High-Performance Capacitive Deionization Disinfection of Water with Graphene Oxide-graft-Quaternized Chitosan Nanohybrid Electrode Coating.

Water disinfection materials should ideally be broad-spectrum-active, nonleachable, and noncontaminating to the liquid needing sterilization. Herein, we demonstrate a high-performance capacitive deionization disinfection (CDID) electrode made by coating an activated carbon (AC) electrode with cationic nanohybrids of graphene oxide-graft-quaternized chitosan (GO-QC). Our GO-QC/AC CDID electrode can achieve at least 99.9999% killing (i.e., 6 log reduction) of Escherichia coli in water flowing continuously through the CDID cell. Without the GO-QC coating, the AC electrode alone cannot kill the bacteria and adsorbs a much smaller fraction (<82.8 ± 1.8%) of E. coli from the same biocontaminated water. Our CDID process consists of alternating cycles of water disinfection followed by electrode regeneration, each a few minutes duration, so that this water disinfection process can be continuous and it only needs a small electrode voltage (2 V). With a typical brackish water biocontamination (with 10(4) CFU mL(-1) bacteria), the GO-QC/AC electrodes can kill 99.99% of the E. coli in water for 5 h. The disinfecting GO-QC is securely attached on the AC electrode surface, so that it is noncontaminating to water, unlike many other chemicals used today. The GO-QC nanohybrids have excellent intrinsic antimicrobial properties in suspension form. Further, the GO component contributes toward the needed surface conductivity of the CDID electrode. This CDID process offers an economical method toward ultrafast, contaminant-free, and continuous killing of bacteria in biocontaminated water. The proposed strategy introduces a green in situ disinfectant approach for water purification.

Modified chitosan emulsifiers: small compositional changes produce vastly different high internal phase emulsion types.

High internal phase emulsions (HIPEs) are indisputably a core technology for various industries involving pharmaceuticals, food, cosmetics, and biologics but they usually require surfactants/co-surfactants to form, which is often undesired. More specifically, micro-HIPEs are thermodynamically stable, optically clear emulsions with droplet sizes in the range of around 1-100 nm that form spontaneously with little energy input but are rare. Mini-/macro-HIPEs have larger droplet sizes in the range of 50-500 nm and >500 nm, respectively, and typically require high energy input for emulsification. We have synthesized a series of chitosan-graft-oligoN-isopropylacrylamide-graft-oligolysine (CSNLYS) copolymers that act as both emulsifiers for HIPEs without needing extraneous surfactants as well as the matrix material of the resulting porous solid polyHIPE. By merely adjusting the length of the oligolysine graft from relatively long to medium to short, we can form either a micro-, mini- or macro-HIPE, respectively. These emulsions can then be solidified into porous polymers, polyHIPEs, simply by increasing the temperature by exploiting the copolymer thermo-responsiveness and then removing the solvents. These porous polyHIPE, particularly the ones from micro-HIPEs, have surface areas as high as 988 m2 g-1 and pore sizes below 200 nm.

Injectable, interconnected, high-porosity macroporous biocompatible gelatin scaffolds made by surfactant-free emulsion templating.

High-porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil-in-water high internal phase emulsions (HIPEs) stabilized by gelatin-graft-poly(N-isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell-laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.

High internal phase emulsion templating with self-emulsifying and thermoresponsive chitosan-graft-PNIPAM-graft-oligoproline.

High internal phase emulsion (HIPE)-templating is an attractive method of producing high porosity polymer foams with tailored pore structure, pore size and porosity. However, this method typically requires the use of large amounts of surfactants to stabilize the immiscible liquid phases, and polymerizable monomers/cross-linker in the continuous minority phase to solidify the HIPE, which may not be desirable in many applications. We show that polyHIPEs with a porosity of 73% can be formed solely using a copolymer of chitosan-graft-PNIPAM-graft-oligoproline (CSN-PRO), which acts simultaneously as emulsifier and thermoresponsive gelator, and forms upon removal of the liquid templating phases, the bulk structure of the resulting polyHIPE. With only a small amount of surfactant (1%v/v in the aqueous phase), and varying the polymer concentration and internal phase volume ratio, different polyHIPEs with porosities of up to 99%, surface areas in excess of 300 m(2)/g and controlled pore interconnectivity can be formed. The poly(CSN-PRO)HIPEs are also shown to be thermoresponsive and remained intact when immersed into water above 34 °C but dissolve below their LCST, which is useful for applications such as drug delivery and tissue engineering scaffolds.

High capacitive performance of flexible and binder-free graphene-polypyrrole composite membrane based on in situ reduction of graphene oxide and self-assembly.

Exploiting flexible and binder-free electrode materials is of importance for the fast development of smart supercapacitor devices. A simple and effective strategy is demonstrated to fabricate a flexible composite membrane of reduced graphene oxide and polypyrrole nanowire (RGO-PPy) via in situ reduction of graphene oxide and self-assembly. More importantly, the shape and thickness of the membrane can be reasonably controlled by varying either the concentration of GO and PPy nanowires or the filtration volume. By direct coupling of two membrane electrodes, symmetric supercapacitors can be fabricated without the use of a binder and conductive additive. The supercapacitor is able to offer large areal capacitance (175 mF cm(-2)) and excellent cycling stability (~93% capacitance retention after 5000 charge-discharge cycles), thanks to the synergic integration between RGO sheets and PPy nanowires and the unique self-assembled porous structure.

High water content hydrogel with super high refractive index.

Transparent, high water content (>65%), and cytocompatible hydrogels, which also possess super high refractive indices (RI > 1.5), are needed for ophthalmological applications. Most hydrogels can achieve either high RI or high water content but not both in the same system because water is a low RI material. Here, high water content/high RI hydrogels fabricated through elevated-temperature UV polymerization of an aqueous solution of acrylamide (AM) and methacrylamide (MAM) with tri(ethylene glycol) dimethacrylate (TEDA) crosslinker are reported. By varying the AM:MAM ratios (2:8 to 8:2) and crosslinker density (5 to 11 mol %), it is discovered that high water content (66%) AM:MAM copolymer hydrogels exhibiting anomalously high refractive indices (1.53); they are also colorless, transparent (99.4%), and cytocompatible with human keratinocytes.