Xiaotong Chen

Highly sensitive and selective optical chemosensor for determination of Cu2+ in aqueous solution

A highly selective and sensitive rhodamine-based colorimetric chemosensor (1) for quantification of divalent copper in aqueous solution has been investigated in this work. It was designed using salicylaldehyde hydrazone and rhodamine 6G as copper-chelating and signal-reporting groups, respectively. In environmentally friendly media (50%(v/v) water/ethanol and 10mM NaAc-HAc neutral buffer (pH 7.0)), the sensor exhibited selective absorbance enhancement to Cu(2+) over other metal ions at 529 nm, with a dynamic working range of 0.05-5.00 microM and a detection limit of 10nM Cu(2+), respectively. To achieve fluorometric determination of Cu(2+), the Cu(2+)-induced absorbance enhancement of 1 was efficiently converted to fluorescence quenching by fluorescence inner filter effects using rhodamine B (RB) as a fluorophore. The selectivity and sensitivity of fluorescence analysis were similar to those of absorptiometric measurement. Both absorptiometric and fluorometric methods were successfully applied to the detection of Cu(2+) in three water samples.

Sensitive and selective fluorescence determination of trace hydrazine in aqueous solution utilizing 5-chlorosalicylaldehyde

A facile fluorescent method for the determination of hydrazine in aqueous solution with excellent sensitivity was developed. 5-chlorosalicylaldehyde (CS), a readily commercially available compound, was applied as the derivatization reagent in this work. Under the addition of CS to hydrazine aqueous solution (ethanol/water/acetic acid=30/66/4), an intense fluorescence enhancement was observed at 570 nm with a large stokes shift of approximately 170 nm. Upon the optimal condition, the fluorescence intensity linearly increased with the concentration of hydrazine in the range of 0.2 and 9.3 microM with a correlation coefficient of R2=0.9995 (n=10) and a detection limit of 0.08 microM. The R.S.D. was 2.0% (n=5). Determination of hydrazine in river and drinking water samples was successfully performed. Hydrazine vapor sensing by the proposed method was also reported.

Salicylaldehyde hydrazones as fluorescent probes for zinc ion in aqueous solution of physiological pH.

Salicylaldehyde hydrazones of 1 and 2 were synthesized and their potential as fluorescent probes for zinc ion was investigated in this paper. Both of the probes were found to show fluorescence change upon binding with Zn(2+) in aqueous solutions, with good selectivity to Zn(2+) over other metal ions such as alkali/alkali earth metal ions and heavy metal ions of Pb(2+), Cd(2+) and Hg(2+). They showed 1:2 metal-to-ligand ratio when their Zn(2+) complex was formed. By introducing pyrene as fluorophore, 2 showed interesting ratiometric response to Zn(2+). Under optimal condition, 2 exhibited a linear range of 0-5.0 microM and detection limit of 0.08 microM Zn(2+) in aqueous buffer, respectively. The detection of Zn(2+) in drinking water samples using 2 as fluorescent probe was successful.

Facile, sensitive and selective fluorescence turn-on detection of HSA/BSA in aqueous solution utilizing 2,4-dihydroxyl-3-iodo salicylaldehyde azine

A novel fluorescence turn-on detection method of human serum albumin (HSA) and bovine serum albumin (BSA) in aqueous solution is investigated using 2,4-dihydroxyl-3-iodo salicylaldehyde azine (DISA). Upon the addition of DISA to HSA/BSA solution, a fluorescence turn-on effect at 529 nm can be observed with a large stokes shift of approximately 129 nm based on hydrophobic binding-mode between protein and dye. Under the optimal condition, the linear ranges of fluorescence intensity for HSA and BSA are 0.1-30 microg mL(-1) with the relative correlation coefficient of R(2)=0.991 (n=10) and 0.3-50 microg mL(-1) with R(2)=0.997 (n=10); and the detection limits for HSA and BSA based on IUPAC (C(DL)=3S(b)/m) are 20 ng mL(-1) and 50 ng mL(-1), respectively.

