Suzhen Ren

A sensor for formaldehyde detection: luminescent metal–organic framework [Zn2(H2L)(2,2′-bpy)2(H2O)]n

Density functional theory and time-dependent density functional theory methods have been used to investigate the hydrogen bonding between the Metal–organic framework [Zn2(H2L)(2,2′-bpy)2(H2O)]n and formaldehyde in the electronically excited state. The calculated geometric configuration, 1H NMR chemical shift and IR spectra of the hydrogen-bonded complex demonstrated that the hydrogen bond was strengthened in the excited state S1. The strengthening of the hydrogen bond in the S1 state would lead to a luminescence decreasing phenomenon of [Zn2(H2L)(2,2′-bpy)2(H2O)]n, and the fluorescent rate constant of [Zn2(H2L)(2,2′-bpy)2(H2O)]n was decreased when encapsulating formaldehyde into it. Taken together, these results indicated that [Zn2(H2L)(2,2′-bpy)2(H2O)]n could be used for the detection of formaldehyde.

Co 3 O 4 nanoparticles assembled on polypyrrole/graphene oxide for electrochemical reduction of oxygen in alkaline media

ABSTRACT The development of highly efficient catalysts for cathodes remains an important objective of fuel cell research. Here, we report Co 3 O 4 nanoparticles assembled on a polypyrrole/graphene oxide electrocatalyst (Co 3 O 4 /Ppy/GO) as an efficient catalyst for the oxygen reduction reaction (ORR) in alkaline media. The catalyst was prepared via the hydrothermal reaction of Co 2+ ions with Ppy-modified GO. The GO, Ppy/GO, and Co 3 O 4 /Ppy/GO were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The incorporation of Ppy into GO nanosheets resulted in the formation of a nitrogen-modified GO porous structure, which acted as an efficient electron-transport network for the ORR. With further anchoring of Co 3 O 4 on Ppy/GO, the as-prepared Co 3 O 4 /Ppy/GO exhibited excellent ORR activity and followed a four-electron route mechanism for the ORR in alkaline solution. An onset potential of −0.10 V vs. a saturated calomel electrode and a diffusion limiting current density of 2.30 mA/cm 2 were achieved for the Co 3 O 4 /Ppy/GO catalyst heated at 800 °C; these values are comparable to those for noble-metal-based Pt/C catalysts. Our work demonstrates that Co 3 O 4 /Ppy/GO is highly active for the ORR. Notably, the Ppy coupling effects between Co 3 O 4 and GO provide a new route for the preparation of efficient non-precious electrocatalysts with hierarchical porous structures for fuel cell applications.

Enhanced dyes removal properties of hollow SnO2 Microspheres and SnO2@C composites

AbstractSnO2 hollow microspheres are controllably synthesized with the assistance of sulfonated polystyrene (sPS) colloidal spheres as hard templates. Via the interaction between ions of Sn2+ from the precursor SnSO4 which are in ethanol–aqueous medium and -SO3H ions on the template surface, sPS spheres-SnO2 precursor (sPS@SnO2) core–shell composite microspheres are prepared through a one-step hydrothermal method. The hollow SnO2 microspheres can be obtained after removal of the sPS microspheres by calcination in air. Furthermore, SnO2@C composite hollow spheres were fabricated with the further carbonization of the sPS@SnO2@glucose composite microspheres. By scanning electron microscopy, transmission electron microscopy, and BET measurements; the morphology, specific surface area, and the core–shell structure were investigated. Application for hollow and composite spheres in sewage treatment of dye solution was evaluated. SnO2 hollow spheres and SnO2@C composite hollow spheres are adsorbent materials whic...