Duoliang Shan

A new electrochemical sensor of nitro aromatic compound based on three-dimensional porous Pt–Pd nanoparticles supported by graphene–multiwalled carbon nanotube composite

In this study, an electrochemical sensor of nitro aromatic compound based on three-dimensional porous Pt-Pd nanoparticles (Pt-Pd NPs) supported by reduced graphene oxide (rGO) nanosheets-multiwalled carbon nanotube (CNTs) nanocomposite (marked as Pt-Pd NPs/CNTs-rGO) was investigated for the first time. This hybrid nanocomposite has been prepared via a facile and versatile hydrothermal synthetic strategy while its structure and property are evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). The result shows that 3D porous Pt-Pd NPs/CNTs-rGO nanocomposite has a large specific surface area of 326.6m(2)g(-1) and exhibited ultrahigh rate capability and good cycling properties at high rates. Electrochemical studies have been performed for the nitro aromatic compounds detection by using different pulse voltammetry (DPV) techniques. The proposed nanocomposite exhibited much enhanced elctrocatalytic activity and high sensitivity toward the detection of nitro aromatic compounds which compared with Pt-Pd NPs dispersed on functionalized rGO, Pt-Pd NPs dispersed on functionalized CNTs, rGO-CNTs and bare glass carbon electrode (GCE). On the basis of the above synergetic electrochemical sensing and synthesis procedure, the hybrid material can be recommended as a robust material for sensor-related applications. Moreover, the proposed sensor exhibits high reproducibility, long-time storage stability and satisfactory anti-interference ability.

Fe2PO5-Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe2 O3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm-2 ), a maximal photocurrent of 1.0 mA cm-2 is achieved with ZnO/Fe2 O3 core-shell NWs and 2.3 mA cm-2 was achieved for the PH3 -treated NWs at 1.23 V versus RHE. The PH3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe2 PO5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material.

Comparative study on the interfacial electron transfer of zinc porphyrins with meso-π-extension at a 2(n) pattern.

Three zinc-tetraarylporphyrins were prepared in order to investigate the effects of systematic meso-π-extension on the redox behaviors and interfacial electron transfer kinetics. The meso-π-extension increased at a 2(n) pattern, where 2(n) was the benzene ring number in an aryl group and the aryl group represented phenyl, naphthyl and pyrenyl group, respectively. The structures of zinc-tetraarylporphyrins and hydroquinone were optimized by using density functional theory. The bimolecular reactions between zinc-tetraarylporphyrins and hydroquinone at the liquid-liquid interface were studied by using scanning electrochemical microscopy. There was an inverse electron transfer rate-overall driving force dependence by comparison of three bimolecular reactions. It was suggested that the formation of a precursor between zinc-tetraarylporphyrin cation and hydroquinone was deeply influenced by the increasing steric hindrance from phenyl group to pyrenyl group. The electron transfer rate constant depended strongly on the overall driving force for each bimolecular reaction, with transfer coefficients of 0.41, 0.37 and 0.39.

Self-supported rectangular CoP nanosheet arrays grown on a carbon cloth as an efficient electrocatalyst for the hydrogen evolution reaction over a variety of pH values

Recent research suggests that transition metal phosphides (TMPs) are one of the most promising nobel-metal-free electrocatalysts for catalyzing the hydrogen evolution reaction. In this study, we report rectangular CoP nanosheet (NS) arrays on carbon cloth (CoP NS/CC) via a concise two-step synthetic method. The 3D rectangular CoP NS/CC with a three-dimensional porous and self-supported structure was fabricated via a hydrothermal method, followed by a low-temperature phosphidation treatment. Such 3D rectangular CoP NS/CC, as an HER electrocatalyst in acidic solution, exhibited high activity, good stability, and nearly 100% Faradaic efficiency (FE). The electrocatalyst requires an overpotential of 92, 112 and 195 mV to achieve current densities of 10, 20 and 100 mA cm−2, respectively, and maintain its catalytic stability for more than 50 h. In addition, the electrocatalyst works well in a neutral environment.

Cathodic electrochemiluminescence of a CdSe/ZnS QDs-modified glassy carbon electrode and its application in sensing of Pb2+

This paper reports the electrochemiluminescence (ECL) behavior of CdSe/ZnS with K2S2O8 as the coreactant. The effects of pH, K2S2O8 concentration, the duration of the reaction of 4-ATP with GCE and the duration of the reaction of 4-ATP/GCE with QDs on ECL intensity were studied in detail. A possible ECL reaction mechanism was then proposed. In addition, it was observed that the ECL intensity was efficiently quenched by trace amounts of heavy metal ion. Based on the quenching effect of Pb2+ upon the ECL of CdSe/ZnS QDs, a QDs-ECL sensor was constructed to detect Pb2+ in preserved duck egg. The sensor showed good reproducibility and stability.

