Covalent organic
frameworks (COFs) with well-tailored channels
are able to accommodate ions and offer their conduction pathway. However,
due to strong Coulombic interaction and the lack of transport medium,
directly including lithium salts into the channels of COFs results
in limited ion transport capability. Herein, we propose a strategy
of incorporating low-molecular-weight polyethylene glycol (PEG) into
COFs with anionic, neutral, or cationic skeletons to accelerate Li+ conduction. The PEG confined in the well-aligned channels
retains high flexibility and Li+ solvating ability. The
ion conductivity of PEG included in a cationic COF can reach 1.78
× 10–3 S cm–1 at 120 °C.
The simplicity of this strategy as well as the diversity of crystalline
porous materials holds great promise to design high-performance all-solid-state
ion conductors.
Abstract. The rapidly intensifying process of ocean acidification (OA) due to
anthropogenic CO2 is not only depleting carbonate ions necessary
for calcification but also causing acidosis and disrupting internal pH
homeostasis in several marine organisms. These negative consequences of OA on
marine calcifiers, i.e. oyster species, have been very well documented in
recent studies; however, the consequences of reduced or impaired
calcification on the end-product, shells or skeletons, still remain one of
the major research gaps. Shells produced by marine organisms under OA are
expected to show signs of dissolution, disorganized microstructure and
reduced mechanical properties. To bridge this knowledge gap and to test the
above hypothesis, we investigated the effect of OA on juvenile shells of the
commercially important oyster species, Magallana angulata,
at ecologically and climatically relevant OA levels (using pH 8.1, 7.8, 7.5,
7.2). In lower pH conditions, a drop of shell hardness and stiffness was
revealed by nanoindentation tests, while an evident porous internal
microstructure was detected by scanning electron microscopy. Crystallographic
orientation, on the other hand, showed no significant difference with
decreasing pH using electron back-scattered diffraction (EBSD). These results
indicate the porous internal microstructure may be the cause of the reduction
in shell hardness and stiffness. The overall decrease of shell density observed
from micro-computed tomography analysis indicates the porous internal
microstructure may run through the shell, thus inevitably limiting the
effectiveness of the shell's defensive function. This study shows the potential
deterioration of oyster shells induced by OA, especially in their early life
stage. This knowledge is critical to estimate the survival and production of
edible oysters in the future ocean.
Biofouling refers to the unfavourable attachment and accumulation of marine sessile organisms (e.g. barnacles, mussels and tubeworms) on the solid surfaces immerged in ocean. The enormous economic loss caused by biofouling in combination with the severe environmental impacts induced by the current antifouling approaches entails the development of novel antifouling strategies with least environmental impact. Inspired by the superior antifouling performance of the leaves of mangrove tree , here we propose to combat biofouling by using a surface with microscopic ridge-like morphology. Settlement tests with tubeworm larvae on polymeric replicas of leaves confirm that the microscopic ridge-like surface morphology can effectively prevent biofouling. A contact mechanics-based model is then established to quantify the dependence of tubeworm settlement on the structural features of the microscopic ridge-like morphology, giving rise to theoretical guidelines to optimize the morphology for better antifouling performance. Under the direction of the obtained guidelines, a synthetic surface with microscopic ridge-like morphology is developed, exhibiting antifouling performance comparable to that of the replica. Our results not only reveal the underlying mechanism accounting for the superior antifouling property of the leaves, but also provide applicable guidance for the development of synthetic antifouling surfaces.
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