Determination of Dopamine in the Presence of Ascorbic Acid Using a Poly(Amidosulfonic Acid) Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) was modified with electropolymerized films of amidosulfonic acid in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In pH 7.0 PBS, the anodic peak current increased linearly with the concentration of DA in the range of 5.0×10^–7 1.0×10^–4moldm^–3, with a correlation coefficient of 0.9932, and a detection limit (S/N=3) of 1.0× 10^–7moldm^–3. The relative standard deviation of 10 successive scans was 2.5% for 1.0×10^–6moldm^–3 DA. The interference of ascorbic acid (AA) with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly(amidosulfonic acid) film in pH 7.0 PBS. The proposed method exhibited good recovery and reproducibility.     

A lead(II) sensor based on a glassy carbon electrode modified with Fe3O4 nanospheres and carbon nanotubes

We have developed a highly sensitive and selective sensor for lead(II) ions. A glassy carbon electrode was modified with Fe₃O₄ nanospheres and multi-walled carbon nanotubes, and this material was characterized by scanning electron microscopy and X-ray diffraction. The electrode displays good electrochemical activity toward Pb(II) and gives anodic and cathodic peaks with potentials at ?496 mV and ?638 mV (vs. Ag/AgCl) in pH?6.0 solution. The sensor exhibits a sensitive and fairly selective response to Pb(II) ion, with a linear range between 20 pM and 1.6 nM, and a detection limit as low as 6.0 pM (at a signal-to noise ratio of 3). The sensor was successfully applied to monitor Pb(II) in spiked water samples.

A sensitive mercury (II) sensor based on CuO nanoshuttles/poly(thionine) modified glassy carbon electrode

Shuttle-like copper oxide (CuO) was prepared by a hydrothermal decomposition process. The resulting material was characterized by scanning electron microscopy and X-ray diffraction. It was then immobilized on the surface of a glassy carbon electrode modified with a film of poly(thionine). A pair of well-defined and reversible redox peaks for Hg(II) was observed with the resulting electrode in pH 7.0 solutions. The anodic and cathodic peak potentials occurred at 0.260 V and 0.220 V (vs. Ag/AgCl), respectively. The modified electrode displayed excellent amperometric response to Hg(II), with a linear range from 40 nM to 5.0 mM and a detection limit of 8.5 nM at a signal-to-noise ratio of 3. The sensor exhibited high selectivity and reproducibility and was successfully applied to the determination of Hg(II) in water samples.     

一类逆时反问题的改进正则化方法的收敛性

1引 言 非线性反问题广泛地存在于许多科学和工程问题中,反问题求解的主要困难在于问题的不适定性,即待求函数或参量不连续依赖于观测数据.用来求解非线性不适定问题的方法主要有Tikhonov正则化方法和迭代正则化方法[1,2,3,4].Tikhonov正则化方法是通过引入正则化参数及稳定泛函,将目标泛函离散化,从而得到解的一个稳定近似,即正则化解.     

An amperometric sensor for hydrazine based on nano-copper oxide modified electrode

A sensitive hydrazine sensor has been fabricated using copper oxide nanoparticles modified glassy carbon electrode (GCE) to form nano-copper oxide/GCE. The nano-copper oxide was electrodeposited on the surface of GCE in CuCl₂ solution at −0.4 V and was characterized by Scanning electron microscopy and X-ray diffraction. The prepared modified electrode showed a good electrocatalytic activity toward oxidation of hydrazine. The electrochemical behavior of hydrazine on nano-copper oxide/GCE was explored. The oxidative current increased linearly with improving concentration of hydrazine on nano-copper oxide/GCE from 0.1 to 600 μM and detection limit for hydrazine was evaluated to be 0.03 μM at a signal-to-noise ratio of 3. The oxidation mechanism of hydrazine on the nano-copper oxide/GCE was also discussed. The fabricated sensor could be used to determine hydrazine in real water.     

