Revisiting the Role of Conductivity and Polarity of Host Materials for Long‐Life Lithium–Sulfur Battery

Despite their high theoretical energy density and low cost, lithium–sulfur batteries (LSBs) suffer from poor cycle life and low energy efficiency owing to the polysulfides shuttle and the electronic insulating nature of sulfur. Conductivity and polarity are two critical parameters for the search of optimal sulfur host materials. However, their role in immobilizing polysulfides and enhancing redox kinetics for long‐life LSBs are not fully understood. This work has conducted an evaluation on the role of polarity over conductivity by using a polar but nonconductive platelet ordered mesoporous silica (pOMS) and its replica platelet ordered mesoporous carbon (pOMC), which is conductive but nonpolar. It is found that the polar pOMS/S cathode with a sulfur mass fraction of 80 wt% demonstrates outstanding long‐term cycle stability for 2000 cycles even at a high current density of 2C. Furthermore, the pOMS/S cathode with a high sulfur loading of 6.5 mg cm^?2 illustrates high areal and volumetric capacities with high capacity retention. Complementary physical and electrochemical probes clearly show that surface polarity and structure are more dominant factors for sulfur utilization efficiency and long‐life, while the conductivity can be compensated by the conductive agent involved as a required electrode material during electrode preparation. The present findings shed new light on the design principles of sulfur hosts towards long‐life and highly efficient LSBs.     

Analysis of Intracellular Nucleotides by Capillary Electrophoresis–Mass Spectrometry

A pilot study using capillary electrophoresis with mass spectrometry for the analysis of nucleotides in human erythrocytes is presented. Erythrocytes were incubated with 5-amino-4-imidazolecarboxamide riboside in order to mimic situation in defect of purine metabolism—AICA-ribosiduria. Characteristic AICA-ribotides together with normal nucleotides were separated by capillary electrophoresis in acetate buffer (20 mmol/L, pH 4.4) and identified on line by mass spectrometry.     

Understanding the pH-dependent immobilization efficacy of feruloyl esterase-C on mesoporous silica and its structure–activity changes

The purpose of the present investigation was to study the pH dependence of both the immobilization process and the enzyme activity of a feruloyl esterase (FoFaeC from Fusarium oxysporum) immobilized in mesoporous silica. This was done by interpreting experimental results with theoretical molecular modeling of the enzyme structure. Modeling of the 3D structure of the enzyme together with calculations of the electrostatic surface potential showed that changes in the electrostatic potential of the protein surface were correlated with the pH dependence of the immobilization process. High immobilization yields were associated with an increase in pH. The transesterification activity of both immobilized and free enzyme was studied at different values of pH and the optimal pH of the immobilized enzyme was found to be one unit lower than that for the free enzyme. The surface charge distribution around the binding pocket was identified as being a crucial factor for the accessibility of the active site of the immobilized enzyme, indicating that the orientation of the enzyme inside the pores is pH dependent. Interestingly, it was observed that the immobilization pH affects the specific activity, irrespective of the changes in reaction pH. This was identified as a pH memory effect for the immobilized enzyme. On the other hand, a change in product selectivity of the immobilized enzyme was also observed when the transesterification reaction was run in MOPS buffer instead of citrate phosphate buffer. Molecular docking studies revealed that the MOPS buffer molecule can bind to the enzyme binding pocket, and can therefore be assumed to modulate the product selectivity of the immobilized enzyme toward transesterification.     

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials'' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber''s methods, which have smooth surfaces.     

Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High‐Performance All‐Vanadium Redox Flow Battery Membrane

A novel low‐cost nanoporous polytetrafluoroethylene (PTFE)/silica composite separator has been prepared and evaluated for its use in an all‐vanadium redox flow battery (VRB). The separator consists of silica particles enmeshed in a PTFE fibril matrix. It possesses unique nanoporous structures with an average pore size of 38 nm and a porosity of 48%. These pores function as the ion transport channels during redox flow battery operation. This separator provides excellent electrochemical performance in the mixed‐acid VRB system. The VRB using this separator delivers impressive energy efficiency, rate capability, and temperature tolerance. In additon, the flow cell using the novel separator also demonstrates an exceptional capacity retention capability over extended cycling, thus offering excellent stability for long‐term operation. The characteristics of low cost, excellent electrochemical performance and proven chemical stability afford the PTFE/silica nanoporous separator great potential as a substitute for the Nafion membrane used in VRB applications.     

Amino‐functionalized macroporous silica for efficient tryptic digestion in acidic solutions

Amino‐functionalized macroporous silica foam (NH₂‐MOSF) has been developed as a host reactor to realize highly efficient proteolysis in acidic solutions where normal tryptic reactions cannot occur. The digestion protocol consists simply of adding the functionalized NH₂‐MOSF into the protein and trypsin solutions without altering the bulk pH or preloading the enzymes on the materials. With this protocol, digestion of sample fractions from LC can be efficiently realized in the acidic solutions directly. Digestion of a protein fraction extracted from rat liver tissue after LC separation was performed to illustrate this principle, where 103 proteins were successfully identified at pH 3 after 1.5 h of tryptic digestion.     

