Fig. 2

a Raman spectroscopic intensity of 3-hydroxykynurenine bound on silver nanoparticles captured by a near-field probe and a confocal microscope. An inset figure presents silver colloidal nanoparticles acquired by an atomic force microscope. The use of this figure from Ref. [64] is permitted by the American Chemical Society. b Intracellular pH value imaging of in vitro cultured cells using a nanoscale sensor consisting of 4-mercaptobenzoic acid functionalized gold nanoparticles. This figure from [67] is re-published with the permission of the American Chemical Society