V. Budavári

Multi-pulse laser-induced plasma spectroscopy using a single laser source and a compact spectrometer

A portable laser induced breakdown spectrometer (LIBS), built around a microscope using a Q-switched Nd:GGG laser releasing multiple pulses and a non-intensified fiber optic spectrometer, was used to investigate the signal improvement of emission data achievable by the multiple-pulse approach. LIBS experiments were carried out in air and using Al, Cu, Si and Zn metallic targets. It was found that the use of 7 laser pulses, separated by ca. 25 μs time intervals, enhance line emissions by a factor of 2.5 to 129 with respect to the single-pulse case, and also decrease the relative standard deviation of the signal based on five consecutive measurements to 2–5%. Time-resolved emission data and the observation of ablation craters suggest that the signal enhancement is mainly attributable to the reheating of the plasma by multiple laser pulses.

Noncovalently bonded quinone on self-assembled molecular layers

Aminoalkanethiol surface modifiers were investigated on gold electrodes. It was established, that quinone molecules could be attached to these surface layers in three different forms with well-distinguished redox potentials. Chemical reaction with the amino groups of the modifiers could produce monosubstituted and disubstituted quinones attached covalently to the layers. However, a third form could be detected, as well that seems to be quinone attached non-covalently to the monosubstituted quinone molecules.

Electrochemical hydrogenation of C60 fullerene films

Abstract Electrochemical reductions of C 60 fullerene films were studied in the presence of Bronsted acids to form hydrogenated fullerenes. It was established that a simple electrochemical treatment, reversible reduction and oxidation of the films formed such structurally rearranged layers that could be transformed to H n C 60 (where n depended on the acid, on the concentration of the acid and on the electrode potential). Hydrogenated fullerene films were shown to behave as semiconductors with very much increased photoefficiency.

Electrochemical behavior of C60 films in dimethylformamide + water mixtures

Abstract Reactions of C 60 fullerene films were studied in N , N -dimethylformamide+water mixtures in the presence of potassium ion as a dopant. The single step three-electron reduction in pure water as solvent could be separated to one-electron reduction processes, depending on the DMF content of the solutions. Under optimal conditions, one-electron reduction and re-oxidation was observed with K + ions. However, the processes are generally complex, and they involve various intermediates. These intermediates could be used as electrocatalysts for the reduction and for the oxidation of various compounds.

Formation and electrochemical behavior of self-assembled multilayers involving quinone

Surface modification of gold electrodes was carried out with various thioamine compound, and quinone binding was studied on these modified surfaces. It was established that depending on the chemical nature of the binder, covalently and noncovalently bonded quinone could be attached with well-distinguished electrochemical characteristic. The attached quinone layer could be reacted with various diamine compounds, and the amine group of the new terminating layer could be reacted again with quinone. In such a way we could form various multilayers of quinone with different binder and spacer between the electroactive units.