Tuning of electronic and magnetic properties of multifunctional r-GO-ATA-Fe2O3-composites for magnetic resonance imaging (MRI) contrast agent

Abstract

We have synthesized r-GO-ATA-Fe2O3 nanocomposites and studied their microstructural and electromagnetic properties for future possible magnetic resonance imaging for biomedical application. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption near edge spectroscopy were used to study the structural and electronic properties, while a superconducting quantum interface device magnetometer was used for investigating the magnetic behavior of the nanocomposites. The nanocomposites have been found to reduce the graphitic structure of GO due to the substitution of carbon/oxygen and/or iron nanoparticles. Conversely, the electrical conductivity of nanocomposites is found to be high due to the formation of Fe—C/Fe—O bonds in the structure of the nanocomposites. The composites also exhibit superparamagnetic features as observed from the M-H hysteresis loop with saturation magnetization of ≈0.1 emu/g at 1.8 K temperature. The results, in general, suggest possible applicability of r-GO/Fe2O3 nanocomposites as an effective multifunctional platform for magnetic resonance imaging in biomedical applications.

Polyacrylate grafted graphene oxide nanocomposites for biomedical applications

“…Similarly, as compared to GO, the r-GO, all the other features in the π* region were downshifted by ~0.4 -0.5 eV and such shift has been observed in our previous work as well. 37 Particularly, the downshift and reduction in the intensity of the previously observed (for GO) mixed hydroxylated (C-OH) and ether-linked carbon species (C-O-C) at 287.8 eV indicates clearly that the hydroxylated species are removed during the reduction process by hydrazine hydrate, leading to the alteration of the electronic structure of the r-GO. 34,38 Now, due to the presence of electronegative oxygen, the hydroxyl groups bonded to the carbonyl carbon see an upshift in their π* position.…”

“…However, P-rGO current response is nearly ~10 2 higher than that of GO, albeit still lower than the r-GO, which can be attributed to the lower amount of oxygen functional groups. 37 The corresponding log I-V curves for the GO/r-GO/P-rGO are shown in Fig. 4(b, d, f) in which the GO shows a symmetric log I-V curve which have a small hysteresis loop on the positive voltage side and ranges between 0 V to 0.5 V, while the P-rGO displayed a small hysteresis loop on the positive voltage side in the range 0.25-0.75 V. The hysteresis effects usually arise from deeply trapped charges due to the presence of defects in the P-GO as the escape time for the trapped charges is longer than the time it takes to make the semi-log sweep.…”

“…43 The observed changes in the electrical properties are further supported by the surface sensitive UPS He-I (hν = 21.22 eV) measurements as the high photon flux source is only able to excite the valence band electrons and thus has been used to probe the position of the Fermi energy (EF) with respect to the vacuum level. 37,44 The UPS He-I spectra consists of two areas of significant interest: the low binding energy region where the valence band maximum (VBM) relative to the EF can be determined and the high binding energy where the electrons are able to overcome the work function () of the material. 44 The  itself is determined by subtracting the width of the spectrum (energy difference between the EF and the high binding energy cut-off) from the He-I excitation energy (21.22 eV).…”

“…The reduction in the () of r-GO to 4.0 eV, as compared to GO ( ~5.0 eV owing to surface dipole moments of oxygen functional groups disrupting the π-conjugation) is understandable in terms of the removal of oxygen functional groups and a consequential increase in the sp 2 content. 37,44 In general, the surface functional groups and the electronic structure of the material are thought to be the most important factors which affect the . 44,47 In the case of P-GO and P-rGO, while the overall oxygen content is increasing and the area under the C K-edge π*-peak (incorporating sp 2 bonds) is reducing (P-rGO (2.05 a.u.…”

Recent Advances of Bioresponsive Nano-Sized Contrast Agents for Ultra-High-Field Magnetic Resonance Imaging

“…Signal intensity of MRI is affected by the relaxation rate of in vivo water protons. By using the contrast agent with varied contents, the MRI signal intensity can be changed, where paramagnetic metal ion in contrast agent with different concentrations will positively alter the relaxation rate of nearby water proton spins (Idisi et al, 2019;Kubíčková et al, 2019). The contrast agent for MRI has been illustrated in Figure 1, where several factors affecting the MRI have been clearly indicated with the listed examples.…”