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Research has been conducted on the 24-nortriterpene derivatives. The route to these derivatives has been developed in preparing the betulinic acid derivatives and the results indicate that the key step in transformation is the A-ring Suarez cleavage.

Understandingof H- and J-aggregation behaviors in fluorene-based polymers is significantboth for determining the origin of various red-shifted emissions occurringin blue-emitting polyfluorenes and for developing polyfluorene-baseddevice performance. In this contribution, we demonstrate a new theoryof the H- and J-aggregation of polyfluorenes and oligofluorenes, andunderstand the influence of chromosphere aggregation on their photoluminescentproperties. H- and J-aggregates are induced by a continuous increasingconcentration of the oligofluorene or polyfluorene solution. A relaxedmolecular configuration is simulated to illustrate the spatial arrangementof the bonding of fluorenes. It is indicated that the relaxed stateadopts a 21helical backbone conformation with a torsionangle of 18° between two connected repeat units. This configurationmakes the formation of H- and J-aggregates through the strong π–πinteraction between the backbone rings. A critical aggregation concentrationis observed to form H- and J-aggregates for both polyfluorenes andoligofluorenes. These aggregates show large spectral shifts and distinctshape changes in photoluminescent excitation (PLE) and emission (PL)spectroscopy. Compared with “isolated” chromophores,H-aggregates induce absorption spectral blue-shift and fluorescencespectral red-shift but largely reduce fluorescence efficiency. “Isolated”chromophores not only refer to “isolated molecules”but also include those associated molecules if their conjugated backbonesare not compact enough to exhibit perturbed absorption and emission.J-aggregates induce absorption spectral red-shift and fluorescencespectral red-shift but largely enhance fluorescence efficiency. ThePLE and PL spectra also show that J-aggregates dominate in concentratedsolutions. Different from the excimers, the H- and J-aggregate formationchanges the ground-state absorption of fluorene-based chromophores.H- and J-aggregates show changeable absorption and emission derivedfrom various interchain interactions, unlike the β phase, whichhas relatively fixed absorption and emission derived from an intrachaininteraction. [ABSTRACT FROM AUTHOR]

Acetylatedlignin (ACL), obtained from the acetylation of alkalilignin (AL), has been found to self-assemble into ordered colloidalspheres in a THF/H2O media. This colloid formation causesthe color of ACL to change from dark brown to light yellow. ACL moleculesform colloidal spheres at critical water content (CWC) of 48 vol %for an initial concentration of ACL in THF of 0.4 mg/mL. The colloidizationprocess is completed at a water content of 77.75 vol %. The colloidalspheres formed from the gradual hydrophobic aggregation of ACL wereapproximately 80 nm in size. The concentration of Fe3+beforeand after colloid formation did not change significantly, which indicatesthat the whitening of ACL colloids is not influenced by metal ions,but is affected by the rearrangement of chromophores during self-assemblyand the light reflectance of uniform particles. Self-assembly of ACLinto colloidal spheres not only whitens the dark color of lignin butalso provides a novel method to prepare ordered lignin-based nanomaterials. [ABSTRACT FROM AUTHOR]

The components and structures of the solid-electrolyte interphase (SEI) are critical for stable cycling of lithium metal batteries (LMBs). LiF has been widely studied as the dominant component of SEI, but Li 2 O, which has a much lower diffusion barrier for Li + , has rarely been investigated as the dominant component of SEI. The effect of Li 2 O-dominated SEI on electrochemical performance still remains elusive. Herein, an ultrastrong coordinated cosolvation diluent, 2,3-difluoroethoxybenzene (DFEB), is designed to modulate solvation structure and tailor Li 2 O-dominated SEI for stable LMBs. In the DFEB-based LHCE (DFEB-LHCE), DFEB intensively participates in the first solvation shell and synergizes with FSI - to tailor an Li 2 O-dominated inorganic-rich SEI which is different from the LiF-dominated SEI formed in conventional LHCE. Benefiting from this special SEI architecture, a high Coulombic efficiency (CE) of 99.58% in Li||Cu half cells, stable voltage profiles, and dense and uniform lithium deposition, as well as effective inhibition of Li dendrite formation in the symmetrical cell, are achieved. More importantly, the DFEB-LHCE can be matched with various cathodes such as LFP, NCM811, and S cathodes, and the Li||LFP full cell using DFEB-LHCE possesses 85% capacity retention after 650 stable cycles with 99.9% CE. Especially the 1.5 Ah practical lithium metal pouch cell achieves an excellent capacity retention of 89% after 250 cycles with a superb average CE of 99.93%. This work unravels the superiority of the Li 2 O-dominated SEI and the feasibility of tailoring SEI components through modulation of solvation structures.

