Zhaoxia Shi

Simple and novel electrochemical sensor for the determination of tetracycline based on iron/zinc cations-exchanged montmorillonite catalyst.

A simple and novel electrochemical sensor for the determination of tetracycline (TC), a kind of antibiotic that may induce residue in the food chain, was developed by the modification of iron/zinc cation-exchanged montmorillonite (Fe/Zn-MMT) catalyst on glassy carbon electrode (GCE). The morphology and the structure of the Fe/Zn-MMT nanomaterial were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results of electrochemical experiments demonstrated that the sensor exhibited excellent electrocatalytic activity to the oxidation of TC in the presence of sodium dodecyl sulfate. The sensor displayed a wide linear range from 0.30 to 52.0 μM and a low detection limit of 0.10 μM by using the derivative differential pulse voltammetry. Moreover, the electrochemical sensor was applied to the detection of TC in feedstuff and meat samples.

Preparation of graphene oxide-wrapped carbon sphere@silver spheres for high performance chlorinated phenols sensor.

A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment. The CS@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity, which was further mechanically protected by graphene oxide (GO) nanolayers to fabricate intriguing configuration, which was beneficial for efficiently preventing the aggregation and oxidation of AgNPs and improving the electrical conductivity through intimate contact. By immobilizing this special material on electrode surface, the CS@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The tailored structure, fast electron transfer ability and facile preparation of CS@Ag@GO made it a promising electrode material for practical applications in phenols sensing.

A novel sensing platform based on a core–shell Fe@Fe3C–C nanocomposite for ultrasensitive determination of vanillin

A simple, rapid and ultrasensitive electrochemical sensing platform has been successfully constructed for vanillin determination. The core–shell structured Fe@Fe3C–C nanocomposite, prepared by adopting α-FeOOH nanorods as the Fe precursor, glucose as the reducing agent and carbon source, urea as the chelating and dispersing agent, and LiFePO4 as an intermediate and/or catalyst, was used for vanillin determination for the first time, and exhibited high sensitivity and good reproducibility. A wide linear range from 10.0 nM to 50.0 μM with a good linear correlation (R = 0.994) was obtained, and the limit of detection was 2.36 nM (S/N = 3). In addition, the practical analytical application of the sensing method was assessed by determination of vanillin in real food samples with satisfactory results. Armed with the remarkable advantages, such as a green route to fabricate, low cost and fast response time, the novel method may hold great potential for the monitoring of abusive vanillin in foods.

Determination of Oxytetracycline in Food Using a Disposable Montmorillonite and Acetylene Black Modified Microelectrode

Oxytetracycline is a broad-spectrum antibiotic used in animal husbandry that may cause the occurrence of antibiotic residues in food-producing animals. A detailed study of the electrochemical properties of oxytetracycline was carried out at montmorillonite and acetylene black modified carbon paste microelectrode. The oxytetracycline underwent an irreversible oxidation at montmorillonite-acetylene black/carbon paste microelectrode, which was an adsorption-controlled process with one proton and one electron. Using differential normal pulse voltammetry with accumulation at a fixed potential of 0.3 V for 120 s, oxytetracycline yielded a well-defined voltammetric response at 0.6 V in pH 7.4 citric acid–Na2HPO4 buffer. Furthermore, the oxidation peak current of oxytetracycline at the montmorillonite–acetylene black/carbon paste microelectrode linearly increased with concentration in the range of 0.5–50 µM with a low detection limit of 87 nM (S/N = 3). This methodology was successfully applied to the determination of oxytetracycline from food samples, suggesting that it has practical applications in monitoring oxytetracycline.

