Yongping Dong

Electrogenerated Chemiluminescence Resonance Energy Transfer between Luminol and CdSe@ZnS Quantum Dots and Its Sensing Application in the Determination of Thrombin

In this work, electrogenerated chemiluminescence resonance energy transfer (ECL-RET) between luminol as a donor and CdSe@ZnS quantum dots (QDs) as an acceptor was reported in neutral conditions. It was observed that a glassy carbon electrode modified with CdSe@ZnS quantum dots (CdSe@ZnS/GCE) can catalyze the luminol oxidation to promote the anodic luminol ECL without coreactants. The intensity of anodic luminol ECL (0.60 V) at the CdSe@ZnS/GCE was enhanced more than 1 order of magnitude compared with that at the bare GCE. Another stronger anodic ECL peak observed at more positive potential (1.10 V) could be assigned to the ECL-RET between the excited state of luminol and the QDs. A label-free ECL aptasensor for the detection of thrombin was fabricated based on the synergic effect of the electrocatalysis and the ECL-RET. The approach showed high sensitivity, good selectivity, and wide linearity for the detection of thrombin in the range of 10 fM-100 pM with a detection limit of 1.4 fM (S/N = 3). The results suggested that the as-proposed luminol-QDs ECL biosensor will be promising in the detection of protein.

Electrogenerated Chemiluminescence Resonance Energy Transfer between Ru(bpy)32+ Electrogenerated Chemiluminescence and Gold Nanoparticles/Graphene Oxide Nanocomposites with Graphene Oxide as Coreactant and Its Sensing Application

In the present work, strong anodic electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) was observed at a graphene oxide modified glassy carbon electrode (GO/GCE) in the absence of coreactants. The electrocatalytical effect of GO on the oxidation of Ru(bpy)3(2+) suggested that GO itself can act as the coreactant of Ru(bpy)3(2+) ECL, which can be used to fabricate the ECL biosensor. Thiol group terminated adenosine triphosphate (ATP) aptamer was immobilized on the GO film via DNA hybridization. When gold nanoparticles/graphene oxide (AuNPs/GO) nanocomposites were modified on the aptamer through the S-Au bond to form a sandwich-like structure, the ECL resonance energy transfer (ECL-RET) could occur between Ru(bpy)3(2+) and AuNPs/GO nanocomposites, resulting in an apparent decrease of ECL signal. After the ECL sensor was incubated in ATP solution, the AuNPs/GO nanocomposites were released from the electrode due to the specific interaction between aptamer and ATP, leading to the increased ECL signal. On the basis of these results, an ECL aptasensor was fabricated and could be used in the sensitive and selective detection of ATP in the range of 0.02-200 pM with a detection limit of 6.7 fM (S/N = 3). The proposed ECL aptasensor can be applied in the detection of ATP in real samples with satisfactory results.

Electrochemiluminescent Sensing for Caspase-3 Activity Based on Ru(bpy)32+-Doped Silica Nanoprobe

Caspase-3 is one of the most frequently activated cysteine proteases during the apoptosis process and has been identified as a well-established cellular marker of apoptosis. In this study, a novel approach for the sensitive determination of caspase-3 activity was proposed using electrochemiluminescence (ECL) of Ru(bpy)3(2+)-doped silica (Ru@SiO2) with tripropylamine (TPA) as coreactant. A nanocomposite containing gold nanoparticles (AuNPs), poly(dimethyldiallyl ammonium chloride) (PDDA), and multiwalled carbon nanotubes (CNTs) was fabricated as an ECL platform. The biotinylated DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Gly-Cys) was immobilized on the nanocomposite surface via the strong bonding interaction between AuNPs and the thiol group. Then the streptavidin-modified Ru(bpy)3(2+)-doped silica (Ru@SiO2-SA) was immobilized on the ECL platform via the specific interaction between biotin and streptavidin to generate ECL signal. Caspase-3 can specifically recognize and cleave the N-terminus of DEVD, leading to the loss of the biotin label and the decrease of ECL intensity to determine the activity of caspase-3. The results revealed a new ECL avenue for the sensitive and specific monitor of caspase-3, and the platform could be utilized to evaluate anticancer drugs.

