Lesson Explainer: Nanoparticles Chemistry

In this explainer, we will learn how to identify nanoparticles, describing their properties and uses.

Nanoparticles are incredibly small objects that have the potential to completely change our lives. Lots of scientists have studied the properties of nanoparticles and many of them state that nanoparticles will be used to make us healthier and to make our lives much easier. It is expected that nanoparticles will fundamentally change the way we live our lives in the future. This is an excellent reason to learn about them here in this explainer.

Nanoparticles are small structures that are between 1 and 100 nanometres (nm). Some nanoparticles have relatively simple shapes, and others have very unusual and complex shapes. Nanoparticles can contain just one type of element or atom. They can also be made up of lots of different types of elements, and they can even contain lots of different types of molecules.

Nanoparticles usually contain a few hundred atoms, and they always have a very high surface-area-to-volume ratio. They almost always have unusual physical and chemical properties because they are so incredibly tiny, and they have such incredibly high surface-area-to-volume ratios.

Definition: Nanoparticle

Nanoparticles are particles of matter that are between 1 and 100 nanometres (nm) in diameter.

Example 1: Identifying What Is and What Is Not a Fact About Nanoparticles

Which of the following statements could not be used to describe nanoparticles?

  1. Particles with a high surface-area-to-volume ratio
  2. Particles 1–100 nm in size
  3. Particles that are smaller than most atoms
  4. Particles with different properties than those of the same material in bulk
  5. Particles containing a few hundred atoms or ions

Answer

Nanoparticles are incredibly small objects that have a diameter between 1 and 100 nanometres (nm). Nanoparticles are smaller than almost all single-celled organisms and viruses. Each nanoparticle ordinarily only contains a few hundred atoms. We can use these statements to determine that options B and E can be used to describe nanoparticles.

Nanoparticles tend to have very high surface-area-to-volume ratios, and this helps us to understand why their physical properties are vastly different from those of the same material in bulk. We can use this sentence to determine that options A and D can be used to describe nanoparticles.

We have deduced through the process of elimination that option C cannot be used to describe nanoparticles, but we could also validate that C is the correct answer with some logical reasoning. Nanoparticles have a diameter between 1 and 100 nanometres, whereas atoms have diameter values of about 0.1 nanometres. This statement can be used to determine that option C is factually incorrect and that it must be the correct answer for this question.

We can compare nanoparticles with more familiar everyday objects to understand their almost unfathomably small size. Human hair is one of the thinnest materials that people see a lot of the time or even every day of their lives. The average strand of human hair has a diameter of approximately 80‎ ‎000100‎ ‎000 nm. Nanoparticles are defined as being 1–100 nm. We can use both of these statements to determine that the smallest nanoparticles are tens of thousands of times smaller than a single strand of human hair.

We can also compare nanoparticles with single water molecules. This comparison can be used to show that some nanoparticles are not that much bigger than a single triatomic compound. Water molecules are about 0.27 nm wide, and the smallest nanoparticles can be no more than 1 nm. This means that some nanoparticles can be just a few times bigger than a single water molecule.

Example 2: Comparing Medium-Sized Nanoparticles with a Single Strand of Human Hair

A human hair has a diameter of 80‎ ‎000 nm. How many nanoparticles with a diameter of 50 nm would fit across the human hair? Give your answer to the nearest whole number.

Answer

The question asks us to consider how many nanoparticles would fit across human hair and not around its perimeter. This means we need to consider how many 50 nm particles can fit end-to-end along an imaginary line that is 80‎ ‎000 nm long. This value can be determined if we divide the value of 80‎ ‎000 nm by the value of 50 nm. The division is performed on the following line 8000050=1600.nmnm The calculation can be used to determine that 1‎ ‎600 medium-sized (50 nm) nanoparticles can fit across a single strand of human hair.

The following image compares the size of most ordinary atoms and molecules with the sizes of nanoparticles. The image shows that some polyatomic molecules are the same size or even bigger than certain nanoparticles. There are lots of biological macromolecules in our bodies that are much larger than some carbon-based and metallic-based nanoparticles.

