Unlocking interfacial electron transfer in biophotoelectrochemical processes: Role of extracellular polymeric substances in aquatic environments

The biophotoelectrochemical process (BPECs) integrates the light-absorbing capabilities of nano-semiconductors with the catalytic efficiency of microorganisms, demonstrating significant potential for the development, utilization, transformation, and ecological restoration of water resources. In aquatic environments, extracellular polymeric substances (EPS) serve as a critical interfacial barrier between microorganisms and semiconductor materials, with the underlying electron transfer mechanisms playing a pivotal role in determining the efficiency of bio-photochemical reactions. Despite their importance, the rapidity and complexity of the electron transfer process within EPS pose significant challenges to a comprehensive understanding of BPECs. In this study, an in-situ characterization strategy was employed to rapidly and accurately analyze the components and pathways of photogenerated electron transfer involving EPS at interfaces. The findings indicate that EPS significantly accelerates the transfer of photogenerated electrons within BPECs. Specifically, proteins and redox-active substances within EPS act as efficient conduits for electron transfer, accounting for up to 84.2% of the increased speed in electron transfer rates at bio-abiotic interfaces. Conversely, polysaccharides within EPS impede the electron transfer process but serve as substrates that facilitate methane (CH4) production. The in-situ characterization approach used in this research provides valuable insights into the interfacial electron transfer mechanisms of EPS in BPECs, emphasizing their relevance in aquatic environments. This study establishes a theoretical framework for designing high-performance BPECs, with significant implications for the energy utilization of water resources and the transformation of water pollutants.

Electricity-powered cryptic CO2 fixation pathway in heterotrophic Shewanella oneidensis for acetate synthesis

Microbial electrosynthesis of CO2 is a sustainable carbon neutral technology. Although known for its diverse and efficient extracellular electron transfer (EET) characteristics, the bacteria of Shewanella genus have never been reported for use in electrosynthesis of multi-carbon chemicals. Herein, the electricity-powered conversion of CO2 to acetate was achieved under ammonium regulation for the first time in the model strain (Shewanella oneidensis MR-1), due to the activation of its intrinsic reductive glycine pathway. A high electron flux from cathode into MR-1 was achieved through the unique electron uptake pathway mediated by endogenous iron release, biomineralization of iron oxide, and inherent EET pathways. Consequently, MR-1 delivered an acetate production rate of 78.6 ± 4.2mmol m-2 d-1, significantly surpassing those of previously reported electro-autotrophic acetogens under similar operating conditions. Our findings not only provide a novel platform for one-carbon biorefinery, but also prompt recognition to the complexity of EET and CO2 fixation.

Recent Progress in Developing Conjugated Polymer-Microorganism Biohybrids for Semi-Artificial Photosynthetic Energy Conversion

Semi-artificial photosynthesis, which merges the precision of synthetic materials with the catalytic versatility of biological systems, offers a transformative route to solar-driven chemical fuel production and sustainable energy conversion. Conjugated polymers, with their high molar absorption coefficients, broad spectral responsiveness, and tunable semiconducting properties, have emerged as key components in advancing semi-artificial photosynthetic biohybrids. Their capacity for targeted surface modification not only facilitates enhanced interfacing with biological catalysts but also optimizes charge transfer across the bio-synthetic interface. This review traces the evolution of conjugated polymer-based biohybrids, highlighting recent advancements that extend microbial light harvesting, support cellular resilience against environmental stress, and optimize charge transfer via precise structure-activity relationships. Furthermore, this review explores the challenges and opportunities in this field, offering a roadmap for the design of durable and high-performance biohybrid systems. Through the integration of conjugated polymers and microorganisms, this review outlines a strategic approach for solar-driven chemical energy conversion, paving the way for eco-friendly energy solutions.

Identification of stay-green candidate gene TaTRNH1-3B and development of molecular markers related to chlorophyll content and yield in wheat (Triticum aestivum L.)

Functional stay-green characteristic is closely associated with delayed loss in photosynthetic function and increased crop yield. However, the development and application of functional molecular markers based on stay-green-related genes are limited. This study compared and analyzed the differences of SPAD values, photosynthetic parameters, fluorescence parameters, and antioxidant enzyme activities at 0, 10, 18, 22, 26, 30 and 34 days after anthesis, as well as agronomic traits at mature stage between a stay-green line, Tailv113 (TL113), and a non-stay-green cultivar, Jinmai39 (JM39). The results showed that TL113 had higher photosynthetic capacity, photosynthetic efficiency, antioxidant capacity and yield than JM39. Subsequently, a comparative transcriptome analysis was conducted on TL113 and JM39 at 0, 26, and 30 days after anthesis. Analysis showed that senescence-associated co-expressed genes (SCEGs) and stay-green-associated differentially expressed genes (SDEGs) jointly affected wheat leaf senescence, while SDEGs played an important role in the stay green differences between TL113 and JM39. By analyzing the SNP sites of the SDEGs from transcriptome sequencing, a nsSNP was found in the TaTRNH1-3B sequence between TL113 and JM39. Further analyzing the resequencing data published in the Wheat Union database, four linked SNP sites were identified in TaTRNH1-3B, which formed two haplotypes, TaTRNH1-3B-Hap1 and TaTRNH1-3B-Hap2. Based on the SNP at 373 bp (A/G), a CAPS molecular marker, TaTRNH1-3B-Nla III-CAPS, was developed to distinguish allelic variations (A/G). Association analysis between TaTRNH1-3B allelic variation and agronomic traits found that the accessions possessing TaTRNH1-3B-Hap1 (A) exhibited significantly higher SPAD values than those possessing TaTRNH1-3B-Hap2 (G) in 6 of 10 environments at the jointing stage and in 7 of 10 environments at the grain filling stage in Beijing. Similarly, the accessions possessing TaTRNH1-3B-Hap1 (A) exhibited significantly higher chlorophyll contents and yield than those possessing TaTRNH1-3B-Hap2 (G) in 3 environments in Taigu. Additionally, lines with TaTRNH1-3B-Hap1 (A) displayed higher SPAD values at 0, 15, and 20 days after anthesis in the two BC3F3 populations than those with TaTRNH1-3B-Hap2 (G). These results suggest that TaTRNH1-3B is associated with the stay-green and yield traits in wheat, and TaTRNH1-3B-Hap1 is a favorable stay-green haplotype. The newly developed molecular marker, TaTRNH1-3B-Nla III-CAPS, provide valuable information for wheat genetic improvement of stay-green and high-yield traits, and can be used to marker-assisted selection breeding.

Biological Hybrid Systems Based on Photocatalysts to Drive the Conversion of CO2 into High-Value Compounds

Artificial photosynthetic biohybrid systems possess the remarkable ability not only to convert solar energy into chemical energy but also to store this energy in the form of organic matter. By leveraging this system, we hold the promise of achieving sustainable energy utilization and chemical production. This review comprehensively summarizes artificial photosynthetic biohybrid systems consisting of metal sulfides, noble metals, quantum dots, composite photocatalysts, and conjugated polymers of organic semiconductor materials with microorganisms and provides a comprehensive overview of examples of artificial photosynthetic biohybrid systems converting CO2 into high-value compounds and a summary of the relevant devices that are currently available. Additionally, the review discusses the challenges and future development trends related to artificial photosynthetic biohybrid systems.

Porous CeO2 nanozyme with visible-light-enhanced catalase-mimicking activities by ligand-to-metal charge transfer

Nanozymes are promising synthetic alternatives to natural enzymes owing to their unique physical and chemical properties, but improving their thermocatalytic activity often involves complex procedures. This study introduces a light-induced approach to enhance the catalytic activity of facilely prepared porous cerium oxide ( P - CeO 2 ) nanozymes. Under visible light irradiation, the catalytic efficiency ( k c a t / K m ) of the P - CeO 2 more than doubles compared to its thermocatalytic efficiency. Spectroscopic analyses reveal that this enhancement stems from a ligand-to-metal charge transfer (LMCT) band, arising from peroxide species adsorbed on the P - CeO 2 surface. As a practical demonstration, P-CeO2 exhibits visible-light enhanced scavenging of reactive oxygen species (ROS) in vitro. Overall, this study provides new mechanistic insights of using LMCT-induced visible light catalysis for the improvement of catalytic activity of light-responsive nanozymes.

Modulating product selectivity in lignin electroreduction with a robust metallic glass catalyst

Converting the lignin into value-added chemicals and fuels represents a promising way to upgrade lignin. Here, we present an effective electrocatalytic approach that simultaneously modulates the depolymerization and hydrogenation pathways of lignin model compounds within a single reaction system. By fine-tuning the pH of the electrolyte, we achieve a remarkable shift in product selectivity, from acetophenone (with selectivity >99%) to 1-phenylethanol (with selectivity >99%), while effectively preventing over-hydrogenation. The robust metallic glass (MG) catalyst, endowed with an amorphous structure, demonstrates high stability, activity, and full recyclability across over 100 consecutive cycles in ionic liquid electrolytes. The relatively strong affinity of the MG catalyst for the substrate during the initial reaction stage, in conjunction with its weaker binding to the phenolic product, as the reaction progresses, creates a delicate balance that optimizes substrate adsorption and product desorption, which is pivotal in driving the cascade hydrogenation process of acetophenone. This work opens versatile pathways for lignin upgrading through integrated tandem reactions and expands the scope of catalyst design with amorphous structures.

Host-Guest Approach to Enhancing Photocatalysis via Photoinduced Energy and Electron Transfer from a Photoactive Triphenylamine-Based Metal-Organic Cage to Bound Guests

The host-guest strategy presents an ideal way to construct versatile supramolecular systems that mimic the structure and functionality of natural enzymes and, therefore, achieve efficient chemical conversions. An emissive triphenylamine-based cage-like host donor was constructed as an energy or electron donor to achieve efficient photoinduced energy or electron transfer (PEnT or PET) by encapsulating the energy or electron acceptor into the cavity of the cage. The host-guest complexes, which served as enzyme-mimicking supramolecular systems, were successfully used as photocatalysts for the selective aerobic oxidation of sulfides and the efficient photocatalytic reduction of aryl halides with high reduction potentials. This work details a promising approach for creating a host-guest system via a host-guest encapsulation strategy to enhance the efficiency of the PEnT or PET process. The resulting designed artificial supramolecular systems achieve efficient chemical conversions by mimicking the structure and functionality of natural enzymes.

Harnessing Near-Infrared Light for Enhanced Solar Hydrogen Production from Escherichia coli Interfaced with Biocompatible Low-Bandgap Conjugated Polymer Nanosheets

The efficient conversion of solar energy into clean hydrogen fuel presents a promising pathway for sustainable energy production. However, utilizing the full solar spectrum, particularly the near-infrared (NIR) region, remains underexplored in photosynthetic biohybrid systems. In this study, biocompatible, low-bandgap conjugated polymer nanosheets (PyTT-tBAL-HAB) are developed to integrate with non-photosynthetic, non-genetically engineered Escherichia coli (E. coli) for enhanced solar-driven biological hydrogen production. The PyTT-tBAL-HAB nanosheets exhibit unique NIR light absorption properties. Integrating these nanosheets with E. coli facilitates efficient electron transfer, resulting in a 1.96-fold increase in hydrogen production rate under NIR light. Consequently, this photosynthetic biohybrid system achieves a quantum efficiency of 18.36% at 940 nm. This study demonstrates the potential of using low-bandgap conjugated polymer nanosheets as advanced photosensitizers in semi-artificial photosynthetic systems, offering a robust platform for the effective utilization of the solar spectrum.

Multienergy Codriven Electron Transfer Across the Nano-Bio Interface for Efficient Photobiocatalysis

Integrating biocatalysis with nanophotocatalysis provides a promising pathway to address the knotty environmental and energy problems. However, energy loss during the transfer of extracellular electrons across the nano-bio interface seriously limits the efficiency of whole-cell-based photobiocatalytic systems. Herein, we demonstrate an integrated multienergy codriven reaction platform containing BaTiO3 nanoparticles (BTO) for harvesting mechanical energy from flowing water to elevate the interfacial electric field, BiVO4 quantum dots (BQD) for harvesting light energy to generate photocarriers, and Geobacter sulfurreducens (GS) for accepting photoelectrons to accomplish the biocatalytic reactions. The synergism between the piezoelectric and photoelectric fields significantly promotes the cross-membrane transport of photoelectrons, contributing to enhanced acetate metabolism, electron transfer, and energy synthesis of GS microbes. Such well-designed BQD/BTO-GS hybrids result in the simultaneous degradation of organic contaminants and detoxification of heavy metals in water with approximately 100% treatment efficiency. The rates of tetracycline (TC) oxidation and Cr(VI) reduction are determined to be 32.8 and 9.58 times higher than that of GS biocatalysis, respectively. Our photobiocatalytic platform exhibits an exceptional apparent quantum yield of 15.54% at 400 nm, exceeding those of most reported abiotic-biotic photobiocatalytic systems. Further investigation verifies the extensibility of our multienergy codriven strategy to the other nano-bio hybrids for enhancing the biocatalytic efficiencies (such as methanogenesis, CO2 fixation, and denitrification), thus offering an inspiring platform for energy and environmental applications. This work not only presents crucial insights into the mechanism of the water-energy nexus but also provides a paradigm for the construction of sustainable reaction systems via multienergy harnessing.

Solar-Driven Paired CO2 Reduction-Alcohol Oxidation Using Semiartificial Suspension, Photocatalyst Sheet, and Photoelectrochemical Devices

Fuel-forming enzymes can display excellent performance, achieving high rates of catalysis with unity selectivity at minimal overpotentials, but they are generally considered to be fragile and difficult to handle in combination with synthetic semiconductors in light-driven chemical synthesis. Here, we demonstrate a biohybrid platform that is assembled from cyanamide-functionalized carbon nitride (CNX) as a scalable and inexpensive photosensitizer that selectively photo-oxidizes 4-methyl benzyl alcohol (MBA) to its aldehyde (MBAld), indium tin oxide (ITO) nanoparticles as electron conduit and biocatalyst support material, and the enzyme formate dehydrogenase (FDH) for selective CO2-to-formate reduction. This integrated semiartificial multicomponent system can be assembled and used in several configurations to drive bias-free operation, including (i) a photocatalytic suspension, (ii) a photocatalyst sheet, and (iii) a photoelectrochemical cell. The unprecedented adaptability and robustness of the assembled biohybrid systems motivated us to select the best performing and scalable system in practical solar chemical production by deploying a 50 cm2 CNX-ITO|FDH photosheet device for 3 days under natural sunlight to produce 41 (mmol formate) m-2 and 35 (mmol aldehyde) m-2. We have therefore demonstrated that CNX-ITO|FDH provides a robust and versatile platform that enables solar chemical synthesis for several days in outdoor operation using natural sunlight.

