On the synthesis and characterisation of luminescent hybrid particles: Mo-6 metal cluster complex/SiO2

Photoluminescent silica-based materials are used in applications in photonics, sensing, and biological and medical sciences. Specifically, hybrid particles based on silica doped by photoluminescent octahedral molybdenum metal cluster complexes are inexpensive and readily available via the Stober process and thus are promising materials for diverse applications. We evaluated design of photoluminescent materials based on silica and {Mo6X8}(4+) clusters (where X = Cl, Br, I), including how synthesis conditions (chemical composition of metal cluster precursors (Bu4N)(2)[{Mo6X8}(NO3)(6)], loading of the precursor and presence of a surfactant) influence key parameters of the final materials, such as phase composition, size and morphology of the particles and photophysical characteristics. Our study revealed that hydrolysis of the molybdenum cluster precursors during the Stober process strongly affects both morphology and photophysical parameters of the materials, especially at high loadings. At relatively low loadings of the precursors, materials doped by {Mo6I8}(4+) clusters demonstrated the most promising set of properties-the highest photoluminescence quantum yields and efficient singlet oxygen generation-while particle size and morphology remained the same as for undoped SiO2 materials.