(Left) Experimental scheme showing detection of Cu(II) using G4-Sac dendrimers and Au-NW-induced SPR. (Right) TEM image showing the adsorption of G4-Sac dendrimers (in gray and black) onto a single Au-NW.
Absorbance of the Cu(II)-G4-Sac complex, where Cu(II) becomes undetectable below .
(a) Selectivity of G4-Sac toward Cu(II). Solid curve–control labeled G4-Sac; dashed curve—labeled G4-Sac and metal matrix containing Cr(III), Mn(II), Pb(II), and Hg(II); dotted curve—labeled G4-Sac, metal matrix, and Cu(II). The concentrations of each metal ion was . (b) Time evolution of FRET efficiency between labeled G4-Sac and Cu(II).
(a) Fluorescence emission spectrum of Alexa Fluor 633 dye (vertical axis, left, solid diamonds) and absorbance of Cu(II) (vertical axis, right, hollow diamonds) in aqueous solution. (b) Fluorescence emission spectra of labeled G4-Sac, Au-G4-Sac complex, Cu(II)-G4-Sac complex, and Au-G4-Sac-Cu(II) complex. The Cu(II) concentration is for all samples. Note a spectral shift of 3–5 nm in the presence of Au-NWs (hollow and solid squares), indicating the occurrence of SPR.
Average fluorescence emission intensity of G4-Sac-Cu(II) complexes with (dark bars) and without (light bars) Au-NWs.
(a) Simulation of electric field propagation from left to right near an Au-NW in aqueous solution. The length and diameter of the NW are and 30 nm, respectively. The dendrimers bound to the NW are spheres of 10 nm each in diameter to match their hydrodynamic size. The number of dendrimers bound on each side of the Au-NW is 240, with an equal spacing of 50 nm. (b) Zoomed-in view of localized electric field intensities at the Au-NW-dendrimer interface. (c) Normalized electric field intensity along the z-axis with (solid curve) and without an Au-NW (dashed curve), calculated for a dendrimer located from the left end of the Au-NW. The distance is defined as on the surface of the Au-NW.
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