Preparation of PANI/CuPc/PDMS Composite Elastomer with High Dielectric Constant and Low Modulus Assisted by Electric Fields.

Dielectric elastomer is a kind of electronic electroactive polymer, which plays an important role in the application of soft robots and flexible electronics. In this study, an all-organic polyaniline/copper phthalocyanine/silicone rubber (PANI/CuPc/PDMS) dielectric composite with superior comprehensive properties was prepared by manipulating the arrangement of filler in a polymer matrix assisted by electric fields. Both CuPc particles and PANI particles can form network structures in the PDMS matrix by self-assembly under electric fields, which can enhance the dielectric properties of the composites at low filler content. The dielectric constant of the assembled PANI/CuPc/PDMS composites can reach up to 140 at 100 Hz when the content of CuPc and PANI particles is 4 wt% and 2.5 wt%, respectively. Moreover, the elastic modulus of the composites remains below 2 MPa, which is important for electro-deforming. The strain of assembled PANI/CuPc/PDMS three-phase composites at low electric field strength (2 kV/mm) can increase up to five times the composites with randomly dispersed particles, which makes this composite have potential application in the field of soft robots and flexible electronics.

Dry-Processable Polymer Electrolytes for Solid Manufactured Batteries.

Designing a solid-state electrolyte that satisfies the operating requirements of solid-state batteries is key to solid-state battery applications. The consensus is that solid-state electrolytes need to allow fast ion transport, while providing better interfacial compatibility and mechanical tolerance. Herein, a simple but effective strategy is proposed, combining hard and soft component polymer systems, to exploit a solid polymer electrolyte (SPE) with a 3D network via an in situ graft polymerization. The 3D structure is constructed by a hard cellulose nanocrystal (CNC) as the skeleton and a soft polyacrylonitrile (PAN) as the filler through a dry-processing method. The reported systems have several advantages, including ease of processing, only requiring using an exceedingly small amount of solvent, light weight (ρ = 1.2 g cm-3), excellent mechanical stability (tensile strength of 9.5 MPa), and high ionic conductivity (3.9 × 10-4 S cm-1, 18 °C) and migration number (tLi+ = 0.8). In particular, the high conductivity is enabled: the efficient Li+ transportation path constructed between CNC-PAN powders and abundant sulfonate radicals and hydroxyl groups on the CNC surface acts as the bridge of Li+ transition. When the CNCs are grafted onto the PAN polymer, the dipole-dipole interaction between the nitrile groups of the PAN and the hydroxyl groups of the CNCs can help to improve the mechanical stability and ionic conductivity of the SPE. Moreover, a tightly formed interface between SPE and LiFePO4 (LFP)/carbon black/SPE cathode can be achieved in an assembled solid-state battery by hot pressing, thus further enhancing the battery's performance.

Implication of Freeze-Thaw Erosion and Mechanism Analysis of High-Performance Aromatic Liquid Crystal Fibers.

According to the demand for high-performance fibers for high-latitude ocean exploration and development, this paper selects representative products of high-performance liquid crystal fibers: thermotropic liquid crystal polymer fibers (TLCP) and poly p-phenylene terephthalamide (PPTA) fibers. Through a series of freeze-thaw (F-T) experiments for simulating a real, cold marine environment, we then measure the retention of mechanical properties of these two kinds of fibers. Before that, due to the difference in their chemical structures, we tested their Yang-Laplace contact angle (YLCA) and water absorption; the results suggested that PPTA fibers would absorb more moisture. Surprisingly, then, compared with thermotropic liquid crystal polymer (TLCP) fibers, the retention of the mechanical properties of poly p-phenylene terephthalamide (PPTA) fibers decreased by around 25% after the F-T experiments. The Fourier-transformed infrared (FT-IR) analysis, the attenuated total reflection (ATR) accessory analysis and the degree of crystal orientation measured by two-dimensional wide-angle X-ray diffraction (2D-WAXD) confirm that no changes in the chemical and the orientation structure of the crystal region of the fibers occurred after they underwent the F-T cycles. However, as observed by scanning electron microscopy (SEM), there are microcracks of various extents on the surface of the PPTA fibers, but they do not appear on the surface of TLCP fibers. It is obvious that these microcracks will lead to the loss of mechanical properties; we infer that the moisture absorbed by the PPTA fibers freezes below the freezing point, and the volume expansion of the ice causes the collapse of the microfibrillar structure. The two sorts of fibers subjected to the F-T experiments are immersed in a sodium chloride solution, and the amount of water infiltrated into the PPTA microfibrillar structure is evaluated according to the content of sodium ions in the fiber surface and subsurface layers through X-ray spectroscopy (EDS) elemental analysis. From the above analysis, we found that TLCP fibers can more effectively meet the operating standards of the severe and cold marine environment.