Sensor for lead(II) ion based on a glassy carbon electrode modified with double-stranded DNA and ferric oxide nanoparticles

Shuttle-like Fe₂O₃ nanoparticles (NPs) were prepared by microwave-assisted synthesis and characterized by scanning electron microscopy and X-ray diffraction. The NPs were immobilized on a glassy carbon electrode and then covered with dsDNA. The resulting electrode gives a pair of well-defined redox peaks for Pb(II) at pH 6.0, with anodic and cathodic peak potentials occurring at ?0.50?V and ?0.75?V (vs. Ag/AgCl), respectively. The amperometric response to Pb(II) is linear in the range from 0.12 to 40?nM, and the detection limit is 0.1?nM at a signal-to-noise ratio of 3. The sensor exhibits high selectivity and reproducibility.

A sensitive sensor for determination of l-tryptophan based on gold nanoparticles/poly(alizarin red S)-modified glassy carbon electrode

This work described a novel sensor for detection of l -tryptophan (Trp) by electrodeposition of gold nanoparticles (AuNPs) onto the poly(alizarin red S) film pre-cast on a glassy carbon electrode (GCE). Alizarin red S (ARS) was deposited on the surface of the GCE by electropolymerization, and gold nanoparticles (AuNPs) were attached onto the poly(ARS) film by electrodeposition, forming an AuNPs–PARS nanocomposite film-modified GCE (AuNPs–PARS/GCE). Then electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were used to characterize modified electrodes. The Nyquist diagrams of EIS indicated that the PARS film and AuNPs were successfully immobilized on the surface of GCE, and the electron transfer resistance value of electrode changed efficiently. The SEM image showed that the immobilized AuNPs were spherical in shape. The AuNPs–PARS/GEC displayed excellent amperometric response for Trp. The amperometric responses have two linear ranges from 0.02 to 0.5 μM and 0.5 to 20.0 μM, with sensitivities of 1.63(±0.08) and 0.21(±0.01)?μAμM^?1, respectively. Its detection limit was 6.7 nM at a signal-to-noise ratio of 3. The proposed method was applied to determine Trp.

The nano-Au self-assembled glassy carbon electrode for selective determination of epinephrine in the presence of ascorbic acid

Gold nanoparticles were self-assembled to the modified glassy carbon electrode (GC) with cysteamine (CA) to prepare the nano-Au/CA/GC modified electrode. The electrochemical behavior of epinephrine (EP) on the modified electrode was explored with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Epinephrine gave a pair of redox peaks at E_pa = 0.190 mV and E_pc = −0.224 mV (versus SCE), respectively. The nano-Au/CA/GC modified electrode shows an excellent electrocatalytic activity for the oxidation of EP. The modified electrode could be used to determine EP in the presence of ascorbic acid (AA). The response of catalytic current with EP concentration shows a linear relation in the range of 1.0 × 10⁻⁷ to 5.0 × 10⁻⁴ mol L⁻¹ with the correlation coefficient of 0.998. The detection limit is 4.0 × 10⁻⁸ mol L⁻¹. The modified electrode exhibited a good reproducibility, sensitivity and stability for the determination of EP injection.     

Sensitive DNA-hybridization biosensors based on gold nanoparticles for testing DNA damage by Cd(II) ions

A DNA biosensor was constructed by immobilizing a 20-mer oligonucleotide probe and hybridizing it with its complementary oligomer on the surface of a glassy carbon electrode modified with gold nanoparticles. The properties of the biosensor and its capability of recognizing its complementary sequence were studied by electrochemical impedance spectroscopy. The oxidative stress caused by cadmium ions can be monitored by differential pulse voltammetry using the cobalt(III)tris(1,10-phenanthroline) complex and methylene blue as electrochemical indicators. The biosensor is capable of indicating damage caused by Cd(II) ions in pH 6.0 solution. The results showed that the biosensor can be used for rapid screening for DNA damage.

超微电极上恒电位法苯胺的电化学聚合研究

本文对超微盘电极上苯胺的恒电位电化学聚合进行了研究，对聚合电流随时间的关系进行了详细的讨论，提出了径向聚合计时电流方程式并进行了验证，实验结果与理论相符。