Preparation of curcumin loaded mesoporous silica nanoparticles: determining polarizability inside the mesopores

Curcumin loaded mesoporopus silica nanoparticles (MSN) with various surface modifications have been prepared. SEM images indicate particle sizes in the range 200–300 nm. Various percentages of curcumin were successfully loaded within the nanoparticles, whereby the resultant loading degree increases linearly with the initial curcumin concentration. The polarizability inside the pores of MSN can be measured by using curcumin as fluorescence probe, which is critical since this cannot usually be easily reached using more conventional characterization methods. It was found that the polarizability value inside the pore is about 0.32, suggesting a solvent environment similar to methanol/ethanol. However, increase in the accumulated curcumin amount on the MSN reduces the energy gap between ground and excited state that saturated at higher curcumin loading due to homo energy transfer between the molecules. Surface modification of MSN also influences the spectral properties of curcumin due to change in pH, especially local accumulation of protons.