ELECTROCHEMICAL SENSORS

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ELECTROCHEMICAL SENSORS

• Muzammil Hussain
• Roll 5012
• Aaida shafiq
• ROLL

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Sensor

•  Sensor is an object that detects signals from
  its surrounding environment and converts it to
  meaningful or quantifiable information. Your
  eyes, ears, and nose are all different types of
  sensors that help you navigate your surroundings
  on a day-to-day basis by detecting and processing
  light, sound, and smell/taste.
• In chemistry, sensors serve a similar purpose
  their job is to translate the reactions and
  conditions in a given environment into useful
  data for analysisand just like your nose, eyes,
  and ears, different chemical sensors gather
  distinct sets of information that may be combined
  for a more complete picture of a given chemical
  environment. In this module, we cover the basics
  of electrochemical sensors,.

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Electrochemical sensors

• Electrochemical sensors, in particular, are a
  class of chemical sensors in which an electrode
  is used as a transducer element in the presence
  of an analyte. Modern electrochemical sensors use
  several properties to detect various parameters
  in our everyday lives, whether physical,
  chemical, or biological parameters.

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• Electrochemical sensors are made up of three
  essential components a receptor that binds the
  sample, the sample or analyte, and
  a transducer to convert the reaction into a
  measurable electrical signal. In the case of
  electrochemical sensors, the electrode acts as
  the transducer.6

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• Electrochemical sensors, an electrode surface is
  used as the site of the reaction. 
• The electrode will either oxidize or reduce the
  analyte of interest. The current that is produced
  from the reaction is monitored and used to
  calculate important data such as concentrations
  from the sample.
• For instance, the nitric oxide (NO) sensor below,
  is a common electrochemical sensor. NO is an
  important vasodilator, and monitoring its levels
  becomes crucial in the diagnostics of
  cardiovascular complications. The sensor monitors
  the oxidation of NO as it occurs on the electrode
  surface.
• In many instances of electrochemical sensors, the
  electrode surface can be modified with catalysts,
  membranes, or other metals to make the electrode
  more sensitive and/or more selective toward the
  analyte (in the instance below, the Glassy Carbon
  (GC) electrode is modified with Cobalt (IV) Oxide
  and Platinum).

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TYPES

•  potentiometric
• amperometric
• conductometric.

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POTENTIOMETER

• A potentiometric sensor is a type of chemical
  sensor used in a wide array of industrial
  processes to determine the volumetric presence of
  a compound based on the detection of ionic atoms
  or molecules in the compound that carry an
  electrical charge. The sensor doesn't require a
  flow of current, but merely that the compound
  itself, whether liquid or gas, passes between the
  electrodes of the sensor device. One of the most
  common potentiometric sensor units manufactured
  as of 2011 is the oxygen sensor incorporated into
  automobiles, but there are many other uses for
  the technology.

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• The basic function of a potentiometer that is at
  the heart of a potentiometric sensor is that a
  known voltage on a reference electrode is used as
  a comparison to a voltage that changes on a
  working electrode. The voltage difference occurs
  when a solid electrolyte compound between the two
  electrodes obtains an electrical charge as a
  liquid or gas in the form of an ionic conductor
  passes by it. The level of charge is used to
  determine the quantity of ions present, and this
  value can then be compared against expected mass
  values and activate controls to maintain a
  desired equilibrium state.

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• Potentiometric sensors mainly determine the
  analyte concentration by measuring the variation
  of potential difference between working and
  reference electrodes at different analyte
  concentrations. Ion-selective electrodes belong
  to such sensor.

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Working principle

• Potentiometric sensors are based on polymeric
  membrane ion-selective electrodes (ISE) and
  ion-selective field effect transistors
  (ISFET), measuring the potential change at one
  electrode against another. In fact, this
  analytical technique has been routinely used for
  physiological testing of key electrolytes

Type I sensors have an electrolyte containing
mobile ions of the chemical species in the gas
phase that it is monitoring. The commercial
product, YSZ oxygen sensor,1 is an example of
type I.
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• Type II sensors do not have mobile ions of the
  chemical species to be sensed, but an ion related
  to the target gas can diffuse in the solid
  electrolyte to allow equilibration with the
  atmosphere. Therefore, type I and type II sensors
  have the same design with gas electrodes combined
  with metal and an electrolyte where oxidized or
  reduced ions can be electrochemically
  equilibrated through the electrochemical cell. In
  the third type of electrochemical sex , auxiliary
  phases are added to the electrodes to enhance the
  selectivity and stability.
• Type III sensors make the electrode concept even
  more confusing. With respect to the design of a
  solid state sensor, the auxiliary phase looks as
  part of the electrode. But it cannot be an
  electrode because auxiliary phase materials are
  not generally good electrical conductor. In spite
  of this confusion, type III design offers more
  feasibility in terms of designing various sensors
  with different auxiliary materials and
  electrolytes

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Amperometric sensors

• Amperometric sensors are sensitive analytical
  systems that measure current as a result of an
  electroactive substance losing (oxidation) or
  gaining (reduction) an electron while undergoing
  an electrochemical reac tion
• The amperometric method provides the ability to
  distinguish selectively between a number of
  electroactive species in solution by judicious
  selection of the applied potential and/or choice
  of electrode material.

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Working priciple

• The principle of amperometric sensor is based
  on measuring current generated by enzymatic or
  bioaffinity reaction at the electrode surface, at
  a constant working potential with respect to the
  reference electrode.

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• Conductometric sensors are miniature,
  two-electrode devices where an AC voltage applied
  across the electrodes causes a current

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Working principle

• . The basic principle of conduct metric detection
  involves a reaction that can change the ionic
  species concentration. This reaction leads to
  changes in electrical conductivity or current
  flow. In this method, two inert metal electrodes
  are used

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Advantages of electrochemical sensors

• 1. It could be interesting to a particular gas
  or fume in the scope of parts per million. The
  level of selectivity relies upon the kind of
  sensor, the sensor is worked to distinguish, the
  objective gas, and the gas focus.
• 2. Straight performance, low necessities for
  force and great goal.
• 3. Remarkable repeatability and accuracy. The
  sensor can give an exact perusing of a repeatable
  objective gas once adjusted to a known fixation.
• 4. Doesn't get harmed by other gases. The
  presence of other surrounding fumes would not
  abbreviate or restrict the sensor 's life. 5.
  Less expensive than most different advances for
  gas detection. Electrochemical sensors are
  practical, not normal for infrared and PID
  innovations

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Limitations of electrochemical

• . Limited or confined scope of temperatures. They
  are temperature touchy, so the sensors are
  regularly temperature remunerated inside. It is
  more secure to keep the temperature of the
  example as consistent as could be expected under
  the circumstances.
• Short or confined rack life. Depending on the gas
  to be distinguished and the climate in which it
  is utilized, an electrochemical sensor regularly
  has a timeframe of realistic usability of a half
  year to one year..
• Cross-affectability of different gases. In spite
  of the fact that this is an advantage, it tends
  to be a disadvantage too. A few sensors are fit
  for meddling with different gases. To know about
  conceivable bogus readings, it is critical to
  understand what gases can cause impedance with
  your sensor..
• The more prominent the objective gas
  presentation, the more limited the existence
  span. A one-to three-year future is typically
  characterized. Low mugginess and high
  temperatures can make the electrolytes of the
  sensors dry out. The electrolyte is likewise
  depleted by presentation to target gas or
  cross-affectability gases.

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