PowerPoint Presentation

Properties of Nanochemistry.

[Audio] SIZE DEPENDENT PROPERTIES: Strength Toughness Hardness Ductility Surface area Density Conductivity Elasticity Melting point INCREASES DECREASES It is composed of grains and grain boundaries. Nanometre sized grains countains few thousands of atoms. As grain size decreases, then significant increases in the volume of grain boundaries. Important properties of nanomaterials: 1.Electrical property 2.Optical property 3.Mechanical property 4.Magnetic property 5.Melting point 6.Surface area 7.Chemical reactivity.

[Audio] Electrical properties:  It decreases due to increased surface scattering.  It can be increased due to better ordering in micro-structure.  When converting into nano-material the electrical property decreases for semi-conductors and increases for metal.  Reson due to high energy gap in semiconductors are confinesd but it makes electron continuous.  Example: ~Polymeric fibres. ~Used as separator plates in batteries, because they can hold many energy. ~Nickel-metal hydride batteries, require for less frequent recharging and last much longer..

[Audio] Optical properties:  Any material is said to be optical when they have absorption of light or reflection of light.  They are different from bulk forms.  Examples: GOLD Red colour Yellow colour Frequency differs, Wavelenght differs, Colour differs..

[Audio] Mechanical property:  The nano-materials have less defects compared to bulk materials.  It increase the mechanical strength.  Polymeric material can be increased by the addition of nano-fillers.  Nano-materials are stronger,harder and corrosion resistant.  Example: Used in spark plugs. Nano-crystalline carbides are much stronger,harder. Used in micro drills..

[Audio] Magnetic properties:  Nano-material are more magnetic compared to bulk.  Even non-magnetic solid shows magnetic properties when compared into nano.  Diamagnetism- paired electron/ slightly repelled/no magnetism when removed from magnetic field.  Paramagnetism - unpaired electron/weakly attracted/no magnetism when removed from magnetic field.  Ferromagnetism-strongly attracted. For example iron become magnetised in MG field.  Super paramagnetism – when bulk particles converted into nano the magnetic property become super paramagnetism.  Note: Paramagnetism is stronger than diamagnetism but weaker than ferromagnetism..

[Audio] Melting point When bulk is converted into melting point decreases. Surface area When bulk is converted into nano surface area increases. Chemical reactivity When bulk is converted into nano chemical reactivity increases..

Types of nano materials.

[Audio] Types Nanoparticles Nanocluster Nanowire Nanorods Nanotubes.

[Audio] Nanoparticales  Size ranges from 1 to 100 nm.  Tiny aggregates of atom.  Smaller than crystals.  Bigger than molecules.  Examples: TiO2,gold,silver,ZnO2,etc., Properties: » They have anti-reflective properties. » High % of atoms. » High catalytic activity. » Low melting point. Applications: Hard coatings on eye glasses. Cosmetics. Industrial catalyst Used in medicine. Bone cement. Surgical instruments..

[Audio] Nanocluster  Size ranges from 0.1 to 10 nm.  Fine aggregates of atoms.  It is the Smallest sized nano material.  Because of their close packing arrangement of atoms.  Examples: CdS,ZnO,etc., Properties: » Atomic (or) molecular clusters are formed. » Size decrease. » So, reactivity also decrease. » Melting point are lower than bulk. » Electron is more confined. Applications: Catalysts in many reactions. In chemical sensors. LED in quantum computers..

[Audio] Nanorods  Size ranges from 1 to 100 nm.  It is one dimensional.  Length to width ratio less than 20.  Examples: ZnO, CdS, GaN. Properties: » It exhibits optical and electrical properties. » Target cell. Applications: Catalysts in many reactions. In chemical sensors. LED in quantum computers..

[Audio] Nanowires  Size ranges from 10 to 100 nm.  It is one dimensional.  It is cylindrical solid material.  Length to width ratio greater than 20.  Examples: TiO2,gold,silver,ZnO2,etc., Properties: » Conductivity is less. » It exhibits optical,chemical,thermal and electrical properties. » Large surface area. » Emits photoluminescence Applications: Data storage(or) transfer. Used to prepare active components. Important role in future of digital computing. In Batteries and generators. Synthesis of Nanowires Template-assisted synthesis VLS method (Vapour-Liquid-Solid).

[Audio] Nanotubes  Size ranges from 1 to 100 nm.  Length of few nm to microns.  It is tiny cylindrical carbon material.  It may be organic or inorganic. Examples Carbon nanotube Silicon nanotube DNA nanotubes Boron nitride nanotube Carbon nanotubes: Size ranges from 1-3 nm. Carbon is solid state. It exits in allotropic forms like graphite, diamond, fullerence and nano tubes. It is a tubular form of carbon. When graphite sheets are rolled into cylinder, their edges join each other to form nanotubes. Each CNT are linked by covalent bonds. CNT aligned as ropes held together by weak vander walls forces..

[Audio] Single-walled nanotubes (SWNTs) Multi-walled nanotubes (MWNTs) One tube of graphite Multiple layers of graphite rolled to form tube shape Exhibit electrical properties. It is an excellent conductor. Exhibit both metallic and semiconducting properties Thick of one atom is 2 nm and length of 100 μm. Nested nanotubes Based on the orientation of hexagon lattice, nanotubes resulted into three kinds, 1.Arm chair- lines are parallel to the axis of the nanotube. 2.zig-zag structures- line are down the centre. 3.Chiral nanotubes: it exhibits twist (or) spiral around the nanotubes. Note: arm-chair CNT are metallic while zig-zag and chiral nanotubes are semiconducting. Uses: For storing fuels such as hydrogen and methane. Types of carbon nanotubes.