To reduce to provide an incentive

1. Discuss with the partner:

1) What is nano?

2) Why are people interested in nanotechnologies nowadays?

3) How does nanoscience affect the environment?

2. Read the text and do the tasks below:

What is nano?

The material is taken from [e-mail]

A nanowire wraps a beam of light around a strand of human hair. A nanometer is 80, 000 times smaller than the width of a human hair.

A nanometre (nm) is extremely small – one billionth of a metre to be precise, i.e. 0.000000001m. This is 80,000 times smaller than the width of a human hair. Properties of materials can be very different at this level; for instance they can be more chemically reactive, have greater strength or conduct electricity more effectively. Take the differences between graphite, which is used in the lead of pencils, and diamond – although both are made up of the same element (carbon), the way in which the atoms are arranged in each is slightly different, giving the dramatic differences between the two. While in the case of graphite and diamond this happens naturally, nanotechnology offers the opportunity for us to make such differences by design.

Why do materials behave differently at the nanoscale?

Materials behave differently at this scale for two reasons:

Firstly, very small particles have a larger surface area compared to the same amount of material in a larger lump (for example, grains of sand would cover a bigger surface than the same amount of sand compressed into a stone). As the surface of the particle is involved in chemical reactions, the larger surface area can make materials more reactive – grains of salt dissolve in water example. In fact, some materials that are generally inactive in their larger form can be more reactive in nanoscale.

Secondly, when we look at materials on a nanoscale level, the relative importance of the different laws of physics shift and effects that we normally do not notice (such as quantum effects) become more significant, especially for sizes less than 20nm.

Why is it in interest now?

Nanoparticles have existed naturally for thousands of years – they are produced by volcanoes, algae and in processes such as burning and cooking for instance. We have also been able to use chemistry and molecular biology to help us to build synthetic materials out of molecules for decades (polythene is made out of nano-scale sub-units for example). Recent advances in technology allow us to study and manipulate atoms much more precisely and easily, leading to an expansion of the potential uses of and interest in this science.

In June 2003 the UK Government commissioned the Royal Society and the Royal Academy of Engineering to carry out an independent review into current and future developments in, and the impacts of, nanoscience and nanotechnology. This report was published in July 2004, raising the profile of nanotechnology and highlighting the need for more research and discussion into the potential benefits and risks involved. The Government has recently published its response to the report.

Following the recent debates surrounding other new technologies, some scientists are also keen to develop any future technologies in partnership with the public – discussing the risks and opportunities of nanotechnologies in advance of the products being available and appreciating the diverse range of views. As a consequence, there is more and more discussion of nanotechnology in public.

How is nanoscience being used?

Most current applications of nanotechnology simply use materials that happen to have features at the nanoscale (materials that exist in very fine powder form for instance), rather than exploiting any of the additional properties that particles might have at the nanoscale.

Commercial examples of nanotechnology that exploit these additional properties are currently very limited however – they are not exploited in any food or pesticide products at the moment for example.

Current uses of nanotechnolog y include:

– Sunscreens based around microfine particles are already in use in Europe, including the UK. Microfine and nanoparticles of zinc oxide absorb UV light while allowing visible light to pass through. These sunscreens appear translucent, but act as effective absorbers of UV light.

– Nanomaterials are currently used for very thin coatings – for example, self cleaning windows. The film made out of titanium dioxide nanoparticles speeds up the breakdown of dirt and bacteria in the presence of water and sunlight which is then washed off the glass more easily.

– Nanocomposites are used to make car bumpers that are claimed to be 60% lighter and twice as resistant to scratches and bumps than usual.

How will nanoscience affect the environment?

So far there has been very little research into the effects that nanoparticles could have on the environment. However, assessments have been made based on research into other small their ability to accumulate in the food chains. For instance, nanoparticles could be taken up by soil and water organisms and then interfere with their biological processes; if these animals are then eaten by other larger particles such as airborne pollutants. These predictions raise concerns about how nanoparticles might behave in the air, water or soil, their effect on animals and plants and organisms the nanoparticles could build up in the food chain. It will therefore be important for us to learn more about the effects of nanoparticles on organisms and whether or not they may build up in the environment.

Can nanoscience help the environment?

If we can address these concerns sufficiently, in the future nanoscience could be used to develop new solutions to environmental problems:

– There is considerable interest in using nanoparticles to convert pollutants to less harmful chemicals in the environment. This technology is based on the large surface area compared to volume of nanosize materials that makes them reactive and therefore useful in speeding up chemical reactions. For example, in the USA, the use of nanoparticles of iron to remove organic pollutants from soil and groundwater has been studied.

– Nano-engineered membranes could enable more energy-efficient water purification. A new technique called ‘electrospinning’ uses electrical rather than mechanical forces to ‘spin’ cellulose into ultra-thin fibres that are less than 100 nanometers in diameter, potentially creating a molecular ‘sieve’. These nanofibres could have a wide variety of applications in addition to water purification – for example, biodegradable electrospun cellulose mats could be used to absorb fertilizers and pesticides allowing a more targeted approach and use of chemicals. Cellulose is also a significant waste product in the industrial manufacture of clothes. Creating a new use for it might encourage more efficient manufacturing and provide an incentive to recycle the material and remove it from the waste stream.

– Nano-sensors could be used to detect chemicals in the environment, and monitor the state of mechanical stresses within buildings.

– ‘Quantum dots’, nanoparticles of semiconductors, could make more efficient solar cells. By exploiting the quantum effects that become important at such a small scale, the particles can be ‘fine tuned’ to absorb the particular colours of light in sunlight. They also might be used to ‘concentrate’ sunlight, avoiding the need for expensive sun tracking mechanisms.

– Nanoparticles in paint technology offer the possibility of thinner, and therefore lighter, coatings, which could reduce, for example, the weight of aircrafts and so cut greenhouse gas emissions.

Дата добавления: 2015-11-16