Xucheng Fu

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.