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Research and Expertise

 

 

Nanotechnology, the convergience of scientific disciplines

Faculty of Chemistry

The motivation of nanotechnology is based on recent developments and potentials of top-down and bottom-up approaches:

In nanotechnology, deterministic physical top-down approaches and statistical chemical bottom-up strategies are converging (from U.Sleytr, Boku Wien). 

 

Nanotsciences are concerned with material chemical issues on the scale from 100 nm down to 1 nm:

 

 

 

 

 

 

 

 

 

 

 

 

 

   

Physical Chemistry and Nanotechnology of Interfaces

(Department of Physical Chemistry, Working Group Prof. Kautek)

• Ultrafast phenomena and nanoscale structures in the area of interfacial research
• fs-Laser-Nanostrukturierung 
• In-situ-fs-Laser-Nanostrukturierung im a-SNOM 
• In-situ-fs-Mikroskopie im aperturfreien Nahfeld einer Rastersonde (a-SNOM)
• Bioelektrochemie: Proteine, Selbstorganisation 
• Multiphotonen 3D-Mikroskopie 
• Single Molecule Spektroskopie im elektrochemischen Multiphotonen 3D-Mikroskop 
• fs-Laseranregung der Selbstorganisation von biologischen, organischen und anorganischen Festkörperoberflächen im Nanoskalenbereich 
• Femto-Elektrochemie heißer Elektronen (Pikosekunden-Strompulse) 
• Laser-Reinigung von Kunstwerken und Dokumenten (Papier, Pergament, Textilien) 
• fs-Laser-Medizin: Ophthalmologie 


The activity of “Physical Chemistry and Nanotechnology of Interfaces" relies on pioneering work for more than 15 years in demonstrating femtosecond machining down to the nanscale of a broad variety of materials soon after fs-laser got available in the early nineties. Experience exists in top-down femtosecond laser ablation allowing micro- and nanomachining of 1D, 2D, and 3D structures in metals, transparent solids and biological tissues that cannot be made any other way. A special advantage is the unique possibility of congruent machining of highly inhomogeneous composite materials. Pulse durations (<80 fs="" far="" below="" the="" electron-phonon="" relaxation="" time="" in="" solids="">1 fs) provide the unique possibility to deterministically excite the electronic system by multi photon excitation resulting in unique precision in contrast to "conventional" fs-laser applications (>100 fs) where stochastic avalanche processes result in poor ablation qualities.

Comparison between amplified laser system (CPA) and high energy oscillators concerning repetition rate and output energy.

A novel optical setup coupling sub-60 fs-pulses into a high precision microscope will allow ultrahigh-precision processing. fs-pulses are necessary to avoid large heat affected zones (> 1µm) common with conventional ns-pulse lasers. Such non-linear phenomena can be exploited to reach supercritical intensities only in the focus of transparent bulk materials enabling laser direct-writing of 3D devices containing optical and microfluidic networks. This new approach to set up nano and microstructures can be applied to almost any transparent composite and functional material. 

It was recently demonstrated that fs-laser-induced self assembly of nanostructures on solids opens a new approach to nano-structure surfaces bottom-up 
Fs-Laser ablation of solids in liquid contact can be a process for synthesizing nanoparticles and nanotubes/nanorods Thus uniformly small particles precipitate in solution. Fs-Pulsed laser deposition can serve to transfer delicate polymeric and biopolymeric materials to any substrate (fs-Laser Induced Forward Transfer, fs-LIFT) as a microprinting process avoiding thermal damage in sharp contrast to conventional nanosecond technology in LIFT.
Electrochemical scanning force microscopy allows to investigate the molecular structure of double layers and nanomanipulate electrified interfaces.
Biolectrochemistry could be demonstrated on crystalline single layer proteins on electrodes in a longterm collaboration with the Vienna University of Natural Resources and Applied Life Sciences (BOKU)


Functional Materials

(Department of Physical Chemistry, Working Group Prof. Rogl)

New Quantum Phases of Matter

Motivation for this research is the quest to discover new quantum phases of matter and realize them in practical materials. Research is based on the recent discovery of “CePt3Si, the first heavy Fermion superconductor without a centre of symmetry”. As a consequence of missing centrosymmetry in the crystal structure space and time inversion symmetries and gauge symmetries are broken. Unlike most superconductors, the absence of parity conservation implies that both singlet and triplet pairs coherently exist. Our NMR-data provide a striking confirmation of the coexistence of triplet and singlet pairs with a small coherence peak characteristic of s-wave superconductivity, slowly crossing over to a T3 dependency at low temperatures characteristic of line nodes around the Fermi-surface. Therefore we can classify CePt3Si is a broken parity superconductor, containing a coherent admixture of singlet and triplet Cooper pairs – a new quantum phase of matter.
The discovery of superconductivity in CePt3Si has thus lead to new physics and to a re-examination of our current understanding of these phenomena – it has opened entirely new directions of experimental and theoretical research. As new phases of matter tend to accumulate near a quantum critical point (or a quantum critical point submersed below the superconducting domain), it would be highly desirable to have more examples of parity-violating superconductors and study their NonFermiLiquid behaviour.
It will be our challenge in chemistry for the next years to design novel materials under these constraints, to find them in proper combination of elements and to characterize their properties.
The recent discovery of „the first Ge-based Skutterudite: Superconducting BaPt4Ge12 “ connects research of strongly correlated electron systems with novel functions in thermoelectric materials.

