Gold is a metal that has been used for centuries in jewellery. Scientists have recently developed gold nanoparticles for use in medical treatments. Explain why gold nanoparticles may behave differently compared to a bulk sample of gold, and suggest one reason why gold nanoparticles might be useful in delivering drugs inside the human body.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Gold nanoparticles have diameters between 1 nm and 100 nm. A bulk sample of gold appears yellow and is chemically unreactive. Gold nanoparticles, however, can appear red or purple in solution and show increased chemical reactivity.
Model answer (4 marks)
Gold nanoparticles have a much larger surface area to volume ratio than bulk gold, so a greater proportion of atoms are exposed on the surface.
Because more atoms are available to interact, the particles show different chemical reactivity and optical properties (e.g. they can appear red or purple in solution).
Their diameters (1–100 nm) are small enough to penetrate cells or pass through cell membranes.
This allows them to deliver drugs directly to specific cells or tumours, improving efficacy and reducing side‑effects.
Because more atoms are available to interact, the particles show different chemical reactivity and optical properties (e.g. they can appear red or purple in solution).
Their diameters (1–100 nm) are small enough to penetrate cells or pass through cell membranes.
This allows them to deliver drugs directly to specific cells or tumours, improving efficacy and reducing side‑effects.
Examiner tips
- Use the phrase ‘larger surface area to volume ratio’ and link it to ‘more atoms exposed’. Explain the optical change briefly. Mention the size range and its relevance to cell penetration. Finish with a clear benefit for drug delivery.
Common mistakes
- Confusing bulk gold colour with nanoparticle colour. Failing to mention the size range (1–100 nm). Lacking a clear link between surface area and reactivity. Not stating the benefit of targeted drug delivery.
Mark scheme (4 marks)
- Nanoparticles have a much larger surface area to volume ratio than bulk gold
- The higher surface area to volume ratio means more atoms are exposed / available to interact, leading to different (e.g. chemical or optical) properties
- Gold nanoparticles are very small / have diameters between 1 nm and 100 nm, so they can enter cells or pass through cell membranes
- This allows targeted / more effective drug delivery (to specific cells or tumours), reducing side effects or improving treatment
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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