Ocular adverse events associated with BRAF and MEK inhibitor combination therapy: a pharmacovigilance disproportionality analysis of the FDA adverse event reporting system.

BACKGROUND: BRAF and MEK inhibitor combination therapy have significantly improved the outcome of several BRAF-mutation tumors, but it also confers the risk of drug-induced ocular adverse events (oAEs). However, very few studies focused on this risk. METHODS: The United States Food and Drug Administration Adverse Event Reporting System (FAERS) data from Quarter 1-2011 to Quarter 2-2022 were searched to detect signs of oAEs of three marketed BRAF and MEK inhibitor combination therapies: vemurafenib plus cobimetinib (V + C), dabrafenib plus trametinib (D + T), and encorafenib plus binimetinib (E + B). Disproportionality analyses were performed by calculating the proportional reporting ratio (PRR), χ2 (chi-square), and reporting odds ratios (RORs) with a 95% confidence interval (CI). RESULTS: A series of oAEs were identified, including 42 preferred terms, which could be classified into 8 aspects. In addition to previously reported oAEs, several unexpected oAE signals were detected. Moreover, differences in oAE profiles were found among three combination therapies (V + C, D + T, and E + B). CONCLUSIONS: Our findings support an association between several oAEs and BRAF and MEK inhibitor combination therapies, including several new oAEs. In addition, oAEs profiles may vary across the treatment regimens. Further studies are needed to better quantify these oAEs.

Combination of High pH and an Antioxidant Improves Chemical Stability of Two-Dimensional Transition-Metal Carbides and Carbonitrides (MXenes) in Aqueous Colloidal Solutions.

MXenes, a large family of two-dimensional (2D) transition-metal carbides/nitrides, have attracted increased attention in recent years because of their excellent electronic, mechanical, thermal, and optical properties. Studying chemical properties of MXenes is important to prolong the shelf life of their colloids and provide robust performance of MXenes in devices and applications. While the role of MXene reactivity with the environment, including water and components of air, is becoming more recognized, less is known about the role of parameters influencing the reactivity. In this work, we investigate the individual and combined effects of the pH and antioxidant on chemical stability of Ti2CTx, Ti3CNTx, and Ti3C2Tx MXenes using GC, XPS, UV-vis, and Raman spectroscopy. In contrast to indirect indicators of MXene degradation, such as film conductivity or performance in electrochemical energy storage systems, we focus on detection of reaction products as the most sensitive and direct way of monitoring the chemical transformations of MXenes. Based on our knowledge of MXene chemistry and interactions with the environment, we propose a combination of sodium hydroxide and sodium l-ascorbate to effectively slow down degradation of MXenes in colloidal solutions by suppressing their hydrolysis and oxidation reactions, respectively.

Conductive graphene coated carboxymethyl cellulose hybrid fibers with polymeric ionic liquids as intermediate.

