Zeitaufgelöste Untersuchung der Kinetik, Intermediate und Mechanismen der Reaktionen zwischen Nanomaterialien und reaktiven Spezies
Zusammenfassung der Projektergebnisse
The scope of this project was the investigation of reactions between carbon based and inorganic (metal oxides) nanomaterials and reactive intermediates. A particular focus was set revealing the kinetic and mechanistic aspects of such reactions and shed light on formed intermediates. In the light of the two frameworks inorganic and carbon based nanomaterials we focused on TiO2 nanotubes and ZnO nanorods as inorganic nanomaterial and in particular on graphene oxide (GO) as carbon based nanomaterial. The latter work on carbon based nanomaterial was flanked by some exploratory studies on nanodiamonds and carbon nanoparticles. Turning to the work on inorganic nanomaterials, the studies on TiO2 nanotubes was performed with the purpose to investigate the exciton properties depending on the fabrication conditions of the rods. The investigations on ZnO nanorods were performed with the scope to test the electron injection into the ZnO conduction band as it is of interest for many applications such as solar-light harvesting devices etc. These investigations were performed in an interwoven photochemical and radiation chemical study testing the electron transfer from free base porphyrin to ZnO nanorods as well as investigating the reactions of solvated electrons with ZnO nanorods. Initial work on carbon based nanomaterial was performed with the thrust to understand the reduction of GO by the reaction with reducing transients. In an interlaced radiation chemical, photochemical and theoretical study we investigated the reduction of graphene oxide by strong reducing transients such as, solvated electrons (eaq-) hydrogen radicals (•H), CO2•-, hydroxy-2-propyl radicals ((CH3)2•COH) and ethoxy radicals (CH3•CHOH). The reduction utilizing free radicals turn out as a very appealing approach since it is rather simple to conduct, the GO flake was not getting contaminated with non-volatile chemicals and surprisingly high conductivity values were obtained for the reduced graphene oxide (rGO). The latter finding was a strong indication that not only the oxygen functionalities were removed from the GO carbon framework but also a substantial “repair” of the sp2-carbon lattice must have taken place. In order to understand this finding we conducted a combined spectroscopic and kinetic study based on pulse radiolysis flanked by quantum chemical calculations. As a result of our study, it turned out, that the mechanism dependent on the particular free radical. As an example, our theoretical studies showed, that •H showed three feasible reaction pathways leading in a multistep reaction to rGO: Electron transfer, radical addition and concerted water elimination. For CO2•- we found out, that only electron transfer and concerted HCO3- elimination are energetically feasible affording rGO and for (CH3)2•COH only the concerted water elimination is energetically feasible. These results explained the different transient absorption spectra obtained for the time resolved investigations which were identified as the intermediates H-GO•, GO•- and GO• formed by •H addition, electron transfer and concerted elimination reactions. Finally we conducted studies testing the feasibility to apply free radicals as an approach to surface-modify nanodiamonds and carbon nanoparticles. As an example our preliminary work indicate that •CCl3 reacts with nanodiamonds forming a radical adduct which is a perspective key for further surface modification and functionalization of nanodiamonds, which is intended to become an object for our forthcoming work in the field.
Projektbezogene Publikationen (Auswahl)
- Appl. Phys. Lett. 2013, 102, 233109
Kahnt, A.; Oelsner, C.; Werner, F.; Guldi, D. M.; Albu, S.P.; Kirchgeorg, R.; Lee, K.; Schmuki P.
- Chem. Commun. 2013, 49, 9128
Rotas, G., Charalambidis, G., Glätzl, L., Gryko, D. T., Kahnt, A., Coutsolelos, A.G., Tagmatarchis N
- ACS Appl. Mater. Interfaces, 2014, 6, 6724
Klaumünzer, M.; Kahnt, A.; Burger, A.; Mačković, M.; Münzel, C.; Srikantharajah, R., Spiecker, E.; Hirsch, A.; Peukert, W.; Guldi, D. M.
(Siehe online unter https://doi.org/10.1021/am5004552) - American Journal of Nano Research and Application 2014, 2, 9
Flyunt, R.; Knolle, W.; Kahnt, A.; Eigler, S.; Lotnyk, A.; Häupl, T.; Prager, A.; Guldi, D. M.; Abel, B
- Int. J. Rad. Biol, 2014, 90, 486
Flyunt, R.; Knolle, W.; Kahnt, A.; Prager, A.; Lotnyk, A.; Malig, J.; Guldi, D.; Abel, B.
(Siehe online unter https://doi.org/10.3109/09553002.2014.907934) - Chem. Commun., 2015, 51, 1631
Mohammadpour, F.; Moradi, M.; Lee, K.; Cha, G.; So, S.; Kahnt, A.; Guldi, D. M.; Altomare, M.; Schmuki P
(Siehe online unter https://doi.org/10.1039/c4cc08266d) - Chem. Eur. J. 2015, 21, 590
Nikkonen, T.; Moreno Oliva, M.; Kahnt, A.; Muuronen, M.; Helaja, J.; Guldi, D. M.
(Siehe online unter https://doi.org/10.1002/chem.201404786) - Nanoscale, 2015, 7, 19432
Kahnt, A.; Flyunt, R.; Laube, C.; Knolle, W.; Eigler, S.; Hermann, R.; Naumov, S.; Abel, B.
(Siehe online unter https://doi.org/10.1039/c5nr03444b) - Nanoscale, 2016, 8, 7572
Flyunt, R.; Knolle, W.; Kahnt, A.; Halbig, C.E.; Lotnyk, A.; Häupl, T.; Prager, A.; Eigler, S.; Abel, B.
(Siehe online unter https://doi.org/10.1039/c6nr00156d) - RSC Adv., 2016, 6, 68835
Kahnt, A., Flyunt, R., Naumov, S., Knolle, W.; Eigler, S.; Hermann, R.; Abel, B.
(Siehe online unter https://doi.org/10.1039/c6ra13085b)
