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This question paper consists of four
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identified by CMNS128001
CMNS128001
Drawing instruments and electronic
calculators may be used.
 University of Leeds
Examination for the Degree of BSc Nanotechnology
(May 2011)
CMNS1280: Molecular electrochemical mechanisms in bionanotechnology
Time allowed: 2 hours
The Examination Paper consists of 5 questions - all of which carry equal marks.
Attempt three questions
Do not write or draw with red ink or red pencil
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To obtain full marks candidates must show how answers are derived
All symbols not specifically defined have their normally accepted meanings
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CMNS128001
1.
(a)
The understanding of the mechanism of galvanic, static and electrolytic cells is fundamental
to electrochemical processes which involve the interaction of electrical energy with chemical
reactions.
(i) Explain the fundamental difference between galvanic, static and electrolytic cells.
[4 marks]
(ii) In a galvanic and electrolytic cell, which reaction takes place at the cathode: reduction or
oxidation?
[1 mark]
(b)
(i) What is the lead-acid accumulator? What are the two electrodes in the charged cell of a
battery and what are the two electrodes in a discharged or "flat" cell of the battery? What is
the electrolyte used?
[6 marks]
(ii) By writing the equations for the two chemical half reactions explain how the lead-acid
accumulator works.
[4 marks]
(iii) What is the voltage that each cell of a lead-acid accumulator generates?
(iv) Name two factors which degrade a lead-acid accumulator's performance.
[1 mark]
[2 marks]
(v) Detail the difference in operational mechanism of a lithium ion diffusion cell to a leadacid cell.
[2 marks]
2.
(a) Polarography is a highly elegant technique invented by Jaroslav Heyrovsky for which he
received the Nobel Prize in 1959.
(i) What is the unique feature of polarography which separates it from other electroanalytical
techniques?
[2 marks]
(ii) Sketch a polarogram and label two important details of the polarographic wave on your
diagram.
[4marks]
(b) Electrochemical or electrolytic reactions at electrodes are categorised into reversible and
irreversible reactions.
(i) Why does an electrochemical process appear irreversible?
[2 marks]
(ii) Explain with a sketch how the polarographic current-potential curve characterising an
electrochemical process of reduction changes when the process becomes irreversible.
[3 marks]
(iii) What is the potential value in mV of the separation between the anodic and cathodic
peaks of a reversible one electron cyclic voltammogram?
[2 marks]
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CMNS128001
(c)
(i) Explain the principle behind the working of an ion selective electrode.
[2 marks]
(ii) A glass electrode is a specific example of an ion selective electrode. How does a glass
electrode work?
[2 marks]
(iii) In your answer sketch a diagram of the glass electrode labelling important details in it.
[3 marks]
3.
How might proteins such as enzymes or antibodies be modified to improve their stability or
otherwise change their properties?
[12 marks]
Briefly describe the biological organisms in which the new proteins might be expressed and
the advantages and disadvantages of these expression systems.
[8 marks]
4.
(a) Describe the approaches that might be used to manufacture a biosensor electrode.
[8 marks]
(b) Describe the approaches that might be used to attach an enzyme or antibody to this
electrode to produce a functional biosensor.
[12 marks]
5.
Although polarography was initially used as an analytical technique for heavy metal ions in
water its sensitivity was never high and the lowest detection limit obtained was about 10-4 mol
dm-3 of a heavy metal ion. Anodic stripping voltammetry (ASV) was subsequently developed
as a suitable analytical technique for heavy metal ions in water.
(a)
(i) Describe the principle of ASV and state why it is advantageous compared to polarography?
[3 marks]
(ii) Sketch the potential programme used when carrying out an ASV experiment.
[3 marks]
(iii) Name four common toxic pollutant heavy metal ions which can be determined using
ASV.
[4 marks]
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CMNS128001
(iv) Name two working electrode systems used in ASV and draw sketches of them with their
critical operating parts.
[4 marks]
(b)
Zinc oxide (ZnO) nanoparticles are known to release soluble Zn2+ ion. This solubility varies
as a function of solution pH. The lower the solution pH, the higher the solubility of the ZnO.
If a centrifugate of a ZnO dispersion is analysed for Zn using inductively coupled plasmamass spectrometry (IPC-MS), a higher value of Zn in the centifugate is obtained than when
using ASV. Please explain the reason for this observation.
[3 marks]
(c)
Explain what is meant by adsorptive (or cathodic stripping voltammetry) and explain the
principles behind it.
[3 marks]
END OF PAPER