Silver nanoparticles are being incorporated into the fabric of some sports clothing to reduce bacterial growth and odour. Explain why silver nanoparticles are more effective at doing this than using the same mass of bulk silver.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Silver has well-known antibacterial properties. Manufacturers are now weaving silver nanoparticles directly into sports clothing fibres.
Model answer (4 marks)
Silver nanoparticles have a much larger surface area to volume ratio than bulk silver, so a larger proportion of the silver atoms are exposed on the surface.
Because more atoms are available on the surface, a greater number of silver ions can be released and more bacterial cells can be contacted at once.
The increased contact means the silver can interact with, penetrate and disrupt a larger number of bacteria, reducing growth and odour.
Moreover, nanoparticles can exhibit different, often enhanced, antibacterial properties compared to bulk silver, further increasing their effectiveness.
Because more atoms are available on the surface, a greater number of silver ions can be released and more bacterial cells can be contacted at once.
The increased contact means the silver can interact with, penetrate and disrupt a larger number of bacteria, reducing growth and odour.
Moreover, nanoparticles can exhibit different, often enhanced, antibacterial properties compared to bulk silver, further increasing their effectiveness.
Examiner tips
- Use the term ‘surface area to volume ratio’ explicitly. Show the chain: larger ratio → more exposed atoms → more contact → better antibacterial action. Mention the property change of nanoparticles.
- Common mistakes: 1. Confusing ‘surface area’ with ‘volume’. 2. Failing to link larger surface area to increased ion release. 3. Not mentioning the enhanced properties of nanoparticles.
Mark scheme (4 marks)
- Nanoparticles have a much larger surface area to volume ratio than bulk silver
- More silver atoms are exposed / in contact with bacteria at the surface
- This means there is more contact between the silver and bacteria / the silver can interact with more bacterial cells
- Nanoparticles can exhibit different properties to the same material in bulk / nanoparticles may have enhanced antibacterial properties compared to bulk silver
Key terms in this question
Related
- All Edexcel GCSE Chemistry (1CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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