Synthesis and Characterization of Magnetic Nanoparticles Fe3O4, Co3O4 and Their Application in Urea Biosensing

The present research work shows the fabrication of potentiometric urea Biosensor based on magnetic nanoparticles iron oxide (Fe3O4) and cobalt oxide (Co3O4) through simple, economical and reproducible approach. Co-precipitation method has been adopted for synthesis of nanoparticles of Fe3O4 and Co3O4. Scanning electron microscope (SEM), X-rays powder diffraction (XRD) and Raman spectroscopic characterization tools have been utilized to look through the morphology, compositional purity, crystallinity and emission characteristics of the fabricated magnetic nanoparticles. The study of magnetic measurement of Fe3O4 and Co3O4 nanoparticles was carried out in order to confirm their ferromagnetic behaviour, which could be attributed to the uncompensated surface spins and/or finite size effects. The magnetic study depicts that the ferromagnetic order of the Fe3O4 and Co3O4 nanoparticles is raised with increasing the decomposition temperature. \ud Furthermore, in one set of experiment, the potentiometric urea biosensor was fabricated by drop casting the initially prepared isopropanol and chitosan solution, containing Fe3O4 nanoparticles, on the glass fiber filter (2cm diameter). To extract the voltage signal from the functionalized nanoparticles, a copper wire (thickness ~500 μm) has been utilized. \ud The functionalization of surface of the Fe3O4 nanoparticles is obtained by the electrostatically immobilization of urease onto the nanobiocomposite of the Fe3O4chitosan (CH). Urea biosensor with enhanced sensitivity, specificity, stability and reusability was fabricated. Electrochemical detection procedure has been adopted to measure the potentiometric response over the wide logarithmic concentration range of the 0.1 to 80 mM. Urea biosensor based on Fe3O4 nanoparticles depicts good sensitivity with 42 mV per decade at room temperature. \ud In other set of experiment, a potentiometric urea biosensor has been fabricated through the immobilization of urease enzyme onto Co3O4-CH hybrid nanobiocomposite on glass filter paper and a copper wire (500µm diameter) has been attached with nanoparticles to extract the voltage output signal. The shape, size and dimensions of the Co3O4 magnetic nanoparticles were investigated by scanning electron microscopy (SEM), and diameter of nanoparticles lies in the range between \ud 80-100 nm. The structural quality of the Co3O4 nanoparticles is confirmed from X-ray powder diffraction (XRD) measurements while the Raman spectroscopy has been used to understand the chemical bonding between the different atoms. A physical absorption method has been adopted to immobilize the enzyme on to the surface of Co3O4-CH hybrid nanobiocomposite. The potentiometric sensitivity curve measured over the large concentration range 0.1 - 80 mM of urea electrolyte and it revealed that the fabricated biosensor holds good linear sensing ability with a slope curve of the 45mV / decade. \ud Besides magnetic nanoparticles, non magnetic nanoparticles silver (Ag) was also exploited for the fabrication of urea biosensor. Magnetic nanoparticles of Co3O4 showed better sensitivity response of 45mV per decade in comparison to that of Fe3O4 and Ag nanoparticles sensitivity response of 42 mV per decade. \ud Presented biosensors depict good reusability, selectivity, reproducibility; resistance against interferers along with the nice stable output response of ~12 seconds. Moreover, proposed biosensor was used for determination of urea concentration in urine and blood samples of healthy and sick people. Comparing the results with laboratory data indicates that results were consistent with the laboratory data. \ud Keywords: Cobalt oxide (Co3O4), iron oxide (Fe3O4), magnetic nanoparticles, potentiometry, urea biosensor, chitosan, magnetic studies