The image also shows that some nanoparticles are hundreds of times smaller than fine particles and thousands of times smaller than coarse particles. Fine and coarse particles are microscopic particles that are suspended in the air. Fine particles include substances like smog and soot. Coarse particles include substances like cement dust and mold spores.

Definition: Fine particle (PM2.5)

Fine particles are particles of matter that are between 100 and 2‎ ‎500 nanometres (nm) in diameter.

Definition: Coarse particle (PM10-2.5)

Coarse particles are particles of matter that are between 2‎ ‎500 and 10‎ ‎000 nanometres (nm) in diameter.

Nanoparticles are almost very reactive materials. Their high reaction rates can be understood if we consider how surface-area-to-volume ratios depend on the size of a three-dimensional object. Objects have low surface-area-to-volume ratios when they are large. Objects have much higher surface-area-to-volume ratios when they are small. Nanoparticles must therefore have very high surface-area-to-volume ratios because they are incredibly small objects. Nanoparticles must also be incredibly reactive because a lot of the nanoparticle surface will always be exposed to other reactant particles.

Many metallic nanoparticles are effective catalysts because they have such high surface-area-to-volume ratios and a lot of the catalyst is exposed to other reactant particles. The reactant particles come into contact with the catalyst surface at a fast rate, and chemical reactions happen very quickly.

Example 3: Understanding Why Metal Nanoparticles Can Be Incredibly Reactive Materials

Which of the following reasons could explain why 1 g of gold nanoparticles is a better catalyst than 1 g of solid gold metal?

  1. The nanoparticles have a smaller mass.
  2. The nanoparticles have a larger surface area.
  3. The nanoparticles have a smaller surface area.
  4. The nanoparticles have a greater mass.
  5. The nanoparticles have a larger volume.

Answer

Nanoparticles almost always have incredibly high surface-area-to-volume ratios because the surface-area-to-volume ratio tends to increase as shapes get smaller. Nanoparticles will almost always be able to react more rapidly than bulk materials because nanoparticles have higher surface-area-to-volume ratios. More of the reactive atom surfaces are exposed to other reactant particles and this means there can be more chemical reactions each second. We can use this line of reasoning to determine that option B is the correct answer for this question.

The following figure shows how three-dimensional objects have a high surface-area-to-volume ratio when they are small. The figure compares three cubes that have different length (𝐿) values. The smallest cube is 1 cm long and the other two cubes are 10 cm and 100 cm long. The figure shows the surface areas, volumes, and surface-area-to-volume ratios for the three different cubes.

The volume (𝑉) for each cube was calculated with the 𝑉=𝐿 expression, and the surface area values (𝐴) were calculated with the 𝐴=6×𝐿 formula. The surface-area-to-volume ratio was determined by dividing each surface area number by the corresponding volume value. The step-by-step calculations show that surface-area-to-volume ratios are larger for smaller cubes.

Example 4: Calculating the Volume of a Cubic Nanoparticle

A type of nanoparticle known as a nanocube is shown in the diagram. Using the dimensions provided, what is the volume of the nanoparticle?

Answer

The volume of a cube can be determined with the 𝑉=𝐿 mathematical expression that uses the 𝑉 symbol to represent total volume and the 𝐿 symbol to represent length values. The shape is a cube, and all of its sides have a length value (𝐿) of 30 nm. The volume can be calculated as 𝑉=(30)nm or as 𝑉=(30)×(30)×(30)nmnmnm. If we perform this calculation, we get the following result: 𝑉=27000nm. This suggests that the nanoparticle has a volume of 27‎ ‎000 nm3. We will not change this to be in units of nm3 because the question asks us to use the dimensions that are provided in the image.

Titanium dioxide (TiO)2 nanoparticles are increasingly being incorporated into windows to help keep them clean and clear. The titanium dioxide nanoparticles are catalysts that generate electrons when they interact with ultraviolet radiation. The electrons convert water molecules in the air into hydroxyl radicals (OH) and these hydroxyl radicals break down carbon-based grime into smaller pieces of dirt. The broken-down dirt particles can then be washed away by rain droplets. Scientists put a relatively small amount of titanium dioxide nanoparticles into each windowpane because the particles have very high surface-area-to-volume values. The nanoparticles are practically invisible, and they do not affect the transparency of any window.

