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The selective crystallization behaviours of amorphous boscalid (BOS), BOS monohydrate and acetone/ethyl acetate/ethanol/methanol solutions are explained and predicted by mid-frequency Raman difference spectra analysis. The phase transition processes including solutions...

Two series of dual-core star-shaped polyfluorenes (DC-TPAs and DC-SBFs) based on a small quantity of green-emitting phenylmaleimide cores and a good deal of non-emissive cores were prepared by a one-pot Suzuki reaction. Triphenylamine (TPA) and 9,9-spirobifluorene (SBF) are employed as the non-emissive cores to construct DC-SBFs and DC-TPAs, respectively. Due to the π-conjugation extended by the fluorene units, the phenylmaleimide core displays a yellow emission which contributes to the white emission with the blue-emitting polyfluorene arms. DC-SBFs with four arms exhibit a better protection for emissive cores and a higher energy transfer efficiency than DC-TPAs with three arms. Consequently, the quantum yield of white emission of the polymers in the film was improved by changing TPA into SBF as the non-emissive core, reaching 0.80 for DC-SBF03. Additionally, the electrons and holes can be transported smoothly in DC-SBFs. A very high electroluminescent efficiency was obtained for DC-SBF03 with a maximum luminous efficiency of 17.4 cd A−1, power efficiency of 10.9 lm W−1 and external quantum efficiency of 6.2% when applied in the solution-processing white polymeric light-emitting devices (WPLEDs) with a LiF/Al cathode. The results denote that the non-emissive core plays a key role in the performance of the star-shaped single white polymers. It provides another way to improve the efficiencies of WPLEDs by designing simple non-emissive cores of the dual-core polymers, and avoiding the complicated synthesis of fluorophores.

Magnetic resonance (MR) imaging, with its inherent good spatial resolution and without tissue penetration depth limitations associated with other cell tracking techniques, is considered a valuable tool to assess the effects of cellular therapy. However, in order to allow in vivo tracking of transplanted cells with MRI, the cells must be labeled with contrast agents, usually in the form of magnetic or paramagnetic nanoparticles. Typically these are iron oxides, which are associated with a number of drawbacks related e.g. to the generation of hypointensities of the MR image due to signal loss. In this study, two chemically distinct manganese oxide-based nanostructures were developed and their feasibility as labels for human mesenchymal stem cells (hMSCs) was investigated. The ability to monitor the produced particles alone or within the labeled cells in vitro using MR imaging was further evaluated. Two novel synthetic approaches, the polyol process and microwave digestion, were combined to yield a “green”, and extremely rapid means of producing water-dispersible crystalline (MnO) and amorphous (MnOx) manganese oxides. To increase their water dispersability, capping agents in the form of organic polymers, poly(vinyl pyrrolidone) (PVP) and poly(acrylic acid) (PAA), were added to the synthesis process. Crystalline MnO was not formed when PAA was used as the capping agent, since Mn ions (Mn2+) cannot be hydrolyzed to Mn(OH)2, which is an intermediate step in the formation of MnO, under the acidic conditions provided by PAA. PVP, on the other hand, served to induce a spherical shape to the formed nanocrystals. Remarkably, the relaxation times of the as-prepared amorphous MnOx were significantly shorter than those of their crystalline counterparts, and the biocompatibility was also higher for MnOx. To the best of our knowledge, this is the first report which describes the use of an amorphous MnOx as a cell label for MR imaging.