Nano approaches are practical strategies to boost the thermoelectric figure of merit due to the strong phonon scattering from the grain boundaries and nanoinclusions. Here, we have reported a strong phonon scattering at the heterogeneous interfaces of Mg 2 Sn/Mg 3 Sb 2 high-content nanocomposites (HCnCs). As a result, a significantly reduced lattice thermal conductivity of 1.09 W m -1 K -1 was observed in the equimolar Mg 2 Sn/Mg 3 Sb 2 HCnC, 80% lower than pure Mg 2 Sn and 25% lower than pure Mg 3 Sb 2 . As a result, a high ZT ∼ 1.13 at 773 K was achieved in the Mg 2 Sn/Mg 3 Sb 2 HCnC. Furthermore, various defects, including solid solutions, nanoinclusions, and misfit dislocations, were observed in both the Mg 3 Sb 2 phase and the Mg 2 Sn phase through the microstructure characterization.

As a promising high energy density electrode material for rechargeable batteries, lithium (Li) metal is still suffering from air/water instability due to its highly reactive nature. In addition, the Li dendrite issue in Li metal batteries needs to be resolved to ensure the safety of batteries and for wide applications. Herein, we demonstrate that a simple compact GaO x layer formed using liquid metal (LM) can act as an artificial solid electrolyte interphase to block moisture and oxygen in the air from corroding the lithium metal. Interestingly, GaO x that covered the electrode effectively inhibits Li dendrite growth in electrochemistry cycling, ensuring the safety of Li metal batteries. The exposed composite Li metal anode (exposed under ambient air with relative humidity (RA) ≈ 75% for 5 h) not only shows a superior stability (symmetrical cell) but also delivers an elevated cycling stability (>500 cycles at 0.5 and 1 C) with a sulfur@C cathode in the full-cell configuration. Our work provides a new pathway for the large-scale applications of the air/water-tolerant Li metal anode in rechargeable batteries.

Solid electrolyte interphase (SEI) is crucial for suppressing Li dendrite growth in high-energy lithium metal (LiM) batteries. Unfortunately, the naturally formed SEI on the LiM anode surface in carbonate electrolytes cannot suppress Li dendrites, resulting in a continuous consumption of electrolytes and LiM during cycling. Artificial SEI normally lacks self-healing and self-regulating capability, gradually losing the effectiveness during cycling. In this work, we report the self-regulating phenomenon of LiRAP-ASEI that can effectively suppress Li dendrites and is investigated using in situ optical microscopy and COMSOL multiphysics simulation. The effectiveness of self-regulated LiRAP-ASEI is further evaluated in the most aggressive Li/sulfur cells with a lean electrolyte (10 μL mAh -1 ) and LiRAP-ASEI/LiM (2.5-fold excess of LiM). The LiRAP@Cu∥sulfur@C cells show a stable 3000 cycle life at a current density of 11.5 mA cm -2 . The self-regulated phenomenon holds great promise for the development of high-energy-density LMBs.

Three-dimensional (3D) lithiophilic host is one of the most effective ways to regulate the Li dendrites and volume change in working Li metal anode. The state-of-the-art 3D lithiophilic hosts are facing one main challenge in that the lithiophilic layer would melt or fall off in high-temperature environment when using the thermal infusion method. Herein, a 3D porous CuZn alloy host containing anchored lithiophilic Zn sites is employed to prestore Li using the thermal infusion strategy, and a 3D composite Li is thus fabricated. Benefiting from the lithiophilic Zn sites with a strong adsorption capacity with Li, which is based on the analyses of the nucleation overpotential, binding energy calculation, and the operando optical observation of Li plating/stripping behaviors, facile uniform Li nucleation and dendrite-free Li deposition could be achieved in the interior of the 3D porous CuZn alloy host and the 3D composite Li shows remarkable enhancement in electrochemical performance.

