ABSTRACT
The threshold structural transformation of the DUT-4 metal-organic framework (MOF) from an ordered to distorted phase during exposure to ambient conditions has been revealed. The in situ X-ray diffraction analysis, in situ Raman and FTIR spectroscopy, scanning electron microscopy and synchronous thermal analysis have been used for investigation. The reversible effect of exposure time and humidity on such a phase transition has been confirmed. We also demonstrated that the observed phase transition correlated well with changes in the optical and electronic properties of DUT-4, paving the way to a new family of MOF-based phase change materials for optoelectronic applications.
ABSTRACT
The photoluminescence (PL) properties of composites obtained by embedding green-emitting semiconductor nanocrystals (NCs) of two different types (thiol-capped CdTe and CdSe/ZnS) into chitosan-based biopolymer particles were investigated. The synthesis of self-assembled particles from oppositely charged polysaccharides involved a preliminary electrostatic binding of positively charged chitosan chains by negatively charged functional groups of NC stabilizing ligands. The amount of NCs and the acidity of the solution were found to be important parameters influencing the PL. The PL properties were mainly discussed in terms of the colloidal stability of the particles and changes in energy gap of NCs. Generally, the obtained biocompatible composites with NCs randomly distributed within a biopolymer particle demonstrated a higher PL resistance to the solution acidity that expands the applicability range of thiol-capped NCs.
