Zinc oxide particles, photostable uv filters, and methods of use thereof

Zinc oxide particles, wherein the particles have:

• an O:Zn ratio of at least 0.99,
• an average particle size of 10 to 300 nm using laser light scattering,
• the particles have a ΔE value of at most 10 in a DPPH Photocatalytic Stability Test,
• the particles have a ΔE value of at least 15 in a Dispersion Color Test,
• wherein the ΔE value in the DPPH Photocatalytic Stability Test is calculated as:
• Δ
• ⁢
• E
• =
• (
• L
• 2
• *
• -
• L
• 1
• *
• )
• 2
• +
• (
• a
• 2
• *
• -
• a
• 1
• *
• )
• 2
• +
• (
• b
• 2
• *
• -
• b
• 1
• *
• )
• ⊥
• 2
• wherein L2*, a2*, and b2* are the color coordinates of a zinc oxide particle test mixture post irradiation and where L1*, a1*, and b1* are the initial color coordinates of the zinc oxide particle test mixture prior to irradiation;
• and
• wherein the ΔE in the Dispersion Color Test is calculated as:
• Δ
• ⁢
• E
• =
• (
• L
• 2
• *
• -
• L
• 1
• *
• )
• 2
• +
• (
• a
• 2
• *
• -
• a
• 1
• *
• )
• 2
• +
• (
• b
• 2
• *
• -
• b
• 1
• *
• )
• ⊥
• 2
• wherein L2*, a2*, and b2* are the color coordinates of a zinc oxide particle test sample and wherein L1*=99.47, α1′=−0.16, and b1*=−0.17 correspond to color coordinates of a white reference tile.