Investigation of the electrochemical and electrocatalytic behavior of single-wall carbon nanotube film on a glassy carbon electrode

Sensitive electrochemical determination of luteolin in peanut hulls using multi-walled carbon nanotubes modified electrode

A simple and highly sensitive electrochemical method was developed for the determination of trace-level luteolin, based on the multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode (GCE). The electrochemical behaviours of luteolin indicate that MWNTs modified glassy carbon electrode (MWNTs/GCE) can greatly enhance the electrocatalytic activity towards the redox of luteolin. It leads to a considerable improvement of the redox peak current for luteolin and allows the development of a highly sensitive voltammetric sensor for the determination of luteolin. A series of experimental parameters including the pH of supporting electrolyte, accumulation potential and time were optimised. The results showed that the oxidative peak currents increased linearly with the concentration of luteolin in the range of 2.0×10(-10) to 3.0×10(-9)M, with a detection limit of 6.0×10(-11)M (S/N=3). The analytical performance of this sensor has been evaluated for detection of luteolin in peanut hulls as a real sample.

Interfacing carbon nanotubes with living mammalian cells and cytotoxicity issues

The unique structures and properties of carbon nanotubes (CNTs) have attracted extensive investigations for many applications, such as those in the field of biomedical materials and devices, biosensors, drug delivery, and tissue engineering. Anticipated large-scale productions for numerous diversified applications of CNTs might adversely affect the environment and human health. For successful applications in the biomedical field, the issue of interfacing between CNTs and mammalian cells in vitro needs to be addressed before in vivo studies can be carried out systematically. We review the important studies pertaining to the internalization of CNTs into the cells and the culturing of cells on the CNT-based scaffold or support materials. The review will focus on the description of a variety of factors affecting CNT cytotoxicity: type of CNTs, impurities, lengths of CNTs, aspect ratios, dispersion, chemical modification, and assaying methods of cytotoxicity.

Advances in carbon nanotube based electrochemical sensors for bioanalytical applications

Electrochemical (EC) sensing approaches have exploited the use of carbon nanotubes (CNTs) as electrode materials owing to their unique structures and properties to provide strong electrocatalytic activity with minimal surface fouling. Nanofabrication and device integration technologies have emerged along with significant advances in the synthesis, purification, conjugation and biofunctionalization of CNTs. Such combined efforts have contributed towards the rapid development of CNT-based sensors for a plethora of important analytes with improved detection sensitivity and selectivity. The use of CNTs opens an opportunity for the direct electron transfer between the enzyme and the active electrode area. Of particular interest are also excellent electrocatalytic activities of CNTs on the redox reaction of hydrogen peroxide and nicotinamide adenine dinucleotide, two major by-products of enzymatic reactions. This excellent electrocatalysis holds a promising future for the simple design and implementation of on-site biosensors for oxidases and dehydrogenases with enhanced selectivity. To date, the use of an anti-interference layer or an artificial electron mediator is critically needed to circumvent unwanted endogenous electroactive species. Such interfering species are effectively suppressed by using CNT based electrodes since the oxidation of NADH, thiols, hydrogen peroxide, etc. by CNTs can be performed at low potentials. Nevertheless, the major future challenges for the development of CNT-EC sensors include miniaturization, optimization and simplification of the procedure for fabricating CNT based electrodes with minimal non-specific binding, high sensitivity and rapid response followed by their extensive validation using "real world" samples. A high resistance to electrode fouling and selectivity are the two key pending issues for the application of CNT-based biosensors in clinical chemistry, food quality and control, waste water treatment and bioprocessing.

Carbon nanotube biosensors based on electrochemical detection

The advantages of carbon nanotubes, such as high surface area, favorable electronic properties, and electrocatalytic effect, attracted considerable attention very recently for the construction of electrochemical biosensors. We describe here the construction and application of carbon nanotube/epoxy rigid polymer composite electrochemical biosensor for the detection of important biomarkers, such as NADH and hydrogen peroxide.

