Fig. 7. (A) Lab-on-a-chip devices for the analytical detection of metallic NPs: microfluidic devices with either Hg (on the left) or Au (on the right) electrodes for the detection of metallic NP impact events under flowing conditions in the presence of a redox species in solution by electrocatalytic amplification. Adapted with permission from ref. 97; T. M. Alligrant, M. J. Anderson, R. Dasari, K. J. Stevenson and R. M. Crooks, Langmuir, 2014, 30, 13462–13469. Copyright 2014 American Chemical Society. (B) Electrochromic sensors: Ag nanoplates may be used in colorometric sensing applications by monitoring spectral shifts in their plasmon absorbance due to Fermi level equilibration with chemisorbed inorganic anions. Adapted with permission from ref. 87; X. C. Jiang and A. B. Yu, Langmuir, 2008, 24, 4300–4309. Copyright 2008 American Chemical Society. (C) Surface plasmon spectroscopy (SPS) of single metallic NPs: (top left) dark-field microscopy experimental setup consisting of a dark-field microscope with dark-field condenser, objective, CCD camera, and spectrometer and (top right) a cell for electrochemical charging under the dark-field microscope, comprising a steel shell with two Ag wires (one contacting the ITO to provide a working electrode, the other a quasi-reference) and an auxiliary Pt electrode. Adapted with permission from ref. 16; C. Novo, A. M. Funston, A. K. Gooding and P. Mulvaney, J. Am. Chem. Soc., 2009, 131, 14664–14666. Copyright 2009 American Chemical Society. Monitoring electrodeposition on single metallic NPs: (D) the position of the surface plasmon band peak of a single Au nanostar as a function of both time (red circles) and applied potential (blue line). The measurements were taken during electrodeposition of metallic Ag from an aqueous solution containing 6.7 × 10^–7 M AgNO₃ and 0.1 M NaNO₃. (E) Selected Rayleigh scattering spectra of the same gold nanostar collected at various applied potentials during the deposition process. The nanostar was coated with polyvinylpyrrolidone (PVP). (D and E) adapted with permission from ref. 98; M. Chirea, S. S. E. Collins, X. Wei and P. Mulvaney, J. Phys. Chem. Lett., 2014, 5, 4331–4335. Copyright 2014 American Chemical Society.