Search

Formation of thick, high energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes. Incomplete infilling results in a low capacitance and poor mechanical properties. Here we report a bottom-up infilling method to overcome these challenges. Electrodes up to 500 μm thick, formed from multi-walled carbon nanotubes and a composite of poly(3,4-ethylenedioxythiophene), polystyrene sulfonate and multi-walled carbon nanotubes are successfully infilled with a polyvinyl alcohol/phosphoric acid gel electrolyte. The exceptional mechanical properties of the multi-walled carbon nanotube-based electrode enable it to be rolled into a radius of curvature as small as 0.5 mm without cracking and retain 95% of its initial capacitance after 5000 bending cycles. The areal capacitance of our 500 μm thick poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, multi-walled carbon nanotube-based flexible solid supercapacitor is 2662 mF cm–2 at 2 mV s–1, at least five times greater than current flexible supercapacitors., The development of high performance flexible solid supercapacitors calls for an effective approach to infill gel electrolytes into porous electrodes. Here the authors report a bottom-up method to address this technical challenge, which leads to enhanced areal capacitance and durability.

The large mechanical energy storage capacity of metal-organic frameworks (MOFs) has suggested their promising potential as shock protective armor materials. Here, we performed shock compression of MOF (ZIF-8) film to understand the shock attenuation mechanisms in MOFs and evaluate the shock absorption efficiency. The shock wave was generated from the impact of an aluminum flyer plate on ZIF-8 film on a table-top shock apparatus. We recovered the ZIF-8 crystal film after shock compression for post-mortem analysis. We found out that the shock wave was absorbed by MOFs through powder compaction, nanopore-collapse, and chemical bond-breakage that were activated at distinct shock energies. The energy profiles obtained from photon Doppler velocimetry shows that ZIF-8 films are more efficient than PMMA (polymethyl methacrylate) in shock wave energy absorption.

In order to improve the safety of hexanitrohexaazaisowurtzitane (CL-20), submicron CL-20 particles were prepared by a siphon ultrasonic-assisted spray refining experimental device. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), and the impact sensitivity of the samples was tested. The results show that the particle size of siphon-refined CL-20 is about 800 nm~1 μm, which is more smooth, mellow, and dense than that of CL-20 prepared by a traditional pressure-refined method. The peak diffraction angle of pressure- and siphon-refined CL-20 is basically the same as that of raw CL-20, and their crystal forms are ε type. The peak strength of pressure- and siphon-refined CL-20 decreased obviously. The apparent activation energy of pressure-refined CL-20 and siphon-refined CL-20 is 13.3 kJ/mol and 11.95 kJ/mol higher than that of raw CL-20, respectively. The thermal stability of CL-20 is improved. The activation enthalpy (ΔH#) is significantly higher than that of raw CL-20, and the characteristic drop is 70.4% and 82.7% higher than that of raw CL-20. The impact sensitivity of siphon-refined CL-20 is lower than that of pressure-refined CL-20, so the safety performance of an explosive is improved obviously.

Recent investigations into the mechanical properties and mechanochemical reactions of metal-organic frameworks (MOFs) have suggested the potential for energy dissipation by multiple mechanisms. Although the possibility of efficient multifunctional shock dissipation by MOFs was suggested by static high pressure studies, there is little known about MOFs under shock compression. Here, we measure the attenuation of shock wave by the MOF denoted zeolitic-imidazolate framework (ZIF-8) in its desolvated, porous state. We find that shock wave dissipation by ZIF-8 occurred by multiple processes: powder compaction, nanopore-collapse, and chemical bond-breakage. The shock energy absorbance in ZIF-8 is proportional to ZIF-8 thickness, allowing the prediction of the thickness of MOF layer needed to attenuate shock waves to a desired lower energy. Compared with PMMA, often used as a standard, ZIF-8 attenuates 7 times more shock energy per unit mass for impacts at a lower velocity of 0.75 km/s and 2.5 times more at a higher velocity of 1.6 km/s. This research illustrates how to improve the ability to attenuate shock waves for personnel and equipment protection by engineering multifunctionality into the shock wave absorbing armor material.

The internal free volume of porous materials diminishes upon mechanical compression, and such volume collapse can have chemical consequences., The internal free volume of porous materials diminishes upon mechanical compression, and such volume collapse can have chemical consequences. We report here the endothermic bond breakage in a metal-organic framework (MOF) during compression-induced collapse. Upon bulk compression at 1.9 GPa, the effective number for Zr–O bonds between Zr(iv) ions and carboxylate groups in UiO-66 decreased from 4.0 to 1.9, as determined by EXAFS, and the internal free volume was synchronously collapsed. Consistent with the EXAFS data, IR spectra confirmed conversion of syn–syn bridging carboxylates to monodentate ligation, thus establishing mechanochemical reactions induced by external compression of MOFs. Substantial mechanical energy (∼4 kJ g–1) was absorbed by UiO-66 nanocrystals during compression, as demonstrated from nanocompression of single crystals (600 nm) in situ during scanning electron microscopy, which establishes the potential application of MOFs as mechanical energy absorbers for hydrostatic and shock compression.

