Shanli Yang

Supersensitive Detection of Chlorinated Phenols by Multiple Amplification Electrochemiluminescence Sensing Based on Carbon Quantum Dots/Graphene

A novel electrochemiluminescence (ECL) sensor based on carbon quantum dots (CQDs) immobilized on graphene (GR) has been first developed for the determination of chlorinated phenols (CPs) in water. The detection is based on the ECL signals from the interaction between the analytes and the excited CQDs (C(*+)) using S2O8(2-) as coreactant. GR facilitates both C(•-) and SO4(•-) production, resulting in a high yield of C(*+), and the multistage amplification effect leads to a nearly 48-fold ECL amplification. Pentachlorophenol (PCP) is often monitored as an important indicator for CPs in real environmental samples, but its ultratrace and real-time analysis is an intractable issue in environmental monitoring. The resulting ECL sensor enables the real-time detection of PCP with unprecedented sensitivity reaching 1.0 × 10(-12) M concentration in a wide linear range from 1.0 × 10(-12) to 1.0 × 10(-8) M. The ECL sensor showed high selectivity to CPs, especially to PCP. The practicability of the sensing platform in real water samples showed ideal recovery rates. It is envisaged that the eco-friendly and recyclable sensor could be employed in the identification of key CPs in the environment.

Electrochemical detection of 4-nitrophenol based on a glassy carbon electrode modified with a reduced graphene oxide/Au nanoparticle composite

A new electrochemical sensor for 4-nitrophenol (4-NP) detection based on the reduced graphene oxide (RGO) and Au nanoparticle composite was developed. The RGO film was first electrodeposited onto a glassy carbon electrode (GCE). Then Au nanoparticles (AuNPs) were electrochemically deposited onto the RGO film. The morphology and electrochemical properties of the AuNP/RGO composite were investigated. The synergic effect of AuNPs and RGO nanosheets as co-modifiers greatly facilitates electron-transfer processes between the electrolyte and the GCE, and thus leads to a remarkably improved sensitivity for 4-NP detection. Two detection modes, differential pulse voltammetry (DPV) and square wave voltammetry (SWV), were applied. A wide linear range of values, 0.05–2.0 μM and 4.0–100 μM for DPV and 0.05–2.0 μM for SWV, were obtained. The limit of detection (LOD) of 4-NP was 0.01 μM and 0.02 μM for DPV and SWV, respectively. This sensor was successfully used in the detection of real water samples from Xiangjiang River.

A third-generation hydrogen peroxide biosensor based on horseradish peroxidase immobilized on DNA functionalized carbon nanotubes

In this paper, DNA functionalized SWCNTs were used to immobilize horseradish peroxidase (HRP) on glassy carbon (GC) electrode. Cyclic voltammetry showed that the direct electrochemistry of HRP immobilized on DNA-SWCNTs hybrids was achieved. The DNA interlayer between the SWCNTs and HRP could be used to keep the activity of HRP. Compared with HRP-SWCNTs/GC and HRP-DNA/GC electrodes, the prepared HRP-DNA-SWCNTs/GC electrode exhibited more excellent electrochemical properties. Thus, the prepared HRP-DNA-SWCNTs/GC electrode was proposed as a third-generation H(2)O(2) biosensor. The effect of pH and applied potential on the performance of the biosensor was discussed in detail. Under the optimal conditions, a wide linear range of the propose biosensor for the detection of H(2)O(2) was observed from 6.0x10(-7) to 1.8 x10(-3)M. The detection limit was found to be 3.0 x10(-7)M at a signal-to-noise ratio of 3. Furthermore, the proposed biosensor displayed rapid response, high stability, very good reproducibility and high sensitivity for the detection of H(2)O(2). Determination H(2)O(2) concentration in disinfector sample by the proposed biosensor also showed satisfactory result.

Direct synthesis of graphene-chitosan composite and its application as an enzymeless methyl parathion sensor.