In this study, a kind of polymeric ionic liquid (PIL) called PIL-Cl was synthesized and modified to obtain conductive graphene coated carboxymethyl cellulose hybrid fibers. Carboxymethyl cellulose (CMC) was formed into fibers by wet spinning assisted with PILCl. Co-precipitation test of CMC and PIL-Cl demonstrated that PIL-Cl could precipitate with CMC through strong electrostatic interaction and molar ratio of CMC and PIL-Cl (calculated in repeating units) would affect the formation of precipitation. Secondly, modified PIL-Cl named PIL-Ac was used as an intermediate connecting CMC fiber and graphene to fabricate conductive CMC/PIL/graphene fibers. A series of tests were performed on CMC/PIL/graphene fibers, including Raman spectroscopy, scanning electron microscopy and conductivity test. The results showed that PIL-Cl could help form CMC fiber, and PIL-Ac could functionalize it and make it conductive.

Adhesion Between MXenes and Other 2D Materials.

MXenes, a large family of two-dimensional (2D) early transition metal carbides and nitrides, have excellent electrical and electrochemical properties, which can also be explored in assemblies with other 2D materials, like graphene and transition metal dichalcogenides (TMDs), creating heterostructures with unique properties. Understanding the interaction mechanism between 2D materials is critical for the design and manipulation of these 2D heterostructures. Our previous work investigated the interaction between SiO2 and two MXenes (Ti3C2Tx and Ti2CTx). However, no experimental research has been done on MXene interlayer interactions and interactions in MXene heterostructures. Here, we used atomic force microscopy (AFM) with SiO2 tip and Ti3C2Tx and Ti2CTx MXene-coated tips, respectively, to measure the adhesion energies of graphene, MoSe2, Ti3C2Tx, and Ti2CTx MXene with other 2D materials. The measured adhesion energies show that only the interfaces involving graphene demonstrate dependence on the number of material monolayers in a stack. Comparing 40 interacting pairs of 2D materials, the lowest adhesion energy (∼0.27 J/m2) was found for the interfaces involving MoSe2 and the highest adhesion energy was observed for the interfaces involving Ti3C2Tx (∼1.23 J/m2). The obtained set of experimental data for 2D interfaces involving MXenes provides a basis for a future in-depth understanding of adhesive mechanisms at interfaces between 2D materials, which is an important topic for the design of 2D heterostructures with controlled interfacial strength and properties.

Hard template synthesis of 2D porous Co3O4 nanosheets with graphene oxide for H2O2 sensing.

In this work, we used graphene oxide (GO) as a template that was removed by calcination to finally successfully prepare Co3O4 with 2D porous nanostructure. The results show that 2D porous structure Co3O4 nanosheets were only prepared at pH = 2. After electrochemical tests, the as-prepared Co3O4 nanosheets showed electrochemical properties that are highly suitable for H2O2 detection, such as high current response, short response time (less than 3 s), wide linear range (0.388-44.156 mM), low limit of detection (2.33 µM) and high sensitivity (0.0891 mA mM-1 cm-2). These excellent properties are mainly due to GO, as a 2D template, which connects Co3O4 nanoparticles to each other on a 2D plane, preventing the agglomeration of Co3O4 nanoparticles. The abundant pores between Co3O4 nanoparticles can greatly increase the reaction between the nanoparticles and H2O2 molecules.

Electrochemical Measurement of Cholesterol Flip-Flop in Plasma Membrane at Single Cells.

Here, a microelectrode approach is established to measure the flip-flop rate of cholesterol in plasma membranes at single living cells. The initial validation is performed in a modeled phospholipid bilayer positioned at an interconnecting hole between two compartments, in which cholesterol in one compartment diffuses into the other one through a flip-flop movement in the bilayer and is then detected by a cholesterol oxidase-modified microelectrode. As compared with the time (140 ± 28 s) for free cholesterol transport in absence of the bilayer, a prolonged time (702 ± 42 s) is needed to observe the current increase in the presence of the bilayer. The difference in the time (562 s) gives the estimated flip-flop time of cholesterol in the bilayer. The position of the microelectrode in contact with a living cell and the injection of cholesterol inside the cell are further applied to measure the cholesterol flip-flop in the plasma membrane. The average time (1183 ± 146 s) is obtained to observe an additional current increase at the microelectrode, which reflects the cholesterol flip-flop rate in plasma membranes in single living cells. All these results support the establishment of this microelectrode approach for the study of the cholesterol flip-flop process in lipid membranes.

