Shaping Wei

Overoxidized polyimidazole/graphene oxide copolymer modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid, guanine and adenine

In the present work, a novel strategy based on overoxidized polyimidazole (PImox) and graphene oxide (GO) copolymer modified electrode was proposed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), guanine (G) and adenine (A). The copolymer was characterized by the scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effects between PImox and GO, the proposed electrode exhibited excellent electrochemical catalytic activities and high selectivity and sensitivity toward the oxidation of AA, DA, UA, G and A. The peak separations between AA and DA, AA and UA, UA and G, and G and A were 140 mV, 200 mV, 380 mV and 300 mV, respectively. The linear response ranges for AA, DA, UA, G and A were 75-2275 μM, 12-278 μM, 3.6-249.6 μM, 3.3-103.3 μM and 9.6-215 μM, respectively, and corresponding detection limits were 18 μM, 0.63 μM, 0.59 μM, 0.48 μM and 1.28 μM.

A signal-on electrochemiluminescence biosensor for detecting Con A using phenoxy dextran-graphite-like carbon nitride as signal probe.

A novel signal-on electrochemiluminescence (ECL) biosensor for detecting concanavalin A (Con A) was fabricated with phenoxy dextran-graphite-like carbon nitride (DexP-g-C3N4) as signal probe. In this construction strategy, the nanocomposites of three-dimensional graphene and gold nanoparticles (3D-GR-AuNPs) were used as matrix for high loading of glucose oxidase (GOx), which served as recognition element for bounding Con A. Con A further interacted with DexP-g-C3N4 through a specific carbohydrate-Con A interaction to achieve a sandwiched scheme. With the increase of Con A incubated onto the electrode, the ECL signal resulted from DexP-g-C3N4 would enhance, thus achieving a signal-on ECL biosensor for Con A detection. Due to the integration of the virtues of 3D-GR-AuNPs and the excellent ECL performance of DexP-g-C3N4, the prepared biosensor exhibits a wide linear response range from 0.05 ng/mL to 100 ng/mL and a low detection limit of 17 pg/mL (S/N=3).

Electrochemical sensor based on overoxidized dopamine polymer and 3,4,9,10-perylenetetracarboxylic acid for simultaneous determination of ascorbic acid, dopamine, uric acid, xanthine and hypoxanthine

A novel electrode based on 3,4,9,10-perylenetetracarboxylic acid (PTCA) and overoxidized dopamine polymer (PDAox) was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XN) and hypoxanthine (HXN). The developed sensors exhibited an excellent catalytic activity, high sensitivity and good selectivity toward the oxidation of AA, DA, UA, XN and HXN. Scanning electron microscopy (SEM), cyclic voltammetry (CV), different pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the sensor. The peak separations between AA–DA, DA–UA, UA–XN and XN–HXN were large, up to 0.15, 0.18, 0.37 and 0.4 V, respectively. The calibration curves for AA, DA, UA, XN and HXN were obtained in the ranges of 76 μM to 3.9 mM, 0.60 to 253 μM, 1.8 to 238 μM, 5.1 to 289 μM and 3.8 to 293 μM with detection limits (S/N = 3) of 25.3 μM, 0.20 μM, 0.60 μM, 1.7 μM and 1.3 μM, respectively. The integration of PDAox and PTCA in the sensor opens up a facile and promising method for the simultaneous determination of above five substances.

A cathodic luminol-based electrochemiluminescence biosensor for detecting cholesterol using 3D-MoS2–PANI nanoflowers and Ag nanocubes for signal enhancement

A sensitive cathodic luminol-based electrochemiluminescence (ECL) biosensor for detecting cholesterol was fabricated with three-dimensional MoS2–polyaniline (3D-MoS2–PANI) nanoflowers and Ag nanocubes (AgNCs) for signal enhancement. In this study, the synthesized 3D-MoS2–PANI–AgNCs nanocomposites with a large surface area were used as a matrix for loading a high amount of cholesterol oxidase (ChOx). Subsequently, the loaded ChOx efficiently catalyzed the oxidation of cholesterol to produce H2O2 in situ, which could promote the oxidation of luminol to generate a cathodic ECL signal. In addition, 3D-MoS2–PANI–AgNCs nanocomposites accelerate the decomposition of H2O2 into reactive oxygen species (ROSs), which increase the ECL intensity. Due to the integration of the properties of 3D-MoS2–PANI nanoflowers and AgNCs, the proposed cholesterol biosensor exhibits a wide linear response range from 3.3 nM to 0.45 mM with a low detection limit of 1.1 nM.

