RESUMO
Carbon nanofibers (CNFs) have been incorporated into poly(methyl methacrylate) (PMMA) through electrospinning. The resulting micro- and nanofibers have been characterized by Scanning Electron Microscopy (SEM), which confirmed fiber formation and demonstrated a core-sheath structure of the PMMA fibers. Thermogravimetric Analysis (TGA) was used to obtain the thermal properties of the materials, indicating an enhancement in the thermal properties of the composite fibers. In addition, Fourier Transform Infrared Spectroscopy (FTIR) was utilized to investigate the interactions of PMMA micro- and nanofibers with CNFs, demonstrating the preferred sites of intermolecular interactions between the polymer matrix and the filler.
RESUMO
We present ion mass spectra obtained by matrix-assisted laser desorption/ionization for analytes of approximately 1000 Da across the largest range of wavelengths and pulse durations to date. The matrix used in all cases was 2,5-dihydroxybenzoic acid. Based on the data and fundamentals of laser-material interactions, we evaluated the plausibility of discriminating among such ion formation mechanisms as multiphoton ionization and excited-state ionization from mass spectra alone. Some previously proposed mechanisms appear unlikely for the matrix-analyte systems that we studied, casting doubt on their general applicability. Moreover, although analysis of mass spectra can apparently exclude certain mechanisms, it cannot establish which of several competing mechanisms is actually operative. This is particularly true with respect to variations in pulse duration and wavelength.