Understanding Chemistry of Two-Dimensional Transition Metal Carbides and Carbonitrides (MXenes) with Gas Analysis.

MXenes, a large family of two-dimensional materials that are intensely investigated for a broad range of applications, are unstable in water, spontaneously forming TiO2. Several hypotheses have been proposed recently to explain the transformations of MXenes in aqueous environments based on characterization of solid products and measurements of solution pH. However, no studies of the gaseous products of these reactions have been reported. In this work, we demonstrate the use of Raman spectroscopy and gas chromatography techniques to study the gaseous reaction products of Ti2C, Ti3C2, Ti3CN, and Nb2C MXenes in aqueous environments. Based on the analysis of gases, the reactivities of MXenes with different monolayer thickness and chemical composition have been analyzed. We demonstrate the analysis of gases produced during MXene transformations as a powerful technique that can be used for better understanding of their nontrivial chemistry.

Dynamical Control over Terahertz Electromagnetic Interference Shielding with 2D Ti3C2Ty MXene by Ultrafast Optical Pulses.

High electrical conductivity and strong absorption of electromagnetic radiation in the terahertz (THz) frequency range by metallic 2D MXene Ti3C2Ty make it a promising material for electromagnetic interference shielding, THz detectors, and transparent conducting electrodes. Here, we demonstrate that ultrafast optical pulses with wavelengths straddling the visible range (400 and 800 nm) induce transient broad-band THz transparency in the MXene that persists for nanoseconds. We demonstrate that optically induced transient THz transparency is independent of temperature from 95 to 290 K. This discovery opens new possibilities for development of switchable electromagnetic interference shielding materials and devices that can be rendered partially transparent on demand for transmitting THz signals, or for designing new THz devices such as sensitive optically gated detectors.

Adhesion of two-dimensional titanium carbides (MXenes) and graphene to silicon.

Two-dimensional transition metal carbides (MXenes) have attracted a great interest of the research community as a relatively recently discovered large class of materials with unique electronic and optical properties. Understanding of adhesion between MXenes and various substrates is critically important for MXene device fabrication and performance. We report results of direct atomic force microscopy (AFM) measurements of adhesion of two MXenes (Ti3C2Tx and Ti2CTx) with a SiO2 coated Si spherical tip. The Maugis-Dugdale theory was applied to convert the AFM measured adhesion force to adhesion energy, while taking into account surface roughness. The obtained adhesion energies were compared with those for mono-, bi-, and tri-layer graphene, as well as SiO2 substrates. The average adhesion energies for the MXenes are 0.90 ± 0.03 J m-2 and 0.40 ± 0.02 J m-2 for thicker Ti3C2Tx and thinner Ti2CTx, respectively, which is of the same order of magnitude as that between graphene and silica tip.

Hydrolysis of 2D Transition-Metal Carbides (MXenes) in Colloidal Solutions.

Although oxidation was deemed as the main factor responsible for the instability of MXenes in aqueous colloids, here we put forward and test a hypothesis about the central role of water as the primary factor. We show that water and related processes of MXene hydrolysis play the main role in the phenomena leading to complete transformations of 2D titanium carbide MXenes into titania in aqueous environments. To demonstrate the role of water, the stability of two MXenes, Ti3C2T x and Ti2CT x, has been systematically studied in aqueous and nonaqueous colloids exposed to oxygen and inert gas atmospheres. The calculated time constant for degradation of Ti3C2T x dispersed in anhydrous iso-propanol saturated with pure oxygen exceeds 5 years, in striking contrast to the same MXene dispersed in water, where more than a half of it would transform into titania even in an oxygen-less atmosphere over ∼41 days. A thinner Ti2CT x MXene showed similar behavior, albeit with shorter time constants in both solvents, correspondingly. UV-vis and Raman spectroscopy were used to analyze the oxidation kinetics and composition of fresh and aged MXenes. An intense anatase peak was observed in MXenes stored in aqueous solutions under Ar atmosphere, while no signs of oxidation could be found in iso-propanol solutions of the MXenes stored under O2 atmosphere over a similar period of time.

