Max Lippitsch

Karl-Franzens-Universität · Experimental Physics

Draxler, Sonja; Lippitsch, Max E. & Gudrun Wolfschmidt: Preface: Harmony and Symmetry - Celestial regularities shaping human culture. Harmony and Symmetry. Celestial regularities shaping human culture. Hamburg: tredition 2020, p. 17-20. It is a well-established procedure for SEAC annual conferences to set a special motto defining the general theme...

Harmony and Symmetry. Celestial regularities shaping human culture. Proceedings of the SEAC 2018 Conference in Graz. Edited by Sonja Draxler, Max E. Lippitsch & Gudrun Wolfschmidt. Hamburg: tredition (European Society for Astronomy in Culture - SEAC Publications; Vol. 01) 2020. With contributions by Rita Gautschy, Aleksandra Bajić, Alexey Stoev, Pe...

The Liber floridus is a medieval encyclopaedia, authored by a certain Lambert, Canon of Saint-Omer. The work was finished in 1121 and deals with a multitude of different topics, from religion and history to geography and astronomy. The Gent manuscript, which is the autograph, contains 287 folios of parchment. Detailed descriptions were given by Del...

Peter Apian was a German humanist and famous for his works in mathematics, astronomy and cartography. From 1519 to 1521 he spent a few years at the University of Vienna to study geography and astronomy. One of his most famous works, the Astronomicum Caesareum, describes the mechan- ics of a geocentric universe and is one of the most beautiful scien...

Der Nobelpreis für Physik 2009 geht zur Hälfte an Charles Kuen Kao, die andere Hälfte teilen sich Willard Sterling Boyle und George Elwood Smith. Sie haben einen unüberseh-baren Beitrag zur modernen Infor-mationstechnologie geleistet. Kao eröffnete mit seinen Entdeckun-gen den Weg für die Glasfasertech-nologie in die modernen Kommu-nikationstechnik...

Original latin text and translation into German with glosses, comprising the following parts of the book: Monitum de secunda editione. Praefatio. Dissertatio. Biwald's biography, written by his contemporary Michael Kunitsch, is added.

Book review: Ilse Maria Fasol-Boltzmann, Gerhard Ludwig Fasol (eds.): Ludwig Boltzmann, on the centenary of his death. Springer Wien New York (in German)

Report on an international project for the World Year of Physics 2005

Combining a transparent substrate and a transparent sensing layer of rather similar refractive index into a common waveguiding structure produces an inhomogeneous waveguide, where a large portion of the total energy transverses the sensing layer. This yields much superior sensor performance. The transmission through a waveguide is subject to variou...

The effect of conformation (E/Z isomerism), nature (donor/acceptor) of substituents, and endgroups (indandione, pyrazolone, pyrazoledione) on the molecular hyperpolarizability βvec of dicyanomethylene (hetero)aromatic dyes is investigated by means of semiempirical (AM1, ZINDO) molecular orbital calculations. Unless Z isomers are stabilized by intra...

A new and simple preparation procedure for fluorophore absorber pairs which enable optical sensing of ammonia is reported. In ion pairs formed between organoruthenium complexes (fluorophore) and triphenylmethane dyes (absorber), a deprotonation of the absorber leads to an absorbance band which overlaps the emission of the fluorophore whereby both t...

A portable, compact device for measuring blood gases by using the fluorescence decay time as the information carrier is presented. The instrument is based on solid state technology only, thus using LEDs for excitation and a photodiode as detector. A capillary coated on its inner surface with different sensing membranes serves as a sample compartmen...

Sensing of anions has been investigated using the fluorescence decaytime as the information carrier. The sensing mechanism is based on the coextraction of an anion and a proton, and the presence of a fluorophore with a rather long fluorescence decaytime inside the membrane to act as a pH indicator. The relevant theory is discussed shortly. As an ex...

An instrument has been designed and implemented capable of mapping oxygen distribution in skin tissue over an area of several square centimeters with a spatial resolution of better than 1 mm and with a resolution in oxygen partial pressure of better than 5 torr. The measurement scheme is optical and is based on luminescence lifetime. It is non- inv...

A small, portable, inexpensive instrument for measuring fluorescence lifetimes in optical sensors has been developed, which employs a super-bright blue or red light-emitting diode (LED) as excitation source and a photodiode with a fast high-gain amplifier for the detection of the fluorescence. A time resolution of down to 20 ns can be achieved with...

Advantages of luminescence-lifetime over intensity measurements in sensing applications include independence of variations in source intensity, detector sensitivity, light throughput and, most importantly, indicator concentration. Nevertheless, most researchers still believe that lifetime measurement needs highly sophisticated instrumentation and h...

