Nanobiotechnology lecture 2
- 1. Manipulating molecules: The scanning probe Microscopes Nanotechnology is envisioned to make smaller and smaller tools in order to manipulate atoms and molecules. Scanning tunneling microscope (STM) and atomic force microscope (AFM) Both are different from conventional microscopy which is based on construction of images by using beam of electron or photons (in case of electron microscope). STM & AFM microscopes are based on very fine scanning of the sample surface using an ultrafine tip.
- 3. The image formed is based on the electrical tunneling properties of the matter as in the case of STM or the topographical properties of the sample as in the case of AFM. The generic name for such sort of microscopes is called as a scanning probe microscope (SPM). The tip or probe scans over the surface of the sample and measures a tunneling current (in case of STM) or the physical topography of the surface (in case of AFM). Principally, the specifications of the scanning probe machine allow us to reach a single atom resolution and atomic organization of metallic substrates.
- 4. Carbon Fullerene: A new form of Carbon Organic compounds are based on carbon as a key building block. 1/5 of human body I is carbon, more than any element except oxygen. Biological entities like proteins and lipids are organic compounds as well common industrial products such as nylon, plastic etc Synthetic abilities in organic chemistry in terms of complexity and scale up process are enormous.
- 5. Carbon exists in three allotropic forms i.e amorphous, graphite and diamond. Diversity of carbon organization at molecular level shows graphite is the softest substance and diamond is the hardest. Molecular organization of the carbon can dramatically affect its macroscopic properties.
- 6. Carbon Fullerene Vaporization of graphite by using laser into new cluster forms of carbon are called carbon fullerenes. They are in the form of closed cage molecules in the arrangement of hexagonal and pentagonal faces. Common and stable cluster is buckministerfullerene. It is a 60 carbon atoms spheroidal molecule like a bucky ball. C60 fullerene is the most abundant cluster of carbon atoms found in carbon soot. It is about 0.7 nm and has excellent electrical and heat conductivity.
- 8. Applications of Carbon Fullerene oServing as nanocontainers for drug delivery. oCould serve as antiviral agents. oModified C60 molecule can effectively inactivate HIV at low micromolar concentrations.
- 9. Carbon nanotubes: Key building blocks for future nanotechnological application Elongated variants of the C60 fullerenes. Resembles graphite sheets wrapped around into elongated cylinders with or without capping at their ends. Their length to width ratio is extremely high. Can be formed in a single shell called as single walled nanotubes (SWNTs) Or in multiwall fashion known as multiwalled nanotubes (MWNTs) They have unique mechanical and electrical properties
- 10. Have ten time more tensile strength than steel. Thus are suitable candidate materials for development of ultra strong materials like in construction of car and aviation industries. Can be used as a source of fabrics and clothing for making lightweight bulletproof fabrics. Can be used in assembly of an ultra strong cable in construction of space elevator. Being very small and highly conductive carbon nanotubes can be used as molecular wires, conductive composites and interconnects.
- 11. Graphene A single layer of carbon which is one atom thick is called graphene. It has high thermal and electrical conductivity and is mechanically very strong yet strechable material. Being transparent and very conductive it can be used in liquid crystal displays and solar cells etc.
- 12. The inorganic nanomaterials The noncarbon nanotubes made by inorganic material which resemble like the carbon fullerene structures. Tungsten, molebdenum etc can form 2D layer rearrangements as evidenced in graphite structures for making nanotube. The structures that have formed in a cage fashion can be rolled to form fullerene like structures. For instance the nano particles of the layered WS2 compound can form closed cage structures that are similar in their molecular organization to carbon fullerenes.
- 13. Used in many industrial and technological applications. as a solid lubricant Increases the life span and efficiency of motors and other power tools with motor parts Used as additives for motor oil. Used as lubricants of medical and dental devices.
- 14. Quantum Dots The nano objects consist of semiconductor materials surrounded by a shell composed of ZnS or CdS. Also called as nanocrystals and have dimensions of few nm to a few tens of nanometers. Serve as a cage for electrons and the molecular diameters of these structures reflect the number of electrons they contain. The size may depends from a single electron to a collection of several thousands.
- 15. Quantum dot behave like a giant atom. Energy levels in a given quantum dot become quantized due to confinement of electrons. The band gap b/w the two energetic states determines the energy of a photon that is being emitted by the transition b/w the two states The energy can be either in the visible or the infrared region depending on the specific band gap