We report here an intriguing hybrid conductive hydrogel as electrode for high-performance flexible supercapacitor. The key is using a rationally designed water-soluble ABA triblock copolymer (termed as IAOAI) containing a central poly(ethylene oxide) block (A) and terminal poly(acrylamide) (PAAm) block with aniline moieties randomly incorporated (B), which was synthesized by reversible additional fragment transfer polymerization. The subsequent copolymerization of aniline monomers with the terminated aniline moieties on the IAOAI polymer generates a three-dimensional cross-linking hybrid network. The hybrid hydrogel electrode demonstrates robust mechanical flexibility, remarkable electrochemical capacitance (919 F/g), and cyclic stability (90% capacitance retention after 1000 cycles). Moreover, the flexible supercapacitor based on this hybrid hydrogel electrode presents a large specific capacitance (187 F/g), superior to most reported conductive hydrogel-based supercapacitors. With the demonstrated additional favorable cyclic stability and excellent capacitive and rate performance, this hybrid hydrogel-based supercapacitor holds great promise for flexible energy-storage device.

We report here a supramolecular hydrogel displaying a wide array of dynamic desirable properties. The key is using an ABA triblock copolymer containing a central poly(ethylene oxide) block and terminal poly( N -isopropylacrylamide) (PNIPAm) block with ureido pyrimidinone (UPy) moieties randomly incorporated. Rapid hydrogelation is triggered upon increasing temperature above the lower critical solution temperature (LCST) of the supramolecular copolymer, where PNIPAm segments dehydrate and assemble into micelles, which subsequently provide hydrophobic microenvironments promoting UPy dimerization to grab polymer chains, thus forming hydrogen-bonded cross-linking points. The supramolecular hydrogels demonstrate fascinating shear-thinning, self-healable, thermo-reversible, and injectable properties, which allow withstanding repeated deformations and 3D construction of complex objects. Mesenchymal stem cells mixed with the hydrogel and injected through needles remain highly viable (>90%) during the encapsulation and delivery process. With these attractive dynamic physical properties, the supramolecular hydrogel holds great promise to support cell or drug therapies.

Utilizing a total synthesis approach, the first 8-heterocyclyltetracyclines were designed, synthesized, and evaluated against panels of tetracycline- and multidrug-resistant Gram-positive and Gram-negative pathogens. Several compounds with balanced, highly potent in vitro activity against a broad range of bacterial isolates were identified through structure-activity relationships (SAR) studies. One compound demonstrated the best antibacterial activity against Pseudomonas aeruginosa both in vitro and in vivo for tetracyclines reported to date.

Here we have obtained a temperature responsive melamine sponge with a controllable wettability between superhydrophilicity and superhydrophobicity by grafting the octadecyltrichlorosilane and thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) onto the surface of melamine sponge skeletons. The whole process included the silanization in which step the rough surface with low surface energy and the NH 2 were provided, and the atom transfer radical polymerization which ensured the successful grafting of PNIPAAm onto the skeleton's surface. The product exhibits a good reversible switch between superhydrophilicity and superhydrophobicity by changing the temperature below or above the lower critical solution temperature (LCST, about 32 °C) of PNIPAAm, and the modified sponge still retains a good responsiveness after undergoing two temperature switches for 20 cycles. Simultaneously, the functionalized sponges could be used to absorb the oil under water at 37 °C, and they released the absorbed oil in various ways under water at 20 °C, showing wide potential applications including oil/water separation.

A series of novel hexacyclic tetracycline analogues ("hexacyclines") was designed, synthesized, and evaluated for antibacterial activity against a wide range of clinically important bacteria isolates, including multidrug-resistant, Gram-negative pathogens. Valuable structure-activity relationships were identified, and several hexacyclines displayed potent, broad spectrum antibacterial activity, including promising anti-Pseudomonas aeruginosa activity in vitro and in vivo.

