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Nanometirals
- 1. NANOMATERIALS Dr. S. Sreenivasa AssociateProfessor and Chairman DOS and R in Organic Chemistry Tumkur University, Tumakuru
- 2. Size Dependent Propertiesof Nanomaterials Why materials in the nano range alone are having so much importance? • Nanomaterials exhibit distinctively different physical properties. • In nanoscale range a material will show different properties when the size is slightly varied. • Transition from atoms or molecules to bulk form takes place in nano scale range. • Nanomaterials are governed by quantum mechanics rather than Newtonian physics
- 3. (A) Surface Area Aninteresting comparison… Surface area of a cube with side length 1m = 6m2 This cube may be cut into 1027 cubes (each with a volume of 1nm3), then the collective surface area = 6000 km2. Properties influenced by surface area Catalytic Activity Gas Adsorption Chemical Reactivity
- 4. (B) Electrical Properties •Electronic bands in bulk materials are continuous whereas it is discrete in nanomaterials • The separation between different electronic states varies with the size of nanomaterial Therefore a conductor in bulk may become semiconductor or
- 5. (C) Optical Properties Nanomaterialsexhibit unique colours Electronic transition among the discrete electronic states Scattering of light Surface Plasmon Resonance (SPR) o When light falls on a metal surface plasmons start oscillating in a synchronised manner – SPR o Resonating electrons have much higher cross sectional area than the nanoparticle. o Resonating electrons capture radiation of different wavelength depending on oscillation frequency.
- 6. Synthesis Top-down Sputtering, pulsed laserdeposition, laser ablation, high energy ball milling, electric arc method, nanolithography, ion-beam implantation Expensive catalyst, surface defects, contamination Bottom-up Sol-gel, precipitation, gas condensation, CVD, hydrothermal & thermolytic process Simple and cost effective, control over chemical composition, less defects and high purity
- 7. Precipitation Method Precipitation fromsolution Steps: i) Nucleation ii) Growth of Particles Precursors – metal salts eg. Zinc Acetate To the precursor solution acid or base is added to obtain desired pH. A precipitating agent (eg. TAA)is added It also causes supersaturation of the solution due to the added ions. Nucleus formation commences at this stage. Nucleus further grows into particles and gets precipitated The precipitate is filtered, washed with water, air dried and finally calcined to remove counter anions.
- 8. Advantages • Particle size,crystallinity and morphology can be controlled by varying concentration, temperature, pH and rate of addition of reagents and mixing processes. • If the solution attains supersaturation slowly then larger particles are formed. • Simple and rapid preparation.
- 9. Fullerene Third allotropic formof carbon Consists of hexagonal and alternate pentagonal rings Fullerene with 60 C atoms – with 12 pentagons and 20 hexagons is called Buckminster fullerene. First Isolated from soot of chimneys.
- 10. 100 nm Characteristcs Requireshigh energy to break (10000C). Insoluble in water soluble in toluene and CS2. It is not toxic but its derivatives are toxic. Applications • Powerful antioxidants • Used as FED’s replacement for LCD and plasma • Blended with polymers can be used in photovoltaics. • Used as catalyst, in water purification and in fuel cells
- 11. Carbon Nanotubes • Theyare called bucky tubes • Posses high strength • Types SWCNT’s and MWCNT’s
- 12. Characteristcs Tensile strength ofCNT is greater than carbon steel. In hardness scale it is harder than diamond and boron nitride. CNT s are having high thermal conductivity along the material compared to copper. Shows high thermal insulation along the axis.
- 13. Nano wires andNano rods Figure: Silver nanowires Figure: ZnO nanorods
- 14. • Depending uponthe size and diameter they are nano wires (dia-1nm) and nanorods (dimension 100-nm) Applications In electronics and optics. Used as rectifiers, diodes, transistors and LED’s Nanorods are used in display technology (change in reflectivity with change in orientation. Nanorods are selectively absorbed by cancer cells and heated in IR They used in energy harvesting
- 15. • Depending uponthe size and diameter they are nano wires (dia-1nm) and nanorods (dimension 100-nm) Applications In electronics and optics. Used as rectifiers, diodes, transistors and LED’s Nanorods are used in display technology (change in reflectivity with change in orientation. Nanorods are selectively absorbed by cancer cells and heated in IR They used in energy harvesting
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- 17. • Dendrimer ingreek means tree like structure. • Molecules forming tightly packed ball like structure resulting in low viscosity. • Because of presence of large surface groups they act as catalysts. • Because of presence of cavity used in selective reaction as sieves (Host – guest) Applications Invitro diagnosis of cardiac problems Contrasting agents in MRI Target delivery drugs Used as proton sensors