Question

Sunscreen lotions contains nanoparticles of

• A. Gold
• B. Pt
• C. $\text{TiO}_2$
• D. Pd

Hint:

Titanium dioxide ($\text{TiO}_2$) and Zinc oxide (ZnO) are the two FDA-approved physical (mineral) sunscreen ingredients. If you see either in a multiple-choice question about sunscreens or UV protection, it's the correct answer!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks us to identify which specific metal or metal oxide nanoparticle is actively used in the formulation of commercial sunscreen lotions.

Step 2: Key Formula or Approach:
Sunscreens require active ingredients that can effectively block, reflect, or scatter harmful Ultraviolet (UV-A and UV-B) radiation from the sun to protect the skin.

Step 3: Detailed Explanation:
Metal nanoparticles like Gold (Au), Platinum (Pt), and Palladium (Pd) are primarily used in catalysis or advanced electronics, not in cosmetics.
Titanium dioxide ($\text{TiO}_2$) and Zinc oxide (ZnO) are semiconductor oxides that are highly effective at absorbing and scattering UV light.
When reduced to nanoparticles (nanoscale size), $\text{TiO}_2$ becomes completely transparent to visible light, eliminating the white, chalky residue older sunscreens used to leave on the skin, while retaining its powerful UV-blocking properties.

Step 4: Final Answer:
Sunscreen lotions contain nanoparticles of $\text{TiO}_2$, corresponding to option (C).