No abstract

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.

A structurally interconnected block copolymer was facilely prepared by the oligomerization of poly(oxyethylene)-segmented diamine and 4,4 0 -oxydiphthalic anhydride, followed by a late-stage curing to generate amide-imide cross-linked gels. The gel structure, with multiple functionalities including poly(oxyethylene) segments, amido-acid linkers, amine termini, and amide cross-linker was characterized by Fourier transform infrared spectroscopy. The gel-like copolymer was used to absorb a liquid electrolyte; formation of 3D interconnected nanochannels, as could be observed by field emission scanning electronic microscopy has confirmed this absorption of the liquid electrolyte by the copolymer.This elastomeric copolymer was used as the matrix of a polymer gel electrolyte (PGE) for a dyesensitized solar cell (DSSC), which shows extremely high photovoltaic performance (soaking for 1 h in the electrolyte). In particular, the PGE containing 76.8 wt% of the liquid electrolyte renders a power conversion efficiency of 9.48% for its DSSC, with a short-circuit photocurrent density of 19.50 mA cm À2 , an open-circuit voltage of 0.76 V, and a fill factor of 0.64. The outstanding performance of the gel-state DSSC, superior to that (8.84%) of the DSSC with the liquid electrolyte, is mainly ascribed to the suppression of the back electron transfer through the PGE. Electrochemical impedance spectra, and dark current measurements were used to substantiate the explanations of the photovoltaic parameters.

An imide-functionalized material, poly(oxyethylene)-segmented polymer, was synthesized from the reaction of poly(oxyethylene) diamine of 2000 g mol(-1) M(w) and 4,4'-oxydiphthalic anhydride and used to disperse hybrid nanomaterials of platinum nanoparticles and multi-wall carbon nanotubes (PtNP/MWCNT). The composite material was spin-coated into film and further prepared as the counter electrode (PtNP/MWCNT-CE) for a dye-sensitized solar cell (DSSC). The short-circuit current density (J(SC)) and power-conversion efficiency (eta) of the DSSC with PtNP/MWCNT-CE were found to be 18.01 +/- 0.91 mA cm(-2) and 8.00 +/- 0.23%, respectively, while the corresponding values were 14.62 +/- 0.19 mA cm(-2) and 6.92 +/- 0.07% for a DSSC with a bare platinum counter electrode (Pt-CE). The presence and distribution of PtNP/MWCNT on the CE were characterized by using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The attachment of PtNPs on MWCNTs was observed by transmission electron microscopy (TEM). Cyclic voltammetry (CV), incident-photo-to-current efficiency (IPCE) and electrochemical impedance spectra (EIS) were correlated to explain the efficacy of this nanocomposite system

A hybrid of polymer-dispersed multi-walled carbon nanotubes (MWCNT) was utilized in networking with the conventional composition of gel electrolyte in dye-sensitized solar cells (DSSCs) to purposely enhance the cell efficiency. The requisite polymer as the dispersant is structurally tailored for its functionalities consisting of poly(oxyethylene)-segmented amides and imides. The existence of the dispersant is multi-functional for first de-bundling the originally aggregated MWCNT and subsequently networking with the conventional gel electrolyte, poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-HFP)/LiI system. The gel electrolyte comprised of only 0.25 wt% MWCNT/POEM in the finely dispersed state was fabricated into a quasi-solid-state DSSC which showed high power-conversion efficiency (h) of 6.86% and short-circuit current density (J SC ) of 15.3 mA cm À2 at the test of 100 mW cm À2 irradiation. The DSSC efficiency was significantly improved from the use of the unmodified gel electrolyte having the values of J SC ¼ 9.6 mA cm À2 and h ¼ 4.63%. The enhancement was further confirmed by the electrochemical impedance spectra analyses for the lowest Warburg resistance (R w ). The fine dispersion of MWCNT in the polymeric dispersant was characterized by UV-Vis, TEM, FT-IR and DSC. The finding indicates the role of MWCNT for homogenizing the amorphous PVDF-HFP and facilitating the diffusion state of I À /I 3 À ion pairs in this electrolyte system.