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IGNOU MPHE-27 (January 2026 – December 2026) Assignment Questions
PART A
1.a) For an icosahedral cluster calculate the number of atoms present in its 7th shell. Find the total number of atoms in this cluster and its surface to bulk atom ratio.
b) Draw the LaMer diagram and explain the particle growth in its three regions.
2. a) Describe the set up used for ionized cluster beam (ICB) deposition. What are the advantages of this method?
b) Explain the steps of sol-gel synthesis of silica gel. Differentiate between the structure and method of formation of xerogel and aerogel.
c) What is meant by bio-template? With an example explain how it can be used in nanostructure synthesis. State the advantages of using green methods for nanomaterial synthesis.
3.a) Explain the structure and bonding pattern in C60 Fullerene. Which nanocrystalline allotropes of carbon are obtained using the electric arc deposition set-up with graphite rods?
b) What are Dirac point and Dirac cone in case of graphene? What are the specialties of a Dirac cone? What is the difference between graphene and graphyne?
4. a) Explain with examples, what are Janus particles. Which synthesis methods can be used to form such particles?
b) Calculate the surface plasmon energy of a metal with free electron density of 8×1027 m-3.
c) What are surface plasmon polaritons (SPP)? State any two technological applications of SPP.
d) What is exciton? What is the difference between Frenkel and Mott-Wannier excitons? Calculate the radius of an exciton in a semiconductor with dielectric constant E = 9.1, me = 0.2 and mh = 0.55.
PART B
5. a) Explain the difference between ballistic transport and normal (diffusive) transport in a material. Using the Landauer formula, calculate the conductance of a quantum device in which the conduction take place through three channels, each of which has a transmission coefficient T=1 .
b) Derive the expression for the conductivity matrix in integer quantum Hall effect.
6. a) What is the difference between single domain and superparamagnetic particles? A superparamagnetic material has a characteristic time of 10-11 seconds and a Néel relaxation time of 2.0 second at 300 K. Calculate
i) the energy barrier (in eV); and
ii) the blocking temperature if the measurement time is 120s.
Take kB = 8.62 x 10-5 eVK-1.
b) What are single negative and double negative materials? Explain with the help of a diagram, the characteristics of the propagation of electromagnetic waves through a double negative material.
c) Describe the property of band inversion in a topological insulator. Hence explain why a topological insulator cannot be transformed into a normal insulator.
7.a) Explain the construction and working principle of a microfluidic cantilever sensor. What is the resolution attained by such sensor?
b) Describe the detection mechanism of a virus with the use of Up-Conversion Nanoparticles (UCNPs).
8. a) What are triboelectric nanogenerators? Explain the different modes of their operation.
b) Describe the role of Nanotechnology in the reduction of air pollution.
c) Explain the lotus effect based on contact angle. Describe two practical applications of lotus effect.
