Fig. 2

Mechanisms for precisely-controlled synthesis and broad spectral MEF of AgNIS. Schematic illustration for proposed mechanisms of Ag structures synthesized at A different seeding densities of AuNP catalysts and B different Ag precursor concentrations and reducing monosaccharides. In general, higher seeding densities, precursor concentrations, and reducing monosaccharides lead to higher degrees of structural continuity. C Extinction spectrum of AgNIS overlaid with excitation (lines) and emission (areas) of CF488A, CF555, and CF647 across a broad visible spectrum. D Electric field intensity distribution contours of AgNIS irradiated with polarized incident excitations at 488, 532, and 635 nm. White and blue arrows indicate gap and surface enhancements, respectively. E Line profiles of electric field intensities at different wavelengths indicated by the dotted lines in Fig. 2D. F Quantification of inhomogeneous gap distances for silver structures synthesized at a fixed 0.001 mg mL⁻¹ of PLL and various Tollens’ reagent concentrations. Automated thresholding on SEM images was first executed to acquire binary images with silver and gaps depicted in white and black, respectively. The gap distance is defined as twice the shortest distance from the 4-connectivity skeleton of gaps to the sliver structural boundaries and is shown in the color scale. Normalized gap distributions of Ag structures synthesized at different concentrations of G Tollens’ reagents (PLL: 0.001 mg mL⁻¹) and H PLL (Tollens’ reagent: 20 mM), fitted by the gamma distribution function on histograms (Additional file 1: Fig. S16). I Schematic diagram of the lift-off micropatterning procedures for controlled synthesis of AgNIS patterns. J Plasmon-enhanced multicolor fluorescence on micropatterned AgNIS of exemplified designed letters