Immobilization rapidly selects for chemoresistant ovarian cancer cells with enhanced ability to enter dormancy

Around 20–30% of ovarian cancer patients exhibit chemoresistance, but there are currently no methods to predict whether a patient will respond to chemotherapy. Here, we discovered that chemoresistant ovarian cancer cells exhibit enhanced survival in a quiescent state upon experiencing the stress of physical confinement. When immobilized in stiff silica gels, most ovarian cancer cells die within days, but surviving cells exhibit hallmarks of single-cell dormancy. Upon extraction from gels, the cells resume proliferation but demonstrate enhanced viability upon reimmobilization, indicating that initial immobilization selects for cells with a higher propensity to enter dormancy. RNA-seq analysis of the extracted cells shows they have signaling responses similar to cells surviving cisplatin treatment, and in comparison to chemoresistant patient cohorts, they share differentially expressed genes that are associated with platinum-resistance pathways. Furthermore, these extracted cells demonstrate greater resistance to cisplatin and paclitaxel, despite being proliferative. In contrast, serum starvation and hypoxia could not effectively select for chemoresistant cells upon removal of the environmental stress. These findings demonstrate that ovarian cancer chemoresistance and the ability to enter dormancy are linked, and immobilization rapidly distinguishes chemoresistant cells. This platform could be suitable for mechanistic studies, drug development, or as a clinical diagnostic tool.     

Hydrogen bond analysis of confined water in mesoporous silica using the reactive force field

ABSTRACT

The structural and dynamical properties of water confined in nanoporous silica with a pore diameter of 2.7?nm were investigated by performing large-scale molecular dynamics simulations using the reactive force field. The radial distribution function and diffusion coefficient of water were calculated, and the values at the centre of the pore agreed well with experimental values for real water. In addition, the pore was divided into thin coaxial layers, and the average number of hydrogen bonds, hydrogen bond lifetime and hydrogen bond strength were calculated as a function of the radial distance from the pore central axis. The analysis showed that hydrogen bonds involving silanol (Si–OH) have a longer lifetime, although the average number of hydrogen bonds per atom does not change from that at the pore centre. The longer lifetime, as well as smaller diffusion coefficient, of these hydrogen bonds is attributed to their greater strength.     

Multiscale simulation of flow-induced texture formation in polymer liquid crystals and carbonaceous mesophases

This paper presents theory and simulation of flow-induced structures in liquid crystalline materials, useful to the creation of synthetic material structures and to the biomimetics of natural fibers. A multiscale theory and simulation of hydrodynamic texture formation is presented; it provides fundamental principles for control and optimization of structures in liquid crystal polymers and carbonaceous mesophases. In thermotropic flow-aligning nematic polymers it is found that as the shear-rate increases, the pathway between an oriented non-planar state and an oriented planar state is through meso-texture formation and coarsening, with temperature and shear rate being efficient fields to control the grain size of the texture. For capillary flow of carbonaceous mesophases, the simulations predict the emergence of macroscopic ring patterns whose thickness and density can be controlled by the applied pressure drops. The results provide insight on microstructure formation and control in liquid crystalline materials.     

Effect of thiol-functionalised silica on cisplatin adsorption

This study contributes to the investigation related to guest–host interactions between the chemotherapeutic agent cisplatin and a functionalised silica matrix in order to improve and find new materials such as drug carriers. The adsorption of cisplatin and its complexes, cis-[PtCl(NH₃)₂]⁺ and cis-[Pt(NH₃)₂]²⁺, on a SH-functionalised SiO₂(111) surface has been studied by the atom superposition and electron delocalisation method. The adiabatic energy curves for the adsorption of the drug and its products on the delivery system were considered. The electronic structure and bonding analysis were also performed. The molecule and their complex are adsorbed on the functionalised surface resulting in a major absorption of the cis-[Pt(NH₃)₂]²⁺ complex. The molecule–surface interactions are formed via –SH group. The molecule/complexes SH electron-donating effect plays an important role in the catalytic reaction. The more important drug–carrier interactions occur through the Cl–H bond for the adsorption of cis-[PtCl₂(NH₃)₂] and cis-[PtCl(NH₃)₂]⁺, and through the Pt–S and Pt–H interactions for cis-[Pt(NH₃)₂]²⁺ adsorption. When the new interactions are formed, the functionalised carrier maintains their matrix properties while the molecule is the most affected after adsorption. The Pt atomic orbitals present the most important changes during adsorption.