Solution-Blown Poly(hydroxybutyrate) and ε-Poly-l-lysine Submicro- and Microfiber-Based Sustainable Nonwovens with Antimicrobial Activity for Single-Use Applications.

Antimicrobial nonwovens for single use applications (e.g., diapers, sanitary napkins, medical gauze, etc.) are of utmost importance as the first line of defense against bacterial infections. However, the utilization of petrochemical nondegradable polymers in such nonwovens creates sustainability-related issues. Here, sustainable poly(hydroxybutyrate) (PHB) and ε-poly-l-lysine (ε-PLL) submicro- and microfiber-based antimicrobial nonwovens produced by a novel industrially scalable process, solution blowing, have been proposed. In such nonwovens, ε-PLL acts as an active material. In particular, it was found that most of ε-PLL is released within the first hour of deployment, as is desirable for the applications of interest. The submicro- and microfiber mat was tested against C. albicans and E. coli, and it was found that ε-PLL-releasing microfibers result in a significant reduction of bacterial colonies. It was also found that ε-PLL-releasing antimicrobial submicro- and microfiber nonwovens are safe for human cells in fibroblast culture. Mechanical characterization of these nonwovens revealed that, even though they are felt as soft and malleable, they possess sufficient strength, which is desirable in the end-user applications.

Electrochemical Oxidation of Atrazine and Clothianidin on Bi-doped SnO2-Ti nO2 n-1 Electrocatalytic Reactive Electrochemical Membranes.

This research focused on improving mineralization rates during the advanced electrochemical oxidation treatment of agricultural water contaminants. For the first time, bismuth-doped tin oxide (BDTO) catalysts were deposited on Magnéli phase (Ti nO2 n-1, n = 4-6) reactive electrochemical membranes (REMs). Terephthalic acid (TA) was used as a OH• probe, whereas atrazine (ATZ) and clothianidin (CDN) were chosen as model agricultural water contaminants. The BDTO-deposited REMs (REM/BDTO) showed higher compound removal than the REM, due to enhanced OH• production. At 3.5 V/SHE, complete mineralization of TA, ATZ, and CDN was achieved for the REM/BDTO upon a single pass in the reactor (residence time ∼3.6 s). Energy consumption for REM/BDTO was as much as 31-fold lower than the REM, with minimal values per log removal of <0.53 kWh m-3 for TA (3.5 V/SHE), <0.42 kWh m-3 for ATZ (3.0 V/SHE), and 0.83 kWh m-3 for CDN (3.0 V/SHE). Density functional theory simulations provided potential dependent activation energy profiles for ATZ, CDN, and various oxidation products. Efficient mass transfer and a reaction mechanism involving direct electron transfer and reaction with OH• were responsible for the rapid and complete mineralization of ATZ and CDN at very short residence times.

Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid.

Conversion of carbon dioxide (CO2) into fuels is an attractive solution to many energy and environmental challenges. However, the chemical inertness of CO2 renders many electrochemical and photochemical conversion processes inefficient. We report a transition metal dichalcogenide nanoarchitecture for catalytic electrochemical CO2 conversion to carbon monoxide (CO) in an ionic liquid. We found that tungsten diselenide nanoflakes show a current density of 18.95 milliamperes per square centimeter, CO faradaic efficiency of 24%, and CO formation turnover frequency of 0.28 per second at a low overpotential of 54 millivolts. We also applied this catalyst in a light-harvesting artificial leaf platform that concurrently oxidized water in the absence of any external potential.

Dynamic Study of Liquid Drop Impact on Supercooled Cerium Dioxide: Anti-Icing Behavior.

This work deals with the anti-icing behavior at subfreezing temperatures of CeO2/polyurethane nanocomposite coatings with and without a stearic acid treatment on aluminum alloy substrates. The samples ranged from superhydrophilic to superhydrophobic depending on surface morphology and surface functionalization. X-ray photoelectron spectroscopy was used to determine the surface composition. The anti-icing behavior was studied both by importing fog into a chamber with controlled atmosphere at subzero temperatures and by conducting experiments with drop impact velocities of 1.98, 2.8, 3.83, and 4.95 m/s. It was found that the ice-phobicity of the ceramic/polymer nanocomposite coating was dependent on the surface roughness and surface energy. Water drops were observed to completely rebound from the surface at subfreezing temperatures from superhydrophobic surfaces with small contact angle hysteresis regardless of the impact velocity, thus revealing the anti-icing capability of such surfaces.

Robust carbon dioxide reduction on molybdenum disulphide edges.

Electrochemical reduction of carbon dioxide has been recognized as an efficient way to convert carbon dioxide to energy-rich products. Noble metals (for example, gold and silver) have been demonstrated to reduce carbon dioxide at moderate rates and low overpotentials. Nevertheless, the development of inexpensive systems with an efficient carbon dioxide reduction capability remains a challenge. Here we identify molybdenum disulphide as a promising cost-effective substitute for noble metal catalysts. We uncover that molybdenum disulphide shows superior carbon dioxide reduction performance compared with the noble metals with a high current density and low overpotential (54 mV) in an ionic liquid. Scanning transmission electron microscopy analysis and first principle modelling reveal that the molybdenum-terminated edges of molybdenum disulphide are mainly responsible for its catalytic performance due to their metallic character and a high d-electron density. This is further experimentally supported by the carbon dioxide reduction performance of vertically aligned molybdenum disulphide.

Characterization of pore structure in biologically functional poly(2-hydroxyethyl methacrylate)-poly(ethylene glycol) diacrylate (PHEMA-PEGDA).

A copolymer composed of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(ethylene glycol) diacrylate (PEGDA) (PHEMA-PEGDA) is structurally versatile. Its structure can be adjusted using the following porogens: water, sucrose, and benzyl alcohol. Using phase separation technique, a variety of surface architectures and pore morphologies were developed by adjusting porogen volume and type. The water and sucrose porogens were effective in creating porous and cytocompatible PHEMA-PEGDA scaffolds. When coated with collagen, the PHEMA-PEGDA scaffolds accommodated cell migration. The PHEMA-PEGDA scaffolds are easy to produce, non-toxic, and mechanically stable enough to resist fracture during routine handling. The PHEMA-PEGDA structures presented in this study may expedite the current research effort to engineer tissue scaffolds that provide both structural stability and biological activity.

Engineering copolymeric artificial cornea with salt porogen.

Artificial corneas or keratoprostheses (KPros) are designed to replace diseased or damaged cornea. Although many synthetic KPros have been developed, current products are often inappropriate or inadequate for long term use due to ineffective host integration. This study presents an alternative approach of engineering a KPro that comprises a combination of poly (2-hydroxyethyl methacrylate) (PHEMA), poly (methyl methacrylate) (PMMA), and sodium chloride (NaCl) as porogen. Based on the core-skirt model for KPro, the porous outer portion of artificial cornea (skirt) was engineered by combining NaCl with HEMA and MMA monomers to promote tissue ingrowth from the host. The central optic (core) was designed to provide >85% light transmission in the visible wavelength range and securely attached to the skirt. Mechanical tensile data indicated that our KPro (referred to as salt porogen KPro) is mechanically stable to maintain its structure in the ocular environment and during implantation. Using human corneal fibroblasts (HCFs), we demonstrate that the cells grew into the pores of the skirt and proliferated, suggesting biointegration is adequately achieved. This novel PHEMA-PMMA copolymeric salt porogen KPro may offer a cornea replacement option that leads to minimal risk of corneal melting by permitting sufficient tissue ingrowth and mass transport.