Nanoparticle

Some things are very, very small.

These are called nanoparticles. They are smaller than a speck of dust. You cannot see them with your eyes. You need a special tool to see them.

These tiny bits can be many shapes. Some look like stars. Some look like rods or cubes. They can even be shaped like flowers. These small shapes help them do special jobs. They are used to make paints and plastics. They are even found in nature. Some tiny germs are this small too.

A nanoparticle is a tiny bit of matter.

It is very small. Most are between 1 and 100 nanometres wide. A nanometre is a tiny unit of measure. These particles are much smaller than a speck of dust. You cannot see them with a regular microscope. Instead, you must use an electron microscope.

Because they are so small, they act in special ways. For example, they do not sink to the bottom of liquids. They also let light pass through them easily. This can make a liquid look clear. Nanoparticles come in many shapes. Some look like stars.

Others look like rods, cubes, or even flowers. Their shape helps them do different jobs.

These tiny bits are found in nature. Some viruses are this small. They are also used to make things like paint and plastic. Scientists can even make them in a lab. This study is called nanotechnology. They use these small parts to make new and useful products.

A nanoparticle is an incredibly tiny bit of matter.

Most of these particles are between 1 and 100 nanometres wide. A nanometre is a very small unit of measurement. These particles are much smaller than a speck of dust. Because they are so small, they act in unique ways. They have different physical or chemical properties than larger pieces of the same material. This makes them very important to study in science.

These tiny particles work in interesting ways. Because they are so small, they do not sink to the bottom of liquids. They stay floating due to something called Brownian motion. They are also smaller than the waves of visible light. This means they cannot be seen with a regular microscope. Scientists must use an electron microscope or a laser microscope to see them.

Because light passes through them, a liquid filled with them can look clear. This is different from larger particles that scatter light.

People have used these tiny particles for a long time. Artisans used them in prehistory without even knowing what they were. For example, Roman glassmakers used them in the 4th century CE. They made a special cup called the Lycurgus cup. In the 9th century CE, people in Mesopotamia used silver and copper particles in pottery.

Later, in 1857, Michael Faraday wrote about how metal particles look under light. In the 1990s, the term nanoparticle became much more common in science.

Nanoparticles come in many different shapes and sizes. Some look like spheres, but others look like rods or cubes. You can even find shapes like nanostars, nanoflowers, or nanoboxes.

Some particles are even shaped like stars or reefs. Scientists can make these shapes by controlling how they grow. The shape can change how the particle acts. For example, gold or silver particles can have beautiful colors. These colors change depending on the shape of the particle.

These tiny bits are all around us in the real world. They occur naturally in the air and in space. Thousands of tons of interplanetary dust fall to Earth every year. Much of this dust is in the nanoparticle range. Many viruses are also this small. We also use them to make everyday things. They are ingredients in paints, plastics, and even magnetic products. Scientists use nanotechnology to build new things with these small parts.

A nanoparticle is a tiny particle of matter with dimensions typically between 1 and 100 nanometres (nm).

While the term is sometimes applied to larger particles up to 500 nm, or to tubes and fibers that are narrow in two directions, it describes a unique scale of existence. These particles are much smaller than microparticles, which range from 1 to 1000 micrometers (μm). They are also distinct from fine particles and coarse particles. At the smallest scale, metal particles smaller than 1 nm are usually called atom clusters. Nanoparticles are important because their tiny size creates physical and chemical properties that differ from the bulk material.

The unique behavior of nanoparticles is driven by their scale. Because they are so small, they are highly subject to Brownian motion, which is the random movement of particles in a fluid. This motion prevents them from settling or sedimenting like larger particles might. They are also much smaller than the wavelengths of visible light, which range from 400 to 700 nm. Because of this, nanoparticles cannot be seen with ordinary optical microscopes. Instead, scientists must use electron microscopes or laser microscopes to observe them.

Furthermore, dispersions of nanoparticles in transparent media can remain transparent. This happens because they do not scatter light in the same way that larger suspensions do. They can also pass easily through common ceramic filters, requiring special nanofiltration for separation.

One reason for these unique properties is the high surface-to-volume ratio. Since a typical atom has a diameter between 0.15 and 0.6 nm, a large fraction of a nanoparticle's material sits near its surface. This means the properties of the surface layer can dominate the behavior of the entire particle. This effect is even stronger when nanoparticles are dispersed in a medium made of a different composition. The interactions at the interface between the nanoparticle and the surrounding material become very significant. This transition between bulk materials and atomic structures allows for phenomena not seen at other scales.

Nanoparticles come in many different shapes, which is known as morphology. Common shapes include nanospheres, nanorods, nanochains, and nanoboxes. Some even resemble more complex structures like nanostars, nanoflowers, or nanoreefs.

The shape of a particle can be determined by its intrinsic crystal habit or by its environment. For example, coating additives can inhibit crystal growth on certain faces. Non-spherical nanoparticles, such as prisms or cubes, exhibit anisotropy. This means their physical and chemical properties change depending on their shape and size. In gold, silver, or platinum, these shapes can even change the colors seen in colloidal solutions.

Creating these particles involves a process called nucleation and growth. Nucleation is the foundation of synthesis and sets the stage for the particle's final size and shape. There are two main types: homogeneous nucleation, where nuclei form uniformly throughout a phase, and heterogeneous nucleation, where they form on surfaces or impurities. To control the final product, scientists often use the LaMer model. This model describes three steps: a rapid increase in monomer concentration, fast nucleation characterized by explosive growth, and finally, growth controlled by the diffusion of monomers. Controlling these steps allows for the creation of monodisperse products, which have a uniform size.

Humans have interacted with nanoparticles for much of history, even without knowing their scientific name. Artisans in prehistory used them in glassmaking and pottery. For instance, the Roman Lycurgus cup from the 4th century CE used nanoparticles to create dichroic glass. In the 9th century CE, Mesopotamian lusterware used silver and copper nanoparticles in its glaze.

In 1857, Michael Faraday provided the first scientific description of how metal nanoparticles interact with light. In the 20th century, researchers used the term "ultrafine particles" until the 1990s, when the National Nanotechnology Initiative helped make the term "nanoparticle" more common.

Today, nanoparticles are essential to many fields and natural processes. They occur naturally in interplanetary dust, which falls to Earth at rates of thousands of tons per year. They are also found in atmospheric dust and within many viruses. In industry, they are key ingredients in paints, plastics, metals, and ceramics. Scientists use them in medicine, such as using liposomes as delivery systems for vaccines or anticancer drugs. By studying the transition between atoms and bulk matter, nanotechnology continues to expand our ability to build new materials.