Nano-structured thermoelectrica – Quantum dots and quantum wires

Our recent studies of skutterudites as well as strongly correlated f-electron systems based on rare-earth elements have revealed extraordinary high potential for thermoelectric (TE) applications. Remarkable materials are Kondo semiconductors and filled skutterudites both containing Ce- and Yb- ions with unstable 4f-electrons. In these systems, the 4f-electrons primarily define the entropy, while the s- and p-electrons carry the charge. Therefore, unlike in conventional semiconductors without 4f-electrons, giant thermopower of more than 150 μV/K concomitantly occurs with rather low electrical resistivities below 1 mΩcm. Furthermore, the thermal conductivity in filled skutterudites is unusually low due to “rattling modes” of filler atoms modifying the phonon spectrum. Particularly the reduction to nanosize of the material carrying the thermoelectric currents in quantum dots and quantum wires drives the system to a Luttinger Liquid promising a remarkable gain in the TE figure of merit.

These research activities for materials design exploiting the quantum-confinement will combine high level experimental expertise with Functional Density Calculations within various institutions in chemistry and physics of the Univ. Wien with the goal to provide the knowledge for novel high efficiency thermoelectric materials to Austrian industry.

   

Bioinorganic Chemistry

(Department of Inorganic Chemistry, Working Group Prof. Keppler)

Focus is on Bioinorganic Chemistry, Medicinal Chemistry, Synthetic Chemistry, Analytical Chemistry, Bioanalytics and Cell Biology, mostly under the aspect of the development of novel tumor therapeutics. There is spezial interest on the development and optimization of Multifunctional Nanoparticles for Clinical Molecular Imaging and Therapy. The group has successfully been contributing to this field for several years. There are two new therapeutics under clinical research which have been developed in this group.

   

Bioimprinting of Polymers and Sol−Gel Phases for Chemical Sensorics

(Department of Analytical Chemistry and Food Chemistry, 
Chair of Chemical Sensors and Optical Spectrometry,
Working Group Prof. F.L. Dickert and Prof. P.A. Lieberzeit)

The main goal of the group is to generate highly functional materials by patterning and structuring both surfaces and bulk materials for application in molecular recognition and bio-recognition. Templates for doing this cover the size range from 0.5 nm to 25 µm including e.g. small molecules, proteins, viruses, cells and pollen. Overall, our strategy is to substitute natural immunoglobulins and cells by artificial plastic replicas. The re-inclusion of molecules and bio-analytes is preferably achieved by a label free detection via high-frequency mass-sensitive devices with fundamental frequencies covering the range from 10 MHz to 1 GHz.

Pyrene imprint (template size 0.7 nm)

The smallest functional cavities generated by templating selectively incorporate small molecules from gases and liquids. An example for this are e.g. materials for incorporating pyrene (molecular size 0.7 nm), as shown in the molecular model. 

Imprint of Virus

yeast cells settled in an imprint-layer shown with the AFM

A next step in size are viruses as templates reaching dimensions between 18-300 nm. Again, polymers for selective interaction can be generated and applied as the first rapid analysis tools ever for these species.
On the upper end of the size scale, materials incorporating e.g. yeast cells (5 µm) are accessible, as depicted in the AFM image below showing both empty surface cavities and others occupied by individual cells.
By our sensing strategies, even single interaction events can be detected, as seen in the red-coloured figure in red showing the frequency response occurring by incorporation of a single yeast cell.

yeast effect

In the same way, it is also possible to sense a single HeLa cell by using SAW structures.

