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MHT-CET Chemistry · Green Chemistry and Nanochemistry

Nanochemistry: Dimensions, Sol–Gel Synthesis and Characterisation

A nanomaterial has at least one dimension between 1 and 100 nm; it is classed by how many of its dimensions lie OUTSIDE that range, made by the sol–gel route, and identified with UV-visible, FTIR, XRD, SEM and TEM.

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Why this matters

14 PYQs, mostly EASY. Seven classify a nanostructure by dimension or place something on the size scale, six ask which technique or step does what, and one asks about silver nanoparticles. Two cards.

Concept 1 of 2: Classifying Nanostructures by Dimension

Count the dimensions that are NOT nanoscale. A quantum dot is small every way, so it is zero-dimensional. A wire is long in one direction — one-dimensional. A film is wide in two — two-dimensional.

Definition

  • 0-D: nanoparticles, quantum dots, nano-rings, microcapsules.
  • 1-D: nanowires, nanotubes, nanorods, fibres.
  • 2-D: thin films, layers, coatings.
  • Size scale: water, glucose (molecules) < virus < bacteria (largest of these).
  • Use: silver nanoparticles kill E. coli in water purification.
DimensionExamples
0-DQuantum dots, nanoparticles, nano-ringsQ
1-DNanowires, nanotubes, nanorodsQ
2-DThin films, coatingsQ
Largest of water, glucose, virus, bacteriaBacteriaQ
Removes E. coli from waterSilver nanoparticlesQ
Practice this conceptself-check · 2 quick reps

The same idea in a real exam question:

MHT-CET · 2023 · 11th May Shift 2 · Q56Moderate

Example 1 · Green Chemistry and Nanochemistry · Nanochemistry, Nanostructures, Classification and Synthesis

Which among the following is an example of one-dimensional nanostructure?

Nano-rings as one-dimensional

A ring looks like a bent wire, but the textbook lists nano-rings with quantum dots as zero-dimensional.
Drill 7 more on classifying nanostructures by dimension

Concept 2 of 2: Sol–Gel Synthesis and the Characterisation Techniques

Sol–gel builds an oxide network from a solution: hydrolyse the precursor, let it condense into a gel, age it, dry it, and finally dehydrate it. Then each instrument answers one question — UV-visible is the quick first check, FTIR the bonding, XRD the crystal structure, SEM the surface, TEM the size.

Definition

  • Sol–gel: hydrolysis → polycondensation (oxide or alcohol-bridged network) → aging of the gel → drying → dehydration (last step).
  • UV-visible spectroscopy: preliminary confirmation of nanoparticles.
  • FTIR: absorption by functional groups — the binding nature.
  • XRD: crystal structure and phase. SEM: morphology. TEM: particle size.
QuestionAnswer
Order of the sol–gel reactionsHydrolysis, then polycondensationQ
Last step of wet chemical synthesisDehydrationQ
Preliminary confirmationUV-visible spectroscopyQ
Information from FTIRFunctional-group absorptionQ
Binding natureFTIRQ
Particle sizeTEMQ
Practice this conceptself-check

The same idea in a real exam question:

MHT-CET · 2024 · 10th May Shift 2 · Q64Moderate

Example 2 · Green Chemistry and Nanochemistry · Nanochemistry, Nanostructures, Classification and Synthesis

Identify the last step in wet chemical synthesis of nanomaterial.

Drying as the last step

Drying of the gel comes before the final dehydration, which is the last step the paper asks for.
Drill 5 more on sol–gel synthesis and the characterisation techniques

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Reference tables (2)

Classifying Nanostructures by Dimension5 rows
DimensionExamples
0-DQuantum dots, nanoparticles, nano-ringsQ
1-DNanowires, nanotubes, nanorodsQ
2-DThin films, coatingsQ
Largest of water, glucose, virus, bacteriaBacteriaQ
Removes E. coli from waterSilver nanoparticlesQ
Sol–Gel Synthesis and the Characterisation Techniques6 rows
QuestionAnswer
Order of the sol–gel reactionsHydrolysis, then polycondensationQ
Last step of wet chemical synthesisDehydrationQ
Preliminary confirmationUV-visible spectroscopyQ
Information from FTIRFunctional-group absorptionQ
Binding natureFTIRQ
Particle sizeTEMQ

Watch out for (2)

Test yourself on Green Chemistry and Nanochemistry

15 past MHT-CET questions from this chapter, timed at 14 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Take the Green Chemistry and Nanochemistry chapter testDrill all 14 questions