摘要:
We report on a glassy carbon electrode that was modified with a composite made from graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) that enables highly sensitive determination of L-tyrosine. The sensor was characterized by transmission electron microscopy and electrochemical impedance spectroscopy, and its electrochemical properties by cyclic voltammetry, chronocoulometry and differential pulse voltammetry. The GO/MWCNT hybrid exhibits strong catalytic activity toward the oxidation of L-tyrosine, with a well defined oxidation peak at 761 mV. The respective current serves as the analytical information and is proportional to the L-tyrosine concentration in two ranges of different slope (0.05 to 1.0 μM and 1.0 to 650.0 μM), with limits of detection and quantification as low as 4.4 nM and 14.7 nM, respectively. The method was successfully applied to the analysis of L-tyrosine in human body fluids. The excellent reproducibility, stability, sensitivity and selectivity are believed to be due to the combination of the electrocatalytic properties of both GO and MWCNT. They are making this hybrid electrode a potentially useful electrochemical sensing platform for bioanalysis. Figure A new L-tyrosine electrochemical sensor was fabricated based on graphene oxide and multiwalled carbon nanotube. The prepared sensor exhibits excellent electro-catalysis to the oxidation of L-tyrosine, and can improve determination sensitivity and decrease detection limit. This sensor was successfully applied to detect L-tyrosine in human fluids with satisfactory results.
摘要:
A copper(II) complex (CuL, 1) with aminothioether ligand and its new inclusion complex with β-cyclodextrin (CuL/β-CD, 2) have been prepared successfully. The binding modes of both complexes with calf thymus DNA were investigated by UV-visible and circular dichroism spectroscopies. Results show that both complexes mainly adopt electrostatic attraction binding mode with DNA and binding constants are (2.02 ± 0.02) × 103 and (1.79 ± 0.05) × 103 M-1, respectively. Both complexes are able to cleave pBR322 plasmid DNA efficiently in the presence of ascorbic acid and the activity of 2 is higher than that of 1. The DNA cleavages by 1 and 2 were inhibited strongly in the presence of DMSO and tert-butyl alcohol, which suggests that hydroxyl radicals are reactive oxygen species for the cleavage.
摘要:
A graphene oxide (GO) film coated glassy carbon electrode (GCE) was fabricated for sensitive determination of 4-nitrophenol (4-NP). The GO-based sensor was characterized by scanning electron microscope, atomic force microscopy and electrochemical impedance spectroscopy. The electrochemical behaviors of 4-NP at the GO-film coated GCE were investigated in detail. In 0.1 M acetate buffer with a pH of 4.8, 4-NP yields a very sensitive and well-defined reduction peak at the GO-modified GCE. It is found that the GO film exhibits obvious electrocatalytic activity toward the reduction of 4-NP since it not only increases the reduction peak current but also lowers the reduction overpotential. Based on this, an electrochemical method was proposed for the direct determination of 4-NP. Various kinetic parameters such as transfer electron number, transfer proton number and standard heterogeneous rate constant were calculated, and various experimental parameters were also optimized. Under the optimal conditions, the reduction peak current varies linearly with the concentration of 4-NP ranging from 0.1 to 120 mu M, and the detection limit is 0.02 mu M at the signal noise ratio of 3. Moreover, the fabricated sensor presented high selectivity and long-term stability. This electrochemical sensor was further applied to determine 4-NP in real water samples, and it showed great promise for simple, sensitive, and quantitative detection of 4-NP. (C) 2011 Elsevier B.V. All rights reserved.
期刊:
Bulletin of the Korean Chemical Society,2012年33(8):2499-2507 ISSN:1229-5949
通讯作者:
Li, Junhua
作者机构:
[Liu, Mengqin; Zhang, Fuzing; Xu, Zhifeng; Li, Junhua; Feng, Yonglan; Kuang, Daizhi] Hengyang Normal Univ, Dept Chem & Mat Sci, Hengyang 421008, Hunan, Peoples R China.
通讯机构:
[Li, Junhua] H;Hengyang Normal Univ, Dept Chem & Mat Sci, Hengyang 421008, Hunan, Peoples R China.
关键词:
Electrochemical detection;Melamine;Ascorbic acid;Recognition element
摘要:
A novel and convenient electrochemical method has been developed for sensitive determination of melamine (MEL) using ascorbic acid (AA) as the recognition element. The working electrode employed in this method was modified with the nanocomposite of hydroxyapatite/carbon nanotubes to enhance the current signal of recognition element. The interaction between MEL and AA was investigated by fourier transform infrared spectroscopy and cyclic voltammetry, and the experimental results indicated that hydrogen bonding was formed between MEL and AA. Because of the existing hydrogen bonding and electrostatic interaction, the anodic peak current of AA was decreased obviously while the non-electroactive MEL added in. It illustrated that the MEL acted as an inhibitor to the oxidation of AA and the decreasing signals can be used to detect MEL. Under the optimal conditions, the decrease in anodic peak current of AA was proportional to the MEL concentrations ranging from 10 to 350 nM, with a detection limit of 1.5 nM. Finally this newly-proposed method was successfully employed to detect MEL in infant formula and milk, and good recovery was achieved.
期刊:
Sensors and Actuators B-Chemical,2012年168:381-389 ISSN:0925-4005
通讯作者:
Deng, Peihong
作者机构:
[Deng, Peihong; Xu, Zhifeng; Li, Junhua; Feng, Yonglan] Hengyang Normal Univ, Dept Chem & Mat Sci, Hengyang 421008, Peoples R China.
通讯机构:
[Deng, Peihong] H;Hengyang Normal Univ, Dept Chem & Mat Sci, Hengyang 421008, Peoples R China.
关键词:
p-Nitrophenol;Salicylaldehyde-modified chitosan;Acetylene black paste electrode;Voltammetric determination
摘要:
A novel method has been developed for the determination of p-nitrophenol (p-NP), which was based on the enhanced electrochemical response of p-NP at an acetylene black paste electrode coated with salicylaldehyde-modified chitosan (denoted as S-CHIT/ABPE). In 0.2 mol L−1 HCl solution, p-NP yielded a sensitive reduction peak at −0.348 V. Compared with the poor response at conventional carbon paste electrode, S-CHIT/ABPE remarkably increased the peak current of p-NP. All the experimental conditions, which influence the electrochemical response of p-NP, were studied and the optimum conditions were achieved. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of 8.0 × 10−8 mol L−1 to 2.0 × 10−6 mol L−1 was developed for the determination of p-NP. The detection limit (S/N = 3) was also examined and a low value of 3.0 × 10−8 mol L−1 for 120 s accumulation was obtained. The method has been successfully applied to the determination of p-NP in water samples with good recovery in the range of 96–104%.