Ccd image system

The surfactant aqueous solutions were sonicated for 30 min and allowed to settle in a dark container (to prevent possible degradation) for 2 h. TEM samples were prepared by pipetting one drop of the surfactant aqueous solution onto a formva-coated copper TEM grid with carbon film. The samples were stained by 2 % aqueous phosphotungstic acid for negative staining. TEM was conducted on a Tecnai C12 Ultra Twin TEM instrument operated at 120 kV and images were collected using a Gatan CCD image system with digital micrograph software program.

Transmission electron microscopy (TEM) samples were prepared by pipetting a 10 μL drop of as-synthesized NPs at a concentration of 0.125 mg/mL onto a copper TEM grid with lacey carbon film. TEM was conducted on a FEI T12 microscope operated at 120 kV, equipped with a Gatan CCD image system with digital micrograph software program. Powder X-ray diffraction (PXRD) patterns were collected on as-synthesized Fe₃O₄ NPs deposited on a glass substrate using a Bruker D8 Advance using Cu Kα radiation (λ= 1.5418 Å), with the background from the glass substrate subtracted. Transmission Fourier transform infrared (FTIR) spectroscopy measurements were recorded on a Bruker Equinox 55 FT-IR spectrometer in the range of 4000 cm⁻¹ to 400 cm⁻¹ at 2 cm⁻¹ resolution on NPs in a potassium bromide (KBr) pellet, at a sample mass loading of 0.33 wt.%. Thermogravimetric analysis (TGA) was carried out using a TA Instruments Q500 thermal analysis system under a N₂ atmosphere and at a constant heating rate of 10 °C/min from 100 °C to 600 °C. All samples were first heated to 100 °C and held at that temperature for 3 min to remove adsorbed water. Dynamic light scattering (DLS) and zeta-potential (ζ-potential) measurements was carried out using a Malvern Zetasizer Nano and three independent measurements were made for each sample.