An ultrasensitive electrochemiluminescence biosensor for the detection of concanavalin A based on Au nanoparticles-thiosemicarbazide functionalized PtNi nanocubes as signal enhancer

A sandwich-configuration electrochemiluminescence (ECL) biosensor was constructed for detecting concanavalin A (ConA) based on peroxydisulfate/oxygen (S2O82-/O2) system. In this work, the gold nanoflower modified Zn-doped SnO2 was used as a substrate to adsorb recognition element horseradish peroxidase (HRP) for binding ConA. Then, Au nanoparticles-thiosemicarbazide functionalized PtNi nanocubes (AuNPs-TSC-PtNi NCs), as a novel ECL signal tracer, were incubated onto the electrode through a specific carbohydrate-ConA interaction, thus achieving a sandwiched structure. The integration of amplifying effect of both TSC and PtNi NCs on the ECL of S2O82-/O2 system endowed the biosensor a high sensitivity. The linear range for ConA detection was from 0.0010ng/mL to 10ng/mL with a detection limit of 0.0002ng/mL (S/N=3).

Electrochemiluminescence biosensor for cholesterol detection based on AuNPs/L-cys–C60 nanocomposites

A sensitive electrochemiluminescence (ECL) biosensor was fabricated for detection of cholesterol based on an anodic ECL of luminol at low potential. First, C60 was functionalized with L-cysteine (L-cys) to obtain an L-cys–C60 composite, which was modified onto the surface of glassy carbon electrodes for adsorbing gold colloidal nanoparticles (AuNPs). Subsequently, cholesterol oxidase (ChOx) was dropped onto the surface of modified electrode to fabricate a cholesterol biosensor. The assembly process was characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and ECL. Under the optimal conditions, the proposed biosensor exhibited a sensitive response to cholesterol in the concentration range from 1.7 × 10−5 mM to 0.30 mM with the detection limit of 5.7 × 10−6 mM (S/N = 3). Furthermore, the proposed biosensor has good reproducibility, stability and anti-interferent ability.

Manganese(III)meso-tetrakis(4-N-methylpyridyl)-porphyrin and mediator thionine co-decorated DNA nanowires for sensitive electrochemical monitoring of mercury(II)

We developed a novel electrochemical DNA biosensor for mercury(II) ion (Hg2+) detection on the basis of manganese(III) meso-tetrakis(4-N-methylpyridyl)-porphyrin (MnTMPyP) and electron mediator thionine (Thi) co-decorated DNA nanowires for signal amplification. The T-rich capture DNA assembled on the electrode could successfully immobilize the primer DNA via specific base-pairing, which triggered the hybridization chain reaction (HCR) to form long DNA nanowires with the aim of loading abundant MnTMPyP and electron mediator Thi. In the electrolyte containing H2O2, the MnTMPyP loaded in the DNA nanowires showed superior peroxidase-like activity and electrocatalyzed the reduction of H2O2, promoting the redox reaction of Thi with a dramatically amplified electrochemical signal. However, in the presence of target Hg2+, Hg2+-mediated thymine base pairs (T–Hg2+–T) are formed between the two neighboring T-rich capture DNAs, which resulted in the release of the MnTMPyP and Thi co-decorated DNA nanowires from the electrode surface, providing a reduced readout signal for the quantitative electrochemical detection of Hg2+. The results showed that the proposed electrochemical DNA biosensor was highly sensitive to Hg2+ in the concentration of 1.0 ng L−1 to 107 ng L−1 with a detection limit of 0.5 ng L−1 (2.5 pM), and it also exhibited excellent selectivity against other interferential metal ions.