NANO TITANIUM DIOXIDE

1.        What is Nano Titanium Dioxide?

Titanium dioxide occurs in nature as well-known minerals rutile, anatase and brookite, and
additionally as two high pressure forms, a monoclinic baddeleyite-like form and an
orthorhombic α-PbO2-like form. The most common form is rutile, which is also the most
stable form. Anatase and brookite both convert to rutile upon heating. Rutile, anatase and
brookite all contain six coordinated titanium.

Titanium dioxide has eight modifications - in addition to rutile, anatase and brookite there
are three metastable forms produced synthetically (monoclinic, tetragonal and orthorombic),
and five high pressure forms (α-PbO2-like, baddeleyite-like and cotunnite-like):





















2.        Physical Properties of Nano Titanium Dioxide.


















3.        Some of the Major Applications of Nano Titanium Dioxide.

Pigment

Titanium dioxide is the most widely used white pigment because of its brightness and very
high refractive index (n = 2.7), in which it is surpassed only by a few other materials.
Approximately 4 million tons of pigmentary TiO2 are consumed annually worldwide. When
deposited as a thin film, its refractive index and colour make it an excellent reflective optical
coating for dielectric mirrors and some gemstones, for example "mystic fire topaz". TiO2 is
also an effective opacifier in powder form, where it is employed as a pigment to provide
whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods,
medicines (i.e. pills and tablets) as well as most toothpastes. Opacity is improved by optimal
sizing of the titanium dioxide particles.

Used as a white food colouring, it has E number E171. Titanium dioxide is often used to
whiten skimmed milk; this has been shown statistically to increase skimmed milk's
palatability.

In cosmetic and skin care products, titanium dioxide is used both as a pigment and a
thickener. It is also used as a tattoo pigment and styptic pencils.

This pigment is used extensively in plastics and other applications for its UV resistant
properties where it acts as a UV absorber, efficiently transforming destructive UV light
energy into heat.

In ceramic glazes titanium dioxide acts as an opacifier and seeds crystal formation.

In almost every sunscreen with a physical blocker, titanium dioxide is found because of its
high refractive index, its strong UV light absorbing capabilities and its resistance to
discolouration under ultraviolet light. This advantage enhances its stability and ability to
protect the skin from ultraviolet light. Sunscreens designed for infants or people with
sensitive skin are often based on titanium dioxide and/or zinc oxide, as these mineral UV
blockers are believed to cause less likely skin irritation than chemical UV absorber
ingredients. The titanium dioxide particles used in sunscreens have to be coated with silica or
alumina, because titanium dioxide creates radicals in the photo catalytic reaction. These
radicals are carcinogenic, and could damage the skin.

Titanium dioxide is used to mark the white lines on the tennis courts of the All England Lawn
Tennis and Croquet Club, best known as the venue for the annual grand slam tennis
tournament The Championships, Wimbledon.

As a photocatalyst

Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet light.
Recently it has been found that titanium dioxide, when spiked with nitrogen ions, or doped
with metal oxide like tungsten trioxide, is also a photocatalyst under visible and UV light.
The strong oxidative potential of the positive holes oxidizes water to create hydroxyl
radicals. It can also oxidize oxygen or organic materials directly. Titanium dioxide is thus
added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and
anti-fouling properties and is also used as a hydrolysis catalyst. It is also used in the Graetzel
cell, a type of chemical solar cell.

The photocatalytic properties of titanium dioxide were discovered by Akira Fujishima in
1967 and published in 1972.The process on the surface of the titanium dioxide was called the
Honda-Fujishima effect. Titanium dioxide has potential for use in energy production: as a
photocatalyst, it can carry out hydrolysis; i.e., break water into hydrogen and oxygen. Were
the hydrogen collected, it could be used as a fuel. The efficiency of this process can be greatly
improved by doping the oxide with carbon.

Titanium dioxide can also produce electricity when in nanoparticle form. Research suggests
that by using these nanoparticles to form the pixels of a screen, they generate electricity
when transparent and under the influence of light. If subjected to electricity on the other
hand, the nanoparticles blacken, forming the basic characteristics of a LCD screen. According
to creator Zoran Radivojevic, Nokia has already built a functional 200-by-200-pixel
monochromatic screen which is energetically self-sufficient.

In 1995 Fujishima and his group discovered the superhydrophilicity phenomenon for
titanium dioxide coated glass exposed to sun light. This resulted in the development of self-
cleaning glass and anti-fogging coatings.

TiO2 incorporated into outdoor building materials, such as paving stones in noxer blocks or
paints, can substantially reduce concentrations of airborne pollutants such as volatile organic
compounds and nitrogen oxides.

A photocatalytic cement that uses titanium dioxide as a primary component, produced by
Italcementi Group, was included in Time's Top 50 Inventions of 2008.

TiO2 offers great potential as an industrial technology for detoxification or remediation of
wastewater due to several factors.

1. The process occurs under ambient conditions very slowly, direct UV light exposure
increases the rate of reaction.
2. The formation of photocyclized intermediate products, unlike direct photolysis
techniques, is avoided.
3. Oxidation of the substrates to CO2 is complete.
4. The photocatalyst is inexpensive and has a high turnover.
5. TiO2 can be supported on suitable reactor substrates.

Other applications

TiO2 is also used in resistance-type lambda probes (a type of oxygen sensor).

Titanium dioxide is what allows osseointegration between an artificial medical implant
and bone.

Titanium dioxide in solution or suspension can be used to cleave protein that contains the
amino acid proline at the site where proline is present. This breakthrough in cost-effective
protein splitting took place at Arizona State University in 2006.

Titanium dioxide on silica is being developed as a form of odor control in cat litter. The
purchased photocatalyst is vastly cheaper than the purchased silica beads, per usage, and
prolongs their effective odor-eliminating life substantially.

Titanium dioxide is also used as a material in the memristor, a new electronic circuit
element. It can be employed for solar energy conversion based on dye, polymer, or quantum
dot sensitized nanocrystalline TiO2 solar cells using conjugated polymers as solid electrolytes.

It has also been recently incorporated as a photocatalyst into dental bleaching products. It
allows the use of decreased concentrations of hydrogen peroxide in the bleaching agent, thus
claimed to achieve similar bleaching effects with fewer side effects (e.g. transient sensitivity,
change in tooth surface topography, etc.)

It is also used by film and television companies as a substitute for snow when filming scenes
which require a winter setting.

Synthetic single crystals and films of TiO2 are used as a semiconductor, and also in Bragg-
stack style dielectric mirrors due to the high refractive index of TiO2 (2.5 – 2.9).