Nanoparticles have many unusual interactions with the human body. Nanoparticles are so small that they can be carried in the wind and inhaled into our respiratory system when we breathe in and out. The interactions of nanoparticles with the human body are not very well understood, and some scientists are worried that the inhalation of nanoparticles could increase rates of human illness and death. Scientists are also concerned that nanoparticles could negatively affect the environment because we do not know how nanoparticles interact with most forms of living and nonliving matter.

Nanoparticles can be absorbed surprisingly deep into the human skin. There are now many different types of sun creams that are made with zinc oxide (ZnO) and titanium oxide (TiO)2 nanoparticles. Sunscreen lotions tend to give better skin coverage and better protection from UV rays when they contain either zinc oxide or titanium oxide nanoparticles. Sunscreen lotions also tend to be transparent when they contain nanosized metal oxide particles. Scientists are starting to incorporate nanoparticles into other cosmetic products because nanoparticles can be designed to have lots of desirable interactions with human skin.

Example 5: Identifying the Advantages of Adding Nanoparticles to Sun Creams

Nanoparticles are used in sun creams. Which of the following reasons is not an advantage of adding nanoparticles to sun creams?

  1. Nanoparticles in sun creams are absorbed deeper into the skin and provide longer protection.
  2. Nanoparticles in sun creams may be washed away into the environment.
  3. Nanoparticles in sun creams result in a transparent liquid.
  4. Nanoparticles in sun creams give better skin coverage.
  5. Nanoparticles in sun creams provide better protection against UV rays.

Answer

Metal oxide nanoparticles are added to sun creams for a number of different reasons. There is the fact that nanoparticles can provide better protection against ultraviolet (UV) radiation and the fact that nanoparticles can be transparent. There is also the fact that nanoparticles give better skin coverage and the fact that nanoparticles tend to be absorbed deeper into the skin. Some scientists are worried that, with the excessive use of sun creams, metal oxide nanoparticles could end up damaging the environment. We do not currently understand how nanoparticles affect the environment, and it is possible that they could damage the environment when they are washed off people’s skin and deposited on the ground or in bodies of water. We can use these statements to determine that option B is not an advantage of adding nanoparticles to sun creams and that option B is the correct answer for this question.

Scientists have determined that gold and silver nanoparticles have the ability to pass through mammalian and bacterial lipid membranes. Metal nanoparticles are now being studied for a combination of drug-delivery and antibacterial applications. The metal nanoparticles can be optimized for drug-delivery purposes, and they can be optimized to enter into and break down bacterial cells. It is also thought that metal nanoparticles will be used to make microscopic electrical circuits because metal nanoparticles can conduct electricity. It is interesting to note that many metallic nanoparticles also tend to have unusual colors and toughness values. Copper nanoparticles are surprisingly tough, and nanosized gold can have a red, orange, green, or blue color.

Different types of nanoparticles can be used to make films, wires, and fibers. These are examples of one-dimensional nano substances, which are nano substances that have one nano dimension. Thin films are used to protect food and stop it from spoiling. They can also be used to cover surfaces, similarly to paint, to prevent rusting or corrosion. One-dimensional nano wires are used in electronic circuits, and incredibly small nanofibers exist inside our water filters ensuring the water is safe to drink.

Lipid nanoparticles are also being modified for drug-delivery purposes. Liposomes are small nanoparticles that are made up of lipid molecules. The properties of liposomes are being changed to make them stronger and to make them more effective at entering into target cells throughout the human body.

Phospholipid bilayer

Graphene, buckminsterfullerene, and carbon nanotubes are some of the most unusual nanoscopic materials because they consist entirely of carbon atoms. Lots of scientists are currently studying these carbon-based nanomaterials, and we are learning more and more about them every day.

Graphene consists of a single layer of covalently bonded carbon atoms. The carbon atoms form an incredibly thin honeycomb structure. Graphene is one of the thinnest materials that have ever been discovered, and it has exceptionally high tensile strength. It is harder than diamonds and yet more elastic than rubber. It also happens to be an effective conductor of electricity, and it conducts heat better than almost every other substance on earth. It is thought that graphene can be used to make advanced electronic equipment and new types of sensors and biodevices.

