Chemistry | Nanomaterials & Dimensionality: Why Is It Important?

"Nanomaterials" is a broad term encompassing a vast array of materials that exhibit unique properties at the nanoscale—defined as dimensions between 1 and 100 nanometres. While breakthrough materials have recently received a surge of media attention, there has been a notable lack of discussion on the fundamental principles behind them.

As a result, the casual observer may not realise that scientists primarily define these materials by their dimensionality or fully appreciate how crucial they are set to become over the next decade. You see, nanomaterials won’t just revolutionise industries—they are poised to become an essential part of daily life, both at home and in the workplace, likely dethroning plastic as the new modern "wonder material".

With that change on the horizon, perhaps there has never been a more fitting time to learn how it all works.

Zero-Dimensional (0-D) Nanomaterials

Zero-dimensional nanomaterials, such as nanoparticles and quantum dots, have all three spatial dimensions confined to the nanoscale. As a result, the electrons in these materials are trapped in every direction, giving rise to a phenomenon known as quantum confinement.

Quantum confinement occurs when the dimensions of a material are reduced to a scale comparable to the de Broglie wavelength of electrons—typically below the exciton Bohr radius. In this regime, electrons become restricted in one or more spatial dimensions, and their energy levels become discrete rather than forming the continuous bands observed in bulk materials.

In simpler terms, when a material is made extremely small—around the same size as the typical wavelength of its electrons—the electrons are compelled to behave differently. Their movement becomes restricted in specific directions, meaning they can only exist at certain fixed energy levels, much like discrete steps on a ladder rather than spanning a continuous range. This leads to what is known as a quantised energy state.

This quantisation often imparts unique optical and electrical properties. For instance, in quantum dots, the confinement forces electrons into specific, quantised energy states, resulting in highly tunable optical characteristics—such as emitting light at very precise wavelengths. These attributes render quantum dots invaluable for applications including quantum computing, advanced display technologies, biomedical imaging, and optoelectronics.

Essentially, quantum confinement provides a versatile tool by allowing the properties of a material to be engineered through the control of its size and shape.

One-Dimensional (1-D) Nanomaterials

One-dimensional nanomaterials are defined by their striking shape: two out of their three dimensions—namely, the width and the thickness—are confined to the nanoscale (typically 1–100 nanometres), while the third dimension (length) extends well beyond that, often by several orders of magnitude.

Imagine a long, ultra-thin strand where the electrons are free to move along its length but are effectively trapped in the other two directions. This extreme confinement in width and thickness forces the electrons into discrete energy levels or sub-bands. The result is that the electronic states in these materials become quantised in exactly the same way as in their zero-dimensional counterparts. Once again, this quantisation dramatically changes the way electrons behave compared with those in bulk materials, where they are free to move in three dimensions.

In typical bulk materials, electrons are scattered frequently by imperfections, phonons (vibrations in the crystal lattice) and other electrons as they travel in all directions. However, in one-dimensional nanomaterials such as nanowires or nanotubes, electrons have a preferred direction for travel—along the length axis.

Because of the confinement in the other two directions, there are fewer available states into which electrons can scatter; this substantially reduces scattering events. In practical terms, it means that electrons can sometimes travel almost ballistically (i.e. with very little resistance or energy loss) along the length of the one-dimensional material. This remarkable property is pivotal in making these materials excellent candidates for advanced nanoelectronic applications. Nanodevices built from these materials can achieve higher performance and energy efficiency since the electrons are transported more cleanly and quickly.

Another fascinating aspect of these one-dimensional structures is their mechanical behaviour. Despite being extremely thin, these materials often exhibit extraordinary flexibility and tensile strength. Their elongated form allows them to bend without breaking—an attribute that is incredibly useful in applications such as flexible electronics or wearable devices. The high aspect ratio (length compared to width) also contributes to their overall strength and makes them excellent reinforcements when incorporated into composite materials.

The combination of unique electronic properties and mechanical robustness makes one-dimensional nanomaterials particularly attractive for a range of technological applications. In the field of nanoelectronics, for example, nanowires and nanotubes can be used to create transistors with superior electron mobility and lower power consumption. Their sensitivity to environmental changes—owing largely to their high surface-to-volume ratio—lends them greatly to sensor applications. They can detect minute changes in temperature, chemical composition or even mechanical strain, which is why they show promise as integral components in nanoscale sensors and smart devices.

On a more fundamental level, one-dimensional nanomaterials offer a fascinating playground for exploring novel quantum phenomena. Their reduced dimensionality means that many-body effects and other quantum behaviours that are typically masked in three-dimensional systems can become much more pronounced. 

