JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year NANO MATERIALS Previous Question Paper (August/September - 2021 - R18)

Nanotechnology faces significant challenges that hinder its widespread industrial and clinical application:

• Manufacturing and Scalability: Producing nanomaterials with consistent size, shape, and purity at a commercial scale remains difficult. Achieving high-throughput synthesis without compromising structural integrity is a major bottleneck.
• Characterization: Measuring properties at the nanoscale requires advanced, expensive instrumentation like TEM, SEM, and AFM. Standardizing these techniques across different laboratories is challenging.
• Toxicity and Environmental Impact: The high reactivity and mobility of nanoparticles raise concerns regarding their long-term effects on human health and ecosystems. Their ability to cross biological barriers like the blood-brain barrier requires rigorous long-term safety studies.
• Cost and Energy: Many synthesis methods, such as chemical vapor deposition or laser ablation, are energy-intensive and costly, making them less viable for mass production.
• Regulatory and Ethical Issues: The lack of standardized safety regulations for nanomaterials creates legal uncertainty for manufacturers and potential risks for consumers.

Small things make a big difference at the nanoscale due to fundamental changes in physical, chemical, and biological properties that emerge when dimensions reach the sub-100 nm range. This shift is driven by two primary factors:

• Increased Surface-to-Volume Ratio: As particle size decreases, the percentage of atoms located on the surface increases dramatically. For example, a nanoparticle has a significantly higher proportion of surface atoms compared to a bulk material, leading to enhanced chemical reactivity, catalytic efficiency, and altered melting points.
• Quantum Confinement Effects: When the size of a material is reduced to the scale of the de Broglie wavelength of electrons, the continuous energy bands of bulk materials break into discrete, quantized energy levels. This leads to size-dependent optical, electrical, and magnetic properties. For instance, semiconductor quantum dots exhibit color changes based solely on their physical size due to the tuning of the bandgap.

These phenomena allow for the creation of materials with unprecedented strength-to-weight ratios, superior conductivity, and unique optical signatures, effectively enabling the design of materials with properties tailored at the atomic level.