Graphitized carbon black in polyethylene as an electrochemical sensor

The electrochemical behaviour of a material obtained by moulding graphitized carbon black and polyethylene at 100–150°C is described. The material can be used as a pellet electrode in voltammetric procedures. As a tubular anode held in a teflon body, the material is valuable as a sensor for high-performance liquid chromatography. Its properties are comparable with those of glassy carbon with better signal-to-noise ratios. It is applied for the determination of several phenols, chlorophenols and hydroquinone in the low mg l^?1 range or less.     

A disposable paper-based electrochemical sensor with an addressable electrode array for cancer screening

A novel addressable electrode array based on paper was assembled on the crossing points of the row/column electrodes to form a 4 × 6 sensor array by a facile home-made device-holder, one paper layer contained the sensing sites, the other paper layer the printed counter electrode and reference electrode.     

Acetylene black nanoparticle-modified electrode as an electrochemical sensor for rapid determination of rutin

Acetylene black nanoparticles were homogeneously dispersed into water in the presence of hydrophobic surfactant and then used to modify the surface of a glassy carbon electrode. An examination of the electrochemistry of rutin showed that this modification of the electrodes resulted in a considerable enhancement of the surface, thus remarkably increasing the signal for rutin. As a result, a sensitive and convenient electrochemical method was developed for the determination of rutin. The linear range is from 20 μg L^-1 to 5 mg L^-1, and the limit of detection is 10 μg L^-1. The method was successfully employed to the determination of rutin in traditional Chinese medicines.     

A simple method to fabricate electrochemical sensor systems with predictable high-redox cycling amplification

In this paper an easy to fabricate SU8/glass-based microfluidic sensor is described with two closely spaced parallel electrodes for highly selective measurements using the redox cycling effect. By varying the length of the microfluidic entrance channel, a diffusion barrier is created for non-cycling species effectively increasing selectivity for redox cycling species. Using this sensor, a redox cycling amplification of ～6500× is measured using the ferrocyanide redox couple. Moreover, a simple, but accurate analytical expression is derived that predicts the amplification factor based on the sensor geometry.     

A novel electrochemical noise sensor applied to detect food safety

A novel electrochemical noise (EN) sensor was elaborately designed to detect the metal residue in energy drinks. By calculating the characteristic parameter, noise resistance R _n, obtained from the EN data, the tin and iron residue can be semiquantitatively evaluated. In addition, R _n was further compared with the inductively coupled plasma mass spectrometer (ICP-MS) results. Accordingly, an interesting relationship was found between the EN data and ICP-MS results. The experimental results reveal that R _n can indirectly reflect the corrosion-induced metal release from the packaging materials; a lower R _n means a higher metal release. This electrochemical sensor has potential applications in evaluating food safety because of its fast, economic and in-situ features.     

Transition metal ion-substituted polyoxometalates entrapped in polypyrrole as an electrochemical sensor for hydrogen peroxide

A conducting polymer was used for the immobilization of various transition metal ion-substituted Dawson-type polyoxometalates (POMs) onto glassy carbon electrodes. Voltammetric responses of films of different thicknesses were stable within the pH domain 2-7 and reveal redox processes associated with the conducting polymer, the entrapped POMs and incorporated metal ions. The resulting POM doped polypyrrole films were found to be extremely stable towards redox switching between the various redox states associated with the incorporated POM. An amperometric sensor for hydrogen peroxide detection based upon the POM doped polymer films was investigated. The detection limits were 0.3 and 0.6 μM, for the Cu(2+)- and Fe(3+)-substituted POM-doped polypyrrole films respectively, with a linear region from 0.1 up to 2 mM H(2)O(2). Surface characterization of the polymer films was carried out using atomic force microscopy, X-ray photoelectron spectroscopy and scanning electron microscopy.     

Two-dimensional TiO2 (001) nanosheets as an effective photo-assisted recyclable sensor for the electrochemical detection of bisphenol A

Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO₂ (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO₂ (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ∼5.37 nmol/L (S/N = 3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO₂ (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6^th cycle. This is attributed to the non-selective OH mediation produced by the 2D TiO₂ (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.     

