Victor Meza-Laguna

Solvent-free one-step covalent functionalization of graphene oxide and nanodiamond with amines

We attempted amide functionalization of the carboxylic groups present in graphene oxide (GO) and nanodiamond (ND) by means of a solvent-free gas-phase treatment with two aromatic amines 1-aminopyrene (AP) and 2-aminofluorene (AF), and also with one aliphatic amine, 1-octadecylamine (ODA), for comparison. The procedure was carried out under moderate vacuum, at temperatures of 150–180 °C, using short reaction times of about 2 h. The amine treatment generally gave rise to changes in Fourier-transform infrared (FTIR), Raman, ultraviolet-visible, and X-ray photoelectron spectra (XPS), to a variable degree depending on the particular sample. Thermogravimetric analysis showed the highest amine content for GO and ND treated with ODA, which turned out to be roughly one order of magnitude higher than in the case of aromatic AF and AP. Considerable changes in sample morphology after functionalization were observed by transmission electron and atomic force microscopy. Based on the analysis of FTIR and XPS spectra, we concluded that amidation is the only possible route for ND functionalization with AF, AP and ODA, whereas we found spectroscopic evidence for an alternative reaction channel on GO sheets, which is amine addition onto epoxy bridges.

Nanostructured Diamine−Fullerene Derivatives: Computational Density Functional Theory Study and Experimental Evidence for their Formation via Gas-Phase Functionalization

Nanostructure derivatives of fullerene C(60) are used in emerging applications of composite matrices, including protective and decorative coating, superadsorbent material, thin films, and lightweight high-strength fiber-reinforced materials, etc. In this study, quantum chemical calculations and experimental studies were performed to analyze the derivatives of diamine-fullerene prepared by the gas-phase solvent-free functionalization technique. In particular, the aliphatic 1,8-diamino-octane and the aromatic 1,5-diaminonaphthalene, which are diamines volatile in vacuum, were studied. We addressed two alternative mechanisms of the amination reaction via polyaddition and cross-linking of C(60) with diamines, using the pure GGA BLYP, PW91, and PBE functionals; further validation calculations were performed using the semiempirical dispersion GGA B97-D functional which contains parameters that have been specially adjusted by a more realistic view on dispersion contributions. In addition, we looked for experimental evidence for the covalent functionalization by using laser desorption/ionization time-of-flight mass spectrometry, thermogravimetric analysis, and atomic force microscopy.

Solvent-free derivatization of oxidized single-walled carbon nanotubes and nanodiamond with aminobenzo-crown ethers

ABSTRACT We report on a one-step amide derivatization of two carbon nanomaterials (CNM) containing carboxylic functional groups, which are oxidized single-walled carbon nanotubes (SWNTs) and nanodiamond (ND), with amino-substituted crown ethers, namely, 4′-aminobenzo-15-crown-5 and 4′-aminobenzo-18-crown-6. The functionalization procedure proposed is based on thermal activation of COOH groups instead of traditional chemical activation, is fast and facile, does not require the use of organic solvents and can be considered as ecologically friendly. The nanohybrids of crown ethers with SWNTs and ND were characterized by means of Fourier-transform infrared and Raman spectroscopy, scanning and transmission electron microscopy, as well as thermogravimetric analysis and solubility tests in toluene and propanol. The approach proposed allows for a facile preparation of crown ether-functionalized SWNTs and ND without contamination with other chemical reagents, solvents and detergents, which might be especially important for a broad spectrum of applications ranging from nanoelectronics to nanomedicine.

Effect of Thin C60 Films Modification with Aminosubstituted Polycyclic Aromatic Hydrocarbons and Meso-tetraphenylporphine on Optical and Photoelectric Properties of Au/C60/Si Photodiode Structures

We present the results of comparative investigations of the effect of a direct solvent-free modification of C60 thin films with photosensitive molecules: aminosubstituted polycyclic aromatic hydrocarbons (1-aminopyrene, 1-pyrenemethylamine hydrochloride, 1,5-diaminonaphthalene) and meso-tetraphenylporphine on their optical properties, photoluminescence, and photoelectric characteristics of Au/C60/Si photodiode structures (λ = 400–1100 nm). The optical properties (n, k) of the investigated C60 films are shown to differ slightly. The photoluminescence spectra measured at 2 K demonstrate a redistribution of the constituent bands intensities and their overall reduction for all C60 modifications. The greatest enhancement of the photocurrent and the photoconversion efficiency is observed for structures with C60 layers modified with meso-tetraphenylporphine.

One-step nondestructive functionalization of graphene oxide paper with amines

Direct functionalization of prefabricated free-standing graphene oxide paper (GOP) is the only approach suitable for systematic tuning of its mechanical, thermal and electronic characteristics. However, the traditional liquid-phase functionalization can compromise physical integrity of the paper-like material up to its total disintegration. In the present paper, we attempted to apply an alternative, solvent-free strategy for facile and nondestructive functionalization of GOP with 1-octadecylamine (ODA) and 1,12-diaminododecane (DAD) as representatives of aliphatic amines, and with 1-aminopyrene (AP) and 1,5-diaminonaphthalene (DAN) as examples of aromatic amines. The functionalization can be carried out under moderate heating at 150–180 °C for 2 h in vacuum, and proceeds through both amidation and epoxy ring opening reactions. Comparative characterization of pristine and amine-modified GOP samples was carried out by means of Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopy, thermogravimetric and differential thermal analysis, scanning electron and atomic force microscopy. In addition, we compared stability in water, wettability, electrical conductivity and elastic (Youngs) modulus of GOP samples before and after functionalization. The highest content of amine species was obtained in the case of GOP-ODA, followed by GOP-DAD, GOP-AP and GOP-DAN. The functionalization increased mechanical and thermal stability, as well as the electrical conductivity of GOP. The magnitude of each effect depends on the structure of amine employed, which allows for tuning a given GOP characteristic. Morphological characterization showed that, compared to pristine graphene oxide paper, amine-modified mats become relatively ordered layered structures, in which individual GO sheets are organized in a near-parallel fashion.

Carbon Nanotubes and Graphene Promote Pyrolysis of Free-Base Phthalocyanine

Unsubstituted phthalocyanines (including free-base H2Pc and many of its metal complexes) are among the most stable organic compounds. They can sublime without decomposition under reduced pressure and temperatures of up to 550 °C. This property was previously employed to design a novel approach to noncovalent functionalization of pristine single-walled carbon nanotubes (SWNTs) with 3d metal(II) phthalocyanine complexes. However, when we attempted to use the same sublimation protocol to prepare a SWNTs-H2Pc hybrid, an unexpected side effect of partial H2Pc pyrolysis was detected, phthalonitrile being a main decomposition product, under the conditions when H2Pc is supposed to be totally stable. By using density functional theory calculations, we offer an explanation for the thermal behavior of H2Pc based on its covalent attachment to the pentagonal-ring topological defects, which are very common in all graphene-derived carbon nanomaterials and capable of reacting with amines via nucleophilic addition process.