Fang Chai

L-cysteine functionalized gold nanoparticles for the colorimetric detection of Hg2+ induced by ultraviolet light

A simple, cost-effective yet rapid and sensitive colorimetric sensor for the detection of Hg(2+) using L-cysteine functionalized gold nanoparticles induced by ultraviolet radiation was developed. The sensitivity and selectivity of detection was also investigated. The L-cysteine modified gold nanoparticles can be induced to aggregate quickly in the presence of Hg(2+), especially with the assistance of ultraviolet radiation. The presence of Hg(2+) can be monitored by the colorimetric response of gold nanoparticles. The detection of Hg(2+) could be realized, after measuring the UV-vis spectra, with a detection limit of 100 nM. The selectivity of this method has been investigated by other divalent metal ions. The effective colorimetric sensor can be used for on-site and real-time Hg(2+) detection.

Fluorescent detection of TNT and 4-nitrophenol by BSA Au nanoclusters

Rapid and sensitive detection of 2,4,6-trinitrotoluene (TNT) and 4-nitrophenol (4-NP) has attracted considerable attention due to their wide applications as nitroaromatic explosive materials. A novel fluorescence method for TNT and 4-NP based on bovine serum albumin functionalized fluorescent gold nanoclusters (BSA Au-NCs) has been developed. The detection probe BSA Au-NCs can be used as a fluorescent probe for the sensitive and selective detection of TNT and 4-NP simultaneously. A good linearity of fluorescence detection using BSA Au-NCs as a fluorescent probe was observed for TNT and 4-NP concentrations in the range of 10(-8)-5 × 10(-5) M and 10(-9)-5 × 10(-5) M, with a detection limit of 10 nM and 1 nM, respectively. The high specificity of TNT and 4-NP with BSA Au-NCs interactions provided excellent selectivity towards detecting TNT and 4-NP over other relevant nitroaromatic compounds. This system can be applied to test strips to detect TNT and 4-NP with high sensitivity and selectivity. The vapour of TNT and 4-NP can be detected using BSA Au-NCs test paper within 1 min with a detection limit of 10 pM and 1 pM.

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.

Colorimetric detection of Hg2+ using thioctic acid functionalized gold nanoparticles

This paper describes the sensing application of water-dispersible thioctic acid functionalized gold nanoparticles (TA-GNPs) as sensors for the colorimetric detection of Hg2+ ion in water samples. The state and stability of thioctic acid decorated gold nanoparticles in pH range (pH = 4–11) were evaluated by UV/vis spectra. The thioctic acid modified GNPs could be induced to aggregate quickly in the presence of Hg2+, especially after adding a solution of 0.05 M NaCl. The detection of Hg2+ by TA-GNPs at different pH values (pH = 5, 7, 9, 11) was also investigated to optimize the experimental conditions in detail. The result indicated that the TA-GNPs at pH 5 were the most optimal choice for detecting Hg2+. The detection results of Hg2+ could be determined by the naked eye or a UV-vis spectrophotometer. The detection of Hg2+ could be realized with a detection limit of 10 nM over a long range (10 nM to 20 μM). Additionally, the selectivity of this method has been investigated using other metal ions. The TA-GNPs can selectively bind Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Ag+ and Cr3+), leading to prominent color change. This will provide a simple and effective colorimetric sensor (no DNA) for on-site and real-time Hg2+ ion detection. More importantly, this probe was also applied to determine the Hg2+ in lake samples, and the results demonstrate low interference and high sensitivity.

Flowerlike γ-Fe2O3@NiO hierarchical core-shell nanostructures as superb capability and magnetically separable adsorbents for water treatment

Sorption is thought to be a versatile and effective approach for the removal of water pollutants and has been widely used in water purification. In this work, we have synthesized flowerlike γ-Fe2O3@NiO core-shell hierarchical nanostructures though a facile method. The NiO shell can be easily controlled by altering the concentration of the nickel source. The obtained flowerlike γ-Fe2O3@NiO core-shell hierarchical nanostructures exhibit superb adsorption capability as adsorbents for the removal of toxic pollutants from waste water. Importantly, the flowerlike γ-Fe2O3@NiO core-shell hierarchical nanostructures still retained this adsorption activity even after being recycled three times with the help of an external magnetic field. Furthermore, the magnetic flowerlike γ-Fe2O3@NiO core-shell hierarchical nanostructures may have potential practical use in catalysis, lithium-ion batteries, supercapacitors and so on.

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.

Fabrication of Core-Shell Structural SiO2@H3[PM12O40] Material and Its Catalytic Activity

Through a natural tree grain template and sol-gel technology, the heterogeneous catalytic materials based on polyoxometalate compounds H3[PM12O40] encapsulating SiO2: SiO2@H3[PM12O40] (SiO2@PM12, M = W, Mo) with core-shell structure had been prepared. The structure and morphology of the core-shell microspheres were characterized by the XRD, IR spectroscopy, UV-Vis absorbance, and SEM. These microsphere materials can be used as heterogeneous catalysts with high activity and stability for catalytic wet air oxidation of pollutant dyes safranine T (ST) at room condition. The results show that the catalysts have excellent catalytic activity in treatment of wastewater containing 10 mg/L ST, and 94% of color can be removed within 60 min. Under different cycling runs, it is shown that the catalysts are stable under such operating conditions and the leaching tests show negligible leaching effect owing to the lesser dissolution.

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.