TY - BOOK A1 - Brehmer, Ludwig T1 - 70-jähriges-Jubiläum der Gründung der Hochschul-Biologie und des Botanischen Gartens der Pädagogischen Hochschule Potsdam BT - eine administrative und wissenschafts-politische Retrospektive und Würdigung der Gründer T3 - Die Hochschulstadt in Sanssouci ; Band 8 Y1 - 2020 SN - 978-3-9821787-3-8 PB - Eigenverlag des Verfassers Brehmer CY - Schwielowsee ER - TY - BOOK A1 - Brehmer, Ludwig T1 - Die Brandeburgische Landeshochschule zu Potsdam im Jahre eins : die Hochschule in Potsdamer Schulen ; Daten und Fakten ; Kommentare und Dokumente Y1 - 2011 SN - 978-3-00-034135-9 VL - 4 PB - Eigenverl. des Verf CY - Potsdam ER - TY - JOUR A1 - Jarosz, Grazyna A1 - Signerski, Ryszard A1 - Brehmer, Ludwig T1 - On dielectric spectra of thin copper phthalocyanine films N2 - The work presents low signal dielectric spectra of gold/copper phthalocyanine/magnesium and gold/copper phthalocyanine/gold sandwich systems in the 25 Hz-1 MHz frequency range. The performed analysis enables us to distinguish the electrode resistance and the lattice polarization from processes related with electric transport, such as charge carrier relaxation at space charge region of a barrier and charge carrier injection in dielectric response. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00406090 U6 - https://doi.org/10.1016/j.tsf.2006.02.035 SN - 0040-6090 ER - TY - JOUR A1 - Jarosz, Grazyna A1 - Quinn, P. D. A1 - Stephan, Niels A1 - Brehmer, Ludwig T1 - Dielectric properties of zinc phthalocyanine thin films : effects of annealing in air and in N-2 N2 - This work presents the effects of ambient conditions, in particular oxygen and humidity, on the dielectric spectra of thin zinc phthalocyanine (ZnPc) films equipped with interdigitated electrodes and the effect of annealing in dry N-2 or in ambient air. The measurements were performed in the frequency range 10(-2)-10(5) Hz. The results indicate that the electric properties of ZnPc films are not only affected by oxygen but also by water vapour the presence of which always leads to the drop in alternating current conductance (ac-conductance). Moreover, at room temperature, the ac-conductance of ZnPc films previously exposed to air exhibits a reversible change with humidity, which makes these films attractive for humidity sensing applications. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0040-6090 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Souto, Jorge A1 - de Saja, J. A. A1 - Brehmer, Ludwig T1 - Brewster angle microscopy and surface potential measurements of Langmuir-Blodgett films of zinc tri(tert-butyl)- 4-sulphophthalocyanine N2 - The formation of a Langmuir monolayer of an amphiphilic derivative of zinc phthalocyanine (Na[(ZnPcSO3)-S-t]) has been studied by means of surface potential technique and Brewster angle microscopy. The experiments were undertaken in order to understand the behaviour of this monolayer with a well-defined surface pressure isotherm. The floating film is described as a truly monomolecular layer formed by very rigid islands in which the phthalocyanine units tend to take on a preferential orientation with their planes perpendicular to the air-water interface, for high values of the surface pressure. (c) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0169-4332 ER - TY - JOUR A1 - Dimitriev, O. P. A1 - Smertenko, P. S. A1 - Stiller, Burkhard A1 - Brehmer, Ludwig T1 - Polyaniline-transition metal salt complexes: insight into formation mechanisms N2 - Two basic morphologies of emeraldine base of polyaniline-transition metal salt complex films cast from N- methylpyrrolidinone solutions are described. The first morphology consists of grains and the other consists of loose aggregates, respectively. The correlation of the film morphology with formation of precipitate in the complex solution, kinetics of solvent evaporation from the cast film, amount of solvent entrapped in the film, film conductivity, and IR absorption spectra is shown. Two different mechanisms of the complex formation as a result of competition in the polymer- inorganic salt-solvent trio interactions are discussed; the first mechanism results in folding of macromolecules into compact coils being then a core of grains in the complex films, and the second mechanism leads to blending of the polymer chains with solvent giving rise to formation of loose aggregates. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0379-6779 ER - TY - JOUR A1 - Muzikante, I. A1 - Fonavs, E. A1 - Tokmakov, A. A1 - Cepite, D. A1 - Stiller, Burkhard A1 - Brehmer, Ludwig A1 - Neilands, O. T1 - Optical and electrical properties of oriented thin films of oligomer containing betaine-type moiety in side chain N2 - Non-linear optical and electrical properties of polymer films obtained by dipole orientation of active units are reported. Novel polar oligomer with N-(indan-1,3-dion-2-yl)pyridinium betaine (IPB) as a side group is studied. Orientation of polar groups in oligomer thin films causes an increase of the photo-induced change of surface potential on irradiation in the region of photo-induced electron transfer (PIET) where the IPB group exhibits a reversible change of the value and sign of the dipole moment. At longer wavelengths, the value of the surface potential of the oligomer may be determined by transport of photo-generated charge carriers Y1 - 2005 SN - 0370-1972 ER - TY - JOUR A1 - Wong, J. E. A1 - Detert, H. A1 - Brehmer, Ludwig A1 - Schrader, Sigurd T1 - Green light-emitting devices based on soluble oligo(phenylenevinylenes) N2 - In this work, we report our investigations on the film-forming properties as well as the optical and electroluminescent characterisations of a series of lateral-substituted soluble oligo(phenylenevinylenes) of various conjugation length. Preliminary investigations show that these materials are potential candidates for use in organic light-emitting devices (OLEDs). Two types of OLEDs were fabricated: single layer (SL) and single heterostructure (SHS), with poly(p-phenylenevinylene) (PPV) as hole transporting layer. Our best results were obtained with single layer device emitting green light with a luminance of 0.18 cd m(-2) and 0.24 cd m(-2) at a driving voltage of 10 V. (c) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0169-4332 ER - TY - JOUR A1 - Karageorgiev, Peter A1 - Neher, Dieter A1 - Schulz, Burkhard A1 - Stiller, Burkhard A1 - Pietsch, Ullrich A1 - Giersig, Michael A1 - Brehmer, Ludwig T1 - From anisotropic photo-fluidity towards nanomanipulation in the optical near-field N2 - An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated Y1 - 2005 SN - 1476-1122 ER - TY - JOUR A1 - Bochenkov, V. A1 - Karageorgiev, Peter A1 - Brehmer, Ludwig A1 - Sergeev, G. B. T1 - Quenched growth of nanostructured lead thin films on insulating substrates N2 - Lead island films were obtained via vacuum vapor deposition on glass and ceramic substrates at 80 K. Electrical conductance was measured during vapor condensation and further annealing of the film up to room temperature. The resistance behavior during film formation and atomic force microscopy of annealed films were used as information sources about their structure. A model for the quenched growth, based on ballistic aggregation theory, was proposed. The nanostructure, responsible for chemiresistive properties of thin lead films and the mechanism of sensor response are discussed. (C) 2003 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0040-6090 ER -