This paper proposed a direct electrodeposition approach to synthesis of graphene-chitosan (GR-CS) composite onto glassy carbon electrode (GCE) under controlled potential. This direct electrodeposition approach for the construction of GR-based hybrid was environmentally friendly, which would not involve the chemical reduction of graphene oxide (GO) and therefore result in no further contamination. The whole procedure was simply and cost only several minutes. Moreover, Combining the advantages of GR (large surface-to-volume ratio and high conductivity) and CS (good biocompatibility and adsorption), the GR-CS composite could be highly efficient to capture OPs and used as solid phase extraction (SPE). The GR-CS/GCE was used to detect organophosphate pesticides (OPs), using methyl parathion (MP) as a model analyte. The significantly redox response of MP on the GR-CS/GCE was proved. The linear range was wide from 4.0 ng mL(-1) to 400 ng mL(-1), and a low detection limit of 0.8 ng mL(-1) for MP was achieved. Moreover, the proposed sensor exhibited high reproducibility, long-time storage stability and satisfactory anti-interference ability. The proposed GR-CS/GCE opens new opportunity for green, fast, simple, and sensitive analysis of OP compounds.

Simple, rapid and green one-step strategy to synthesis of graphene/carbon nanotubes/chitosan hybrid as solid-phase extraction for square-wave voltammetric detection of methyl parathion

Simple, rapid, green and one-step electrodeposition strategy was first proposed to synthesis of graphene/carbon nanotubes/chitosan (GR/CNTs/CS) hybrid. The one-step electrodeposition approach for the construction of GR-based hybrid is green environmentally, which would not involve the chemical reduction of graphene oxide (GO) and therefore result in no further contamination. The whole procedure is simple and needs only several minutes. Combining the advantages of GR (large surface area, high conductivity and good adsorption ability), CNTs (high surface area, high enrichment capability and good adsorption ability) and CS (good adsorption and excellent film-forming ability), the obtained GR/CNTs/CS composite could be highly efficient to capture organophosphate pesticides (OPs) and used as solid phase extraction (SPE). The GR/CNTs/CS sensor is used for enzymeless detection of OPs, using methyl parathion (MP) as a model analyte. Significant redox response of MP on GR/CNTs/CS sensor is proved. The linear range is wide from 2.0ngmL(-1) to 500ngmL(-1), with a detection limit of 0.5ngmL(-1). Detection limit of the proposed sensor is much lower than those enzyme-based sensors and many other enzymeless sensors. Moreover, the proposed sensor exhibits high reproducibility, long-time storage stability and satisfactory anti-interference ability. This work provides a green and one-step route for the preparation of GR-based hybrid, and also offers a new promising protocol for OPs analysis.

Fabrication of DNA functionalized carbon nanotubes/Cu2+ complex by one-step electrodeposition and its sensitive determination of nitrite

In this paper, DNA functionalized single-wall carbon nanotubes/Cu(2+) (DNA-CNTs/Cu(2+)) complex was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a DNA-CNTs/Cu(2+)/GCE sensor to detect nitrite. Cyclic voltammogram of DNA-CNTs/Cu(2+)/GCE showed a pair of well-defined redox peaks for Cu(2+)/Cu(+). Compared with DNA-CNTs/GCE and DNA-Cu(2+)/GCE, the prepared DNA-CNTs/Cu(2+)/GCE exhibited more excellent electrochemical properties. Thus, the prepared DNA-CNTs/Cu(2+)/GCE was proposed as nitrite sensor. The effects of Cu(2+), CNTs and DNA concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of DNA-CNTs/Cu(2+)/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO(2)(-)). The linear range for the detection of NO(2)(-) was 3x10(-8) to 2.6x10(-3)M, and the response was very fast (less than 3s). A low detection limit of 3x10(-8)M (S/N=3) for NO(2)(-) was achieved.

Ultrasensitive electrochemiluminescent detection of pentachlorophenol using a multiple amplification strategy based on a hybrid material made from quantum dots, graphene, and carbon nanotubes

AbstractWe report on a highly sensitive and selective electrochemiluminescence (ECL) based method for the determination of pentachlorophenol (PCP). It is based on a new hybrid material composed of CdS quantum dots (QDs), graphene, and carbon nanotubes (CNTs), and uses peroxodisulfate as the coreactant. The use of this system results in a nearly 18-fold increase in ECL intensity. On interaction between PCP and the QDs, a decrease in ECL intensity is observed at PCP in a concentration as low as 1.0 pM and over a wide linear range (from 1.0 pM to 1.0 nM). The method is hardly affected by other chlorophenols and nitrophenols, and the electrode can be recycled. Figureᅟ