The quest for developing highly efficient TiO2-based photocatalysts is continuing and, inparticular, evolving a new strategy is an important aspect in this regard. In general, much effort hasbeen devoted to the anatase TiO2 modifications, despite there being only a few recent studies onrutile TiO2 (rTiO2). To the best of our knowledge, studies on the preparation and characterization ofthe photocatalysts based on the intentional inclusion of graphene (G) into rTiO2 nanostructureshave not been reported yet. Herein, we develop a new type of TiO2-based photocatalyst comprisingof G included pure rTiO2 nanowire (abbreviated as rTiO2(G) NW) with enhanced visible lightabsorption capability. To prepare rTiO2(G) NW, the G incorporated titanate electrospun fibers wereobtained by electrospinning and subsequently heat treated at various temperatures (500 to 800 °C).Electrospinning conditions were optimized for producing good quality rTiO2(G) NW. The rTiO2(G)NW and their corresponding samples were characterized by appropriate techniques such as X-raydiffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopyand UV-vis diffuse reflectance spectroscopy to ascertain their material characteristics. XRD resultsshow that the lattice strain occurs upon inclusion of G. We present here the first observation of anapparent bandgap lowering because of the G inclusion into TiO2 NW. While anatase TiO2 NWexhibited poor visible light photocatalysis towards NOx removal, the rTiO2(G) NW photocatalystwitnessed a significantly enhanced (~67%) photocatalytic performance as compared to anataseTiO2(G) NW. We concluded that the inclusion of G into rTiO2 nanostructures enhances the visiblelight photoactivity. A plausible mechanism for photocatalysis is suggested.
We report the detailed microstructural, morphological, optical and photocatalytic studies of graphene (G) and manganese (Mn) co-doped titanium dioxide nanowires (TiO 2 (G-Mn) NWs) prepared through facile combined electrospinning-hydrothermal processes. The as-prepared samples were thoroughly characterized using X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). XRD studies reveal the formation of mixed anatase-rutile phases or rutile phase depending on the dopant (Mn) precursor concentrations in the electrospinning dope and calcination temperature. The evaluation of lattice parameters revealed that the incorporation of Mn species and carbon atoms in to the lattice of anatase or rutile TiO 2 could occur through substituting the sites of oxygen atoms. XPS results confirm the existence of Mn 2+ /Mn 3+ within the TiO 2 NW. Raman spectroscopy provides the evidence for structural modification because of the graphene inclusion in TiO 2 NW. The optical band gap of G-Mn including TiO 2 is much lower than pristine TiO 2 as confirmed through UV-vis DRS. The photocatalytic activities were evaluated by nitric oxide (NOx) degradation tests under visible light irradiation. Superior catalytic activity was witnessed for rutile G-Mn-co-doped TiO 2 NW over their anatase counterparts. The enhanced photocatalytic property was discussed based on the synergistic effects of doped G and Mn atoms and explained by plausible mechanisms.
Magnetic nanoparticles (MNPs) are widely used materials for biomedical applications owing to their intriguing chemical, biological and magnetic properties. The evolution of MNP based biomedical applications (such as hyperthermia treatment and drug delivery) could be advanced using magnetic nanofluids (MNFs) designed with a biocompatible surface coating strategy. This study presents the first report on the drug loading/release capability of MNF formulated with methoxy polyethylene glycol (referred to as PEG) coated MNP in aqueous (phosphate buffer) fluid. We have selected MNPs (NiFe2O4, CoFe2O4 and Fe3O4) coated with PEG for MNF formulation and evaluated the loading/release efficacy of doxorubicin (DOX), an anticancer drug. We have presented in detail the drug loading capacity and the time-dependent cumulative drug release of DOX from PEG-coated MNPs based MNFs. Specifically, we have selected three different MNPs (NiFe2O4, CoFe2O4 and Fe3O4) coated with PEG for the MNFs and compared their variance in the loading/release efficacy of DOX, through experimental results fitting into mathematical models. DOX loading takes the order in the MNFs as CoFe2O4 > NiFe2O4 > Fe3O4. Various drug release models were suggested and evaluated for the individual MNP based NFs. While the non-Fickian diffusion (anomalous) model fits for DOX release from PEG coated CoFe2O4, PEG coated NiFe2O4 NF follows zero-order kinetics with a slow drug release rate of 1.33% of DOX per minute. On the other hand, PEG coated NiFe2O4 follows zero-order DOX release. Besides, several thermophysical properties and magnetic susceptibility of the MNFs of different concentrations have been studied by dispersing the MNPs (NiFe2O4, CoFe2O4 and Fe3O4) in the base fluid at 300 K under ultrasonication. This report on the DOX loading/release capability of MNF will set a new paradigm in view that MNF can resolve problems related to the self-heating of drug carriers during mild laser treatment with its thermal conducting properties.
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