Organic and Metal Chalcogenide-Based Light Absorbers for Assembling with Microbes—A Solar to Chemical Approach Through Living Microbial Photo Hybrids

Rapidly increasing carbon footprint in the atmosphere is a global pressing challenge that has direct implications for climate change. Solar-to-chemical conversion is a promising way of renewable energy generation with the advantage of storing intermittent solar energy in the form of storable chemical bonds. To demonstrate this, we propose a semi-artificial way of photosynthesis by incorporating anaerobic bacteria over a synthetic light-absorbing material to form a biohybrid system. This biohybrid can convert CO₂ and sunlight into value-added chemicals and fuels through photo-assisted microbial catalysis. We are trying to achieve this through the process called microbial photosynthesis. This happens through bacteria hacking the photochemical activity of the light-absorbing semiconductor, that’s by capturing the reducing equivalents (electrons or hydrogen) after photoexcitation to undergo the microbe’s metabolism converting CO₂ into chemicals and fuels. Therefore, the photocatalytic performance of the light-absorbing semiconductor is crucial in the process that the overall performance of the biohybrid is majorly relied on it. We have been working on two classes of materials for Integrating with bacteria in microbial photosynthesis, those are nanocomposite metal chalcogenide and organic semiconductor. Both these materials are proven to be biocompatible with added benefits such as solution processibility, low toxicity, tuneable surface Interaction and cheap fabrication from earth-abundant elements. Cu₂ZnSnS₄ is a semiconducting quaternary metal chalcogenide we have been working on for Integrating with bacteria, this material has a narrower band gap of 1.5eV and a large optical coefficient. On Integrating with an anaerobic microbe <i>Sporomusa ovata</i>, the biohybrid has performed microbe-assisted photocatalytic CO₂ reduction into acetate and ethanol in appreciable yield with long-term stability. In parallel, nitrogen-containing linear poly (phenylic) organic semiconductor is another light-absorbing material we have been hybridizing with microbes. On Integrating with methanogenic/acetogenic bacteria, these materials have performed CO₂to chemical conversion with appreciable yield. Considering the optical/spectroscopic relevance of this material, we are Investigating the enigmatic electron transfer mechanism happening between the light absorber and microbe through photoluminescence (PL) spectroscopy and transient absorption spectroscopy (TAS).