Showing papers on "Differential pulse voltammetry published in 2012"

Toward single-DNA electrochemical biosensing by graphene nanowalls.

Abstract: Graphene oxide nanowalls with extremely sharp edges and preferred vertical orientation were deposited on a graphite electrode by using electrophoretic deposition in an Mg2+-GO electrolyte. Using differential pulse voltammetry (DPV), reduced graphene nanowalls (RGNWs) were applied for the first time, in developing an ultra-high-resolution electrochemical biosensor for detection of the four bases of DNA (G, A, T, and C) by monitoring the oxidation signals of the individual nucleotide bases. The extremely enhanced electrochemical reactivity of the four free bases of DNA, single-stranded DNA, and double-stranded DNA (dsDNA) at the surface of the RGNW electrode was compared to electrochemical performances of reduced graphene nanosheet (RGNS), graphite, and glassy carbon electrodes. By increasing the number of DPVs up to 100 scans, the RGNW electrode exhibited an excellent stability with only 15% variation in the oxidation signals, while for the RGNS electrode no detectable signals relating to T and C of 0.1 μM...

Simultaneous determination of catechol and hydroquinone using electrospun carbon nanofibers modified electrode

Abstract: In this paper, the simultaneous determination of dihydroxybenzene isomers (catechol (CC) and hydroquinone (HQ)) was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at electrospun carbon nanofiber-modified carbon paste electrode (ECF-CPE) in 0.1 M PBS (pH 7.0) solution. The ECF was prepared by combination of electrospinning and thermal treatment processes, and was modified on the surface of CPE directly without further oxidation treatment and immobilization. Compared to the bare CPE electrode, ECF-CPE exhibits much higher electrocatalytic activity toward the oxidation of dihydroxybenzene isomers with increasing of peak current and decreasing of potential difference (ΔEp) between the oxidation and reduction peaks. CV and DPV results show that the isomers can be detected selectively and sensitively at modified CPE with peak-to-peak separation about 110 mV. Under the optimized condition, the detection limits of CC and HQ are 0.2 and 0.4 μM (S/N = 3) with linear ranges of 1–200 μM in the presence of 50 μM isomer, respectively. The proposed method was successfully applied to the simultaneous determination of CC and HQ in real sample of lake water with reliable recovery. The attractive electrochemical performances and facile preparation method made this novel electrode promising for the development of effective dihydroxybenzene sensor.

Electrochemical aptasensor for the detection of tetracycline with multi-walled carbon nanotubes amplification

Abstract: Herein, we present a simple electrochemical tetracycline (TET) aptasensor with multi-walled carbon nanotubes (MWCNTs) modification. MWCNTs were dropped on the glassy carbon electrode (GCE) to immobilize the anti-TET aptamer and to construct the aptasensor. The stepwise assembly process of the aptasensor was characterized by cyclic voltammetry. Results demonstrated that the peak currents of Fe(CN) 6 3− /Fe(CN) 6 4− redox pair decreased due to the formation of anti-TET/TET complexes on the modified electrode. The optimization of the loading amount of MWCNTs, the incubating conditions of aptamer and the detection time of TET were investigated in details. Under optimal conditions, the peak currents change obtained by DPV increased linearly with the increasing TET concentrations in the range from 1 × 10 −8 M to 5 × 10 −5 M with a linear coefficiency of 0.995. This electrochemical aptasensor has a detection limit of 5 × 10 −9 M and was successfully applied to the determination of TET in spiked milk samples.

