© RSC, 2017; DOI: 10.1039/c7tc03312e
By merging coordination compounds, like ccordination polymers and Metal-Organic Frameworks, with microparticles composites can be generated combining the properties of the contained components. This allows for example a fusion of luminescence of lanthanide-containing coordination polymers and the magnetism of magnetite microparticles. This results in composites potentially applicable as humidity sensors. If these luminescent composite particles are disperged in an organic solvent, they react with a luminescence colour change depending on the water amount in the solvent. Therefore, the water amount gets optically detectable.
This property combination was successful for our working group by functionalizing superparamagnetic magnetite micorpartcles with the luminescent Ln-N-MOFs 2∞[Ln2Cl6(bipy)3] · 2 bipy (Ln = Eu, Tb; bipy = 4,4'-Bipyridin) and the terephthalate network 3∞[Eu2(BDC)3] · 2 DMF · 2 H2O.
Depending on the type and composition of the core material and the coordination compound the properties can be optimized application-oriented. by co-spray-drying of magnetite or iron particles with titania a composit can be generated, which shows a strong magnetism and a white appearance. By subsequent solvothermal modification af a suchlike composite with a white light emitting coordination compound the resulting composite gains white luminescence as feature. During our research we were successful generating such a composite by combining of various synthesis methods and materials. This composite has a white appearance due to light reflection and refraction as well as white light emission under UV light and additionaly a strong magnetic behaviour. On this account this composite is referred to as "All White Magnet".
© RSC, 2020; DOI: 10.1039/c7tc03312e
By appropriate selection of the core material, some luminescence quenching substances can be utilized for sensor applications. If carbon particles are used as core material, which are functionalized with lanthanide containing luminophores the resulting composite can lose its luminescence properties subsequent to mechanical stress. Therefore, it can detect forces affecting the composite. As a part of our resarch — in cooperation with the Fraunhofer Institute for Silicate Research in Würzburg — our group was able to prepare composite particles, which exhibit exactly this behavioir. Carbon particles were encapsulated in Raspberry-like silica paricles by spray drying. The resulting particles are then functionalized with luminophores, like the MOF 3∞[Tb2(BDC)3(H2O)4], again by spray drying leading to a luminescent composite particle. Upon applying mechanical stress the core materials is released and quenches the luminescence. These composites are hence applicable as shear sensors. Read more about that in the section "Sensors"