Regeneration of Activated Sludge into SiO2-Decorated Heteroatom-Doped Porous Carbon as Advanced Electrodes for Li-S Batteries.

The regeneration of harmful activated sludge into an energy source is an important strategy for municipal sludge treatment and recycling. Herein, SiO2-modified N,S auto-doped porous carbon (NSC@SiO2) with high conductivity (70 S m-1) is successfully obtained through a simple calcination method of the activated sludge from wastewater treatment. Further, P-doped NSC@SiO2 (NSPC@SiO2) is designed to achieve a higher surface area (891 m2 g-1 vs 624 m2 g-1), a larger pore volume (0.87 cm3 g-1 vs 0.08 cm3 g-1), and more carbon defects. Due to its special structure, NSPC@SiO2 is used as a sulfur host of lithium-sulfur batteries. The results of polysulfide adsorption experiments, S 2p X-ray photoelectron spectra (XPS), Li2S nucleation experiments, polysulfide symmetric cells, measurement of the galvanostatic intermittent titration (GITT), polarization voltage difference, lithium-ion diffusion rate, and Tafel slope verified that NSPC@SiO2 greatly improved the adsorption capacity of polysulfides, lowered the barrier to Li2S formation and the internal resistances of cells, and accelerated Li+ ion diffusion and the reaction kinetics of polysulfide conversion, resulting in the excellent performance of polysulfide capture and superior rate performance and cyclic stability. By comparing NSPC@SiO2 with NSC@SiO2, a higher initial capacity (1377 mAh g-1 vs 1150 mAh g-1 at 0.1C), better rate capacity (912 mAh g-1 vs 719 mAh g-1 at 2C), and low capacity decay (0.094% per cycle within 200 cycles) are obtained. Our work provides direction for the treatment, disposal, and resource utilization of activated sludge.

Interference-free and single exposure to generate continuous cycloidal alignment for large-area liquid crystal devices.

An approach for generating cycloidal pattern of liquid crystal (LC) molecules based on interference-free and single exposure is illustrated. The spatial manipulation of polarization state is achieved using birefringent prism and wave plates. And then, the spatially variant polarization of exposure beam is transferred to LC molecules by azo-dye photo-sensitive layer. Consequently, the LC samples fabricated shows periodically cycloidal texture and diffraction efficiency more than 99%. The measured period Λ and diffraction angle are in good consistency with theoretical results. Thus, this exposure method provides an effective and robust way for fabricating large-area LC elements, therefore paving the way for widespread applications of high-performance diffractive LC devices.

The mechanism of thiophene oxidation on metal-free two-dimensional hexagonal boron nitride.

Hexagonal boron nitride (h-BN) as an outstanding catalyst has been applied in oxidative desulfurization (ODS). In order to increase its catalytic performance, deep insight into the catalytic mechanism is urgent. In this work, DFT calculations were carried out to explore thiophene oxidation on the h-BN surface sites, involving the perfect and zigzag B, zigzag N, and armchair edge sites, and B- or N-monovacancy site. The calculated results show that O2 is easily activated on defect sites such as the edge sites and N-vacancy sites. For the thiophene oxidation mechanism, our results show that the zigzag N edge site is the most favorable active site, followed by the armchair and zigzag B edge sites. For the vacancy sites, although they are active for O2 dissociation, the dissociated O is trapped in the vacancy site, and they are not active for eventual sulfone formation.

H2O2 decomposition mechanism and its oxidative desulfurization activity on hexagonal boron nitride monolayer: A density functional theory study.

Hydrogen peroxide (H2O2) decomposition mechanism and its oxidative desulfurization activity on hexagonal boron nitride monolayer (h-BN) have been explored by density functional theory (DFT) at M06-2X/6-311 + G (d,p) level. A cluster model which contains seven rings has been constructed to simulate the h-BN surface. It is found that 7 possible species will be generated after the decomposition of H2O2. Among them, 2H*+O2* and 2H*+2O* are relatively unstable while other species, such as HOO*+H*, HO*+HO*, H*+HO + O*, H2O*+O* are relatively stable and may exist in the current system. In addition, 4 decomposition pathways have been explored. Results show that the H2O2* will first undergo an O-H bond break (HOO*+H*), then the HO-O bond decomposes into H*+HO*+O* (Pathway (b)). By considering the concentration and activation energy together, the H2O*+O* is proposed to be the most possible active species for oxidative desulfurization due to the relative higher concentration and lower activation energy.

Colorimetric detection of kanamycin based on analyte-protected silver nanoparticles and aptamer-selective sensing mechanism.

In this work, a novel colorimetric detection method for kanamycin (Kana), a widely used aminoglycoside antibiotic, has been developed using unmodified silver nanoparticles (AgNPs) as sensing probe. The method is designed based on the finding that the analyte (Kana) can protect AgNPs against salt-induced aggregation, and nucleic acid aptamers can decrease the risk of false positives through an aptamer-selective sensing mechanism. By use of the proposed method, selective quantification of Kana can be achieved over the concentration range from 0.05 to 0.6 µg mL(-1) within 20 min. The detection limit is estimated to be 2.6 ng mL(-1), which is much lower than the allowed maximum residue limit. Further studies also demonstrate the applicability of the proposed method in milk samples, revealing that the method may possess enormous potential for practical detection of Kana in the future.