Space-confined mediation of electron transfer for efficient biomolecular solar conversion

Solar-converting nanosystems using self-renewing biomaterial resources carry great potential for developing sustainable technologies to ameliorate climate change and minimize reliance on fossil fuels. By mimicking natural photosynthesis, diverse proof-of-concept biosolar systems have been used to produce green electricity, fuels and chemicals. Efforts so far have focused on optimizing light harvesting, biocatalyst loading and electron transfer (ET), however, the long-term performance of best-performing systems remains a major challenge due to the intensive use of diffusive, toxic mediators. To overcome this limitation, we developed a rationally designed nanosystem based on the entrapment of non-toxic mediator, ferrocene dimethanol (Fc), localized at the abiotic-biotic molecular interface that efficiently promoted ET between electrode surface and two photosynthetic proteins: cytochrome c and photosystem I. We demonstrate that space-confined Fc mediators (1 nM) are as effective in terms of ET kinetics as a 500 000-fold higher concentration of freely-diffusive Fc. The Fc-confined biophotocathodes showed a milestone photocurrent density of 14 μA cm-2 under oxic conditions compared to analogous planar (2D) biophotoelectrodes, with a photoconductive biolayer stable for over 5 months. The space-confined ET mediation reported in this work opens a new avenue for efficiently interfacing biomachineries, providing a benchmark design advancement in the quest for viable biohybrid technologies.

A photosynthesis-derived bionic system for sustainable biosynthesis

"Cell factory" strategy based on microbial anabolism pathways offers an intriguing alternative to relieve the dependence on fossil fuels, which are recognized as the main sources of CO2 emission. Typically, anabolism of intracellular substance in cell factory requires the consumption of sufficient reduced nicotinamide adenine dinucleotide /nicotinamide adenine dinucleotide phosphate NAD(P)H and adenosine triphosphate ATP. However, it is of great challenge to modify the natural limited anabolism and to increase the insufficient level of NAD(P)H and ATP to optimum concentrations without causing metabolic disorder. Inspired by the natural photosynthesis process in which NAD(P)H and ATP can both be produced through the coupled electron-proton transfer processes driven by sunlight, herein we designed a light-driven bionic system composed of three modules including photo-induced electron module, electron transfer channel module and proton gradient module. The proposed strategy of light-driven bionic system enables for achieving simultaneous and controllable supplies of NAD(P)H and ATP, thus facilitating both highly efficient CO2 fixation and biomanufacturing. The proposed light-driven bionic system design strategy in this work might pave new sustainable ways for reducing power and energy regeneration to optimize microbial metabolism, offering intriguing alternatives for CO2 emission mitigation and high-value chemical biomanufacturing.

Powering the Future: Unveiling the Secrets of Semiconductor Biointerfaces in Biohybrids for Semiartificial Photosynthesis

Developing technology for sustainable chemical and fuel production is a key focus of scientific research. Semiartificial photosynthesis is a promising approach, pairing "electric microbes" with artificial light absorbers (semiconductors) to convert N2, CO2, and water into value-added products using sunlight. Mimicking natural photosynthesis is done with semiconductors acting as electron donors or sinks for microbes. This method enables the production of multicarbon (C2+) chemicals (e.g., ethanol and caproic acid) and ammonia with high efficiency and selectivity. Despite significant progress, commercial-scale applications remain elusive due to fundamental challenges. This Review covers advances in semiartificial photosynthesis and highlights that there is no clear mechanistic understanding underpinning the production of chemicals using the combination of light, semiconductors, and microbes. Does the mechanism rely on H2 uptake, do the microbes eat electrons directly from the light absorbers, or is it a combination of both? It focuses on overcoming bottlenecks using advanced spectroscopy, microscopy, and synthetic biology tools to study charge transfer kinetics between microbial cell membranes and semiconductors. Understanding this interaction is crucial for increasing solar-to-chemical (STC) efficiencies, necessary for industrial use. This Review also outlines future research directions and techniques to advance this field, aiming to achieve net-zero climate goals through multidisciplinary efforts.

Supramolecular Reconstruction of Self-Assembling Photosensitizers for Enhanced Photocatalytic Hydrogen Evolution

Natural photosynthetic systems require spatiotemporal organization to optimize photosensitized reactions and maintain overall efficiency, involving the hierarchical self-assembly of photosynthetic components and their stabilization through synergistic interactions. However, replicating this level of organization is challenging due to the difficulty in efficiently communicating supramolecular nano-assemblies with nanoparticles or biological architectures, owing to their dynamic instability. Herein, we demonstrate that the supramolecular reconstruction of self-assembled amphiphilic rhodamine B nanospheres (RN) through treatment with metal-phenolic coordination complexes results in the formation of a stable hybrid structure. This reconstructed structure enhances electron transfer efficiency, leading to improved photocatalytic performance. Due to the photoluminescence quenching property of RN and its electronic synergy with tannic acid (T) and zirconium (Z), the supramolecular complexes of hybrid nanospheres (RNTxZy) with Pt nanoparticles or a biological workhorse, Shewanella oneidensis MR-1, showed marked improvement in photocatalytic hydrogen production. The supramolecular hybrid particles with a metal-phenolic coordination layer showed 5.6- and 4.0-fold increases, respectively, in the productivities of hydrogen evolution catalyzed by Pt (Pt/RNTxZy) and MR-1 (M/RNTxZy), respectively. These results highlight the potential for further advancements in the structural and photochemical control of supramolecular nanomaterials for energy harvesting and bio-hybrid systems.

Photoredox Cascade Catalysts for Solar Hydrogen Production From Sustainable Hydrogen Sources

Visible-light-driven photocatalytic hydrogen (H2) production has been extensively studied as a clean and sustainable energy resource. Although sacrificial electron donors (SEDs) are commonly used to evaluate photocatalytic activity, their irreversible decomposition forces charge separation, which disrupts the inherent dual productivity of photocatalysis, that is, the formation of both the reduction and oxidation products. To achieve highly efficient photoinduced charge separation without SED decomposition, the layer-by-layer assembly of redox-active photosensitizing dyes and electron mediators through Zr4+-phosphonate bonds has been extensively studied as an artificial mimic of the electron transport chain in natural photosynthesis. This concept paper presents an overview of photoredox cascade catalytic (PRCC) systems comprising multiple Ru(II)-trisbipyridine-type dyes and mediator layers on Pt-loaded TiO2 nanoparticles for H2 production from redox reversible electron donors (RREDs). The PRCC structure-activity relationship for photocatalytic H2 production is briefly discussed in terms of layer thickness, surface structure and modification, and cooperativity with molecular oxidation catalysts. Finally, new insights into the design of efficient dual-production photocatalysts based on the PRCC structure are presented.

Long-Term Autotrophic Growth and Solar-to-Chemical Conversion in Shewanella Oneidensis MR-1 through Light-Driven Electron Transfer

Members of the genus Shewanella are known for their versatile electron accepting routes, which allow them to couple decomposition of organic matter to reduction of various terminal electron acceptors for heterotrophic growth in diverse environments. Here, we report autotrophic growth of Shewanella oneidensis MR-1 with photoelectrons provided by illuminated biogenic CdS nanoparticles. This hybrid system enables photosynthetic oscillatory acetate production from CO2 for over five months, far exceeding other inorganic-biological hybrid system that can only sustain for hours or days. Biochemical, electrochemical and transcriptomic analyses reveal that the efficient electron uptake of S. oneidensis MR-1 from illuminated CdS nanoparticles supplies sufficient energy to stimulate the previously overlooked reductive glycine pathway for CO2 fixation. The continuous solar-to-chemical conversion is achieved by photon induced electric recycling in sulfur species. Overall, our findings demonstrate that this mineral-assisted photosynthesis, as a widely existing and unique model of light energy conversion, could support the sustained photoautotrophic growth of non-photosynthetic microorganisms in nutrient-lean environments and mediate the reversal of coupled carbon and sulfur cycling, consequently resulting in previously unknown environmental effects. In addition, the hybrid system provides a sustainable and flexible platform to develop a variety of solar products for carbon neutrality.

