Extreme Physics -Nanoparticles Done by: Foo Kai Siang: 3A311

Introduction-What are nanoparticles? There is no accepted international definition of a nanoparticle However, one given in the UK is: "A particle having one or more dimensions of the order of 100nm or less". There is a note associated with this definition: "Novel properties that differentiate nanoparticles from the bulk material typically develop at a critical length scale of under 100nm".

Why are they different The "novel properties" mentioned are entirely dependent on the fact that at the nano-scale. The physics of nanoparticles mean that their properties are different from the properties of the bulk material. This makes the size of particles or the scale of its features the most important attribute of nanoparticles. Thus, it can be said that nanoparticles are different because they are ‘small’

Why are they different There is no strict dividing line between nanoparticles and non-nanoparticles. The properties of many conventional materials change when formed from nanoparticles. This is typically because nanoparticles have a greater surface area per weight than larger particles; this causes them to be more reactive to certain other molecules.

Case Study: Gold Nanoparticles We all know that Gold is very shiny when in its natural state. However, the formation of gold nanoparticles can be observed by a change in colour since small nanoparticles of gold are red.

Case Study: Gold Nanoparticles A layer of absorbed citrate anions on the surface of the nanoparticles keep the nanoparticles separated. The presence of this colloidal suspension can be detected by the reflection of a laser beam from the particles Switching to a smaller anion allows the particles to approach more closely and another color change is observed. Thus, gold nanoparticles can be many different colours, red, blue, yellow, depending on its size.

Case Study: Gold Nanoparticles As mentioned previously, nanoparticles are more reactive to certain other molecules than bulk particles Applying this theory in the case of Gold nanoparticles, the bulk particles of gold that we see today are not reactive to the citrate anions as they do not have such a large surface area per weight ratio. Thus, without the citrate anions giving off the red colour under the microscope, bulk gold particles that we know today are shiny and glittery

Technological Applications Manufacture of stain-resistant fabrics Solar panels Lightweight bulletproof military vest Therapy against Heart Disease Imaging agents

Stain-Resistant Fabric Making composite fabric with nano-sized particles or fibers allows improvement of fabric properties without a significant increase in weight, thickness, or stiffness as might have been the case with previously-used  techniques. For example incorporating nano-whiskers into fabric used to make pants produces a lightweight water and stain repellent material. Nanoparticles can cause water to bead up, making the fabric water and stain resistant

Stain Resistant Fabric More examples are: Silver nanoparticles in fabric that kills bacteria making clothing odor- resistant. Nanopores providing superior insulation for shoe inserts in cold weather.  Nanoparticles that provide a "lotus plant" effect for fabric used awnings and other material left out in the weather, causing dirt to rinse off in the rain.

Solar Panels Scientists are developing a relatively new approach to solar cells: lacing them with nanoscopic metal particles. As the authors describe in a new article, this approach has the potential to greatly improve the ability of solar cells to harvest light efficiently.

Solar Panels Current solar cells cannot convert all the incoming light into usable energy because some of the light can escape back out of the cell into the air. Additionally, sunlight comes in a variety of colours and the cell might not be efficient in converting all light forms

Solar Panels The nanoparticle approach seeks to remedy these problems. The key to this new research is the creation of a tiny electrical disturbance called a "surface plasmon." First of all, the use of nanoparticles causes the incoming sunlight to scatter more fully, keeping more of the light inside the solar cell. Second, varying the size and material of the particles allows researchers to improve light capture at otherwise poorly-performing colors.

Light, Bulletproof Military Vest Liquid armor has been shown to stop bullets more effectively than plain Kevlar, according to British firm BAE Systems. The material could be used to make thinner, lighter armor for military personnel and police officers,  Materials scientists combined a shear-thickening liquid with traditional Kevlar to make a bulletproof material that absorbs the force of a bullet strike by becoming thicker and stickier.

Light, Bulletproof Military Vest Its molecules lock together more tightly when it is struck, the scientists explained -- they described it as "bulletproof custard," Shear-thickening liquids are composed of hard nanoparticles suspended in a liquid, which turns rigid after being struck with a bullet or shrapnel. BAE says their tests provide the first clear evidence that it can actually protect people.

Light, Bulletproof Military Vest In some tests, BAE scientists used a gas gun to fire ball-bearing bullets at nearly 1,000 feet per second at two test materials -- 31 layers of regular Kevlar and 10 layers of Kevlar combined with the shear- thickening liquid. The shear-thickening liquid stopped the bullets more quickly and prevented them from penetrating as deeply, showing that the nanoparticles in the ‘liquid armour’ is indeed effective.

Therapy Against Heart Disease Researchers at MIT and Harvard Medical School have built targeted nanoparticles that can cling to artery walls and slowly release medicine. It is an advance that potentially provides an alternative to drug-releasing stents in some patients with cardiovascular disease. The particles, dubbed “nanoburrs” because they are coated with tiny protein fragments that allow them to stick to target proteins, can be designed to release their drug payload over several days.

Therapy Against Heart Disease They are one of the first such targeted particles that can precisely home in on damaged vascular tissue The nanoburrs are targeted to a specific structure, known as the basement membrane, which lines the arterial walls and is only exposed when those walls are damaged. Therefore, the nanoburrs could be used to deliver drugs to treat atherosclerosis and other inflammatory cardiovascular diseases.

Imaging Agents Hybrid nanoparticles which incorporate multiple functionalities, such as fluorescence and magnetism, can exhibit enhanced efficiency and versatility by performing several tasks in parallel. In this study, magnetic-fluorescent semiconductor polymer nanospheres (MF- SPNs) have been synthesized by encapsulation of hydrophobic conjugated polymers and iron oxide nanoparticles in phospholipid micelles.

Imaging Agents Four fluorescent conjugated polymers were used, yielding aqueous dispersions of nanoparticles which emit across the visible spectrum. In MRI studies, they were seen to have a shortening effect on the transverse relaxation time, which demonstrates their potential as an MR contrast agent.

Imaging Agents Finally, successful uptake of the MF-SPNs by SH-SY5Y neuroblastoma cells was demonstrated, and they were seen to behave as bright and stable fluorescent markers. There was no evidence of toxicity or adverse affect on cell growth.

Some Video links http://www.youtube.com/watch?v=jUh1g HG2jns http://www.youtube.com/watch?v=uyhxRI vw_cY

Conclusion Nanoparticles are small substances which are different than its bigger form. Nanoparticles are really useful in the advancement of modern technology and are really important to mankind They could be our basis for the next big human technology breakthrough and it will be important for us to do more research on it as can be seen from the examples above, we are not really quite done with Nanoparticles just yet.

Reflection I feel that it is really a great and enriching experience learning about such a fascinating topic. I started doing this topic as an ACE assignment but felt a little sad when I actually finished it in the end. This is really a field of technology in which people and scientists can focus on in the future to create better and more efficient technology to enhance and improve the lives of the people of the world. I have also gained much more insight on this topic.

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