Scalable long-term extraction of photosynthetic electrons by simple sandwiching of nanoelectrode array with densely-packed algal cell film

Prolonged hydrogen production by engineered green algae photovoltaic power stations

Interest in securing energy production channels from renewable sources is higher than ever due to the daily observation of the impacts of climate change. A key renewable energy harvesting strategy achieving carbon neutral cycles is artificial photosynthesis. Solar-to-fuel routes thus far relied on elaborately crafted semiconductors, undermining the cost-efficiency of the system. Furthermore, fuels produced required separation prior to utilization. As an artificial photosynthesis design, here we demonstrate the conversion of swimming green algae into photovoltaic power stations. The engineered algae exhibit bioelectrogenesis, en route to energy storage in hydrogen. Notably, fuel formation requires no additives or external bias other than CO2 and sunlight. The cellular power stations autoregulate the oxygen level during artificial photosynthesis, granting immediate utility of the photosynthetic hydrogen without separation. The fuel production scales linearly with the reactor volume, which is a necessary trait for contributing to the large-scale renewable energy portfolio.

Photosynthetic Nanomaterial Hybrids for Bioelectricity and Renewable Energy Systems

Harvesting solar energy in the form of electricity from the photosynthesis of plants, algal cells, and bacteria has been researched as the most environment-friendly renewable energy technology in the last decade. The primary challenge has been the engineering of electrochemical interfacing with photosynthetic apparatuses, organelles, or whole cells. However, with the aid of low-dimensional nanomaterials, there have been many advances, including enhanced photon absorption, increased generation of photosynthetic electrons (PEs), and more efficient transfer of PEs to electrodes. These advances have demonstrated the possibility for the technology to advance to a new level. In this article, the fundamentals of photosynthesis are introduced. How PE harvesting systems have improved concerning solar energy absorption, PE production, and PE collection by electrodes is discussed. The review focuses on how different kinds of nanomaterials are applied and function in interfacing with photosynthetic materials for enhanced PE harvesting. Finally, the review analyzes how the performance of PE harvesting and stand-alone systems have evolved so far and its future prospects.

Enhanced interfacial electron transfer between thylakoids and RuO2 nanosheets for photosynthetic energy harvesting

The harvesting of photosynthetic electrons (PEs) directly from photosynthetic complexes has been demonstrated over the past decade. However, their limited efficiency and stability have hampered further practical development. For example, despite its importance, the interfacial electron transfer between the photosynthetic apparatus and the electrode has received little attention. In this study, we modified electrodes with RuO₂ nanosheets to enhance the extraction of PEs from thylakoids, and the PE transfer was promoted by proton adsorption and surface polarity characteristics. The adsorbed protons maintained the potential of an electrode more positive, and the surface polarity enhanced thylakoid attachment to the electrode in addition to promoting ensemble docking between the redox species and the electrode. The RuO₂ bioanode exhibited a five times larger current density and a four times larger power density than the Au bioanode. Last, the electric calculators were successfully powered by photosynthetic energy using a RuO₂ bioanode.

Electrosprayed Thylakoid-Alginate Film on a Micro-Pillar Electrode for Scalable Photosynthetic Energy Harvesting

Direct harvesting of electricity from photosynthesis is highly desired as an eco-friendly and sustainable energy harvesting technology. Photosynthetic apparatuses isolated from plants, such as thylakoid membranes (TMs), are deposited on an electrode by which photosynthetic electrons (PEs) are collected from water splitting. To enhance PE collection efficiency, it is critical to increase the electrochemical interfaces between TMs and the electrode. Considering the size of TMs to be around a few hundred nanometer, we hypothesize that an array of micropillar-shaped (MP) electrode can maximize the TM/electrode interface area. Thus, we developed MP electrodes with different heights and investigated the electrospraying of TM-alginate mixtures to fill the gaps between MPs uniformly and conformally. The uniformity of the TM-alginate film and the interaction between the TM and the MP electrode were evaluated to understand how the MP heights and film quality influenced the magnitude of the PE currents. PE currents increased up to 2.4 times for an MP electrode with an A/R of 1.8 compared to a flat electrode, indicating increased direct contact interface between TMs and the electrode. Furthermore, to demonstrate the scalability of this approach, an array of replicated SU-8 MP electrodes was prepared and PE currents of up to 3.2 μA were monitored without a mediator under 68 mW/cm². Finally, the PE current harvesting was sustained for 14 days without decay, demonstrating the long-term stability of the TM-alginate biophotoanodes.

Evaluation of the Liver Toxicity of Pterocephalus hookeri Extract via Triggering Necrosis

Pterocephalus hookeri (C. B. Clarke) Höeck, recorded in the Chinese Pharmacopoeia (2015 version) as a Tibetan medicine for the treatment of various diseases, especially rheumatoid arthritis, was believed to possess a slight toxicity. However, hardly any research has been carried out about it. The present study aimed to evaluate the toxicity in vivo and in vitro. Toxicity was observed by the evaluation of mice weight loss and histopathological changes in the liver. Then, the comparison research between ethyl acetate extract (EAE) and n-butanol extract (BUE) suggested that liver toxicity was mainly induced by BUE. The mechanical study suggested that BUE-induced liver toxicity was closely associated with necrosis detected by MTT and propidium iodide (PI) staining, via releasing lactate dehydrogenase (LDH), reducing the fluidity, and increasing the permeability of the cell membrane. Western blot analysis confirmed that the necrosis occurred molecularly by the up-regulation of receptor-interacting protein kinase 1 (RIP1) and receptor-interacting protein kinase 3 (RIP3), as well as the activation of the nuclear factor-kappa-gene binding (NF-κB) signaling pathway in vivo and in vitro. This finding indicated that the liver toxicity induced by BUE from P. hookeri was mainly caused by necrosis, which provides an important theoretical support for further evaluation of the safety of this folk medicine.