Solar-Driven Methanogenesis through Microbial Ecosystem Engineering on Carbon Nitride

Semi-biological photosynthesis combines synthetic photosensitizers with microbial catalysts to produce sustainable fuels and chemicals from CO2. However, the inefficient transfer of photoexcited electrons to microbes leads to limited CO2 utilization, restricting the catalytic performance of such biohybrid assemblies. Here, we introduce a biological engineering solution to address the inherently sluggish electron uptake mechanism of a methanogen, Methanosarcina barkeri (M. barkeri), by coculturing it with an electron transport specialist, Geobacter sulfurreducens KN400 (KN400), an adapted strain rich with multiheme c-type cytochromes (c-Cyts) and electrically conductive protein filaments (e-PFs) made of polymerized c-Cyts with enhanced capacity for extracellular electron transfer (EET). Integration of this M. barkeri-KN400 co-culture with a synthetic photosensitizer, carbon nitride, demonstrates that c-Cyts and e-PFs, emanating from live KN400, transport photoexcited electrons efficiently from the carbon nitride to M. barkeri for methanogenesis with remarkable long-term stability and selectivity. The demonstrated cooperative interaction between two microbes via direct interspecies electron transfer (DIET) and the photosensitizer to assemble a semi-biological photocatalyst introduces an ecosystem engineering strategy in solar chemistry to drive sustainable chemical reactions.

Precisely Constructing Molecular Junctions in Hydrogen-Bonded Organic Frameworks for Efficient Artificial Photosynthetic CO2 Reduction

The development of artificial photocatalysts to convert CO2 into renewable fuels and H2O into O2 is a complex and crucial task in the field of photosynthesis research. The current challenge is to enhance photogenerated charge separation, as well as to increase the oxidation capability of materials. Herein, a molecular junction-type porphyrin-based crystalline photocatalyst (Ni-TCPP-TPyP) was successfully self-assembled by incorporating a nickel porphyrin complex as a reduction site and pyridyl porphyrin as an oxidation site via hydrogen bonding and π-π stacking interactions. The resulting material has a highly crystalline structure, and the formation of inherent molecular junctions can accelerate photogenerated charge separation and transport. Thus, Ni-TCPP-TPyP achieved an excellent CO production rate of 309.3 μmol g-1 h-1 (selectivity, ~100 %) without the use of any sacrificial agents, which is more than ten times greater than that of single-component photocatalyst (Ni-TCPP) and greater than that of the most organic photocatalysts. The structure-function relationship was investigated by femtosecond transient absorption spectroscopy and density functional theory calculations. Our work provides new insight for designing efficient artificial photocatalysts, paving the way for the development of clean and renewable fuels through the conversion of CO2 using solar energy.

Chlorophyll a acts as a natural photosensitizer to drive nitrate reduction in nonphotosynthetic microorganisms

With the death and decomposition of widely distributed photosynthetic organisms, free natural pigments are often detected in surface water, sediment and soil. Whether free pigments can act as photosensitizers to drive biophotoelectrochemical metabolism in nonphotosynthetic microorganisms has not been reported. In this work, we provide direct evidence for the photoelectrophic relationship between extracellular chlorophyll a (Chl a) and nonphotosynthetic microorganisms. The results show that 10 μg of Chl a can produce significant photoelectrons (∼0.34 A/cm2) upon irradiation to drive nitrate reduction in Shewanella oneidensis. Chl a undergoes structural changes during the photoelectric process, thus the ability of Chl a to generate a photocurrent decreases gradually with increasing illumination time. These changes are greater in the presence of microorganisms than in the absence of microorganisms. Photoelectron transport from Chl a to S. oneidensis occurs through a direct pathway involving the cytochromes MtrA, MtrB, MtrC and CymA but not through an indirect pathway involving riboflavin. These findings reveal a novel photoelectrotrophic linkage between natural photosynthetic pigments and nonphototrophic microorganisms, which has important implications for the biogeochemical cycle of nitrogen in various natural environments where Chl a is distributed.

Proteomic and metabolic analysis of Moorella thermoacetica-g-C3N4 nanocomposite system for artificial photosynthesis

Artificial photosynthesis by microbe-semiconductor biohybrid systems has been demonstrated as a valuable strategy in providing sustainable energy and in carbon fixation. However, most of the developed biohybrid systems for light harvesting employ heavy metal materials, especially cadmium sulfide (CdS), which normally cause environmental pollution and restrict the widespread of the systems. Herein, we constructed an environmentally friendly biohybirid system based on a typical acetogenic bacteria, Moorella thermoacetica, coupling with a carbon-based semiconductor, graphitic carbon nitride (g-C3N4), to realize light-driven carbon fixation. The proposed biohybrid system displayed outstanding acetate productivity with a quantum yield of 2.66 ± 0.43 %. Non-targeted proteomic analysis indicated that the physiological activity of the bacteria was improved, coupling with the non-toxic material. We further proposed the mechanisms of energy generation, electron transfer and CO2 fixation of the irradiated biohybrid system by proteomic and metabolomic characterization. With the photoelectron generated in g-C3N4 under illumination, CO2 is finally converted to acetate via the Wood-Ljungdahl pathway (WLP). Other associated pathways were also proved to be activated, providing extra energy or substrates for acetate production. The study reveals that the future focus of the development of biohybrid systems for light harvesting can be on the metal-free biocompatible material, which can activate the expression of the key enzymes involved in the electron transfer and carbon metabolism under light irradiation.

Electrogenic performance and carbon sequestration potential of biophotovoltaics

Biophotovoltaics (BPV) is a clean and sustainable solar energy generation technology that operates by utilizing photosynthetic autotrophic microorganisms to capture light energy and generate electricity. However, a major challenge faced by BPV systems is the relatively low electron transfer efficiency from the photosystem to the extracellular electrode, which limits its electrical output. Additionally, the transfer mechanisms of photosynthetic microorganism metabolites in the entire system are still not fully clear. In response to this, this article briefly introduces the basic BPV principles, reviews its development history, and summarizes measures to optimize its electrogenic efficiency. Furthermore, recent studies have found that constructing photosynthetic-electrogenic microbial consortia can achieve high power density and stability in BPV systems. Therefore, the article discusses the potential application of constructing photosynthetic-electrogenic microbial aggregates in BPV systems. Since photosynthetic-electrogenic microbial communities can also exist in natural ecosystems, their potential contribution to the carbon cycle is worth further attention.

Small Conjugated Organic Ligand-Modified Polyoxometalate-Based Hybrid Materials for Boosting Photocatalytic CO2 Reduction

Photocatalytic carbon dioxide (CO2) reduction to value-added chemicals is a multielectron transfer process, and the crucial step is the synthesis of photocatalysts. The introduction of small conjugated organic ligands can make the catalytic active site of the compound easier to be exposed in the reaction system and fully contact with the substrate, accelerating the photocatalytic reaction process. In this paper, we synthesized two isomorphic compounds, namely, {[Co(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (1) and {[Ni(mtrz)3·(H2O)2]2·[SiW12O40]}·6H2O (2) (mtrz = 1-methyl-1,2,4-triazole). We found that compound 1 has a great photocatalytic performance through a series of experiments, with a CO reduction yield of 7364.92 μmol g-1 h-1 and a CO selectivity of 82.5%. Furthermore, the high catalytic activity can be maintained over four cycle experiments. The catalytic mechanism of its photocatalytic system is also elucidated, which provides an idea for realizing efficient catalytic reduction of CO2 to CO.

Host-Guest Approach to Promoting Photocatalysis Based on Consecutive Photo-Induced Electron-Transfer Processes via Efficient Förster Resonance Energy Transfer

Supramolecular artificial light-harvesting system with highly efficient host-guest energy transfer pathway provides an ideal platform for optimizing the photochemistry process. The consecutive photo-induced electron transfer (conPET) process overcomes the energy limitation of visible-light photocatalysis, but is often compromised by mismatching between the absorption of ground state dye and its radical, weakening the efficiency of photoredox reaction. By encapsulating a conPET photocatalyst rhodamine 6G into metal-organic cage, the supramolecular approach was undertaken to tackle the intrinsic difficulty of matching the light absorption of photoexcitation between rhodamine 6G and its radical. The highly efficient Förster resonance energy transfer from the photoexcited cage to rhodamine 6G forced by host-guest encapsulation facilitates the conPET process for the single-wavelength light-driven activation of aryl halides by stabilizing and accelerating the production and accumulation of the rhodamine 6G radical intermediate. The tunable and flexible nature of the supramolecular host-guest complex renders the cage-based encapsulation strategy promising for the development of ideal photocatalysts toward the better utilization of solar energy.

