Gesteuerte Integration von funktionalisierten Janus-Nanopartikeln
Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Zusammenfassung der Projektergebnisse
The insights obtained during the project are manifold and prove that the original goal “control the integration of functionalized Janus-nanoparticles” is sophisticated but feasible. We synthesized and characterized a number of different compounds suitable for the stepwise growth of Ru-TP nanowires and the stepwise synthesis of AuNPs capped with TP or Ru-TP. The sequential application of TP ligand, Ru precursor and a TP linking unit allowed us to form Ru-TP wires on Au surfaces “in situ” in comparably mild conditions. The stepwise growth was investigated via IRRAS, SERS, VASE and XPS. Thereby, the orientation of the molecular wires relative to the surface was obtained. This information was essential to determine the necessary growth steps for the connection of electrodes with a given separation. We further established a synthesis route for two new Ru-TP complexes that allow direct functionalization of AuNPs with a diameter of approx. 15 nm. Each type of AuNP was characterized with respect to its protonation behaviour and the orientational configuration of the TP rings in the ligand shell. The functionalization of the AuNP with TP and Ru¬TP derivatives was verified using different techniques, including IR, Raman, AAS, and UV-Vis spectroscopy, as well as ICP MS and DLS. In order to immobilize the functionalized AuNP we fabricated heterometallic nanoelectrode pairs with a gap size approximately 10 nm, so that one AuNP can bridge the nanogap. Two different types of AuNPs, one functionalized with TP ligands and the second with Ru-TP ligands were assembled between these nanoelectrodes and thus, used to form nanodevices. The nanodevices were thoroughly electrically characterized. Thus, differences in the device conductance could be attributed to sensible differences in the molecule-metal contact formation and underlined their importance. Further, the conductance switching of Ru-TP AuNP was identified in device geometry. Subsequently, the performance of these Ru- TP AuNP devices was compared to the performance of devices formed by Ru-TP nanowires bridging the 10 nm gap between two nanoelectrodes. The use of long Ru-TP nanowires (length about 10 nm) produced by this method results in hopping conduction with an extremely low transport efficiency and hereby the loss of switching ability. In a readily accessible approach using multiple isotropic Ru-TP AuNPs in nanoelectrode gaps of 20 to 50 nm the light-driven switching behaviour of the Ru-TP complexes is measurable. Moreover, our sophisticated nanometer scale devices, assembled by single, switching Ru-TP AuNP in between a heterogenous nanoelectrode pair with a gap size of only 10 nm, reveal the potential to be used as storage elements. In addition, an asymmetry implemented into these devices by heterogeneous nanoelectrodes, Janus-type AuNP or by an accidential asymmetric contact geometry installs a rectifying functionality within the nanodevice. Additionally, we found conditions to successfully synthesize Janus-like AuNP with both, the Ru-TP complexes and the short conducting TP ligand. These Janus-like AuNP implemented in CMOS technology bear the possibility to combine switching and rectifying properties in the future.
Projektbezogene Publikationen (Auswahl)
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Polydiacetylene functionalized gold nanoparticles – stability and integration into a nanoelectrode device, JARA-FIT Annual Report, 2015
R. Liffmann, M. Homberger, M. Mennicken, S. Karthäuser, U. Simon
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Langmuir 2016, 32, 954-962
S. D. Bourone, C. Kaulen, M. Homberger, U. Simon
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RSC Adv., 2018, 8, 1717-1724
C. Kaulen, U. Simon
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J. Phys. Chem. C 2019, 123, 21367-21375
M. Mennicken, S. K. Peter, C. Kaulen, U. Simon, S. Karthäuser
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J. Phys. Chem. C 2019, 123, 6537-6548
S. K. Peter, C. Kaulen, A. Hoffmann, W. Ogieglo, S. Karthäuser, M. Homberger, S. Herres-Pawlis, U. Simon
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J. Phys. Chem. C 2020, 124, 4881-4889
M. Mennicken, S. K. Peter, C. Kaulen, U. Simon, S. Karthäuser
