Superaerophobic hydrogels for enhanced electrochemical and photoelectrochemical hydrogen production

The efficient removal of gas bubbles in (photo)electrochemical gas evolution reactions is an important but underexplored issue. Conventionally, researchers have attempted to impart bubble-repellent properties (so-called superaerophobicity) to electrodes by controlling their microstructures. However, conventional approaches have limitations, as they are material specific, difficult to scale up, possibly detrimental to the electrodes' catalytic activity and stability, and incompatible with photoelectrochemical applications. To address these issues, we report a simple strategy for the realization of superaerophobic (photo)electrodes via the deposition of hydrogels on a desired electrode surface. For a proof-of-concept demonstration, we deposited a transparent hydrogel assembled from M13 virus onto (photo)electrodes for a hydrogen evolution reaction. The hydrogel overlayer facilitated the elimination of hydrogen bubbles and substantially improved the (photo)electrodes' performances by maintaining high catalytic activity and minimizing the concentration overpotential. This study can contribute to the practical application of various types of (photo)electrochemical gas evolution reactions

Longitudinal evolution of cortical thickness signature reflecting Lewy body dementia in isolated REM sleep behavior disorder: a prospective cohort study

Background The isolated rapid-eye-movement sleep behavior disorder (iRBD) is a prodromal condition of Lewy body disease including Parkinson's disease and dementia with Lewy bodies (DLB). We aim to investigate the longitudinal evolution of DLB-related cortical thickness signature in a prospective iRBD cohort and evaluate the possible predictive value of the cortical signature index in predicting dementia-first phenoconversion in individuals with iRBD. Methods We enrolled 22 DLB patients, 44 healthy controls, and 50 video polysomnography-proven iRBD patients. Participants underwent 3-T magnetic resonance imaging (MRI) and clinical/neuropsychological evaluations. We characterized DLB-related whole-brain cortical thickness spatial covariance pattern (DLB-pattern) using scaled subprofile model of principal components analysis that best differentiated DLB patients from age-matched controls. We analyzed clinical and neuropsychological correlates of the DLB-pattern expression scores and the mean values of the whole-brain cortical thickness in DLB and iRBD patients. With repeated MRI data during the follow-up in our prospective iRBD cohort, we investigated the longitudinal evolution of the cortical thickness signature toward Lewy body dementia. Finally, we analyzed the potential predictive value of cortical thickness signature as a biomarker of phenoconversion in iRBD cohort. Results The DLB-pattern was characterized by thinning of the temporal, orbitofrontal, and insular cortices and relative preservation of the precentral and inferior parietal cortices. The DLB-pattern expression scores correlated with attentional and frontal executive dysfunction (Trail Making Test-A and B: R = − 0.55, P = 0.024 and R = − 0.56, P = 0.036, respectively) as well as visuospatial impairment (Rey-figure copy test: R = − 0.54, P = 0.0047). The longitudinal trajectory of DLB-pattern revealed an increasing pattern above the cut-off in the dementia-first phenoconverters (Pearsons correlation, R = 0.74, P = 6.8 × 10−4) but no significant change in parkinsonism-first phenoconverters (R = 0.0063, P = 0.98). The mean value of the whole-brain cortical thickness predicted phenoconversion in iRBD patients with hazard ratio of 9.33 [1.16–74.12]. The increase in DLB-pattern expression score discriminated dementia-first from parkinsonism-first phenoconversions with 88.2% accuracy. Conclusion Cortical thickness signature can effectively reflect the longitudinal evolution of Lewy body dementia in the iRBD population. Replication studies would further validate the utility of this imaging marker in iRBD

Brain structural correlates of subjective sleepiness and insomnia symptoms in shift workers

BackgroundStudies on the brain structures of shift workers are limited; thus, this cross-sectional study aimed to compare the brain structures and the brain structural correlates of subjective sleepiness and insomnia symptoms between shift workers and non-shift workers.MethodsShift workers (n = 63) and non-shift workers (n = 58) completed questionnaires assessing subjective sleepiness and insomnia symptoms. Cortical thickness, cortical surface area, and subcortical volumes were measured by magnetic resonance imaging. The brain morphometric measures were compared between the groups, and interaction analyses using the brain morphometric measures as the dependent variable were performed to test the interactions between the study group and measures of sleep disturbance (i.e., subjective sleepiness and insomnia symptoms).ResultsNo differences in cortical thickness, cortical surface area, or subcortical volumes were detected between shift workers and non-shift workers. A single cluster in the left motor cortex showed a significant interaction between the study group and subjective sleepiness in the cortical surface area. The correlation between the left motor cortex surface area and the subjective sleepiness level was negative in shift workers and positive in non-shift workers. Significant interaction between the study group and insomnia symptoms was present for the left/right putamen volumes. The correlation between the left/right putamen volumes and insomnia symptom levels was positive in shift workers and negative in non-shift workers.ConclusionLeft motor cortex surface area and bilateral putamen volumes were unique structural correlates of subjective sleepiness and insomnia symptoms in shift workers, respectively

