scholarly journals Pencil Graphite Electrodes: A Versatile Tool in Electroanalysis

2017 ◽  
Vol 2017 ◽  
pp. 1-22 ◽  
Author(s):  
Iulia Gabriela David ◽  
Dana-Elena Popa ◽  
Mihaela Buleandra
Keyword(s):  
Surface Characterization ◽  
Surface Cleaning ◽  
Small Sample ◽  
Graphite Electrodes ◽  
Chemically Modified ◽  
Low Concentrations ◽  
Versatile Tool ◽  
User Friendly ◽  
Lower Background ◽  
Higher Sensitivity

Due to their electrochemical and economical characteristics, pencil graphite electrodes (PGEs) gained in recent years a large applicability to the analysis of various types of inorganic and organic compounds from very different matrices. The electrode material of this type of working electrodes is constituted by the well-known and easy commercially available graphite pencil leads. Thus, PGEs are cheap and user-friendly and can be employed as disposable electrodes avoiding the time-consuming step of solid electrodes surface cleaning between measurements. When compared to other working electrodes PGEs present lower background currents, higher sensitivity, good reproducibility, and an adjustable electroactive surface area, permitting the analysis of low concentrations and small sample volumes without any deposition/preconcentration step. Therefore, this paper presents a detailed overview of the PGEs characteristics, designs and applications of bare, and electrochemically pretreated and chemically modified PGEs along with the corresponding performance characteristics like linear range and detection limit. Techniques used for bare or modified PGEs surface characterization are also reviewed.

Direct electron transfer in immobilized flavoenzyme chemically modified graphite electrodes

1982 ◽  
Vol 141 ◽  
pp. 23-32 ◽  
Author(s):  
Robert M. Ianniello ◽  
Thomas J. Lindsay ◽  
Alexander M. Yacynych
Keyword(s):  
Electron Transfer ◽  
Direct Electron Transfer ◽  
Graphite Electrodes ◽  
Chemically Modified

scholarly journals Electrospinning of Ultrafine Conducting Polymer Composite Nanofibers with Diameter Less than 70 nm as High Sensitive Gas Sensor

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1744 ◽  
Author(s):  
Qianqian Zhang ◽  
Xiaoxiong Wang ◽  
Jie Fu ◽  
Ruiqiang Liu ◽  
Hongwei He ◽  
...  
Keyword(s):  
Composite Nanofibers ◽  
Fiber Diameter ◽  
Average Diameter ◽  
Impedance Analysis ◽  
Ultrafine Fibers ◽  
Ammonia Sensing ◽  
Low Concentrations ◽  
Ultrafine Nanofibers ◽  
Different Diameters ◽  
Higher Sensitivity

Polyvinyl alcohol/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PVA/PEDOT:PSS) composite ultrafine fibers were successfully fabricated by high pressure airflow assisted electrospinning. The electrical properties of PVA/PEDOT:PSS nanofibers with different diameters were characterized. The average diameter of the nanofibers can be down to 68 nm. Due to its large specific surface area, ammonia sensing of the ultrafine nanofibers is more sensitive than the traditional electrospun fibers (average fiber diameter of 263 nm). The ammonia sensing properties of the samples were tested by impedance analysis. The results show that ultrafine PVA/PEDOT:PSS nanofibers are more suitable for detecting low concentrations of ammonia with higher sensitivity.

