Luminescent CaWO4:Tb3+-Loaded Mesoporous Silica Composites for the Immobilization and Release of Lysozyme

Luminescence-functionalized silica composites were synthesized by deposition of CaWO4:Tb3+ nanoparticles onto mesoporous silica (MS) materials by a Pechini-type 501 gel process. The pristine mesoporous silica materials comprise rodlike and spherical SBA-15-type silica materials in micron size, hollow silica spheres of around 2-4 mu m, and silica tubes with lengths of tens of micrometers. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and N-2 adsorption/desorption results confirm that the composites still conserve regular mesopore structure after the incorporation of the CaWO4:Tb3+ nanoparticles. These luminescent composites possessing suitable pore size, high BET surface area, and large pore volume (>1.0 cm(3)/g) were studied as supports for immobilization of lysozymes. These composites show various lysozyme adsorption capacities at different. solution pH values. CaWO4:Tb3+-loaded SBA-15-type composites and hollow spheres adsorb relatively high amounts (>500 mg/g composite at a solution pH of 10.0) of lysozyme (LYZ). The different enzyme adsorption and release properties of these luminescent mesoporous silica materials make them good candidates for specific bioimmobilization hosts. The emission intensity of Tb3+ in the CaWO4:Tb3+@rod-like SBA-15 varies with the total released amount of LYZ, which enables the lysozyme release to be tracked by the change in the luminescence intensity.