We report a facile method to synthesize Fe3O4@polydopamine (PDA)-Ag core-shell microspheres. Ag nanoparticles (NPs) are deposited on PDA surfaces via in situ reduction by mussel-inspired PDA layers. High catalytic activity and fast adsorption of a model dye methylene blue (MB) at different pH values are achieved mainly due to the presence of monodisperse Ag NPs and electrostatic interactions between PDA and MB. The as-prepared Fe3O4@PDA-Ag microspheres also show high cyclic stability (>27 cycles), good acid stability, and fast regeneration ability, which can be achieved efficiently within several minutes by using NaBH4 as the desorption agent, showing great potentials in a wide range of applications.

The C-8 position of the tetracyclines has been largely underexplored because of limitations in traditional semisynthetic techniques. Employing a total synthetic approach allowed for modifications at the C-7 and C-8 positions, enabling the generation of structure-activity relationships for overcoming the two most common tetracycline bacterial-resistance mechanisms: ribosomal protection (tet(M)) and efflux (tet(A)). Ultimately, several compounds were identified with balanced activity against both Gram-positive and Gram-negative bacteria, including pathogens bearing both types of tetracycline-resistance mechanisms. Compounds were screened in a murine systemic infection model to rapidly identify compounds with oral bioavailability, leading to the discovery of several compounds that exhibited efficacy when administered orally in murine pyelonephritis and pneumonia models.

The paper reports on a headspace gas chromatographic (HS-GC) method for the determination of methoxyl in lignin. The method involves the quantitive cleavage of methoxyl with hydroiodic acid (HI) to form methyl iodide in a closed headspace sample vial at 130 °C for 30 min. After HI has been added, the sample is neutralized by injecting a sodium hydroxide solution; the methyl iodide in the vial was determined by HS-GC using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD < 0.69%) and accuracy (RSD < 3.5%) for the quantification of methoxyl content in lignin. The present method is simple and accurate and can be used for the efficient determination of methoxy1 content in lignin and related materials.

Utilizing a fully synthetic route to tetracycline analogues, the C-9 side-chain of the fluorocyclines was optimized for both antibacterial activity and oral efficacy. Compounds were identified that overcome both efflux (tet(K), tet(A)) and ribosomal protection (tet(M)) tetracycline-resistance mechanisms and are active against Gram-positive and Gram-negative organisms. A murine systemic infection model was used as an oral efficacy screen to rapidly identify compounds with oral bioavailability. Two compounds were identified that exhibit both oral bioavailability in rat and clinically relevant bacterial susceptibility profiles against major respiratory pathogens. One compound demonstrated oral efficacy in rodent lung infection models that was comparable to marketed antibacterial agents.

Sequentially adsorbed multilayers composed of sodium lignosulfonate (SL) and poly(diallyldimethylammonium chloride) (PDAC) were built up by a layer-by-layer self-assembly technique to investigate the adsorption characteristics of SL microgels for sensitivity improvement. The effect of molecular weight on the adsorption characteristics was investigated by light scattering, UV-visible spectroscopy, ellipsometer, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements. Results show that the self-assembly of SL microgels and PDAC is not mainly driven by electrostatic interaction but by cation-π interaction and hydrophobic interaction. The Coulomb interaction in SL microgels causes a "slow mode" peak in dynamic light scattering measurement, but it can be completely suppressed when SL is dissolved in 1.2 mol/L NaCl solutions due to charge-screening. The SL in 1.2 mol/L NaCl solutions can be well adsorbed on a PDAC surface, indicating that the electrostatic interaction is not the main driving force. The presence of cation-π interaction between SL and PDAC is detected by a stoichiometric ratio of SL to PDAC in SL/PDAC self-assembled films. During SL/PDAC self-assembly, hydrophobic interaction plays an important role in determining the adsorption rate, film thickness, surface morphology, and surface properties. SL with a higher M(w) has a stronger hydrophobic ability in water, so it exhibits a slower adsorption rate, a larger film thickness, and a higher film roughness. SL with different M(w) has almost the same wettability because of a larger hydrophobic effect that increases contact angle and a higher film roughness that decreases contact angle. In this case, the opposite effects cancel each other to make no difference in wettability, but it still reflects the role of the hydrophobic effect in surface properties.

