Nanotechnology in sunscreen uv protection
Nanotechnology in sunscreen uv protection, sunscreen, uv protection
Published on: Mar 3, 2016
Transcripts - Nanotechnology in sunscreen uv protection
NANOMATERIALS IN SUN-SCREEN
A. POOJA SHUKLA
Nanoparticles are one-twentieth the thickness of a human hair.
Nanoparticles are smaller than 100 nanometres and invisible to
the human eye – a nanometre is 0.000001 millimetre.
Microfine particles are smaller than those used in conventional
white zinc sunscreens, however are larger than nanoparticles –
usually in the range of 100 to 2500 nanometres.
is already making today’s products:
WHAT ARE SUN RAYS…??
The sun emits several kinds of electromagnetic radiation: Visible (Vis), Infrared (IR)
and Ultra Violet (UV)
Each kind is distinguished by a characteristic wavelength, frequency and energy
Higher energy radiation can damage our skin
The kind of skin damage is determined by the size of the
energy packet ( E = h x f)
The UV spectrum is broken into three parts:
Very High Energy (UVC)
High Energy (UVB)
Low Energy (UVA)
• As far as we know, visible and IR radiation don’t harm the
• Very high energy radiation (UVC)
is currently blocked by the ozone
layer (ozone hole issue)
• High energy radiation (UVB) does
• But lower energy radiation (UVA)
can penetrate deeper into the skin,
leading to long term damage
SUN RADIATION SUMMARY
(high l IR)
(<1% of all UV)
(5% of all UV)
(95 % of all UV)
NANOPARTICALS IN SUN-SCREEN
The nanoparticles used in sunscreens
and other consumer products may have
novel biological and physical properties,
which can lead to unusual effects – both
good and bad.
Nanoparticles found in sunscreens are
either titanium dioxide or zinc oxide.
WHY USE SUN-SCREEN….??
Too much unprotected sun exposure leads to:
Premature skin aging (e.g. wrinkles)
WHY NANOMATERIALS IN SUN-
Sunscreens made with zinc oxide and titanium dioxide
generally score well because:
they provide strong sun protection with few health concerns
they don’t break down in the sun
zinc oxide offers good protection from UVA rays – titanium
oxide less so, but better than most other active ingredients.
Inorganic UV Filters
dioxide (TiO2) and zinc oxide (ZnO) pigments are
commonly used in personal care products to provide protection
against UVA and UVB
They attenuate UV light by absorption and scattering
They are usually surface coated to minimize photo-catalytic activity.
are typically produced as finer crystals from the same feed
stocks and with similar processes as pigmentary grades.
Manufacturing is a two step process :
The production of TiO and ZnO
1. Purification of the raw material
2. Growing of crystals (primary particles) of the desired size
They are two different processes for TiO2, known as sulfate and chloride,
and three for ZnO, known as American, French and Wet.
Crystals are grown at high temperatures to the required sizes : 200 nm and
above (pigmentary grades) and finer than 200 nm (attenuation grades).
Surface Treatment of Inorganic UV Filters
(primary particle size)
Attenuation grade TiO2
(30 - 50 nm)
Attenuation grade ZnO
(15 - 35 nm)
M. Kobayashi and al., Cosm & Toil., Vol. 112, No. 6, p83, 1997
* Rate constant of the first order reaction of oxydation of acetalydehyde
It is common industry practice to use surface treated inorganic UV filters when
Attenuation of UV light is influenced by particle size.
Scattering of visible light (whitening effect) is influenced by particle
size and the difference between the refractive index of the pigment
and the surrounding media.
Maximum scattering occurs when size equals 1/2 the wavelength and
particles are uniformly dispersed (Mie theory).
TiO2 Dispersions in Cyclopentasiloxane
10nm TiO2 (110 nm dispersion particle size) makes transparent dispersions for all skin
All dispersions diluted in Cyclopentasiloxane (to 20% TiO2)
Particle Size and UV attenuation
UVB / UVA
100 - 120 nm
7.0 - 8.0
120 - 150 nm
3.4 - 5.5
11 - 55
130 - 160 nm
150 - 180 nm
1.5 - 2.0
7 - 17
> 250 nm
130 - 180 nm
1.0 - 1.1
30 - 37
180 - 250 nm
> 250 nm
308/360 extinction ratio : indication of UVB/UVA balance
(2) 308/524 extinction ratio : indication of transparency
70 - 90
Attenuation grade Titanium Dioxide and Zinc Oxide are produced
using the same processes as larger pigmentary grades. They are
usually surface coated to minimize their photo-catalytic activity.
TiO2 and ZnO attenuate UV light according to their particle size :
Small primary particle sizes (10 - 15 nm) are necessary to produce
dispersions (100 - 150 nm) transparent to visible light and efficient
ZnO and larger TiO2 (35 - 150 nm) are more efficient against
The particle size of pigmentary grades are appropriate to scatter
visible light, but they are not efficient at attenuating UV light or
effective as sunscreens.
With all of this possible damage, it pays
to wear sunscreen, but which one should
Do the shape and size of the particles affect sun protection?
Yes. The smaller they are, the better the SPF protection and the worse the UVA
protection. Manufacturers must strike a balance: small particles provide greater
transparency but larger particles offer greater UVA protection. The form of zinc
oxide most often used in sunscreens is larger and provides greater UVA protection
than the titanium dioxide products that apply clear on the skin.
Do the nanoparticles in sunscreen penetrate the skin?
No. Some studies indicate that nanoparticles can harm living cells and organs, but
there is no evidence that zinc oxide and titanium dioxide nanoparticles penetrate
skin in any significant quantities.
Could nanoparticles that penetrate the skin cause skin damage when
energized by sunlight?
Possibly but unlikely, since the materials don’t penetrate deep enough in skin to
reach living skin cells.
Blocks UVA and UVB radiation
Full SPF protection
Protects from SKIN RASHES
Avoids SKIN CANCER
Avoids SKIN AGING
Twenty different skin cancer lesions
Images : source internet
Nano-ingredients in sunscreen, The need for regulation, july 2012
Nanotechnology and cosmetics, November 2008