Nanoparticles and their Applications

Nanoparticles are incredibly small, being 100 nanometers or less in their largest dimension. To produce nanoparticles you break down a bulk material into atoms or ions. You then allow those atoms or ions to condense to form nanoparticles. (You can read about this process in our Nanoparticle Synthesis webpage).

The properties of many conventional materials change when formed as nanoparticles. This is typically because nanoparticles have a greater surface area per weight than larger particles, which causes them to be more reactive to some other molecules.

The materials listed here can be used to form nanoparticles.

Iron Nanoparticles

Every iron atom has four unpaired electrons around each atom. When unpaired electrons align in a certain way, a magnetic field is formed.

Iron nanoparticles retain the magnetic properties of iron and also have a larger surface area. Nanoparticles formed from iron can have several uses. For example, you can use iron nanoparticles in settings such as medical imaging and the clean up of groundwater.

For more information see the Iron webpage

Iron Oxide Nanoparticles

When iron rusts, it forms iron oxide (a combination of iron and oxygen). Iron oxide has magnetic properties, just like iron, however iron oxide has just two unpaired electrons so it is less magnetic. This is called paramagnetic. When iron oxide forms into nanoparticles, they retain their paramagnetic properties, but they can be useable in settings where larger particles aren’t.

Magnetic resonance imaging or MI produces an improved image using paramagnetic nanoparticles. These particles attach to any object that you want to take an image of. For example, to functionalize iron oxide nanoparticles, researchers have coated them with molecules that are drawn towards objects such as cancer tumors.

If you make nanoparticles with a core of iron oxide nanocrystals and they are surrounded by nanoporous silica, you can even better images of tumors. This method could also provide a way to control the release of therapeutic drugs.

For more information see the Iron Oxide webpage

Gold Nanoparticles

The world of medical treatments has looked to various materials throughout the decades to provide treatments, but some materials, such as platinum, can be toxic. Gold has proven useful in the past, and when researchers were able to create gold nanoparticles, they discovered that they could be used in applications where their size could provide new capabilities. Molecules can attach to gold nanoparticles that in turn are attracted to diseased parts of the body. This includes cancer tumors and drug modules, enabling more targeted drug delivery.

Gold nanoparticles that get really tiny (with a diameter of 5 nm or less), also offer an opportunity for change. Bulk gold is an inert material, meaning that it doesn’t corrode or tarnish. That characteristic means gold isn’t useful for chemical reactions. But gold nanoparticles are different. Because of their small size, these particles can be used as catalysts to enable reactions, such as the changing of air pollution into molecules that are harmless or oxidizing carbon monoxide.

Gold nanoparticles can also be used to convert some wavelengths of light into heat. All metals, including gold, have electrons that roam freely; that is, they aren’t attached to any one atom in the metal. These free roaming electrons assist in conducting a current when voltage is applied across a conductor. The free electrons can then convert light into heat by absorbing energy from the light, and producing a cloud of free electrons that resonate on the surface of gold nanoparticles.

For more information see the Gold webpage

Platinum Nanoparticles

Platinum is a remarkably efficient catalyst, though costly. Catalytic converters in cars, for example, use platinum as a catalyst that converts molecules in pollution to partially purify them.  

Atoms in molecules can bond with platinum atoms. The resulting atoms can, in some cases, react with other molecules. When molecules break up into atoms, platinum can act as a catalyst for chemical reactions that happen at lower temperatures. Platinum nanoparticles can be used to increase surface area available for a reaction. This larger surface area ups the percentage of platinum atoms that are available to contact other molecules in the reaction. That means you can use a smaller amount of platinum to create a reaction that can break down pollutants, which is good news considering the material’s cost!  

For more information see our Platinum webpage

Silica Nanoparticles

Silica, while a weak conductor of heat and electrons, tells a different story when in the form of silica nanoparticles. These nanoparticles are the basis of silica aerogels, which are made up of silica nanoparticles and nanopores. Nanopores are filled with air, so silica aerogels are primarily made of air. It turns out that both silica and air have extremely low thermal conductivity, so nano aerogels are some of the best thermal insulators around.  

Functionalizing silica nanoparticles can be done by bonding molecules to a nanoparticle that is capable of bonding to yet another surface. For example, when silica nanoparticles that have been functionalized attach to cotton fiber, you get a water repellent fabric. This repellent nature is caused by the rough surface that results from the attachment.

One kind of silica nanoparticle contains nanoscale pores, which forms the basis of a new method of drug delivery. Molecules of drugs are stored in the pores. The drugs can thereby be released slowed into the area of the body that is diseased, such as a tumor.

For more information see our Silica webpage

Silver Nanoparticles

Silver may be lovely in jewelry and other ornamental objects, but you may not know that it’s also used to kill off bacteria. Silver can help to inhibit infections in wounds, a method that was used before the development of antibiotics. That’s because silver offers good thermal and electrical conductivity.  

• Silver nanoparticles, because of the large number of atoms on their surface, kill bacteria in a few ways, such as:
• For the treatment of wounds
• In plastic food storage bins to help kill bacteria from foods that have been previously stored in the containers
• In getting rid of odors; this possible because microorganisms in the form of microbes simply can’t live near silver ions
• Making low-cost filters. When created with carbon nanotubes and silver nanowires these filters can kill bacteria in drinking water  

For more information see our Silver webpage    

Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles have more surface area so they can react more efficiently with other molecules. Titanium dioxide also absorbs ultraviolet light, which makes it a key ingredient in many sunscreen products. That happens because titaniu  m dioxide nanoparticles act as photocatalysts. Photocatalysts can take the energy contained in light and catalyze reactions with molecules in lower temperatures, and is especially effective in sunlight.  

Titanium dioxide also reflects colors in the visible light spectrum as white light. Why is this useful? This ability makes the material useful in providing a white pigment in paints. It’s also what produces some white residue on your skin when you use sunscreen. Titanium dioxide is also used in creams and coatings that don’t leave a white residue as they absorb UV.    

For more information see our Titanium Dioxide webpage