Solvothermal synthesis of lanthanide-functionalized graphene oxide nanocomposites

We propose a facile approach to the preparation of graphene oxide (GO) composites with lanthanide (Ln) oxide/hydroxide nanoparticles (Ln = La, Eu, Gd, Tb) under relatively mild conditions by two different procedures of solvothermal synthesis. The mechanism of GO-Ln nanocomposite formation is thought to involve the initial coordination of Ln3+ ions to the oxygen-containing groups of GO as nucleation sites, followed by f Ln2O3 and Ln(OH)3 nanoparticle growth. The nanocomposites obtained preserve the intrinsic planar honeycomb-like structures of graphene as proven by the typical G and D bands in the Raman spectra. Fourier-transform infrared and X-ray photoelectron spectroscopy confirm the interaction between oxygen-containing groups of GO and Ln ions. The size and distribution of Ln oxide/hydroxide nanoparticles on GO sheets, estimated from scanning and transmission electron microscopy images, vary broadly for the different lanthanides. The size can span from sub-nm dimensions for Eu oxide to more than 10 μm for Eu hydroxide nanoparticles. The most homogeneous distribution of Ln oxide/hydroxide nanoparticles was found in La-containing composites. Thermogravimetric analysis demonstrated that all the GO-Ln nanocomposites are thermally less stable, by up to 30 °C than pristine GO.</p

Eco-friendly synthesis of graphene oxide–palladium nanohybrids

Nanostructured hybrids of graphene oxide and palladium were fabricated by means of one-step solvent-free gas phase treatment of graphene oxide with the aliphatic amines 1-octadecylamine and 1,8-diaminooctane, followed by in situ decoration with palladium in the liquid medium using palladium chloride as the precursor and citric acid as a mild and environmentally friendly stabilizing and reducing agent. The proposed synthesis method represents an eco-friendly alternative for obtaining nanohybrids of graphene oxide and palladium nanoparticles under mild conditions. Spectroscopic studies evidenced -COOH group derivatization of graphene due to the amidation reaction; transmission electron microscopy demonstrated the formation of nanometer-sized crystalline palladium particles and evidenced that the diamine-functionalization results in a larger particle sizes than observed for monoamine- or non-functionalized substrates. The hybrids obtained have a slightly lower thermal stability than pristine graphene oxide.</p

Effect of chemical modification of thin C₆₀ fullerene films on the fundamental absorption edge

Fullerene C₆₀ films were grown using physical vapor deposition on Si substrates at room temperature. Then chemical modification with cross-linking these films was performed using the reaction with 1,8-octanediamine (DA) or octane-1,8- dithiol (DT). These chemically cross-linked C₆₀ films are capable of stable binding the Ag or Au nanoclusters. Optical properties of the obtained nanostructured hybrid films were investigated by both reflectance spectroscopy and spectral ellipsometry within the spectral range 1.55 to 5.0 eV at various angles of incidence. From the spectral dependences of the extinction coefficient in the region of optical absorption edge, the physical nature of the fundamental allowed direct band-gap transitions between HOMOLUMO states Eg, the optical absorption edge near the intrinsic transition Eo, and exponential tail of the density-of-states caused by defects have been determined. Influence of chemical modification and decoration of metal nanoparticles on the above mentioned parameters has been analyzed

Optical and photoluminescent properties of nanostructured hybrid films based on functional fullerenes and metal nanoparticles

The chemically cross-linked C₆₀ thin films, capable of binding Ag or Au nanoparticles, were prepared by the gas-phase treatment with diamine for one set of samples and dithiol for another one and decoration with Ag or Au nanoparticles, respectively. The optical and photoluminescent properties of the obtained nanostructured hybrid films in comparison with the undecorated films were studied. The low temperature photoluminescence (PL) spectra demonstrate significant changes of the band intensity and appearance of fine structure for bands connected with radiative transitions of self-trapped and localized excitons. The decoration of pristine and treated C₆₀ films with Ag nanoparticles leads to a decrease of PL intensity and to slight bandgap reduction. These phenomena can be explained by the increase of the surface recombination velocity at the fullerene-nanoparticle interface. At the same time, the nanoparticles insignificantly decrease the transmittance of light into the fullerene and Si layers, and have almost no influence on photoelectric properties of metal/fullerene/Si barrier structures