Five sodium lignosulfonate (SL) fractions with narrow molecular weight distribution and known salt content were used as the polyanion to build up layer-by-layer self-assembly multilayers with poly(diallyldimethylammonium chloride) (PDAC) as polycation. It is interesting to find that the salt-free SL is hardly adsorbed on the PDAC surface, but the SL in salt-added solutions can be self-assembled well with PDAC to form SL/PDAC multilayers. When the five SL fractions dissolved in saline solutions are adsorbed on the PDAC surface by a self-assembly technique, SL with higher M(w) shows a higher adsorption amount than does SL with lower M(w). The driving forces of self-assembly of SL and PDAC are discussed based on the solution behaviors and adsorption characteristics of SL in salt-free and salt-added aqueous solutions. A possible self-assembled mechanism of SL and PDAC is electrostatic or cation-π interactions, but the SL cannot be adsorbed onto the PDAC surface without a hydrophobic interaction. With the addition of enough salt, the Coulomb interaction of SL becomes negligible, but the adsorption amount increases, indicating that the electrostatic interaction is not the main driving force of SL/PDAC self-assembly. For adsorption of SL in saline solution onto the PDAC surface, the cation-π interaction is the main driving force, and the hydrophobic interaction plays an important role in the adsorbed amount.

Molecular iodine has been introduced into the alkali lignin (AL) solutions to adjust the π-π aggregation, and the effect of lignin-iodine complexes on the aggregation and assembly characteristics of AL have been investigated by using fluorescence, UV-vis spectroscopy, light scattering, and viscometric techniques. Results show that AL form π-π aggregates (i.e., J-aggregates) in THF driven by the π-π interaction of the aromatic groups in AL, and the π-π aggregates undergo disaggregation in THF-I(2) media because of the formation of lignin-iodine charge-transfer complexes. By using iodine as a probe to investigate the aggregation behaviors and assembly characteristics, it is estimated that about 18 mol % aromatic groups of AL form π-π aggregates in AL molecular aggregates. When molecular iodine is introduced into the AL solutions, lignin-iodine complexes occur with charge-transfer transition from HOMO of the aromatic groups of AL to the LUMO of iodine. The formation of lignin-iodine complexes reduces the affinity of the aromatic groups approaching each other due to the electrostatic repulsion and then eliminates the π-π interaction of the aromatic groups. The disaggregation of the π-π aggregates brings a dissociation behavior of AL chains and a pronounced molecular expansion. This dissociation behavior and molecular expansion of AL in the dipping solutions induce a decrease in the adsorbed amount and an increase in the adsorption rate, when AL is transferred from the dipping solution to the self-assembled adsorbed films. Consequently, the adsorption behavior of AL can be controlled by adjusting the π-π aggregation. Above observations give insight into the occurrence of J-aggregation of the aromatic groups in the AL molecular aggregates and the disaggregation mechanism of AL aggregates induced by the lignin-iodine complexes for the first time. The understanding can provide an academic instruction in the efficient utilization of the alkali lignin from the waste liquor and also leads to further development in expanding functionalities of the aromatic compounds through manipulation of the π-π aggregation.

In this work, azobenzene-containing colloidal spheres have been fabricated and used to construct photoresponsive monolayers. The colloidal spheres were prepared from an amphiphilic azobenzene-containing random copolymer through hydrophobic aggregation of the polymer chains, which was induced by adding the selective solvent (H2O) into a THF solution of the polymer. The size and size distribution of the spheres depended on the initial concentration of the azo polymer in THF and the H2O/THF ratio. Adjusting those factors and optimizing other preparation conditions, uniform colloidal spheres could be obtained. Monolayers composed of hexagonally close-packed colloidal spheres were prepared by the capillary-force-driven method. The colloidal monolayers showed obvious dichroism after laser irradiation due to the photoinduced azo-chromophore orientation occurred in the spheres. The orientation order parameter was related to the irradiation time and estimated to be 0.09 at the photostationary state. The colloidal spheres and their monolayers can potentially be used as building blocks or media for reversible optical data storage, photo-switching, sensors, and other photo-driven devices.