Sujuan Li

Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production

Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g−1 at 1.25 A g−1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h−1.

Amplified voltammetric detection of dopamine using ferrocene-capped gold nanoparticle/streptavidin conjugates

Dopamine (DA) is one of the most important neurotransmitters present in brain tissues and body fluids of mammals. The change in the concentration levels has been associated with various diseases and disorders. Thus, sensitive and selective determination of DA is much preferred. In this work, sandwich-type electrochemical biosensor was developed, in which phenylboronic acid immobilized onto gold electrodes was used to capture DA. The anchored DA was then derivatized with biotin for the attachment of ferrocene-capped gold nanoparticle/streptavidin conjugates. The voltammetric responses were found to be proportional to the concentrations of DA ranging from 0.5 to 50 nM. A detection limit of 0.2 nM was achieved, which is 1~2 orders of magnitude lower than those achievable at various chemically modified electrodes. Analytical merits (e.g., dynamic range, reproducibility, detection level, selectivity and interference) were evaluated. The feasibility of the method for analysis of DA in artificial cerebrospinal fluid and dopamine hydrochloride injection has been demonstrated.

Facile synthesis of porous nickel manganite materials and their morphology effect on electrochemical properties

New porous bipyramid, fusiform and plate structured NiMn2O4 materials have been successfully synthesized by calcining oxalate precursors in the air without using any template or surfactant. More importantly, electrochemical measurements show that morphology affects their electrochemical properties, and the porous plate structured NiMn2O4 showed a large specific capacitance and a long cycle life.

Competitive electrochemical immunoassay for detection of β-amyloid (1–42) and total β-amyloid peptides using p-aminophenol redox cycling

β-Amyloid (1-42) peptide (Aβ(1-42)) is believed to be important for diagnosis and prognosis of Alzheimers disease (AD) serving as a reliable molecular biomarker. However, the levels of Aβ(1-42) may differ by gender and age; thus, assay of Aβ(1-42) only might be unable to discriminate between AD and health or other types of dementia. In this work, we reported a sensitive and selective electrochemical method for detection of both Aβ(1-42) and total Aβ using p-aminophenol (p-AP) redox cycling on antibody-modified gold electrodes. Specifically, the conjugates performed between streptavidin-conjugated alkaline phosphatase (SA-ALP) and biotinylated Aβ peptides were captured by the antibody-modified electrodes, which induced the production of electrochemically active p-AP from the p-aminophenyl phosphate (p-APP) substrate. In the presence of tris(2-carboxyethyl)phosphine (TCEP), p-AP could be cycled after its electro-oxidization on the electrode, enabling the increase of the anodic current. Because native Aβ competed with the conjugates to bind the anchored antibody, the signal decreased with the increase of native Aβ concentration. A detection limit of 5 pM was achieved. To demonstrate the viability of the method for analysis of Aβ(1-42) and total Aβ in real sample, artificial cerebrospinal fluid (aCSF) containing Aβ(1-40), Aβ(1-42) and Aβ(1-16) was tested. We believe that the simultaneous detection of Aβ(1-42) and total Aβ would be valuable for the early diagnosis of AD.

3D porous metal-organic framework as an efficient electrocatalyst for nonenzymatic sensing application

Novel electroactive materials with high surface area and stability have great potential for electrochemical sensor. Herein, we demonstrate the exploitation of a porous Cu-based metal-organic framework (Cu-MOF) with large pore size as nonenzymatic sensors for the electrochemical determination of hydrogen peroxide (H2O2) and glucose. The Cu-MOF shows high stability even in NaOH solution. The as-prepared Cu-MOF modified carbon paste electrode (CPE) presents a well-behaved redox event from electroactive metal centers in the MOF at the physiological pH which can be utilized to catalyze the electroreduction of H2O2. It also exhibited excellent electrocatalytic activity towards the oxidation of glucose in alkaline solution. The results showed that the nonenzymatic sensors based on the Cu-MOF display excellent analytical performances, which make it a promising candidate in electrochemical sensor.

