morphological, and textural properties. The galvanostatic charge-discharge properties were highly dependent on the physicochemical properties of the RGOs. The scIPA-reduced GO(2) exhibited superior electrochemical performance as compared to the thermally reduced GO(1)/GO(2) and scIPA-reduced GO(1). Highly reversible capacity (1331 mAh g(-1) at 50 mA g(-1) after 100 cycles), excellent rate-performance (328 mAh g(-1) at 5 A g(-1)), and good cycling stability up to 1000 cycles even at a current density of 10 A g(-1) were observed with the scIPA-reduced GO(2) electrode. The characterization results suggested that a large amount of hydrogen-terminated groups, numerous defect sites, and large interlayer spacing have beneficial effects on the electrochemical performance of scIPA-reduced GO(2).close2