Platinum nanoparticle ensemble-on-graphene hybrid nanosheet: one-pot, rapid synthesis, and used as new electrode material for electrochemical sensing

The development of nanoscience and nanotechnology has inspired scientists to continuously explore new electrode materials for constructing an enhanced electrochemical platform for sensing. In this article, we proposed a new Pt nanoparticle (NP) ensemble-on-graphene hybrid nanosheet (PNEGHNs), a new electrode material, which was rapidly prepared through a one-step microwave-assisted heating procedure. The advantages of PNEGHNs modified glassy carbon electrode (GCE) (PNEGHNs/GCE) are illustrated from comparison with the graphenes (GNs) modified GCE for electrocatalytic and sensing applications. The electrocatalytic activities toward several organic and inorganic electroactive compounds at the PNEGHNs/GCE were investigated, all of which show a remarkable increase in electrochemical performance relative to GNs/GCE. Hydrogen peroxide (H2O2) and trinitrotoluene (TNT) were used as two representative analytes to demonstrate the sensing performance of PNEGHNs. It is found that PNEGHNs modified GCE shows a wide linear range and low detection limit for H2O2 and TNT detection. Therefore, PNEGHNs may be an attractive robust and advanced hybrid electrode material with great promise for electrochemical sensors and biosensors design.

Discrimination of dopamine and ascorbic acid using carbon nanotube fiber microelectrodes

The detection of dopamine is a scientific challenge of great importance for the understanding of neurobiological dysfunctions. However the presence of ascorbic acid at concentrations several times higher than that of dopamine and its oxidation at a very similar potential make a selective electrochemical detection difficult. Here we report the original and intrinsic selectivity of carbon nanotube (CNT) fiber microelectrodes (CNTFM) towards dopamine oxidation without significant interaction from ascorbic acid.

Synthesis of gelatin-stabilized gold nanoparticles and assembly of carboxylic single-walled carbon nanotubes/Au composites for cytosensing and drug uptake

Gelatin-stabilized gold nanoparticles (AuNPs-gelatin) with hydrophilic and biocompatible were prepared with a simple and "green" route by reducing in situ tetrachloroauric acid in gelatin. The nanoparticles showed the excellent colloidal stability. UV-vis spectra, transmission electron microscopy (TEM), and atomic force microscopy revealed the formation of well-dispersed AuNPs with different sizes. By combination of the biocompatibility of AuNPs and excellent conductivity of carboxylic single-walled carbon nanotubes (c-SWNTs), a novel nanocomposite was designed for the immobilization and cytosensing of HL-60 cells at electrodes. The immobilized cells showed sensitive voltammetric response, good activity, and increased electron-transfer resistance. It can be used as a highly sensitive impedance sensor for HL-60 cells ranging from 1 x 10(4) to 1 x 10(7) cell mL(-1) with a limit of detection of 5 x 10(3) cell mL(-1). Moreover, the nanocomposite could effectively facilitate the interaction of adriamycin (ADR) with HL-60 cells and remarkably enhance the permeation and drug uptake of anticancer agents in the cancer cells, which could readily lead to the induction of the cell death of leukemia cells.

Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes

In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine)(2)Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs)(3)/CNT electrodes in response to 10 and 50 microM DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs)(3)/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 microM DA, the linear range was 0.1-10 microM DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 microA cm( - 2) microM( - 1). The newly fabricated (Nafion/PV I-dmeOs)(3)/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

Facile synthesis of Fe(3)O(4)/MWCNTs by spontaneous redox and their catalytic performance

Fe(3)O(4) nanoparticles with a size range of 4-8 nm were formed by the spontaneous redox reaction between Fe(3 + ) and multi-walled carbon nanotubes (MWCNTs). Cyclic voltammetry, Raman spectroscopy and x-ray photoelectron spectroscopy were employed to study the thermodynamic and dynamic conditions for the Fe(3)O(4)/MWCNTs formation. It is found that the high defect density of MWCNTs was thermodynamically favorable for the spontaneous reduction of Fe(3 + ) ions and a reaction time of above 2.5 h should be guaranteed. As the catalysts for benzene hydroxylation to phenol, the as-obtained Fe(3)O(4)/MWCNTs exhibit superior catalytic performance to those prepared by the hydrothermal method. Therefore, the spontaneous redox between the Fe(3 + ) and MWCNTs supplies an attractive facile route for the preparation of Fe(3)O(4) nanoscale catalysts.

Understanding the sensor response of metal-decorated carbon nanotubes

We have explored the room temperature response of metal nanoparticle decorated single-walled carbon nanotubes (NP-SWNTs) using a combination of electrical transport, optical spectroscopy, and electronic structure calculations. We have found that upon the electrochemical growth of Au NPs on SWNTs, there is a transfer of electron density from the SWNT to the NP species, and that adsorption of CO molecules on the NP surface is accompanied by transfer of electronic density back into the SWNT. Moreover, the electronic structure calculations indicate dramatic variations in the charge density at the NP-SWNT interface, which supports our previous observation that interfacial potential barriers dominate the electrical behavior of NP-SWNT systems.