JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NANOTECHNOLOGY Previous Question Paper (August - 2022 - R16)

The history of nanotechnology began with Richard Feynman's 1959 lecture, There's Plenty of Room at the Bottom, where he proposed the possibility of manipulating matter at the atomic scale. The term nanotechnology was later coined by Norio Taniguchi in 1974. The field gained significant momentum in the 1980s with the invention of the Scanning Tunneling Microscope (STM) by Binnig and Rohrer, which allowed for the visualization and manipulation of individual atoms, and the discovery of fullerenes (C60) by Kroto, Smalley, and Curl in 1985, which opened the door to carbon-based nanomaterials.

Nanomaterials are classified based on their dimensionality, which refers to the number of dimensions that fall outside the nanometer range (typically below 100 nm):

• Zero-dimensional (0D) nanomaterials: All three dimensions are in the nanoscale. Examples include quantum dots, nanoparticles, and nanoclusters.
• One-dimensional (1D) nanomaterials: Two dimensions are in the nanoscale, while the third dimension is larger. Examples include nanotubes, nanowires, and nanorods.
• Two-dimensional (2D) nanomaterials: One dimension is in the nanoscale, while the other two are extended. Examples include graphene, thin films, and nanolayers.
• Three-dimensional (3D) nanomaterials: None of the dimensions are restricted to the nanoscale, but they are composed of nanostructured building blocks. Examples include bulk polycrystalline materials, dispersions of nanoparticles in matrices, and multi-nanolayer assemblies.

Beyond dimensionality, nanomaterials are also classified by their chemical composition into carbon-based materials (fullerenes, nanotubes), metal-based materials (gold/silver nanoparticles, metal oxides), dendrimers (nanoscale polymers), and composites.

The science and technology of nanomaterials has evolved from simple synthesis to the precise engineering of functional nanostructures, leading to transformative breakthroughs across multiple disciplines. Key developments include:

1. Advanced Synthesis and Bottom-Up Assembly: Modern techniques like atomic layer deposition (ALD) and molecular self-assembly allow for the construction of materials with atomic-level precision. This enables the creation of quantum dots, nanowires, and nanotubes with tailored electronic and optical properties.

2. Nanocomposites and Structural Materials: The integration of carbon nanotubes (CNTs) and graphene into polymer or metal matrices has produced materials with unprecedented strength-to-weight ratios. These are revolutionizing the aerospace and automotive industries by enabling lighter, more durable components.

3. Nanomedicine and Targeted Drug Delivery: Developments in functionalized nanoparticles, such as liposomes and dendrimers, have enabled site-specific drug delivery. This minimizes systemic toxicity in cancer therapy and enhances the efficacy of gene delivery systems.

4. Energy Storage and Conversion: Nanotechnology has significantly improved battery performance. The use of nanostructured electrodes, such as silicon nanowires and graphene-based anodes, increases surface area for ion transport, leading to faster charging rates and higher energy density in lithium-ion batteries. Additionally, perovskite-based nanostructured solar cells have achieved record-breaking power conversion efficiencies.

5. Nano-electronics and Photonics: The transition from traditional silicon-based transistors to field-effect transistors (FETs) utilizing 2D materials like molybdenum disulfide (MoS2) and black phosphorus is overcoming the physical limits of Moore's Law. Furthermore, plasmonic nanostructures are enabling the development of high-speed, low-power optical computing components.

6. Environmental Remediation: Nanomaterials such as zero-valent iron nanoparticles (nZVI) and photocatalytic titanium dioxide (TiO2) are being deployed for the efficient degradation of organic pollutants and heavy metal removal from water sources, providing sustainable solutions for environmental cleanup.