Design of Poly(Acrylonitrile)-Based Gel Electrolytes for High-Performance Lithium Ion Batteries

The use of polyacrylonitrile (PAN) as a host for gel polymer electrolytes (GPEs) commonly produces a strong dipole–dipole interaction with the polymer. This study presents a strategy for the application of PAN in GPEs for the production of high performance lithium ion batteries. The resulting gel electrolyte GPE-AVM comprises a poly­(acrylonitrile-co-vinyl acetate) copolymer blending poly­(methyl methacrylate) as a host, which is swelled using a liquid electrolyte (LE) of 1 M LiPF6 in carbonate solvent. Vinyl acetate and methacrylate groups segregate the PAN chains in the GPE, which produces high ionic conductivity (3.5 × 10 –3 S cm–1 at 30 °C) and a wide electrochemical voltage range (>6.5 V) as well as an excellent Li+ transference number of 0.6. This study includes GPE-AVM in a full-cell battery comprising a LiFePO4 cathode and graphite anode to promote ion motion, which reduced resistance in the battery by 39% and increased the specific power by 110%, relative to the performance of batteries based on LE. The proposed GPE-based battery has a capacity of 140 mAh g–1 at a discharge rate of 0.1 C and is able to deliver 67 mAh g–1 of electricity at 17 C. The proposed GPE-AVM provides a robust interface with the electrodes in full-cell batteries, resulting in 93% capacity retention after 100 charge–discharge cycles at 17 C and 63% retention after 1000 cycles

Graphite Oxide with Different Oxygenated Levels for Hydrogen and Oxygen Production from Water under Illumination: The Band Positions of Graphite Oxide

Graphite oxide (GO) photocatalysts derived from graphite oxidation can have varied electronic properties by varying the oxidation level. Absorption spectroscopy shows the increasing band gap of GO with the oxygen content. Electrochemical analysis along with the Mott–Schottky equation show that the conduction and valence band edge levels of GO from appropriate oxidation are suitable for both the reduction and the oxidation of water. The conduction band edge shows little variation with the oxidation level, and the valence band edge governs the bandgap width of GO. The photocatalytic activity of GO specimens with various oxygenated levels was measured in methanol and AgNO₃ solutions for evolution of H₂ and O₂, respectively. The H₂ evolution was strong and stable over time, whereas the O₂ evolution was negligibly small due to mutual photocatalytic reduction of the GO with upward shift of the valence band edge under illumination. The conduction band edge of GO showed a negligible change with the illumination. When NaIO₃ was used as a sacrificial reagent to suppress the mutual reduction mechanism under illumination, strong O₂ evolution was observed over the GO specimens. The present study demonstrates that chemical modification can easily modify the electronic properties of GO for specific photosynthetic applications

Electron Transport Dynamics in TiO₂ Films Deposited on Ti Foils for Back-Illuminated Dye-Sensitized Solar Cells

In this study, we examine the electron transport dynamics in TiO2 films of back-illuminated dye-sensitized solar cells. The TiO2 films are fabricated using electrophoretic deposition (EPD) and the conventional paste-coating (PC) of TiO2 nanoparticles on Ti-foil substrates. Intensity-modulated photocurrent spectroscopy reveals that red-light irradiation is more efficient than blue-light irradiation for generating photocurrents for back-illuminated cells. A single trapping–detrapping diffusion mode, without trap-free diffusion, reveals the electron transport dynamics involved in the backside illumination. The closely-packed EPD films exhibit a shorter electron transit time than does the loosely packed PC films. The porosity dependence of the electron diffusion rate is consistent with the 3D percolation model for metallic solid spheres. The EPD films possess longer electron lifetimes because of their smaller void fraction, which suppresses recombination with electrolytes. The EPD cells, which feature rapid electron transport and suppressed recombination in the TiO2 films, exhibit a maximum power conversion efficiency of 7.1%, which is higher than that of PC cells (6.0%). Because the distance between electron injection and collection is close to the film thickness and the transport lacks trap-free diffusion, the performance of back-illuminated cells is more sensitive to TiO2 film thickness and porosity than the performance of the front-illuminated cells. This study demonstrates the advantages of EPD-film architecture in promoting charge collection for high power conversion

Flow cytometry analysis of <i>P</i>_<i>hag</i><i>-GFP</i> at various concentrations of ZnO NPs.

<p>Wild-type bacteria were grown at different ZnO-NP concentrations for 3 h. <b>A</b>: PBS, <b>B</b>: unstained cells, <b>C</b>: 0 ppm, <b>D</b>: 10 ppm, <b>E</b>: 25 ppm, <b>F</b>: 50 ppm, and <b>G</b>: 100 ppm. The X axis indicates GFP fluorescence intensity (arbitrary units: au), and the Y axis indicates cell counts.</p

XANES and EXAFS spectra for <i>B</i>. <i>subtilis</i> cells treated with ZnO NPs.