Preparation of electrochemically reduced graphene oxide-modified electrode and its application for determination of p -aminophenol

A simple and eco-friendly electrochemical method to reduce graphene oxide precursor was employed for fabrication of graphene sheets modified glassy carbon electrode, and then, the resulting electrode [electrochemically reduced graphene oxide (ERGO)/glassy carbon electrode (GCE)] was used to determine p-aminophenol. The experimental results demonstrated that the modified electrode exhibited excellent electrocatalytic activity toward the redox of p-aminophenol as evidenced by the significant enhancement of redox peak currents and the decreased peak-to-peak separation in comparison with a bare GCE. A highly sensitive and selective voltammetry determination of p-aminophenol is developed using the ERGO/GCE. This method has been applied for the direct determination of p-aminophenol in artificial wastewater.

Mesoporous uniform ammonium nickel phosphate hydrate nanostructures as high performance electrode materials for supercapacitors

Mesoporous uniform ammonium nickel phosphate hydrate nanostructures are successfully prepared by a one-pot hydrothermal method. As a result of the unique feature of large surface area (418 m2 g−1) and tunable mesostructures, the material exhibits good performance as supercapacitor electrodes, with a specific capacitance of 1072 F g−1 in 3.0 M KOH at a current density of 1.50 A g−1, and show a good cycle life which does not obviously decay after 3000 cycles (the retention 95.0% of initial specific capacitance after 3000 cycles).

NH4CoPO4·H2O microbundles consisting of one-dimensional layered microrods for high performance supercapacitors

Unique layered NH4CoPO4·H2O microbundles consisting of one-dimensional layered microrods are firstly synthesized by a facile hydrothermal method. As a result of novel layered structures, there are many nanolayered channels for the diffusion of ions and electrolytes. The preliminary supercapacitor investigation indicates that the specific capacitance of layered NH4CoPO4·H2O microbundle electrodes reaches up to 662 F g−1 at a current density of 1.5 A g−1 and remains at 520 F g−1 even at 15.0 A g−1. The cycle test shows excellent cycling performance of layered NH4CoPO4·H2O microbundle electrodes (the retention 92.7% of initial specific capacitance after 3000 cycles).

A comparative study of different types of reduced graphene oxides as electrochemical sensing platforms for hydroquinone and catechol

We compared the electrochemical performance of various reduced graphene oxides (RGOs), including chemically reduced graphene oxide (CRGO), thermally reduced graphene oxide (TRGO), and electrochemically reduced graphene oxide (ERGO) under different reduction potentials, using aromatic species of hydroquinone and catechol as analytes. Strong adsorption of analytes on RGOs surface is found due to π-π interaction between RGOs and aromatic species. Analytical parameters of electron transfer rate, detection sensitivity, and linear response range were considered. CRGO showed the fastest heterogeneous electron transfer rate and the most wide linear range but among the poorest detection sensitivity. The different restoration extent of graphitic network, such as ERGO prepared under different reduction potentials, will also affect the sensing performance. These results will enhance our understanding of the applicability of RGOs in biosensing.

Glassy carbon electrode modified with 7,7,8,8-tetracyanoquinodimethane and graphene oxide triggered a synergistic effect: low-potential amperometric detection of reduced glutathione.

A sensitive electrochemical sensor based on the synergistic effect of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and graphene oxide (GO) for low-potential amperometric detection of reduced glutathione (GSH) in pH 7.2 phosphate buffer solution (PBS) has been reported. This is the first time that the combination of GO and TCNQ have been successfully employed to construct an electrochemical sensor for the detection of glutathione. The surface of the glassy carbon electrode (GCE) was modified by a drop casting using TCNQ and GO. Cyclic voltammetric measurements showed that TCNQ and GO triggered a synergistic effect and exhibited an unexpected electrocatalytic activity towards GSH oxidation, compared to GCE modified with only GO, TCNQ or TCNQ/electrochemically reduced GO. Three oxidation waves for GSH were found at -0.05, 0.1 and 0.5V, respectively. Amperometric techniques were employed to detect GSH sensitively using a GCE modified with TCNQ/GO at -0.05V. The electrochemical sensor showed a wide linear range from 0.25 to 124.3μM and 124.3μM to 1.67mM with a limit of detection of 0.15μM. The electroanalytical sensor was successfully applied towards the detection of GSH in an eye drop solution.