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Introduction to Nanomaterials

Joydip Sengupta1, Arpita Adhikari2, and Chaudhery Mustansar Hussain3

1Department of Electronic Science, Jogesh Chandra Chaudhuri College, Kolkata, 700033, India

2Department of Electronics and Communication Engineering, Techno Main Salt Lake, Kolkata, 700091, India

3Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ, 07102, USA

1.1 Introduction

1.1.1 Definition and Size Range

Nanomaterials [1] constitute a pivotal class of advanced materials characterized by at least one dimension confined within the nanoscale regime, typically ranging from 1 to 100 nm. To contextualize this scale, a nanometer equates to one-billionth of a meter, rendering it approximately 100,000 times smaller than the diameter of a human hair (Figure 1.1). Within this regime, classical physical laws often yield to quantum mechanical phenomena [2], imparting unique physicochemical properties to these materials that markedly deviate from those of their bulk analogs.

The definitional framework for nanomaterials is not purely theoretical [4]; it bears substantial relevance across regulatory, research, and commercial domains. Although variations exist among definitions proposed by international standardization bodies, a broad consensus centers on the 1-100 nm dimensional criterion. This range delineates a transitional regime in which atomic- and molecular-scale interactions begin to dominate material behavior, surface area-to-volume ratios increase dramatically, and quantum confinement effects become significant, thus governing the emergent properties of these materials.

1.1.2 Classification by Dimensionality

Nanomaterials are systematically classified based on the number of dimensions confined within the nanoscale (Figure 1.2), a categorization that provides predictive insight into their behavior and potential applications.

• Zero-dimensional (0D) nanomaterials are confined in all three spatial dimensions at the nanoscale. Representative examples include nanoparticles, quantum dots, and nanoclusters [5]. These systems exhibit pronounced quantum confinement effects in all directions, leading to discrete energy states and distinctive optical and electronic behavior. For instance, quantum dots demonstrate size-dependent photoluminescence [6], which has proven invaluable in applications such as biological imaging and next-generation display technologies [7].

  Figure 1.1 Size of different objects and natural organisms.

  Source: Reproduced with permission from Loos [3] / Elsevier.

  Figure 1.2 Categorization based on dimensionality.

• One-dimensional (1D) nanomaterials possess two dimensions within the nanoscale, while the third dimension extends to the microscale or beyond. This class encompasses nanorods, nanowires, nanofibers, and nanotubes. Carbon nanotubes (CNTs) [8], a paradigmatic 1D material, are renowned for their exceptional mechanical strength and tunable electronic properties, which range from metallic to semiconducting depending on chirality and structural configuration. Such attributes render them indispensable in nanoelectronics [9] and multifunctional composite systems.
• Two-dimensional (2D) nanomaterials are characterized by nanoscale confinement in one dimension, typically thickness, with the other two dimensions extending laterally. Graphene [10], a monolayer of sp2-hybridized carbon atoms arranged in a hexagonal lattice, exemplifies this category and has garnered widespread attention for its superlative electrical conductivity, mechanical robustness, and thermal stability. Other noteworthy 2D materials include hexagonal boron nitride, transition metal dichalcogenides (e.g., MoS2) [11], and layered oxides, all of which are at the forefront of research in flexible electronics, energy storage, and photonics.
• Three-dimensional (3D) nanomaterials comprise macroscopic structures incorporating nanoscale constituents or features, such as nanocrystalline materials, nanocomposites, and hierarchically porous systems [12]. Although their overall dimensions exceed the nanoscale, the inclusion of nanoscale domains endows these materials with enhanced functionalities, including improved mechanical properties, catalytic activity, and transport characteristics.

1.1.3 Natural Versus Engineered Nanomaterials

Distinguishing between natural and engineered nanomaterials is essential for comprehending the ubiquity of nanoscale phenomena in nature and the extent of human agency in tailoring these effects for technological advancement.

Natural nanomaterials have existed since geological antiquity, generated through a multitude of biogenic, atmospheric, and geophysical processes. Examples encompass nanoparticles present in volcanic ash [13], sea spray aerosols [14], and wildfire smoke [15]. Biological systems are particularly rich in natural nanostructures, such as the hierarchical organization of hydroxyapatite in bone [16], the nanostructured cuticles of lotus leaves conferring superhydrophobicity [17], and the photonic nanostructures found in butterfly wings and peacock feathers [18], which exhibit structural coloration via optical interference rather than pigmentation.

In contrast, engineered nanomaterials are synthetically designed and fabricated through deliberate interventions in materials processing. These efforts leverage advances in chemistry, physics, and materials science to control morphological, compositional, and surface attributes with atomic or molecular precision. Engineered nanomaterials have unlocked unprecedented functionalities, including tunable bandgaps [19], tailored catalytic behavior [20], and the development of metamaterials with negative refractive indices [21] or programmable self-assembly [22]. Their development reflects a culmination of decades of interdisciplinary research and remains central to innovations across sectors such as energy, biomedicine, and nanoelectronics.

1.2 Historical Development of Nanoscience

1.2.1 Ancient Applications

Although the term "nanotechnology"is a product of modern scientific discourse, empirical utilization of nanoscale phenomena can be traced back to antiquity. Historical artisans and metallurgists, despite lacking theoretical understanding, exploited nanoscale effects through empirical methods refined over centuries.

One of the earliest and most notable examples is the incorporation of noble metal nanoparticles in ancient glassmaking. The Lycurgus Cup [23], a fourth-century Roman artifact, exemplifies this phenomenon. This dichroic vessel appears green under reflected light and red when backlit, an optical behavior now attributed to surface plasmon resonance effects induced by embedded gold and silver nanoparticles within the glass matrix (Figure 1.3). Similarly, medieval European glassmakers achieved vivid ruby-red hues in stained glass through the dispersion of colloidal gold [25], albeit without any knowledge of the underlying nanoscale interactions [26].

In the domain of metallurgy, the production of Damascus steel by ancient blacksmiths remains a remarkable illustration of unintentional nanoscale engineering [27]. Modern materials analysis has revealed that the exceptional sharpness and durability of Damascus blades stem from the formation of CNTs [28] and cementite nanowires embedded within the steel microstructure, features generated through specific thermomechanical forging regimes that have since been lost to history.

These historical examples underscore the long-standing, albeit unconscious, engagement of human civilization with nanoscale materials phenomena.

Figure 1.3 The Lycurgus Cup, an ancient Roman feat of pioneering nanotechnology in the fourth century, exhibited at the British Museum.

Source: OIST [24] / Okinawa Institute of Science and Technology Graduate University / CC BY 4.0.

1.2.2 Twentieth-Century Foundations and Key Milestones

The formal conceptualization of nanoscience emerged in the mid-twentieth century through theoretical propositions and the advent of tools capable of interrogating and manipulating matter at the atomic scale. The seminal moment occurred with Richard Feynman's visionary 1959 lecture, "There's Plenty of Room at the Bottom," delivered at the California Institute of Technology [29]. In this address, Feynman speculated about the feasibility of manipulating atoms individually, thereby anticipating many of the principles that would later define nanotechnology.

Progress during the 1960s and 1970s was driven primarily by advances in surface science and the development of high-resolution characterization techniques. Electron microscopy enabled the first direct visualization of nanoscale structures [30], while emerging thin-film deposition methods [31] allowed controlled construction of layered materials at the atomic scale. This period laid the empirical groundwork...