Nanoparticelle d'oro supportate su silice funzionalizzata: Sintesi, caratterizzazione e catalisi.

Sono stati sintetizzati catalizzatori eterogenei di oro supportati su silice funzionalizzata. Le specifiche funzionalità condensate sulla superficie del supporto sono in grado di ridurre HAuCl4, producendo nanoparticelle d’oro metalliche sferiche e stabilizzate sulla superficie, senza l’aggiunta di agenti riducenti e stabilizzanti. I catalizzatori sono attivi per la reazione di riduzione del 4-nitrofenolo (4-NP) a 4-amminofenolo (4-AP)

Silica-Supported Gold Nanoparticles: Synthesis, Characterization and Reactivity

The main aim of this work was the synthesis and applications of functionalized-silica-supported gold nanoparticles. The silica-anchored functionalities employed, e.g. amine, alkynyl carbamate and sulfide moieties, possess a notable affinity with gold, so that they could be able to capture the gold precursor, to spontaneously reduce it (possibly at room temperature), and to stabilize the resulting gold nanoparticles. These new materials, potentially suitable for heterogeneous catalysis applications, could represent a breakthrough among the “green” synthesis of supported gold nanoparticles, since they would circumvent the addition of extra reducing agent and stabilizers, also allowing concomitant absorption of the active catalyst particles on the support immediately after spontaneous formation of gold nanoparticles. In chapter 4 of this thesis is also presented the work developed during a seven-months Marco Polo fellowship stay at the University of Lille (France), regarding nanoparticles nucleation and growth inside a microfluidic system and the study of the corresponding mechanism by in situ XANES spectroscopy. Finally, studies regarding the reparation and reactivity of gold decorated nanodiamonds are also described. Various methods of characterization have been used, such as ultraviolet-visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), X-ray Fluorescence (XRF), Field Emission Gun Scanning Electron Microscopy (SEM-FEG), X-ray Photoionization (XPS), X ray Absorption Spectroscopy (XAS)

1,1’,1’’-(2’,4’-Dinitro-[1,1’-biphenyl]-2,4,6-triyl)tripiperidine

The compound 1,1’,1’’-(2’,4’-dinitro-[1,1’-biphenyl]-2,4,6-triyl)tripiperidine was synthesized by SEAr/SNAr reaction between 1-fluoro-2,4-dinitrobenzene and 1,3,5-tris(N-piperidinyl)benzene. The structure of the newly synthesized compound was elucidated based on 1H-NMR, 13C-NMR, ESI-MS, UV-Vis and IR spectroscopy

Novel synthesis of gold nanoparticles supported on functionalized silica

Recently, we presented stable silica-supported gold nanoparticles (AuNPs) suitable for catalysis, obtained by using as the only reactants a gold precursor, chloroauric acid (HAuCl4), and commercial polyethyleneimine-functionalized silica beads (SiO2-PEI), with the need for neither external reducing agents nor conventional stabilizing moieties. In this work we describe another convenient method to prepare silica-supported gold nanoparticles. The silica nanoparticles were synthetized, first, by co-condensation of tetraethoxysilane and an organo-silane alkyne-terminated (SiO2-Yne), and then post-functionalized by thiol/yne coupling with cysteamine (SiO2@Thio-Yne). By simply adding the obtained systems to an aqueous solution of HAuCl4 the spontaneous formation of AuNPs was observed in both cases and in very short times with diameters in the range of 10 to 20 nm. These new systems were fully-characterized by FT-IR, XPS spectroscopy, DLS , UV-Vis and TEM microscopy

Time-resolved characterization of the embryonic state formation of nuclei during gold nanoparticles synthesis in a microfluidic device

Gold nanoparticles (Au-NPs) are among the most intensely studied nanoscale materials. [1-2] The molecular mechanisms of Au-NPs formation remain unclear due first to the quantity of material analyzed (~mM), second to the relative short time scale for the nucleation and growth steps and third to the limited accessibility to in situ time-resolved characterization. To overcome those issues and regarding the experimental aspects, Synchrotron radiation related techniques are useful to characterize such rapid NPs formation. [3] In order to access to a direct in situ time-resolved characterization, we build and adapt a micro-fluidic system under continuous flow conditions, whereby we follow, via in situ XANES spectroscopy, the Au-NPS formation from a gold precursor (HAuCl4) with sodium citrate as reducing and stabilizer agent to final. The setup is constituted by two glass syringes, a syringe pump, and one tee-mixer for combining the reagents and a 1.5 m 7 200 \u3bcm internal diameter fused silica capillary as micro-reactor heated using a heating plate. By focusing the X-rays (analysis spot of 50*50 \ub5m), the reaction was followed by monitoring the gold LIII-edge XAS spectra at different locations along the micro-tube, temperature and flow rates. Thanks to this set up it is possible to convert a "time scale" reaction in a "length scale" reaction. We describe the embryonic state NPs formation by characterizing the oxidation state of gold, geometry modifications of the precursor and ligand substitutions. [1] M. C. Daniel, D. Astruc, Chem. Rev., 104 (2004) 293. [2] A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. Int. Ed., 45, (2006), 7896. [3] J. Polte, , T. T. Ahner, F. Delissen, , S. Sokolov, F. Emmerling, A. F.Th\ufcnemann, R. Kraehnert, J. Am. Chem. Soc, 132, (2010), 1296

