1. What are nanomaterials?
Nanomaterials are materials with at least one dimension below 100 nanometers. At this scale, the surface-area-to-volume ratio is enormous and quantum effects emerge, giving the material superior conductivity, strength, catalytic activity and optical properties compared with conventional materials.
2. Common nanomaterials
Graphene oxide (GO)
A one-atom-thick carbon layer decorated with oxygen groups, easily dispersed in water. Uses: conductive films, sensors, composites, water filtration, battery electrodes.
Carbon nanotubes (CNT)
Rolled carbon tubes with extremely high tensile strength and good electrical/thermal conductivity. Uses: ultralight composites, conductive inks, transistors, heat dissipation, electrodes.
Gold nanoparticles (AuNP)
Nano-sized gold particles with unique optical properties (plasmon resonance). Uses: biosensors, medical diagnostics, catalysis, imaging.
TiO₂ nanopowder
Nano titanium dioxide with strong photocatalytic activity. Uses: self-cleaning surfaces, water treatment, DSSC solar cells, UV protection.
3. Dispersion — the hardest part of working with nanomaterials
Nanomaterials rarely fail because the material itself is poor. They fail because of agglomeration. At nanometre scale the surface-area-to-volume ratio is enormous, so van der Waals forces between particles are strong enough to pull them together. Agglomerated graphene oxide no longer behaves like graphene — it is just carbon powder.
- Match the solvent. Graphene oxide disperses well in water thanks to oxygen-containing surface groups. Reduced graphene oxide (rGO) is hydrophobic and needs NMP, DMF or a surfactant.
- Sonicate with restraint. Sonication breaks up agglomerates, but too long or too intense will snap carbon nanotubes and cut graphene sheets. Repeated gentle bath sonication usually beats one high-power probe run.
- Check stability, not just dispersion. Getting a suspension is not the same as keeping it. Measure zeta potential: magnitudes above roughly 30 mV indicate electrostatic stabilisation.
- Buy pre-dispersed where possible. For graphene oxide, buying a ready dispersion saves considerable effort over dispersing dry powder yourself.
4. Characterisation: verifying you received what you ordered
Nanomaterials are the most easily misrepresented items in a laboratory, because the eye cannot tell them apart. All black powders look alike. These are the minimum measurements worth running before committing material to a main experiment:
| Technique | What it tells you |
|---|---|
| Raman spectroscopy | The D/G intensity ratio reflects defect density in graphene and CNTs; the 2D peak shape indicates layer count |
| SEM / TEM | Real morphology: particle size, tube length, degree of agglomeration |
| XRD | Crystalline phase — for TiO₂, the anatase/rutile ratio that governs photocatalytic activity |
| BET | Specific surface area, key for adsorption and catalysis |
| DLS | Size distribution in suspension — catches agglomeration that dry-powder SEM misses |
| UV-Vis | For gold nanoparticles, the surface plasmon resonance peak position confirms particle diameter |
5. Safety when handling nanomaterials
Dry nanoparticles can become airborne and penetrate deeper into the respiratory tract than ordinary dust. Long-fibre carbon nanotubes deserve particular care because of their asbestos-like aspect ratio, and their long-term respiratory toxicity is still under study.
- Weigh and handle dry nanopowders in a fume hood or safety cabinet, never on an open bench.
- Prefer suspensions over dry powder where the application allows — liquids largely remove the inhalation risk.
- Wear nitrile gloves, a lab coat and a certified particulate respirator when handling powders.
- Clean with damp wipes rather than dry sweeping or compressed air — blowing re-suspends the dust.
- Collect nanomaterial waste separately; do not pour it down the sink.
Frequently asked questions
How do graphene oxide and graphene differ?
Graphene is a single sheet of pure carbon and conducts electricity very well. Graphene oxide carries oxygen-containing groups on its surface, which makes it water-dispersible but essentially insulating. Reducing graphene oxide (to rGO) recovers some conductivity but never reaches pristine graphene.
What makes TiO₂ P25 special?
P25 is a mixed-phase material, roughly 3:1 anatase to rutile. The junction between the two phases separates electron–hole pairs more effectively than either phase alone, giving P25 high photocatalytic activity and making it the standard benchmark in most photocatalysis publications.
How should nanomaterials be stored?
Keep dry powders sealed and dry, since moisture promotes agglomeration. Store suspensions cool and dark and mix before use; gold nanoparticle suspensions are especially salt-sensitive, so do not dilute them with high-ionic-strength solutions. Record the date of opening — the large surface area means nanomaterials adsorb contaminants from air over time.
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