In-situ construction of biomineralized cadmium sulfide-Rhodopseudomonas palustris hybrid system: Mechanism of synergistic light utilization

Sulfide biomineralization is a microorganism-induced process for transforming the environmentally hazardous cadmium into useful resource utilization. This study successfully constructed cadmium sulfide nanoparticles-Rhodopseudomonas palustris (Bio-CdS NPs-R. palustris) hybrids. For the self-assembling hybrids, Bio-CdS NPs were treated as new artificial-antennas to enhance photosynthesis, especially under low light (LL). Bacterial physiological results of hybrids were significantly increased, particularly for cells under LL, with higher enhancement photon harvesting ability. The enhancement included the pigment contents, and the ratio of the peripheral light-harvesting complex Ⅱ (LH2) to light-harvesting Ⅰ (1.33 ± 0.01 under LL), leading to the improvements of light-harvesting, transfer, and antenna conversion efficiencies. Finally, the stimulated electron chain of hybrids improved bacterial metabolism with increased nicotinamide adenine dinucleotide (NADH, 174.5% under LL) and adenosine triphosphate (ATP, 41.1% under LL). Furthermore, the modified photosynthetic units were induced by the up-regulated expression of fixK, which was activated by reduced oxygen tension of the medium for hybrids. fixK up-regulated genes encoding pigments (crt, and bch) and complexes (puf, pucAB, and pucC), leading to improved light-harvesting and transfer, and transform ability. This study provides a comprehensive understanding of the solar energy utilization mechanism of in-situ semiconductor-phototrophic microbe hybrids, contributing to further theoretical insight into their practical application.

A biocompatible surface display approach in Shewanella promotes current output efficiency

The biology-material hybrid method for chemical-electricity conversion via microbial fuel cells (MFCs) has garnered significant attention in addressing global energy and environmental challenges. However, the efficiency of these systems remains unsatisfactory due to the complex manufacturing process and limited biocompatibility. To overcome these challenges, here, we developed a simple bio-inorganic hybrid system for bioelectricity generation in Shewanella oneidensis (S. oneidensis) MR-1. A biocompatible surface display approach was designed, and silver-binding peptide AgBP2 was expressed on the cell surface. Notably, the engineered Shewanella showed a higher electrochemical sensitivity to Ag+, and a 60 % increase in power density was achieved even at a low concentration of 10 μM Ag+. Further analysis revealed significant upregulations of cell surface negative charge intensity, ATP metabolism, and reducing equivalent (NADH/NAD+) ratio in the engineered S. oneidensis-Ag nanoparticles biohybrid. This work not only provides a novel insight for electrochemical biosensors to detect metal ions, but also offers an alternative biocompatible surface display approach by combining compatible biomaterials with electricity-converting bacteria for advancements in biohybrid MFCs.

Revisiting Solar Energy Flow in Nanomaterial-Microorganism Hybrid Systems

Nanomaterial-microorganism hybrid systems (NMHSs), integrating semiconductor nanomaterials with microorganisms, present a promising platform for broadband solar energy harvesting, high-efficiency carbon reduction, and sustainable chemical production. While studies underscore its potential in diverse solar-to-chemical energy conversions, prevailing NMHSs grapple with suboptimal energy conversion efficiency. Such limitations stem predominantly from an insufficient systematic exploration of the mechanisms dictating solar energy flow. This review provides a systematic overview of the notable advancements in this nascent field, with a particular focus on the discussion of three pivotal steps of energy flow: solar energy capture, cross-membrane energy transport, and energy conversion into chemicals. While key challenges faced in each stage are independently identified and discussed, viable solutions are correspondingly postulated. In view of the interplay of the three steps in affecting the overall efficiency of solar-to-chemical energy conversion, subsequent discussions thus take an integrative and systematic viewpoint to comprehend, analyze and improve the solar energy flow in the current NMHSs of different configurations, and highlighting the contemporary techniques that can be employed to investigate various aspects of energy flow within NMHSs. Finally, a concluding section summarizes opportunities for future research, providing a roadmap for the continued development and optimization of NMHSs.

Redox and Energy Homeostasis Enabled by Photocatalytic Material-Microbial Interfaces

Material-microbial interfaces offer a promising future in sustainable and efficient chemical-energy conversions, yet the impacts of these artificial interfaces on microbial metabolisms remain unclear. Here, we conducted detailed proteomic and metabolomic analyses to study the regulations of microbial metabolism induced by the photocatalytic material-microbial interfaces, especially the intracellular redox and energy homeostasis, which are vital for sustaining cell activity. First, we learned that the materials have a heavier weight in perturbing microbial metabolism and inducing distinctive biological pathways, like the expression of the metal-resisting system, than light stimulations. Furthermore, we observed that the materials-microbe interfaces can maintain the delicate redox balance and the energetic status of the microbial cells since the intracellular redox cofactors and energy currencies show stable levels as naturally inoculated microbes. These observations ensure the possibility of energizing microbial activities with artificial materials-microbe interfaces for diverse applications and also provide guides for future designs of materials-microbe hybrids to guard microbial activities.

Engineering of bespoke photosensitiser-microbe interfaces for enhanced semi-artificial photosynthesis

Biohybrid systems for solar fuel production integrate artificial light-harvesting materials with biological catalysts such as microbes. In this perspective, we discuss the rational design of the abiotic-biotic interface in biohybrid systems by reviewing microbes and synthetic light-harvesting materials, as well as presenting various approaches to coupling these two components together. To maximise performance and scalability of such semi-artificial systems, we emphasise that the interfacial design requires consideration of two important aspects: attachment and electron transfer. It is our perspective that rational design of this photosensitiser-microbe interface is required for scalable solar fuel production. The design and assembly of a biohybrid with a well-defined electron transfer pathway allows mechanistic characterisation and optimisation for maximum efficiency. Introduction of additional catalysts to the system can close the redox cycle, omitting the need for sacrificial electron donors. Studies that electronically couple light-harvesters to well-defined biological entities, such as emerging photosensitiser-enzyme hybrids, provide valuable knowledge for the strategic design of whole-cell biohybrids. Exploring the interactions between light-harvesters and redox proteins can guide coupling strategies when translated into larger, more complex microbial systems.

A Self-Assembled MOF-Escherichia Coli Hybrid System for Light-Driven Fuels and Valuable Chemicals Synthesis

The development of semi-artificial photosynthetic systems, which integrate metal-organic frameworks (MOFs) with industrial microbial cell factories for light-driven synthesis of fuels and valuable chemicals, represents a highly promising avenue for both research advancements and practical applications. In this study, an MOF (PCN-222) utilizing racemic-(4-carboxyphenyl) porphyrin and zirconium chloride (ZrCl4) as primary constituents is synthesized. Employing a self-assembly process, a hybrid system is constructed, integrating engineered Escherichia coli (E. coli) to investigate light-driven hydrogen and lysine production. These results demonstrate that the light-irradiated biohybrid system efficiently produce H2 with a quantum efficiency of 0.75% under full spectrum illumination, the elevated intracellular reducing power NADPH is also observed. By optimizing the conditions, the biohybrid system achieves a maximum lysine production of 18.25 mg L-1, surpassing that of pure bacteria by 332%. Further investigations into interfacial electron transfer mechanisms reveals that PCN-222 efficiently captures light and facilitates the transfer of photo-generated electrons into E. coli cells. It is proposed that the interfacial energy transfer process is mediated by riboflavin, with facilitation by secreted small organic acids acting as hole scavengers for PCN-222. This study establishes a crucial foundation for future research into the light-driven biomanufacturing using E. coli-based hybrid systems.

