Two-dimensional (2D) materials are a class of materials only one or a few atoms thick, giving them properties that differ dramatically from the same substance in bulk form. The most famous example is graphene, a single layer of carbon atoms arranged in a honeycomb lattice, first isolated in 2004. Since then, researchers have identified dozens of other 2D materials with unique electrical, optical, and mechanical behaviors. The global market for these materials is valued at roughly $1 billion in 2025 and is projected to reach $8.7 billion by 2035.
Why Thickness Changes Everything
When you shave a material down to just one or two atomic layers, electrons become confined in two dimensions instead of three. This confinement reshapes how the material conducts electricity, absorbs light, and transfers heat. A bulk chunk of molybdenum disulfide, for instance, has an indirect band gap of about 1.2 electron volts, meaning it absorbs and emits light inefficiently. Peel it down to a single layer, and the band gap becomes direct at roughly 1.8 eV. That shift makes the monolayer dramatically better at converting light into electrical signals or emitting light on its own.
Graphene illustrates the extremes of what 2D confinement can produce. Its electrons move with mobilities above 15,000 cm² per volt-second at room temperature, far outpacing silicon. Its thermal conductivity reaches 2,000 to 4,000 watts per meter-kelvin, the highest of any known material and roughly ten times better than copper. Yet graphene has no band gap at all, which means it can’t easily switch between “on” and “off” states the way a transistor needs to. That single limitation is why graphene alone can’t replace silicon in computer chips and why researchers have spent the past two decades exploring other 2D materials.
The Major Families
Graphene gets the headlines, but it’s only one branch of a growing family tree. The three categories that dominate current research are graphene, transition metal dichalcogenides (TMDs), and MXenes.
- Graphene is pure carbon, prized for extreme conductivity and mechanical strength. It excels in applications where you need to move charge or heat quickly: flexible electrodes, thermal management layers, and high-frequency sensors.
- TMDs are compounds pairing a transition metal (like molybdenum or tungsten) with sulfur or selenium. Materials like MoS₂ and WS₂ are semiconductors, meaning they have a band gap and can switch on and off. That makes them candidates for next-generation transistors, photodetectors, and LEDs. Their crystal structure can also be engineered into different phases: a semiconducting phase for active electronic layers, or a metallic phase useful as flexible electrodes.
- MXenes are made from layered metal carbides or nitrides with tunable surface chemistry. They combine high electrical conductivity with good transparency to visible light, making them promising replacements for the indium tin oxide coatings currently used in touchscreens and displays.
Beyond these three, researchers are working with black phosphorus (which shows exceptional capacity for storing sodium ions in batteries), hexagonal boron nitride (an excellent electrical insulator often used as a substrate for other 2D materials), and various other layered compounds.
How 2D Materials Are Made
The original method, famously, involved pressing Scotch tape against a chunk of graphite and peeling off thin flakes. This mechanical exfoliation still produces the highest-quality samples. Layers made this way show virtually no defects, and the number of layers in each flake can be precisely identified. The problem is scale: the flakes are tiny, typically ten microns or smaller, and they form uneven, stepped structures. You can’t build a commercial product from tape-peeled scraps.
Chemical vapor deposition (CVD) solves the scale problem. In CVD, carbon-containing gases flow over a heated metal surface and assemble into graphene films that can cover areas measured in square centimeters or larger. The thickness can be accurately controlled, and the cost is reasonable. The trade-off is quality. CVD-grown layers contain more defects than exfoliated ones, and those defects increase as the number of layers grows beyond two. For many practical applications, especially in coatings and composites, CVD quality is more than sufficient. For fundamental physics experiments that demand perfect crystal structure, exfoliation remains the standard.
Electronics and Optoelectronics
The semiconductor industry faces a fundamental scaling challenge: as transistors shrink below a few nanometers, silicon starts to leak current. TMDs like MoS₂ offer a potential path forward because their atomically thin channels can maintain sharp on/off switching at dimensions where silicon struggles. A monolayer of MoS₂ has a direct band gap of about 1.8 eV, which is precisely the threshold needed to cleanly toggle between conducting and insulating states.
In optoelectronics, 2D semiconductors are being developed for solar cells, photodetectors, LEDs, and even lasers. Their extreme thinness means they can be stacked and combined in ways that bulk materials cannot, opening the door to ultrathin, flexible devices. Researchers are working on all-2D photonic circuits where light sources, detectors, and waveguides are built entirely from layered materials integrated onto a single chip.
Energy Storage
The thin, flat geometry of 2D materials seems like a natural fit for batteries. Ions should be able to slip quickly between layers, enabling fast charging. Black phosphorus electrodes, for example, have demonstrated sodium-ion storage capacities of approximately 2,500 milliamp-hours per gram, among the highest of any battery material.
The reality is more complicated. Research published in ACS Nano found that the high aspect ratio of 2D nanosheets can actually slow ion movement through the liquid electrolyte inside a battery. When ions have to navigate around flat, overlapping flakes, the paths become tortuous. The study found that 2D-based electrodes were, on average, about 40 times poorer in rate performance than non-2D materials. This doesn’t erase their capacity advantage, but it means that simply being thin doesn’t guarantee fast charging. Electrode design, including how the sheets are spaced and oriented, matters enormously.
Medical and Biomedical Uses
The large, flat surface area of 2D materials makes them effective carriers for drug molecules. Graphene oxide nanosheets have been used for targeted delivery of chemotherapy drugs to cancer cells. By attaching a protein called transferrin to the nanosheet surface, researchers directed the drug-loaded sheets toward tumor cells that have an abundance of transferrin receptors on their surface, concentrating the treatment where it’s needed.
Black phosphorus nanosheets have been used to deliver gene-editing tools (specifically, the CRISPR-Cas9 system) directly into cells. Another class called layered double hydroxides responds to acidic environments by breaking down into biocompatible byproducts, which is useful because tumors tend to be more acidic than healthy tissue. That pH sensitivity allows the material to release its drug payload specifically at the tumor site.
MXenes and TMDs are also being explored for biosensing, photothermal therapy (using light to heat and destroy tumor cells), and medical imaging contrast agents.
Stability Remains a Challenge
Many 2D materials degrade quickly when exposed to air. Gallium telluride, for example, deteriorates rapidly after exfoliation. Its surface morphology, chemical composition, and even its directional physical properties change drastically during aging. The culprit is water vapor rather than oxygen or nitrogen: moisture in air interacts strongly with the material’s surface and drives the breakdown.
This instability is one of the primary hurdles to commercialization. A material that falls apart in ambient conditions can’t be used in consumer electronics or medical devices without protection. Surface treatments offer a path forward. Chemical functionalization, where small organic molecules are bonded to the material’s surface, has been shown to dramatically improve the shelf life of tellurium-based 2D materials in both normal and extreme conditions. Encapsulation with hexagonal boron nitride is another common strategy, essentially sandwiching the sensitive material between protective layers. These solutions work, but they add manufacturing complexity and cost.
The composite and coatings sector is currently the fastest-growing segment of the 2D materials market, in part because those applications are more forgiving of stability issues. Graphene mixed into a polymer coating, for instance, doesn’t face the same degradation risks as an exposed monolayer in a transistor. As stability solutions mature, the range of viable commercial applications will expand considerably.