Glass capillaries with a chemically sensitive coating on the inner surface are used as optical sensors for medical diagnostics. The capillary simultaneously serves as a sample compartment, a sensor element, and an inhomogeneous optical waveguide. Different optical setups have been investigated and compared regarding its waveguiding properties.

Most intrinsic fiberoptic sensors are based on the evanescent-wave scheme, where the evanescent field of modes guided in a fiber reaches out into a chemically sensitive coating. In the commonly used multimode waveguides, the evanescent field contains only a small part of the total energy, however, thus making evanescent-wave sensors rather insensit...

Glass capillaries with a chemically sensitive coating on the inner surface are used as optical sensors for medical diagnostics. A capillary simultaneously serves as a sample compartment, a sensor element, and an inhomogeneous optical waveguide. Various detection schemes based on absorption, fluorescence intensity, or fluorescence lifetime are descr...

A family of sensors is presented with fluorescence decay-time measurements used as the sensing technique. The concept is to take a single fluorophore with a suitably long fluorescence decay time as the basic building block for numerous different sensors. Analyte recognition can be performed by different functional groups that are necessary for sele...

This study aims at a quantitative extraction of specific solvent effects of hydroxylic solvents on the non-radiative decay of tris(2,2′-bipyridyl) ruthenium(II). For this purpose the emission spectra, quantum yields and excited state lifetimes of the dye were measured in a series of monovalent linear alcohols. Separation of the non-radiative decay...

Glass capillaries with a chemically sensitive coating on the inner surface are used for optical chemical sensing in gaseous and liquid samples. The light from an LED or a laser is coupled into and out of the capillary under a well-defined angle. The coated glass capillary acts as an inhomogeneous waveguide, in which light is guided in both the glas...

The influence of the microenvironment on the fluorescence behavior of indicator molecules is investigated. A model is developed to describe the fluorescence decay of indicator molecules in a nonuniform medium. Its consequences for fluorescence lifetime-based chemical sensors are discussed and verified in two examples, namely, a pH sensor using a py...

Glass capillaries with a chemically sensitive coating on the inner surface coating on the inner surface are used as optical sensors for medical diagnostics. The capillary simultaneously serves as a sample compartment, a sensor element, and an inhomogeneous optical waveguide.

An analytical instrument comprising absorption- and fluorescence-based capillary waveguide optrodes (CWOs) is described. Glass capillaries with a chemically sensitive coating on the inner surface are used for optical chemical sensing in gaseous and liquid samples. In case of absorption-based CWOs, light from a LED is coupled into and out of the cap...

A new approach for using optical fibres as sensing elements by exploiting the evanescent field of the guided wave is proposed. The optical principle is based on the differential phase modulation between the two orthogonal polarization modes of a single-mode fibre via evanescent field interaction with sensitive thin films deposited on the side-polis...

Nonlinea Stern-Volmer quenching characteristics are a common feature of oxygen sensors containing Ru(II) complexes immobilized in solid-state matrices. We discuss the origins of this behaviour and address the implications of the molecular processes on sensor performance with the help of two different sensor systems: (1) For tris(2,2′-bipyridyl)Ru(I...

Optical pH sensors based on different fluorescence decay times of acid and base forms of suitable indicators have been developed. The indicator is incorporated in a hydrogel matrix providing the aqueous environment necessary for the acid-base reactions. Dramatic improvement of long-term stability and reproducibility compared to conventional intensi...

A family of indicators has been developed for measuring different analytes, all the indicators being derivatives of the same chemical compound and having identical spectral and lifetime properties. The indicators show an absorption accessible to low-cost light sources, a large Stokes shift, and a long fluorescence decay time. All indicators can be...

An analytical instrument comprising absorption- and fluorescence-based capillary waveguide optrodes (CWOs) is described. Glass capillaries with a chemically sensitive coating on the inner surface are used for optical chemical sensing in gaseous and liquid samples. In case of absorption-based CWOs, light from a LED is coupled into and out of the cap...

The excited state of Ru(II)[bpy]32+ dissolved in hydroxylic solvents is subject to specific solvent effects, which were hitherto not understood on a quantitative basis. We determined the solvent effects of linear monovalent alcohols on the energy gap law of internal conversion with the help of lifetime and intensity measurements. An on-line method...

A family of indicators has been developed for fluorescence lifetime-based measurement of oxygen, pH, carbon dioxide, and potassium, all the indicators being derivatives of the same chemical compound and having identical spectral and lifetime properties. The indicators show an absorption accessible to low- cast light sources, a large Stokes shift, a...

