Knowledge of the chemical structure of young soot and its precursors is very useful in the understanding of the paths leading to soot particle inception. This paper presents analyses of the chemical functional groups, based on FT-IR and 1 H NMR spectroscopy of the products obtained in an ethylene inverse diffusion flame. The trends in the data indicate that the soluble fraction of the soot becomes progressively more aromatic and less aliphatic as the height above the burner increases. Results from 1 H NMR spectra of the chloroform-soluble soot samples taken at different heights above the burner corroborate the infrared results based on proton chemical shifts (Ha, Hα, Hβ, and Hγ ). The results indicate that the aliphatic β and γ hydrogens suffered the most drastic reduction, while the aromatic character increased considerably with height, particularly in the first half of the flame.

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The effect of the oxidation degree of multiwalled carbon nanotubes (MWCNTs) for the detection of NADH was evaluated in this paper. MWCNTs were oxidized by microwave‐assisted sulfonitic treatment at different times (5, 10, 15, and 30 min) and deposited onto a graphite screen printed electrodes. Oxidized MWCNTs were characterized and the electrochemical performance evaluated. The best sensor in terms of sensitivity and stability was obtained after 15 minutes of oxidation (SPE/CNT15). A significant reduction of the NADH oxidation potential was recorded for oxidized MWCNTs compared with unmodified MWCNTs (0.270 V and 0.500 V, respectively vs. Ag/AgCl pseudo reference electrode), increasing the selectivity of the system. Chronoamperometric calibration curves carried out applying a potential of 0.3 V for 1 min were linear in the 4–35 μM range of NADH. A limit of detection of 1 μM was achieved with negligible surface fouling (three consecutive calibration curves, 30 total measurements: slope decrease 5.9 %). Inter electrode reproducibility (n=13) was good resulting in RSD of 15.2 % and 5.0 % for the peak intensity and the oxidation potential, respectively. Quantification of glucose in white wine samples was carried out to demonstrate the ability of the NADH sensor to work in real samples. A good correlation with a spectrophotometric kit for the glucose quantification was achieved.

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