Speciation of Inorganic- and Methyl-Mercury in Biological Matrixes by Electrochemical Vapor Generation from an l-Cysteine Modified Graphite Electrode with Atomic Fluorescence Spectrometry Detection

A novel nonchromatographic speciation technique for ultratrace inorganic mercury (Hg(2+)) and methylmercury (CH(3)Hg(+)) in biological materials is developed and validated by electrolytic vapor generation (EVG) coupled with atomic fluorescence spectrometry (AFS). The studies show that CH(3)Hg(+) and Hg(2+) can be converted to Hg vapor efficiently on an l-cysteine modified graphite cathode, which has never been reported before. We observe that only Hg(2+) can be converted efficiently to Hg vapor at low current mode (0.2 A). While at high current mode (2.2 A), both CH(3)Hg(+) and Hg(2+) can be reduced efficiently. As a result, we successfully establish an exact and sensitive method based on the current control to detect mercury speciation for the first time. The factors of electrolytic conditions have been optimized, and the potential mechanism is discussed. Under the optimal conditions, the detection limits (3s) of Hg(2+) and CH(3)Hg(+) in aqueous solutions are 0.098 and 0.073 μg L(-1), respectively. The relative standard deviations for 6 replicate determinations of 2 μg L(-1) Hg are determined as 3.2% and 4.7% for Hg(2+) and CH(3)Hg(+). The accuracy of the method is verified through the analysis of certified reference materials (CRM, NRC-DORM-2), and the proposed method has been applied satisfactorily to the determination of mercury speciation in several seafood samples by calibration curve mode.

Electrogenerated chemiluminescence of quantum dots with lucigenin as coreactant for sensitive detection of catechol.

Electrogenerated chemiluminescence (ECL) of quantum dots (QDs), including CdS, CdSe, CdTe, and CdSe@ZnS QDs, was comparatively studied in neutral lucigenin solution without coreactants. Cathodic ECL signals were obtained at -1.2 V at different QDs modified gold electrodes (QDs/GEs) and the strongest ECL emission was obtained at the CdSe@ZnS QDs modified GE, which is nearly 7-times larger than other QDs modified GEs. The electrochemical results and the ECL spectrum revealed that the luminophor of the cathodic ECL is the excited state of QDs but not lucigenin, revealing that lucigenin can act as coreactant to generate cathodic ECL with QDs. Several impact factors, such as the amount of QDs, the supporting electrolytes, and the pH were investigated. Under the optimal condition, catechol exhibited apparent inhibiting effect on the cathodic ECL signal, based on which a new ECL sensor was developed and applied in the sensitive detection of catechol. The inhibited ECL intensity varied linearly with catechol concentration in the range of 5-1000 nM with a detection limit of 2 nM (S/N=3). The ECL sensor exhibited satisfied stability, repeatability, and selectivity. The mechanism of cathodic ECL was also proposed.

Electrogenerated chemiluminescence of Si quantum dots in neutral aqueous solution and its biosensing application

Electrogenerated chemiluminescence (ECL) of semiconductor quantum dots (QDs) has been considered as a powerful technique in the fabrication of biosensor, however, high-toxicity of heavy metal ion containing in QDs severely limits their further applications, and the search for the alternative benign nanomaterials with high ECL efficiency is urgent. Herein, ECL behavior of eco-friendly silicon quantum dots (SiQDs) was reported in neutral aqueous condition. Stable and intense cathodic ECL emission was obtained in phosphate buffer solution (PBS) with K2S2O8 as coreactant. ECL resonance energy transfer (ECL-RET) system was established with SiQDs ECL as energy donor and gold nanoparticles (AuNPs) as energy acceptor, based on which a novel ECL biosensor was fabricated. AuNPs was connected at the terminal of hairpin DNA to form a signal probe. When the probe was modified on SiQDs, ECL-RET occurred due to the short distance between AuNPs and SiQDs, resulting in the apparent decrease of ECL signal. Target DNA can open the loop of hairpin DNA, and move AuNPs away from the electrode surface. As a result, the ECL-RET process was hampered, and the ECL emission resumed. The increased ECL signals varied linearly with the target DNA concentrations in the range of 0.1fM to 1pM with the detection limit of 0.016fM (3σ). The proposed ECL sensor exhibited highly sensitivity and good selectivity in the detection of target DNA.

Anodic Electrogenerated Chemiluminescence of Ru(bpy) 3 2+ with CdSe Quantum Dots as Coreactant and Its Application in Quantitative Detection of DNA

In the present paper, we report that CdSe quantum dots (QDs) can act as the coreactant of Ru(bpy)32+ electrogenerated chemiluminescence (ECL) in neutral condition. Strong anodic ECL signal was observed at ~1.10 V at CdSe QDs modified glassy carbon electrode (CdSe/GCE), which might be mainly attributed to the apparent electrocatalytic effect of QDs on the oxidation of Ru(bpy)32+. Ru(bpy)32+ can be intercalated into the loop of hairpin DNA through the electrostatic interaction to fabricate a probe. When the probe was bound to the CdSe QDs modified on the GCE, the intense ECL signal was obtained. The more Ru(bpy)32+ can be intercalated when DNA loop has larger diameter and the stronger ECL signal can be observed. The loop of hairpin DNA can be opened in the presence of target DNA to release the immobilized Ru(bpy)32+, which can result in the decrease of ECL signal. The decreased ECL signal varied linearly with the concentration of target DNA, which showed the ECL biosensor can be used in the sensitive detection of DNA. The proposed ECL biosensor showed an excellent performance with high specificity, wide linear range and low detection limit.

