Fe₃S₄ NPs 

Synthesis Procedure:

1. Preparation of Precursor Solution:

   • Dissolve 1.09 g of FeCl₃·6H₂O and 0.609 g of SC(NH₂)₂ in a beaker containing 80 mL of ethylene glycol (for pure Fe₃S₄ phase, Greigite).

   • (If a mixed phase of Fe₃S₄ and FeS₂ is desired, use 60 mL ethylene glycol and 20 mL distilled water instead.)

   • Place the beaker on a magnetic stirrer and stir the solution until complete dissolution is achieved (Yellowish hazel color).

2. Hydrothermal Reaction:

   • Transfer the well-mixed solution into a Teflon-lined stainless-steel autoclave.

   • Seal the autoclave and place it inside an electric oven preheated to 180°C.

   • Maintain the reaction for 12 hours until a black powder forms, indicating Fe₃S₄ formation.

3. Cooling and Washing Process:

   • Allow the autoclave to cool naturally to room temperature before opening.

   • Collect the black precipitate and wash it twice with distilled water and once with ethanol.

   • Use centrifuge tubes to hold the sample and place them in a centrifuge set at 8000 rpm for 8 minutes (optional; for low rpm use more time) to separate impurities.

   • Transfer the residue into a beaker and use a mixer to evenly mix the fluids and sample.

4. Drying the Fe₃S₄ NPs:

   • Place the washed precipitate inside a vacuum oven and dry it overnight to obtain pure undoped Fe₃S₄ nanoparticles.