A fractured microstructure design: A new type of piezoresistive sensor with ultra-high-pressure sensitivity (0.26 kPa(-1) ) in low pressure range (<2 kPa) and minimum detectable pressure of 9 Pa has been fabricated using a fractured microstructure design in a graphene-nanosheet-wrapped polyurethane (PU) sponge. This low-cost and easily scalable graphene-wrapped PU sponge pressure sensor has potential application in high-spatial-resolution, artificial skin without complex nanostructure design.

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Far-red and near infrared (NIR) emissive dyes have advantages in the development of fluorescent probes and labelling for bio-imaging in living systems since fluorescence in the long-wavelength region would generate minimum photo-toxicity to biological components, deep tissue penetration and minimal background from auto-fluorescence by bio-molecules. BODIPY dyes are attractive due to their excellent photo-physical properties and potential for fluorescence-based sensing and bio-imaging applications. Thus, numerous research papers have emerged to develop BODIPY-based dyes with absorption and emission in the long-wavelength spectral region (650-900 nm). This review summarizes the general strategies to obtain far-red and NIR BODIPYs. Moreover, their applications for fluorescent pH probes and imaging or labelling in living systems are highlighted.

Various methods have been exploited to replicate nacre features into artificial structural materials with impressive structural and mechanical similarity. However, it is still very challenging to produce nacre-mimetics in three-dimensional bulk form, especially for further scale-up. Herein, we demonstrate that large-sized, three-dimensional bulk artificial nacre with comprehensive mimicry of the hierarchical structures and the toughening mechanisms of natural nacre can be facilely fabricated via a bottom-up assembly process based on laminating pre-fabricated two-dimensional nacre-mimetic films. By optimizing the hierarchical architecture from molecular level to macroscopic level, the mechanical performance of the artificial nacre is superior to that of natural nacre and many engineering materials. This bottom-up strategy has no size restriction or fundamental barrier for further scale-up, and can be easily extended to other material systems, opening an avenue for mass production of high-performance bulk nacre-mimetic structural materials in an efficient and cost-effective way for practical applications.

Recently, porous hydrophobic/oleophilic materials (PHOMs) have been shown to be the most promising candidates for cleaning up oil spills; however, due to their limited absorption capacity, a large quantity of PHOMs would be consumed in oil spill remediation, causing serious economic problems. In addition, the complicated and time-consuming process of oil recovery from these sorbents is also an obstacle to their practical application. To solve the above problems, we apply external pumping on PHOMs to realize the continuous collection of oil spills in situ from the water surface with high speed and efficiency. Based on this novel design, oil/water separation and oil collection can be simultaneously achieved in the remediation of oil spills, and the oil sorption capacity is no longer limited to the volume and weight of the sorption material. This novel external pumping technique may bring PHOMs a step closer to practical application in oil spill remediation.

The generic case of a ferroelectric solid solution is considered wherein different symmetry phases located at opposing ends of the diffusionless phase diagram are separated by a morphotropic boundary (MB). It is shown that the Landau theory of weak first-order phase transformations automatically predicts vanishing of the anisotropy of polarization, continuity of thermodynamic properties, and a drastic decrease in domain wall energy near the MB line that results in the formation of adaptive ferroelectric nanodomain states. Low-resolution diffraction from these adaptive states acquired at the coherence lengths of elastic x-ray or neutron scattering probes will produce the same diffraction pattern as attributed to monoclinic (MA,MB,MC) phases. It is further shown that the electric- or stress-field-induced reconfiguration of these adaptive nanodomain states results in a softening of the piezoelectric, elastic, and dielectric properties near the MB line. In addition, the spherical degeneration of the polarization direction, reflecting the decoupling of the polarization from the crystal lattice at the MB, also predicts the formation of a polar glass state whose properties should be similar to the special properties of amorphous ferromagnets. In particular, the vanishing of the polarization anisotropy at the MB should result in ferroelectric domains with irregular shapes exhibiting high configurational sensitivity to external forces. The theory further predicts that two tricritical points will occur on the line of paraelectric→ferroelectric transitions and it is shown that all two-phase equilibrium lines of the diffusionless phase diagram—including the MB line—must be replaced by two-phase fields. Within these two-phase fields, the adjacent ferroelectric-ferroelectric and paraelectric-ferroelectric phases coexist. Possible topologies of the equilibrium MB phase diagram illustrating these two-phase equilibrium fields are computed and discussed.

