Fig. 1. (a) Schematic illustration of the self-assembly and film transfer process of gold nanoparticles (NPs) induced by PFT at the water-n-hexane interface; (b) Scanning electron microscope (SEM) images of a monolayer gold nanoparticle film with a particle size of 20 nm and interparticle spacing of 1-2 nm. Scale bars are 1 μm, 200 nm, and 50 nm, respectively. Inset: Image of a monolayer gold nanoparticle film in a beaker; (c-f) Images of gold nanoparticle superlattice films with different numbers of layers transferred onto a PDMS substrate using a layer-by-layer stacking method. Images from (c) to (f) represent one layer to four layers, respectively

Fig. 2. Reflectance spectra (a) and transmission spectra (b) of gold nanoparticle films with a size of 20 nm, from one to six layers, with the solid black line indicating the simulation results and the red line indicating the experimental measurements

Fig. 3. Near-field distribution of a thin film of gold nanoparticles with a diameter of 20 nm and an interparticle spacing of 1 nm in (a) a single layer, (b) a bilayer, (c) a six-layer (λ = 638 nm), and (d) a six-layer (λ = 778 nm). The plasma pattern of current distribution through the interior of the nanoparticles is demonstrated next to it, and the dipole moments in the particles of each layer are indicated by the white arrows

Fig. 4. Reflectance spectra of gold nanoparticle superlattice films with different numbers of layers and diameters (20 nm - black curve, 25 nm - red curve, 30 nm - blue curve). (a) Experimental measurement results; (b) Numerical simulation results