Attempts at depositing uniform films of nanoparticles by drop-drying have been frustrated by the "coffee-stain" effect due to convective macroscopic flow into the contact line. Here, we show that uniform deposition of nanoparticles in aqueous suspensions can be attained easily by drying the droplet in an ethanol vapor atmosphere. This technique allows the particle-laden water droplets to spread on a variety of surfaces such as glass, silicon, mica, PDMS, and even Teflon. Visualization of droplet shape and internal flow shows initial droplet spreading and strong recirculating flow during spreading and shrinkage. The initial spreading is due to a diminishing contact angle from the absorption of ethanol from the vapor at the contact line. During the drying phase, the vapor is saturated in ethanol, leading to preferential evaporation of water at the contact line. This generates a surface tension gradient that drives a strong recirculating flow and homogenizes the nanoparticle concentration. We show that this method can be used for depositing catalyst nanoparticles for the growth of single-walled carbon nanotubes as well as to manufacture plasmonic films of well-spaced, unaggregated gold nanoparticles.

We demonstrate continuous roll-to-roll production of highly conductive silver network films on a plastic substrate via mechanical and chemical welding processes. This process included three essential steps: (i) solvent spraying, (ii) roll compression, and (iii) salt treatment and washing. The sheet resistance of the resulting AgNW film was 5 Ω sq(-1) at 92% transmittance, which was the lowest sheet resistance and the highest transparency among the values reported previously for solution-processed AgNW electrodes. Moreover, the strong contacts among the AgNWs dramatically enhanced the mechanical stability of the network film. The resulting AgNW film was successfully applied to various organic electronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), and organic solar cells (OSCs).

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

Using the first-principles calculations, we explored the feasibility of using graphdiyne, a 2D layer of sp and sp2 hybrid carbon networks, as lithium ion battery anodes. We found that the composite of the Li-intercalated multilayer α-graphdiyne was C6Li7.31 and that the calculated voltage was suitable for the anode. The practical specific/volumetric capacities can reach up to 2719 mAh g−1/2032 mAh cm−3, much greater than the values of ∼372 mAh g−1/∼818 mAh cm−3, ∼1117 mAh g−1/∼1589 mAh cm−3, and ∼744 mAh g−1 for graphite, graphynes, and γ-graphdiyne, respectively. Our calculations suggest that multilayer α-graphdiyne can serve as a promising high-capacity lithium ion battery anode.

Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

Abstract. "Margination" refers to the movement of particles in flow toward the walls of a channel. The term was first coined in physiology for describing the behavior of white blood cells (WBCs) and platelets in blood flow. The margination of particles is desirable for anticancer drug delivery because it results in the close proximity of drug-carrying particles to the endothelium, where they can easily diffuse into cancerous tumors through the leaky vasculature. Understanding the fundamentals of margination may further lead to the rational design of particles and allow for more specific delivery of anticancer drugs into tumors, thereby increasing patient comfort during cancer treatment. This paper reviews existing theoretical and experimental studies that focus on understanding margination. Margination is a complex phenomenon that depends on the interplay between inertial, hydrodynamic, electrostatic, lift, van der Waals, and Brownian forces. Parameters that have been explored thus far include the particle size, shape, density, stiffness, shear rate, and the concentration and aggregation state of red blood cells (RBCs). Many studies suggested that there exists an optimal particle size for margination to occur, and that nonspherical particles tend to marginate better than spherical particles. There are, however, conflicting views on the effects of particle density, stiffness, shear rate, and RBCs. The limitations of using the adhesion of particles to the channel walls in order to quantify margination propensity are explained, and some outstanding questions for future research are highlighted.

Cloned soybean sterol methyltransferase was purified from Escherichia coli to gel electrophoretic homogeneity. From initial velocity experiments, catalytic constants for substrates best suited for the first and second C 1 transfer activities, cycloartenol and 24(28)-methylenelophenol, were 0.01 and 0.001 s ؊1 , respectively. Two-substrate kinetic analysis using cycloartenol and S-adenosyl-L-methionine (AdoMet) generated an intersecting line pattern characteristic of a ternary complex kinetic mechanism. H 3 ]AdoMet to examine the kinetic isotope effects attending the C-28 deprotonation in the enzymatic synthesis of 24-ethyl(idene) sterols. The stereochemical features as well as the observation of isotopically sensitive branching during the second C-methylation suggests that the two methylation steps can proceed by a change in chemical mechanism resulting from differences in sterol structure, concerted versus carbocation; the kinetic mechanism remains the same during the consecutive methylation of the ⌬ 24 bond.Sterol methyltransferases (SMTs) 1 are ubiquitously represented in plants and fungi (1). Together, these enzymes generate 24-alkyl sterol diversity, which includes formation of singly and doubly C-24-alkylated sterol side chains and olefin variants possessing ⌬ 24(28) , ⌬ 23 (24) , and ⌬ 25(27) side chains (2). In most organisms, SMTs catalyze the first committed step in the biosynthesis of phytosterols (3, 4) (Fig. 1). The crucial role of these enzymes to generate an essential physiological group in sterol structure has stimulated considerable interest in the stereochemistry and mechanism of the C-methylation reaction (5, 6). Several SMTs have been characterized at the molecular level, and their amino acid compositions reveal a highly conserved signature motif that represents the sterol-binding site (7,8). A number of these enzymes have been characterized, and they share similar native molecular masses in the range of 160 -175 kDa and similar properties (1). The methyl transfer reaction catalyzed by SMT is proposed to proceed through a nucleophilic attack by the electrons of the ⌬ 24 double bond on the S-methyl group of AdoMet (9 -11). The reaction can lead to the formation of a high energy intermediate (HEI) possessing a methyl at C-24 and a carbonium ion at C-25. After a hydride transfer from C-24 to C-25, an elimination of a proton at C-28 occurs, giving a 24(28)-methylene sterol. The steric course of the reaction has been hypothesized to proceed by an "X-group" (covalent), carbocation, or concerted mechanism (Scheme 1) (8).As recognized in the steric-electric plug model and X-group mechanism, the conformation of the bound sterol side chain can influence the configuration of the enzyme-generated product at C-24 and C-25 (Scheme 1A) (8).Recent work on the stereochemistry of phytosterol (24-alkyl sterols) side chain carbon atoms harboring chemically or biosynthetically introduced 13 C label showed that the natural configuration for C-26 and C-27 of ergosterol and sitosterol (C-25 S; 2) is opposite to that...

A new model for mechanically induced red blood cell damage is presented. Incorporating biophysical insight at multiple length scales, the model couples flow-induced deformation of the cell membrane (similar to 10 mu m) to membrane permeabilization and hemoglobin transport (similar to 100 nm). We estimate hemolysis in macroscopic (above similar to 1 mm) 2-D inhomogeneous blood flow by computational fluid dynamics (CFD) and compare results with literature models. Simulations predict the effects of local flow field on RBC damage, due to the combined contribution of membrane permeabilization and hemoglobin transport. The multiscale approach developed here lays a foundation for a predictive tool for the optimization of hydrodynamic and hematologic design of cardiovascular prostheses and blood purification devices. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 1509-1516, 201