Periodic Report Summary - BIOMOLECTRONIC (Biomolecular electronics and electrocatalysis)
The aim of the joint exchange programme BIOMOLECTRONIC is to strengthen existing successful scientific collaborations between the partners and to foster a long-term network activity through short period staff and student exchanges. The programme involves three well-established research groups in the European Union (EU) (Southampton and Galway) and in an international cooperation third partner country (ICPC) third country with science and technology (S&T) agreement (Conicet in Buenos Aires, Argentina). The participation of students (early stage researchers) undergoing doctorate (PhD) training and post-doctoral fellows as well as established scientists (experienced researchers) from two partners in Europe and a partner in Argentina will provide a basis for long-term research and training cooperation through a coordinated programme of visits. It is expected that this will extend the network activity to include all of the group members of the participants who will get to know each others experience and perspectives.
The activities in the three research partner groups will permit familiarisation with complementary developments in chemistry, spectroscopy and electrochemistry, instrumentation and theory / molecular simulation.
The three partner groups of this joint exchange programme share a solid experience in electrochemistry and bioelectrochemistry, with particular emphasis on the chemical modification of surfaces with molecular systems. The joint research proposed is relevant to improved technologies and medical devices for higher safety and improved quality of life of consumers and EU citizens and potentially to the greater understanding of biofuel cell systems which could contribute to the generation of clean energy.
The programme concentrates on four topic areas:
1. Tailoring redox complexes for catalysis
In biosensors and biofuel cells, the redox potential of the molecular system, either direct electron transfer to molecules tethered chemically to the surface or mediated by redox relays, is a crucial parameter. For biosensors, the suitable choice of redox potential may eliminate interferences, while in electrocatalysis for biofuel cells the redox potential of the mediator and enzyme determine the voltage and power that the device can deliver. Another important factor that determines the current (amperometric response in a biosensor or power in a biofuel cell) is enzyme kinetics. At present even for very efficient redox enzymes such as fungal laccase which can operate at a higher electrode potential than noble metal catalysts for oxygen reduction, the maximum current density is limited by enzyme kinetics both for direct electron transfer as well as for mediated electrocatalysis. The rational design of mediated biomolecular devices with improved performance requires the ability to build electrodes with fine control of the redox potential of mediator.
2. Covalent surface modification
For practical applications, the ability to modify the surface properties of the electrode by covalent attachment of redox and other groups is an important step. The Southampton group have developed a flexible methodology based on the combination of electrochemical immobilisation of linker species followed by subsequent modification using solid phase synthesis methodologies to build libraries of modified electrodes which can be screened by high-throughput electrochemical methods. The advantage of this approach is that it allows the effects of mediator structure, method of immobilisation and surface structure to be explored in a coherent way for the first time and is ideally suited as a technique for the optimisation of electrode surfaces for bioelectrochemical applications.
3. Spectroscopy and spectroelectrochemistry
Once the electrode surface is modified with small redox molecules, enzymes or other biomolecules as designed it is essential to verify that these molecules are attached to the surface with the correct orientation, interaction and electronic coupling that makes it possible to generate electrical signals through electrochemical reactions at the interface.
In this direction, the group in Southampton has developed powerful platforms for the spectroscopic interrogation of these molecular systems, such as sphere segment void nanostructured surfaces designed to give high surface enhancements in surface-enhanced Raman spectroscopy (SERS). These Raman and resonance Raman (RR) scattering techniques will be complemented with quantitative polarisation modulation infrared reflection absorption spectroscopy (PM-IRRAS) recently developed at in Buenos Aires. This spectroscopic technique under electrochemical conditions provides evidence of the molecular orientation at metal surfaces at the submonolayer level. Combining these two spectroscopic techniques will be a powerful way to study the electrode surface.
4. Layer-by-Layer (LbL) films for electrocatalysis
The Conicet group in Buenos Aires has the ability to build thin multilayer films by LbL self-assembly of redox polyelectrolytes carrying as redox moieties the osmium complexes described above and this technology is also under development in Galway who have particular expertise in the design and synthesis of osmium complexes as redox mediators.
The combination of the expertise in the three partner groups offers a unique opportunity to tackle difficult problems in molecular electronics and electrocatalysis in areas of internationally leading science in the three laboratories. This joint exchange program will benefit the early stage researchers that will be trained in these converging scientific aspects, the postdoctoral research associates that will bring their own experience while acquiring those developed in the host laboratory and will benefit the EU since the technologies covered are within the targets of the Seventh Framework Programme (FP7).
Work so far has contributed to these aims through the exchange of early stage researchers and experienced researchers who have been involved in collaborative research on the synthesis and electrochemical characterisation of osmium complexes designed as mediators for laccase. These electrodes have been characterised by a range of techniques including in situ scanning tunnelling microscope (STM) and SER(R)S. In addition early stage researchers and experienced researchers have received training and experience in the specialised techniques of in situ Fourier transform infrared spectroscopy (FTIR), and particularly PM-IRRAS, and synchrotron studies of electrode surfaces through exchanges between the three partners.