Surface-imprinted chitosan-coated magnetic nanoparticles modified multi-walled carbon nanotubes biosensor for detection of bovine serum albumin

Abstract: A surface-imprinting biosensor was prepared for bovine serum albumin (BSA) detection using chitosan-coated magnetic nanoparticles modified multi-walled carbon nanotubes (MNPs/CS-MWNTs) as a signal amplifier. The property of the MNPs/CS-MWNTs was studied using infrared spectra and their configurations were characterized with scanning electron microscopy. The molecularly imprinted biosensor was tested by differential pulse voltammetry to investigate the relationship between the response current and BSA concentration. The results showed that a wide detection linear range (1.0 × 10 −4 –1.0 × 10 −10 g mL −1 ) for the determination of bovine serum albumin with the low detection limit of 2.8 × 10 −11 g mL −1 for S/N = 3 was obtained. The surface imprinted biosensor exhibited excellent selectivity, high sensitivity, and good reproducibility. The proposed biosensor also exhibited fast balance response time of 30 s, which is propitious to rapid detect protein in spot specimens. The merits of the imprinted biosensor suggested an attractive and broadly applicable way for developing biosensors.

Graphene–Au nanoparticles nanocomposite film for selective electrochemical determination of dopamine

Abstract: A novel graphene–Au nanoparticles (AuNPs) composite film modified glassy carbon electrode (GCE) was proposed for selective detection of dopamine (DA). The resulting electrode was characterized using transmission electron microscopy, cyclic voltammetry and differential pulse voltammetry. Compared to bare and graphene modified electrodes, this nanocomposite modified electrode not only significantly improved the electrochemical peak potential difference between DA and ascorbic acid (AA), but also noticeably enhanced the current response. The constructed DA sensor showed a wide linear range (5–1000 μM) and a low detection limit (1.86 μM). The graphene–AuNPs composite, which was obtained by assembling AuNPs onto the graphene surface, could provide a promising platform to develop excellent electrochemical sensors for detecting DA.

The use of nano-carbon as an alternative to multi-walled carbon nanotubes in modified electrodes for adsorptive stripping voltammetry

Abstract: We report the advantageous use of nano-carbon black as a much cheaper alternative to multiwalled carbon nanotubes as an electrode modifier for use in adsorptive stripping voltammetry. Namely, the adsorptive stripping voltammetry (AdsSV) of nicotine is compared and contrasted at an unmodified glassy carbon (GC) electrode and GC electrodes modified with either bamboo multiwalled carbon nanotubes (MWCNT) or carbon black. The approximately spherical, primary carbon black particles used possessed an average radius of 7 nm, and are a form of ‘nano-carbon’. Their immobilisation on a GC resulted in a nanostructured surface with a large active surface area. Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV) and Differential Pulse Voltammetry (DPV) were performed using the various systems. SWV resulted in a Limit of Detection (LOD) of 12.4 ± 0.2 μM at bare GC. CV gave the lowest LOD results for MWCNT and nano-carbon modified electrodes, with LOD values of 5.0 ± 0.3 and 2.0 ± 0.3 μM. Nano-carbon is highlighted to be a cheap, highly effective electrode modifier which facilitates the electroanalytical quantification of physiologically relevant concentrations of nicotine by AdsSV.

Simultaneous electrochemical determination of dopamine and paracetamol based on thin pyrolytic carbon films

Abstract: This paper describes the determination of dopamine and paracetamol using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The selective, stable and reproducible simultaneous measurement of the two compounds is achieved using thin pyrolytic carbon (PyC) films as working electrodes. These are created via a reliable, non-catalytic chemical vapour deposition (CVD) process, and the electron transfer characteristics of the films are optimised using a simple oxygen plasma treatment. This new class of carbon electrode can detect dopamine in the range 18 to 270 μM, with a 2.3 μM limit of detection (LoD), while simultaneously sensing paracetamol in the range 15 to 225 μM (LoD 1.4 μM). A 225 mV separation between the two competing signals is realised. The accuracy of the sensor is demonstrated using human serum and commercially available pharmaceutical products. This is the first report of the application of PyC to this problem, and the performance is shown to be competitive with the leading carbon electrodes available today, particularly edge-plane pyrolytic graphite (EPPG). This work will serve as an important benchmark in the development of inexpensive, disposable, high-performance nano-structured electrodes for sensors, fuel cells and energy conversion.

Surface molecularly imprinted polymers-based electrochemical sensor for bovine hemoglobin recognition

Abstract: A novel electrochemical sensor for bovine hemoglobin (BHb) recognition and detection was prepared by a surface molecularly imprinted technique. Aldehyde group-functionalized silica microspheres were modified on an Au electrode surface, and these were subsequently covalently bound with the template molecule, BHb, through imine bonds. Electropolymerization was performed to deposit polypyrrole onto the above modified electrode surface. A three-dimensional macroporous structural sensor was obtained after etching of silica and the extraction of BHb. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the fabrication process of the sensor using [Fe(CN)6](3-)/[Fe(CN)6](4-) as an electroactive probe. Since all imprinted cavities were situated at the surface of the polymers, the prepared sensor exhibited considerably fast binding kinetics. Compared to other non-template proteins, the sensor showed an excellent recognition capacity for BHb. Moreover, the prepared sensor also exhibited a dependent relationship between the concentration of BHb and the peak current of [Fe(CN)6](3-)/[Fe(CN)6](4-).

Application of thermally reduced graphene oxide modified electrode in simultaneous determination of dihydroxybenzene isomers

Abstract: Thermally reduced graphene oxide (TRGO) was used as an excellent electrocatalyst for the construction of electrochemical sensor for simultaneous determination of dihydroxybenzene isomers including hydroquinone (HQ), catechol (CC) and resorcinol (RC). The surface morphology and structure of TRGO were investigated by utilizing transmission electron microscope, scanning electron microscopy, atomic force microscope, Raman spectroscopy and X-ray diffraction. The electrode modified with TRGO shows excellent electrocatalytic activity toward the oxidation of HQ, CC and RC. As a result, the oxidation peaks of three isomers in pH 6.0 PBS can be clearly discriminated due to large peak potential separation among them. In addition, HQ and CC can be simultaneously determined by using differential pulse voltammetry without any separation step. Under the optimized condition, the detection limits of HQ and CC are 0.75 and 0.8 μM (S/N = 3) with linear ranges of 1–500 μM in the presence of 50 μM isomer, respectively. The proposed method was successfully applied to the simultaneous determination of CC and HQ in synthetic water sample with reliable recovery. The proposed sensor has some important advantages such as low cost, ease of preparation, good stability and high reproducibility. Therefore, the present work promises for the application of graphene modified electrode in the simultaneous determination of multiple analytes.

Determination of acetaminophen by electrochemical co-deposition of glutamic acid and gold nanoparticles

Abstract: We developed an electrochemical sensor to detect acetaminophen by electrochemically co-depositing glutamic acid and gold nanoparticles on a single-walled carbon nanotube film (AuNP-PGA/SWCNT). Cyclic voltammetry indicated that the electrochemical oxidation of acetaminophen at the AuNP-PGA/SWCNT film electrode involved a two-electron, one-proton process and was pH dependent. Different pulse voltammograms of acetaminophen oxidation on the AuNP-PGA/SWCNT film electrode yielded a well-defined oxidation peak at 360 mV in 0.1 M phosphate buffered saline buffer (pH 7.2) with linear calibration from 8.3 to 145.6 μM ( R 2 = 0.997). The detection limit was estimated to be 1.18 μM. The proposed sensor is stable and reproducible from 1.15 to 5.21% with a relative standard deviation of 3.56%. The AuNP-PGA/SWCNT film electrode was able to detect acetaminophen in the presence of interfering ascorbic acid; two well-defined oxidation peaks, one for ascorbic acid at 0.15 V and the other for acetaminophen at 0.39 V, were detected. Furthermore, the fabricated sensor accurately measured the amount of acetaminophen in pharmaceutical samples. Together, these results indicate that our AuNP-PGA/SWCNT film is a promising platform for accurate and reproducible detection of acetaminophen.