BioNanotechnology BME 4215 Dr Md Sherajul Islam Professor
Bio-Nanotechnology BME 4215 Dr. Md. Sherajul Islam Professor Department of Electrical and Electronic Engineering Khulna University of Engineering & Technology Khulna, Bangladesh
LECTURE - 1 Basic Concepts on Nanotechnology
Two Challenges by Feynman At the meeting Feynman concluded his talk with two challenges, and he offered a prize of $1000 for the first individuals to solve each one First challenge involved the construction of a tiny motor A Nanometer is a molecular or nanoscale device capable of converting energy into movement The second challenge involved the possibility of scaling down letters small enough so as to be able to fit the entire Encyclopædia Britannica on the head of a pin, by writing the information from a book page on a surface 1/25, 000 smaller in linear scale In 1985, Tom Newman, a Stanford graduate student, successfully reduced the first paragraph of A Tale of Two Cities by 1/25, 000, and collected the second Feynman prize Kinesin uses protein domain dynamics on nanoscales to walk along a microtubule.
Nanoscale
Nanoscale A sheet of paper is about 100, 000 nanometers thick, a human hair is around 80, 000 - 100, 000 nanometers wide 6, 000 and 10, 000 nanometers in diameter
Nanotechnology The art and science of manipulating and rearranging individual atoms and molecules to create useful materials, devices, and systems Nanotechnology is defined as the knowledge and management of processes on a scale from 1 to 100 nm and application of object properties on a nanometer scale. Definition for the term nanotechnology was given for the first time by Norio Taniguchi, a professor of Tokyo University, in 1974 in his paper Basic concepts of Nanotechnology, which mentioned “Nanotechnology mainly consists of the processing of separation, consolidation, and deformation of materials by one atom or one molecule. ”
Size Effects -Why does size influence the material’s properties? -How does size influence the material’s performance? -Why are properties of nanoscale objects different than those of the same materials at the bulk scale? -Why nanomaterials are unstable?
Size-dependent properties At the nanometer scale, properties become size-dependent For example, (1) Chemical properties – reactivity, catalysis (2) Thermal properties – melting temperature (3) Mechanical properties – adhesion, capillary forces (4) Optical properties – absorption and scattering of light (5) Electrical properties – tunneling current (6) Magnetic properties – superparamagnetic effect New properties enable new applications !!!!!!
Scale Changes Everything Four important ways in which nanoscale materials may differ from macroscale materials – Gravitational forces become negligible and electromagnetic forces dominate – Quantum mechanics is the model used to describe motion and energy instead of the classical mechanics model – Greater surface area to volume ratios – Random molecular motion becomes more important
Dominance of Electromagnetic Forces Because the mass of nanoscale objects is so small, gravity becomes negligible – Gravitational force is a function of mass and distance and is weak between (lowmass) nanosized particles – Electromagnetic force is a function of charge and distance is not affected by mass, so it can be very strong even when we have nanosized particles The electromagnetic force between two protons is 1036 times stronger than the gravitational force!
Quantum Effects Classical mechanical models that we use to understand matter at the macroscale break down for… –The very small (nanoscale) –The very fast (near the speed of light) Quantum mechanics better describes phenomena that classical physics cannot, like… –The colors of nanogold –The probability (instead of certainty) of where an electron will be found
Surface Area to Volume Ratio Increases As surface area to volume ratio increases – A greater amount of a substance comes in contact with surrounding material – This results in better catalysts, since a greater proportion of the material is exposed for potential reaction
Random Molecular Motion is Significant • Tiny particles (like dust) move about randomly – At the macroscale, we barely see movement, or why it moves – At the nanoscale, the particle is moving wildly, batted about by smaller particles • Analogy – Imagine a huge (10 meter) balloon being batted about by the crowd in a stadium. From an airplane, you barely see movement or people hitting it; close up you see the balloon moving wildly
What Does This All Mean? The following factors are key for understanding nanoscale-related properties – Dominance of electromagnetic forces – Importance of quantum mechanical models – Higher surface area to volume ratio – Random (Brownian) motion It is important to understand these four factors when researching new materials and properties
- Slides: 29