Improving light-harvesting and catalytic efficiency of water oxidation photoanodes with nanoparticle-polymer hybrid films

Solar water oxidation has been recognized as a promising technology to produce clean energy resources using unlimited solar energy. In principle, semiconducting materials with a proper bandgap and band-edge positions can be used for solar water oxidation. However, most semiconducting materials have low photocatalytic efficiency due to their intrinsic problems such as narrow absorption band with a low light-absorption coefficient or slow water oxidation kinetics. To address these problems, it is necessary to develop a comprehensive strategy to modify semiconducting materials. In this study, we successfully developed a highly efficient water oxidation photoanode through the integration of functional materials on semiconductor surfaces with layer-by-layer assembly methods. The performance of the photoanodes were significantly improved after the modification with these components due to their respective roles: improved light harvesting in the band absorption by Ag nanoparticles(NPs), utilization of Infrared light by upconversion NPs, suppression of surface recombination by polyelectrolyte passivation, and increased catalytic activity by polyoxometalate catalysts

Layer-by-Layer Assembled Photoelectrochemical Devices for Solar-to-Chemical Conversion

Efficient harvesting and utilization of unlimited solar energy to produce valuable chemicals, the so-called artificial photosynthesis, has been a holy grail of scientists and engineers to solve modern energy and environmental problems. In principle, we can produce various fine chemicals including chemical fuels through a series of photoelectrochemical processes by rational design of photocatalytic systems. Despite numerous efforts made for decades, its practical application is limited by low efficiency and stability of photosynthetic devices. Considering the diversity and excellent properties of functional components developed to date, the limitation may be partly due to the absence of a general and simple method to precisely assemble them in various combinations without altering their properties to build an integrated photosynthetic device. To solve this problem, we have studied to develop a simple modular platform to fabricate various photoelectrochemical devices using the huge library of functional components reported to date. For example, we found that layer-by-layer assembly technique can serve as a versatile and promising method to build and engineer various photoelectrodes for solar water oxidation. In this talk, I will present our progress over the past few years in the development of the modular photosynthetic devices and discuss the potential and limitations

Enhancement of Visible Light Driven Photoelectrochemical Performances of Hematite via Layer-by-Layer Self Assembly (LbL)

Hematite is one of promising materials for visible light driven photoelectrochemical water splitting due to its narrow band gap, abundance and inexpensiveness. For their practical applications, however, there still remain many weakness to be solved such as low photocurrent efficiency, high onset potential for catalytic water splitting and low stability under neutral pH conditions. To address such issues, we developed a novel modification method for enhancing photocatalytic activity of hematite by utilizing layer-by-layer self-assembly (LbL) technique. We found that the surface modification of hematite with polyelectrolytes and molecular oxide catalysts led to the increase of photocurrent efficiency approximately 2 to 5 times, the decrease of onset potential, and the improvement of electrode stability against photocorrosion at the same time. In principle, our findings can be further applied to virtually any kinds of photoelectrodes and provide a general method for construction of hybrid photocatalytic systems

Catalytic Multilayers for Efficient Solar Water Oxidation through Catalyst Loading and Surface-State Passivation of BiVO4 Photoanodes

We studied the kinetics of photoelectrochemical (PEC) water oxidation using a model photoanode BiVO4 modified with various water oxidation catalysts (WOCs) by electrochemical impedance spectroscopy. In particular, we prepared BiVO4 photoanodes with catalytic multilayers (CMs), where cationic polyelectrolytes and anionic polyoxometalate (POM) WOCs were assembled in a desired amount at a nanoscale precision, and compared their performance with those with well-known WOCs such as cobalt phosphate (CoPi) and NiOOH. Our comparative kinetics analysis suggested that the deposition of the CMs improved the kinetics of both the photogenerated charge carrier separation/transport in bulk BiVO4 due to passivation of surface recombination centers and water oxidation at the electrode/electrolyte interface due to deposition of efficient molecular WOCs. On the contrary, the conventional WOCs were mostly effective in the former and less effective in the latter, which is consistent with previous reports. These findings explain why the CMs exhibit an outstanding performance. We also found that separated charge carriers can be efficiently transported to POM WOCs via a hopping mechanism due to the delicate architecture of the CMs, which is reminiscent of natural photosynthetic systems. We believe that this study can not only broaden our understanding on the underlying mechanism of PEC water oxidation but also provide insights for the design and fabrication of novel electrochemical and PEC devices, including efficient water oxidation photoanodes