04 Oct

Examples of Nano Materials

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Contents

• Schwarzite
• Graphene
• Carbon Nanotubes

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A) Schwarzite – New Form of Carbon Created

Introduction

Schwarzites is a completely new form of carbon that has been created by scientists recently. It is a negatively curved carbon unlike fullerenes and graphene which have positive or zero curvature respectively.

Creation of Schwarzites

• Scientists, in Japan and South Korea, while investigating  Zeolite-templated carbons (ZTCs) – crystalline form of silicon di-oxide with carbon structure built into them – accidently created schwarzites.
• Later, scientists at University of California demonstrated that it was possible to create ZTC structures by injecting a vapor containing carbon into zeolites.
• Once inside, the carbon assembles into a graphene-like sheet that lines the walls of the pores in the zeolite. In doing so, the surface stretches to minimize the area. As schwarzites are topologically minimal surfaces, they tend to acquire negative curvature. The zeolite is then dissolved to produce pure schwarzites.

 Potential Future Applications

• Super Capacitors:
• Storage of atoms and molecules
• Catalyzing Reactions

 Conclusion: Though the applications of schwarzites remains to be seen, the scientists speculate that their unique electronic, magnetic, and optical properties can make them useful, as super capacitors, battery electrodes and catalysts, and with their large internal spaces ideal for gas storage and separation.

Example Questions

• What is a Schwarzites? Discuss its future potential applications [10 marks, 150 words]

B) Graphene

• It is an allotrope of carbon which is a one-atom thick layer of pure carbon. Carbon atoms are bounded together in a hexagonal honeycomb lattice.

How is it produced

• By separating a single atom layer film from graphite.

Properties: Physical

• 2D – world’s first 2D material
• Graphene is harder than diamond, more elastic than rubber, tougher than steel and yet lighter than aluminum.
• In fact, it is 200 times stronger than steel (100 times stronger than the strongest steel).
• Thickness: 1 million times thinner than a human hair
• Stretchable as well as transparent, flexible, and impermeable.
• It can also act as perfect barrier – not even helium can pass through it

Properties: Thermal, Electrical and Magnetic Properties

• Highest electronic conductivity of any material in the world.
• Best Heat conductivity of any material in the world
• Shows a large and nonlinear diamagnetism

Applications: Graphene’s unique combination of extraordinary properties offer a fascinating material platform for the development of next-generation technologies in many areas.

• Energy Harvesting and Storage: It can be used for better rechargeable batteries; superior capacitors; newer methods of making solar cells Further, proton transfer in graphene shows promise for artificially mimicking photosynthesis.
• Electronics: Very high electron conductivity allows graphene to be used for low-cost printable electronics, high performance transistors; thermal management and heat dissipation in nano-electronic devices.
  • The optical properties of graphene can also be controlled by doping and make it well suited for optoelectronic devices.
• Composites and Coatings: Its low mass and low loading requirements make graphene standout as a reinforcing agent in composites. It can be used for making lubricants with enhanced anti-wearing capabilities; radiation shielding and lighting strike protection; superhydrophobic coating; transparent, flexible and conductive thin films
• Membranes – It can improve the quality of filters used in desalination or other water purifying instruments. Graphene oxide is used for the purpose.
  • It can also act as gas barrier for e.g. in food packaging.
  • It can be used for separation of organic solvent with water.
• Biomedical Technologies: Very high surface area, electron mobility is paving the way for novel biomedical technologies. Graphene bioelectronics (transistors and electrode arrays) has become a ground-breaking field that offers existing opportunities for developing new kinds of biosensors. Key applications include Thermal ablation of highly resistant cancer cells; Bioelectronics (bionics); Electronic interface to living cells and nerve tissues; etc.
• Sensors: Since every atom of graphene is exposed it is an ideal material for biological, gas and chemical sensors. It can be used for explosive detection; detecting biomarkers for parkinson’s disease; selective gas sensing; self-healable, multifunctional electronic sensor tattoos; environment monitoring
• Wearable technologies
• Light weight cars, planes etc.
• Health Risks: Extensively debated.
• Toxicity depends on several factors such as shape, size, purity, post-production processing steps, oxidative state etc.

C)  Carbon Nanotubes (CNT)

Intro

• Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of material science and technology. 

Properties

• Strength: One of the most tensile and elastic material discovered yet.
• Wettability
• Exhibits a super hydrophobic
• By applying a low voltage as low as 1.3 V, the extreme water repellants surface can be switched into super hydrophilic.

Electrical Properties

• CNT are either metallic or semiconducting along the tubular axis.

Thermal Properties

• All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as “ballistic conduction”, but good insulators lateral to the tube axis.

Application

• Current uses and application of nanotubes has mostly been limited to the use of bulk nanotubes, which is a mass of rather unorganized fragments of nanotubes.
  • Used as composite fibers in polymers to improve the mechanical, thermal and electrical properties of the bulk product.
  • Tips for atomic force microscope probes
  • In tissue engineering, carbon nanotubes can act as scaffolding for bone growth.

Concerns: Toxicity, health risk not clear yet.

• • Smart materials able to adapt to their environment, small sensors that can be controlled remotely, and drugs that are activated on command
  • Efficient energy storage devices