Metal Nanoparticles


In recent years, researchers in the field of nanotechnology are finding that metal nanoparticles have all kinds of previously-unexpected benefits in both the conventional technology and experimental medical industries.

These nanostructured metal powders (in some cases they may even be alloys) are typically reduced to their particle size using metal salts or some type of corrosive alcohol.

Copper nanoparticles constitute some of the most versatile and useful metal nanoparticles currently in production.

In electronics manufacturing it has been found that thin films of extra-small copper particles exhibit a peculiarly strong electrocatalytic behavior, making them prime candidates for many types of electric processes.

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Researchers at Yangzhou University in China conducted a series of experiments involving copper nanoparticles which they stabilized with cysteine and used the resulting mixture to coat individual electrodes of indium tin oxide.

Once the electrodes have been altered in this way, they are more capable of transferring electrons back and forth to establish an electrical current. They also respond efficiently to the effects of nitric oxide and other nitrate derivatives, which makes them useful electrochemical sensors.

What does all of this mean? In March of 2009 the University of Helsinki decided to find out what could be achieved by utilizing the conductive properties of copper particles. The University’s Polymer Chemistry Research Group found that the fundamental properties of the copper changed dramatically when they were reduced to a billionth of their original size.

The tiny copper nanoparticles have more atoms on their surface than on the inside, which causes a variety of characteristics but most importantly makes their melting temperature very low. Researchers then applied a heat treatment known as “sintering” and found that afterwards, the copper particles could be used to create patterns and layers of an electricity-conducting nature. They decided to apply these interesting designs to paper.

It seems that many types of metal particles can achieve these results when coated with a polymer layer, turning them into excellent electrical conductors. Scientists can design intelligent formations and print them onto the paper in such a way that they anticipate using paper instead of expensive silicon boards and chips in the not-too-distant future.

The Polymer Chemistry Research Group didn’t necessarily intend to make such a discovery in their work with copper nanoparticles. They were actually conducting a routine test of various compounds that could protect copper nanoparticles during the manufacturing process and had decided to try out polymers and compounds made of smaller molecules.

They rotated through several combinations before settling on polyethylene imine and tetraethylenepentamine as good candidates. Sure enough, these polymer layers contained the right level of oxidization to be effectively sintered to the surface of the paper.

Researchers then measured the electrical conductivity of the recently-applied particle layer and were both pleased and surprised to find that at a certain temperature they could cause rapid re-growth of the particles.

These properties turned the nanoparticles into ideal conductors of electricity and gave researchers a brilliant idea. Their findings may have revolutionized the world of electronics by providing paper as a cheaper, more malleable substance on which to imprint electronic code. Soon, microchips will be flexible and inexpensive, as will motherboards.

Metal nanoparticles have served a variety of functions over time, but gold nanoparticles are some of the most popular. They are non-toxic and appear to have endless medical applications; it has also been found that ingesting liquid gold nanoparticles has extremely beneficial effects on human health.

But gold nanoparticles can be costly, and scientists are looking for ways to replace these expensive nanoparticles with others that behave just as well. Copper nanoparticles are now thought to be the best substitute for the process that allows fuel cells to last longer and perform better.

The U.S. Department of Energy sponsors an institute known as the Brookhaven National Laboratory, which has been conducting a series of x-ray experiments using copper nanoparticles as a replacement catalyst for gold nanoparticles in a fuel cell reaction sequence.

Traditionally the problem posed by fuel cells has been their harmful byproducts, since the main source of energy for these cells is hydrogen. Hydrogen makes a wonderful “food” for the fuel cell but its byproduct often contains large amounts of poisonous carbon monoxide.

Not only is this dangerous to humans and their environment, it’s also bad for the fuel cell mechanisms themselves. The carbon monoxide circulates within the fuel cell until, over time, it has corroded and destroyed the costly platinum catalysts inside the fuel cell that allow it to convert hydrogen into a usable form of electricity.

Scientists anticipate that by mixing the carbon monoxide byproduct with water, they can effect a chemical transformation that will produce relatively harmless amounts of hydrogen gas as well as carbon dioxide, this reaction is known as a “water-gas shift.” It does an extremely effective job of turning almost all the deadly CO into carbon dioxide and hydrogen.

What the Brookhaven Laboratory researchers wanted to do was to find a different way to create and sustain this process within the fuel cell. They found that by using a metal support coated with either gold or copper nanoparticles, they could achieve transformation without the cumbersome and difficult task of directly applying water to the cell while it functioned.

They were even able to maximize catalytic efficiency further by using tiny nanoparticles less than 4 nanometers wide and applying them to a support base made of a metal called cerium oxide, otherwise known as ceria.

As it turns out, copper nanoparticles react wonderfully with ceria and can achieve even higher levels of catalytic activity in this process. Gold was traditionally used because its reliable tendency for reactivity made it a solid choice, but despite the well-documented effects of gold nanoparticles, researchers were put off by its large price tag.

It took quite a bit of experimentation and the Brookhaven Laboratory scientists ran through a number of methods (spectroscopy, x-ray diffraction, absorption) before finally hitting on the thing that worked: nanotechnology. Copper performs at nearly the same level as gold and is much more cost-effective.

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