Periodic Reporting for period 1 - SpinBioAnode (Nature’s spin-flipping machine: design of the semiconductor-free biophotoanode)
Reporting period: 2023-05-01 to 2025-04-30
SpinBioAnode (“Nature’s spin-flipping machine: design of the semiconductor-free biophotoanode”) tackles a key weakness of today’s photovoltaic and photo-bioelectrochemical technologies: they depend on scarce, hard-to-recycle semiconductors and lose most of the absorbed photon energy as heat. Bacterial reaction-centre (bRC) proteins already convert light into charge with near-unity quantum yield, yet conventional biohybrid devices extract electrons only after ~70 % of that energy is dissipated, constraining the open-circuit voltage (OCV) to ≈0.5 V. SpinBioAnode exploits an alternative, long-lived triplet state that lies ~1.0 eV above the ground state, theoretically doubling the attainable OCV and paving the way for biodegradable, metal-free solar electrodes.
The project’s overall goal is to build and validate the first energy-efficient, semiconductor-free biophotoanode in which electrons are harvested directly from the triplet state and delivered to an external circuit through a viologen-based redox-polymer hydrogel that also scavenges oxygen and protects the protein matrix. To reach this goal the work is structured around three research objectives:
RO1 – To construct a working biophotoanode utilizing the primary donor triplet as the electron source state
RO2 – To identify photocurrent limitations within the constructed biophotoanode
RO3 – To optimize photocurrent generation by rationally addressing the identified bottlenecks
Pathway to impact
Scientific: deliver the first mechanistic picture of utilization pf a triplet electron transfer in a biohybrid photovoltaic device and provide open kinetic models and spectroelectrochemical protocols for the field.
Technological: establish a blueprint for sustainable photoanodes that can be utilized to power in situ biocatalysis, biosensors etc.
Industrial & economic: offer a route to photovoltaic coatings made entirely from earth-abundant, biodegradable components, lowering material costs and supply-risk barriers for EU SMEs.
Societal & environmental: advance European Green Deal goals by reducing reliance on critical raw materials, easing end-of-life recycling and opening photovoltaic niches where biodegradability and low-waste manufacturing are paramount (e.g. off-grid micro-power in developing regions).
By rewiring nature’s spin-flipping machinery into a protective redox-polymer framework, SpinBioAnode aims to demonstrate a new class of clean, scalable optoelectronic devices and to lay rigorous scientific foundations for their future commercialisation.
The project’s overall goal is to build and validate the first energy-efficient, semiconductor-free biophotoanode in which electrons are harvested directly from the triplet state and delivered to an external circuit through a viologen-based redox-polymer hydrogel that also scavenges oxygen and protects the protein matrix. To reach this goal the work is structured around three research objectives:
RO1 – To construct a working biophotoanode utilizing the primary donor triplet as the electron source state
RO2 – To identify photocurrent limitations within the constructed biophotoanode
RO3 – To optimize photocurrent generation by rationally addressing the identified bottlenecks
Pathway to impact
Scientific: deliver the first mechanistic picture of utilization pf a triplet electron transfer in a biohybrid photovoltaic device and provide open kinetic models and spectroelectrochemical protocols for the field.
Technological: establish a blueprint for sustainable photoanodes that can be utilized to power in situ biocatalysis, biosensors etc.
Industrial & economic: offer a route to photovoltaic coatings made entirely from earth-abundant, biodegradable components, lowering material costs and supply-risk barriers for EU SMEs.
Societal & environmental: advance European Green Deal goals by reducing reliance on critical raw materials, easing end-of-life recycling and opening photovoltaic niches where biodegradability and low-waste manufacturing are paramount (e.g. off-grid micro-power in developing regions).
By rewiring nature’s spin-flipping machinery into a protective redox-polymer framework, SpinBioAnode aims to demonstrate a new class of clean, scalable optoelectronic devices and to lay rigorous scientific foundations for their future commercialisation.
The main work performed within the project can be summarized within those points:
- Prototype electrodes built, but triplet route unproven. Drop-cast films of viologen hydrogels with engineered Rhodobacter sphaeroides reaction centres showed clean, reversible viologen redox chemistry; however, photocurrents stayed in the nanoampere range and fell under triplet-enhancing conditions, ruling out the envisaged triplet-based mechanism.