Sensor response to a single HeLa cell

By developing our surface strategies we are now at the level to also detect IgGs as antibody by printing the antibodies into nanospherical structures which apply to our surfaces. 

nanoscale biomolecular objects selectively detectable by imprinting technologies

Equipment, 
(Department of Analytical Chemistry and Food Chemistry
Chair of Chemical Sensors and Optical Spectrometry,
Working Group Prof. F.L. Dickert and Prof. P.A. Lieberzeit)

Characterization Techniques   Some Transducer Devices:
- Molecular Spectrometry (UV-VIS,   - QMB
FT-IR, ATR, Fluorescence   - SAW, ID-Tag, STW
Fluorescence Microscopy)   - Optical Systems - SPR
- Impedance Spectrometry    
- AFM, STM, SNOM    
- Optical Systems - SPR    

AFM atom force microscope

   

Sensor Array

   

Measuring cell for aqueous

   

Selected Examples Strategies for Sensor
- PAH Detection - Layer Design
- Oil Degradation Measurements - Self Assembly
- Protein Detection - Molecular Imprinting
- Virus and Cell Detection  

   

Selected Recent Publications
(Department of Analytical Chemistry and Food Chemistry
Chair of Chemical Sensors and Optical Spectrometry,
Working Group Prof. F.L. Dickert and Prof. P.A. Lieberzeit)

  • M. Jenik, A. Seifner, S. Krassnig, K. Seidler, P. A. Lieberzeit, F. L. Dickert, C. Jungbauer, Biosens. Bioelectron. 2009, in press doi:10.1016/j.bios.2009.01.019
  • P. A. Lieberzeit, A. Afzal, A. Rehman, F. L. Dickert, Anal. Bioanal. Chem. 127 (2007) 132-136.
  • O. Hayden, P. A. Lieberzeit, D. Blaas, F. L. Dickert, Adv. Funct. Mater. 16 (2006) 1269-1278.
  • O. Hayden, K.-J. Mann, S. Krassnig, F. L. Dickert, Angew. Chem. Int. Ed. 45 (2006) 2688-2691.
  • F. L. Dickert, P. A. Lieberzeit, P. Achatz, C. Palfinger, M. Fassnauer, E. Schmid, W. Werther, G. Horner, Analyst 129 (2004) 432-437.
  • F. L. Dickert, O. Hayden, Anal Chem 74 (2002) 1302-1306.
  • O. Hayden, F. Dickert, Adv Mater 13 (2001) 1480-1483.
  • F. L. Dickert, W. Greibl, A. Rohrer, G. Voigt, Adv Mater 13 (2001) 1327-1330.

Patents include:

  • F.L. Dickert, P. Forth, P. Lieberzeit, G. Voigt, K.D. Marquadt, Oil Quality Sensor. International patent No. WO 98/19156 (1998).
  • F.L. Dickert, W. Greibl, P. Lieberzeit, G. Voigt, K.D. Marquadt, Oil Quality Sensor and Method for Producing the Same. International patent No. WO 00/50894 (2000).

   

Synthesis of Nano-Sized Powders and Solders

(Department for Inorganic Chemsitry/Materials Chemistry, 
Working Group Prof. Ipser)

Synthesis of Nano-Sized Powders of Intermetallic Compounds

Intermetallic compounds serve as alloys for special applications in an ever increasing extent. At the same time nano-sized materials with their particular properties are offering a wide field of new developments in materials science and technology. Thus research on the synthesis of nano-crystalline metals and intermetallic compounds is required. A key route is the decomposition of appropriate precursors, e.g. inorganic compounds, complexes or gels. 

Our group has successfully synthesized nano-crystalline powders of GaNi3 and GaNi. These two compounds are the homologues of AlNi3 and AlNi, which are frequently used as high temperature and corrosion resistant super alloys, e.g. in turbines.

The first picture shows a ball-milled powder from a bulk sample of GaNi3. It has grey colour and can be removed from the paper without leaving traces. The same compound, synthesized via thermal decomposition of co-precipitated acetylacetonato complexes in reducing atmosphere is shown at the second picture. It is black and invades the fine pores of the paper. A similar effect can be seen at the last image. A glass vial, filled with the nano-sized powder of GaNi3 on the left: the glass is toned by the black particles in the micro pores of the glass (see also the borderline on the upper side, caused by the lid of the vial); compare with the clean vial on the right side.

A glass vial, filled with the nano-sized powder of GaNi3 on the left: the glass is toned by the black particles in the micro pores of the glass (see also the borderline on the upper side, caused by the lid of the vial); compare with the clean vial on the right side.

   

Interaction of Sn-based Solders with Ni(P) substrates

Today’s mass soldering techniques are highly demanding in terms of joint quality, reliability and cost. Along with further miniaturization higher lead-densities are required in less space, for which the so-called ball grid array (BGA) provides a convenient solution and can thus e.g. be found in mobile phones. Though simple at first sight, soldering is in no way a straight forward process with a chemical reaction taking place between the solder alloy and the contact material. In BGA assemblies the most cost-effective surface coating is done by a process called electroless plating, where an amorphous Ni-layer is autocatalytically deposited on Cu. As Na2HPO2 is used as a reducing agent, P is co-deposited in this layer. This Ni(P) layer is itself protected by a thin Au-layer resulting in the so-called electroless Ni-gold (ENIG) layer.

