<i>p</i>- and <i>n</i>‑type Doping Effects on the Electrical and Ionic Conductivities of Li₄Ti₅O₁₂ Anode Materials

We systematically investigated p- and n-type doping effects on the electrical conductivity of spinel Li₄Ti₅O₁₂ (LTO) by designing theoretically stoichiometric Li₁₁Ti₁₃O₃₂ (p-type) and Li₁₀Ti₁₄O₃₂ (n-type) because LTO has a nonstoichiometric (Li)₈[Li_8/3Ti_40/3]­O₃₂ formula with the <i>Fd</i>3<i>m̅</i> space group. In this work, we present evidence that the electronic modification plays a fundamental role in the electrical conductivity of LTO, especially, n-type Li₁₀Ti₁₄O₃₂, which has superior electrical conductivity compared to p-type Li₁₁Ti₁₃O₃₂. We proposed a way to improve the electrical conductivity of pristine LTO by halogen ion doping, Li₄Ti₅O_{12–<i>x</i>}Hal_<i>x</i> (Hal: F, Cl, and Br), for an n-type doping effect. However, the substitution of halogen ions can enhance the electrical conductivity by mixing Ti⁴⁺/Ti³⁺ and impede the Li ion diffusion in the lattice. The larger size of Cl and Br increases the Li ion diffusion energy barrier with van der Waals repulsion. Therefore, our theoretical investigations of the effects of halogen doping on the electrical and ionic conductivities anticipate that the smaller-sized F may be the most promising dopant for improving the performance of LTO

Cell growth and rhG-CSF expression during the fed-batch culture.

<p><i>E. coli</i> JM109/pPT-G-CSF cells were grown in fed-batch culture using temperature shift method in a 300-L fermentor with glucose as the energy source. Optical density was detected using a spectrophotometer at 600 nm. Glucose concentration (grey triangle); OD₆₀₀ (●); Expression rate of rhG-CSF (□). The arrow indicates the start time of feeding.</p

rhG-CSF analyses.

<p><b>A</b>. RP-HPLC chromatogram of rhG-CSF. Samples (30 μg) containing rhG-CSF for analysis was loaded on the RP-HPLC column. <b>B</b>. GPC-HPLC chromatogram of rhG-CSF. <b>C</b>. MALDI mass spectra of rhG-CSF.</p

The analysis of rhG-CSF protein by SDS-PAGE and IEF.

<p><b>A</b>. A 4–12% discontinuous NuPAGE SDS-PAGE gel and Coomassie brilliant blue staining were used to confirm the purity of rhG-CSF. Lane 1, molecular weight marker; lane 2, standard rhG-CSF (Filgrastim); lane 3, rhG-CSF. <b>B</b>. The Novex pH 3–10 IEF gel was used to examine the purity of rhG-CSF. The IEF marker indicates pI. Lane 1, pI marker 4.5–7.4; lane 2, standard hG-CSF; lane 3, purified rhG-CSF. The arrow indicates rhG-CSF.</p

Analysis of rhG-CSF protein by SDS-PAGE.

<p>Upon IPTG induction, rhG-CSF was analyzed using a 4–12% reducing SDS-PAGE gel followed by Coomassie brilliant blue staining. <b>A.</b> Lane 1, cell homogenates of <i>E. coli</i> JM109/pPT-G-CSF without IPTG induction; lane 2, cell homogenates after IPTG induction for 1 h; lane 3, After IPTG induction for 3 h; lane 4, After IPTG induction for 5 h. <b>B.</b> Lane 1, total homogenates; lane 2, supernatant after centrifugation; lane 3, Pellet after centrifugation. Most of IPTG induced rhG-CSF is pelleted after centrifugation. The arrow indicates rhG-CSF.</p

Prep-HPLC chromatogram and IEF analysis.

<p>Prep-HPLC chromatography was performed to detect rhG-CSF protein. <b>A</b>. Chromatogram of prep-HPLC with the sup after pH precipitation of refolded rhG-CSF. <b>B</b>. IEF analysis of each fraction from A to H obtained by Prep-HPLC. The IEF marker indicates pI. Lane 1, pI marker 4.5–7.4. Absorbance is in milliabsorbance units (mAU).</p

The purity of rhG-CSF is increased following refolding from inclusion bodies.

<p>Insoluble fraction of the induced culture were harvested, refolded, and precipitated under the stepwise decrease of pH (7.5→5.5). The refolded samples before and after pH precipitation process were analyzed by reducing 4-12% SDS-PAGE, followed by Coomassie brilliant blue staining. Lane 1, solubilized IBs; lane 2, refolded IBs before pH precipitation; lane 3, supernatant (Sup) after pH 7.5 precipitation; lane 4, sup after pH 6.5 precipitation; Lane 5, sup after pH 5.5 precipitation. The arrow indicates rhG-CSF.</p

Peptide map and Western blot analysis of standard hG-CSF and purified rhG-CSF.

<p><b>A</b>. Two chromatograms of standard hG-CSF and rhG-CSF are overlapped for comparison. The solid arrow is the chromatogram for rhG-CSF and the dotted arrow is the chromatogram for standard hG-CSF. Absorbance is in absorbance units (AU). <b>B</b>. Two rhG-CSF proteins were examined by western blot after a 4–12% reducing SDS-PAGE performance. Lane 1, standard rhG-CSF (Filgrastim, 5 μg); lane 2, purified rhG-CSF (5 μg). The arrow indicates rhG-CSF.</p

Biological activity of rhG-CSF protein.

<p>The rhG-CSF protein was assessed for its ability to stimulate the proliferation of an NSF-60 cells. The cells were incubated for 48 h in the presence of rhG-CSF. As a control, standard hG-CSF (WHO 2^nd International Standard) was also analyzed. The bioactivity of rhG-CSF on NFS-60 cell proliferation was measured using the reagent WST-1. Data are the mean ± SD of triplicate measurements (significant versus control, p<0.05).</p

Hierarchically Designed 3D Holey C₂N Aerogels as Bifunctional Oxygen Electrodes for Flexible and Rechargeable Zn-Air Batteries

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey C₂N aerogels (S-C₂NA) as bifunctional catalysts for Zn-air and Li-O₂ batteries. The S-C₂NA exhibited ultrahigh surface area (∼1943 m² g^–1) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO₂) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C–N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-C₂NA air cathodes exhibit superb energy densities (958 and 862 Wh kg^–1), low charge–discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO₂ catalysts, respectively. Notably, Li-O₂ batteries with S-C₂NA demonstrated an outstanding specific capacity of ∼648.7 mA h g^–1 and reversible charge–discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics