"Preparation of iron oxide nanoparticles (NPs)"

 

Preparation of iron oxide nanoparticles (NPs)

Theory:

The co-precipitation method involves the precipitation of iron hydroxide from iron salts in the presence of a base. In this case, the FeCl₃ and FeSO₄ salts are used to provide Fe⁺² ions for the reaction. By gradually adding NH₄OH as the base, the pH of the solution increases, leading to the formation of iron hydroxide. The iron hydroxide precipitate can then be further processed to obtain iron oxide nanoparticles.

Chemicals Required:

• Iron (III) chloride (FeCl₃) solution, 0.2 M
• Iron (II) sulfate (FeSO₄) solution, 0.1 M
• Ammonium hydroxide (NH₄OH) solution
• Solvent: Water or appropriate organic solvent

Materials Required:

1. Reaction vessel or flask
2. Magnetic stirrer or mechanical stirrer
3. pH meter
4. Centrifuge
5. Drying equipment (e.g., vacuum oven or desiccator)

Chemical Equation:

Procedure:

• Prepare a reaction vessel and add the FeCl₃ solution (50 ml, 0.2 M) and the FeSO₄ solution (50 ml, 0.1 M) to it.
• Start stirring the mixture using a magnetic or mechanical stirrer for 15 minutes to ensure proper mixing.
• Gradually add NH₄OH dropwise to the reaction mixture while monitoring the pH using a pH meter.
• Continue stirring the mixture for an additional 20 minutes or until the pH reaches 11. The pH adjustment to 11 promotes the formation of iron hydroxide precipitates.
• Once the reaction time is complete, stop the stirring and allow the precipitate to settle.
• Separate the precipitate from the solution using a centrifuge. Discard the supernatant.
• Wash the obtained precipitate several times with water or a suitable solvent to remove any impurities or unreacted reagents.
• Dry the washed precipitate using a vacuum oven or desiccator to remove any residual moisture.
• The resulting dried material will likely consist of iron oxide nanoparticles, which can be characterized using various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), or Fourier-transform infrared spectroscopy (FTIR).

Alternating method for synthesis of Iron Oxide Nanoparticles by using ammonia:

Theory:

Iron oxide nanoparticles are commonly synthesized through a precipitation method using iron chloride and iron sulfate solutions. The addition of ammonia helps in the formation of iron hydroxide, which is subsequently transformed into iron oxide nanoparticles through heat treatment or aging.

Formation of iron hydroxide:

FeCl₂ + 2NaOH → Fe(OH)₂ + 2NaCl

FeSO₄ + 2NaOH → Fe(OH)₂ + Na₂SO₄

Conversion of iron hydroxide to iron oxide:

2Fe(OH) ₂ → Fe₂O₃ + 2H₂O

Overall reaction:

2FeCl₂ + 4NaOH → Fe₂O₃ + 4NaCl + 2H₂O

2FeSO₄ + 4NaOH → Fe₂O₃ + 2Na₂SO₄  + 2H₂O

Procedure:

1. Prepare a 0.2 M solution of iron chloride (FeCl₂) by dissolving the appropriate amount of iron chloride in 50 ml of distilled water.
2. Prepare a 0.1 M solution of iron sulfate (FeSO₄) by dissolving the appropriate amount of iron sulfate in 50 ml of distilled water.
3. Mix both solutions (0.2 M FeCl₂ and 0.1 M FeSO₄) in a glass beaker.
4. Stir the mixture for approximately 15 minutes to ensure thorough mixing. Apparatus required: Magnetic stirrer, stir bar.
5. Add 40 ml of ammonia (NH₃) to the mixture while continuing to stir.
6. Continue stirring the mixture until the formation of iron oxide nanoparticles.

Note:

The stirring time required for nanoparticle formation may vary depending on the desired size and properties of the nanoparticles. Further heat treatment or aging may be necessary to complete the transformation.

Calculations:

Molar mass of FeCl₃ = 55.845 g/mol + 106.359 g/mol = 162.204 g/mol

To prepare a 0.2 M solution of FeCl₃ in 50 ml water:

Molarity (M) = moles of solute / volume of solution (L)

0.2 M = moles of FeCl₃ / 0.05 L (50 ml = 0.05 L)

Moles of FeCl₃ = 0.2 M x 0.05 L = 0.01 moles

Mass of FeCl₃ = Moles of FeCl₃ x Molar mass of FeCl₃

Mass of FeCl₃ = 0.01 moles x 162.204 g/mol

Therefore, the mass of FeCl₃ required is 1.62204 grams.

Similarly, for FeSO₄:

Molar mass of FeSO₄ = 55.845 g/mol + 32.06 g/mol + 63.996 g/mol = 151.901 g/mol

To prepare a 0.1 M solution of FeSO₄ in 50 ml water:

Molarity (M) = moles of solute / volume of solution (L)

0.1 M = moles of FeSO₄ / 0.05 L (50 ml = 0.05 L)

Moles of FeSO₄ = 0.1 M x 0.05 L = 0.005 moles

Safety Precautions:

• Wear appropriate personal protective equipment, such as gloves and safety goggles, when handling chemicals.
• Work in a well-ventilated area or under a fume hood to avoid inhalation of fumes.
• Handle ammonia with care, as it is a corrosive substance. Avoid direct contact with skin and eyes.
• Follow proper waste disposal protocols for chemicals used in the synthesis.