These studies have led to increased and on-going collaboration between the three research centres and their different research activities. The visits have also enabled the early stage researchers to participate in scientific discussions with student and staff at the host institutions and this has broadened their scientific perspective and experience.
The expected final outcomes of the programme are the enhanced training and expertise of the early stage researchers and the experienced researchers as well as greater insight and understanding into the factors that control the electrocatalytic performance of the bioelectrode and electrocatalyst surface.
The activities in the three research partner groups will permit familiarisation with complementary developments in chemistry, spectroscopy and electrochemistry, instrumentation and theory / molecular simulation.
The three partner groups of this joint exchange programme share a solid experience in electrochemistry and bioelectrochemistry, with particular emphasis on the chemical modification of surfaces with molecular systems. The joint research proposed is relevant to improved technologies and medical devices for higher safety and improved quality of life of consumers and EU citizens and potentially to the greater understanding of biofuel cell systems which could contribute to the generation of clean energy.
The programme concentrates on four topic areas:
1. Tailoring redox complexes for catalysis
In biosensors and biofuel cells, the redox potential of the molecular system, either direct electron transfer to molecules tethered chemically to the surface or mediated by redox relays, is a crucial parameter. For biosensors, the suitable choice of redox potential may eliminate interferences, while in electrocatalysis for biofuel cells the redox potential of the mediator and enzyme determine the voltage and power that the device can deliver. Another important factor that determines the current (amperometric response in a biosensor or power in a biofuel cell) is enzyme kinetics. At present even for very efficient redox enzymes such as fungal laccase which can operate at a higher electrode potential than noble metal catalysts for oxygen reduction, the maximum current density is limited by enzyme kinetics both for direct electron transfer as well as for mediated electrocatalysis. The rational design of mediated biomolecular devices with improved performance requires the ability to build electrodes with fine control of the redox potential of mediator.
2. Covalent surface modification
For practical applications, the ability to modify the surface properties of the electrode by covalent attachment of redox and other groups is an important step. The Southampton group have developed a flexible methodology based on the combination of electrochemical immobilisation of linker species followed by subsequent modification using solid phase synthesis methodologies to build libraries of modified electrodes which can be screened by high-throughput electrochemical methods. The advantage of this approach is that it allows the effects of mediator structure, method of immobilisation and surface structure to be explored in a coherent way for the first time and is ideally suited as a technique for the optimisation of electrode surfaces for bioelectrochemical applications.
3. Spectroscopy and spectroelectrochemistry
Once the electrode surface is modified with small redox molecules, enzymes or other biomolecules as designed it is essential to verify that these molecules are attached to the surface with the correct orientation, interaction and electronic coupling that makes it possible to generate electrical signals through electrochemical reactions at the interface.
In this direction, the group in Southampton has developed powerful platforms for the spectroscopic interrogation of these molecular systems, such as sphere segment void nanostructured surfaces designed to give high surface enhancements in surface-enhanced Raman spectroscopy (SERS). These Raman and resonance Raman (RR) scattering techniques will be complemented with quantitative polarisation modulation infrared reflection absorption spectroscopy (PM-IRRAS) recently developed at in Buenos Aires. This spectroscopic technique under electrochemical conditions provides evidence of the molecular orientation at metal surfaces at the submonolayer level. Combining these two spectroscopic techniques will be a powerful way to study the electrode surface.
4. Layer-by-Layer (LbL) films for electrocatalysis
The Conicet group in Buenos Aires has the ability to build thin multilayer films by LbL self-assembly of redox polyelectrolytes carrying as redox moieties the osmium complexes described above and this technology is also under development in Galway who have particular expertise in the design and synthesis of osmium complexes as redox mediators.
The combination of the expertise in the three partner groups offers a unique opportunity to tackle difficult problems in molecular electronics and electrocatalysis in areas of internationally leading science in the three laboratories. This joint exchange program will benefit the early stage researchers that will be trained in these converging scientific aspects, the postdoctoral research associates that will bring their own experience while acquiring those developed in the host laboratory and will benefit the EU since the technologies covered are within the targets of the Seventh Framework Programme (FP7).
Work so far has contributed to these aims through the exchange of early stage researchers and experienced researchers who have been involved in collaborative research on the synthesis and electrochemical characterisation of osmium complexes designed as mediators for laccase. These electrodes have been characterised by a range of techniques including in situ scanning tunnelling microscope (STM) and SER(R)S. In addition early stage researchers and experienced researchers have received training and experience in the specialised techniques of in situ Fourier transform infrared spectroscopy (FTIR), and particularly PM-IRRAS, and synchrotron studies of electrode surfaces through exchanges between the three partners.
These studies have led to increased and on-going collaboration between the three research centres and their different research activities. The visits have also enabled the early stage researchers to participate in scientific discussions with student and staff at the host institutions and this has broadened their scientific perspective and experience.
The expected final outcomes of the programme are the enhanced training and expertise of the early stage researchers and the experienced researchers as well as greater insight and understanding into the factors that control the electrocatalytic performance of the bioelectrode and electrocatalyst surface.