N-doped carbon nanofibers from pyrolysis of free-base phthalocyanine

Heating free-base phthalocyanine (H2Pc) at around 450 °C under static vacuum results in the formation of a nonvolatile carbonaceous material through oxidative pyrolysis. We used a number of instrumental techniques to characterize its morphology and chemical composition. According to electron microscopy observations, the dominating morphology is fibrous. The estimated length of individual fibers, which appear as rather homogeneous and continuous structures, is several micrometers, with diameters of roughly 200 nm. According to elemental analysis estimates, the per cent contribution of carbon remains approximately the same as in pristine H2Pc, but about 5.4 at% of nitrogen is substituted by oxygen. Spectroscopic measurements suggest that the oxygen is incorporated into nanofiber structure in the form of different functionalities containing C]O and C–OH bonds. Raman spectroscopy revealed an approximately equal contribution due to sp3 and sp2 -hybridized carbon atoms, which would made one to expect that the thermal stability of nanofibers must be similar to that of defect-containing nanotubes, graphene oxide and nanodiamond. Nevertheless, according to thermogravimetric curves obtained, nanofibers are at least as thermally stable as graphene and defect-free nanotubes. Density functional theory calculations were employed to suggest possible initial steps of H2Pc oxidative pyrolysis leading to the formation of nanofibers.Financial support from the National Autonomous University of Mexico (grant DGAPA-IN101118, FTIR and Raman spectroscopic measurements; DGAPA-IN203219, SEM and EDS characterization) and from the National Council of Science and Technology, Mexico (CONACYT, grant 250655) is greatly appreciated. L. M. B.-P. is grateful to the Doctorate Degree Program in Chemical Sciences of UNAM and to CONACyT for PhD scholarshi

Solvent-free covalent functionalization of multi-walled carbon nanotubes and nanodiamond with diamines: Looking for cross-linking effects

The covalent functionalization of carbon nanomaterials with diamines is a way to enhance the mechanical strength of nanocomposites due to cross-linking effects, to form complex networks for nanotube-based electronic circuits, as well as is important for a number of biomedical applications. The main goal of the present work was to covalently functionalize pristine multi-walled carbon nanotubes and nanodiamond with three aliphatic diamines (1,8-diaminooctane, 1,10-diaminodecane and 1,12-diaminododecane) and one aromatic diamine (1,5-diaminonaphthalene), by employing a simple one-step solvent-free methodology, which is based on thermal instead of chemical activation. We looked for experimental evidences of cross-linking effects in the carbon nanomaterials synthesized by using solubility/dispersibility tests, atomic force microscopy, scanning and transmission electron microscopy, as well as Fourier-transform infrared spectroscopy and thermogravimetric analysis for additional characterization

Solvent-free functionalization of carbon nanotube buckypaper with amines

none10sitWe demonstrate the possibility of fast and efficient solvent-free functionalization of buckypaper(BP) mats prefabricated from oxidized multiwalled carbon nanotubes (MWCNTs-ox), by using threerepresentative amines of different structure: one monofunctional aliphatic amine, octadecylamine(ODA), one monofunctional aromatic amine, 1-aminopyrene (AP), and one aromatic diamine, 1,5-diaminonaphthalene (DAN). The functionalization procedure, which relies on the formation of amidebonds with carboxylic groups of MWCNTs-ox, is performed at 150–180◦C under reduced pressure andtakes about 4 h including auxiliary degassing. The amine-treated BP samples (BP-ODA, BP-AP and BP-DAN, respectively) were characterized by means of a variety of analytical techniques such as Fourier-transforminfrared and Raman spectroscopy, thermogravimetric and differential thermal analysis, scanning andtransmission electron microscopy, scanning helium ion microscopy, and atomic force microscopy. Thehighest amine content was found for BP-ODA, and the lowest one was observed for BP-DAN, with a possi-ble contribution of non-covalently bonded amine molecules in all three cases. Despite of some differencesin spectral and morphological characteristics for amine-functionalized BP samples, they have in commona dramatically increased stability in water as compared to pristine BP and, on the other hand, a relativelyinvariable electrical conductivity.Basiuk, E.V.; Ramírez-Calera, I.J.; Meza-Laguna, V.; Abarca-Morales, E.; Pérez-Rey, L.A.; Re, M.; Prete, P.; Lovergine, N.; Álvarez-Zauco, E.; Basiuk, V.A.Basiuk, E. V.; Ramírez Calera, I. J.; Meza Laguna, V.; Abarca Morales, E.; Pérez Rey, L. A.; Re, M.; Prete, Paola; Lovergine, Nicola; Álvarez Zauco, E.; Basiuk, V. A