Mandeep Singh – PhD thesis summary

Synthesis and characterization of magnetic nanoparticles for applications in chemical robots

In the present thesis, we had exploited the utilization of various nanoparticles for the hyperthermia and water treatment applications. For the synthesis of magnetic nanoparticles, we followed a chemical coprecipitation approach. Further, in order to obtain aqueous and non-aqueous ferrofluids (FF’s), we coat the magnetic nanoparticles with various ionic and steric stabilizers, respectively.

Various characterization techniques were being used in order to get the knowledge about their surface morphology and magnetic properties, before apply them for above noted applications. For the surface morphology, we used Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier Transform Infrared spectrometry (FT-IR), Thermogravimetric analysis (TGA) etc. From the TEM measurements, we get knowledge about the mean size (number-weighted) and the shape of the nanoparticles. From the XRD measurements, we obtain the average grain size of the nanoparticles plus purity of the powder. Since the magnetite and maghemite phase shifts are quite identical, it is difficult to identify the exact phase of the iron oxide nanoparticles alone from XRD measurements. For this we used FT-IR measurements, which not only give us the phase identification knowledge but also regarding the chemical bonding information between the nanoparticles and the surfactants. From the TGA measurements, we calculated the percentage of the surfactant coating onto the nanoparticle surface. For magnetic characterization we used Superconducting Quantum Interference Device (SQUID). For the hyperthermia applications, we set-up a heating experimental apparatus in our Lab and conducted the experiments. The net rise in temperature w.r.t time was noted for different concentration of samples in their respective mediums and SAR is evaluated by linear regression from the slope of a plot of (ΔT/Δt) against concentration. We had also calculated the time relaxations (Neel and Brownian), in order to know about their contributions towards final SAR.

Besides co-precipitation, we had also obtained maghemite nanoparticles using a novel non-solvent based method – “the Vapour phase approach” and air stable core shell (Fe0/Fe3O4) nanopowder using vacuum freeze drying technique from the NZVI slurry. A detailed surface morphology, magnetic characterization was done and their heating properties were being noted for the hyperthermia applications.

Lastly, we utilized various nanoadsorbents for water treatment applications, especially towards arsenic removal from aqueous medium. For this we synthesize various nanoadsorbents like α-MnO2 (nanorods), δ-MnO2 (nano-clumps) and γ-Fe2O3 (nanoparticles) respectively. However, due to small size, there is difficulty in the separation process after the water treatment. To remove this drawback, we choose two low cost adsorbents- Laterite and Perlite and synthesize various microcomposites. The adsorbents surface morphology is being characterized using various techniques like TEM, SEM, XRD, PSD etc. and their physical properties were being noted. Further, the performance for As(V) removal from aqueous media by these various adsorbents were investigated by batch adsorption experiments.