A theoretical model supported by experimental results explains the dependence of the Raman scattering signal on the evolution of structural parameters along the amorphization trajectory of polycrystalline graphene systems.Four parameters rule the scattering efficiencies, two structural and two related to the scattering dynamics. With the crystallite sizes previously defined from X-ray diffraction and microscopy experiments, the three other parameters (the average grain boundaries width, the phonon coherence length, and the electron coherence length) are extracted from the Raman data with the geometrical model proposed here. The broadly used intensity ratio between

Abstract:The aim of this study was to prepare a novel targeting drug delivery system for 2-Methoxyestradiol (2ME) in order to improve the clinical application of this antitumor drug. It is based in nanoparticles (NPs) of titanium dioxide (TiO 2 ) coated with polyethylene glycol (PEG) and loaded with 2ME. A complete IR and Raman characterization have been made to confirm the formation of TiO 2 -PEG-2ME composite. Vibrational modes have been assigned for TiO 2 , PEG, and 2ME and functionalized TiO 2 -PEG and TiO 2 -PEG-2ME. The observed variation in peak position of FTIR and Raman of each for these composites has been elucidated in terms of intermolecular interactions between PEG-2ME and TiO 2 , obtaining step-by-step the modification processes that were attributed to the conjugation of PEG and 2ME to TiO 2 NPs. Modifying TiO 2 NPs with PEG loaded with the 2ME drug revealed that the titanium dioxide nanocarrier possesses an effective adsorption capability, and we discuss their potential application as a system of drug delivery.

Understanding biological interaction with graphene and hexagonal-boron nitride (h-BN) membranes has become essential for the incorporation of these unique materials in contact with living organisms. Previous reports show contradictions regarding the bacterial interaction with graphene sheets on metals. Here, we present a comprehensive study of the interaction of bacteria with copper substrates coated with single-layer graphene and h-BN. Our results demonstrate that such graphitic coatings substantially suppress interaction between bacteria and underlying Cu substrates, acting as an effective barrier to prevent physical contact. Bacteria do not "feel" the strong antibacterial effect of Cu, and the substrate does not suffer biocorrosion due to bacteria contact. Effectiveness of these systems as barriers can be understood in terms of graphene and h-BN impermeability to transfer Cu(2+) ions, even when graphene and h-BN domain boundary defects are present. Our results seem to indicate that as-grown graphene and h-BN films could successfully protect metals, preventing their corrosion in biological and medical applications.

This study shows the results obtained when binding alkyl ferrocene molecules on silicon surface forming incomplete monolayers. The electrodic surface functionalization is carried out by a two step procedure: First, a hydrosilytation reaction between a Si-H surface and an alkenyl bromide active by white light; and then, the reaction of this surface with a monolithio ferrocene solution. Alkenyl bromide with different numbers of carbon atoms (3, 5 and 10 carbon atoms) were employed in order to obtain propyl, pentyl and decyl ferrocene chains on the electrodic surface. The samples of modified silicon were analyzed by X-ray photoelectron spectroscopy (XPS) and electrochemical measurements confirming the presence of ferrocene molecules on the electrode surface. The results obtained show that in each and every case, there were incomplete monolayers on the silicon surface, ranging from 16% to 42 %, depending on the alkenyl bromide employed in the synthesis. AC voltammetry was employed to determine the kinetic of the electron transfer between ferrocene molecules and the silicon electrode. However, the rate constant is not influenced by the length of the alkyl chain, and is usually constant (2.01 s-1-3.66 s-1). The result above is due to the electron transfer process which is determine by electron hopping in a regime of bonded diffusion and not by a long-rate electron transfer such as in a full compact monolayer.