As important members of the fullerene family, C60 and its derivatives have become the most popular N-type organic narrow-band gap semiconductor. Expanding synthetic control over its hybrid nanostructures has become a major challenge. In this work, dimethylformamide was used to significantly reduce the rate of C60 precipitation, making it possible to synthesize a series of Au–C60 hybrid nanostructures, including a core–shell structure with a tunable shell thickness. On this basis, strong ligand-mediated interfacial energy controlled the formation of Au–C60 Janus structures with a tunable size of the C60 domain. The charge separation efficiencies of different Au–C60 hybrid structures were systematically studied. The photocurrent generation and transient fluorescence showed significantly improved charge separation, which was attributed to the physical separation of the Au and C60 domains. We believe that mechanistically understanding the design and synthesis of intricate Janus architectures would help future efforts in functional exploration.

Conspectus Nanosynthesis is the art of creating nanostructures, with on-demand synthesis as the ultimate goal. Noble metal nanoparticles have wide applications, but the available synthetic methods are still limited, often giving nanospheres and symmetrical nanocrystals. The fundamental reason is that the conventional weak ligands are too labile to influence the materials deposition, so the equivalent facets always grow equivalently. Considering that the ligands are the main synthetic handles in colloidal synthesis, our group has been exploring strong ligands for new growth modes, giving a variety of sophisticated nanostructures. The model studies often involve metal deposition on seeds functionalized with a certain strong ligand, so that the uneven distribution of the surface ligands could guide the subsequent deposition. In this Account, we focus on the design principles underlying the new growth modes, summarizing our efforts in this area along with relevant literature works. The basics of ligand control are first revisited. Then, the four major growth modes are summarized as follows: (1) The curvature effects would divert the materials deposition away from the high-curvature tips when the ligands are insufficient. With ligands fully covering the seeds, the sparser ligand packing at the tips would then promote the initial nucleation thereon. (2) The strong ligands may get trapped under the incoming metal layer, thus modulating the interfacial energy of the core–shell interface. The evidence for embedded ligands is discussed, along with examples of Janus nanostructures arising from the synthetic control, including metal–metal, metal–semiconductor, and metal–C60 systems using a variety of ligands. (3) Active surface growth is an unusual mode with divergent growth rates, so that part of the emerging surface is inhibited, and the growth is focused onto a few active sites. With seeds attached to oxide substrates, the selective deposition at the metal–substrate interface produces ultrathin nanowires. The synthesis can be generally applied to grow Au, Ag, Pd, Pt, and hybrid nanowires, with straight, spiral, or helical structures, and even rapid alteration of segments via electrochemical methods. In contrast, active surface growth for colloidal nanoparticles has to be more carefully controlled. The rich growth phenomena are discussed, highlighting the role of strong ligands, the control of deposition rates, the chiral induction, and the evidence for the active sites. (4) An active site with sparse ligands could also be exploited in etching, where the freshly exposed surface would promote further etching. The result is an unusual sharpening etching mode, in contrast to the conventional rounding mode for minimized surface energy. Colloidal nanosynthesis holds great promise for scalable on-demand synthesis, providing the crucial nanomaterials for future explorations. The strong ligands have delivered powerful synthetic controls, which could be further enhanced with in-depth studies on growth mechanisms and synthetic strat...

Precise structural control has attracted tremendous interest in pursuit of the tailoring of physical properties. Here, this work shows that through strong ligand‐mediated interfacial energy control, Au‐Cu2O dumbbell structures where both the Au nanorod (AuNR) and the partially encapsulating Cu2O domains are highly crystalline. The synthetic advance allows physical separation of the Au and Cu2O domains, in addition to the use of long nanorods with tunable absorption wavelength, and the crystalline Cu2O domain with well‐defined facets. The interplay of plasmon and Schottky effects boosts the photocatalytic performance in the model photodegradation of methyl orange, showing superior catalytic efficiency than the AuNR@Cu2O core–shell structures. In addition, compared to the typical core–shell structures, the AuNR‐Cu2O dumbbells can effectively electrochemically catalyze the CO2 to C2+ products (ethanol and ethylene) via a cascade reaction pathway. The excellent dual function of both photo‐ and electrocatalysis can be attributed to the fine physical separation of the crystalline Au and Cu2O domains.

Among plasmonic metals, Au is the best candidate for practical applications due to its intrinsic visible LSPR absorption, excellent stability and facile shape control and surface functionalization. [21][22][23][24][25] Generally, the LSPR of AuNPs is basically dependent on their shape, size, and structural aspect ratio (AR). [2,21,26,27] Much effort has been devoted to the controlled synthesis of AuNPs with various shapes. [28][29][30][31][32][33] To date, the synthesis of AuNPs in spheres, [34] cubes, [35] spikes, [36] rods, [37] plates, [38] bipyramids, [39] octahedra, [35] stars, [40] etc., has been extensively studied and is well controlled. As a result of this structural diversity, the LSPR absorptions of the different AuNPs are distributed widely within the visible and near-infrared (NIR) spectral range.Beyond shape control, structural hybridization is another effective way to tune the LSPR absorptions of Au nanostructures, which can lead to different plasmonic modes due to the intraparticle couplings of the elementary structural units. In general, plasmonic coupling can be divided into two types: capacitive and conductive couplings. Capacitive coupling, which is inversely proportional to the interparticle distance, usually occurs between separated AuNP units. When the AuNPs are linked by a conductive bridge, the charge transfer across the bridge induces the occurrence of the charge transfer plasmon (CTP) mode. [41][42][43][44] The resonance energy of the CTP is highly dependent on the conductance of the bridge, which determines the position of the CTP peaks.Recently, Duan, [45] Shi [46] , and Halas [47] reported Au matryoshka structures with tunable broad spectral absorptions in the NIR spectral range by engineering capacitive couplings among multiple Au shells. In Duan's and our recent works, the strong intraparticle capacitive couplings among the Au branches led to full spectrum absorption (black body) properties. [30,45] Effective conductive couplings were first achieved by introducing a conductive Au bridge between two Au nanodisks on a substrate by the lithography method, leading to CTP modes. By varying the conductance of the bridge, i.e., the different widths and lengths of the bridge, the CTP absorptions were readily tuned to within the middle IR spectral region.For the CTP structures synthesized by the lithography method, their applications are limited on substrate. To expand the study and application of CTP to colloidal systems, the solution phase synthesis of uniform nanostructures with tunable CTP is thus highly desired.The localized surface plasmon resonance (LSPR) is one of the important properties for noble metal nanoparticles. Tuning the LSPR on demand thus has attracted tremendous interest. Beyond the size and shape control, manipulating intraparticle coupling is an effective way to tailor their LSPR. The charge transfer plasmon (CTP) is the most important mode of conductive coupling between subunits linked by conductive bridges that are well studied for structures prepared on substrates b...