Operando Spectroscopic Elucidation of the Bubble Sunshade Effect in Inorganic-Biological Hybrids for Photosynthetic Hydrogen Production

Hydrogen production by photosynthetic hybrid systems (PBSs) offers a promising avenue for renewable energy. However, the light-harvesting efficiency of PBSs remains constrained due to unclear intracellular kinetic factors. Here, we present an operando elucidation of the sluggish light-harvesting behavior for existing PBSs and strategies to circumvent them. By quantifying the spectral shift in the structural color scattering of individual PBSs during the photosynthetic process, we observe the accumulation of product hydrogen bubbles on their outer membrane. These bubbles act as a sunshade and inhibit light absorption. This phenomenon elucidates the intrinsic constraints on the light-harvesting efficiency of PBSs. The introduction of a tension eliminator into the PBSs effectively improves the bubble sunshade effect and results in a 4.5-fold increase in the light-harvesting efficiency. This work provides valuable insights into the dynamics of transmembrane transport gas products and holds the potential to inspire innovative designs for improving the light-harvesting efficiency of PBSs.

Conjugated Polymer/Recombinant Escherichia coli Biohybrid Systems for Photobiocatalytic Hydrogen Production

Biohybrid photocatalysts are composite materials that combine the efficient light-absorbing properties of synthetic materials with the highly evolved metabolic pathways and self-repair mechanisms of biological systems. Here, we show the potential of conjugated polymers as photosensitizers in biohybrid systems by combining a series of polymer nanoparticles with engineered Escherichia coli cells. Under simulated solar light irradiation, the biohybrid system consisting of fluorene/dibenzo [b,d]thiophene sulfone copolymer (LP41) and recombinant E. coli (i.e., a LP41/HydA BL21 biohybrid) shows a sacrificial hydrogen evolution rate of 3.442 mmol g-1 h-1 (normalized to polymer amount). It is over 30 times higher than the polymer photocatalyst alone (0.105 mmol g-1 h-1), while no detectable hydrogen was generated from the E. coli cells alone, demonstrating the strong synergy between the polymer nanoparticles and bacterial cells. The differences in the physical interactions between synthetic materials and microorganisms, as well as redox energy level alignment, elucidate the trends in photochemical activity. Our results suggest that organic semiconductors may offer advantages, such as solution processability, low toxicity, and more tunable surface interactions with the biological components over inorganic materials.

Performance evaluation and multidisciplinary analysis of catalytic fixation reactions by material-microbe hybrids

Hybrid systems that integrate synthetic materials with biological machinery offer opportunities for sustainable and efficient catalysis. However, the multidisciplinary and unique nature of the materials-biology interface requires researchers to draw insights from different fields. In this Perspective, using examples from the area of N2 and CO2 fixation, we provide a unified discussion of critical aspects of the material-microbe interface, simultaneously considering the requirements of physical and biological sciences that have a tangible impact on the performance of biohybrids. We first discuss the figures of merit and caveats for the evaluation of catalytic performance. Then, we reflect on the interactions and potential synergies at the materials-biology interface, as well as the challenges and opportunities for a deepened fundamental understanding of abiotic-biotic catalysis.

Electrostatic [FeFe]-hydrogenase-carbon nitride assemblies for efficient solar hydrogen production

The assembly of semiconductors as light absorbers and enzymes as redox catalysts offers a promising approach for sustainable chemical synthesis driven by light. However, achieving the rational design of such semi-artificial systems requires a comprehensive understanding of the abiotic-biotic interface, which poses significant challenges. In this study, we demonstrate an electrostatic interaction strategy to interface negatively charged cyanamide modified graphitic carbon nitride (NCNCNX) with an [FeFe]-hydrogenase possessing a positive surface charge around the distal FeS cluster responsible for electron uptake into the enzyme. The strong electrostatic attraction enables efficient solar hydrogen (H2) production via direct interfacial electron transfer (DET), achieving a turnover frequency (TOF) of 18 669 h-1 (4 h) and a turnover number (TON) of 198 125 (24 h). Interfacial characterizations, including quartz crystal microbalance (QCM), photoelectrochemical impedance spectroscopy (PEIS), intensity-modulated photovoltage spectroscopy (IMVS), and transient photocurrent spectroscopy (TPC) have been conducted on the semi-artificial carbon nitride-enzyme system to provide a comprehensive understanding for the future development of photocatalytic hybrid assemblies.

Temperature modulated sustainable on/off photosynthesis switching of microalgae towards hydrogen evolution

Despite great progress in the active interfacing between various abiotic materials and living organisms, the development of a smart polymer matrix with modulated functionality of algae towards the application of green bioenergy is still rare. Herein, we design a thermally sensitive poly(N-isopropylacrylamide)-co-poly(butyl acrylate) with an LCST (ca. 25 °C) as a chassis, which could co-assemble with algal cells based on hydrophobic interaction to generate a new type of robust hybrid hydrogel living material. By modulating the temperature to 30 °C, the volume of the polymer matrix is shrunk by 9 times, which allows the formation of physical shading and metabolism changing of the algae, and then triggers the functionality switching of the algae from photosynthetic oxygen production to hydrogen production. By contrast, by decreasing the temperature to 20 °C, the hybrid living materials go into a sol state where the algae behave normally with photosynthetic oxygen production. In particular, due to the proliferation of the algae in living materials, a long-term and exponential enhancement in the amount of hydrogen produced is achieved. Overall, it is anticipated that our investigations could provide a new paradigm for the development of polymer/living organism-based hybrid living materials with synergistic functionality boosting green biomanufacturing.

A heterogeneous cobalt cubane polymer co-catalyst for cooperative water oxidation

We achieve a successful transition of Co4O4 molecules from a homogeneous to a heterogeneous system by modifying the functional groups at their termini. The resulting cocatalyst, denoted as Co4O4-poly, not only preserved the catalytic sites of Co4O4 molecules but also exhibited outstanding performance in catalyzing water oxidation.

Engineering extracellular electron transfer pathways of electroactive microorganisms by synthetic biology for energy and chemicals production

The excessive consumption of fossil fuels causes massive emission of CO2, leading to climate deterioration and environmental pollution. The development of substitutes and sustainable energy sources to replace fossil fuels has become a worldwide priority. Bio-electrochemical systems (BESs), employing redox reactions of electroactive microorganisms (EAMs) on electrodes to achieve a meritorious combination of biocatalysis and electrocatalysis, provide a green and sustainable alternative approach for bioremediation, CO2 fixation, and energy and chemicals production. EAMs, including exoelectrogens and electrotrophs, perform extracellular electron transfer (EET) (i.e., outward and inward EET), respectively, to exchange energy with the environment, whose rate determines the efficiency and performance of BESs. Therefore, we review the synthetic biology strategies developed in the last decade for engineering EAMs to enhance the EET rate in cell-electrode interfaces for facilitating the production of electricity energy and value-added chemicals, which include (1) progress in genetic manipulation and editing tools to achieve the efficient regulation of gene expression, knockout, and knockdown of EAMs; (2) synthetic biological engineering strategies to enhance the outward EET of exoelectrogens to anodes for electricity power production and anodic electro-fermentation (AEF) for chemicals production, including (i) broadening and strengthening substrate utilization, (ii) increasing the intracellular releasable reducing equivalents, (iii) optimizing c-type cytochrome (c-Cyts) expression and maturation, (iv) enhancing conductive nanowire biosynthesis and modification, (v) promoting electron shuttle biosynthesis, secretion, and immobilization, (vi) engineering global regulators to promote EET rate, (vii) facilitating biofilm formation, and (viii) constructing cell-material hybrids; (3) the mechanisms of inward EET, CO2 fixation pathway, and engineering strategies for improving the inward EET of electrotrophic cells for CO2 reduction and chemical production, including (i) programming metabolic pathways of electrotrophs, (ii) rewiring bioelectrical circuits for enhancing inward EET, and (iii) constructing microbial (photo)electrosynthesis by cell-material hybridization; (4) perspectives on future challenges and opportunities for engineering EET to develop highly efficient BESs for sustainable energy and chemical production. We expect that this review will provide a theoretical basis for the future development of BESs in energy harvesting, CO2 fixation, and chemical synthesis.