- Primary bottleneck isolated. Transient-absorption spectroscopy on protein–dendrimer solutions revealed that viologen dendrimers shorten the P-triplet lifetime without producing detectable reduced-viologen signals, indicating inefficient - or immediately recombining - electron injection from the triplet state into the polymer.
- Contingency study was performed in the scope of not delivering significant photocurrents from the triplet pathway. The oxygen protection mechanism of viologen polymers was studied in more details with the [FeFe] hydrogenase as the sensitive protein. A 3-D confocal‐fluorescence method quantified the oxidation-front thickness versus time and pH, results now drafted for publication.
- Side-project arised. An autocatalytic reactivation behaviour in polymer-hydrogenase films were observed. This lead to topics for work of Master's students supervised by the researcher and may lead to additional publications in the future.
Overall outcome
Although a functional triplet-driven biophotoanode has not yet been realised, the project has:
- Pinpointed electron injection from the protein triplet to the viologen network as the critical obstacle, but without any success in improving it with currently available tools.
- Generated versatile imaging and spectroelectrochemical tools that strengthen the host laboratory’s capacity and open new lines of publishable research.
These tangible assets position the researcher to revisit the original objectives with a far more focused strategy for the future projects.
- Prototype electrodes built, but triplet route unproven. Drop-cast films of viologen hydrogels with engineered Rhodobacter sphaeroides reaction centres showed clean, reversible viologen redox chemistry; however, photocurrents stayed in the nanoampere range and fell under triplet-enhancing conditions, ruling out the envisaged triplet-based mechanism.
- Primary bottleneck isolated. Transient-absorption spectroscopy on protein–dendrimer solutions revealed that viologen dendrimers shorten the P-triplet lifetime without producing detectable reduced-viologen signals, indicating inefficient - or immediately recombining - electron injection from the triplet state into the polymer.
- Contingency study was performed in the scope of not delivering significant photocurrents from the triplet pathway. The oxygen protection mechanism of viologen polymers was studied in more details with the [FeFe] hydrogenase as the sensitive protein. A 3-D confocal‐fluorescence method quantified the oxidation-front thickness versus time and pH, results now drafted for publication.
- Side-project arised. An autocatalytic reactivation behaviour in polymer-hydrogenase films were observed. This lead to topics for work of Master's students supervised by the researcher and may lead to additional publications in the future.
Overall outcome
Although a functional triplet-driven biophotoanode has not yet been realised, the project has:
- Pinpointed electron injection from the protein triplet to the viologen network as the critical obstacle, but without any success in improving it with currently available tools.
- Generated versatile imaging and spectroelectrochemical tools that strengthen the host laboratory’s capacity and open new lines of publishable research.
These tangible assets position the researcher to revisit the original objectives with a far more focused strategy for the future projects.
Key scientific and technological results
• Mechanistic breakthrough. Transient-absorption spectroscopy showed that viologen dendrimers shorten the lifetime of the primary-donor triplet without forming detectable reduced-viologen signals, unambiguously isolating electron injection from the triplet state as the sole kinetic bottleneck in triplet-based bioanodes.
• First 3-D redox imaging of hydrogel electrodes. A confocal-fluorescence workflow was pioneered to visualise, in real time, the thickness and growth kinetics of the oxygen-protection layer inside viologen hydrogels—tooling that was previously unavailable to the bioelectrochemistry community.
• Control of enzyme-driven autocatalysis in polymer films. Spatially resolved microscopy revealed patterned, self-amplifying reactivation fronts in [FeFe]-hydrogenase hydrogels, opening a new line of research into enzymatic signal amplification for sensing and catalysis that can be controlled via the film properties.
• Mechanistic breakthrough. Transient-absorption spectroscopy showed that viologen dendrimers shorten the lifetime of the primary-donor triplet without forming detectable reduced-viologen signals, unambiguously isolating electron injection from the triplet state as the sole kinetic bottleneck in triplet-based bioanodes.
• First 3-D redox imaging of hydrogel electrodes. A confocal-fluorescence workflow was pioneered to visualise, in real time, the thickness and growth kinetics of the oxygen-protection layer inside viologen hydrogels—tooling that was previously unavailable to the bioelectrochemistry community.
• Control of enzyme-driven autocatalysis in polymer films. Spatially resolved microscopy revealed patterned, self-amplifying reactivation fronts in [FeFe]-hydrogenase hydrogels, opening a new line of research into enzymatic signal amplification for sensing and catalysis that can be controlled via the film properties.