Browsing by Subject "Methanol"

Now showing 1 - 6 of 6

Open Access
Analysis of Fe nanoparticles using XPS measurements under d.c. or pulsed-voltage bias
(2010) Süzer, Şefik; Baer, D. R.; Engelhard, M. H.
The impact of solution exposure on the charging properties of oxide coatings on Fe metal-core oxide-shell nanoparticles has been examined by sample biasing during XPS measurements. The Fe nanoparticles were suspended in relatively unreactive acetone and analyzed after particles containing solutions were deposited on SiO2/Si or Au substrates. The particle and substrate combinations were subjected to ±10V d.c. or ±5V a.c., biasing in the form of square wave (SQW) pulses. The samples experienced variable degrees of charging for which low-energy electrons at ∼1eV, 20 μA and low-energy Ar+ ions were used to minimize it. Application of d.c. bias and/or SQW pulses significantly influences the extent of charging, which is utilized to gather additional analytical information about the sample under investigation. This approach allows separation of otherwise overlapping peaks. Accordingly, the O1s peaks of the silicon oxide substrate, the iron oxide nanoparticles, and that of the casting solvent can be separated from each other. Similarly, the C1s peak belonging to the solvent can be separated from that of the adventitious carbon. The charging shifts of the iron nanoparticles are strongly influenced by the solvent to which the particles were exposed. Hence, acetone exhibited the largest shift, water the smallest, and methanol in between. Dynamical measurements performed by application of the voltage stress in the form of SQW pulses provides information about the time constants of the processes involved, which leads us to postulate that these charging properties we probe in these systems stem mainly from ionic movement(s).
Open Access
The effect of cucurbit[n]uril on the solubility, morphology, and the photophysical properties of nonionic conjugated polymers in an aqueous medium
(2010) Tuncel, D.; Artar, M.; Hanay, S. B.
The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer, namely, poly[9,9-bis{6(N,N-dimethylamino) hexyl}fluorene-co-2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV-vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy.
Open Access
Electrical and chemical characterization of chemically passivated silicon surfaces
(IEEE, 2008) Chhabra, B.; Süzer, Şefik; Opila, R. L.; Honsberg, C. B.
The surface composition of chemically passivated silicon substrates is investigated using XPS and FTIR techniques. The samples are passivated with methanol, quinhydrone-methanol and iodine-methanol solution after HF treatment. The minority carrier lifetimes of these chemically passivated silicon substrates are also measured. Quinhydrone-methanol solution provides a chemically inert surface and a considerably longer minority carrier lifetime.
Open Access
Electrooxidation of methanol on doped polypyrrole films in acidic media
(Elsevier, 2001-04-06) Becerık, İ.; Süzer, S.; Kadirgan, F.
Electrooxidation of methanol was realised on platinum and perchlorate anion doped polypyrrole film electrodes in acidic media. A systematic kinetic investigation was performed and optimum experimental conditions for the preparation of the electrocatalytic system were determined. The presence of ClO4- anions was confirmed by XPS analysis of the doped polymer matrix. (C) 2001 Elsevier Science B.V. All rights reserved.
Open Access
Mesoporous metallic rhodium nanoparticles
(Nature Publishing Group, 2017) Jiang B.; Li C.; Dag, Ö.; Abe, H.; Takei, T.; Imai, T.; Hossain, M. S. A.; Islam, M. T.; Wood, K.; Henzie, J.; Yamauchi, Y.
Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ∼1/42.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O 2.
Open Access
NOx reduction on a transition metal-free γ-Al2O3 catalyst using dimethylether (DME)
(2008) Ozensoy, E.; Herling, D.; Szanyi, J.
NO2 and dimethylether (DME) adsorption as well as DME and NO2 co-adsorption on a transition metal-free γ-alumina catalyst were investigated via in-situ transmission Fourier transform infrared spectroscopy (in-situ FTIR), residual gas analysis (RGA) and temperature programmed desorption (TPD) techniques. NO2 adsorption at room temperature leads to the formation of surface nitrates and nitrites. DME adsorption on the alumina surface at 300 K leads to molecularly adsorbed DME, molecularly adsorbed methanol and surface methoxides. Upon heating the DME-exposed alumina to 500-600 K the surface is dominated by methoxide groups. At higher temperatures methoxide groups are converted into formates. At T > 510 K, formate decomposition takes place to form H2O(g) and CO(g). DME and NO2 co-adsorption at 423 K does not indicate a significant reaction between DME and NO2. However, in similar experiments at 573 K, fast reaction occurs and the methoxides present at 573 K before the NO2 adsorption are converted into formates, simultaneously with the formation of isocyanates. Under these conditions, NCO can further be hydrolyzed into isocyanic acid or ammonia with the help of water which is generated during the formate formation, decomposition and/or NCO formation steps. © 2008 Elsevier B.V. All rights reserved.