González Santiago, Miguel A.
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Publication Restricted Biomedical applications of nanotechnology : exploratory research on the use of one dimensional nanostructures(2016) González Santiago, Miguel A.; Castro Rosario, Miguel E.; College of Arts and Sciences - Sciences; Vega Olivencia, Carmen A.; López Garriga, Juan; Juan García, Eduardo J.; Department of Chemistry; Castillo, PaulStudies related to the use of nanoscaled materials in biomedical science and engineering research is at the forefront of research in medicine. Applied research in nanotechnology, particularly as related to medicine, is central to advance new technologies to improve our quality of life. Applied research usually identifies a specific need and is followed by applied research in a laboratory setting. The success of the applied research to treat a condition usually dictates further experiments related to toxicology and animals before the nanotechnology is explored in humans. This dissertation summarizes the results of exploratory research at the laboratory scale on the effect of one dimensional nanostructures as a tool to (1) prevent rupture of aneurysms and (2) facilitate neuron growth and communication. One dimensional silver nanostructures (Ag 1d) are assembled from the reaction of silver nitrate with mercapto acetic acid and water. Dry deposits of the dispersion results in the formation of nanofibers with an optical absorption spectrum similar to the one reported for Ag nanowires in the literature. We found that Ag 1d nanostructures formed on blood vessels ex situ increase their resistance toward deformation. We estimate an elastic modulus between 1 and 3 x 103 N/m2 and 0.15 x 103 N/m2 for the blood vessels modified with the silver nanofibers and control, respectively. We also investigated the effect of Ag1d nanostructures in the growth and development of Rat Embryonic Dorsal Root Ganglion (ReDRG) cells cultures. We found that ReDRG growth and proliferation on control and Ag 1D nanostructures is similar. The Ag 1d reduced the attachment of Schwann cells to the neuron cell bodies and axons as compared to the control.Publication Restricted X-ray photoelectron spectroscopy (XPS) study of Hexahydro-1,3,5-Trinitro-S-Triazine (RDX)(2007) González Santiago, Miguel A.; Castro Rosario, Miguel E.; College of Arts and Sciences - Sciences; Mina Camilde, Nairmen; Hernández Rivera, Samuel P.; Department of Chemistry; Estévez De Vidts, Luis A.Energetic materials are used as explosives component of landmines, plastic explosives (C-4), and home made bombs, among others. Hexahydro-1,3,5-trinitro-s-triazine (RDX) is a secondary explosive, which is the main component of C-4. Structural studies of solid RDX have established the existence of two forms known as α−RDX and a less stable and less understood β−RDX. The structural conformation of α-RDX has a Cs symmetry in which two of its nitro groups are in an axial orientation while the third one is oriented equatorially. The β−RDX solid form has a C3v symmetry, which results from an all-axial or all-equatorial orientation of its three nitro groups. The ring breathing Raman frequency is centered at 882 and 878 cm-1 in α− and β−RDX, respectively. This work reports X-ray photoelectron spectroscopy (XPS) measurements on RDX deposits on a silicon surface as a substrate. Deposits from RDX/acetone solution on a silicon substrate were prepared and allowed to evaporate to open air at room temperature. XPS measurements performed on these deposits revealed a broad N 1s band between 403.4 and 405.8 eV for deposits that consist of small amounts of RDX while a second band at 410 eV was observed in deposits that had large amounts of RDX. The 403 eV and 410 eV N 1s peaks were associated with aliphatic or ring nitrogen atoms and the nitrogen atom in the nitro group of RDX, respectively. In an attempt to assign these bands to either β− or α−RDX, vibrational spectroscopy measurements were performed on the deposits. The ring breathing mode frequency on the deposits was determined to be between 883 and 887 cm-1, a value that allowed ruling out the presence of β−RDX in the deposits. A third type of RDX is proposed to exist to account for the difference in the coverage dependent of the N 1s XP data.