Knowledge of the chemical reaction for a certain combination of solder and contact material is essential, because the reaction product is a layer of brittle intermetallic compounds (IMC). Since the transition to lead-free solders introduced high Sn-containing solders, the research focus has shifted towards this IMC formation. These solders are known to form particularly large IMC layers which are detrimental to the joint quality.
During the reaction between such Sn-based solders and ENIG surfaces Ni-atoms diffuse via the interface to react with the solder and form Ni3Sn4 and/or (Cu,Ni)6Sn5 phases. This Ni out-diffusion leaves a P-enriched layer behind that crystallizes into Ni3P. All of the mentioned compounds are extremely brittle and make the joint vulnerable to mechanical shock. During the lifetime of the component it may be furthermore subjected to high working temperatures, which results in further growth and formation of additional compounds, e.g. ternary Ni-P-Sn compounds.

The aim of the current research project is the investigation of the ternary Ni-P-Sn phase diagram to provide basic material information on ternary phases that can be formed in a solder joint. Within the scope of this work new investigations in the limiting binary systems Ni-P and P-Sn are carried out, too.

In the ternary system the phase equilibria were determined at various temperatures between 200 °C and the melting range. Even if soldering is done at comparatively low temperatures it is necessary to investigate the full temperature range in order to achieve a consistent description.
Work on the phase diagram also revealed the existence of a hitherto unknown ternary compound, Ni21P6Sn2, that crystallizes in the C6Cr23 structure type well known from steel technology.

Experimental difficulties caused by the volatility of P have so far hampered the investigation in the Sn- and P-rich parts of the phase diagram. It is therefore desirable to enhance the experimental phase diagram information by semi empirical modelling. The required thermodynamic properties are investigated by calorimetric methods and by the isopiestic method (vapour pressure method).

 

 

 

 

Lead-free Solders for a Cleaner

Why lead-free solders?
• about 6 mio t scrap from electronics in industrialized nations (in 2000) 
• about 200 mio mobile phones in use in the USA (in 2005) (which results in 65,000 t electronic scrap per year (including charging devices) 
• about 315 mio computers discarded between 1997 and 2004, resulting in about 550,000 t of lead
Where would all that lead from the solders go?
• Possibly a lot of it would go into garbage dumps – and from there into the groundwater – and from there straight into the food chain … 
Possible alternatives (currently in use):
• Tin-Silver (e.g. Sn-3.5Ag)
• Tin-Copper (e.g. Sn-0.7Cu)
• Tin-Silver-Copper 
(„SAC“, e.g. Sn-3.7Ag-0.7Cu)
• ...

Development of new lead-free solders
• Search for possible high-temperature solders (with melting temperatures above 250°C)
• Tin-Zinc-X (possible high-temperature solders for the future; 
e.g. Sn-9Zn-0.5X) 
• Ag-Bi-X; Sn-Sb-X, Sn-Al-X, …
Development of new contacting methods
• Transient Liquid Bonding (TLB) Method

Bismuth for bonding nickel contacts
Tin for bonding copper contacts

Current Research Topics (Examples)
Example 1: What happens if Sn-Ag-Cu Solders react with Ni Substrates? 

• Phase equilibria of binary and ternary systems:
e.g. Ag-Ni, Ni-Sn; Ag-Ni-Sn, Cu-Ni-Sn
• Thermochemical data for binary and ternary systems:
e.g. enthalpies of mixing of liquid alloys, enthalpies of formation of solid intermetallic compounds, partial thermodynamic properties in the solid and the liquid state
• Calculation of optimized phase diagrams

Ag-Ni-Sn: isothermal section 700°C
Example 2: What happens if any Sn-based solder reacts with phosphorus-containing Ni substrates?

Phosphorus content from chemical method of nickel deposition (“Electroless Nickel”), i.e. reduction of nickel solution with hypophosphites

• Phase equilibria in the Ni-Sn, Ni-P, P-Sn, and Ni-P-Sn system
• Partial thermodynamic properties in Ni-P and Sn-P
• Calculation of optimized phase diagrams

Example 3: How reliable are Sn-Ag/Cu and Sn-Ag/Ni solder joints? 
• Tensile strength of model solder joints
• Shear strength of model solder joints
• Stress relaxation in model solder joints

->  In all cases appearance of a clear size effect (“Constraint Effect”), i.e. small solder joints are stronger but much more brittle

Example 4: Development of Nanosolders to reduce melting temperatures (planned)
• Sb-Sn-X nanosized solder powders by chemical reduction methods
• Characterization of nanosolders (particle size, melting temperatures, phase composition, …)

   

Structure and dynamics of biomolecules

(Computational Biological Chemistry, Working Group Prof. Steinhauser)

  • Structure and Dynamics of Biomolecules in Solution using Molecular Dynamics
  • Dielectric properties of proteins in solution
  • Investigation of NMR relaxation by Molecular Dynamics

Institut für Physikalische Chemie
Universität Wien

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