Cheng-Gen Xie

Stripping voltammetric detection of mercury(II) based on a surface ion imprinting strategy in electropolymerized microporous poly(2-mercaptobenzothiazole) films modified glassy carbon electrode

This work reports a surface ion imprinting strategy in electropolymerized microporous poly(2-mercaptobenzothiazole) (MPMBT) films at the surface of glassy carbon electrode (GCE) for the electrochemical detection of Hg(II). The Hg(II)-imprinted MPMBT/GCE exhibits larger binding to functionalized capacity, faster binding kinetics and higher selectivity to template Hg(II) due to their high ratio of surface-imprinted sites, larger surface-to-volume ratios, the complete removal of Hg(II) templates and larger affinity to Hg(II). The square wave anodic stripping voltammetry (SW ASV) response of the Hg(II)-imprinted MPMBT/GCE to Hg(II) is ca. 3.0 and 5.9 times larger than that at the direct imprinted poly(2-mercaptobenzothiazole) modified GCE and non-imprinted MPMBT/GCE sensor, respectively; and the detection limit for Hg(II) is 0.1nM (which is well below the guideline value given by the World Health Organization). Excellent wide linear range (1.0-160.0nM) and good repeatability (relative standard deviation of 2.5%) were obtained for Hg(II). The interference experiments showed that mercury signal was not interfered in the presence of Pb(II), Cd(II), Zn(II), Cu(II) and Ag(I), respectively. These values, particularly the high sensitivity and excellent selectivity compared favorably with previously reported methods in the area of electrochemical Hg(II) detection, demonstrate the feasibility of using the prepared Hg(II)-imprinted MPMBT/GCE for efficient determination of Hg(II) in aqueous environmental samples.

Electropolymerized surface ion imprinting films on a gold nanoparticles/single-wall carbon nanotube nanohybrids modified glassy carbon electrode for electrochemical detection of trace mercury(II) in water

Electrochemical detection of Hg(II) using a electropolymerized ion imprinting poly(2-mercaptobenzothiazole) films at the surface of gold nanoparticles/single-walled carbon nanotube nanohybrids modified glassy carbon electrode (PMBT/AuNPs/SWCNTs/GCE) is described for the first time. The Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor exhibits larger binding to functionalized capacity, larger affinity, faster binding kinetics and higher selectivity to template Hg(II). The differential pulse anodic stripping voltammetry (DPASV) response of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor to Hg(II) is ca. 3.7- and 10.5-fold higher than that at the non-imprinted PMBT/AuNPs/SWCNTs/GCE and the imprinted PMBT/AuNPs/GCE, respectively, and the detection limit for Hg(II) is 0.08 nM (S/N=3, which is well below the guideline value given by the World Health Organization) and a sensitivity of 0.749 μA nM(-1) was obtained. Excellent wide linear range (0.4-96.0 nM) and good repeatability (relative standard deviation of 2.6%) were obtained for Hg(II). The interference experiments show that Ag(I), Pb(II), Cd(II), Zn(II) and Cu(II) had little or no influence on the Hg(II) signal. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of electrochemical Hg(II) detection, demonstrate the analytical performance of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE toward Hg(II) is superior to the existing electrodes and could be used for efficient determination of Hg(II) in natural water samples.

Rhodamine-based fluorescent probe immobilized on mesoporous silica microspheres with perpendicularly aligned mesopore channels for selective detection of trace mercury(II) in water

A rhodamine-based organic–inorganic hybrid solid fluorescent chemosensor by covalently immobilized R6G derivative on core–shell structured mesoporous silica microspheres with perpendicularly aligned mesopore channels has been prepared. The fluorescent responses of the prepared chemosensor to Hg2+ have been investigated, and the results demonstrated that the proposed hybrid solid fluorescent chemosensor featured a high affinity Hg2+-specific fluorescence response in water by considering the highly dense modification of the rhodamine probe. The detection limit for Hg2+ is 0.1 nM (S/N = 3, which is well below the guideline value given by the World Health Organization) under optimized conditions. Excellent wide linear range (1.0–100.0 nM) and good repeatability (relative standard deviation of 3.2%) were obtained for Hg2+. The proposed chemosensor also exhibited excellent selectivity for Hg2+ over competing environmentally relevant metal ions, and can be used in a wide pH span and regenerated readily. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of fluorescent Hg2+ detection, demonstrated the analytical performance of the proposed chemosensor could be used for efficient determination of Hg2+ in natural water samples. Toward the purpose of practical application, the proposed chemosensor was further used to determine Hg2+ in real environmental water samples.

Electrochemical determination of trace copper(II) based on L-cysteine functionalized gold nanoparticle/CdS nanosphere hybrid

This paper describes a simple and efficient electrochemical assay for the determination of trace Cu(II) employing L-cysteine functionalized gold nanoparticles/CdS nanospheres/glassy carbon electrode (L-cys/AuNPs/CdS/GCE) as an enhanced sensing platform. The prepared sensor exhibited a high active surface area, excellent electron transfer properties, and greatly enhanced sensitivity for Cu(II) in comparison with AuNPs/CdS/GCE, L-cys/AuNPs/GCE and CdS/GCE, due to the synergistic effect of L-cysteine, Au nanoparticles and CdS nanospheres. The experimental conditions, namely preconcentration time, electrolyte and pH value, were optimized in order to maximize the sensitivity of the measurements. Under optimal conditions, the SWASV stripping signals for Cu(II) were linear in the concentration range of 0.5 to 200.0 nmol L−1, and a detection limit of 0.1 nmol L−1 (S/N = 3) was obtained. The prepared sensor also exhibited excellent repeatability and selectivity for Cu(II) over competing environmentally relevant metal ions. It was further applied to determine Cu(II) in real water samples, and the results agreed satisfactorily with the certified values.

A novel turn-on fluorescent sensor for highly selective detection of Al(III) in an aqueous solution based on simple electrochemically synthesized carbon dots

In this study, a simple and sensitive turn on fluorescent sensor for the detection of Al3+ ion in an aqueous solution was developed based on carbon dots (C-dots) obtained via one-step electrolysis of graphite in sodium hydroxide aqueous solution. The as-prepared C-dots exhibit excellent photoluminescence and up-conversion photoluminescence properties and have an average size of 5.0 nm. The as-prepared C-dots showed a light green luminescence emission under 365 nm ultraviolet excitation and could be used as a novel label-free turn on fluorescent probe for the selective detection of Al3+; this is quite different from the case of usual quenching effects of metal ions on fluorescent C-dots. The fluorescence enhancement effect of Al3+ ion on the as-prepared C-dots could be attributed to the chelation-enhanced fluorescence (CHEF) mechanism. Abundant oxygen functional groups on the surface of C-dots have chelation interaction with Al3+ and increase the rigidity of the C-dots, leading to fluorescence enhancement. Moreover, the as-prepared C-dots are highly selective for Al3+ over other metal ions, with a detection limit of 0.05 μM, and the linear relationship between fluorescence intensity and concentration of Al3+ is in the range of 0.1–7.2 μM. In addition, the as-prepared novel fluorescent probe was successfully applied for the direct analysis of Al3+ in a real environmental water sample.