Microwave-assisted preparation of intense luminescent BODIPY-containing hybrids with high photostability and low leachability

Abstract

Organic-inorganic hybrids with high luminescence were facilely obtained by a one-pot process through the combination of sol–gel condensation and radical copolymerization. The sol–gel reaction of methyltrimethoxysilane (MeTMOS) was carried out together with radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methacrylate-tethering boron dipyrromethene (BODIPY) dye 1, which was prepared by the reaction of a meso-butyl-substituted BODIPY dye and potassium methacrylate, under microwave irradiation or conventional heating conditions. The obtained hybrids were characterized by UV-vis and photoluminescence spectroscopies, and differential scanning calorimetry (DSC) thermogram, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) measurements. Microwave irradiation led to a more rapid and homogeneous reaction as compared to conventional heating conditions. Therefore, the obtained hybrids by means of microwave irradiation showed higher transparency owing to inhibition of aggregation derived from π–π stacking of BODIPY units. Quantum yields (ΦF = ∼94%) of the obtained hybrids were higher than those of 1 in methanol solution. Photostability of the hybrids was improved in comparison with that of poly(HEMA-co-1) film due to shielding by silica matrices; i.e., the access of oxygen in the excited state of BODIPY units is avoided. Moreover, the elution of BODIPY dye 1 from the hybrids was significantly reduced as compared to BODIPY dye without the methacrylate group due to the covalent bond between HEMA polymer and 1.