Photoluminiscent (PL) cellulose aerogels of variable shape containing homogeneously dispersed and surface-immobilized alloyed (ZnS)x(CuInS2)1-x/ZnS (core/shell) quantum dots (QDs) have been obtained by 1) dissolution of hardwood prehydrolysis kraft pulp in the ionic liquid 1-hexyl-3-methyl-1H-imidazolium chloride, 2) addition of a homogenous dispersion of quantum dots in the same solvent, 3) molding, 4) coagulation of cellulose with ethanol as antisolvent, and 5) drying of the resulting composite aerogels with scCO2. Both compatibilisation with the cellulose solution and covalent attachment of the quantum dots onto the surface of the regenerated cellulose was achieved through replacement of the 1-mercaptododecyl ligands typically used in alloyed (ZnS)x(CuInS2)1-x/ZnS QD synthesis by 1-mercapto-3-(trimethoxysilyl)-propyl ligands.The obtained materials have densities of 37.9 to 57.2 mg cm-3, and have BET surface areas of 296 to 686 m2 g-1comparable with non-luminiscent cellulose aerogels obtained according to the NMMO, TBAF/DMSO or Ca(SCN)2 routes. Depending mainly on the ratio of QD core constituents and to a minor extent on the cellulose/QD ratio, the emission wavelength of the novel aerogels can be controlled within a wide range of the visible light spectrum. Whereas higher QD contents lead to bathochromic PL shifts, hypsochromism is observed when the amount of cellulose at constant QD content is increased. Reinforcement of the cellulose aerogels - and hence significantly reduced shrinkage during scCO2 drying - is a beneficial side effect of a-mercapto-?-(trialkoxysilyl) alkyl ligands for QD capping and covalent QD immobilization onto the cellulose surface.

Fluorescent cellulose aerogels containing covalently immobilized (ZnS)x(CuInS2)?1-x?/ZnS (core/shell) quantum dots

247th National Meeting (2014)

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