Development of a New Immunosensor for the Detection of Dopamine

2007 ◽  
Vol 62 (7-8) ◽  
pp. 613-618
Author(s):  
Dina Fouad
Keyword(s):  
Graphite Electrodes ◽  
Microtiter Plates ◽  
Dopamine Hydrochloride ◽  
Elisa Technique ◽  
Low Levels ◽  
Graphite Rods ◽  
Higher Sensitivity

Graphite immunoelectrodes as immunosensors using indirect immobilization of a hapten were investigated for their applicability to detect dopamine hydrochloride at low levels. Conditions were optimized to achieve the highest sensitivity using the indirect immobilization of dopamine hydrochloride through a polymerized glutaraldehyde network on microtiter plates using ELISA technique. The conditions were later transferred to the graphite rods (ø 0.8 m × 20 mm) and a comparison between the two different sensitivities (IC50 midpoint of test) was carried out. Graphite electrodes showed higher sensitivity towards dopamine than ELISA, since they were able to detect dopamine with a midpoint of test of 0.2 mmol/l while using ELISA they were able to detect dopamine hydrochloride at 2 mmol/l

scholarly journals Analysis of Array-CGH Data Using the R and Bioconductor Software Suite

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Winfried A. Hofmann ◽  
Anja Weigmann ◽  
Marcel Tauscher ◽  
Britta Skawran ◽  
Tim Focken ◽  
...  
Keyword(s):  
Array Cgh ◽  
Molecular Genetic ◽  
Comparative Genomic ◽  
Accurate Identification ◽  
Genome Wide ◽  
Versatile Tool ◽  
Breakpoint Detection ◽  
Dna Copy Number Alterations ◽  
User Friendly

Background. Array-based comparative genomic hybridization (array-CGH) is an emerging high-resolution and high-throughput molecular genetic technique that allows genome-wide screening for chromosome alterations. DNA copy number alterations (CNAs) are a hallmark of somatic mutations in tumor genomes and congenital abnormalities that lead to diseases such as mental retardation. However, accurate identification of amplified or deleted regions requires a sequence of different computational analysis steps of the microarray data.Results. We have developed a user-friendly and versatile tool for the normalization, visualization, breakpoint detection, and comparative analysis of array-CGH data which allows the accurate and sensitive detection of CNAs.Conclusion. The implemented option for the determination of minimal altered regions (MARs) from a series of tumor samples is a step forward in the identification of new tumor suppressor genes or oncogenes.

scholarly journals xrayutilities: a versatile tool for reciprocal space conversion of scattering data recorded with linear and area detectors

2013 ◽  
Vol 46 (4) ◽  
pp. 1162-1170 ◽  
Author(s):  
Dominik Kriegner ◽  
Eugen Wintersberger ◽  
Julian Stangl
Keyword(s):  
Open Source ◽  
Small Sample ◽  
Reciprocal Space ◽  
Scattering Data ◽  
Versatile Tool

General algorithms to convert scattering data of linear and area detectors recorded in various scattering geometries to reciprocal space coordinates are presented. These algorithms work for any goniometer configuration including popular four-circle, six-circle and kappa goniometers. The use of commonly employed approximations is avoided and therefore the algorithms work also for large detectors at small sample–detector distances. A recipe for determining the necessary detector parameters including mostly ignored misalignments is given. The algorithms are implemented in a freely available open-source package.

Surface characterization by optical contact angle measuring system

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Adrianna Nogalska ◽  
Anna Trojanowska ◽  
Bartosz Tylkowski ◽  
Ricard Garcia-Valls
Keyword(s):  
Contact Angle ◽  
Surface Characterization ◽  
Pressure Control ◽  
Measuring System ◽  
Optical Contact ◽  
Wetting Properties ◽  
Current State ◽  
Angle Measuring ◽  
Versatile Tool

Abstract Constant development of novel materials and their characterization is a highly important matter nowadays. Optical contact angle measuring system is a very versatile tool among the surface characterization techniques. The main application of the technique is determination of hydrophobicity/hydrophilicity and wetting properties of materials. Current generation machines are fully automatized with a number of complements for temperature and pressure control, nanoliter drop generation, etc. Besides commenting on the current state of the art of the equipment, their capabilities and costs, this review includes some practical tips on the execution of the technique and data analysis.

