INTRODUCTION Definition: nanotechis the study of the control of matter on an atomic and molecular scale. Nanotechnology uses techniques, processes and materials at the supramolecular level, approximately in a range between 1-100 nanometers (nm), in order to create new properties and to stimulate particular desired functionalities.
Carbon nanotubes Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube might be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to several millimeters in length (as of 2008). Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp2 bonds for sp3bonds, giving the possibility of producing strong, unlimited-length wires through high-pressure nanotube linking. Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. There are two models which can be used to describe the structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g. a (0,8) single-walled nanotube (SWNT) within a larger (0,10) single-walled nanotube. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.3 Å (330 pm).
Different types of carbon nanotubes Single walled Multi walled
Application of carbon nanotubes Carbon Nanotubes in Batteries and Capacitors Carbon Nanotubes in Fuel Cell Applications carbon nanotubes with biological systems can significantly improve medical science — especially diagnostics and disease treatment. Carbon nanotubes and graphene exhibit extraordinary electrical properties for organic materials, and have a huge potential in electrical and electronic applications such as sensors, semiconductor devices, displays, conductors and energy conversion devices (e.g., fuel cells, harvesters and batteries). Carbon Nanotubes May Exhibit High Thermal Conductivity
Molecular manufacturing molecular manufacturing, is a term given to the concept of engineered nanosystems (nanoscale machines) operating on the molecular scale. It is especially associated with the concept of a molecular assembler, a machine that can produce a desired structure or device atom-by-atom using the principles of mechanosynthesis. molecular manufacturing also has the potential to revolutionize medicine. For example, sensors that are smaller than blood cells could be produced inexpensively. When released into a patient's blood stream in large numbers, these sensors could provide very accuratediagnoses. Nanorobots could be built using molecular manufacturing to perform surgicalprocedures in a more precise way.
Nanomaterials Nanomaterials is a field which takes a materials science-based approach to nanotechnology. It studies materials with morphological features on the nanoscale, and especially those which have special properties stemming from their nanoscale dimensions. Nanoparticles or nanocrystals made of metals, semiconductors, or oxides are of particular interest for their mechanical, electrical, magnetic, optical, chemical and other properties. Nanoparticles have been used as quantum dots and as chemical catalysts.
Properties of nanomaterials large fraction of surface atoms high surface energy spatial confinement reduced imperfections high Young’s modulus and high tensile strength improve adhesion, durability, and abrasion resistance extreme high thermal conductivity in axial directions,leaving high anisotropy in the heat transport in the materials
Application of nanomaterials Sunscreens and Cosmetics : Nanosized titanium dioxide and zinc oxide are currently used in some sunscreens, as they absorb and reflect ultraviolet (UV) rays and yet are transparent to visible light and so are more appealing to the consumer. Composites : An important use of nanoparticles and nanotubes is in composites, materials that combine one or more separate components and which are designed to exhibit overall the best properties of each component. This multi-functionality applies not only to mechanical properties, but extends to optical, electrical and magnetic ones Phosphors for High-Definition TV Elimination of Pollutants High-Sensitivity Sensors
Nanotechnology in Medicine Employing nano-particles to deliver drugs, heat, light or other substances to specific cells in the human body. . Engineering particles to be used in this way allows detection and/or treatment of diseases or injuries within the targeted cells, thereby minimizing the damage to healthy cells in the body. Development nanocrystalline silver is already being used as a antimicrobial agent in the treatment of wounds Nanotubes used in broken bones to provide a structure for new bone material to grow. Nanoparticles that can attach to cells infected with various diseases and allow a doctor to identify, in a blood sample, the particular disease. Nanoshells that concentrate the heat from infrared light to destroy cancer cells with minimal damage to surrounding healthy cells. For a good visual explanation of nanoshells
Water Pollution & Nanotech Used as a cleaning agent Use deionization method using electrodes to remove salt or metals from water removes virus cells from water using filters
Energy and Nanotechnology Used in fuel cells Nanotechnology is being used to reduce the cost of catalysts used in fuel cells to produce hydrogen ions from fuel such as methanol and to improve the efficiency of membranes used in fuel cells to separate hydrogen ions from other gases such as oxygen. Used in solar cells
Nanotechnology and Space nanosensors and nanorobots could improve the performance of spaceships, spacesuits, and the equipment used to explore planets and moons nanomaterials make lightweight solar sails and a cable for the space elevator Using carbon nanotubes to make the cable needed for the space elevator, a system which could significantly reduce the cost of sending material into orbit
Food and Nanotechnology Nanotechnology is having an impact on several aspects of food science, from how food is grown to how it is packaged,that will make a difference not only in the taste of food, but also in food safety, and the health benefits that food delivers. Clay nanocomposites are being used to provide an impermeable barrier to gasses such as oxygen or carbon dioxide in lightweight bottles, cartons and packaging films Storage bins are being produced with silver nanoparticles embedded in the plastic. The silver nanoparticles kill bacteria from any material that was previously stored in the bins, minimizing health risks from harmful bacteria.