Asthma is a chronic inflammatory, heterogeneous airway disease affecting millions of people around the world. Curcumin has been found to have anti-inflammatory and antifibrosis effects. Researchers reported that curcumin regulated Wnt/β-catenin signaling in lots of cells. However, whether curcumin regulates the levels of Wnt/β-Catenin signaling in lung tissues and DCs (dendritic cells) remains unclear. In this study, we assessed the effects of curcumin on DCs and asthma.C57BL/6 mice immunized with OVA (ovalbumin) were challenged thrice with an aerosol of OVA every second day for 8 days. Dexamethasone or curcumin was administered intraperitoneally to OVA-immunized C57BL/6 mice on day 24 once a day for 9 days. Mice were analyzed for effects of curcumin on asthma, inflammatory cell infiltration and cytokine levels in lung tissue. DCs were isolated from mouse bone morrow. The surface markers CD40, CD86 and CD11c of DCs was detected by FACS (fluorescence activated cell sorting) and the function of DCs was detected by mixed lymphocyte reaction. The expression of GSK-3β and β-catenin was detected by Western Blot.Results showed that OVA increased the number of inflammatory factors in BALF (bronchoalveolar lavage fluid), elevated lung inflammation scores in mice. Curcumin dose-dependently reversed the alterations induced by OVA in the asthmatic mice. Curcumin activated Wnt/β-catenin signaling pathway in DCs and asthmatic mouse lungs.Curcumin could influence the morphology and function of DCs, ease asthma symptom and inflammatory reaction through the activation of Wnt/β-catenin signaling. These results provide new evidence new evidence for application of curcumin on asthma.

Ocular complications associated with diabetes mellitus are progressive and becoming one of the most important causes of morbidity worldwide. The purpose of the study is to evaluate the protective effect of Polygonatum sibiricum polysaccharide, an important component of Polygonatum sibiricum, on ocular complications in streptozotocin-induced diabetes mellitus rats. Sprague Dawley rats were made diabetic with streptozotocin(60 mg/kg, i.v.) and then the rats were treated with Polygonatum sibiricum polysaccharide 200, 400 and 800 mg/kg.d by gavage for 12 weeks. Biochemical analysis indicated that Polygonatum sibiricum polysaccharide lowered the levels of fasting blood glucose and glycated hemoglobin in blood and elevated the levels of insulin and C-peptide in plasma of diabetes mellitus rats in a dose-dependent manner. Physical measurements revealed that Polygonatum sibiricum polysaccharide improved clinical symptoms of polydipsia, polyphagia, polyuria and weight loss in diabetes mellitus rats. The content of malondialdehyde and activity of superoxide dismutase in plasma were determined, and the data showed Polygonatum sibiricum polysaccharide suppressed oxidative stress reaction. Lens opacification was observed using slit lamp illumination, and the data showed Polygonatum sibiricum polysaccharide delayed cataract progression in a dose-dependent manner. Electroretinogram showed Polygonatum sibiricum polysaccharide treatment reversed the decrease of electroretinogram b and OPs2 waves’ amplitudes. Flash-visual evoked potential test indicated that the peak time of P2 wave was prolonged, and the amplitude of N2-P2 was lowered in diabetes mellitus group, and Polygonatum sibiricum polysaccharide suppressed these changes. Fundus fluorescein angiography showed Polygonatum sibiricum polysaccharide alleviated the retinal vasculopathy in a dose-dependent manner. In conclusion, these results suggest that the administration of Polygonatum sibiricum polysaccharide slows the progression of diabetic retinopathy and cataract through alleviating hyperglycemia and reducing oxidative stress in streptozotocin-induced diabetes mellitus rats.

Metal-organic frameworks (MOFs) are promising materials for shock energy dissipation via nanopore collapse and powder compaction. In this work, we measured shock wave energy attenuation by ZIF-8 (a MOF with a zinc-2-methylimidazolate framework) using a tabletop laser-driven flyer-plate apparatus. Aluminum flyer plates 75-um thick were accelerated to speeds up to 2.0 km/s to impact the ZIF-8 film. The pressure of the shock waves that break out from ZIF-8 was measured by photon Doppler velocimetry (PDV). By comparing the shock profile with and without ZIF-8, we deduced the shock pressure attenuated by the ZIF-8 layer. We identified the two-wave structure of shocks in ZIF-8 caused by nanopore collapse. Electron micrographs of recovered shocked ZIF-8 show distinct zones in the shocked material corresponding to shock powder compaction, nanopore collapse and chemical bond destruction.Metal-organic frameworks (MOFs) are promising materials for shock energy dissipation via nanopore collapse and powder compaction. In this work, we measured shock wave energy attenuation by ZIF-8 (a MOF with a zinc-2-methylimidazolate framework) using a tabletop laser-driven flyer-plate apparatus. Aluminum flyer plates 75-um thick were accelerated to speeds up to 2.0 km/s to impact the ZIF-8 film. The pressure of the shock waves that break out from ZIF-8 was measured by photon Doppler velocimetry (PDV). By comparing the shock profile with and without ZIF-8, we deduced the shock pressure attenuated by the ZIF-8 layer. We identified the two-wave structure of shocks in ZIF-8 caused by nanopore collapse. Electron micrographs of recovered shocked ZIF-8 show distinct zones in the shocked material corresponding to shock powder compaction, nanopore collapse and chemical bond destruction.

