Shirong Hu

A sensitive and reliable dopamine biosensor was developed based on the Au@carbon dots-chitosan composite film

A novel composite film of Au@carbon dots (Au@CDs)-chitosan (CS) modified glassy carbon electrode (Au@CDs-CS/GCE) was prepared in a simple manner and applied in the sensitive and reliable determination of dopamine (DA). The CDs had carboxyl groups with negative charge, which not only gave it have good stability but also enabled interaction with amine functional groups in DA through electrostatic interaction to multiply recognize DA with high specificity, and the Au nanoparticle could make the surface of the electrode more conductive. Compared with the bare GCE, CS/GCE, and CDs-CS/GCE electrodes, the Au@CDs-CS/GCE had higher catalytic activity toward the oxidation of DA. Furthermore, Au@CDs-CS/GCE exhibited good ability to suppress the background current from large excess ascorbic acid (AA) and uric acid (UA). Under the optimal conditions, selective detection of DA in a linear concentration range of 0.01-100.0 μM was obtained with the limit of 0.001 μM (3S/N). At the same time, the Au@CDs-CS/GCE was also applied to the detection of DA content in DAs injection with satisfactory results, and the biosensor could keep its activity for at least 2 weeks.

A high performance electrochemical biosensor based on Cu2O–carbon dots for selective and sensitive determination of dopamine in human serum

A green and facile method was developed by synthesizing a cuprous oxide–carbon dots/Nafion (Cu2O–CDs/NF) composite film for highly sensitive and reliable determination of dopamine (DA). The Cu2O nanoparticles could improve the conductivity of the electrode, while the CDs with carboxyl groups and the NF with sulfo groups could attract cations via the ion-exchange model and exclude anions by the electrostatic action. The proposed biosensor exhibited a low detection limit of 1.1 nM with a wide linear range of 0.05–45.0 μM and acquired excellent sensitivity and selectivity for DA. Furthermore, the Cu2O–CDs/NF/GCE also was applied to determine DA in human serum with satisfactory results and showed good activity for more than two months.

Designed self-assembled hybrid Au@CdS core–shell nanoparticles with negative charge and their application as highly selective biosensors

A novel and general strategy for the synthesis of a monodispersed Au@CdS core-shell structure with uniform morphology and size through a self-assembly process is proposed here. The obtained negatively charged Au@CdS hybrid core-shell nanoparticles (NPs) are highly selective to dopamine (DA), in the presence of oxidation of ascorbic acid (AA) and uric acid (UA), based on electrostatic interaction. The fabricated biosensor shows a wide linear range from 0.002 to 800 μmol L-1, with a lower detection limit of 0.55 nmol L-1 (n = 5, S/N = 3), revealing the high-sensitivity properties. Electrostatic charge plays an important role in the selective electrocatalytic activity of Au@CdS hybrid core-shell nanoparticles, that is the formation of an electrostatic system between the negatively charged Au@CdS hybrid core-shell NPs and the DA cation. The modified electrode is used to achieve the real-time quantitative detection of DA for biological applications, and satisfactory results are obtained. Due to the advantages of the biosensor, its selectivity, sensitivity and stability, it will have a bright future in the field of medical diagnosis.

Microwave synthesis of 3D rambutan-like CuO and CuO/reduced graphene oxide modified electrodes for non-enzymatic glucose detection

A novel type of cupric oxide (CuO) particles-reduced graphene oxide (r-GO) modified electrode has been fabricated through a facile, simple and fast microwave method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD) were employed to characterize the morphologies and structures of the as-prepared samples. The results reveal that the CuO/r-GO composite was a porous 3D rambutan-like microstructure with high surface area. Then the CuO and CuO/r-GO electrodes were constructed for their use as non-enzymatic glucose biosensors owing to their high-performance and sensitivity under alkaline conditions. The proposed biosensor exhibits glucose concentrations in the range from 0.50 μM to 3.75 mM. Besides, chronoamperometry demonstrates a desirable sensitivity of 52.1 μA mM-1 at an applied potential of 0.50 V (vs. Ag/AgCl), with a detection limit of 0.10 μM (signal/noise = 3). Most importantly, this non-enzymatic glucose biosensor has highly stable characteristics and can be manufactured into a long-term stability electrode for its application in various complicated circumstances. All these results confirm that this CuO/r-GO biosensor is a promising active material with excellent analytical properties for non-enzymatic glucose detection.

A nitrogen-doped carbon dot/ferrocene@β-cyclodextrin composite as an enhanced material for sensitive and selective determination of uric acid

A simple and convenient method for the synthesis of nitrogen-doped carbon dots (N-CDs) was reported. Layers of the N-CDs and ferrocene@β-cyclodextrin (Fc@β-CD) host–guest complex were deposited on a glassy carbon electrode (GCE) which was used for highly selective and sensitive detection of uric acid (UA). Under the optimal conditions, compared to bare, N-CD and Fc@β-CD modified electrodes, the Fc@β-CD/N-CD/GCE had higher catalytic activity toward the oxidation of UA. Differential pulse voltammetry (DPV) was used as the analytical technique for detection of UA, the observed linear range for the determination of the UA concentration was from 5 μM to 120 μM with the detection limit estimated to be 0.08 μM (3S/N). Meanwhile, it was applied to determine uric acid in spiked samples with satisfactory results.

Ultrasensitive-electrochemical sensor for the detection of luteolin in Chrysanthemums and Peanut shells using an Au/Pd/reduced graphene oxide nanofilm

In this study, a rapid and ultrasensitive luteolin sensor has been developed based on an Au/Pd/reduced graphene oxide (Au/Pd/rGO) nanofilm modified glassy carbon electrode (GCE). A green and facile method was used for the synthesis of Au/Pd/rGO, in which the groups on GO, for example, hydroxyls, epoxides and carboxyls, are used for the in situ anchoring of Au/Pd bimetallic nanocrystal precursors, which are further reduced to form an Au/Pd/rGO nanofilm. Under optimized conditions, the Au/Pd/rGO/GCE demonstrated a more excellent electrochemical response for the determination of luteolin than GCE, Au/rGO/GCE and Pd/rGO/GCE. This luteolin sensor has a linear range from 0.01 to 80.0 μM and a detection limit of 0.98 nM. In addition, the sensor was also applied to determine luteolin in Chrysanthemums and Peanut shells with satisfactory results. The proposed sensor has good stability for three months.

Microwave-assisted synthesis of carbon dots–zinc oxide/multi-walled carbon nanotubes and their application in electrochemical sensors for the simultaneous determination of hydroquinone and catechol

A facile, efficient, and rapid microwave-assisted synthesis was developed to prepare carbon dots–zinc oxide/multi-walled carbon nanotubes (CDs–ZnO/MWCNTs) composite. The CDs–ZnO/MWCNT material was characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The electrode modified with the CDs–ZnO/MWCNTs composite was applied for the simultaneous determination of hydroquinone (HQ) and catechol (CC) in 0.1 M phosphate buffer solution (PBS, pH = 4.5). The anodic potential difference (ΔEpa) between HQ and CC was 104 mV, which indicated that the modified electrode could simultaneously detect HQ and CC. The calibration curves for both HQ and CC were obtained in the range from 5.0 to 200 μM, and the detection limits (S/N = 3) were 0.02 μM and 0.04 μM, respectively. The modified electrode was applied to determine HQ and CC in tap water and the recovery rates were 99.3–105.4% for HQ and 104.3–110.1% for CC.