Fig. 1

Stepwise formation and characterization of Au@Nb@H _x K_1−xNbO₃ NPPs. a Schematic and b, c crystallographic illustrations of the morphological evolution of templated H _x K_4−xNb₆O₁₇ crystallites to lamellar and tubular colloids. d Crystal structure of cubic HNbO₃ perovskite. e TEM image (scale bar: 70 nm) of tubular H _x K_1−xNbO₃ NSs, in which the hollow cavity functions as the host to breed the Au@Nb CS-NPs. f SAED pattern (top, scale bar: 3 nm), corresponding azimuthally averaged SEAD pattern (bottom) and g TEM image (scale bar: 100 nm) of the Au@Nb@H _x K_1−xNbO₃ NPPs. h Absorption spectrum (inset) and derived Tauc plot of the H _x K_1−xNbO₃ NSs. i Schematic highlights of the biomimicry of the Au@Nb@H _x K_1−xNbO₃ NPPs, wherein the Au@Nb CS-NPs as the “peas” are unidirectionally loaded into the tubular cavity of nanoscale H _x K_1−xNbO₃ as the “pods”. j HAADF-STEM image and EDXS elemental maps (scale bars: 20 nm) of the Au (red), Nb (blue), and combined Au/Nb distribution prove the structure of the Au@Nb@H _x K_1−xNbO₃ NPPs, in which the Au@Nb CS-NPs (lilac) are unidirectionally located inside the H _x K_1−xNbO₃ NSs (blue). Abbreviations used: OAm, oleylamine; TBA⁺, tetrabutylammonium cation; NS, nanoscroll; CS-NPs, core-shell nanoparticles; NPP, nanopeapod