Preparation and Characterization of Soft-Hard Block Copolymer of 3,4-IP-b-s-1,2-PBD Using a Robust Iron-Based Catalyst System.

A series of well-defined diblock copolymers, namely, 3,4-polyisoprene-block-syndiotactic-1,2-polybutadiene (3,4-PI-b-s-1,2-PBD), with a soft-hard block sequence were synthesized via an in situ sequential polymerization process using a robust iron-based catalytic system Fe(acac)3/(isocyanoimino) triptenylphosphorane (IITP)/AliBu3. This catalyst exhibits vigorous activity and temperature tolerance, achieving a polymerization activity of 5.41 × 106 g mol(Fe)-1 h-1 at 70 °C with a [IP]/[Fe] ratio of 15,000. Moreover, the quasi-living polymerization characteristics of the catalyst were verified through kinetic experiments. The first-stage polymerization of isoprene (IP) is performed at 30 °C to give a soft 3,4-PI block, and then a quantitative amount of 1,3-butadiene was added in situ to the quasi-living polymerization system to produce a second hard s-1,2-PBD. The s-1,2-PBD segments in block copolymers display a rodlike morphology contrasting with the spherulitic morphology characteristic of s-1,2-PBD homopolymers. The precise tunability of the length of the soft and hard chain segments of these novel elastic materials with the feed ratio of IP and BD, endowing them with outstanding mechanical properties and excellent dynamic mechanical properties, which are expected to be promising high-performance rubber materials.

N,S-GQDs mixed with CdTe quantum dots for ratiometric fluorescence visual detection and quantitative analysis of malachite green in fish.

N,S-GQDS was prepared through citric acid cracking method from thiourea and citric acid, a ratiometric fluorescence sensor was constructed for the detection of malachite green based on CdTe quantum dots and N,S-GQDs. Interestingly the color of this ratiometric fluorescence sensor could change from red to blue under UV light upon exposure to different amounts of malachite green, and this ratiometric fluorescence sensor could be used for visual detection of malachite green. Fluorescence emission spectra of this ratiometric fluorescence sensor with different amounts of malachite green were also analyzed, and there was a good linear relationship between F460nm/F666nm and concentrations of malachite green, the lowest limit detection could reach 0.4597 nmol/L. Furthermore, this proposed ratiometric sensor is used for quantitative analysis of malachite green in fish sample. Results shown that this ratiometric fluorescence sensor is feasibility and practicality for both visual detection and quantitative analysis of malachite green.

A fluorescence-quenching method for quantitative analysis of Ponceau 4R in beverage.

CdTe quantum dots was synthesized and used to quantitative analysis of Ponceau 4R in solution. With the excitation wavelength of 380nm the emission of CdTe quantum dots was quenched obviously by Ponceau 4R. In order to detect Ponceau 4R in mild condition the influences of fluorescence emission wavelength of CdTe quantum dots, pH value, temperature and reaction time were examined to establish the experimental condition. The linear response of the fluorescence intensity of CdTe quantum dots to Ponceau 4R allowed the quantitative analysis of Ponceau 4R in a range of 2.5-25µg/mL, and the limit of detection for Ponceau 4R was 0.025µg/mL. In addition, the responsive mechanism of this reaction system was investigated in detail by using the modified Stern-Volmer equation and thermodynamic calculation. Particularly, this method was used to quantitatively analyze the real sample, which indicated that this method could be more widely applied in similar samples.