In this blog post, we’ll explore the meaning and characteristics of nanoparticles, as well as why they are important in modern science and technology and their potential applications.
When asked what “nano” means, many people think of cutting-edge science and technology or consider it a somewhat unfamiliar concept. However, today it’s not uncommon to come across terms like IT, BT, and NT (Nano Technology). So, what exactly is NT, and why has it established itself as such an important field of technology?
“Nano” is actually just a prefix used to denote the size of an object. It is similar to “kilo” in kilometer (km) or “milli” in millimeter (mm). A nanometer (nm) equals 10⁻⁹ m, while a micrometer (μm) equals 10⁻⁶ m. Units smaller than these include pico (10⁻¹²) and femto (10⁻¹⁵). In other words, “nano” is simply a unit denoting a size of 10⁻⁹.
However, when asked what a nanoparticle is, it is common to answer that it is a particle so small it cannot be seen with the naked eye, rather than explaining the unit itself—and in fact, this explanation is appropriate. So why are these tiny particles called “nanoparticles” rather than “microparticles” or “picoparticles”? The reason is that the size of molecules and atoms is on the nanometer (nm) scale. The smallest particles that can be created using these atoms and molecules fall within the nanoscale, and “nanoparticles” refer to the smallest particles that can be made from molecules.
So why do we go to such lengths to create the smallest particles—ones that are invisible to the naked eye and extremely difficult to produce? The reason becomes clear when we compare nanoparticles with particles of a typical size visible to the naked eye. For a given mass of material, nanoparticles have a much larger surface area than conventional particles. While this may seem like a simple fact, it is precisely this characteristic that makes nanoparticles so significant.
This may raise a question. If the goal is to increase surface area, wouldn’t it suffice to simply grind a material into small particles? Why, then, do we insist on the much more difficult-to-produce nanoscale? To understand this, we need to examine the concept of “surface energy.” Since surface energy is a somewhat abstract concept, it is helpful to first understand “surface tension,” a concept closely related to it and familiar to many people.
Take water as an example: the molecules inside the liquid exchange attractive forces with surrounding molecules in various directions, achieving a balance of forces. In contrast, molecules on the surface do not experience an upward attractive force because there are no molecules above them. As a result, surface molecules are subjected to a force pulling them inward, and overall, this force acts to minimize the surface area as much as possible. This is surface tension. The phenomenon of a water droplet maintaining a spherical shape in zero gravity is also a classic example of this surface tension.
Surface energy is closely related to this surface tension. Just as basic physics concepts explain energy through the relationship between force and distance, surface energy can be understood by considering the relationship between surface tension and surface area. Even without delving into complex derivations, it is easy to see that surface energy increases as the same amount of material is divided into as many small particles as possible to maximize the surface area.
However, this surface energy has almost no effect on particles of a typical size visible to the naked eye. This is why we hardly notice any difference in properties between large and small water droplets. On the other hand, when particle size is reduced to the nanoscale, surface energy becomes significant enough to be impossible to ignore, and various phenomena that do not occur in particles of typical size begin to emerge. For this reason, nanoparticles can exhibit properties that were difficult to achieve with conventional materials, which is a key reason why research on nanoparticles remains active to this day.
Because nanoparticles have very high surface energy, they have a strong tendency to stick together. Consequently, when attempting to manufacture bulk materials using nanoparticles under typical conditions, the nanoparticles often agglomerate into larger particles at the micrometer scale. For this reason, it is difficult to stably produce or utilize nanoparticles using simple methods alone. Ultimately, producing nanoparticles requires precise manufacturing techniques and meticulous process control, and the manufacturing process itself is highly complex. If you wish to learn more about these manufacturing methods, it is helpful to consult relevant research papers or specialized literature.
Although manufacturing is challenging, the potential applications of nanoparticles are vast. For example, designing pharmaceuticals in nanoparticle form allows for more effective delivery of drugs to specific sites within the body, which is why this area is actively being researched in the field of drug delivery technology. Additionally, gold nanoparticles are used as catalysts and demonstrate high efficiency in the reaction that oxidizes carbon monoxide into carbon dioxide; they are also utilized in deodorization and environmental remediation technologies. Titanium dioxide (TiO₂) nanoparticles exhibit properties such as sterilization, self-cleaning, and anti-fogging when exposed to ultraviolet light, and are used in various industrial fields, including construction materials and coatings.
As such, even when made of the same material, nanoparticles exhibit very unique physical and chemical properties compared to particles of conventional size, and these properties are widely utilized across various industries and fields of science and technology. However, due to their extremely small size, they are difficult to observe directly with a standard optical microscope and require precision analytical equipment. Furthermore, since some nanomaterials may be inhaled by humans, research on their safety and toxicity is ongoing. Nevertheless, nanotechnology plays a crucial role in core areas of modern science and technology—such as semiconductors, energy, biotechnology, the environment, and medicine—and is expected to continue driving various technological innovations in the future.
