The combined use of the microcapillary cell (MEC) and scanning vibrating electrode technique (SVET) and low-angle cross sections was employed to elucidate the role of each coating region on the protection of the cut-edge corrosion of galvanized steels. Different compounds are involved in the blocking action of the corrosion products: Zincite (ZnO) on the steel substrate, hydrozincite (Zn5(OH)6(CO3)2) at the coating/steel interface, and Simonkolleite (Zn5(OH)8Cl2) and ZnO on the different coating regions in different proportions. The coating surface is also active at the initial stage and during long-term protection and thus, must be considered in experimental simulation of the cut-edge corrosion.
The use of chitosan functionalized silica for benznidazole delivery in the treatment of neglected disease such as Chagas disease is one of the forms not yet explored, but with great potential for this therapy, as little is known about nanoformulations for the treatment of Chagas disease. In this work, we used chitosan-succinate covalently attached to the surface pore of MSNs to act as anchor for benznidazole as a delivery system. The samples were characterized structurally and chemically with multiple techniques. The applicability of functionalized MSNs as platforms for benznidazole delivery into T. cruzi parasites was assessed. The results demonstrate that the proposed system is a potential promising nanoplatform for drug and gene delivery targeting neglected diseases such as Chagas disease.
Synthetic polymers are made up of repeated monomeric units, and this gives them a very versatile appearance, making them useful in many areas of science. One is the pharmaceutical, which correlates the properties of the polymer with the active principle, so they can be used as an excipient or in the controlled release system. The PMMA-g-PEG4000 has characteristics derived from its precursors, that are pharmacologically active. When we incorporate drugs into this structure, the polymer can act on the controlled release, lessening the toxic character of the drug and producing fewer side effects. In this work, incorporations of the drug indomethacin were made in the PMMA-g-PEG copolymer and derivatives (PMMA-g-PEG4000 ETIL and PMMA-g-PEG4000 ACET). The samples were characterized by infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), and atomic force microscopy (AFM) measurements. For each sample, the controlled release was performed in a total time of 4 h and the efficiency of the modified structures was verified.
Abstract Isoxazoles have well established biological activities but, have been underexplored as synthetic intermediates for applications in materials science. The aims of this work are to synthesis a novel isoxazole and analyze its structural and photophysical properties for application in electronic organic materials. The novel bis (phenylisoxazolyl) benzene compound was synthesized in four steps and characterized by NMR, high resolution mass spectrometry, differential thermal analysis, infrared spectroscopy, cyclic voltammetry, ultraviolet–visible spectroscopy, fluorescence spectroscopy, \DFT\ and \TDDFT\ calculations. The molecule presented optical absorption in the ultraviolet region (from 290 nm to 330 nm), with maximum absorption length centered at 306 nm. The molar extinction coefficients (ε), fluorescence emission spectra and quantum efficiencies in chloroform and dimethylformamide solution were determined. Cyclic voltammetry analysis was carried out for estimating the \HOMO\ energy level and these properties make it desirable material for photovoltaic device applications. Finally, the excited-state properties of present compound were calculated by time-dependent density functional theory (TDDFT).
In the present work, we use atomic force microscopy nanomanipulation of 2D-material standing folds to investigate their mechanical deformation. Using graphene, h-BN and talc nanoscale wrinkles as testbeds, universal force–strain pathways are clearly uncovered and well-accounted for by an analytical model. Such universality further enables the investigation of each fold bending stiffness κ as a function of its characteristic height h 0 . We observe a more than tenfold increase of κ as h 0 increases in the 10–100 nm range, with power-law behaviors of κ versus h 0 with exponents larger than unity for the three materials. This implies anomalous scaling of the mechanical responses of nano-objects made from these materials.
Abstract In this work, we demonstrate the nanofabrication of monolayer MoS2 islands using local anodic oxidation of few-layer and bulk MoS2 flakes. The nanofabricated islands present true monolayer Raman signal and photoluminescence intensity up to two orders of magnitude larger than that of a pristine monolayer. This technique is robust enough to result in monolayer islands without the need of
meticulously fine-tuning the oxidation process, thus providing a fast and reliable way of creating monolayer regions with enhanced optical properties and with controllable size, shape, and position.