A novel method for picoxystrobin determination by flow injection chemiluminescence assistance with ultrasonic treatment

A simple and sensitive flow injection chemiluminescence (FI-CL) method for determination of the fungicide picoxystrobin was described for the first time. Picoxystrobin was injected into the mixed stream of luminol with KMnO4, and the CL signal of picoxystrobin could be greatly improved when an ultrasonic treatment was adopted. Meanwhile, the signal intensity increases with the analyte concentration proportionally. The effects of the ultrasonic conditions including ultrasonic frequency, time, power and temperature on the CL signal have been studied in detail. It was found that the higher the ultrasonic frequency used, the stronger the CL intensity increased. Since the variety of ultrasonic parameters can lead to the fluctuation of signal intensity, the CL mechanism was discussed. Under the optimized conditions, the CL intensity was linear for picoxystrobin concentration over the range of 2–150 ng mL−1 with a 3σ detection limit of 0.27 ng mL−1. The relative standard deviation was 3.9% for 11 consecutive measurements of 20 ng mL−1 picoxystrobin. The method was demonstrated by application to spiked water samples from different origins including river, ground and tap water.

Enhancement of electrogenerated chemiluminescence of luminol by ascorbic acid at gold nanoparticle/graphene modified glassy carbon electrode

Gold nanoparticle/graphene (GNP/GR) nanocomposite was one-pot synthesized from water soluble graphene and HAuCl₄ by hydrothermal method and characterized by TEM, Raman spectroscopy, XRD, XPS, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS). Electrogenerated chemiluminescence (ECL) of luminol was investigated at the GNP/GR modified glassy carbon electrode (GNP/GR/GCE) and the GNP modified glassy carbon electrode (GNP/GCE) in aqueous solution respectively. The results revealed that one strong anodic ECL peak could be observed at ∼0.8 V at two modified electrodes compared with that at the bare electrode. The intensity of the anodic ECL at the GNP/GR/GCE is weaker than that at the GNP/GCE, which should be due to the synergic effect of the enhancing effect of gold nanoparticles and the inhibiting effect of graphene on anodic luminol ECL. One strong cathodic ECL peak located at ∼-0.8 V could be observed at the GNP/GR/GCE but not at the GNP/GCE, which should be result from the adsorbed oxygen at the graphene film. In the presence of ascorbic acid, the anodic ECL at the GNP/GR/GCE was enhanced more than 8-times, which is more apparent than that at the GNP/GCE. Whereas, the cathodic ECL peak was seriously inhibited at the GNP/GR/GCE. The enhanced ECL intensity at the GNP/GR/GCE varied linearly with the logarithm of ascorbic acid concentration in the range of 1.0 × 10(-8) to 1.0 × 10(-6)mol L(-1) with a detection limit of 1.0 × 10(-9) mol L(-1). The possible ECL mechanism was also discussed.

Electrogenerated chemiluminescence of luminol at a gold nanoparticle–carbon nanotube–graphene composite modified glassy carbon electrode in neutral solution

In this paper, a graphene modified glassy carbon electrode (GR-GCE), a carbon nanotube modified glassy carbon electrode (CNT-GCE), a carbon nanotube–graphene modified glassy carbon electrode (CNT–GR-GCE), and a gold nanoparticle–carbon nanotube–graphene modified glassy carbon electrode (GNP–CNT–GR-GCE) were prepared and characterized by FT-IR, atomic force microscopy (AFM), and electrochemical methods respectively. Electrogenerated chemiluminescence (ECL) of luminol was comparatively studied at these modified electrodes in neutral solution. The results revealed that carbon nanotube could intercalate into the graphene film and improve the conductivity of the CNT–GR composite significantly. The CNT–GR composite is an ideal matrix for the deposition of gold nanoparticles. At the GNP–CNT–GR-GCE, the effect of GR on luminol ECL is more predominant than that of CNT while the electrocatalytic effect of GNP on luminol ECL is well preserved. These nanomaterials exhibit a good synergic effect towards luminol ECL, which is more efficient than that of the sole material. The volume ratio of GR and CNT, the amount of modified suspension, the presence of N2 and O2, and the supporting electrolytes could affect luminol ECL. Finally, the mechanisms of luminol ECL at the modified electrodes were proposed.