NANOPARTICLES USING SOL GEL SCIENCE

Contracted nanoparticle aggregates which is vibrating ( seen as a Blur) at one side of the cabon film after disconnecting from the other side.

 Such systems can be translated from solution into two demensional representations on glass surfaces via methods such as dip coating.

 In essense, the fractal nature can still be seen but in a two demensional film

Sol- Gel Dipping Apparatus

Low density coating of SiO2 via Sol-gel Dip Coating method

 The reaction going to completion first in solution to form a sol is one way to do sol gel dip coating  Another way is to allow the reaction to be incomplete or still proceed after dipping.

Sol-Gel Dip Coatings 1 to 10 Layers One Layer Two Layers AL doped ZnO layers Five Layers Ten layers

Demostration Experiments  Sol-Gel Synthesis via TMOS  Sol-Gel Synthysis using Sodium silicate better known as furnace cement.

 Ultrasonic synthesis of TMOS

Mix the reactives SOL-GEL SCIENCE Hydrolysis and Condesation reactions take place Sol Gelification Aging Gel  Gelification  Aging  Soaking Drying Gel Aerogel

Gelification Mix reactives OR OR OR Si OR + H 2 O OR Hydrolysis and Condesation OR OR reactions take place Si OR OR + H O OR Si OR Sol OR OR OR Si OR OH + H O OR Si OR Gelification OR H O OR Si OR + ROH OR OR OR Si O Si OR OR OR + ROH OR OR OR Si O Si OR OR OR + H 2 O Aging Gel Gel

Designing Nanomaterials First Step

Silica Solution

Precursor: Tetraetilortosilicate Si(OCH 2 CH 3 ) 4 Solvent: Ethanol Catalyst: OxalicAcid Modifications

pH (final product)

Temperature (crystal phase) Precursor (Type of material) Time (Strength) etc

D E S I G N I N G

Time vs pH 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 6  Shrinkage 7 Gel 8   

V

9

pH

Precipitation 10 11 No gel formation 12

Aging Once there is a gel, chemical reactions still keep taking place. These further reactions add strength to the solid network.

Gel Stronger Gel Aging

Aerogeles y Xerogeles Special Drying Tecniques Aerogel Gel Evaporation Xerogel

Synthesis of Titania  Up to now many methods have been established for the synthesis of titania. The sol-gel technique being the most important  Unfortunately, the sol-gel technique derived precipitates are amorphous in nature which requires further crystalline phase.

treatment to form

Sol Gel Preparation of Anatase TiO2 NanoParticles  When done under controlled conditions size of particle can be reduced to < 10 nm  Controlling Hydrolysis and concentration is a must.

 Important in our work for constructing highly active nanocrystalline photocatalysts.

Ti(OET) 4 + H 2 O(excess) Precipitate Acid No Anatase < 70% Rutile >30 Forms gel No Yes Heat Yes Anatase + Trace Brookite Forms gel Heat Yes Anatase + Trace Brookite no gel No Anatase =70% Bookite =30 no gel

Selective synthesis with Ultrasound.

IRON OXIDE Particles Stabilized with Oleic Average diameter = 8 nm