895wileyonlinelibrary.com www.particle-journal.com www.MaterialsViews.com Here, a controlled synthesis of remarkable 3D photocatalysts is presented that is composed of ultrahigh-density unaggregated plasmonic Au nanoparticles (AuNPs) chemically bound to vertically aligned ZnO nanorod arrays (ZNA) through bifunctional molecular linkers. Experimental probes and electromagnetic simulations of electron transfer and localized plasmonic coupling processes are exploited to gain insight into the underlying light-irradiationinduced interactions in the 3D ZNA-AuNPs photocatalysts. Highly dense AuNPs on ZNA surfaces act as sinks for the storage of UV-generated electrons, which promote the separation of charge carriers and create numerous photocatalytic reaction centers. Furthermore, 3D fi nite-difference time domain simulation indicates that signifi cant visible light confi nement and enhancement around the ZNA-AuNPs interfacial plasmon "hot spots" contribute to effi cient conversion of light energy to electron-hole pairs. Signifi cantly, in comparison with the bare ZNA, the 10-nm-sized AuNPs-decorated ZNA exhibits 10.6-fold enhanced photoreaction rate in the entire UV-vis region. Moreover, various novel hybrid structures based on the plasmonic AuNPs and diverse nanostructures (fi lms, powdered nanorods, mesoporous, and nanotubes) or functional materials (multiferroic BiFeO 3 , CuInGaSe 2 absorber layers, and photoactive TiO 2 ) are successfully constructed using the present synthesis methodology. It may stimulate the progress in materials science toward the synthesis of multifunctional plasmonic heterostructures or devices.nanoparticles (Pt, Ag, or Au) deposited on a wide-bandgap oxide semiconductor (TiO 2 or ZnO). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The interaction of metal nanoparticles with the supporting semiconductor can improve the photocatalytic activity in two aspects. On one hand, the metal phase deposited on semiconductor retards the electron-hole recombination by serving as an electron sink for the storage of UV-light-excited electrons, and thus enhances the quantum yield. [1][2][3][4][5] On the other hand, surface plasmon resonance (SPR), defi ned as the collective oscillations of free electrons in plasmonic nanoparticles (especially Au) induced by visible light illumination, can enlarge the localized electric fi eld in the proximity of the metal particles; at the same time, the interaction of the localized electric fi eld with the neighboring semiconductor generates additional electron-hole pairs in the near-surface region of the semiconductor. [6][7][8][9][10][11][12] Most recently, the plasmonic effect has often been considered as the cause of visible photoactivity. [13][14][15][16][17][18][19] To comprehend the photocatalytic process fully, it requires an understanding of the following components: the semiconductor, the metal, the metal-support interface, and the interaction of these with chemical reactants. [ 1,3,7 ] However, the apparently simple process is diffi cult to make clear bec...