Diodes based on bilayers comprising of tetraphenyl porphyrin derivative and fullerene for hybrid nanoelectronics

The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents

C60 fullerene exhibits unique optical properties that have high potential for wide photo-optical applications. To analyze the optical properties of C60, its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, non-polar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to Ag → T1u and Ag → T1g transitions. However, these bands differed from the solid C60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C60 and the organic solvents due to their different solvent polarities.

Electrografted monolayer based on a naphthalene diimide–ruthenium terpyridine complex dyad: efficient creation of large-area molecular junctions with high current densities

Robust monolayers with multiple redox states were used to create large-area molecular junctions (MJ) with a high yield of operating devices. These MJs show high current densities and rectifications properties.

Silicon-pyrene/perylene hybrids as molecular rectifiers

We have synthesized two alkenyl (C-6 and C-11 chains) pyrenes and one alkenyl (C-11 chain) perylene as the σ-π systems, which were electro-grafted on H-terminated Si surfaces to form the respective monolayers. The I-V characteristics of the monolayers revealed pronounced rectification in forward bias with a maximum rectification ratio (RR) of 2.5 × 10(5) at 2.5 V for the C-6-pyrene 4b, 1000 at 1.5 V for the C-11-pyrene 4a and 3000-5000 at 1.75 V for the C-11-perylene 3. The higher RR of the devices containing 4b compared to those of 4a and 3 is possibly due to better alignment and packing of the 4b-monolayers on the Si substrate. The rectification was explained using the ab initio molecular-orbital calculations.

Synthesis, electron transport, and charge storage properties of fullerene–zinc porphyrin hybrid nanodiscs

A MIS-type diode (Ag/C₆₀–ZnTANP circular discs/p-Si/Ag) has been fabricated and its charge storage properties have been explored.

Self-metalation of 2H-tetraphenylporphyrin on Cu(111): an x-ray spectroscopy study

The bonding and the temperature-driven metalation of 2H-tetraphenylporphyrin (2H-TPP) on the Cu(111) surface under ultrahigh vacuum conditions were investigated by a combination of x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy with density functional theory calculations. Thin films were prepared by organic molecular beam epitaxy and subsequent annealing. Our systematic study provides an understanding of the changes of the spectroscopic signature during adsorption and metalation. Specifically, we achieved a detailed peak assignment of the 2H-TPP multilayer data of the C1s and the N1s region. After annealing to 420 K both XPS and NEXAFS show the signatures of a metalloporphyrin, which indicates self-metalation at the porphyrin-substrate interface, resulting in Cu-TPP. Furthermore, for 2H-TPP monolayer samples we show how the strong influence of the copper surface is reflected in the spectroscopic signatures. Adsorption results in a strongly deformed macrocycle and a quenching of the first NEXAFS resonance in the nitrogen edge suggesting electron transfer into the LUMO. For Cu-TPP the spectroscopic data indicate a reduced interaction of first-layer molecules with the substrate as demonstrated by the relaxed macrocycle geometry.