Sensing nanoparticles: Small 5/2010

The cover image depicts a novel encapsulated nanoparticle probe system consisting of a pH-sensitive molecule embedded within the surface-enhanced Raman scattering (SERS) plasmonics hot spot. Ag nanoparticle clusters are prepared by self-assembly using bifunctional molecular linkers to create small junction volumes that produce intense SERS. Ideal positioning of the Raman tag and stabilizers is achieved by stepwise linking, coating with polymer and protein, and then infusing with the small Raman tag, which adsorbs onto the nanoparticle aggregate and at its pre-formed nanometer-sized junctions. By simultaneously using a fluorescent protein coat, the nanocluster becomes a multimodal tag for combined imaging by fluorescence and Raman, allowing tracking and sensing with one probe. Modifying the outer coat for cell uptake using a transfection agent permits intracellular nanoparticle tracking at the single-particle level. For more information, please read the Communication “Mapping Local pH in Live Cells Using Encapsulated Fluorescent SERS Nanotags” by M. Moskovits et al., beginning on page 618.