Functionalization of magnetic nanoparticles with organic molecules: Loading level determination and evaluation of linker length effect on immobilization

A general method is introduced to immobilize organic molecules on magnetic nanoparticles through silanization reactions and determine the maximum loading level by UV–vis spectroscopy. Loading levels of 1.5 × 10 −3 mol per gram of nanoparticle were obtained with structurally diverse compounds such as rhodamine B and glucosamine. The length of the linker did not have a significant effect on loading as comparable maximum amounts of rhodamine B were immobilized on magnetic nanoparticles regardless of the linker length. Interestingly, rhodamine B derivatives lost conjugation during synthetic manipulations due to reversible spiroisobenzofuran formation. Full regeneration of conjugation was found to be slow with rhodamine B attached on magnetic nanoparticles. The results obtained from these studies will be useful for studying surface functionalization of MNPs in general. Chirality, 2008. © 2007 Wiley‐Liss, Inc.