Templated 2D polymer heterojunctions for improved photocatalytic hydrogen production

2D polymers have emerged as one of the most promising classes of organic photocatalysts for solar fuel production due to their tunability, charge-transport properties, and robustness. They are however difficult to process and so there are limited studies into the formation of heterojunction materials incorporating these components. In this work, a novel templating approach is used to combine an imine-based donor polymer and an acceptor polymer formed through Knoevenagel condensation. Heterojunction formation is shown to be highly dependent on the topological match of the donor and acceptor polymers with the most active templated material found to be between three and nine times more active for photocatalysis than its constituent components. Transient absorption spectroscopy reveals that this improvement is due to faster charge separation and more efficient charge extraction in the templated heterojunction. The templated material shows a very high hydrogen evolution rate of >20 mmol h−1 m−2 with an ascorbic acid hole scavenger but also produces hydrogen in the presence of only water and a cobalt-based redox mediator. This suggests the improved charge-separation interface and reduced trapping accessed through this approach could be suitable for Z-scheme formation

Complex origins indicate a potential bridgehead introduction of an emerging amphibian invader (Eleutherodactylus planirostris) in China

Identifying the origins of established alien species is important to prevent new introductions in the future. The greenhouse frog (Eleutherodactylus planirostris), native to Cuba, the Bahamas, and the Cayman Islands, has been widely introduced to the Caribbean, North and Central America, Oceania and Asia. This invasive alien amphibian was recently reported in Shenzhen, China, but the potential introduction sources remain poorly understood. Based on phylogenetic analysis using mitochondrial 16S, COI and CYTB sequences, we detected a complex introduction origin of this species, which may be from Hong Kong, China, the Philippines, Panama and Florida, USA, all pointing to a bridgehead introduction. In addition, the nursery trade between the four countries or regions and mainland China from 2011 to 2020 was also significantly higher than other areas with less likelihood of introductions, which supported the molecular results. Our study provides the first genetic evidence of the potential sources of this emerging amphibian invader in mainland China, which may help develop alien species control strategies in the face of growing trade through globalization

Air-stable bismuth sulfobromide (BiSBr) visible-light absorbers : optoelectronic properties and potential for energy harvesting

ns2 compounds have recently attracted considerable interest due to their potential to replicate the defect tolerance of lead-halide perovskites and overcome their toxicity and stability limitations. However, only a handful of compounds beyond the perovskite family have been explored thus far. Herein, we investigate bismuth sulfobromide (BiSBr), which is a quasi-one-dimensional semiconductor, but very little is known about its optoelectronic properties or how it can be processed as thin films. We develop a solution processing route to achieve phase-pure, stoichiometric BiSBr films (ca. 240 nm thick), which we show to be stable in ambient air for over two weeks without encapsulation. The bandgap (1.91 ± 0.06 eV) is ideal for harvesting visible light from common indoor light sources, and we calculate the optical limit in efficiency (i.e., spectroscopic limited maximum efficiency, SLME) to be 43.6% under 1000 lux white light emitting diode illumination. The photoluminescence lifetime is also found to exceed the 1 ns threshold for photovoltaic absorber materials worth further development. Through X-ray photoemission spectroscopy and Kelvin probe measurements, we find the BiSBr films grown to be n-type, with an electron affinity of 4.1 ± 0.1 eV and ionization potential of 6.0 ± 0.1 eV, which are compatible with a wide range of established charge transport layer materials. This work shows BiSBr to hold promise for indoor photovoltaics, as well as other visible-light harvesting applications, such as photoelectrochemical cells, or top-cells for tandem photovoltaics

Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor–acceptor interface should equally control exciton dissociation. Here, we demonstrate that in low-bandgap non-fullerene acceptor (NFA) BHJs ultrafast donor-to-acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover, sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies, since energy level bending at the donor–NFA interface caused by the acceptors’ quadrupole moments prevents efficient exciton-to-charge-transfer state conversion at low IE offsets. The same bending, however, is the origin of the barrier-less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA-based blends, and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low-bandgap NFAs

Data from: Dispersal, niche, and isolation processes jointly explain species turnover patterns of nonvolant small mammals in a large mountainous region of China

Understanding the mechanisms that govern the spatial patterns of species turnover (beta diversity) has been one of the fundamental issues in biogeography. Species turnover is generally recognized as strong in mountainous regions, but the way in which different processes (dispersal, niche, and isolation) have shaped the spatial turnover patterns in mountainous regions remains largely unexplored. Here, we explore the directional and elevational patterns of species turnover for nonvolant small mammals in the Hengduan Mountains of southwest China and distinguish the relative roles of geographic distance, environmental distance, and geographic isolation on the patterns. The spatial turnover was assessed using the halving distance (km), which was the geographic distance that halved the similarity (Jaccard similarity) from its initial value. The halving distance was calculated for the linear, logarithmic, and exponential regression models between Jaccard similarity and geographic distance. We found that the east–west turnover is generally faster than the south–north turnover for high-latitudinal regions in the Hengduan Mountains and that this pattern corresponds to the geographic structure of the major mountain ranges and rivers that mainly extend in a south–north direction. There is an increasing trend of turnover toward the higher-elevation zones. Most of the variation in the Jaccard similarity could be explained by the pure effect of geographic distance and the joint effects of geographic distance, environmental distance, and average elevation difference. Our study indicates that dispersal, niche, and isolation processes are all important determinants of the spatial turnover patterns of nonvolant small mammals in the Hengduan Mountains. The spatial configuration of the landscape and geographic isolation can strongly influence the rate of species turnover in mountainous regions at multiple spatial scales

1 Tb/s WDM-OFDM-PON over 20km SSMF with Polarization Interleaving and Multi-band

1 Tb/s WDM-OFDM-PON with 50 GHz channel spacing is demonstrated, adopting the polarization interleaving and multi-band schemes. The transmission penalty induced by fiber nonlinearity is investigated by numerical simulations. ? OSA 2013.EI

Pisha sandstone: Causes, processes and erosion options for its control and prospects

Pisha sandstone is a special kind of soft rock in the semiarid region along the up and middle reaches of Yellow River and Loess Plateau and is severely eroded by wind, rainfall and gravity force. Pisha sandstone region is called “the most severe water loss and soil erosion in the world” and referred to as the “Earth Cancer” by local residents and experts both at home and abroad. The plan for the control of Pisha sandstone started in the 1950s. Since then a series of projects have been implemented, both engineering and vegetation measures have been developed and widely used to protect Pisha sandstone from erosion. Since seabuckthorn was introduced as a viable approach for soil erosion protection and its implementation resulted in a breakthrough to control Loess Plateau, it was considered as an important and efficient measure. Then the seabuckthorn flexible dam was proposed for coarse sediment retention and fine sediment deposition. And then a new comprehensive control model using consolidation materials combined with vegetation was proposed and promising results were achieved both in laboratory and field demonstrations. In the future, the complex erosion mechanism and ecological carrying capacity should be studied further and more efficient and practical comprehensive measures shall be developed. Moreover, monitoring systems shall be used to predict and detect the changes in the Pisha sandstone slope and structure. Keywords: Water loss and soil erosion, Land degradation, Ecological restoration, Seabuckthorn, Comprehensive measur

Transparent Ceramics Enabling High Luminous Flux and Efficacy for the Next-Generation High-Power LED Light

Transparent Ceramics Enabling High Luminous Flux and Efficacy for the Next-Generation High-Power LED Ligh

Small mammal dataset

Presence-absence dataset of small mammals in 164 counties of the Hengduan Mountain