Ultrathick electrode design is a promising strategy to enhance the specific energy of Li-ion batteries (LIBs) without changing the underlying materials chemistry. However, the low Li-ion conductivity caused by ultralong Li-ion transport pathway in traditional random microstructured electrode heavily deteriorates the rate performance of ultrathick electrodes. Herein, inspired by the vertical microchannels in natural wood as the highway for water transport, the microstructures of wood are successfully duplicated into ultrathick bulk LiCoO (LCO) cathode via a sol-gel process to achieve the high areal capacity and excellent rate capability. The X-ray-based microtomography demonstrates that the uniform microchannels are built up throughout the whole wood-templated LCO cathode bringing in 1.5 times lower of tortuosity and ≈2 times higher of Li-ion conductivity compared to that of random structured LCO cathode. The fabricated wood-inspired LCO cathode delivers high areal capacity up to 22.7 mAh cm (five times of the existing electrode) and achieves the dynamic stress test at such high areal capacity for the first time. The reported wood-inspired design will open a new avenue to adopt natural hierarchical structures to improve the performance of LIBs.

CONSPECTUS: Aromaticity is one of the most important concepts in organic chemistry to understand the electronic properties of cyclic πconjugated molecules. Over a century, different aromaticity rules have been developed and validated. For planar monocyclic conjugated polyenes (also known as [n]annulenes), they will be aromatic if they contain [4N + 2] π electrons according to Huckel's rule, or antiaromatic if they have [4N] π electrons. Topological change from a planar to a half-twisted Mobius strip will lead to [4N] ([4N + 2]) aromaticity (antiaromaticity), which is just inverse to Huckel's rule. When the molecules are excited into the first triplet excited state, the Huckel (anti)aromaticity observed in the ground state will become reversed according to Baird's rule. Strictly speaking, these basic rules are only applicable for monocyclic conjugated systems, but some polycyclic systems such as porphyrinoids may also follow these rules if there is a dominant [n]annulene-like conjugation pathway. On the other hand, all-benzenoid polycyclic aromatic hydrocarbons usually display local aromaticity with π electrons predominantly localized at certain benzene rings according to Clar's aromatic sextet rule. In recent years, some proaromatic and antiaromatic molecules with even number of paired electrons have been found to exhibit open-shell diradical character and unique optical, electronic, and magnetic activities. One of the major driving forces is their intrinsic tendency to become aromatic in the open-shell diradical/polyradical forms. A number of stable diradicaloids and linear polyradicaloids have been successfully synthesized by using thermodynamic and kinetic stabilizing strategies. Herein, our particular interest is a type of macrocyclic polyradicaloid in which multiple frontier π-electrons are antiferromagnetically coupled with each other in a cyclic mode. Formally, these free electrons may behave like normal π-electrons in the [n]annulenes, and thus, it raises questions about their possible global aromaticity and which rule they will follow. In the past 5 years, our group has synthesized a series of macrocyclic polyradicaloids and systematically investigated their global aromaticity and electronic properties. Some important findings include: (1) global (anti)aromaticity is generally observed, but there is a balance between local aromaticity and global aromaticity; (2) most of these molecules follow Huckel's rule in the singlet state and display respective (anti)aromatic characteristics; (3) in some special cases, both Huckel's rule and Baird's rule can be applicable, and a unique annulene-within-an-annulene super-ring structure was demonstrated for the first time; (4) global antiaromaticity in the transition state is also important and a slow valence tautomerization process was observed in a supercyclobutadiene tetraradicaloid. These studies demonstrate how these open-shell macrocyclic polyradicaloids adapt their geometry and spin state to reach the lowest-energy state (aromatic). In this Account, we will main...