Crystal lattice model of a crystal lattice

Three-dimensional nano substances are nano substances that have three nano dimensions, and a common example is buckminsterfullerene. Buckminsterfullerene (buckyballs) consists of single three-dimensional nanoparticles that contain sixty covalently bonded carbon atoms. The carbon atoms form small cage-like particles. Some scientists have shown that buckyballs (C)60 can be used to deliver small compounds to target cells inside the human body. Small pharmaceutical molecules can be trapped inside buckyballs, and these buckyballs can be steered or directed toward target cells in cancerous or infected human organs. The pharmaceutical compounds should arrive at the target cells relatively unaltered because the buckyballs will stop them from interacting with other molecules.

Carbon nanotubes are hollow two-dimensional tubes that are made up of covalently bonded carbon atoms. They are examples of two-dimensional nano substances that have two nano dimensions. The tubes usually have diameters that are between 0.4 nm and 40 nm. The nanotubes usually have length values that are hundreds or thousands of times longer. Carbon nanotubes generally have high electrical conductivity values, and they also tend to conduct heat more effectively than diamonds. Carbon nanotubes have extraordinarily high tensile-strength values, and most nanotubes are hundreds of times stronger than sturdy metals like steel and iron. Many scientists state that carbon nanotubes will be used to make effective biological sensor devices, and other scientists propose that carbon nanotubes will be used to make advanced electronic devices.

Buckminsterfullerene (buckyball, C60), molecular model. Atoms are represented as spheres
Carbon nanotube, molecular model.

A further example of a two-dimensional nano substance is a multiwall carbon nanotube. Multiwall carbon nanotubes contain at least two concentric tubes of graphene and have some unique mechanical properties.

Multi-walled carbon nanotubes (MWNTs)..

Nanoparticles are incredibly useful substances. They are currently being used to address lots of our health and technological problems. It is predicted that they will be used even more in the future to make our lives easier and to make us even healthier. The following table describes some of the most important and well known applications of nanoparticles.

The Medical Field
Nanoparticles enable the early diagnosis of disease.
Nanoparticles enable the imaging of organs and tissue.
Nanoparticles result in drug delivery systems that reduce
side effects and improve healing.
Nanoparticles result in nanoscale devices used for dialysis.
Nanoparticles result in nanoscale robots that can remove
blood clots.
The Field of Agriculture
Nanoparticles enable the identification of bacteria
in different nutrients.
Nanoparticles are used in the preservation of food.
Nanoparticles improve the quality of
nutrients and pesticides.
Nanoparticles enable the development of new
treatments for plants and livestock with new
properties and features.
The Field of Energy
Nanoparticles enable the production of solar cells that are
more energy efficient.
Nanoparticles enable the production of hydrogen fuel cells
with improved performance.
The Field of Industry
Nanoparticles result in the creation of self-cleaning
glass and ceramics.
Nanoparticles enable sun-blocking properties in
cosmetics and creams.
Nanoparticles result in the creation of nanopaints
and nanosprays that provide layers of covering to protect
electrical devices from scratching.
Nanoparticles enable the development of new types
of tissues and fabrics that repel stains and are self cleaning.
The Field of Communications
Nanoparticles result in the creation of wireless
nanodevices for improved telecommunications and
satellite usage.
Nanoparticles enable the reduction in the size of the
transistor component in electronics.
Nanoparticles enable the production of smaller
electronic chips with high storage capabilities.
The Field of Environment
Nanoparticles enable the purification of air and water.
Nanoparticles result in improved nuclear
waste management.
Nanoparticles result in industrial waste
clearance and management.

Let us summarize what we have learned about nanoparticles.

Key Points

  • Nanoparticles are particles of matter that are between 1 and 100 nanometres (nm) in diameter.
  • Nanoparticles usually contain just a few hundred atoms, and they have very high surface-area-to-volume ratios.
  • Many nanoparticles are effective catalysts because they have such incredibly high surface-area-to-volume ratios.
  • Titanium dioxide nanoparticles are being used to make self-cleaning windows and sun creams.
  • Several metal nanoparticles have antibacterial properties.
  • Nanoparticles can be used as drug-delivery devices.
  • Buckyballs, graphene, and carbon nanotubes are carbon allotropes that are expected to have many important uses in the future.

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