Facile synthesis of monodisperse Ag@C@Ag core–double shell spheres for application in the simultaneous sensing of thymol and phenol

A simple coupled synthesis and encapsulation route was developed to fabricate monodisperse, uniform Ag@C@Ag core–shell structured nanocomposites with excellent electrochemical and catalytic properties, in which Ag nanoparticles were first encapsulated in a carbonaceous shell through the catalyzed dehydration of glucose under hydrothermal conditions, and then the surface-activated Ag@C spheres were subsequently used to accumulate [Ag(NH3)2]+ or Ag+ ions through electrostatic attraction to anchor the Ag coating. The as-prepared nanocomposites were demonstrated to have a great potential for the simultaneous multiplexed detection of thymol and phenol, and exhibited high sensitivity and good reproducibility. In addition, the practical analytical application of the sensing platform was assessed by the determination of thymol and phenol in real honey samples, and satisfactory results were achieved.

Preparation of yolk–shell structured copper oxide@silica oxide spheres and their application in high performance electrochemical sensing of Formoterol fumarate residues in swine feed and tissues

In this paper, we report a facile route to synthesize yolk-shell structured copper oxide@silica oxide (CuO@SiO2) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030-10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues.

Synthesis and Characterization of Mesoporous Tin Oxide-Functionalized Reduced Graphene Oxide Nanoplatelets for Ultrasensitive Detection of Guaiacol in Red Wines

This work describes for the first time the use of mesoporous tin oxide-functionalized reduced graphene oxide (SnO2-rGO) as electrode modifier in combination with differential pulse voltammetry techniques for preconcentration and detection of guaiacol in red wine samples. SnO2-rGO was prepared through in situ growth of SnO2 particles on the rGO surface using cetyltrimethylammonium bromide as the structure-directing agent. Using the best set of experimental conditions, a linear response for guaiacol in the concentration range of 0.05 to 60 μM with a limit of detection of 7.2 nM (signal-to-noise ratio = 3) was obtained. Finally, the method was successfully applied to determine guaiacol in red wine samples, and the contents closely corresponded to those obtained by the reported chromatographic method.

Preparation of Reduced Graphene Oxide–Poly(Safranine T) Film via One-Step Polymerization for Electrochemical Determination of Methyl Jasmonate

In this work, a new reduced graphene oxide–poly(safranine T) (rGO–PST) film was prepared on glassy carbon electrode (GCE) via one-step polymerization using rGO as an electron transfer mediator. The uniform structure of rGO–PST film was exhibited by scanning electron microscopy. Electrochemical characterization indicated that rGO–PST/GCE possessed much larger surface area and faster electron transfer rate constant compared with GCE. Furthermore, the rGO–PST/GCE exhibited strong catalytic ability and sensitive response to the oxidation of methyl jasmonate (MeJA) using derivative linear scan voltammetry. Under optimal working conditions, the oxidation current of MeJA linearly increased with its concentration in the range of 1.0–10 μM and 30–3000 μM after 2-min accumulation, along with a low detection limit of 0.5 μM. As an example of practical application, the rGO–PST/GCE was successfully employed for the determination of MeJA in jasmine essential oil and rice spikelets samples.

Graphene oxide reinforced core−shell structured Ag@Cu 2 O with tunable hierarchical morphologies and their morphology−dependent electrocatalytic properties for bio−sensing applications

In this study, a facile solution approach was developed for the synthesis of a series of core-shell structured Ag@Cu2O nanocrystals of various shapes including triangles, spheres, and cubes with well-defined stable heterojunctions. The electrooxidation of dopamine (DA), uric acid (UA), guanine (G), and adenine (A) using these hybrids revealed morphology-dependent sensing properties, with activities and accumulation ability following the order, triangular Ag@Cu2O > spherical Ag@Cu2O > cubic Ag@Cu2O. Further, we constructed a novel graphene oxide (GO) nanosheet-reinforced triangular Ag@Cu2O ternary hetero-nanostructure. Such a hybrid with a three-dimensional interconnected hierarchical architecture is suitable for catalysis, since it not only leads to improved interfacial electron transfer, but also readily exposes the highly catalytic Ag@Cu2O to the reactants. Therefore, more enhanced electrochemical activities were observed for the oxidation of DA, UA, G, and A. This study provides an efficient way to synthesize morphology-controlled Ag@Cu2O heterogeneous catalysts for the fabrication of potential biosensors, and also opens up attractive avenues in the design of multifunctional ternary noble metal-semiconductor-carbon hybrids.