Photo-Electro-Biochemical H2 Production Using the Carbon Material-Based Cathode Combined with Genetically Engineered Escherichia coli Whole-Cell Biocatalysis

Abio/bio hybrids, which incorporate biocatalysts that promote efficient and selective material conversions under mild conditions into existing catalytic reactions, have attracted considerable attention for developing new catalytic systems. This study constructed a H2 -forming biocathode based on a carbon material combined with whole-cell biocatalysis of genetically-engineered-hydrogenase-overproducing Escherichia coli for the photoelectrochemical water splitting for clean H2 production. Low-cost and abundant carbon materials are generally not suitable for H2 -forming cathode due to their high overpotential for proton reduction; however, the combination of the reduction of an organic electron mediator on the carbon electrode and the H2 formation with the reduced mediator by the redox enzyme hydrogenase provides a H2 -forming cathodic reaction comparable to that of the noble metal electrode. The present study demonstrates that the recombinant E. coli whole cell can be employed as a part of the H2 -forming biocathode system, and the biocathode system wired with TiO2 photoanode can be a photoelectrochemical water-splitting system without external voltage assistance under natural pH. The findings of this study expand the feasibility of applications of whole-cell biocatalysis and contribute to obtaining solar-to-chemical conversions by abio/bio hybrid systems, especially for low-cost, noble-metal-free, and clean H2 production.

A Facile Design for Water-Oxidation Molecular Catalysts Precise Assembling on Photoanodes

Regulating the interfacial charge transfer behavior between cocatalysts and semiconductors remains a critical challenge for attaining efficient photoelectrochemical water oxidation reactions. Herein, using bismuth vanadate (BiVO4 ) photoanode as a model, it introduces an Au binding bridge as holes transfer channels onto the surfaces of BiVO4 , and the cyano-functionalized cobalt cubane (Co4 O4 ) molecules are preferentially immobilized on the Au bridge due to the strong adsorption of cyano groups with Au nanoparticles. This orchestrated arrangement facilitates the seamless transfer of photogenerated holes from BiVO4 to Co4 O4 molecules, forming an orderly charge transfer pathway connecting the light-absorbing layer to reactive sites. An exciting photocurrent density of 5.06 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (3.4 times that of BiVO4 ) is obtained by the Co4 O4 @Au(A)/BiVO4 photoanode, where the surface charge recombination is almost completely suppressed accompanied by a surface charge transfer efficiency over 95%. This work represents a promising strategy for accelerating interfacial charge transfer and achieving efficient photoelectrochemical water oxidation reaction.

Highly Efficient Nitrogen-Fixing Microbial Hydrogel Device for Sustainable Solar Hydrogen Production

Conversion of sunlight and organic carbon substrates to sustainable energy sources through microbial metabolism has great potential for the renewable energy industry. Despite recent progress in microbial photosynthesis, the development of microbial platforms that warrant efficient and scalable fuel production remains in its infancy. Efficient transfer and retrieval of gaseous reactants and products to and from microbes are particular hurdles. Here, inspired by water lily leaves floating on water, a microbial device designed to operate at the air-water interface and facilitate concomitant supply of gaseous reactants, smooth capture of gaseous products, and efficient sunlight delivery is presented. The floatable device carrying Rhodopseudomonas parapalustris, of which nitrogen fixation activity is first determined through this study, exhibits a hydrogen production rate of 104 mmol h-1  m-2 , which is 53 times higher than that of a conventional device placed at a depth of 2 cm in the medium. Furthermore, a scaled-up device with an area of 144 cm2 generates hydrogen at a high rate of 1.52 L h-1  m-2 . Efficient nitrogen fixation and hydrogen generation, low fabrication cost, and mechanical durability corroborate the potential of the floatable microbial device toward practical and sustainable solar energy conversion.

Ultrasound-Induced Abiotic and Biotic Interfacial Electron Transfer for Efficient Treatment of Bacterial Infection

Electron transfer plays an important role in various catalytic reactions and physiological activities, whose altered processes may change catalytic efficiency and interfere in physiological metabolic processes. In this study, we design an ultrasound (US)-activated piezoelectric responsive heterojunction (PCN-222-BTO, PCN: porous coordination network), which can change the electron transfer path at the abiotic and abiotic-biotic interfaces under US, thus achieving a rapid (15 min) and efficient bactericidal effect of 99.96%. US-induced polarization of BTO generates a built-in electric field, which promotes the electron transfer excited from PCN-222 to BTO at the PCN-222-BTO interface, thereby increasing the level of reactive oxygen species (ROS) production. Especially, we find that the biological electron transfer from the bacterial membrane to BTO is also activated at the MRSA-BTO interface. This antibacterial mode results in the down-regulated ribosomal, DNA and ATP synthesis related genes in MRSA, while the cell membrane and ion transport related genes are up-regulated due to the synergistic damage effect of ROS and disturbance of the bacterial electron transport chain. This US responsive dual-interface system shows an excellent therapeutic effect for the treatment of the MRSA-infected osteomyelitis model, which is superior to clinical vancomycin therapy.

Photoredox Cascade Catalyst for Efficient Hydrogen Production with Biomass Photoreforming

Biomass photoreforming is a promising method to provide both a clean energy resource in the form of hydrogen (H2 ) and valuable chemicals as the results of water reduction and biomass oxidation. To overcome the poor contact between heterogeneous photocatalysts and biomass substrates, we fabricated a new photoredox cascade catalyst by combining a homogeneous catalyst, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), and a heterogeneous dual-dye sensitized photocatalyst (DDSP) composed of two Ru(II)-polypyridine photosensitizers (RuP6 and RuCP6 ) and Pt-loaded TiO2 nanoparticles. During blue-light irradiation (λ=460±15 nm; 80 mW), the DDSP photocatalytically reduced aqueous protons to form H2 and simultaneously oxidized TEMPO• radicals to generate catalytically active TEMPO+ . It oxidized biomass substrates (water-soluble glycerol and insoluble cellulose) to regenerate TEMPO• . In the presence of N-methyl imidazole as a proton transfer mediator, the photocatalytic H2 production activities for glycerol and cellulose reforming reached 2670 and 1590 μmol H2 (gTiO2 )-1  h-1 , respectively, which were comparable to those of state-of-the-art heterogeneous photocatalysts.

Pursuing excitonic energy transfer with programmable DNA-based optical breadboards

DNA nanotechnology has now enabled the self-assembly of almost any prescribed 3-dimensional nanoscale structure in large numbers and with high fidelity. These structures are also amenable to site-specific modification with a variety of small molecules ranging from drugs to reporter dyes. Beyond obvious application in biotechnology, such DNA structures are being pursued as programmable nanoscale optical breadboards where multiple different/identical fluorophores can be positioned with sub-nanometer resolution in a manner designed to allow them to engage in multistep excitonic energy-transfer (ET) via Förster resonance energy transfer (FRET) or other related processes. Not only is the ability to create such complex optical structures unique, more importantly, the ability to rapidly redesign and prototype almost all structural and optical analogues in a massively parallel format allows for deep insight into the underlying photophysical processes. Dynamic DNA structures further provide the unparalleled capability to reconfigure a DNA scaffold on the fly in situ and thus switch between ET pathways within a given assembly, actively change its properties, and even repeatedly toggle between two states such as on/off. Here, we review progress in developing these composite materials for potential applications that include artificial light harvesting, smart sensors, nanoactuators, optical barcoding, bioprobes, cryptography, computing, charge conversion, and theranostics to even new forms of optical data storage. Along with an introduction into the DNA scaffolding itself, the diverse fluorophores utilized in these structures, their incorporation chemistry, and the photophysical processes they are designed to exploit, we highlight the evolution of DNA architectures implemented in the pursuit of increased transfer efficiency and the key lessons about ET learned from each iteration. We also focus on recent and growing efforts to exploit DNA as a scaffold for assembling molecular dye aggregates that host delocalized excitons as a test bed for creating excitonic circuits and accessing other quantum-like optical phenomena. We conclude with an outlook on what is still required to transition these materials from a research pursuit to application specific prototypes and beyond.