Optical microscopy is one of the most important tool for understanding biology processes. Recently with the advance of femtosecond laser all the nonlinear optical processes have been included into optical microscopy methods and Second Harmonic Generation (SHG) microscopy has emerged as a powerful new optical imaging tool with applications in disease diagnostics \[1-2\]. The ``gold standard'' in cancer diagnostics is still the traditional histology analysis where accuracy depends on the experience and interpretation skill of the pathologist. A major development would be to use the SHG microscopy as a quantitative tool to cancer diagnosis. Here we show SHG imaging results of the collagen fibers in prostate cancer tissue that can be directly correlated with the cancer malignancy diagnostic \[3\]. We performed SHG imaging in a back-scattering geometry on the histological slides from the same biopsies that were analyzed by the pathologist. We studied prostate from patients treated at the the Urology Center of UFMG Hospital, Belo Horizonte. A 1 mm diameter punch biopsy was extracted from multiple peripheral zone of the prostate showing normal tissue and cancer tissue with Gleason scores ranging from 3 to 5. The study was approved by the UFMG Institutional Review Board and the Brazilian National Health Committee on the use of humans as experimental subjects. Written informed consent was obtained from all participants before their biopsy procedures. Figure 1 shows SHG images for normal and cancer tissue. The SHG images show major differences on the collagen fiber alignment that changes with cancer progression. The average direction of the fibers in the image was calculated and we obtained a value for the fiber anisotropy \[4\]. The statistical analysis is presented in the boxplot in figure 1. Note that both the average values (crosses) and the median lines (black center lines) are well separated for the normal and cancer tissue.
Despite the advanced stage of diamond thin-film technology, with applications ranging from superconductivity to biosensing, the realization of a stable and atomically thick two-dimensional diamond material, named here as diamondene, is still forthcoming. Adding to the outstanding properties of its bulk and thin-film counterparts, diamondene is predicted to be a ferromagnetic semiconductor with spin polarized bands. Here, we provide spectroscopic evidence for the formation of diamondene by performing Raman spectroscopy of double-layer graphene under high pressure. The results are explained in terms of a breakdown in the Kohn anomaly associated with the finite size of the remaining graphene sites surrounded by the diamondene matrix. Ab initio calculations and molecular dynamics simulations are employed to clarify the mechanism of diamondene formation, which requires two or more layers of graphene subjected to high pressures in the presence of specific chemical groups such as hydroxyl groups or hydrogens.
Abstract Molecular dynamics (MD) employing the Lennard-Jones (LJ) interaction potential was used to compute the heat capacities of argon at constant volume \CV\ and constant pressure \CP\ near the critical point very close to the asymptotic region. The accurate \MD\ calculation of critical divergences was shown to be related to a careful choice of the cutoff radius rc and the inclusion of long-range corrections in the \LJ\ potential. The computed \CP\ and \CV\ values have very good agreement as compared to available \NIST\ data. Furthermore, values of \CV\ in a range of temperatures for which \NIST\ data is not available could be computed. In the investigated range of temperatures, both \CP\ and \CV\ \MD\ results were fitted to a simple mathematical expression based on an empirical model that describes the critical effects when the asymptotic models are not appropriate. The present approach is of general applicability and robust to compute thermophysical properties of fluids in the near-critical region.
Dengue is the most prevalent arthropod-borne viral disease in the world. In this article we present results on the development, characterization and immunogenic evaluation of an alternative vaccine candidate against Dengue.
We report a first-principles study of edge-reconstructed, few-layered graphene nanoribbons. We find that the nanoribbon stability increases linearly with increasing width and decreases linearly with increasing number of layers (from three to six layers). Specifically, we find that a three-layer 1.3 nm wide ribbon is energetically more stable than the C60 fullerene, and that a 1.8 nm wide ribbon is more stable than a (10,0) carbon nanotube. The morphologies of the reconstructed edges are characterized by the presence of five-, six-, and sevenfold rings, with sp3 and sp2bonds at the reconstructed edges. The electronic structure of the few-layered nanoribbons with reconstructed edges can be metallic or semiconducting, with band gaps oscillating between 0 and 0.28 eV as a function of ribbon width.
In this work we have used atomically-resolved scanning tunneling microscopy and spectroscopy to study the interplay between the atomic and electronic structure of graphene formed on copper via chemical vapor deposition. Scanning tunneling microscopy directly revealed the epitaxial match between a single layer of graphene and the underlying copper substrate in different crystallographic orientations. Using scanning tunneling spectroscopy we have directly measured the electronic density of states of graphene layers near the Fermi level, observing the appearance of a series of peaks in specific cases. These features were analyzed in terms of substrate-induced perturbations in the structural and electronic properties of graphene by means of atomistic models supported by density functional theory calculations.