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We compare the electronic structure of differently fluorinated copper phthalocyanines (CuPC, CuPCF4, and CuPCF16) using x-ray photoemission spectroscopy and valence-band ultraviolet photoemission spectroscopy. Whereas the ionization potential (IP) is increased by more than 1 eV as a function of the degree of fluorination, further electronic properties such as the optical gap or the composition of the highest occupied molecular orbital and lowest unoccupied molecular orbital remain nearly unchanged. This fact renders these compounds an ideal tool for the investigation of the influence of the IP on the interface properties. At the interface to gold, besides interface dipoles we observe both downward and upward band bending. These phenomena depend clearly on the IP of the phthalocyanines.

A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H

Highly concentrated 0.5 M II-VI semiconductor quantum dot solutions for coating applications can be synthesized employing chalcogenolysis and condensation of functionalized cluster-like cadmium and zinc ethoxyacetates. Furthermore, in nucleation studies on CdSe solutions, new magic clusters between 0.42 and 1.7 nm in size were found exhibiting sharp HOMO-LUMO resonances (lowest absorption features) in the optical absorption spectra. High resolution small angle X-ray scattering (SAXS) measurements performed on 1.7 and 3.4 nm CdSe clusters corroborate the size. Information on the intra-cluster structure was hard to derive with respect to the small cluster size. These species could be Koch pyramids with a fractal dimension Df=2 as well as non-fractal zincblende pyramids (additionally checked by XRD and HFtTEM). In any case rather chain-like (Dt= 1) aggregates are formed. It further will be shown that in alcoholic CdSe sols the initially nucleated "seeds" are highly reactive. Their sharp HOMO-LUMO transitions are found to be strongly modified by externally induced chemical reactions. For example, aminosilane capped 1.7 nm clusters decompose rapidly upon exposure to phosphines. After a period of few hours, they begin to re-grow to their original size or they reorganize to give smaller 0.85 nm subunits depending on the P/N ratio. In contrast, 0.85 nm phosphinecapped clusters double their size if exposed to amines. The last process liberates cadmium ions into the solution as found in complementary polarographic measurements. ~ allel to this work and the sol-gel chemistry of metal oxides, addressing metal ethoxy-acetate derived synthesis of II-VI chalcogenide quantum dots, to provide insights into the cluster-cluster aggregate evolution mechanism within the strong exciton confinement regime. We shall demonstrate that chemical surface reactions can change both the cluster optical absorption and fluorescence spectra related to structural changes within cluster-cluster aggregates. This spectroscopic work is supported by SAXS-, XRDand HRTEM investigations addressing a fractal character of highly concentrated semiconductor cluster materials. Experimental GeneralAU manipulations involving silylchalcogenides and phosphines were carried out under argon using the Schlenk technique. Cadmium and zinc acetate dihydrate were purchased from Fluka. Bis(trimethylsily1)selenium (TMS)2Se prepared according to the procedure described elsewhere [15] was stored at 240 K under argon. Bis(trimethylsily1)sulfide (TMS)$3 and bis(trimethylsily1)tellurium (TMS)2Te were purchased from Aldrich and Acros respectively. Anhydrous heptane, pyridjne, tetrahydrofuran (THF) and 2-butoxyethanol in addition to aUcyl amines and tributylphosphine (TBP) were purchased from Aldrich. 3-Aminopropyltriethoxy-silane (AMEO) was purchased from ABCR. All chemicals were used without additional purification.