Mengmeng Kang

One-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide for selective detection of mercury ions

In this paper, we report on the facile one-step synthesis of porous cuprous oxide microspheres on reduced graphene oxide (Cu2OMS–rGO) by synchronously reducing Cu2+ ions and GO with ascorbic acid sodium, followed by their application as electrochemical biosensors for the detection of mercury ions in water. After detailed characterization of the basic chemical components, crystal structure, surface morphology, and electrochemical properties of the Cu2OMS–rGO composites, single-stranded and thymine (T)-rich oligonucleotides were successively immobilized onto the surface of the composite electrode modified by Cu2OMS–rGO. Upon introduction of the target analyte, Hg2+ ions were intercalated into the DNA polyion complex membrane based on T–Hg2+–T coordination chemistry. The results show that the Cu2OMS–rGO composite has high sensitivity for the detection of Hg2+, with a detection limit of 8.62 pM within the range of 0.05 nM to 40 nM. Therefore, the Cu2OMS–rGO composite could be utilized as a novel biosensor for the detection of heavy metal ions in water or in the environment. The strategy yielded excellent selectivity of Hg2+ against other interfering metal ions. In addition, the developed DNA sensor for the determination of Hg2+ ions could be reproduced up to 10 cycles, and the recovery was approximately 95%.

An electrochemical sensor based on rhodamine B hydrazide-immobilized graphene oxide for highly sensitive and selective detection of Cu(II)

A novel strategy for fabricating a Cu2+ sensor based on rhodamine B hydrazide (RBH)-immobilized graphene oxide (GO) was reported. The thiol-modified Au electrode was functionalized by carboxyl functionalized GO through intermolecular interactions, followed by chemical bonding with RBH. The developed nanocomposite was used as an electrochemical sensor for detecting Cu2+ in aqueous solution using electrochemical impedance spectroscopy analysis with a detection limit of 0.061 nM within the range from 0.1 to 50 nM. Furthermore, the interference from potentially interfering ions such as Hg2+, Ag+, Cr2+, Fe2+, Pb2+, Ba2+, Mn2+, Co2+, and Ni2+ associated with Cu2+ analysis could be effectively inhibited. In addition, the developed Cu2+ sensor could be reproduced up to 10 cycles. In this approach, the fluorescent probe RBH can be replaced by other fluorescein derivatives which could identify the corresponding ions, which makes the approach a widely applicable strategy for metal ion detection.

Graphene nanostructures with plasma-polymerized pyrrole as an adsorbent layer for biosensors

AbstractWe report on a novel nanoarchitecture for use in highly bioactive electrochemical biosensors. It consists of multilayers of nanostructured plasma-polymerized pyrrole (ppPY) and nanosheets of electrically conductive graphene. The ppPY films were deposited by plasma-enhanced chemical vapor deposition on a graphene surface to form nanostructured composites (G-ppPY). The G-ppPY films were then coated with protein (BSA as a model) by adsorption, and then with DNA. The adsorption of protein and DNA on the nanocomposite was studied by electrochemical impedance spectroscopy and with a quartz crystal microbalance. Results demonstrated that the adsorption of biomolecules on G-ppPY films causes a higher variation in its electrochemical properties and adsorbed amount than that on a plain ppPY surface. This indicates that the presence of graphene can enhance the electrochemical activity of ppPY without reducing the sensitivity of biomolecular adsorption. FigureA novel nanoarchitecture is developed for use in highly bioactive electrochemical biosensors, which is composed of multilayers of nanostructured plasma-polymerized pyrrole and electrically conductive graphene nanosheets. The presence of graphene can enhance the electrochemical activity of ppPY without reducing the sensitivity of biomolecular adsorption.

Easy amino-group modification of graphene using intermolecular forces for DNA biosensing

We demonstrated an easy and efficient approach to produce amino-group-functionalized graphene (G-NH2) for highly sensitive DNA biosensing through intermolecular interaction. The nucleotide molecules prefer to anchor onto the as-prepared G-NH2 surface rather than be immobilized on pristine graphene. The electrostatic interaction between the positive charges of the ionized amino on G-NH2 and the negative charges of phosphate groups on nucleotide chains enabled label-free probe DNA to be immobilized on the G-NH2 surface. The electrochemical performance and quality variations during the preparation of G-NH2 and nucleotide immobilization processes were determined by electrochemical measurements and quartz crystal microbalance in situ, respectively. Results showed that complementary target DNA could be hybridized with probe DNA within the concentration range of 0.1 nM to 200 nM, and the detection limit was 0.8 nM. Therefore, this kind of G-NH2 could be an alternative for DNA biosensing.