JNTU B.Tech III NANOTECHNOLOGY Previous Question Paper (February - 2022 - R16)

Nanomaterials in nature exhibit unique properties due to their high surface-to-volume ratio, quantum confinement effects, and surface energy. These properties include enhanced chemical reactivity, altered magnetic and optical characteristics, and superior mechanical strength compared to their bulk counterparts. In the biological world, nanophenomena are fundamental to life processes:

• Molecular Recognition: Biological systems operate through precise nano-scale interactions, such as enzyme-substrate binding and DNA base pairing, which rely on specific structural geometries.
• Self-Assembly: Proteins and lipid bilayers spontaneously organize into functional structures like cell membranes and organelles, driven by non-covalent interactions at the nanometer scale.
• Structural Coloration: Many organisms, such as butterfly wings and peacock feathers, derive vibrant colors from nanostructured surfaces that cause thin-film interference or diffraction of light rather than pigments.
• Superhydrophobicity: The lotus effect, observed in various plants, utilizes hierarchical nano-scale surface roughness to minimize the contact area of water droplets, resulting in self-cleaning surfaces.
• Biomineralization: Organisms like diatoms and mollusks synthesize complex, highly ordered inorganic nanostructures (e.g., silica shells or calcium carbonate nacre) under ambient conditions.

The mechanism of self-cleaning textiles primarily relies on the Lotus Effect, which involves achieving superhydrophobicity through surface engineering. This is typically implemented using two approaches:

1. Surface Roughness: By coating textile fibers with nano-scale particles (such as silica or titanium dioxide), a hierarchical structure is created. This roughness traps air pockets between the fiber surface and a water droplet, significantly reducing the solid-liquid contact area.
2. Low Surface Energy: The fibers are treated with hydrophobic chemicals, such as fluorocarbons or silanes, which lower the surface energy of the fabric.

When these conditions are met, the water droplet maintains a nearly spherical shape with a high contact angle (typically >150°). As the droplet rolls off the surface due to gravity or slight tilting, it picks up dust, dirt, and contaminants, effectively cleaning the fabric without the need for detergents or mechanical agitation. Some textiles also utilize Photocatalysis, where titanium dioxide nanoparticles decompose organic stains when exposed to UV light.