Fig. 5: Design of 3D NP orgnization with nanoscale (in-plane) and photonic (interplane) spacing regimes.
From: Encoding hierarchical 3D architecture through inverse design of programmable bonds
a, Mesovoxel 8 is composed of six voxels utilizing five bond colours to build three distinct voxel NP planes, mirrored to create larger NP spacings. b, SAXS data for the synthesized crystal (black) versus modelled S(q) (red) with the associated indexing of Bragg peaks (Supplementary Figs. 46 and 47) and inset 2D SAXS pattern, corresponding to a tetragonal primitive lattice with lattice parameters a = b = 58.34 nm, c = 233.4 nm and α = β = γ = 90°. The inset plot is an enlargement of the scattering region beyond q = 0.01 Å, highlighting higher-order structural features. c,d, SEM images of silicated crystals. Scale bars, 2 µm (c), 1 µm (d). e, TEM image of the (100) crystal face after FIB sectioning. Scale bar, 200 nm. f, EDS scanning transmission electron microscopy (STEM) image of the same sample showing the location of Au within the structure (see Supplementary Fig. 59 for further details). g, Schematic of Bragg diffraction, where θ is the incident light angle, c is the distance between particle planes, a is the distance between in-plane particles, d is the particle diameter and neff is the background refractive index. h, Upper plot shows the mean and maximum diameters of Au NPs over growth cycles 0–3 (N = 2,508, 740, 520, 288 NPs, respectively, with error bars representing ±1 s.e.m.). Comparative optical microscope images of representative samples at NP growth cycle 0 (that is, the initial state, top) and at growth cycle 3 (bottom) are also shown (scale bars, 10 μm). The green background of the images is due to a Fabry–Pérot resonance near wavelength λ = 525 nm due the indium tin oxide glass coating, which has been subtracted from the reflectance spectra. Lower plot shows simulated (dashed line) and measured (solid lines) reflection spectra under normal incidence for particle growth cycles 0–3, showing pronounced Bragg peaks in the wavelength range of 625–650 nm. Each measured spectral curve is the average of six spectra taken from six distinct samples synthesized in the same batch. The raw spectra and additional sample images are included in Supplementary Section V.
