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Make your own ferrofluid!

This tutorial is designed with middle and high school teachers and students in mind. It is intended to demonstrate a simple synthesis procedure for obtaining water-based magnetic liquids.

The resulting ferrofluid is comprised of magnetite (iron oxide) nanoparticles with an average diameter of about 10 nanometers.

Where possible, we have tried to list the sources and vendors for basic materials. You may see pictures from a recent implementation of this tutorial here.

Before We Begin

The synthesis procedure outlined in this section can be performed by teams of 2-4 students. 

For all the ferrofluid preparation steps, please remember to wear a lab coat, latex or nitrile gloves, and protective eye wear or goggles.

Make sure to work in a ventilated area. The chemical reactions involving ammonia should be run inside a working fume hood or under an aspirator. You may want to test the effectiveness of the hood or aspirator via a simple perfume test -- it should not be possible to smell the sprayed perfume outside the air suction region!!

Let's Get Started

Here is a list of utensils and containers that you will need during the synthesis process for the water-based magnetic liquid:

  1. A strong permanent magnet
  2. A stirring rod (preferably glass or plastic
  3. Two glass flasks (125 ml and 50 ml). If not available, transparent plastic cups may do.
  4. Several plastic weighing boats. If not available, a clean sheet of paper may do.
  5. Simple pipettes
  6. A liquid waste container (could be a glass beaker or a large jar)
  7. A small spatula. If not available, a simple tea or dessert spoon may do.

Fig. 1. Containers and other materials that will be used during the synthesis of the magnetic liquid.

Below is a list of chemicals and materials that you will need:

  1. Iron(iii)chloride
  2. Iron(ii)chloride
  3. Ammonium hydroxide
  4. Tetramthyleammoniumhydroxide
  5. hydrochloride acid
  6. mineral oil
  7. distilled water

Fig. 2. Chemicals for ferrofluid synthesis.

Procedure Summary

The synthesis procedure outlined below is divided into eight steps. The first two steps are similar; they involve the preparation iron (II) and iron (III) salt solutions. In the third step, we will react these solutions (as shown in the chemical reaction below) to form and precipitate iron oxide (magnetite) as nanoparticles.

2 FeCl3 + FeCl2 + 8 NH3+ 4H2O → Fe3O4 + 8 NH4Cl

We will then eliminate excess chloride ions from the resulting solution, and change the pH to neutral.

The fifth step will modify the surface of the magnetite particles so that they are stabilized in water. In the sixth step, we will adjust the concentration of the ferrofluid so that it spikes with our magnet.

The final step is to prepare the sample for demonstration.

In the next section, we will outline the synthesis steps.