Metal–organic frameworks (MOFs) have potential applications as energy absorbing materials for shock wave energy mitigation due to their nanoporosity. Here we have examined km/s laser-driven flyer plate impacts on a prototypical MOF, ZIF-8. We observed particle fragmentation and morphological changes in microcrystals of ZIF-8 at lower shock pressures (≈2.5 GPa), and amorphization and structural collapse at higher pressures (≈8 GPa). High-speed emission spectroscopy revealed that 50 ns after flyer plate impacts, an emission pulse was generated by ZIF-8 resulting from chemical bonds that were broken and subsequently reformed. MOFs may prove useful in the dissipation of shock wave energy through large structural changes (free volume collapse and endothermic bond breakage).

Porous materials provide a plethora of technologically important applications that encompass molecular separations, catalysis, and adsorption. The majority of research in this field involves network solids constructed from multitopic constituents that, when assembled either covalently or ionically, afford macromolecular arrangements with micro- or meso-porous apertures. Recently, porous solids fabricated from discrete organic cages have garnered much interest due to their ease of handling and solution processability. Although this class of materials is a promising alternative to network solids, fundamental studies are still required to elucidate critical structure-function relationships that govern microporosity. Here, we report a systematic investigation of the effects of building block shape-persistence on the porosity of molecular cages. Alkyne metathesis and edge-specific postsynthetic modifications afforded three organic cages with alkynyl, alkenyl, and alkyl edges, respectively. Nitrogen adsorption experiments conducted on rapidly crystallized and slowly crystallized solids illustrated a general trend in porosity: alkynylalkenylalkyl. To understand the molecular-scale origin of this trend, we investigated the short and long time scale molecular motions of the molecular cages using ab initio molecular dynamics (AIMD) and classical molecular dynamics (MD) simulations. Our combined experimental and computational results demonstrate that the microporosity of molecular cages directly correlates with shape persistence. These findings discern fundamental molecular requirements for rationally designing porous molecular solids.

Conversion of cellulosic biomass to renewable chemicals such as 5-hydroxymethylfurfural (HMF) is of high current interest. Herein, we report a rare example of one-pot synthesis of HMF from glucose by tandem catalysis. The system is composed of a thermophilic glucose isomerase enzyme for glucose isomerization to fructose and a solid acid catalyst for fructose dehydration to HMF. A base (−NH2) functionalized mesoporous silica (aminopropyl-FMS) with large pore size was deployed successfully to immobilize and protect the thermophilic glucose isomerase in organic solvents at high temperature. The combination of this catalyst with a Bronsted acid (−SO3H) functionalized mesoporous silica (propylsulfonic acid-FMS) allowed us to conduct a one-pot transformation of glucose to HMF directly in a monophasic solvent system composed of tetrahydrofuran (THF) and H2O (4:1 v/v) with 61% yield of fructose and 30% yield of HMF at temperatures >363 K in 24 h.

Two manganese sulfates, [C2H6O2][MnSO4] (1) and [C4N2H12][Mn(SO4)2(H2O)] (2), were solvothermally synthesized in the presence of ethylene glycol and piperazine. Both compounds are constructed from 4-membered ring ladder chains made of MnO6 and SO4 units, with 1 displaying a 3D zeolite gismondine (GIS) framework and 2 possessing a 1D chain structure, respectively.

The deformation and mechanical behavior of individual zeolitic–imidazolate framework (ZIF-8) micro- and sub-microcrystals were observed under compression. Young’s modulus and volume changes as a function of applied pressure were determined on individual single crystals, offering insights in the relationship among structure, morphology, and mechanical properties. Dramatic volume decreases and amorphization were detected during compression over a pressure range of 0–4 GPa for individual 1.2 μm ZIF-8 microcrystals, and the deformed microcrystals partially recovered after pressure release. The orientation and size effects on the mechanical behavior of ZIF-8 nano- and microcrystals were also investigated. The presence of solvates within the pores of the ZIF-8 has a dramatic effect on the mechanical properties of the single crystals. Methanol-solvated ZIF-8 microcrystals are much less deformable than the desolvated microcrystals and shatter completely at very low applied force.