Fig. 1: Polymer precipitation-induced PGNP crystallization in solution during solvent evaporation.

a Schematic of polymer precipitant-induced PGNP crystallization: the added polymers precipitate onto PGNP surfaces to form small PGNP clusters that grow into crystals. b Representative TEM images of PGNP assemblies of (1.7k) Au-PS_0.70 NPs with various polymer precipitants. See “Methods” for detailed polymer information. Scale bars are 100 nm for PNIPAM-COOH and PS-b-PHEMAC, 1 μm for PBd-COOH and PP/PE, and 20 nm for all inset images. c SAXS results of PGNP crystals in a toluene solution of (5.3k) Au-PS_0.60 NPs with PP/PE. A simulated scattering profile of a perfect bcc lattice is shown for reference. d In situ SAXS studies of toluene solutions of (1.7k) Au-PS_0.70 NPs and PP/PE during the drying process. Plots are offset for clarity. e PGNP crystal growth in a toluene solution of (1.7k) Au-PS_0.70 NPs and PP/PE over time. Data points reflect the peak integration ratio between the sharp diffraction peak at q ~ 0.1 Å⁻¹ in d from PGNPs in crystals and the broad peak from PGNPs in the solution. f TEM images of (1.7k) Au-PS_0.70 NP assemblies with PP/PE upon fast solvent removal. Scale bars are 20 nm. PGNPs were dispersed at \({\varnothing }_{{\mathrm{NP}}}=0.1{\rm{vol}}. \%\) with \({\varnothing}_{{\mathrm{PP}}/{{\mathrm{PE}}}}\) = \(0.08{\rm{vol}}. \%\) and all other polymers at \({{{\varnothing }}}_{{\mathrm{polymer}}}\) = \(0.2{\rm{vol}}. \%\).