In this wonderful world we see different things of different sizes and colors. Our vision is limited to a particular range of size, and we differentiate colors because of light matter interaction, which is due to the surface property of a material.
We all know about gold; a layman can recognize it because of its color. But gold particles at nanoscale are red. Means the property changes with size, and this amazing phenomenon dragged the attention of different scientists towards a technology, called the Nanotechnology. This technology is the synthesis, processing, manipulating of materials at nanoscale which is the scale from 1 to 100 nanometers, and nanometer is the billionth of a meter, means quite small.
A material is characterized by its physical and chemical properties, but the physical properties (mechanical, thermal, optical, electronic, and electrical) changes by reducing the size.
1. Some Facts about Nanomaterials: Carbon is considered to be the future of world as its allotropes at nanoscale (Graphene, Nano Diamond, Carbon Nanotube (CNT), and Fullerene), show versatile properties. Taking the example of Carbon Nanotube (it’s of three types Single Walled CNT, Double Walled CNT, and Multi Walled CNT), some interesting properties/facts are:
Mechanical Properties: In 2000, a multiwalled carbon nanotube (CNT) was tested and the tensile strength was calculated as 63 giga Pascals, which in weight equivalence can bear 6422 Kg force of cross-section of 1 square millimeter, and research is still going on and this property gets increased.
Electrical Properties: We normally consider gold, silver as good conductors of electricity, but because of their high price these are not used commercially and the commercial conducting considered as best is copper and aluminum and are widely used. The copper and aluminum may get replaced by CNT as it shows versatile electric properties, with current density of 4×109 Ampere/cm2, which is thousand times that of copper.
Thermal properties: All CNT’s have very good thermal conducting property along the tube. The single walled nanotube has the thermal conductivity of 3500 W.m-1.k-1, compare to copper (which is today’s best thermal conducting material) transmits only at 385 W/m/k.
2. Applications of Nanotechnology:
Energy Application: Nanotechnology finds its application in Solar Photovoltaic, Light Emitting Diodes, Hydrogen Storage, Fuel Cells, Super Capacitors, Batteries, Geothermal energy harvesting, flywheels etc. The efficiency of a solar cell is a function of its band gap and this band gap is size dependent. We normally use silicon as a semiconducting material, but with the help of nanotechnology we can use insulators to conduct electricity, as the conduction is the function of band gap and it can be tailored to any value by nanotechnology.
Another approach of nanotechnology in energy is Nanogenerator , which can harvest energy from day to day activities( like body motion, body heat and so on). Nano generator converts mechanical/thermal energy produced by small –scale physical change into electricity. These approaches are Piezo electricity, Tribo electricity, Pyro electricity. These approaches can harvest energy and finds its application as:
• Self-Powered Nano/Micro Devices: We install sensor at different places for different applications and these sensors are excited externally. Now sensors can self excited by harvesting energy by using different kind of nanomaterials.
• Smart Wearable Systems.
• Harvesting energy from human body motion.
Medical Applications: Medical applications of nanotechnology are called nanomedicine. Current problem for nanomedicine involve understanding the issues related to toxicity and environmental impact of nanomaterials. This problem gets almost terminated by a different approach called the Green Nanotechnology. The medical applications of nanotechnology are:
• Targeted Drug Delivery: When we take a medicine, its effect not only goes to the effective area but also at all parts of body, which could damage the normal cells. So target drug delivery is a good approach in which the medicine would address only the required area.
• Cancer Treatment: Cancer can treat by using the nanomaterials, as their size is less than the cancer cells. These nanomaterials get absorbed by the cancer cells and are heated outside by RF, which can burn the cancer cells. Other approaches to treat cancer are:
• Abraxane, approved by U.S Food and Drug Administration to treat Breast cancer, pancreatic cancer, and non-small-cell lung cancer is a nanoparticle of albumin bound paclitaxel. Other drugs are Doxil, Rapamune.
• Sensing and Imaging: The small size of nanoparticles can be useful in oncology, in imaging. Quantum Dots (QD) when used in conjunction with MRI can produce images of tumor sites. Nanoparticles of Cadmium Selenide Quantum Dot glow when exposed to UV light. When it is injected they seep into cancer cells. The surgeon can see the glowing tumor and use it as a guide for more accurate tumor removal.
• Blood Purification: Magnetic nanoparticles are proven research instruments for the separation of cells and proteins from complex media. The technology is available under the name Magnetic- activated cell sorting or Dynabeads. Magnetic nanoparticles can be used for the removal of various noxious compounds including toxins, pathogens and proteins from whole blood in an extracorporeal circuit similar to dialysis.
In contrast to dialysis, which works on the principle of the size related to diffusion of solutes and ultra filtration of fluid across a semi-permeable membrane, the purification with nanoparticles allows specific targeting of substances.
• Tissue Engineering: Nanotechnology may be used as a part of tissue engineering to help reproduce or repair or reshape damaged tissue.
3. How nanomaterials are fabricated: There are different techniques to fabricate nanomaterials and are classified by two approaches Top Down and Bottom Up ones, and are further classified by physical and chemical methods.
Top Down approach means slicing or successive cutting of bulk material to get nanomaterial.
Bottom Up approach is piecing together of small particles to form nanomaterials of particular size range.
—The author has sourced information from the Wikipedia
The author, a student at Jamia Millia Islamia, New Delhi, can be reached at: email@example.com