This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Synthesis of Nanoclusters”.
1. Ion sputtering makes use of highly energetic meta ions for bombardment.
a) True
b) False
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Explanation: Ion sputtering is a method that makes use of highly energetic inert gases like krypton and xenon ions for bombarding the surface. This produces an intense continuous beam of small singly ionized cluster of metals.
2. Why is DNA a promising template for the fabrication of silver nanocrystals?
a) DNA is chemically inert
b) High affinity of silver to cytosine
c) Lower binding sites of DNA
d) Greater oxidation of metals
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Explanation: Silver metals ions have a great affinity towards the cytosine bases present in the single stranded DNA molecule. Cytosine number in the loop can influence the stability and fluorescence of the nanoclusters. This makes DNA a promising template for synthesizing small silver nanoclusters. Moreover, larger and complex proteins possess more binding sites compared to short peptides making them more favorable for binding and reducing the metal ions.
3. Pick out the odd one from the following options.
a) Tiopronin
b) 3-mercaptopropionic acid
c) Tetrabutylammonium
d) Thiolate α-cyclodextrin
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Explanation: Tetrabutylammonium is a non-thiol based stabilizing agent used during electrochemical reduction of metal ions to metallic nanoclusters. Other compounds are thiol based stabilizing agents. The thiol-containing molecules are adopted as stabilizers in synthesis of nanoclusters because of their strong interaction with metals like silver, gold etc.
4. Electromagnetic rays cannot be used for the fabrication of nanoclusters.
a) True
b) False
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Explanation: Various electromagnetic waves such as gamma rays, microwaves, ultraviolet and infrared have been applied to reduce metal ions into metallic nanoclusters. Microwaves can produce fluorescent silver nanoclusters in PMAA that emit red colour. Gamma rays give silver nanoclusters in aqueous solution containing sodium polyacrylate or glutaric acid.
5. Pick the odd one out.
a) Tetrabutylammonium
b) Polyethylene glycol
c) Sodium hypophosphite
d) Dodecanethiol
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Explanation: Sodium hypophosphite is a reductant used to bring about chemical reduction for producing nanoclusters. However, the other compounds are stabilizing agents used during the electrochemical reduction process of formation of nanoclusters.
6. How are inorganic scaffolds like zeolites used to synthesize metal nanoclusters?
a) Applying UV light or two-photon excitation
b) Doping the metals
c) Using laser irradiation
d) Reducing the metal ions
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Explanation: Inorganic materials such as glass and zeolite have been used to synthesize metal nanoclusters. In zeolites, pores are present having size in the order of 10-10m. These can be impregnated with metal ions which can be then activated either by UV excitation, heat treatment or two-photon excitation. While this process is carried out, nanocluster formation takes place.
7. How does electrostatic stabilization occur in aqueous medium?
a) Diffusion of ions from the nucleophilic metal surface
b) Binding sterically bulk materials to metal surface
c) Development of the steric hindrance prevent close contact of metals
d) Formation of the electrical double layer
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Explanation: In aqueous medium there are two kinds of stabilization of nanoclusters taking place-steric and electrostatic. The electrostatic stabilization proceeds by the absorption of ions to the electrophilic metal surface, thus forming the electrical double layer. The Coulombic repulsion arising between the individual particles prevents agglomeration, hence bringing about the stabilization of the nanoclusters.
8. Which among the following compounds can form silver nanoclusters from silver ions?
a) NaBH4
b) K2Cr2O7
c) H2S2O8
d) OsO4
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Explanation: Nanoclusters can be formed by chemical reduction. It involves reduction of metal ions like silver into its nanoclusters. Some chemical reductants commonly used for this purpose are sodium borohydride (NaBH4) and sodium hypophosphite (NaPO2H2.H2O).
9. Name a method similar to laser vaporization method of nanocluster production.
a) Liquid-metal ion
b) Pulsed arc cluster ion
c) Seeded supersonic nozzle
d) Ion sputtering
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Explanation: Laser vaporization makes use of pulse laser to form the nanoclusters. A similar method using pulsed arc is used for nanoclusters synthesis. This method however uses an intense electric discharge instead of laser to vaporize the target metal.
10. Which of these is not an advantage of the nanoclusters formed using polymers?
a) Excellent quantum yield
b) Highly fluorescent
c) Multi-functional
d) Water – soluble
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Explanation: Polymers possessing abundant carboxylic acid groups were considered to be promising techniques for synthesizing highly fluorescent, water soluble silver nanoclusters. These stabilized nanoclusters have an excellent quantum yield and also have the property to sense the local environment.
Sanfoundry Global Education & Learning Series – Nanotechnology.
To practice all areas of Nanotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
