Nanomaterials are materials with at least one dimension smaller than 100 nanometers, a size roughly 100,000 times smaller than the diameter of a human hair. At this scale, familiar substances like gold, carbon, and silver start behaving in unexpected ways, gaining new optical, electrical, and chemical properties that their larger counterparts don’t have. The global nanotechnology market is projected to reach roughly $220 billion by 2031, driven by applications in medicine, electronics, energy, and manufacturing.
What Makes the Nanoscale Special
The defining feature of nanomaterials isn’t just their size. It’s what happens to their physical and chemical behavior at that size. Two effects dominate: a massive increase in surface area and quantum-level changes in how electrons behave.
Surface area is the easier one to grasp. If you took a one-meter cube of any material and broke it into nanometer-sized fragments, the total surface area would increase by a factor of one billion. The material’s mass and composition stay the same, but far more of it is now exposed to its surroundings. That means more atoms are available to participate in chemical reactions. In lab experiments, 15-nanometer gold particles can drive chemical reactions that 200-nanometer gold particles of the same total mass simply cannot, purely because of the difference in exposed surface.
The second effect, quantum confinement, is subtler. In a bulk material, electrons move through continuous energy bands, much like cars on a highway. Shrink that material below about 20 nanometers and those bands break apart into discrete energy levels, more like a ladder with specific rungs. This changes how the material absorbs and emits light, conducts electricity, and interacts with magnetic fields. It’s why nanoscale cadmium sulfide particles glow different colors depending on their size, even though they’re chemically identical. The smaller the particle, the more its energy levels shift toward blue light.
Types of Nanomaterials by Shape
Scientists classify nanomaterials by how many of their dimensions fall below 100 nanometers.
- Zero-dimensional (0D): All three dimensions are nanoscale. These are essentially tiny dots. Quantum dots, nanoparticles, and fullerenes (soccer-ball-shaped carbon molecules) fall here.
- One-dimensional (1D): One dimension extends beyond the nanoscale while the other two remain tiny. Think of nanowires, nanorods, and carbon nanotubes, structures that are incredibly thin but relatively long.
- Two-dimensional (2D): Two dimensions extend beyond the nanoscale, leaving only the thickness at the nanometer level. Nanosheets and nano-coatings are examples. Graphene, a single-atom-thick sheet of carbon, is the most famous.
- Three-dimensional (3D): Larger structures built from nanoscale building blocks, such as nanoflowers, nanocubes, or self-assembled bundles of nanowires.
Nanomaterials Already Exist in Nature
Engineered nanoparticles get most of the attention, but nature has been producing nanomaterials for billions of years. A strand of DNA is 2.5 nanometers in diameter. A typical virus is about 100 nanometers wide. Bacteria and yeasts produce nanoscale particles of elemental sulfur and selenium as byproducts of their metabolism. Mineral wells rich in hydrogen sulfide naturally contain nanoscopic sulfur particles. Volcanic ash, soot from forest fires, and airborne mineral dust all include particles at the nanoscale.
The engineered versions differ in that they’re designed with precise sizes, shapes, and surface coatings to perform specific functions. That deliberate control is what makes them useful in technology and medicine.
Carbon-Based Nanomaterials
Carbon is the backbone of many of the most studied nanomaterials. Graphene, a flat sheet of carbon atoms arranged in a honeycomb pattern, conducts electricity exceptionally well. Researchers have measured electron mobility in suspended graphene exceeding 200,000 cm² per volt per second at room temperature, far higher than silicon. That property makes it attractive for next-generation electronics and energy storage devices.
Graphene quantum dots, tiny fragments of graphene typically under 10 nanometers, retain that electrical conductivity while also gaining the size-dependent optical properties of quantum dots. They can fluoresce under certain light, making them useful for biological imaging and chemical sensors. Carbon nanotubes, essentially graphene rolled into cylinders, combine high electrical conductivity with remarkable mechanical strength and have been explored for applications ranging from hydrogen storage to composite materials.
Medical Uses: Targeted Drug Delivery
One of the most promising applications of nanomaterials is delivering drugs directly to diseased tissue, particularly tumors. Conventional chemotherapy drugs circulate through the entire body, damaging healthy cells along the way. Nanoparticle-based drug delivery aims to concentrate the drug where it’s needed and reduce side effects elsewhere.
This works through two strategies. Passive targeting takes advantage of the fact that blood vessels around tumors are leakier than normal vessels, with gaps large enough for nanoparticles to slip through. Healthy tissue has tighter blood vessel walls, so the particles accumulate preferentially in the tumor. Active targeting goes a step further by attaching molecules to the nanoparticle surface that recognize and bind to specific receptors on cancer cells, essentially giving the drug a homing signal.
Both approaches depend on precise control over particle size, shape, and surface chemistry, exactly the kind of fine-tuning that nanoscale engineering allows.
How Nanomaterials Are Made
Manufacturing nanomaterials generally follows one of two strategies: top-down or bottom-up.
Top-down methods start with bulk material and carve it down to the nanoscale. Optical lithography uses light to etch patterns into surfaces and is the workhorse behind modern computer chip fabrication. Electron beam lithography achieves finer detail by using a focused beam of electrons instead of light. Nanoimprint lithography physically stamps nanoscale patterns into a material, offering a faster and cheaper alternative for certain applications.
Bottom-up methods build nanostructures atom by atom or molecule by molecule. Atomic layer deposition grows ultra-thin films one atomic layer at a time, giving precise control over thickness. Sol-gel fabrication uses chemical solutions that gradually form solid nanoscale structures as they dry and condense. Some researchers even use DNA strands as scaffolding, exploiting DNA’s natural tendency to self-assemble into predictable shapes to organize nanoscale electronic components.
Safety Concerns and Toxicity
The same properties that make nanomaterials useful also raise safety questions. Their small size allows them to enter cells through multiple pathways, most commonly through endocytosis, where the cell membrane wraps around the particle and pulls it inside. Some nanoparticles can also penetrate cell membranes directly, bypassing the cell’s normal intake machinery.
Once inside cells, the primary toxicity concern is the generation of reactive oxygen species, unstable molecules that damage DNA, proteins, and cell membranes. This oxidative stress can disrupt energy production in mitochondria, interfere with calcium signaling, trigger inflammation, and in some cases cause cell death. The extent of these effects depends heavily on the particle’s size, shape, surface coating, and chemical composition, which means broad statements about “nanomaterial safety” are difficult to make. A gold nanoparticle coated with a biocompatible polymer behaves very differently inside the body than an uncoated metal oxide particle of the same size.
How Nanomaterials Are Regulated
In the United States, the EPA regulates nanoscale materials under the Toxic Substances Control Act. Companies that manufacture or import nanoscale chemical substances must report specific information to the agency, including the chemical identity, production volume, manufacturing methods, exposure and release data, and any available health and safety data. The EPA can restrict uses of specific nanomaterials, require protective equipment for workers handling them, limit environmental releases, and mandate toxicity testing.
New nanoscale substances require premanufacture notification before they can enter commerce, giving the EPA a chance to evaluate potential risks before the material reaches consumers or the environment. The regulatory framework treats nanoscale versions of existing chemicals as distinct from their bulk counterparts, recognizing that size fundamentally changes how a substance behaves. This is still an evolving area, with agencies continuing to refine testing requirements as the science around nanotoxicology matures.