Trace analysis of uranyl ion (UO22+) in aqueous solution by fluorescence turn-on detection via aggregation induced emission enhancement effect

A sensitive fluorescence turn-on method for trace amounts of uranyl ion (UO2(2+)) in solution has been developed in this study, based on aggregation induced emission enhancement (AIEE) characteristics of 4-pethoxycarboxyl salicylaldehyde azine (PCSA) induced by complex interaction between UO2(2+) and PCSA. Under optimized conditions, a fluorescence enhancement at 540 nm could be observed, which was linearly related to the concentration of UO2(2+) in the range of 1-25 ppb (part per billion). Analytical data showed that a detection limit of 0.2 ppb was achieved with the relative standard deviation (R.S.D.) 1.3% (n=5). The proposed method was successfully utilized in quantifying UO2(2+) in fuel processing wastewaters.

A ratiometric fluorescent chemodosimeter for Cu(II) in water with high selectivity and sensitivity

Coumarin derivative 1 was synthesized as an efficient ratiometric chemodosimeter for the detection of Cu(II) in 99% water/DMSO (v/v) at pH 7.0. Mechanism studies suggested that 1 formed a complex with Cu(II) at 2:1 ratio accompanied by quenching of green fluorescence at 524 nm; when the solution was heated to 50°C for 30 min, Cu(II)-promoted hydrolysis of coumarin lactone moiety of 1 occurred with bright blue fluorescence at 451 nm emerged. With fluorescence intensity ratio detection at 451 nm and 524 nm, 1 features an excellent sensitivity with the detection limit of 15 nmol L(-1) toward Cu(II) and a good selectivity over other metal ions.

Effective uranium(VI) sorption from alkaline media using bi-functionalized silica-coated magnetic nanoparticles

In this study, a bi-functionalized magnetic iron oxide composite which was covalently bound by ammonium and phosphonate groups has been employed as a novel sorbent for effective sorption of uranium(VI) from alkaline media. The maximum sorption capacity was observed at pH 9.0 with a capacity of 70.7 mg g−1 at CU(VI)initial = 21.7 mg L−1. The sorption isotherm followed a pseudo-second order kinetic equation and could be described by a Freundlich isotherm. The thermodynamics research showed that the sorption was a feasible and endothermic process. Since the as-prepared material could be separated by magnetic field without filtration and centrifugation, it could be a promising sorbent for highly-efficient removal of U(VI) from alkaline solution.

The development of a material for uranium sorption in NH3/N environments

A bi-functionalized hybrid silica (TP-silica) sorbent has been prepared through post-grafting of both positively charged and uranium chelate groups for efficient uranium(VI) uptake in a NH3/N environment. The introduction of the above two groups was achieved by ammonium and phosphonate moieties covalently anchored on the silica surface. The prepared sorbent was characterized using scanning electron microscopy, elemental analysis, and 13C-nuclear magnetic resonance. Detailed U(VI) sorption behaviors on the sorbent were also discussed. The combination of these two kinds of functionalized groups on the sorbent has shown to be an effective method for the U(VI) uptake in NH3/N environments.

The Electric Current Effect on Electrochemical Deconsolidation of Spherical Fuel Elements

For High-Temperature Gas-Cooled Reactor in China, fuel particles are bonded into spherical fuel elements by a carbonaceous matrix. For the study of fuel failure mechanism from individual fuel particles, an electrochemical deconsolidation apparatus was developed in this study to separate the particles from the carbonaceous matrix by disintegrating the matrix into fine graphite powder. The deconsolidated graphite powder and free particles were characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and ceramography. The results showed that the morphology, size distribution, and element content of deconsolidated graphite matrix and free particles were notably affected by electric current intensity. The electrochemical deconsolidation mechanism of spherical fuel element was also discussed.