A novel non-enzymatic electrochemical glucose sensor modified with FeOOH nanowire

The recent development in the nanotechnology has paved the way for large number of new materials and devices of desirable properties which have useful functions for electrochemical sensor and biosensor applications. In this paper, a novel enzymeless glucose sensor is developed on the discovery that the FeOOH nanowire in fact possesses an intrinsic enzyme mimetic electrocatalytic activity similar to that found in natural peroxidases. The electrode modified with FeOOH nanowires showed a wide linear range (15 μM–3 mM) and high sensitivity (12.13 μA mM^? 1) for glucose sensing. Other excellent performances such as highly reproducible response, long-term stability, sound mechanical and chemical stability are also observed, and the interferences of ascorbic acid and dopamine can almost be completely avoided. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective glucose sensors.     

Surface-initiated DNA self-assembly as an enzyme-free and nanoparticle-free strategy towards signal amplification of an electrochemical DNA sensor

Surface-initiated DNA polymerization has been employed in this work as an appealing signal amplification strategy for electrochemical DNA sensors. This strategy is especially superior in that enzymes, colloidal particles and other bulky structures are not involved in order to achieve amplified signals, and thus is highly promising in circumventing problems due to uncontrolled nucleation, adsorption, aggregation or disassembly of nanoparticles, liposomes and proteins, as well as enzyme deactivations. Our preliminary results have shown that a decrease (as compared to an amplification-free system) in detection limit by a factor greater than 300 can be easily achieved by cyclic voltammetry under still not optimized conditions, with an ability of differentiating a single base mutation.     

Chitosan-coated hemoglobin microcapsules for use in an electrochemical sensor and as a carrier for oxygen

The article describes the preparation of chitosan-coated hemoglobin (Hb-CS) microcapsules by (a) preparing a CaCO₃ precipitate containing Hb, (b) crosslinking Hb with glutaraldehye, (c) coating the particles with chitosan, and (d) preparing Hb-CS microcapsules by removing the CaCO₃ template with a solution of disodium EDTA. The morphology and electrochemical properties of the Hb-CS microcapsules were investigated by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. An oxygen sensor was obtained by immobilizing the Hb-CS microcapsules on the surface of a glassy carbon electrode (GCE) first modified with gold nanoparticles. The application of Hb-CS microcapsules facilitates electron transfer on the surface of GCE and warrants the integrity and biological activity of Hb. The oxygen sensor, operated best at a working voltage of ?0.335  V (vs. SCE), displays a low limit of detection (30 nM). The Hb-CS microcapsules also are shown to release loaded oxygen to an anaerobic aqueous environment within 300 min.

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Graphical abstract The hemoglobin-chitosan microcapsule shows an excellent ability of electrocatalysis and carrying of oxygen.

     

Surface chemistry effects on the performance of an electrochemical DNA sensor

E-DNA sensors are a reagentless, electrochemical oligonucleotide sensing platform based on a redox-tag modified, electrode-bound probe DNA. Because E-DNA signaling is linked to hybridization-linked changes in the dynamics of this probe, sensor performance is likely dependent on the nature of the self-assembled monolayer coating the electrode. We have investigated this question by characterizing the gain, specificity, response time and shelf-life of E-DNA sensors fabricated using a range of co-adsorbates, including both charged and neutral alkane thiols. We find that, among the thiols tested, the positively charged cysteamine gives rise to the largest and most rapid response to target and leads to significantly improved storage stability. The best mismatch specificity, however, is achieved with mercaptoethanesulfonic and mercaptoundecanol, presumably due to the destabilizing effects of, respectively, the negative charge and steric bulk of these co-adsorbates. These results demonstrate that a careful choice of co-adsorbate chemistry can lead to significant improvements in the performance of this broad class of electrochemical DNA sensors.     

Concanavalin A electrochemical sensor based on the surface blocking principle at an ion-selective polymeric membrane

Microchimica Acta - We report on a new electrochemical sensor for Concanavalin A. It is based on blocking the surface of plasticized PVC membranes that were covalently modified with D-mannose using...     

A deep cavitand with a fluorescent wall functions as an ion sensor

The synthesis and characterization of a deep cavitand bearing a fluorescent benzoquinoxaline wall is reported. Noncovalent host-guest recognition events are exploited to sense small charged molecules including acetylcholine. The cavitand also exhibits an anion dependent change in fluorescence that is used to differentiate halide ions in solution.     

