الفهرس 
Potential-waveformsOnly 14 pages are availabe for public view
 |  | from | 233 |  |  |
| | | from | 233 | | |
Abstract
A sensor is a device which detects a variable quantity, usually electronically, and converts the measurement into signals to be recorded
elsewhere.The most important aspect of investigation of sensors issensitivity, selectivity, and stability. Sensors can be classified,according to the type of energy transfer,as thermal,electromagnetic, mechanical, and electrochemical. Among them, the electrochemical sensors are very promising analytical methods because of their high degree of selectivity and
sensitivity. They are more useful and easy to determine the concentrations of
various analytes in samples such as fluids and dissolved solid materials.They are frequently used in clinical diagnostics, occupational safety, medical engineering, process measuring engineering, and environmental analysis. Currently, much attention has been focused on developing nanomaterials,which are used for signal amplification in electrochemical sensors.Nanomaterials are usually used to take advantage of a larger surface area for biomolecules to be immobilized. This generally increases the number of binding sites available for the detection of a specific chemical analyte.Various types of nanomaterials are used in electrochemical sensors. Carbon nanotubes(CNTs)are one of the most exciting materials because of their
unique electronic, chemical, and mechanical properties. Also, clay minerals are naturally occurring materials, cheap and widely available. Among clay minerals, sodium montmorillonite (Na-MMT) has attracted much attention and has been widely used in electroanalysis owing to its huge cationic exchange capacity, well-layered structure, high chemical and mechanical stability and strong adsorptive properties attributed to the expandability of its internal layers.The proposed research represents numerous important applications in
modern science and technology. Solid electrodes based on carbon are
currently in wide spread use in electroanalysis because of their broad
potential window, low background current, rich surface chemistry, low cost, and chemical inertness. However, their sensitivity is relatively poor towards the determination of some biologically active compounds and metal ions.This may be attributed to its high surface hydrophobicity which is mainly
responsible for high overpotential (irreversibility) and sluggishness of the kinetics of the electrode process, resulting in weak electrochemical
responses. A fascinating and effective way to improve the sensitivity is to
find a good modifier to increase the rate of electron transfer (on one side),
surface area and consequently the adsorptive affinity of the surface of carbon electrodes (on other side). The modifiers used in this work are,Namontmorillonite(Na-MMT) and multi walled carbon nanotubes (MWCNT), which became attractive electrode modifiers because of unique properties they have.