Sub-millimolar cobalt selectively inhibits the receptive field surround of retinal neurons

1999 ◽  
Vol 16 (1) ◽  
pp. 159-168 ◽  
Author(s):  
JOZSEF VIGH ◽  
PAUL WITKOVSKY
Keyword(s):  
Receptive Field ◽  
Synaptic Transmission ◽  
Ganglion Cell ◽  
Horizontal Cell ◽  
Great Majority ◽  
Amacrine Cells ◽  
Small Sample ◽  
Feedback Circuit ◽  
Retinal Neurons ◽  
Low Concentrations

Recent work has indicated that cobalt, at sub-millimolar concentrations, blocks horizontal cell (HC) to cone feedback, without attenuating direct cone to second-order cell synaptic transmission. We utilized low concentrations (0.25–0.5 mM) of cobalt to test the contribution of the feedback circuit, and other possible cobalt-sensitive mechanisms, to the receptive-field surrounds of retinal neurons. In the great majority of cases, low cobalt blocked ganglion cell surrounds, and it invariably blocked driving the ganglion cell by extrinsic current injected into the HC network. Although low cobalt reduced the integrating area of the HC network, dopamine, which similarly constricted the HC receptive area, did not block ganglion cell surrounds. Low cobalt reduced a late depolarizing wave in the HC light-evoked waveform and selectively suppressed the depolarizing component of chromatic HCs, both signs of HC to cone feedback. Low cobalt also reduced or blocked completely the receptive-field surrounds of a small sample of bipolar and amacrine cells. These results implicate the HC to cone feedback synapse in the formation of the receptive-field surround of retinal neurons.

scholarly journals Surface Functionalization by Stimuli-Sensitive Microgels for Effective Enzyme Uptake and Rational Design of Biosensor Setups

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 791 ◽  
Author(s):  
Larisa Sigolaeva ◽  
Dmitry Pergushov ◽  
Marina Oelmann ◽  
Simona Schwarz ◽  
Monia Brugnoni ◽  
...  
Keyword(s):  
Rational Design ◽  
Surface Characterization ◽  
Choline Oxidase ◽  
Amino Groups ◽  
Graphite Electrodes ◽  
Quartz Crystals ◽  
Adsorptive Behavior ◽  
Primary Amino ◽  
The Masses ◽  
Stimuli Sensitive

We highlight microgel/enzyme thin films that were deposited onto solid interfaces via two sequential steps, the adsorption of temperature- and pH-sensitive microgels, followed by their complexation with the enzyme choline oxidase, ChO. Two kinds of functional (ionic) microgels were compared in this work in regard to their adsorptive behavior and interaction with ChO, that is, poly(N-isopropylacrylamide-co-N-(3-aminopropyl)methacrylamide), P(NIPAM-co-APMA), bearing primary amino groups, and poly(N-isopropylacrylamide-co-N-[3-(dimethylamino) propyl]methacrylamide), P(NIPAM-co-DMAPMA), bearing tertiary amino groups. The stimuli-sensitive properties of the microgels in the solution were characterized by potentiometric titration, dynamic light scattering (DLS), and laser microelectrophoresis. The peculiarities of the adsorptive behavior of both the microgels and the specific character of their interaction with ChO were revealed by a combination of surface characterization techniques. The surface charge was characterized by electrokinetic analysis (EKA) for the initial graphite surface and the same one after the subsequent deposition of the microgels and the enzyme under different adsorption regimes. The masses of wet microgel and microgel/enzyme films were determined by quartz crystal microbalance with dissipation monitoring (QCM-D) upon the subsequent deposition of the components under the same adsorption conditions, on a surface of gold-coated quartz crystals. Finally, the enzymatic responses of the microgel/enzyme films deposited on graphite electrodes to choline were tested amperometrically. The presence of functional primary amino groups in the P(NIPAM-co-APMA) microgel enables a covalent enzyme-to-microgel coupling via glutar aldehyde cross-linking, thereby resulting in a considerable improvement of the biosensor operational stability.

Sign in / Sign up

Export Citation Format

Share Document