Experimental demonstration and simulation of electrochemical non-linear responses to glucose and its interferents with an amperometric sensor

A novel sensing system based on the multi-dimensional information contained in a dynamic non-linear response is proposed. A sinusoidal potential was applied to an amperometric-type glucose sensor and the resulting current of the sensor was analyzed by fast Fourier transformation (FFT). The amplitudes of the higher harmonics of FFT characterize the non-linear properties of the response. The amplitudes of the higher harmonics of FFT exhibit characteristic changes which depend on the concentration and the kinetics of the reactions of glucose and its interferents at the sensor surface. The essential features of the current-potential curve were reproduced by a computer simulation based on the kinetics of electrochemical reactions.     

Copper nanoclusters conjugated silica nanoparticles modified on carbon paste as an electrochemical sensor for the determination of dopamine

An electrochemical sensor based on modification of carbon paste electrode by glutathione‐capped copper nanoclusters silica nanoparticles (CuNCs/SiO₂NPs) composite for determination of dopamine in the presence of ascorbic acid was presented. Transmission electron microscopy, scanning electron microscopy, energy dispersive X‐Ray analysis, X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction and electrochemical impedance spectroscopy were used for characterization of the developed electrode. The electrochemical behavior of dopamine on CuNCs/SiO₂NPs/carbon paste electrode was investigated by cyclic voltammetry and differential pulse voltammetry. Dopamine was determined in the range of 10.0 – 900.0 μM, and the limit of detection was obtained as 0.43 μM. The electrochemical behaviors of the coexisting electroactive species, which often cause interference with the determination of dopamine, were investigated. The results show that the developed electrode does not show any interference with respect to coexisting species, even in the presence of ascorbic acid. The developed electrochemical sensor was further employed for the determination of dopamine in human blood plasma, with a good recovery.     

New electrode material GCE/AgNPs-D3 as an electrochemical sensor used for the detection of thallium ions

Optimal working parameters for the innovative electrode GCE/AgNPs-D3 were determined and the selectivity was assessed. The stripping anodic peak current of thallium characterized in linearity over range from 4.9 ⋅ 10⁻⁸ to 4.9 ⋅ 10⁻⁷ mol ⋅ dm⁻³, with LOD = 7.16 ppb (3.5 ⋅ 10⁻⁸ mol ⋅ dm⁻³). Furthermore, the new electrode showed more than sevenfold improvement in the thallium current signal compared to the unmodified electrode GCE. High selectivity was achieved using EDTA disodium salt as a complexing agent for other metals.     

Effect of molecular crowding on the response of an electrochemical DNA sensor

E-DNA sensors, the electrochemical equivalent of molecular beacons, appear to be a promising means of detecting oligonucleotides. E-DNA sensors are comprised of a redox-modified (here, methylene blue or ferrocene) DNA stem-loop covalently attached to an interrogating electrode. Because E-DNA signaling arises due to binding-induced changes in the conformation of the stem-loop probe, it is likely sensitive to the nature of the molecular packing on the electrode surface. Here we detail the effects of probe density, target length, and other aspects of molecular crowding on the signaling properties, specificity, and response time of a model E-DNA sensor. We find that the highest signal suppression is obtained at the highest probe densities investigated, and that greater suppression is observed with longer and bulkier targets. In contrast, sensor equilibration time slows monotonically with increasing probe density, and the specificity of hybridization is not significantly affected. In addition to providing insight into the optimization of electrochemical DNA sensors, these results suggest that E-DNA signaling arises due to hybridization-linked changes in the rate, and thus efficiency, with which the redox moiety collides with the electrode and transfers electrons.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT−GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, α, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4 ± 0.5 s⁻¹ and 0.51, respectively at pH = 7.0. The obtained results indicate that hydrazine peak potential at OMWCNT−GCE shifted for 14, 109, and 136 mV to negative values as compared with oxadiazole-modified GCE, MWCNT−GCE, and activated GCE surface, respectively. The electron transfer coefficient, α, and the heterogeneous rate constant, k′, for the oxidation of hydrazine at OMWCNT−GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0 μM and 10.0 to 400.0 μM and detection limit of 0.17 μM for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT−GCE was shown to be successfully applied to determine hydrazine in various water samples.

     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s^?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples.