- 2.703 g FeCl3 6H2O
- 0.999 g FeCl2 4H2O
- 40 ml H2O
- 25 ml NH4OH 2M (6.63 ml conc.)
The iron salts were added to an Erlenmeyer flask with water to create a solution. This was stirred at 800 RPM.
1:30 – start of the addition of NH4OH.
2:15 – end of addition of NH4OH.
Heating at 90°C was started.
3:00. Heating and agitation were stopped and the sample was washed twice with water, precipitating the nanoparticles with an external magnetic field. 50 ml of sodium citrate 10mM were added.
The sample was ultra-sonicated for 2:30 min at 65% amp with a probe.
The solution was washed with water to remove any excess of sodium citrate and the size was measured by Dynamic Light Scattering (DLS). The biggest peak was found between 69-70nm. The sample was dried under vacuum overnight.
03/07/2014
Once dried, the sample was ground with a mortar and then coated with TEOS.
Coating – 50 ml of absolute EtOH and 10 ml water were mixed with 500 mg of Fe3O4 nanoparticles and were ultra-sonicated at 70% amplitude using a sonic probe.
100 μl of TEOS were dissolved in 10 ml of absolute ethanol. After, this solution was added dropwise to the nanoparticles, stirring at 750 RPM.
The addition of TEOS lasted 20 min and the nanoparticles were left stirring overnight.
04/07/2014
The same procedure was followed, changing the amount of NH4OH for 10 ml 5M and adding this amount dropwise over 15 min. Afterwards, the addition of sodium citrate was repeated. (MB2)
15 ml of the ferro-fluid were diluted in 30 ml of ethanol for coating with 150 and 100 μl of TEOS each. (SBS_1 and SB2_2). Each volume of TEOS was diluted in 10 mL EtOH and added dropwise under intense magnetic stirring.
07/07/2014
The same procedure was followed a third time for the coating with TEOS. This time 75 μl were used and left 3 hours in constant stirring (SB2_3).
Functionalization with APTS.
15 ml of the magnetic fluid were washed with isopropanol (20 ml) and diluted in toluene with 100 μl APTS. (NB2)
The average refractive index was calculated as follows:
Fe3O4, n = 2.42
SiO2, n = 1.46
2.42 + 1.46 = 3.15
08/07/2014
Samples SB2_1, SB2_2 and SB2_3 were washed with water three times and were sonicated with a sonic probe for 1 minute at 60% amplitude.
Once again, it was observed how the solid was easily dispersed in water, forming a fake solution. Spinels were observed in the presence of a magnetic field with samples NB2 and SB2_(1-3).
09/07/2014
The nanoparticles were characterized by DLS. For MB2, it was observed a peak at 39 nm, once coated with TEOS, the peak was moved toward 60 and 80 nm.
For different amounts of TEOS, same results were achieved. (50, 75 and 100 μl).
10/07/2014
The samples SB2_(1-3) were evaporated until the amount of water was minimum. The last residual water was removed with absolute EtOH for the correct functionalization with APTS.
15 ml of absolute ethanol were added to the sample SB2 in intense agitation. Finally, 75 μl of APTS were added and left in constant stirring overnight.
11/07/2014
The samples were once again washed with water, these samples easily precipitated in water, contrary to previous samples. Code names for these samples were NB2_(1-3)
To help the precipitation, a little amount of acetone was added, this was also done for sample SB2’s aliquots.
The samples were magnetically decanted and dried under vacuum for 4 hours.
15/07/14
Samples were taken of pure magnetite, silanized magnetite (NB2) and magnetite coated with silica and silane (SB2_1 and SB2_3) for its characterization in IR for solids.
Comparing the spectra given by the IR of the pure magnetite and silanized magnetite (SB2 and NB2) we were able to distinguish a peak at 990.2 cm
-1 corresponding to a Si-O bond, confirming the correct silanization of the magnetite, although the amino group couldn’t be identified.
Similar results were achieved for samples SB2_1 and SB2_3, however, this peak was not decisive to know if the sample was correctly functionalized giving the fact that the samples are coated with silica.
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