Sensors core-shell particles

Besides, nanocomposites of conducting polymers with iron oxide nanoparticles have been extensively used directly as sensor system. For example, core-shell particles of Fe203 covered with PANI were prepared by oxidative polymerization. In this case the sensing properties were investigated towards uric acid and those were attributed to the presence of both PANI and Fe203 electrocatalytic center [133]. 

Paek K, Chung S, Cho C-H, Kim BJ (2011) Fluorescent and pH-responsive diblock copolymer-coated core-shell CdSe/ZnS particles for a color-displaying, ratiometric pH sensor. Chem Commun 47 10272... 

Figure 11.16 Multishell silica nanoparticle for ratiometric fluorescence sensing of Pb2+ ions, (a) Schematic working scheme of the sensor binding of the Pb2+ ions to the thiol groups present on the surface causes the quenching of the emission of the dansylamide dyes (labeled e when unperturbed and q when quenched) in the outer shell but not of the methoxynaphthalene dyes in the core (labeled r). (b) TEM micrograph of the particles (inset) and ratiometric behavior of the fluorescence emission at different Pb2+ concentrations.83 (Reprinted with permission from M. Arduini et al., Langmuir, 2007, 23, 8632—8636. Copyright 2007 American Chemical Society.)...

Tetramethylrhodamine, which is pH insensitive, was covalently linked to 50 nm silica particles that were coated with a 10 nm thick shell doped with the pH responsive fluorescein. In this case, shell structuring is not needed to obtain the ratiometric response but it produces an improvement of the sensor performance. In fact, the presence of sensitive units in the solvent-inaccessible core of the nanoparticle, which would result in a less pronounced ratiometric effect, is avoided. 

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