This has led to extensive research into new states of matter and exotic behaviours such as Luttinger liquid phenomena in carbon nanotubes. In these systems, electrons, forced to interact strongly in a confined one-dimensional space, no longer behave as individual particles but instead form collective excitations, sometimes even displaying spin–charge separation, where the electron’s spin and charge propagate independently.

Two-Dimensional (2-D) Nanomaterials

Two-dimensional nanomaterials exhibit a unique geometry: one dimension—usually the thickness—is confined to the nanoscale (often just a few atoms thick), while the other two dimensions (length and width) extend over a much larger area. This extreme anisotropy—the material exhibits different properties when measured along various directions—creates a “sheet-like” structure that is radically different from bulk materials.

Graphene is the poster child for 2-D nanomaterials. It is essentially a single layer of carbon atoms bonded together in a hexagonal (honeycomb) lattice. This one-atom thickness (approximately 0.34 nanometres) means that electrons within graphene are confined in the vertical direction yet can move freely within the plane. This freedom, coupled with the arrangement of carbon atoms, results in a linear electronic energy dispersion characterised by Dirac cones—conical features in the band structure where conduction and valence bands meet, causing electrons to behave as if they are massless due to the linear relationship between energy and momentum. In other words, electrons in graphene behave as though they are massless, enabling extremely rapid and efficient electrical conduction. This extraordinary electron mobility underpins many of graphene’s potential applications in high-speed electronics and quantum devices.

The planar geometry of 2-D materials like graphene imparts several exceptional properties. Firstly, the extensive in-plane bonding network yields remarkable mechanical strength and flexibility; graphene, for instance, is not only incredibly strong but also very stretchable and pliable. Secondly, the atomic thinness contributes to a high surface-area-to-volume ratio, which is advantageous for applications that rely on surface interactions—such as sensing, energy storage and catalysis. Additionally, the planar nature facilitates efficient heat dissipation, making these materials excellent candidates for thermal management in electronic devices.

Essentially, two-dimensional nanomaterials bridge the gap between atomic-scale phenomena and macroscopic applications. They provide a platform where quantum effects can be harnessed in practical devices, paving the way for significant breakthroughs in electronics, optics and materials science.

Three-Dimensional (3-D) Nanomaterials

Unlike 1-D or 2-D nanomaterials, which are significantly confined in one or two dimensions, 3-D nanomaterials consist of one or more types of nanoscale building blocks (such as nanowires, nanoparticles, or nanotubes) that are assembled into a bulk structure. Each of these components retains its intrinsic nanoscale properties—be it an enhanced catalytic activity, unique electronic behaviour, or remarkable mechanical strength—while being integrated into a larger, robust framework.

Imagine constructing a mosaic where each tile (the nanoscale component) has distinct functionalities that collectively contribute to a macroscopic piece that is both strong and versatile.

The strength of 3-D nanomaterials lies in the enhanced functionalities bestowed by their nanoscale constituents. For instance, nanoparticles with a high surface-to-volume ratio may display superior catalytic behaviour compared to their bulk counterparts. When these are embedded within a composite material, the overall system can catalyse chemical reactions at rates far exceeding those of conventional materials. Similarly, incorporating networks of nanowires provides continuous conductive pathways. Despite being part of a three-dimensional structure, these pathways allow for efficient electron transport and can yield electrical properties that are critical in high-performance sensors or electronic devices. The key point is that the holistic properties of the composite are not simply an average of its parts but are amplified by the interactions at the nanoscale.

Although the assembled 3-D material appears similar to conventional bulk materials from a structural standpoint, its internal architecture is entirely different. The distributed nanoscale elements create a material that often displays unusual mechanical behaviour, such as increased toughness or flexibility. The nanoscale network acts as an internal reinforcement, enabling the material to absorb energy, dissipate stresses, and perform reliably under challenging conditions—qualities essential for advanced structural applications in aerospace, biomedical devices, or high-performance engineering.

In essence, three-dimensional nanomaterials serve as a bridge between the nanoscale and the macroscale. They harness the extraordinary properties of individual nanoscale entities while forming a bulk material with far superior functionalities.

The TLDR: So, Nanomaterials & Dimensionality: Why Is It Important?

Because the degree of confinement determines the exact effect or property a nanomaterial exhibits, the way electrons and other particles move within these materials depends significantly on how confined they are. When dimensions are reduced to the nanoscale, quantum mechanical effects become pronounced, leading to a variety of phenomena.

This dimensional classification not only helps us understand the fundamental physics at play but also guides researchers in tailoring materials for specific applications—whether that's creating more efficient solar cells, stronger, lighter materials or novel electronic devices.

Citations: