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Microfluidic systems with large surface‐to‐volume ratios and superior light transmission are used to efficiently transfer mass and convert energy, and to enhance photocatalytic reactions. Utilizing the entire solar spectrum for promoting photocatalytic reactions is highly desirable and near‐infrared (NIR) radiation, in particular, has a high transmission efficiency through common polymers and materials used to construct microfluidic devices. Herein, a reliable microfluidic system using bimodal light‐harvesting technique is reported to improve the photocatalytic efficiency of C(sp3)‐H functionalization reactions using coumarin dye (C153) and lanthanide‐doped upconversion nanocrystals (UCNs). Using two light‐harvesting components (C153 and UCNs) in polycarbosilane polymer matrix, a bimodal light‐harvesting microfluidic reactor is realized in which the inner surface of the microfluidic channel is reliably coated with a transparent composite of C153/UCNs to simultaneously downshift visible light and upconvert NIR light. A double‐stacked microfluidic system that successfully enhanced the photocatalytic conversion efficiency of Rose Bengal‐based aza‐Henry photocatalytic reactions by twofold (≈93% conversion). The study provides a design principle of next‐generation microfluidic reactor for a robust photocatalytic organic synthesis. [ABSTRACT FROM AUTHOR]

We report the development of semiconducting melanin‐based organic/inorganic hybrid photoanodes for solar water oxidation. Synthetic melanin thin‐film incorporating polyoxometalate (POM) water oxidation catalysts (WOCs) are readily deposited on the surface of various n‐type inorganic semiconductors (e.g. Fe2O3, BiVO4, and TiO2) by electropolymerization. The deposition of melanin and POM hybrid (MP) thin‐film results in the remarkably improved performance of an underlying semiconductor photoanode for solar water oxidation with a significantly increased photocurrent density and decreased onset potential for water oxidation through the formation of a melanin‐based p–n heterojunction structure. We believe that this study can provide insights into the design and fabrication of various melanin‐based optoelectronic devices by utilizing its unique physicochemical properties. Artificial photosynthesis: Semiconducting synthetic melanin‐based organic/inorganic hybrid photoanodes were fabricated for solar water oxidation. Detailed analysis revealed that electrochemical deposition of melanin on an n‐type inorganic semiconductor leads to the formation of a p–n heterojunction structure and can be utilized for the fabrication of efficient photoanodes for solar water oxidation (see figure). [ABSTRACT FROM AUTHOR]

Efficient harvesting of unlimited solar energy and its conversion into valuable chemicals is one of the ultimate goals of scientists. With the ever-increasing concerns about sustainable growth and environmental issues, numerous efforts have been made to develop artificial photosynthetic process for the production of fuels and fine chemicals, thus mimicking natural photosynthesis. Despite the research progress made over the decades, the technology is still in its infancy because of the difficulties in kinetic coupling of whole photocatalytic cycles. Herein, we report a new type of artificial photosynthesis system that can avoid such problems by integrally coupling biocatalytic redox reactions with photocatalytic water splitting. We found that photocatalytic water splitting can be efficiently coupled with biocatalytic redox reactions by using tetracobalt polyoxometalate and Rh-based organometallic compound as hole and electron scavengers, respectively, for photoexcited [Ru(bpy)3]2+. Based on these results, we could successfully photosynthesize a model chiral compound (l-glutamate) using a model redox enzyme (glutamate dehydrogenase) upon in situ photoregeneration of cofactors. [ABSTRACT FROM AUTHOR]

Solar-to-Chemical Energy Conversion: Modular Layer-by-Layer Assembly of Polyelectrolytes, Nanoparticles, and Molecular Catalysts into Solar-to-Chemical Energy Conversion Devices (Adv. Funct. In article number 1906407, Joonseok Lee, Jiseok Lee, Jungki Ryu, and co-workers suggest the fabrication of solar-to-chemical energy conversion devices using a layer-by-layer assembly method. Rational and precise assembly of plasmonic and upconversion nanoparticles, polyelectrolytes, and molecular catalysts enables more efficient light-harvesting, surface passivation, and catalysis, respectively, for solar water oxidation. [Extracted from the article]

The design and fabrication of solar‐to‐chemical energy conversion devices are enabled through interweaving multiple components with various morphologies and unique functions using a versatile layer‐by‐layer assembly method. Cationic and anionic polyelectrolytes are used as an electrostatic adhesive to assemble the following functional materials: plasmonic Ag nanoparticles for improved light harvesting, upconversion nanoparticles for utilization of near‐infrared light, and polyoxometalate water oxidation catalysts for enhanced catalytic activity. Polyelectrolytes also have an additional function of passivating the surface recombination centers of the underlying photoelectrode. These functional components are precisely assembled on a model photoanode (e.g., Fe2O3 and BiVO4) in a desired order and various combinations without degradation of their intrinsic properties. As a result, the performance of water oxidation photoanodes is synergistically enhanced. This study can enable the design and fabrication of novel solar‐to‐chemical energy conversion devices. [ABSTRACT FROM AUTHOR]