Novel polymer gel electrolyte with organic solvents for quasi-solid-state dye-sensitized solar cells.

A cross-linked copolymer was previously synthesized from poly(oxyethylene) diamine (POE-amine) and an aromatic anhydride and cured to generate an amide-imide cross-linking structure. The copolymer containing several chemical groups such as POE, amido acids, and imide, enabled to absorb liquid electrolytes in methoxypropionitrile (MPN) for suitable uses in dye-sensitized solar cells. To establish the advantages of polymer gel electrolytes (PGE), the same copolymer was studied by using different electrolyte solvents including propylene carbonate (PC), dimethylformamide, and N-methyl-2-pyrrolidone, and shown their long-term stability. The morphology of the copolymer after absorbing liquid electrolytes in these solvents was proven the same as a 3D interconnected nanochannels, evidenced field emission-scanning electron microscopy. Among these solvents, PC was selected as the optimized PGE, which demostrated a higher power conversion efficiency (8.31%) than that of the liquid electrolyte (7.89%). In particular, the long-term stability of only a 5% decrease in the cell efficiency after 1000 h of testing was achieved. It was proven the developed copolymer as PGE was versatile for different solvents showing high efficiency and long-term durability.

Controlling formation of silver/carbon nanotube networks for highly conductive film surface.

Flexible polymer films with high electrical conductivity were prepared through a simple coating of well-dispersed silver nanoparticle (AgNP) and multiwalled carbon nanotube (CNT) solution. The hybrid film with surface resistance as low as 1 × 10(-2) Ω/sq was prepared by controlling the annealing temperature in air and by using a suitable composition of silver nitrate/CNT/poly(oxyethylene)-oligo(imide) (POE-imide) in the ratio 20:1:20 by weight. During the heating, color of the film surface changed from black to golden to milky white, indicating the accumulation of AgNPs through surface migration and melting into CNT-connected networks. Thermogravimetric measurements showed that the transition temperature of 170 °C was responsible for the POE-imide degeneration and the subsequent Ag melting with a decrease in the surface resistance from 2.1 × 10(5) to 2.0 × 10(-1) Ω/sq, which was able to illuminate light-emitting diode lamps because of the formation of a continuous Ag network.

The cellular responses and antibacterial activities of silver nanoparticles stabilized by different polymers.

Silver nanoparticles (AgNPs) are known for their excellent antibacterial activities. The possible toxicity, however, is a major concern for their applications. Three types of AgNPs were prepared in this study by chemical processes. Each was stabilized by a polymer surfactant, which was expected to reduce the exposure of cells to AgNPs and therefore their cytotoxicity. The polymer stabilizers included poly(oxyethylene)-segmented imide (POEM), poly(styrene-co-maleic anhydride)-grafting poly(oxyalkylene) (SMA) and poly(vinyl alcohol) (PVA). The cytotoxicity of these chemically produced AgNPs to mouse skin fibroblasts (L929), human hepatocarcinoma cells (HepG2), and mouse monocyte macrophages (J774A1) was compared to that of physically produced AgNPs and gold nanoparticles (AuNPs) as well as the standard reference material RM8011 AuNPs. Results showed that SMA-AgNPs were the least cytotoxic among all materials, but cytotoxicity was still observed at higher silver concentrations (>30 ppm). Macrophages demonstrated the inflammatory response with cell size increase and viability decrease upon exposure to 10 ppm of the chemically produced AgNPs. SMA-AgNPs did not induce hemolysis at a silver concentration below 1.5 ppm. Regarding the antibacterial activity, POEM-AgNPs and SMA-AgNPs at 1 ppm silver content showed 99.9% and 99.3% growth inhibition against E. coli, while PVA-AgNPs at the same silver concentration displayed 79.1% inhibition. Overall, SMA-AgNPs demonstrated better safety in vitro and greater antibacterial effects than POEM-AgNPs and PVA-AgNPs. This study suggested that polymer stabilizers may play an important role in determining the toxicity of AgNPs.

The disruption of bacterial membrane integrity through ROS generation induced by nanohybrids of silver and clay.

Nanohybrids, synthesized via silver nitrate reduction in the presence of silicate clay, exhibit a high potency against bacterial growth. The plate-like clay, due to its anionic surface charges and a large surface area, serves as the support for the formation of silver nanoparticles (AgNPs) approximately 30 nm in diameter. The nanohybrid consisting of Ag/silicate at a 7/93 weight ratio inhibited the growth of dermal pathogens including Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa and Streptococcus pyrogens, as well as the methicillin- and oxacillin-resistant S. aureus (MRSA and ORSA). Scanning electron microscope revealed that these nanohybrids were adherent on the surface of individual bacteria. The thin silicate plates provide a surface for immobilizing AgNPs in one highly concentrated area but prevent them from entering the cell membrane. Subsequent cytotoxicity studies indicated that surface contact with the reduced AgNPs on clay is sufficient to initiate cell death. This toxicity is related to a loss in membrane integrity due to reactive oxygen species (ROS) generation. The hybridization of AgNPs on clay surface is viable for generating a new class of nanohybrids exhibiting mild cytotoxicity but high efficacy for battling drug-resistant bacteria.