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

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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

No.	Term	Description
(a)	Nano Diamond	Carbon material with nanocrystalline diamond grains; exhibits extreme hardness, high thermal conductivity, and chemical stability.
(b)	Quantum Dots	Semiconductor nanocrystals exhibiting size-dependent optical and electronic properties due to quantum confinement.
(c)	Fullerenes	Allotropic carbon molecules (C₆₀, C₇₀, etc.) forming spherical cage-like structures — used in drug delivery, superconductors.
(d)	Luminescence	Emission of light by a substance not resulting from heat (includes fluorescence and phosphorescence).
(e)	Face-Centered Cubic (FCC) Nanoparticles	Crystalline structure with atoms at cube corners and face centers (e.g., Au, Ag, Ni). Stable and dense packing.
(f)	Lattice Vibrations	Oscillations of atoms about their equilibrium positions — quantized as phonons.
(g)	Excitons	Bound state of an electron and a hole attracted by Coulomb force in semiconductors.
(h)	Magic Numbers	Specific cluster sizes of atoms that are unusually stable due to closed electronic shells.
(i)	Fermi Surfaces	Surfaces in momentum space separating occupied from unoccupied electron states at absolute zero.
(j)	Trap Levels	Energy levels within the bandgap that trap charge carriers, influencing conductivity and luminescence.

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:

Topic Area	Concepts Covered
Nanomaterials	CNTs, fullerenes, quantum dots, graphene
Characterization Tools	AFM, SEM, TEM, Raman spectroscopy
Quantum & Solid-State Physics	Schrödinger equation, excitons, Fermi surfaces
Growth & Fabrication	CVD, PVD, thermal evaporation
Applications	Electronics, energy storage, medicine, and sensors