High yielded Co-C derived from polyester-Cobalt carbothermal reduction for efficient activation of peroxymonosulfate to degrade levofloxacin.

A kind of high yield and recyclable Cobalt-Carbon composite (Zn1Co5/PnC) was prepared by carbothermal reduction process, in which the cobalt acetate and zinc acetate were considered as Zn and Co precursors, and the polyester waste was evolved as the carbon precursor. The morphology, structure and composition of the composite were characterized using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results showed that evaporation of zinc contributed to the formation of porous carbon structure, and the Co nanoparticles were wrapped and protected by the porous carbon matrix. The Zn1Co5/PnC activated peroxymonosulfate (PMS) system (Zn1Co5/PnC/PMS) was constructed to degrade the levofloxacin (LEV). The activity and mechanism of LEV degradation was understood. The LEV degradation efficiency was high to 96.60% within 90 min in the presence of Zn1Co5/P4C. Moreover, the Zn1Co5/P4C still maintained favorable PMS activation performance after five-cycle runs. The results show that the Zn1Co5/P4C played positive role in activating the PMS, it may be due to the facts that the polyester derived carbon could supported the Co while the evaporated Zn could increase the surface area of Zn1Co5/P4C, leading to the increased activity. The possible degradation pathways were proposed by identifying the intermediate products through liquid chromatography-mass spectrometry analysis. This study put forward a promising method to use polyester waste to synthesize high yield cobalt-carbon composite for degrading the antibiotic in wastewater.

Spatial-mode-coupling-based dispersion engineering for integrated optical waveguide.

Dispersion ultimately limits the efficiency of the nonlinear process in the optical waveguide. Traditional dispersion engineering method is to tailor the cross-section of the waveguide with both of the height and width. However, the fabrication process limits the design freedom of the height in some cases. To solve the problem, we develop a dispersion engineering technique based on spatial mode coupling. Just by tailoring the width of waveguide without altering the height, the proposed method achieves anomalous dispersion with a range of 70 nm numerically and experimentally changes the dispersion of a micro-ring resonator from -750 ± 30 ps/nm/km to 1300 ± 200 ps/nm/km over a wavelength range of 25 nm with high Q of 0.8 million on the Si3N4/SiO2 waveguide platform. This technique overcomes the restrict from the fabrication process to the optical waveguide on the dispersion control and can enlarge application of the nonlinear optics on chip.