With reference to carbon nanotubes, consider the following statements : 1. They can be used as carriers of drugs and antigens in the human body. 2. They can be made into artificial blood capillaries for an injured part of human body. 3. They can be used in biochemical sensors. 4. Carbon nanotubes are biodegradable. Which of the statements given above are correct ?

Mentions fullerenes (C60) as a class of carbon allotropes related to other carbon nanostructures; shows carbon can form distinct cage/novel structures.

A student could note that nanotubes are another carbon allotrope similar to fullerenes and therefore may share properties (size, hollow structure) that make them candidates for carrying molecules.

Describes graphene aerogel, a novel porous carbon material with high absorbance and use in environmental cleanup — an example of engineered carbon materials used to take up/hold substances.

One could infer that engineered carbon materials can adsorb and carry other substances and thus hypothesize nanotubes might carry drugs/antigens by adsorption or encapsulation.

Explains that functional groups on carbon chains determine properties regardless of chain length — shows that adding functional groups to carbon frameworks changes interactions.

A student can extend this to the idea that functionalising carbon nanotubes (attaching groups) could tailor their solubility/biocompatibility and drug-binding — key for carrier design.

Highlights carbon's tetravalency and catenation leading to many carbon compounds and bonds with elements like oxygen, nitrogen, etc.

This suggests carbon nanostructures can form covalent or noncovalent interactions with biological molecules or functional groups, implying routes to attach drugs/antigens.

Describes blood as a transport medium that carries dissolved substances throughout the body.

Using the basic fact that the bloodstream transports carried agents, a student could combine this with nanotube carrier potential to assess delivery feasibility and need for biocompatibility/size considerations.

Describes carbon allotropes (graphite, diamond, fullerenes) showing that carbon forms diverse structures with very different physical properties.

A student could note that carbon nanotubes are another carbon allotrope and infer that diverse physical properties of allotropes make them candidates for specialized uses like sensing.

Gives an example of a carbon nanomaterial (graphene aerogel) with very high porosity and absorbing capacity and mentions uses in devices and coatings.

From graphene aerogel's high surface area and device applications, a student could extrapolate that similar carbon nanostructures (e.g., nanotubes) might provide high surface area and adsorption useful for biosensors.

Notes that graphite (a carbon form) is a very good conductor of electricity, unlike most non-metals.

Since electrical conductivity is often exploited in electronic biosensors, a student could infer conductive carbon nanostructures might be useful transducers in biosensing.

Explains that the presence of functional groups determines properties of carbon compounds (pattern: functionalisation changes behaviour).

A student could infer that attaching functional groups to carbon nanostructures could let them bind biomolecules specifically — a key requirement for biosensors.

Emphasises tetravalency and catenation producing many carbon compounds and the role of non-carbon groups in determining properties.

A student could combine this with knowledge of biomolecule chemistry to reason that carbon frameworks can be chemically modified to interact with biological targets in sensors.

Gives the working definition of 'biodegradable' vs 'non-biodegradable' (broken down by biological processes vs persistent/inert).

A student could apply this definition to CNTs by asking whether biological agents (microbes, enzymes) can chemically break CNTs into simpler compounds under physiological conditions.

States that bioremediation is limited to compounds that are biodegradable and that not all compounds are susceptible to rapid/complete biological degradation.

Use this rule to frame experiments or literature searches: check whether CNTs fall into the 'not susceptible' category by seeking evidence of microbial or enzymatic degradation rates.

Gives examples of non-biodegradable pollutants (plastics, glass) indicating that many man-made carbon-containing materials resist microbial decomposition.

Compare CNTs (a synthetic carbon nanomaterial) with listed non-biodegradable materials to hypothesize persistence and then look for data on CNT persistence or similarity in chemical stability.

Explains environmental consequence of non-biodegradables (persistence and bioaccumulation up the food chain).

If CNTs are persistent, one would predict potential accumulation in organisms; a student could therefore seek studies measuring CNT persistence, tissue accumulation, or trophic transfer.

Describes biological weathering and how biological processes (acids, organism activity) can enhance decay of materials.

Use this as a guide to test whether known biological weathering agents (acidic conditions, enzymes, phagocytic cells) can degrade CNTs under body-like conditions.