Introduction to Nanotechnology PDF

CHAPTER 9 Introduction to Nanotechnology 104 Learning objectives By the end of this chapter, the student should be able to: Define Nanotechnology, Classify the materials at nanoscale and list the fabrication techniques of nanostructures. Definition The creation of functional materials...

CHAPTER 9 Introduction to Nanotechnology 104 Learning objectives By the end of this chapter, the student should be able to: Define Nanotechnology, Classify the materials at nanoscale and list the fabrication techniques of nanostructures. Definition The creation of functional materials, devices and systems through control of matter on the nanometer length scale (1 -100 nm), and exploitation of novel phenomena and properties (physical, chemical, biological) at that length scale. The size range that holds interest in nanotechnology is from 100nm to approximately 0.1-0.2nm (atomic level). In this range, materials can have different or enhanced properties such as; reactivity, strength, electrical and optical characteristics compared with the same materials at a larger size. 105 What is different about the nanoscale? An increased surface area to volume ratio Nanomaterials have an increased surface area to volume ratio compared to bulk materials i.e. As the particle size decreases, a greater proportion of the atoms are found on the surface compared to those inside. Thus materials within the nanoscale become highly reactive. Dominance of electromagnetic forces Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized particles. Because the mass of nanoscale objects is so small, gravity becomes negligible. On the other hand, electromagnetic force is a function of charge and distance, so it can be very strong even when we have nanosized particles. Importance of quantum mechanical models Nanomaterials are closer in size to single atoms and molecules than to bulk materials. Thus, classical mechanical models that we use to understand matter at the macroscale cannot be used for the very small (nanoscale) and the very fast (near the speed of light) nanomaterials. Quantum mechanics better describes phenomena that classical physics can't. Quantum mechanics is a scientific model that was developed for describing the motion and energy of atoms and electrons. 106 Random molecular motion While random molecular motion (molecules moving around in space, rotating around their bonds, and vibrating along their bonds) is present for all particles, at the macroscale this motion is very small compared to the sizes of the objects and thus is not very influential in how object behave. On the nanoscale however, these motions can be on the same scale as the size of the particles and thus have an important influence on how particles behave. Nanoscale Approaches and Fabrication Top-down Approaches Bottom-up Approaches Create smaller objects using Larger objects They arrange smaller components in to more complex. Uses principles of molecular recognition Layer-by-layer self assembly Classification of nanomaterials according to dimensionality: 107