Encapsulation of Dual‐Emitting Fluorescent Magnetic Nanoprobe in Metal‐Organic Frameworks for Ultrasensitive Ratiometric Detection of Cu2+

An effective dual-emission fluorescent metal-organic framework (MOF)-based nanoprobe has been established for ultrasensitive and rapid ratiometric detection of Cu2+ . Such a nanoprobe was prepared by encapsulating fluorescein isothiocyanate (FITC), and Eu(III) complex-functionalized Fe3 O4 into the zeolitic imidazolate framework material (ZIF-8). In this nanoprobe, FITC was used as a reference signal, thus improving the influence of external uncertainties. The Eu-complex signal could be quenched after adding an amount of Cu2+ . The ZIF-8 could enrich the target analytes, which can amplify the fluorescence signal due to the good adsorption properties of the ZIF-8. Based on above structural and compositional features, the detection limit of the nanoprobe is 0.1 nm for Cu2+ , almost 2×104 times lower than the maximum allowable amount of Cu2+ in drinking water, which constructed a platform for effective detection of Cu2+ . Using the nanoprobe to detect Cu2+ in aqueous solution is rapid and the probe still remained stable. Additionally, this sensor for the ratiometric fluorescence imaging of copper ions was also certified in real samples and live cells.

Investigation of proton-driven amine functionalized tube array as ion responsive biomimetic nanochannels

A simple amine embellished tube array was assembled at the liquid–liquid interface to study ion transfer behavior. Variation in the pH of the solution resulted in three different protonation states at the amino groups of the nanochannel, which in turn regulated ion transport, similar to the switching effect of ion channels in vivo.

Preparation of GO-COOH/AuNPs/ZnAPTPP nanocomposites based on the π–π conjugation: Efficient interface for low-potential photoelectrochemical sensing of 4-nitrophenol

The GO-COOH/AuNPs/ZnAPTPP nanocomposites were constructed using zinc monoamino porphyrin (ZnAPTPP) through π-π conjugation with carboxylated graphene oxide (GO-COOH) loaded with Au nanoparticles (AuNPs). Prepared materials were characterized by 1H NMR spectra, UV-vis absorption spectroscopy and electrochemical impedance spectroscopy. ITO electrode surface was modified with the prepared nanocomposites showed a good photocurrent response when the bias potential, -0.1V was applied. Nanocomposites modified ITO electrode exhibited good photo-response to the 4-nitrophenol (4-NP). ZnAPTPP were excited from HOMO to LUMO under light irradiation, the photoexcited electrons injected into the conduction band of GO-COOH, and then transferred to AuNPs further to the ITO. The presence of GO-COOH and AuNPs improved the separation of photogenerated charges due to their synergetic effect and excellent conductivity. Externally added 4-NP scavenges the photogenerated holes i.e. it acts as a sacrificial electron donor thereby it enhances the photocurrent of the system. Based on this interaction, a novel method for photoelectrochemical detection of 4-NP was developed with a linear range from 0.1 to 15nmol/L (r = 0.996) and detection limit of 0.04nmol/L (S/N = 3). Proposed method is simple and sensitive and this was successfully applied for the quantification 4-NP in river water sample matrices.

A simple yet sensitive colorimetric nitrite ions assay based on diazotization with p‑Aminobenzoic and coupling with phloroglucinol in acidic medium

Immoderate intake of nitrite (NO2-) is deleterious human health and may result in causing dangerous diseases. In this study, nitrite detection system was successfully fabricated based on a unique diazo-coupling reaction of p‑Aminobenzoic acid (PABA) and phloroglucinol (1, 3, 5‑trihydroxybenzene). Upon the presence of NO2- in an acid medium, p‑Aminobenzoic acid could not only form diazonium ion easily but also couple with p‑Aminobenzoic acid, and results forming yellow water-soluble azo dye that shows maximum absorption at 434 nm. Under the further accurate determination condition, such as acid concentration, amount of reagents and time required, the naked-eye detection of NO2- showed excellent selectivity in compared with some anions. Especially, diazotization and coupling reaction proposed here is very fast and control of pH and temperature are unnecessary. Moreover, the color is stable for several days and Beers law is obeyed over a wide range. Reliable detection can be made in the range of 0.05 to 1 p.p.m. of nitrite ion. Detection limit was calculated to be 0.024 p.p.m. (0.52 μ M) by UV-visible spectroscopy and 0.05 p.p.m. (1.09 μ M) by naked-eye. By using an electrochemical method, IR, SEM, and 1HNMR, the sensing mechanism can be easily verified. More importantly the proposed method was successfully applied for the determination of nitrite in a real water sample.

Three-dimensional porous self-assembled chestnut-like nickel-cobalt oxide structure as an electrochemical sensor for sensitive detection of hydrazine in water samples

Three-dimensional NiCo2O4 is a kind of superior sensing material owing to its high electron transfer capability, large available surface area and numbers of active sites. In this work, NiCo2O4 of the three-dimensional chestnut-like structure were easily achieved through a one step hydrothermal process. Afterwards, the morphology and structure were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Based on the three-dimensional porous chestnut-like NiCo2O4, an electrochemical sensor for hydrazine (N2H4) detection is fabricated. This electrochemical platform can realize good selectivity, excellent stability, high sensitivity (∼2154.4 μA mM-1 cm-2), and low detection limit (0.3 μM), as well as a wide linear range from 1 μM to 1096 μM. The synergistic effect of nickel-cobalt in such mixed transition metal oxides which Co in Co3O4 is partially replaced by Ni are beneficial for enhancing sensing properties. This study proves that three-dimensional porous chestnut-like NiCo2O4 is electrochemically active for catalytic performance which is particular and promising material for good application in the practical detection of N2H4.