THEORY EXAMINATION (SEM–IV) 2016-17 NANO SCIENCES

Course: B.Tech (All Branches – Common Elective)
Subject Code: EOE042
Subject Title: Nano Sciences
Exam Type: Theory
Duration: 3 Hours
Maximum Marks: 100

SECTION – A (10 × 2 = 20 Marks)

Short and conceptual questions covering key definitions and phenomena in nanoscience

SECTION – B (5 × 10 = 50 Marks)

Conceptual and analytical questions covering synthesis, properties, and instrumentation of nanomaterials

(a) Carbon Nanotubes (CNTs)

Cylindrical carbon molecules (single or multi-walled).

Properties: High tensile strength, thermal conductivity, and electrical mobility.

Applications: Nanoelectronics, composite reinforcement, drug delivery.

(b) Quantum Dot Laser & Superconductivity

Quantum Dot Lasers: Operate via discrete energy levels; low threshold current and tunable wavelength.

Superconductivity: Nanostructures can enhance critical current and magnetic flux pinning.

(c) Electron–Material Interaction & Gold Coating in SEM

Electrons interact through elastic scattering, inelastic scattering, and secondary emission.

Gold Coating: Applied on non-conductive samples to prevent charging, improve signal, and enhance imaging in SEM (Scanning Electron Microscope).

(d) Atomic Force Microscopy (AFM)

Working Principle: Uses a cantilever with a sharp tip to scan the surface; deflections measured via a laser beam.

Applications: Surface topography, nanomechanical property measurement, and molecular imaging.

(e) Nanomaterial Growth Techniques

Chemical Vapor Deposition (CVD)

Sol–Gel Method

Physical Vapor Deposition (PVD)

Thermal Evaporation – Material evaporated under vacuum, condenses on cooler substrate forming thin films.

(f) Graphene

Single layer of carbon atoms arranged in a 2D honeycomb lattice.

Properties: High electrical conductivity, mechanical strength, transparency.

Applications: Flexible electronics, sensors, batteries, and quantum devices.

(g) Localized Particles & Trap States

Donors: Add free electrons to conduction band.

Acceptors: Create holes in valence band.

Deep Traps: Defects deep within bandgap that capture carriers for long durations — crucial in photodetectors and semiconductors.

(h) Raman Spectroscopy

Principle: Inelastic scattering of photons (Raman effect).

Measures vibrational modes of molecules.

Applications: Characterization of CNTs, graphene, thin films, and molecular identification.

SECTION – C (2 × 15 = 30 Marks)

Long derivation and theory-based questions

Q3. Time-Dependent Schrödinger Equation

Derivation from classical wave mechanics:

iℏ∂Ψ∂t=H^Ψ=[−ℏ22m∇2+V(x)]Ψi \hbar \frac{\partial \Psi}{\partial t} = \hat{H}\Psi = \left[-\frac{\hbar^2}{2m}\nabla^2 + V(x)\right]\Psiiℏ∂t∂Ψ​=H^Ψ=[−2mℏ2​∇2+V(x)]Ψ

Explains probability amplitude evolution of quantum particles — fundamental to nanophysics and quantum confinement.

Q4. Inert Gas & Superfluid Clusters

Inert Gas Clusters: Argon, neon — form van der Waals bonded clusters at low temperature.

Superfluid Clusters: Exhibit zero viscosity and quantum coherence — used to trap and cool nanoparticles for quantum simulations.

Q5. Transmission Electron Microscopy (TEM)

Working: Electron beam transmitted through ultra-thin specimen → image formed based on scattering contrast.

Advantages: High-resolution imaging (~0.1 nm), crystallographic and compositional analysis.

Applications: Nanoparticle morphology, crystal defects, and phase identification.

Summary

This Nano Sciences (EOE042) paper comprehensively tests: