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Excess amount of analgesic and anti-inflammatory drug, such as indomethacin, often leads to serious gastrointestinal complications; therefore, amount of such active compound should be regulated in commercial drugs. This study proposes an efficient analytical technique to detect indomethacin selectively. We prepared and investigated electrochemical properties of a manganese dioxide-graphene nanocomposite film modified glassy carbon electrode (MnO2-Gr/GCE). The behavior of the modified electrode as electrocatalyst towards indomethacin oxidation was also examined. The cyclic voltammetric results reveal that the electrocatalytic activity for the oxidation of indomethacin can significantly be enhanced on the MnO2-Gr/GCE. Indomethacin exhibited a sensitive anodic peak at about 0.90 V at MnO2-Gr/GCE. The data obtained from differential pulse voltammetry showed that the anodic peak currents were linearly dependent on the indomethacin concentrations in the range of 1.0 × 10−7 to 2.5 × 10−5 mol/L with a detection limit of 3.2 × 10−8 mol/L (S/N = 3). Most importantly, the proposed method shows efficient and selective sensing of indomethacin in commercial pharmaceutical formulations. This is the first report of a voltammetric sensor for indomethacin using MnO2-Gr/GCE. We believe that this new method can be commercialized for routine applications in laboratories.
Zn1-xCuxO nanorods with different Cu concentrations are prepared by a hydrothermal method. Bent and aggregated nanorods are obtained, which is attributed to centripetal surface tension of the evaporation and coagulation processes of the water film on the ZnO nanorods. The broad visible band consists of one violet, three blue,and one green emission. The violet emission is due to the transition of electrons from zinc interstitial (Zni)levels to the valance band. The three blue emissions may be attributed to the transition from extended Zni levels, which are slightly below the simple Zni level, to the valance band. The change of the green emission may be the result of competition between oxygen vacancies (VO) and zinc vacancies (VZn).
ZnO thin films were grown on silicon substrates using a hydrothermal method. The XRD patterns show that all of the peaks can be attributed to the wurtzite structures of ZnO. The TC value of (002) plane and average crystal size increase first and then decrease with the increase of solution concentration. SEM and AFM results show that many dense hexagonal cylinder particles have been observed on the surface of the thin films, which grown at 0.08 and 0.10 mol/L. The surface roughness of the thin films deposited at 0.06,0.08, 0.10, and 0.12 mol/L are 24.5, 38.3, 32.0, and 39.4 nm, respectively. Surface wettability results show that the preferential orientation along c-axis and surface roughness contribute significantly to the hydrophobicity. The reversible switching between hydrophobicity and hydrophilicity is related to the synergy of the transition of wetting model, surface crystal structure, and surface roughness.
High magnetic field effects on the microstructure and magnetic properties of BaFe12O19 hexaferrites synthesized hydrothermal method have been investigated. The obtained results indicate that the lattice constant decreases gradually as the magnetic field strength increases, which may be attributed to the lattice distortion resulted from the high magnetic field. Polycrystalline BaFe12O19 samples prepared under magnetic field strength at zero and 5 T are single phase. It is found that application of external magnetic field during synthesis can induce orientated growth of the hexaferrite crystals along the easy magnetic axis. The magnetic properties can be effectively regulated by an application of high magnetic fields. It is observed that the BaFe12O19 prepared under a 5 T magnetic field exhibits a higher room-temperature saturation magnetization (66.3 emu/g) than that of the sample (43.6 emu/g) obtained without magnetic field. The results can be explained as the enhanced crystalline, improvement of Fe3+ ions occupancy and the oriented growth induced by the external magnetic field. The growing orientation of particles gives rise to increased coercivity due to the enhancement in shape anisotropy. It is expected that an application of magnetic field during the formation of magnetic nanoparticles could be a promising technique to modify magnetic properties with excellent performance.
The effect of indium doping on structural and magnetic properties of Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe1- xInx)12O22 (x=0, 0.02, 0.04, 0.06, 0.08 and 0.1) prepared by the solid state reaction method was investigated. The Rietveld refinement method was used to analyze the X-ray diffraction patterns. The magnetic transition temperatures associated with the proper-screw spin phase to the collinear ferrimagnetic spin phase transition can be efficiently modulated by varying indium content. The magnetic transition temperature increases to a maximum with indium content x=0.04 and then decreases with x, suggesting the possibility that electrically controlled magnetization reversal can be can be effectively tailored by varying indium content. The saturation magnetization at room temperature was decreased as increasing indium content, which can be explained as the metal ions occupation. It is worthy to note that the coercivity of In-doped samples was decreased drastically compared that of undoped sample, which is probably resulted from the reduction in anisotropy field with substitution of In3+ for Fe3+. The In-doped hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22 may be potential candidates for application in magnetoelectric devices.
Zn2+ and F- ions are successfully used to modify pure Li4Ti5O12 via a co-precipitation method followed by calcination at 400℃ for 5 h in an Ar atmosphere in order to further investigate the reaction mechanism of the fluoride modification process. Zn2+ and F- co-modified Li4Ti5O12 samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. After the modification process, no ZnF2 coating layer is formed on the surface of Li4Ti5O12, instead, F- ions react with Li4Ti5O12 to generate a new phase, composed of a small amount of anatase TiO2, rutile TiO2, LiF, and Zn2+ ions are suspected to form a ZnO coating layer on Li4Ti5O12 particles. The electrolyte reduction decomposition is suppressed in Zn2+ and F- co-modified Li4Ti5O12 due to the ZnO coating layer. 1 wt.% Zn2+ and F- co-modified Li4Ti5O12 exhibits the best rate capability, which leads to a charge capacity of 236.7, 227.8, 222.1, 202.7, 188.9 and 150.7 mAh g -1 at 0.2C, 0.5C, 1C, 3C, 5C and 10C, respectively, between 0 V and 3 V. Furthermore, 1 wt.% Zn2+ and F- comodified Li4Ti5O12 exhibits 96.0% charge capacity retention at 3C rate after 200 cycles, which is significantly higher than that of pure Li4Ti5O12 (78.4%).