SYNTHESIS OF GOLD NANOPARTICLES SUPPORTED ON FUNCTIONALIZED SILICA NANOPARTICLES

Gold nanoparticles (AuNPs) are among the most intensely studied nanoscale materials, finding numerous applications in several fields such as catalysis, biomedicine and microelectronics. [1] AuNPs can be synthesized by several chemical procedures reported in literature, where in general the Au(III) precursor is reduced by a reducing agent and the AuNPs formed stabilized by the use of a stabilizing agent. [2] Recently, we presented stable silica-supported gold nanoparticles suitable for catalysis, obtained by using as the only reactants a gold precursor, chloroauric acid (HAuCl4), and commercial polyethyleneimine-functionalized silica beads (SiO2-PEI), with the need for neither external reducing agents nor conventional stabilizing moieties. [3] In this work we describe another convenient method to prepare functionalized-silica nanoparticles able to reduce in situ HAuCl4 precursor. The silica nanoparticles were synthetized, first, by co-condensation of tetraethoxysilane and an organo-silane alkyne-terminated (PPTEOS) (SiO2-Yne) [4] and then post-functionalized by thiol/yne coupling with cysteamine, silica nanoparticles SiO2-Thio-Yne are obtained with sulphide and primary amine, known for their capability to stabilize gold nanoparticles. [5] . Scheme 1. Synthesis of alkyne-modified silica nanoparticles and subsequent thiol/yne coupling. By simply adding an aqueous solution of HAuCl4 to SiO2-Yne (d 77 \ub1 10 nm) or to SiO2-Thio-Yne we achieved in both case AuNPs anchored on the silica surface. These systems were fully-characterized by FT-IR, XPS spectroscopy, DLS ,UV-Vis, TOF-SIMS and TEM microscopy

Electron reduction processes of nitrothiophenes. A systematic approach by DFT computations, cyclic voltammetry and E-ESR spectroscopy

none7noIn the framework of the interest in nitrothiophenes as drugs or hits with different pharmacological applications and considering that in several instances nitroreduction is an essential step for their biological activity, we have studied a complete series of mono-, di-, and tri-nitrothiophenes (1–6) and by comparison some mononitro benzo[b]thiophenes and benzo[b]furans (7–10). Their electroreduction behaviour has been investigated by different techniques: DFT calculations, cyclic voltammetry and electrochemical electron spin resonance spectroscopy. Although, the first reduction process for all of the compounds leads to the relevant radical anions, both the computational and experimental results indicate that there are significant differences in the fate of their corresponding forthcoming reductions, for example, formation of secondary radicals (open-shell electronic structures) or dianions. The effect of the relative positions of the nitro groups during the reduction has also been analysed and rationalised.noneC. Boga; M. Calvaresi; P. Franchi; M. Lucarini; S. Fazzini; D. Spinelli; D. TonelliC. Boga; M. Calvaresi; P. Franchi; M. Lucarini; S. Fazzini; D. Spinelli; D. Tonell

Novel synthesis of gold nanoparticles supported on functionalized silica

Recently, we presented stable silica-supported gold nanoparticles (AuNPs) suitable for catalysis, obtained by using as the only reactants a gold precursor, chloroauric acid (HAuCl4), and commercial polyethyleneimine-functionalized silica beads (SiO2-PEI), with the need for neither external reducing agents nor conventional stabilizing moieties. [1] In this work we describe another convenient method to prepare silica-supported gold nanoparticles. The silica nanoparticles were synthetized, first, by co-condensation of tetraethoxysilane and an organo-silane alkyne-terminated (SiO2-Yne), [2] and then post-functionalized by thiol/yne coupling with cysteamine (SiO2@Thio-Yne). By simply adding the obtained systems to an aqueous solution of HAuCl4 the spontaneous formation of AuNPs was observed in both cases and in very short times with diameters in the range of 10 to 20 nm. These new systems were fully-characterized by FT-IR, XPS spectroscopy, DLS , UV-Vis and TEM microscopy

Mild fabrication of silica-silver nanocomposites as active platforms for environmental remediation

Herein we report a new, simple, low cost and one step way to obtain silica-supported silver nanoparticles (AgNPs) on commercial polyethyleneimine-functionalized silica beads (SiO2-PEI) under mild experimental conditions. The novel AgNPs/(SiO2-PEI) material has been thoroughly analyzed using FE-SEM, BET, XRD, XPS and XE-AES analysis. The reduction of Methylene Blue (MB) to Leuco Methylene Blue (LMB) in the presence of NaBH4 was chosen for testing the catalytic properties of AgNPs/(SiO2-PEI) towards dyes decoloration. Moreover, the prepared supported nanocatalyst was also found to exhibit excellent catalytic activity towards decoloration of some azo dyes such as E110 and E122