This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Production of Graphene – Set 3”.
1. Choose the correct order for graphene production via Ion implantation.
a) Application of electric field ➜ Creation of graphene layer ➜ High temperature activation annealing ➜ Acceleration of carbon ions onto substrate
b) Acceleration of carbon ions onto substrate ➜ Application of electric field ➜ High temperature activation annealing ➜ Creation of graphene layer
c) Application of electric field ➜ Acceleration of carbon ions onto substrate ➜ High temperature activation annealing ➜ Creation of graphene layer
d) High temperature activation annealing ➜ Application of electric field ➜ Acceleration of carbon ions onto substrate ➜ Creation of graphene layer
View Answer
Explanation: Graphene can be created on silicon using ion implantation method. In this process carbon ions are accelerated, by an electric field, onto a layered surface comprising of nickel, silicon dioxide and silicon. The nickel layer acts as a catalyst for graphene synthesis and has high solubility for carbon. The process then involves high temperature activation annealing to form a honeycomb lattice of graphene on the substrate.
2. Which of the following indicates the advantage of CVD for graphene production?
a) Dislocations, wrinkles arise in graphene sheets during the process
b) Complicated process using sophisticated machineries
c) Impervious and hard graphene obtained
d) Production of toxic and corrosive gases
View Answer
Explanation: CVD, so far has been the most widely used method for graphene production. It produces hard, high quality and impervious graphene in large scale. Though this method has many advantages as mentioned, yet there are a few downsides to this method which makes its use limited. These include i) production of corrosive and toxic gases, ii) difficulty in controlling the thickness of graphene formed, iii) defects and disorders arising in graphene lattice, iv) complex method.
3. Which method uses oxidizing agents to convert graphite into graphite oxide for the production of graphene?
a) Chemical vapour deposition
b) Sonication
c) Ion implantation
d) Hummer’s method
View Answer
Explanation: Hummer’s method uses oxidizing agents such as potassium permanganate (KMnO4) to oxidize graphite to graphite oxide (GO). This is further reduced to graphene using reducing agents such as hydrazine. The modern modified Hummer’s method is carried out in three basic steps- oxidation, reduction and post-treatment.
4. What kind of laser is used for the production of porous three-dimensional graphene films from commercial polymer films?
a) Ruby laser
b) Helium Neon laser
c) CO2 infrared laser
d) Chemical laser
View Answer
Explanation: CO2 infrared lasers can be used to produce and pattern three-dimensional graphene films, using commercial polymer films. The resulting graphene shows high electrical conductivity. Roll to roll manufacturing method is possible using lasers.
5. Select from the following the first metal substrate on which CVD growth of large area graphene was conducted.
a) Copper
b) Palladium
c) Nickel
d) Potassium
View Answer
Explanation: The deposition of high quality graphene onto various transition metal substrates is done using the CVD process. These metals include Nickel, Palladium, Copper etc. Studies reveal that nickel was the first among metals to be used as a substrate on which CVD growth of large area graphene was conducted.
6. Which of the following is the correct sequence in Hummer’s method of graphene production?
a) Ultrasonication to obtain monolayer GO ➜ Oxidation of graphite to graphite oxide ➜ Filtration of solution ➜ Use of aprotic solvents along with organic compounds ➜ Drying and grinding of products ➜ Addition of hydrazine
b) Addition of hydrazine ➜ Oxidation of graphite to graphite oxide ➜ Ultrasonication to obtain monolayer GO ➜ Use of aprotic solvents along with organic compounds ➜ Filtration of solution ➜ Drying and grinding of products
c) Oxidation of graphite to graphite oxide ➜ Ultrasonication to obtain monolayer GO ➜ Addition of hydrazine ➜ Drying and grinding of products ➜ Filtration of solution ➜ Use of aprotic solvents along with organic compounds
d) Oxidation of graphite to graphite oxide ➜ Ultrasonication to obtain monolayer GO ➜ Addition of hydrazine ➜ Use of aprotic solvents along with organic compounds ➜ Filtration of solution ➜ Drying and grinding of products
View Answer
Explanation: Hummer’s method has three fundamental steps- oxidation, reduction and post-treatment. During oxidation, graphite is oxidized to GO using KMnO4. Ultrasonication is done to obtain monolayer GO. Next in reduction, hydrazine is used to reduce GO to graphene, while aprotic solvents enhance the exfoliation in GO solution. Finally post-treatment method involves the filtration of the solution, and the drying and grinding of the products.
7. Which method of graphene production directly synthesizes graphene in one step, reducing the reaction time from days to few seconds?
a) Spin coating
b) Unzipping method
c) Ion implanation
d) Microwave assisted oxidation
View Answer
Explanation: Microwave assisted oxidation process uses microwave energy to directly synthesize graphene in a single step. The microwave radiation assistance can be used to synthesize graphene oxide with or without holes by controlling the microwave time. This method effectively shortens the reaction time from days to seconds.
8. Which of these is not a quality of the graphene obtained using CVD?
a) High quality
b) Defect free
c) Hard
d) Impervious
View Answer
Explanation: CVD method for graphene synthesis produces graphene of high purity, high quality, great hardness and high impermeability. Though CVD produces such good quality graphene, it forms a large number of defects in the lattice.
9. Which of the following gases is not used in the arc discharge method of graphene production?
a) Hydrogen
b) Helium
c) Ammonia
d) Iodine
View Answer
Explanation: Graphene can be produced by multiple methods. One among them is the arc discharge method. It is carried out in the presence of hydrogen (H2) atmosphere, producing two or three graphene layers. Helium (He) is also used predominantly to form different number of graphene sheets. Apart from that ammonia (NH3) atmosphere is also applied for graphene production.
10. What was the very first method used to obtain graphene?
a) Mechanical exfoliation
b) Hummer’s method
c) Chemical vapour deposition
d) Arc discharge of graphite
View Answer
Explanation: Graphene was first obtained as small flakes of the order of several microns through mechanical exfoliation of graphite using scotch tape. This method is simple, safe and can easily form few layer graphene (FLG). But it requires high expertise in peeling off the tape with thick shiny layers of graphite attached to it.
Sanfoundry Global Education & Learning Series – Nanotechnology.
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