<p><b>A.</b> ZnO K-edge XANES spectra of silver standards and <i>B</i>. <i>subtilis</i> cells treated with 100 ppm of ZnO-NPs. <b>B.</b> ZnO K-edge EXAFS spectra of ZnO standards and <i>B</i>. <i>subtilis</i> cells treated with 100 ppm of ZnO-NPs. The best-fitting EXAFS spectra are indicated by the colored symbol lines. (Zn-Zn standard: red; ZnO standard: blue; <i>Bacillus subtilis</i> cells treated with 100 ppm of ZnO-NPs: black).</p

ZnO NPs affect biofilm formation.

<p><b>A.</b> The pellicle column depicts microtiter wells (6-well plate) in which cells were grown in biofilm medium with various concentrations of ZnO NPs at 25°C for 3 days (scale bar: 2 cm). Bacterial wild-type (3610) and mutant strains are indicated as follows: <i>sinR</i> (DS92), <i>epsA-O</i> (DS696), <i>sfp</i> (DS3629), <i>tasA</i> (DS3630), and <i>sinR epsA-O</i> (HS222). <b>B.</b> Images of a 12-well microtiter dish containing ethanol-precipitated supernatant from the indicated strain, following treatment with different concentrations of ZnO NPs. <b>C</b>. The supernatants of the indicated strains were treated with proteinase K, DNase, and RNase, precipitated with ethanol, and resolved through SDS-PAGE on a 12% gel, after which staining with Stains-All was performed. <b>D.</b> FT-IR spectra analysis of EPS from <i>Bacillus</i> cells treated with ZnO NPs. Wild type bacteria were grown at ZnO NP concentrations of 0, 5, 10, 25, and 50 ppm, and untreated <i>eps</i> mutant cells were grown to serve as a negative control.</p

ZnO Nanoparticles Affect <i>Bacillus subtilis</i> Cell Growth and Biofilm Formation

<div><p>Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect <i>Bacillus subtilis</i>, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on <i>B</i>. <i>subtilis</i> growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that <i>B</i>. <i>subtilis</i> growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and P<i>_hag</i>-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, <i>B</i>. <i>subtilis</i> reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that <i>B</i>. <i>subtilis</i> biofilm surface structures became smooth under ZnO-NP concentrations of only 5–10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured <i>B</i>. <i>subtilis</i> cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn⁺ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect <i>B</i>. <i>subtilis</i> viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.</p></div

<i>P</i>_<i>hag</i><i>-GFP</i> at varying concentrations of ZnO NPs.

<p>Fluorescent micrographs of <i>B</i>. <i>subtilis</i> cells show the expression of <i>P</i>_{<b><i>hag</i></b>}<i>-GFP</i> after cultivation with ZnO-NP concentrations of 0, 5, 10, 25, 50, and 100 ppm for 3 h. GFP reporter expression presents a false green color. DAPI presents a false blue color. Scale bar: 10 μm.</p

Flow cytometry and fluorescent micrograph analysis of RedoxSensor activity in <i>B</i>. <i>subtilis</i>.

<p>Wild-type bacteria were grown for 3 hrs at ZnO-NP concentrations of 0 ppm, 10 ppm, 25 ppm, 50 ppm, 100 ppm. Unstained samples and PBS buffer alone were used as controls. The X axis indicates RedoxSensor or PI fluorescence intensity (arbitrary units: au), and the Y axis indicates cell counts. <b>A.</b> Flow cytometry analysis of Redoxsensor activity, and <b>B.</b> Flow cytometry analysis of PI activity. <b>C.</b> Fluorescent micrographs of <i>B</i>. <i>subtilis</i> cells indicate RedoxSensor activity or PI fluorescence after incubation with different concentrations of ZnO-NPs for 3 h. Redoxsensor activity presents a false green color. PI presents a false red color. Scale bar: 10 μm.</p

Photocatalytically Reduced Graphite Oxide Electrode for Electrochemical Capacitors

Graphene sheets are an ideal carbon material with the highest area available for electrolyte interaction and can be obtained by reducing graphite oxide (GO). This study presents the photocatalytic reduction of GO in water with mercury-lamp irradiation. The specific capacitance of the reduced GO in an H₂SO₄ aqueous solution reached levels as high as 220 F g^–1. This is because of the double layer formation and the reversible pseudocapacitive processes caused by oxygen functionalities at the sheet periphery. The rate capability for charge storage increases with irradiation time due to the continued reduction of oxygenated sites on the graphene basal plane. Alternating current impedance analysis shows that prolonged light irradiation promotes electronic percolation in the electrode, significantly reducing the capacitive relaxation time. With a potential widow of 1 V, the resulting symmetric cells can deliver an energy level of 5 Wh kg^–1 at a high power of 1000 W kg^–1. These cells show superior stability, with 92% retention of specific capacitance after 20 000 cycles of galvanostatic charge–discharge