Nanomaterials: The Science of Matter at the Nanoscale

What defines a nanomaterial

A nanomaterial is any material with an internal or external structure on the nanoscale, conventionally defined as 1 to 100 nanometres in at least one dimension. The European Commission's 2011 recommendation, revised in 2022, uses a number-based threshold: a material qualifies if 50% or more of its constituent particles, by number, fall within that size range. The International Organization for Standardization (ISO) maintains a parallel vocabulary through its ISO/TC 229 technical committee.

Two physical facts explain why nanoscale matter behaves differently. The first is the surface-to-volume ratio. As a particle shrinks, the fraction of its atoms sitting on the surface grows dramatically - for a particle a few nanometres across, a large share of all its atoms are surface atoms, exposed and chemically reactive. This is why nanoparticles make such potent catalysts and sensors.

The second is quantum confinement. When a material's dimensions approach the wavelength of its electrons, those electrons can no longer be treated as if moving freely through bulk matter; their allowed energy levels become discrete and size-dependent. A semiconductor quantum dot changes the colour of light it emits simply by changing its diameter. These effects place nanomaterials at the intersection of classical materials science and quantum behaviour, a theme explored further in quantum materials and solid-state physics.

A short history, from Feynman to graphene

The conceptual starting point is usually traced to physicist Richard Feynman's 1959 lecture at Caltech, "There's Plenty of Room at the Bottom," in which he speculated about manipulating and arranging individual atoms. The word "nanotechnology" itself was coined later, by Norio Taniguchi in 1974.

The field became experimental reality in the 1980s and 1990s. In 1985 Harold Kroto, Richard Smalley and Robert Curl discovered buckminsterfullerene (C60), a soccer-ball-shaped carbon molecule - work that earned the 1996 Nobel Prize in Chemistry. In 1991 Sumio Iijima, at NEC in Japan, characterised carbon nanotubes: rolled cylinders of carbon atoms with extraordinary strength and conductivity. The invention of the scanning tunnelling microscope in 1981 by Gerd Binnig and Heinrich Rohrer (Nobel Prize 1986) gave researchers, for the first time, the ability to image and even move single atoms.

The modern era arguably crystallised in 2004, when Andre Geim and Konstantin Novoselov isolated graphene, a single layer of carbon, by peeling it from graphite with adhesive tape. Their work won the 2010 Nobel Prize in Physics and opened the still-expanding study of two-dimensional materials.

The main types of nanomaterials

Nanomaterials are often classified by how many of their dimensions fall on the nanoscale. This yields a useful taxonomy:

• Zero-dimensional (all three dimensions nanoscale): nanoparticles and quantum dots - including metal nanoparticles (gold, silver), metal-oxide particles (titanium dioxide, zinc oxide) and semiconductor quantum dots (cadmium selenide, indium phosphide) whose emission colour depends on size.
• One-dimensional (one dimension larger): nanotubes, nanowires and nanorods - carbon nanotubes and silicon nanowires are the archetypes, prized for conductivity and mechanical strength along their length.
• Two-dimensional (sheet-like, one dimension nanoscale): graphene and its relatives, hexagonal boron nitride, and transition-metal dichalcogenides such as molybdenum disulfide.
• Three-dimensional / nanostructured bulk: materials built from nanoscale building blocks - nanoporous solids, nanocomposites and aerogels - where the object itself is large but its internal architecture is nanoscale.
• Carbon nanomaterials as a family: fullerenes, nanotubes, graphene and nanodiamonds, all built from carbon yet spanning every dimensional class.

How nanomaterials are made

Synthesis strategies fall into two broad philosophies. Top-down approaches start with bulk material and carve it down: ball milling, lithography (the same patterning that defines microchips), and laser ablation. These methods scale well but struggle to reach the smallest sizes with atomic precision.

Bottom-up approaches build nanostructures atom by atom or molecule by molecule, exploiting self-assembly and controlled chemistry. Chemical vapour deposition (CVD) grows graphene sheets and carbon nanotubes on catalytic surfaces; sol-gel processing yields oxide nanoparticles and aerogels; colloidal chemistry produces uniform quantum dots; and molecular self-assembly lets components organise themselves through weak interactions. Bottom-up routes offer finer control over size and structure, which matters because, at the nanoscale, a few nanometres of size difference can change a material's colour, reactivity or band gap.