Making the connections: physical and electric interactions in biohybrid photosynthetic systems

Biohybrid photosynthesis systems, which combine biological and non-biological materials, have attracted recent interest in solar-to-chemical energy conversion. However, the solar efficiencies of such systems remain low, despite advances in both artificial photosynthesis and synthetic biology. Here we discuss the potential of conjugated organic materials as photosensitisers for biological hybrid systems compared to traditional inorganic semiconductors. Organic materials offer the ability to tune both photophysical properties and the specific physicochemical interactions between the photosensitiser and biological cells, thus improving stability and charge transfer. We highlight the state-of-the-art and opportunities for new approaches in designing new biohybrid systems. This perspective also summarises the current understanding of the underlying electron transport process and highlights the research areas that need to be pursued to underpin the development of hybrid photosynthesis systems.

Roots Fuel Cell Produces and Stores Clean Energy

In recent years, extensive scientific efforts have been conducted to develop clean bioenergy technologies. A promising approach that has been under development for more than a hundred years is the microbial fuel cell (MFC) which utilizes exoelectrogenic bacteria as an electron source in a bioelectrochemical cell. The viability of bacteria in soil MFCs can be maintained by integrating plant roots, which release organic materials that feed the bacteria. In this work, we show that rather than organic compounds, roots also release redox species that can produce electricity in a biofuel cell. We first studied the reduction of the electron acceptor Cytochrome C by green onion roots. We integrate green onion roots into a biofuel cell to produce a continuous bias-free electric current for more than 24 h in the dark. This current is enhanced upon irradiation of the onion's leaves with light. We apply cyclic voltammetry and 2D-fluorescence measurements to show that NADH and NADPH act as major electron mediators between the roots and the anode, while their concentrations in the external root matrix are increased upon irradiation of the leaves. Finally, we show that roots can contribute to energy storage by charging a supercapacitor.

Direct Biocatalytic Processes for CO2 Capture as a Green Tool to Produce Value-Added Chemicals

Direct biocatalytic processes for CO₂ capture and transformation in value-added chemicals may be considered a useful tool for reducing the concentration of this greenhouse gas in the atmosphere. Among the other enzymes, carbonic anhydrase (CA) and formate dehydrogenase (FDH) are two key biocatalysts suitable for this challenge, facilitating the uptake of carbon dioxide from the atmosphere in complementary ways. Carbonic anhydrases accelerate CO₂ uptake by promoting its solubility in water in the form of hydrogen carbonate as the first step in converting the gas into a species widely used in carbon capture storage and its utilization processes (CCSU), particularly in carbonation and mineralization methods. On the other hand, formate dehydrogenases represent the biocatalytic machinery evolved by certain organisms to convert CO₂ into enriched, reduced, and easily transportable hydrogen species, such as formic acid, via enzymatic cascade systems that obtain energy from chemical species, electrochemical sources, or light. Formic acid is the basis for fixing C₁-carbon species to other, more reduced molecules. In this review, the state-of-the-art of both methods of CO₂ uptake is assessed, highlighting the biotechnological approaches that have been developed using both enzymes.

Light-driven biohybrid system utilizes N2 for photochemical CO2 reduction

Attempting to couple photochemical CO₂ reduction with N₂ fixation is usually difficult, because the reaction conditions for these two processes are typically incompatible. Here, we report that a light-driven biohybrid system can utilize abundant, atmospheric N₂ to produce electron donors via biological nitrogen fixation, to achieve effective photochemical CO₂ reduction. This biohybrid system is constructed by incorporating molecular cobalt-based photocatalysts into N₂-fixing bacteria. It is found that N₂-fixing bacteria can convert N₂ into reductive organic nitrogen and create a localized anaerobic environment, which allows the incorporated photocatalysts to continuously perform photocatalytic CO₂ reduction under aerobic conditions. Specifically, the light-driven biohybrid system displays a high formic acid production rate of over 1.41 × 10^-14 mol h^-1 cell^-1 under visible light irradiation, and the organic nitrogen content undergoes an over-3-fold increase within 48 hours. This work offers a useful strategy for coupling CO₂ conversion with N₂ fixation under mild and environmentally benign conditions.

Biotic-abiotic hybrids for bioanalytics and biocatalysis

The advances in biotic-abiotic interfaced systems open new directions toward bioanalytics and biocatalysis applications. Conjugating the unique electronic and optic properties of nanoelements with the high selectivity and extraordinary catalytic abilities of biotic materials holds great promise to gain superior new features. Herein, we present a wide scope of biotic-abiotic research, with key examples for its utilization in bioanalytics applications as well as in biocatalysis. The described configurations feature methodologies that enable extending the known scientific toolbox to gain synergy. These new nanobiohybrids may contribute to major global challenges, for example, developing alternative energy utilization or new affordable biodiagnostics and therapeutics tools.

Supramolecular Biohybrid Construct for Photoconversion Based on a Bacterial Reaction Center Covalently Bound to Cytochrome c by an Organic Light Harvesting Bridge

A supramolecular construct for solar energy conversion is developed by covalently bridging the reaction center (RC) from the photosynthetic bacterium Rhodobacter sphaeroides and cytochrome c (Cyt c) proteins with a tailored organic light harvesting antenna (hCy2). The RC-hCy2-Cyt c biohybrid mimics the working mechanism of biological assemblies located in the bacterial cell membrane to convert sunlight into metabolic energy. hCy2 collects visible light and transfers energy to the RC, increasing the rate of photocycle between a RC and Cyt c that are linked in such a way that enhances proximity without preventing protein mobility. The biohybrid obtained with average 1 RC/10 hCy2/1.5 Cyt c molar ratio features an almost doubled photoactivity versus the pristine RC upon illumination at 660 nm, and ∼10 times higher photocurrent versus an equimolar mixture of the unbound proteins. Our results represent an interesting insight into photoenzyme chemical manipulation, opening the way to new eco-sustainable systems for biophotovoltaics.

Water-soluble conjugated polymers for bioelectronic systems

Bioelectronics is an interdisciplinary field of research that aims to establish a synergy between electronics and biology. Contributing to a deeper understanding of bioelectronic processes and the built bioelectronic systems, a variety of new phenomena, mechanisms and concepts have been derived in the field of biology, medicine, energy, artificial intelligence science, etc. Organic semiconductors can promote the applications of bioelectronics in improving original performance and creating new features for organisms due to their excellent photoelectric and electrical properties. Recently, water-soluble conjugated polymers (WSCPs) have been employed as a class of ideal interface materials to regulate bioelectronic processes between biological systems and electronic systems, relying on their satisfying ionic conductivity, water-solubility, good biocompatibility and the additional mechanical and electrical properties. In this review, we summarize the prominent contributions of WSCPs in the aspect of the regulation of bioelectronic processes and highlight the latest advances in WSCPs for bioelectronic applications, involving biosynthetic systems, photosynthetic systems, biophotovoltaic systems, and bioelectronic devices. The challenges and outlooks of WSCPs in designing high-performance bioelectronic systems are also discussed.