Codetermination of Sphingomyelin and Cholesterol in Cellular Plasma Membrane in Sphingomyelin-Depletion-Induced Cholesterol Efflux.

Quantification of multiple lipids with different contents in plasma membrane in single cells is significant, but challenging, for investigating lipid interactions and the role of dominant protein transporters. In this paper, comonitoring the alteration of low-content sphingomyelin (SM) and high-content cholesterol in plasma membrane of one living cell is realized by use of luminol electrochemiluminescence (ECL) for the first time. Concentrations of SM as low as 0.5 µM are detected, which permits the measurement of low-content membrane SM in single cells. More membrane cholesterol is observed in individual cells after depletion of membrane SM, providing direct evidence about SM-depletion-induced cholesterol efflux. The upregulation of ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1) in SM-depleted cells induces a further increase in membrane cholesterol. These results imply that higher expression of ABCA1/G1 promotes cholesterol trafficking, which offers additional information to solve the debate about ABC transporters in cholesterol efflux. Moreover, the established approach offers a special strategy to investigate the correlation of membrane lipids and the role of transporters in cholesterol trafficking.

Surface functionalization of cellulose nanocrystals with polymeric ionic liquids during phase transfer.

In this study, the cellulose nanocrystals (CNCs) were prepared by method of acid hydrolysis, while the polymeric ionic liquid (PIL) [PEP-MIM]DBS was synthesized by epichlorohydrin, o-phthalic anhydride as well as N-methylimidazole then anion exchanged by sodium dodecyl benzene sulfonate. It was demonstrated that [PEP-MIM]DBS could modify CNCs by non-covalent interaction to change its surface properties, such as amphiphilicity. The chemical structure of the composite CNCs/[PEP-MIM]DBS was characterized via FTIR, 13C NMR, TGA, XRD, etc. Moreover, the properties and applications were characterized through a series of dispersion experiments, contact angle tests, FE-SEM, etc. This study showed that the PIL-modification improved the dispersion of CNCs in non-polar organic solvents with their chemical structure integrated.

The Putative Protein Phosphatase MoYvh1 Functions Upstream of MoPdeH to Regulate the Development and Pathogenicity in Magnaporthe oryzae.

Protein phosphatases are critical regulators in eukaryotic cells. For example, the budding yeast Saccharomyces cerevisiae dual specificity protein phosphatase (DSP) ScYvh1 regulates growth, sporulation, and glycogen accumulation. Despite such importance, functions of Yvh1 proteins in filamentous fungi are not well understood. In this study, we characterized putative protein phosphatase MoYvh1, an Yvh1 homolog in the rice blast fungus Magnaporthe oryzae. Deletion of the MoYVH1 gene resulted in significant reductions in vegetative growth, conidial production, and virulence. The ΔMoyvh1 mutant also displayed defects in cell-wall integrity and was hyposensitive to the exogenous osmotic stress. Further examination revealed that the ΔMoyvh1 mutant had defects in appressorium function and invasive hyphae growth, resulting attenuated pathogenicity. Interestingly, we found that MoYvh1 affects the scavenging of host-derived reactive oxygen species that promotes M. oryzae infection. Finally, overexpression of the phosphodiesterase MoPDEH suppressed the defects in conidia formation and pathogenicity of the ΔMoyvh1 mutant, suggesting MoYvh1 could regulate MoPDEH for its function. Our study reveals not only the importance of MoYvh1 proteins in growth, differentiation, and virulence of the rice blast fungus but, also, a genetic link between MoYvh1 and MoPDEH-cAMP signaling in this fungus.