A colorimetric assay for measuring iodide using Au@Ag core-shell nanoparticles coupled with Cu(2+).

Au@Ag core-shell nanoparticles (NPs) were synthesized and coupled with copper ion (Cu(2+)) for the colorimetric sensing of iodide ion (I(-)). This assay relies on the fact that the absorption spectra and the color of metallic core-shell NPs are sensitive to their chemical ingredient and dimensional core-to-shell ratio. When I(-) was added to the Au@Ag core-shell NPs-Cu(2+) system/solution, Cu(2+) can oxidize I(-) into iodine (I2), which can further oxidize silver shells to form silver iodide (AgI). The generated Au@AgI core-shell NPs led to color changes from yellow to purple, which was utilized for the colorimetric sensing of I(-). The assay only took 10 min with a lowest detectable concentration of 0.5 µM, and it exhibited excellent selectivity for I(-) over other common anions tested. Furthermore, Au@Ag core-shell NPs-Cu(2+) was embedded into agarose gels as inexpensive and portable "test strips", which were successfully used for the semi-quantitation of I(-) in dried kelps.

A simple, rapid and eco-friendly approach for the analysis of aromatic amines in environmental water using single-drop microextraction-gas chromatography.

Single-drop microextraction (SDME) coupled with gas chromatography-flame ionization detector (GC-FID) was developed for the extraction and determination of aromatic amines (AAs) in environmental water samples. A silicon tube was introduced for the SDME procedure by inserting it into the needle of the micro-injector. In this manner, a large volume of extractant is allowed to be suspended for the extraction, leading to the enhancement of method sensitivity and reproducibility. Extraction parameters which control the performance of SDME such as the type of microextraction solvent and volume, sample pH, ionic strength and extraction time were investigated and optimized. Under the optimized conditions, the SDME-GC method exhibited good linearity from 0.5 to 50 µg mL(-1) for aniline and 4-methylaniline and 0.1 to 50 µg mL(-1) for N-methylaniline and N, N-diethylaniline. The enrichment factors were calculated to be 42-509. The SDME-GC method was performed for the determination of AAs in environmental water samples including drinking, lake and sea water, and excellent recoveries and relative standard deviations (RSD values) ranging from 79.5 to 122.7% and 3.2 to 13.3%, respectively, were obtained. The results demonstrated that SDME-GC is a rapid, simple and effective sample preparation method and could be successfully applied for the determination of AAs in environmental water samples.

Beta-MnO2 3D nanostructures: mineralizer-assisted synthesis, characterization, and growth mechanism.

The beta-MnO2 three-dimensional (3D) nanostructures were synthesized in large area by a mineralizer-assisted hydrothermal route. KNO3 was introduced as inorganic mineralizer to direct the growth of beta-MnO2 3D nanostructures from Mn(NO3)2 solutions. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Possible growth mechanism of beta-MnO2 3D nanostructures was proposed based on comparative experiments, indicating that KNO3 mineralizer and the concentration of Mn(NO3)2 solution were the two decisive factors in the fabrication of beta-MnO2 3D nanostructures.

'Green' synthesis of nitro alcohols catalyzed by solid-supported tributylammonium chloride in aqueous medium.

A series of 1-aryl-2-nitroalkan-1-ols (5a-m; Table 2) was prepared in yields of 64-94% by Henry reaction between aromatic aldehydes and nitroalkanes in the presence of a dual catalytic system of KOH and polystyrene-supported tributylammonium chloride (PsTBAC; 2). The reactions were performed either in H2O containing 10% of THF or, in the case of liquid reagents (aldehydes and nitroalkanes), in neat H2O at room temperature. The immobilized phase-transfer catalyst, designed to be used for large-scale industrial processes, could be easily separated from the products, and effectively re-used several times, basically without loss in activity.