Precise fabrication is central to the wider study of nanomaterials and advanced materials, where controlling structure at the atomic level is the whole point.

Where nanomaterials are used

Nanomaterials are already embedded in everyday products, often invisibly. Their applications span several sectors:

• Catalysis: high surface area makes nanoparticles efficient catalysts in chemical manufacturing, fuel cells and vehicle catalytic converters.
• Medicine: nanoparticles carry drugs to targeted sites and sharpen MRI and imaging contrast, and lipid nanoparticles famously delivered the mRNA in COVID-19 vaccines. Silver nanoparticles are used for their antimicrobial action.
• Electronics and optics: quantum dots produce the vivid colours in QLED displays, while nanoscale features underpin modern transistors and sensors.
• Energy storage and harvesting: nanostructured electrodes increase the surface area and capacity of batteries and supercapacitors, a link explored in energy harvesting and energy conversion.
• Materials and coatings: titanium dioxide and zinc oxide nanoparticles provide transparent UV protection in sunscreens; carbon nanotubes and graphene reinforce lightweight composites; nanocoatings add scratch resistance and self-cleaning properties.

Nanomaterials in energy: the graphene bridge

Energy research is one of the most active frontiers for nanomaterials, precisely because nanoscale structure governs how efficiently a material can absorb, store or convert energy. Larger surface areas mean more sites for chemical reactions or charge storage, and engineered nanostructures can steer heat and electrons in useful ways. This connects nanomaterials to work on new energy technology and renewable energy innovations.

Graphene's role is central here. Because it is both highly conductive and mechanically responsive, researchers have studied whether the thermal motion of freestanding graphene - atomic-scale ripples driven by ambient heat - could be rectified into a small usable current, an idea investigated experimentally by Paul Thibado's group at the University of Arkansas. Building on such nanomaterials research, the Neutrino Energy Group, a Berlin research organisation founded in 2008, is developing an early-stage concept it calls neutrinovoltaic: a graphene-and-doped-silicon multilayer intended to harvest a portion of the energy already present in the surrounding environment. It is important to be precise: this is early-stage research, not a proven or purchasable product, and - like any physically legitimate energy technology - it could only convert energy already present in an open system, never create energy from nothing.

Safety, toxicity and regulation

The very properties that make nanomaterials useful - small size and high reactivity - also raise legitimate safety questions. Because nanoparticles can cross biological barriers that larger particles cannot, and because their behaviour does not always match the bulk material's known safety profile, toxicologists study them as a distinct class. The field of nanotoxicology examines how factors such as size, shape, surface chemistry and solubility influence whether a nanomaterial poses a hazard.

The evidence is mixed and material-specific rather than uniform. Some studies have found that certain long, rigid carbon nanotubes can produce inflammatory responses in lung tissue resembling those of asbestos fibres; other nanomaterials appear comparatively benign under normal exposure. The responsible position is caution and case-by-case assessment, not blanket alarm or blanket reassurance.

Regulators have responded. The European Union addresses nanomaterials under its REACH chemicals framework and requires labelling of nano-ingredients in cosmetics and food, while the U.S. Food and Drug Administration and Environmental Protection Agency apply existing statutes with nano-specific guidance. Standardised definitions and test methods remain a work in progress, which is why consistent international terminology matters so much.

Why nanomaterials matter

Nanomaterials represent a shift in how scientists design matter: instead of choosing from the fixed properties of known substances, they engineer new properties by controlling structure at the scale of atoms. That capability underlies advances across medicine, electronics, catalysis and energy, and it links directly to related frontiers in advanced materials, ceramics and composites, and the broader study of how structure dictates function.

The honest summary is that nanomaterials are neither a miracle nor a menace. They are a powerful and fast-maturing toolkit whose benefits are already tangible and whose risks are real, partly understood, and actively studied. Getting the science, the applications and the safety right - all three together - is what will determine how far the field goes.