The influence of the environment on the fluorescence behavior of indicator molecules is investigated. A model is developed to describe the fluorescence decay of indicator molecules in a non-uniform medium. Its consequences for fluorescence decay time based chemical sensors are discussed and verified in two examples, namely a pH sensor using a pyren...

Quenching of luminescence by oxygen of ruthenium diphenylphenanthroline in various polymers was studied by time-resolved spectroscopy. The luminescence decay was not single exponential, and the Stern-Volmer plot was nonlinear (downward-curved) in all cases. A new model for describing the nonexponential luminescence decay was developed, which consid...

A family of sensors is presented with fluorescence decay-time measurements used as the sensing technique. The concept is to take a single fluorophore with a suitably long fluorescence decay time as the basic building block for numerous different sensors. Analyte recognition can be performed by different functional groups that are necessary for sele...

Chemically homogeneous polymer layers loaded with oxygen-quenchable luminescent dyes may lead to promising applications for optical oxygen sensing. In this work, luminescence quenching of tris(4,7'-diphenyl-1-1,10'phenanthroline)Ru(II) perchlorate, dissolved in a polystyrene layer, has been investigated. Although the dye appears to be molecularly d...

A method developed for quantitative determination of static and dynamic contributions to luminescence quenching is applied to Ru(II) complexes in polymer matrices (silica gel and polystyrene), quenched by oxygen. This method is based on both intensity and lifetime quenching experiments. The curvature of intensity Stern-Volmer plots is related to th...

The technical requirements for a small, rugged, and moderately- priced device for measuring fluorescence lifetimes have been investigated. The suitability and performance of various lifetime measuring schemes were compared. Based on these investigations a compact time-domain instrument was developed allowing measurement of fluorescence decays with...

Optical sensors often suffer from poor long-term stability. This drawback can be overcome by using fluorescence decay-time measurement as the sensing principle. In this way calibration- free chemical sensors can be developed. The sensing scheme has been used so far mainly in connection with dynamic quenching, for example in oxygen sensors. We have...

Absorption and CW and time-resolved fluorescence nleasurements were performed to investigate the excited-state acid-base kinetics and equilibria of norharman in aqueous solutions of different pH. Four different excited-state species, namely cation, neutral molecule, anion,and zwitterion, can be distinguished. Rate-equations were applied to explain...

Sensors based on luminescence suffer from the fact that during the operating time of the instrument changes in source intensity, light throughput, detector sensitivity, indicator quantum yield, and indicator concentration are inevitable and have to be overcome by extensive referencing and recalibration procedures. Sensors based on luminescence deca...

Picosecond time-resolved transient absorption studies with phytochrome in its red light absorbing form (Pr) isolated from rye (Secale cereale cv. Danae) are reported. After excitation of Pr with 6 ps pulses at 621 nm the transient absorption spectra were measured at various delay times from 5 ps up to 1 ns. Upon excitation an increase in the transi...

Optical sensors based on fluorescence usually suffer from dye leaching and bleaching, yielding erroneous results. Decay-time-based sensors, which overcome this drawback, need rather sophisticated measuring equipment. An attactive possibility is to measure the decay time indirectly via fluorescence polarization anisotropy. In this contribution vario...

Fluorescence decay-time measurements in chemical sensors have so far been based on dynamic quenching, which is not well suited for pH measurements. Several other mechanisms are described in this contribution. The conditions necessary for an indicator to be useful in a decay-time-based pH-sensing scheme are clarified and the suitability of this sche...

Sensors based on luminescence intensity measurements suffer from the fact that, during the operating time of the instrument, changes in source intensity, light throughput, detector sensitivity, indicator quantum yield and indicator concentration are inevitable and have to be overcome by extensive referencing and recalibration procedures. Decay-time...

The second-order polarizability of organic molecules depends sensitively on their chemical structure. Modification by reversible chemical interactions alters the non-linear optical response, and hence the intensity of second-harmonic radiation. This fact has been exploited to construct a pH sensor using Langmuir-Blodgett films containing optically...

Optical second-harmonic generation (SHG) was performed in Langmuir-Blodgett films of 4-octadecyl-4'-nitrostilbene (OANS). The linear and non-linear optical properties are dependent on the preparation, especially on the pH value of the aqueous subphase. In films drawn from a subphase at pH 1.5 the absorption spectrum as well as the second-order hype...

Donor (anthracene) sensitized acceptor (perylene) fluorescence is quenched more efficiently by halothane than is intrinsic perylene fluorescence. The underlying process of dynamic fluorescence quenching is investigated by time-resolved fluorescence spectroscopy.