Long-Term Degradation Mechanisms in Application-Implemented Radical Thin Films.

Blatter radical derivatives are very attractive due to their potential applications, ranging from batteries to quantum technologies. In this work, we focus on the latest insights regarding the fundamental mechanisms of radical thin film (long-term) degradation, by comparing two Blatter radical derivatives. We find that the interaction with different contaminants (such as atomic H, Ar, N, and O and molecular H2, N2, O2, H2O, and NH2) affects the chemical and magnetic properties of the thin films upon air exposure. Also, the radical-specific site, where the contaminant interaction takes place, plays a role. Atomic H and NH2 are detrimental to the magnetic properties of Blatter radicals, while the presence of molecular water influences more specifically the magnetic properties of the diradical thin films, and it is believed to be the major cause of the shorter diradical thin film lifetime in air.

FePc and FePcF16 on Rutile TiO2(110) and (100): Influence of the Substrate Preparation on the Interaction Strength.

Interface properties of iron phthalocyanine (FePc) and perfluorinated iron phthalocyanine (FePcF16) on rutile TiO2(100) and TiO2(110) surfaces were studied using X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and low-energy electron diffraction (LEED). It is demonstrated that the interaction strength at the interfaces is considerably affected by the detailed preparation procedure. Weak interactions were observed for all studied interfaces between FePc or FePcF16 and rutile, as long as the substrate was exposed to oxygen during the annealing steps of the preparation procedure. The absence of oxygen in the last annealing step only had almost no influence on interface properties. In contrast, repeated substrate cleaning cycles performed in the absence of oxygen resulted in a more reactive, defect-rich substrate surface. On such reactive surfaces, stronger interactions were observed, including the cleavage of some C-F bonds of FePcF16.

Island shape and electronic structure in diindenoperylene thin films deposited on Au(110) single crystals.

We have investigated diindenoperylene (DIP) thin films deposited on Au(110) single crystals, by using a multi-technique approach based on X-ray photoemission spectroscopy (XPS), resonant photoemission spectroscopy (RPES), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, atomic force microscopy (AFM) and photoemission electron microscopy (PEEM). DIP molecules are physisorbed on gold, with image-charge screening playing the major role as an interface phenomenon. DIP thin films show Stranski-Krastanov growth mode and the structural herringbone arrangement mimics the arrangement found in DIP single crystals. These results are common with the (100) and (111) gold substrate geometries. On the contrary, the island aggregation is substrate geometry-dependent. This paves the way to exploit the degree of anisotropy in different lattice geometries as a tool for molecular patterning of inorganic surfaces, keeping the electronic structure preserved.

Electronic structure at transition metal phthalocyanine-transition metal oxide interfaces: Cobalt phthalocyanine on epitaxial MnO films.

The electronic structure of the interface between cobalt phthalocyanine (CoPc) and epitaxially grown manganese oxide (MnO) thin films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results reveal a flat-lying adsorption geometry of the molecules on the oxide surface which allows a maximal interaction between the π-system and the substrate. A charge transfer from MnO, in particular, to the central metal atom of CoPc is observed by both PES and XAS. The change of the shape of N-K XAS spectra at the interface points, however, to the involvement of the Pc macrocycle in the charge transfer process. As a consequence of the charge transfer, energetic shifts of MnO related core levels were observed, which are discussed in terms of a Fermi level shift in the semiconducting MnO films due to interface charge redistribution.

Communication: Influence of graphene interlayers on the interaction between cobalt phthalocyanine and Ni(111).

The influence of graphene interlayers on electronic interface properties of cobalt phthalocyanine on Ni(111) is studied using both photoemission and X-ray absorption spectroscopy. A charge transfer associated with a redistribution of the d-electrons at the Co-atom of the phthalocyanine occurs at the interface to Ni(111). Even a graphene buffer layer cannot prevent the charge transfer at the interface to Ni(111); however, the detailed electronic situation is different.

The development of [(124)I]iodinated-VG76e: a novel tracer for imaging vascular endothelial growth factor in vivo using positron emission tomography.

The development of anticancer therapies that target the angiogenic process is an area of major growth in oncology. A method of noninvasively measuring tumor vascular endothelial growth factor (VEGF) in vivo could provide important efficacy information for VEGF-dependent antiangiogenic agents and the role of VEGF in cancer biology. We have developed a novel radiotracer for use with positron emission tomography (PET) that enables noninvasive imaging of VEGF. This radiotracer comprises an IgG1 monoclonal antibody, known as VG76e, that binds to human VEGF, labeled with a positron-emitting radionuclide, iodine-124 ([(124)I]-SHPP-VG76e). Three radiolabeling strategies were evaluated to synthesize the radiotracer with optimal radiochemical yield, purity, and immunoreactivity. To evaluate the pharmacokinetics and VEGF-specific localization of [(124)I]-SHPP-VG76e, two subclones of the HT1080 human fibrosarcoma selected on the basis of differing VEGF production (26.6 and 1/3C, the former producing 2-4-fold more in vitro) were established in culture and grown as solid tumor xenografts in immune-deficient mice. A single i.v. injection of the radiotracer into tumor-bearing mice revealed a time dependent and specific localization of [(125)I]-SHPP-VG76e to the tumor tissue. Three validation studies established the VEGF specificity and potential for use of [(124)I]-SHPP-VG76e in vivo: (a) uptake of [(125)I]-SHPP-VG76e was 1.8-fold higher in HT1080-26.6 compared with HT1080-1/3C tumors (P < 0.05); (b) uptake of [(125)I]-SHPP-VG76e in HT1080-26.6 tumors was specifically blocked by prior administration of excess unlabeled VG76e (P < 0.05); and (c) tumor uptake of the IgG1, [(125)I]-SHPP-CIP5, which has a similar molecular weight as [(125)I]-SHPP-VG76e but does not recognize VEGF, was the same for both HT1080-26.6 and HT1080-1/3C (P > 0.05). Other than tumor localization, [(125)I]-SHPP-VG76e was present in urine and blood and to a lesser extent in heart, lungs, liver, kidney, and spleen. Whole-animal PET imaging studies revealed a high tumor-to-background contrast and also revealed [(124)I]-SHPP-VG76e distributions in the major organs. These studies support further development of [(124)I]-SHPP-VG76e as a radiotracer for measuring tumor levels of VEGF in humans.