Guojuan Ren

Fabrication of Fe3O4@Au hollow spheres with recyclable and efficient catalytic properties

The preparation of catalysts with superior catalytic activity, reusability and economical processes is highly desirable. In this work, we report a route for the facile synthesis of Fe3O4@Au hollow spheres. The Fe3O4@Au hollow spheres were prepared based on Fe3O4 hollow spheres with gold nanoparticles inlaid on their surface. The Fe3O4@Au hollow nanospheres were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX). The Fe3O4@Au hollow spheres exhibit remarkable catalytic activity and good reusability toward the reduction of 4-nitrophenol and potassium hexacyanoferrate(III) by NaBH4 in water. In addition, the catalysts show good reusability for at least 6 successive cycles.

Morphology tuning of assembled Au–Cu nicotinate rings by ligand coordination and their use as efficient catalysts

In this work, cyclic annular Au–Cu nicotinates were synthesized through a facile one-pot method. Cupric nitrate trihydrate, hydrogen tetrachloroaurate and nicotinic acid were used as the initial reactants; nicotinic acid was found to be an excellent ligand. The Au–Cu nicotinate annularity rings were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Specifically, the shape of the assembled Au–Cu nicotinate rings can be readily controlled by changing the ratio of the reactants and the reaction time. The mechanism of growth of the Au–Cu nicotinate annular rings was also investigated; the results of the experiments indicate that the Au–Cu nicotinate annular rings were assembled from ultrathin nanosheets. The Au–Cu nicotinate rings exhibit excellent catalytic activity toward the reduction of nitrophenols (including 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and 4-nitrothiophenol) by sodium borohydride in water. Experimentally, the optimized ratio of the components was found to be Au : Cu : nicotinate close to 1 : 4 : 1. Kinetic rate investigations were carried out for the Au–Cu NRs-catalyzed reactions at different cycles. Importantly for their use as catalysts, the Au–Cu nicotinate rings can be recycled and exhibit good reusability. These results indicate that Au–Cu nicotinate rings are an effective catalyst for environmental wastewater treatment.

Fabrication of magnetic bimetallic Fe3O4@Au–Pd hybrid nanoparticles with recyclable and efficient catalytic properties

Bimetallic nanostructures show exciting potential as materials for effective catalysis. Magnetically recoverable bimetallic nanoparticles are promising catalysts for chemical reactions. Here, Fe3O4@Pd and Fe3O4@Au–Pd hybrid nanoparticles were synthesized and used as catalysts. The morphology, composition, and structure of the Fe3O4@Pd and Fe3O4@Au–Pd hybrid nanoparticles were fully characterized by scanning and transmission electron microscopy, energy dispersive spectroscopy, high angle annular dark-field scanning TEM, X-ray powder diffraction, X-ray photoelectron spectroscopy, etc. The Fe3O4@Pd and Fe3O4@Au–Pd nanoparticles show excellent catalytic activity towards the reduction of nitrophenols and potassium hexacyanoferrate(III). In addition, the magnetic bimetallic heterogeneous nanoparticles can be easily recycled, showing good reusability; conversion higher than 99% was achieved after 6 cycles.

Shape-controlled synthesis of 3D copper nicotinate hollow microstructures and their catalytic properties

A series of three-dimensional (3D) copper nicotinate hollow microstructures were fabricated by a one step method. The shape of the copper nicotinate hollow microstructures evolved from a hexagon, to an octagon and to a tetragonum, depending on the setting time and concentrations of the reactants. The 3D copper nicotinate hollow microstructures were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) and scanning electron microscopy (SEM). The mechanism of the growth of the copper nicotinate hollow microstructures has also been investigated, which indicated that 3D copper nicotinate hollow microstructures were assembled by ultrathin copper nicotinate nano-sheets. The catalytic activities of the as-obtained copper nicotinate hollow microstructures for the reduction of 4-nitrophenol by sodium borohydride were examined. The catalytic activity of copper nicotinate hollow microstructures was greatly improved due to the hollow structure.

Orange emissive carbon dots for colorimetric and fluorescent sensing of 2,4,6-trinitrophenol by fluorescence conversion

In this study, infrequent orange carbon nanodots (CNDs) were applied as a dual-readout probe for the effective colorimetric and fluorescent detection of 2,4,6-trinitrophenol (TNP). The orange fluorescence could be rapidly and selectively quenched by TNP, and the colorimetric response from the original pink color to blue could also be captured immediately by the naked eye. A limit of detection of 0.127 μM for TNP was estimated by the fluorescent method and 5 × 10−5 M by visualized detection. Interestingly, the fluorescence of the CNDs with TNP gradually transitioned from orange to green upon irradiation by a UV lamp, and the colorimetric response transitioned from pink to blue to colorless, which ensured effective multi-response detection of TNP. In addition, the CNDs exhibited bright fluorescence, excellent biocompatibility and low toxicity, making them high-quality fluorescent probes for cellular imaging.

Nitrogen-doped carbon dots for the detection of mercury ions in living cells and visualization of latent fingerprints

Nitrogen-doped carbon dots (NCDs) were synthesised using a simple and straightforward solvothermal method. The resulting spherical NCDs showed stable fluorescence and a prominent fluorescence quantum yield (67%) with an average size of 3.52 nm. The fluorescence of the NCDs was quenched effectively by mercury ions (Hg2+), exhibiting a detection limit of 0.65 μM. Upon addition of a saturated solution of ethylenediaminetetraacetic acid to a dispersion of the NCDs/Hg2+ complex, the fluorescence of the NCDs underwent significant immediate recovery. Due to their favorable biocompatibility, NCDs were also demonstrated to be efficient for HeLa cell imaging. The detection of Hg2+ by NCDs could be realized in environmental water samples and living cells, with excellent results. Moreover, the as-synthesized fluorescent NCD nanopowders were used for visualizating latent fingerprints (LFPs) with significant third level detail.