Cornflower is a flowering weed and ornamental plant whose blue flowers have been used for food, decorative and colouring purposes. In this study, the upper (edible flowers) and lower (non-edible receptacle and involucre) parts of the capitulum were studied and compared for their chemical composition and bioactive properties. The flowers were richer in tocopherols, organic acids, and apigenin derivatives (mainly apigenin-7-O-glucuronide-4′-O-(6-O-malonylglucoside)) than the non-edible bristly part (where syringic acid predominated). Four cyanidin derivatives were identified in the flowers. The extract of the non-edible part was more efficient in inhibiting the formation of thiobarbituric acid reactive substances (TBARS), the bleaching of β-carotene, and the haemolysis of the erythrocytes membrane. In general, the extracts were more active against Gram-positive bacteria and had no cytotoxicity against non-tumour liver PLP2 cells. Therefore, while flowers are a potential source of natural cyanidin-based colorants, the lower part of the capitulum has bioactive properties to be exploited in different food or pharmaceutical formulations.
Transparent luminescent nanocomposites were obtained using the bulk polymerization of transparent
dispersions containing manganese-doped ZnS nanoparticles with a crystallite size of 2 nm in a mixture
of methyl methacrylate and acrylic acid. The effective diameter in the monomer dispersions is 22 nm as
determined using dynamic light scattering and depends on the composition of the continuous phase but
is significantly higher than the primary crystallite size of the ZnS:Mn nanoparticles initially obtained
from the precipitation reaction. The dispersions are stable up to 8 months. Deprotonated carboxylate
groups are detected in IR spectra (1547, 1437 cm-1) of particles isolated from a stable dispersion indicating
the presence of surface-bound acrylate molecules. Thermal bulk polymerization of the entire dispersions
is suitable for production of luminescent acrylic glasses with an emission maximum at 590 nm (330 nm
excitation) and a quantum yield of 29.8%. Ultramicrotome cuts of the nanocomposites with a thickness
of 50−100 nm were prepared for transmission electron microscopic investigations. In the micrographs,
a low degree of agglomeration is observed and the agglomerate diameter is below 20 nm. In the
nanocomposites, light scattering and turbidity is minimized due to the small particle size and high degree
of dispersion, resulting in highly transparent acrylic glasses with a transmittance as high as 87% (600
nm).
At present, thick film (powder based) alternating current electroluminescence (AC-EL) is the only technology available for the fabrication of large area, laterally structured and coloured light sources by simple printing techniques. Substrates for printing may be based on flexible polymers or glass, so the final devices can take up a huge variety of shapes. After an introduction of the underlying physics and chemistry, the review highlights the technical progress behind this development, concentrating on luminescent and dielectric materials used. Limitations of the available materials as well as room for further improvement are also discussed.
Review: Non‐conventional phosphor host materials such as cryptands (see Figure) or zeolites now offer potential alternatives to the traditional inorganic solid‐state materials which find applications in e.g. fluorescent lamps, T.V. sets, or X‐ray detectors. Recent efforts to further optimize conventional materials are reviewed and a forward look is taken at the new‐generation materials which could further extend the physical limits of luminescence.
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