Jawaharlal Nehru Technological University Hyderabad B.Tech III NANOTECHNOLOGY Previous Question Paper (March - 2021 - R16)

The development and implementation of nanotechnology face several significant hurdles:

• Manufacturing Scalability: Transitioning from laboratory-scale synthesis to mass production while maintaining uniform particle size, shape, and purity remains difficult and costly.
• Toxicity and Health Risks: The unique properties of nanomaterials, such as high surface area and reactivity, may lead to unforeseen biological interactions, requiring extensive long-term toxicological studies to ensure safety for humans and the environment.
• Metrology and Characterization: Measuring and manipulating matter at the atomic scale requires highly sophisticated and expensive instrumentation, making precise quality control a major challenge.
• Regulatory and Ethical Issues: There is a lack of standardized international regulations regarding the handling, disposal, and labeling of nanomaterials, leading to concerns about environmental impact and public safety.
• Integration: Integrating nanoscale components into existing macro-scale systems and devices presents significant engineering challenges in terms of assembly and signal interfacing.

When materials are reduced to the nanoscale, they exhibit properties significantly different from their bulk counterparts due to two primary factors: the quantum confinement effect and the high surface-to-volume ratio.

• Surface Effects: As particle size decreases, the fraction of atoms located on the surface increases dramatically. This leads to higher surface energy and reactivity, which can enhance catalytic activity, alter melting points, and change chemical stability.
• Quantum Confinement: When the physical dimensions of a material become comparable to the de Broglie wavelength of electrons, the continuous energy bands of the bulk material split into discrete energy levels. This causes profound changes in optical, electrical, and magnetic properties. For example, semiconductors may exhibit size-dependent bandgaps, changing their light-absorption and emission characteristics.
• Mechanical Properties: Nanomaterials often exhibit increased hardness, strength, and ductility compared to bulk materials because the reduced grain size limits the movement of dislocations within the crystal lattice.
• Optical Properties: Materials like gold, which appear yellow in bulk, can appear red or purple at the nanoscale due to surface plasmon resonance, where conduction electrons oscillate in response to incident light.