Papers by Charles Pittman
Materials Science …, 2003
Page 1. Computational Modeling for the Development of CVD SiC Epitaxial Growth Processes. G. Meln... more Page 1. Computational Modeling for the Development of CVD SiC Epitaxial Growth Processes. G. Melnychuk 1, Y. Koshka 1 S. Yingquan 1, M. Mazzola 1, CU Pittman, Jr.2 1 Department of Electrical & Computer Engineering ...
Organodithiols with two distal thiols have been used extensively in gold and silver nanoparticle ... more Organodithiols with two distal thiols have been used extensively in gold and silver nanoparticle (AuNP and AgNP) applications. However, understanding the structures and conformations of organodithiols on these nanoparticles is challenging. Reported in this work is a combined surface enhanced Raman spectroscopy (SERS), transmission electron microscope (TEM), inductively coupled plasma mass-spectrometry (ICP-MS), and localized surface plasmonic resonance (LSPR) study of alkyldithiol (ADT, (HS-(CH 2) n-SH, n = 2, 4, and 6) interactions with AuNPs and AgNPs in water. These complementary techniques revealed a series of new insights that would not be possible using individual methods. A large-fraction of ADTs lies flat on AuNP surfaces. The upright ADTs are dimerized horizontally through disulfide-bond, or remain as monothiolates on the AuNP surfaces. The possibility of a significant amount of vertically disulfide-linked organodithiol on the surface is excluded on the basis of ICP-MS and AuNP LSPR experiments. ADTs induced significant AgNP disintegrations in which ADTs are predominantly in dithiolate forms. This work highlights the extraordinary complexity of organodithiol interactions with plasmonic nanoparticles. The insights provided in this work will be important for enhancing fundamental understanding of the structure and properties of organothiol-functionalized AgNPs and AuNPs.
Carbon, 1999
Three series of porous carbon fibers were prepared by electrochemical oxidation of a synthetic po... more Three series of porous carbon fibers were prepared by electrochemical oxidation of a synthetic polyacrylonitrilebased fiber to various degrees. The electrooxidized fibers were characterized by N 2 adsorption at 77 K, CO 2 adsorption at 273 K, NaOH neutralization and X-ray photoelectron spectroscopy ( XPS). In all cases standard BET surface areas calculated from nitrogen adsorption data barely exceeded the geometric area of the fiber itself (ca 1 m2 g−1). In contrast, surface areas derived by applying the Dubinin-Radushkevich (DR) method to CO 2 adsorption data increased fairly linearly from ca 1 to 132 m2 g−1 with increasing electrooxidation severity. NaOH uptakes were also found to increase linearly as a function of electrooxidation severity. It is thus inferred that: (1) N 2 adsorption at 77 K is severely hindered because of activated N 2 diffusion effects; and (2) by virtue of their thinner dimension and faster diffusion rate at 273 K, CO 2 molecules manage to probe the entire pore structure of the carbon fibers. Therefore, a new model based on density functional theory (DFT ) was applied to CO 2 adsorption data at 273 K in order to generate true pore size distributions (PSDs) of the fibers tested. The DFT/CO 2 method revealed that the PSDs of the electrooxidized fibers are neither Gaussian nor monomodal. Comparison with steam activated synthetic and natural plant ( Kenaf ) fibers revealed that ultramicroporous fibers possess PSD peaks at ca 0.4, 0.6, 0.8 and 1.1 nm. The peak at ca 0.4 was dominant and negligible when the DR/CO 2 to BET/N 2 surface area ratios were >1 and <1, respectively. It is therefore concluded that pores of ca 0.4 nm width are responsible for activated N 2 diffusion at 77 K.
Bioresource Technology, 2014
Journal of the Chemical Society, Chemical Communications, 1975
Tetrahedron Letters, 1967
Macromolecules Containing Metal and Metal-Like Elements, 2004
Journal of the American Chemical Society
Journal of the American Chemical Society
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Journal of the American Chemical Society
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Journal of Polymer Science Part A-1 Polymer Chemistry
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Journal of the Chemical Society D Chemical Communications
Journal of the American Chemical Society
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Papers by Charles Pittman