Analysegeräte und Methoden

• Monolagenuntersuchungen
• Doppelbrechungs-Mikroskopie
• AFM/STM-Mikroskopie
• REM-Mikroskopie
• Raman-Mikroskopie
• Spektroelektrochemie
• GPC, HPLC, GC, GC/MS, AAS

andere Geräte

• Hydrothermalsynthese
• Mikrowellensynthese
• Autoclav
• Photoreaktor

Monolagenuntersuchungen

The group is equipped with different Langmuir troughs (http://www.nima.co.uk) for the purpose of investigating water-insoluble monolayers of organic molecules which are spread at the air-water interface. As a main characteristics of monolayers, the compression isotherms can be recorded in conjunction with their corresponding potential isotherms.

Working principle of the Kelvin probe

Monolayer structures can be directly visualized using a state-of-the-art Brewster angle microscope (http://www.nanofilm.de). Moreover, monolayers can be transfered onto solid substrates employing the well established Langmuir-Blodgett technology, and the deposited LB-films can be analyzed by various analytical techniques including imaging ellipsometry, STM/AFM, X-ray reflectivity, or contact angle measurements.

Working principle of the Brewster-angle microscope

Crystal growing underneath a monolayer in a Langmuir trough

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Doppelbrechungsmikroskopie

We have recently applied birefingence microscopy (LC-PolScope^TM) in order to investigate the domain structure of polycrystalline thin films. In general, this imaging system allows to quickly and easily measure stress and structure in transparent materials, and it provides a unique method to measure and analyze low-level birefringence in samples. Traditional methods for measuring the spatial distribution of birefringence with polarized light are cumbersome and time-intensive. LC-PolScope technology opens the door to the world of birefringence imaging by automating the process of quantitative polarization microscopy, allowing accurate measurements of retardance magnitude and orientation at every pixel within seconds. Another application field of birefingence microscopy is live-cell imaging, collagen birefringence mapping, and structural imaging. This technology enables fine birefringent structures to be imaged and measured within living cells or other materials non-invasively – without harmful dyes or UV light. It enables direct observation of microtubules, actin filaments, meiotic spindles, and neural growth cones at sensitivities two hundred-times greater than conventional polarized light methods.

Schematic view of the LC-PolScope imaging system. The computer-controlled LC variable retarders and linear polarizer comprise the “LC compensator” optical assembly

a) LC-PolScope image of a polycrystalline calcite thin film (retardance given as pseudo-color). b) Retardance grayscale image overlaid by short lines indicating the orientations of the slow birefringence axis measured in each location. (Slow axis orientations are typically shown for every 15 pixel in the horizontal and vertical direction of the original video frame).

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AFM/STM-Mikroskopie

The Agilent 5500 AFM/SPM microscope offers numerous unique features, such as patented top-down scanning and unrivalled environmental and temperature control, while providing maximum flexibility and modularity. The universal microscope base permits easy integration with an environmental chamber or an inverted optical microscope. Sample preparation is made easy with our unique sample plates designed for your application including imaging in fluids.

A top-down optical axis through the scanner allows an unobstructed view of the cantilever and the sample without sacrificing sample handling. The scanner’s modular nose cone makes changing imaging modes quick and easy. The Agilent 5500 SPM/AFM is a high performance system that facilitates advanced applications solutions. It offers atomic resolution and is ideal for electrochemistry, polymers, and soft material applications.

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REM-Mikroskopie

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Raman-Mikroskopie

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Spektroelektrochemie

The group has recently expanded its analytical facilities by purchasing a full line of electrochemical instruments, including a research potentiostat (PARSTAT 2273) and a quartz crystal microbalance (PARSTAT 922). Different electrochemical cells are available including sets for microanalytical measurements, potential-controlled bulk electrolysis (electrosynthesis), and spectro-electrochemistry.

PARSTAT 2273 research potentiostat

PARSTAT 922 EQCM

Electrochemical cell kits

Key specifications of the potentiostat include:

• 2 A current max. (20 A boosted)
• 100 V compliance
• 1.2 fA current resolution
• >10¹³ Ohms input impedance
• <5 pF of capacitance
• 10 µHz to 1 MHz built-in analyzer for impedance

Applications

The PARSTAT 2273 is a fit for any application in electrochemistry.  Its high current, built-in EIS, and the ability to be boosted up to 20 amps makes it ideal for fuel cell and battery work.  The unique combination of high-compliance voltage and wide current range allows it to handle any corrosion measurement required.  For coatings, even the thickest coatings can be handled due to the high input impedance and low input capacitance.  For voltammetry, the excellent resolution and sensitivity in the current are a must and are well suited for the most precise measurements. (A short survey of basic electrochemical techniques is available here.)

The QCM922 Quartz Crystal Microbalance can be employed to monitor mass changes at the surface of the electrode. It is sensitive enough to measure weight changes in a monolayer.

With the addition of a potentiostat/galvanostat, the QCA922 system (with the Pt or Au coated resonator serving as the working electrode) can provide information on potential, current, charge, resonant frequency (mass), and resonant resistance (viscosity) simultaneously. This allows researchers to analyze electrochemical depositions, polymer films formation on electrodes, corrosion, adsorption and electrochemical reaction mechanisms. Other application areas include battery research, electroplating and biosensor development.

Spectroelectrochemistry Application

• Ion transfer analysis
• Spectroscopic analysis of electrode surfaces
• Spectral absorption analysis of redox reaction products or intermediates
• Analysis of reaction parameters such as concentration, diffusion coefficient, life span

Measurement are performed using a fiber optical spectrometer, light source and fiber optics to transmit light with a proper wave length through the electrode. Light which passes through the electrode changes its spectral characteristics due to electrochemical reactions occuring at the electrode surface.

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GPC, HPLC, GC, GCMS

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Hydrothermalsynthese

Hydrothermal Synthesis of our MOFs is performed with commercially available programmable heating blocks (TH20, HLC Biotec).

For upscaling experiments and synthesis of larger amounts we use a custom product from Barkey GmbH.

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Mikrowellensynthese

For fast and high yield synthesis of MOFs and other applications we use the CEM Discover S-Class and Explorer microwave synthesizer.

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