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1.
A Nafion-modified glassy carbon electrode incorporated with tobramycin for the voltammetric stripping determination of Cu2+ has been explored. The electrode was fabricated by tobramycin containing Nafion on the glassy carbon electrode surface. The modified electrode exhibited a significantly increased sensitivity and selectivity for Cu2+ compared with a bare glassy carbon electrode and the Nafion modified electrode. Cu2+ was accumulated in HAc-NaAc buffer (pH 4.6) at a potential of -0.6 V (vs. SCE) for 300 s and then determined by differential pulse anodic stripping voltammetry. The effects of various parameters, such as the mass of Nafion, the concentration of tobramycin, the pH of the medium, the accumulation potential, the accumulation time and the scan rate, were investigated. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 1.0 x 10(-9) to 5.0 x 10(-7) mol l(-1) with a correlation coefficient of 0.9971. The relative standard deviations for eight successive determinations were 4.3 and 2.9% for 1.0 x 10(-8) and 2.0 x 10(-7) mol l(-1) Cu2+, respectively. The detection limit (three times signal to noise) was 5.0 x 10(-10) mol l(-1). A study of interfering substances was also performed, and the method was applied to the direct determination of copper in water samples, and also in analytical reagent-grade salts with satisfactory results. 相似文献
2.
Cu nanotube arrays were fabricated by electroless deposition using porous anodic aluminium oxide membranes as templates. This was accomplished by a four-step procedure, i.e. pore-wall modification, polishing treatment, sensitization-activation and electroless deposition. The as-synthesized Cu nanotubes possess controllable inner diameter and open ends. 相似文献
3.
Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems. 相似文献
4.
Juan Hong Liang-Fu Tang Zhi Yang Yu-Ping Zhai Mujia Nan 《Transition Metal Chemistry》2005,30(4):439-444
A series of [M(CO)5I]− and [M2(CO)10I]− anion complexes have been synthesized by the photochemical reaction of PhCH2N(CH3)3I or FcCH2N(CH3)3I (Fc=ferrocenyl) with M(CO)6 (M = Cr, Mo or W), and characterized by elemental analyses, i.r., 1H-n.m.r. and 13C-n.m.r. spectra in the case of the molybdenum and tungsten complexes. These complexes exhibit considerably different electrochemical behavior, when investigated by cyclic voltammetry. The crystal structures of [PhCH2N(CH3)3][Cr(CO)5I] and [FcCH2N(CH3)3][W2(CO)10I] have been determined by X-ray diffraction, indicating that only weak contacts maybe exist between anions and cations by the I...H bond in the former, and there are no direct interactions between anions and cations in the latter. 相似文献
5.
建立了散射背景下测定人体血清中Zn^2+含量的激光热透镜光谱分析方法。比较了蛋白质微粒散射对于分光光度法和激光热透镜光谱分析法测定的影响。结果表明,激光热透镜光谱分析方法能够避免溶液中存留蛋白质微粒散射的影响。Zn^2+量在0~1.6μg/mL范围内呈线性关系(r=0.9986),检出限为1ng/mL。应用于人体血清中Zn^2+含量的测定,与原子吸收法测定结果基本一致。 相似文献
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The adsorptive and electrochemical behaviors of medecamycin were investigated on a glassy carbon electrode (GCE) pretreated by anodic oxidation at +1.8 V for 5 min in 0.025 mol l–1 NH3-NH4Cl (pH 8.6) solution. An adsorptive stripping voltammetric method for the determination of medecamycin at the pretreated glassy carbon electrode has been developed. Medecamycin was accumulated in NH3-NH4Cl buffer (pH 9.0) at a potential of –0.7 V (vs. saturated calomel electrode (SCE)) for a certain time, and then determined by second-order differential anodic stripping voltammetry. The second-order differential anodic stripping peak current at +0.72 V was proportional to the concentration of medecamycin in the range 2.0 g ml–1 to 50.0 g ml–1. The detection limit (three times the signal-to-noise) was 1.0 g ml–1 and the relative standard deviation of the results was 3.28% for eight successive determinations of 10.0 g ml–1 medecamycin. This method has been applied to the direct determination of medecamycin in commercial tablets and spiked urine samples with satisfactory results. 相似文献
9.
Using renewable green hydrogen and carbon dioxide (CO2) to produce methanol is one of the fundamental ways to reduce CO2 emissions in the future, and research and development related to catalysts for efficient and stable methanol synthesis is one of the key factors in determining the entire synthesis process. Metal nanoparticles stabilized on a support are frequently employed to catalyze the methanol synthesis reaction. Metal-support interactions (MSIs) in these supported catalysts can play a significant role in catalysis. Tuning the MSI is an effective strategy to modulate the activity, selectivity, and stability of heterogeneous catalysts. Numerous studies have been conducted on this topic; however, a systematic understanding of the role of various strengths of MSI is lacking. Herein, three Cu/ZnO-SiO2 catalysts with different strengths of MSI, namely, normal precipitation Cu/ZnO-SiO2 (Nor-CZS), co-precipitation Cu/ZnO-SiO2 (Co-CZS), and reverse precipitation Cu/ZnO-SiO2 (Re-CZS), were successfully prepared to determine the role of such interactions in the hydrogenation of CO2 to methanol. The results of temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) characterization illustrated that the MSI of the catalysts was considerably affected by the precipitation sequence. Fourier transform infrared reflection spectroscopy (FT-IR) results indicated that the Cu species existed as CuO in all cases and that copper phyllosilicate was absent (except for strong Cu-SiO2 interaction). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2O chemical titration results revealed that strong interactions between the Cu and Zn species would promote the dispersion of Cu species, thereby leading to a higher CO2 conversion rate and improved catalytic stability. As expected, the Re-CZS catalyst exhibited the highest activity with 12.4% CO2 conversion, followed by the Co-CZS catalyst (12.1%), and the Nor-CZS catalyst (9.8%). After the same reaction time, the normalized CO2 conversion of the three catalysts decreased in the following order: Re-CZS (75%) > Co-CZS (70%) > Nor-CZS (65%). Notably, the methanol selectivity of the Re-CZS catalyst was found to level off after a prolonged period, in contrast to that of Co-CZS and Nor-CZS. Investigation of the structural evolution of the catalyst with time on stream revealed that the high methanol selectivity of the catalyst was caused by the reconstruction of the catalyst, which was induced by the strong MSI between the Cu and Zn species, and the migration of ZnO onto Cu species, which caused an enlargement of the Cu/ZnO interface. This work offers an alternative strategy for the rational and optimized design of efficient catalysts. 相似文献
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