Enhanced sensitivity and selectivity of chemosensor for malonate by anchoring on gold nanoparticles

A novel organic-inorganic nanohybrided receptor 4 functionalized with bis-thiourea arms and then assembled on gold nanoparticles was synthesized. The preorganized system possesses phenylthiourea units for the spectrophotometric sensing of dicarboxylates, especially malonate, based on changes in the surface plasmon absorption of the gold nanoparticles (GNPs). The intensity of the absorbance band increases gradually with the concentration of dicarboxylates increasing. But such an ion-selective change in the plasmon band was not observed in control tests carried out by mono-thiourea-modified GNPs, receptor 3 and the free receptor 2. As it is shown from the association constants, derived from quantitative titrations, receptor 4 can selectively recognize dicarboxylate anions of shorter carbon chain, and has the highest affinity to malonate. The interaction properties for anions of receptor 4 were evaluated by ¹H NMR and UV-vis spectroscopic methods.