Engineering the Au-Cu2 O Crystalline Interfaces for Structural and Catalytic Integration

Engineering the Blackbody Absorption of the Au-Branch-on-Au-Plate Heterostructures

Utilizing the strong ligand control effects of l-cysteine (l-Cys), the growth of Au on Au triangular nanoplate (AuTN) seeds was continuously tuned from layer-by-layer (the Frank-van der Merwe) to layer-plus-island (the Stranski-Krastanov), and island (the Volmer-Weber) growth modes, leading to the formation of a series of Au-on-AuTN heterostructures. Within the window of VW growth mode (featured by the growth of Au spikes and branches on AuTNs), the effective localized surface plasmon resonance (LSPR) coupling led to the selective strengthening of the "valley" absorptions, leading to smooth and flat absorption curves. Interestingly, through engineering the number/density, size, and branching degree of the Au branches, except for the black color, full spectrum absorption within 400-1300 nm wavelength was achieved on Au-branch-on-AuTN structures. Mechanistic studies revealed that the blackbody absorption property of the Au-branch-on-AuTN originates from the well-balanced intraparticle LSPR couplings among the neighboring Au branches. The tunable blackness and the full spectrum absorption property made the Au-branch-on-AuTN heterostructure a suitable candidate for various plasmonic-related applications, such as a wide spectrum light absorber, photoacoustic imaging contrast agent, and photothermal therapy medium. In addition, our strong ligand control in Au-branch-on-AuTN heterostructures could be extended to other hybrid systems with diverse material combinations, so long as to find the proper strong ligand.

Gaining Deep Understanding of Electrochemical CO2 RR with In Situ/Operando Techniques

Electrocatalysis for CO2 conversion has been extensively studied to mitigate the energy shortage and environmental issues, which are gaining ever-increasing attention. However, the complicated CO2 reduction process and the dynamic evolution occurring on electrocatalyst surface make it hard to understand the catalytic mechanism. The development of advanced in situ/operando techniques intelligently coupled with electrochemical cells sheds light on the related study via capturing surface atomic rearrangement, tracing chemical state change of catalysts, monitoring the behavior of intermediates and products, and depicting microenvironment near the electrode surface. In this review, fundamentals of the state-of-the-art in situ/operando techniques are clarified first. Case studies on the in situ/operando techniques performed to probe the CO2 reduction reaction processes are then discussed in detail. Finally, conclusions and outlook on this field are presented.

Nanocomposites of Cu2O with plasmonic metals (Au, Ag): design, synthesis, and photocatalytic applications

Metal-semiconductor nanocomposites have been utilized in a multitude of applications in a wide array of fields, prompting substantial interest from different scientific sectors. Of particular interest are semiconductors paired with plasmonic metals due to the unique optical properties that arise from the individual interactions of these materials with light and the intercomponent movement of charge carriers in their heterostructure. This review focuses on the pairing of Cu2O semiconductor with strongly plasmonic metals, particularly Au and Ag. The design and synthesis of Au-Cu2O and Ag-Cu2O nanostructures, along with ternary nanostructures composed of the three components, are described, with in-depth discussion on the synthesis techniques and tunable parameters. The effects of compositing on the optical and electronic properties of the nanocomposites in the context of photocatalysis are discussed as well. Concluding remarks and potential areas for exploration are presented in the last section.

Strong Ligand Control for Noble Metal Nanostructures

ConspectusNanosynthesis 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 strategies, as well as functions and properties.