Design and fabrication of a sensitive electrochemical sensor for uranyl ion monitoring in natural waters based on poly (brilliant cresyl blue).

New insights are proposed into enhancing detection of uranyl ions (UO22+) by electropolymerization brilliant cresyl blue-modified glassy carbon electrode (PBCB/GCE). The mercury-free PBCB/GCE sensor was applied to determine UO22+ in water samples by differential pulse adsorptive stripping voltammetry (DPAdSV). The unique combination of the PBCB/GCE and DPAdSV significantly improves sensitivity due to the polymer of high electroactive area and fast electron transfer rate. The DPAdSV current using a 3 mm diameter PBCB/GCE was proportional to the UO22+ concentration in the range 2.0-90.0 µg·L-1 (- 0.113 V vs. SCE) with a detection limit of 0.650 µg·L-1, RSD = 3.1% (n = 10), and 4.5% reproducibility. In addition, the sensitivity for UO22+ determination was further improved at using an 1 mm diameter PBCB/GCE, which enhances the efficiency of UO22+ deposition due to its higher current density. The 1 mm diameter PBCB/GCE based on DPAdSV technique could be used to determine uranyl ions in the concentration range 0.20-2.0 µg·L-1 (- 0.113 V vs. SCE) with a detection limit of 0.067 µg·L-1, RSD = 5.7 % (n = 10) and 5.4% reproducibility. Hence, the PBCB/GCE is a suitable candidate to substitute the mercury electrode. Graphical abstract.

Ratiometric fluorescence nanosensors based on core-shell structured carbon/CdTe quantum dots and surface molecularly imprinted polymers for the detection of sulfadiazine.

Sulfadiazine is an environmental pollutant derived from abuse of antibiotics. Its content in environmental water is closely related to human health. Thus, a novel dual-emission surface molecularly imprinted nanosensor is designed for the specific adsorption and detection of sulfadiazine. In the system, blue emissive carbon quantum dots wrapped with silica served as the internal reference signal for eliminating background interference, while red emissive thioglycolic acid modified CdTe quantum dots (CdTe QDs), which are low dimensional semiconductor materials by the combination of cadmium and tellurium with excellent optical properties, were encapsulated in the imprinted layer to offer recognition signal. The fluorescence of CdTe quantum dots was quenched and the fluorescence quenching degree of carbon quantum dots was inconspicuous with the increase of concentration of sulfadiazine, thereby reflecting the color change. The detection of sulfadiazine was successfully achieved in a concentration range of 0.25-20 µmol/L with detection limit of 0.042 µmol/L and nanosensors had specific recognition for sulfadiazine over its analogues. Compared to single-emission fluorescence sensors, ratiometric fluorescence nanosensors had wider linear range and higher detection accuracy. Furthermore, the nanosensors were also successfully applied for the determination of sulfadiazine in real water and milk samples with acceptable recoveries. The study provides a feasible method for the detection of sulfadiazine and a reference for the detection of sulfonamides.

Concerning the relative importance of enantiomorphic site vs. chain end control in the stereoselective polymerization of lactides: reactions of (R,R-salen)- and (S,S-salen)-aluminium alkoxides LAlOCH2R complexes (R = CH3 and S-CHMeCl).

The preparations and structures of LAlOCH(2)C(S)HMeCl, where L = (R,R) or (S,S)-N,N'-bis(3,5-di-tert-butyl-salicylidene)-1,2-cyclohexenediamino, are reported together with the respective LAlOEt compounds, and their reactivities toward L- and rac-lactides in various solvents reveal the surprising complexity of the stereopreference for the ring-opening event.