No abstract

aThe bismuth doped aluminosilicate phases leucite (KAlSi 2 O 6 ), gallium leucite (KGaSi 2 O 6 ) and pollucite (CsAlSi 2 O 6 ) display broadband NIR photoluminescence. The active center, responsible for this luminescence, is the Bi + monocation, which substitutes for the large alkali metal cations. The Al,Si-disorder in the aluminosilicate framework of studied crystal phases results in the heterogeneity of Bi + luminescent center population, which manifests itself in the characteristic dependency of the luminescence spectrum shape on the excitation wavelength. The relation of NIR emission in Bi + -doped leucite and pollucite phases to the luminescent properties of bismuth-doped glasses is also discussed.

The cold alkaline treatment or mercerization of cellulose is widely used in industry to enrich the cellulose raw with high-molecular-weight $$\alpha$$ α -cellulose. Washing out of hemicelluloses by alkalies is accompanied by the rearrangement of the cellulose chains’ packing, well known as a transition between cellulose I and cellulose II. Cellulose II can also be produced by the precipitation of the cellulose solutions (regeneration). The currently accepted theory implies that in cellulose II, both mercerized and regenerated, the macromolecules are arranged antiparallelly. However, forming such a structure in the course of the mercerization seems to be significantly hindered, while it seems to be quite possible in the regeneration process. In this work, we discuss the sticking points in the theory on the antiparallel structure of mercerized cellulose from a theoretical point of view summarizing all of the available experimental data in the field.

No abstract

No abstract

No abstract

No abstract

No abstract