Dispersing carbon nanotubes in water can be either with chemical functionalization or with the use of non-covalent functionalization.

In the first category, you can use an acid treatment like c.HNO3 (heat for 4 h, Carboxylic acid-functionalized, +increased oxygen content, -lower L/D, -less sp2 carbon atoms).

In the second category, you can use surfactants (soap) in order to disperse nanotubes in aqueous dispersions. There are 4 main surfactants that you can use and they are: i) SDS, ii) SDBS, iii) Triton X-100, and in hardcore situations, you can use dishwashing soap!!! Typically you can mix 5g CNTs + 5g Surfactant +1L H2O.

You can use ultrasonication at a high amplitude with longer on time

Hi

I suggest you which use ultrasound for dispersing

Mahsa Amiri

While the only dispersing agent for small material is energy there are some dangers in using prolonged sonication:

• Breakage of the CNT's
• Contamination of the system by the disintegrating ultrasound tip
• Damage by thermal effects - the temperature in a collapsing ultrasound bubble is approximately 5500K! I've seen pictures of welded metal particles under sonication

The stages in making a successful dispersion are wetting, separation, and stabilization. Surfactants are used primarily to wet (hydrophobic, usually) surfaces and, in many instances, almost any can be used in the appropriate concentration (I've used washing up liquid to the chagrin of some university professors but I do like Triton X-100 too as well as non-charged systems such as Nonidet. In food or pharam applications only Tween or Span may be appropriate) unless they're also there to aid the stabilization (charge or steric). Take a look at these webinars (registration required) in this order:

Dispersion and nanotechnology

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat

Ultrasound, cavitation, and the singing kettle

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W130619UltrasoundCavitationSingingKettle.html

While you may use functionalization and the like to improve wetting between water and CNTs, you may also consider employing ultrasonication. Both mentioned routes have a number of advantages and disadvantages; it depends what exactly you are asking for. Here I'd like to explain some about the advantages and disadvantages associated with sonication. Please feel free to ask should you have other questions.

Advantages are:

• high quality dispersion
• inexpensive process
• easy to use
• environmentally friendly approach unlike chemical methods
• higher performance and efficiency
• fast
• higher stability without agglomeration over time

Disadvantages are:

• probability of particle breakage (Try not to use high intensities; lower weight fractions are also recommended; bath sonicators are better than probe sonication tool)
• contaminants caused by sonication probe/tool (Try to finish the job as quickly as possible; longer sonication, higher contamination)
• Thermally induced problems (Try to minimize thermal effects by loweing temperature)

Good luck!