Facet‐Dependent Optical Properties of Semiconductor Nanocrystals

Recent observations of facet‐dependent electrical conductivity and photocatalytic activity of various semiconductor crystals are presented. Then, the discovery of facet‐dependent surface plasmon resonance absorption of metal–Cu₂O core–shell nanocrystals with tunable sizes and shapes is discussed. The Cu₂O shells also exhibit a facet‐specific optical absorption feature. The facet‐dependent electrical conductivity, photocatalytic activity, and optical properties are related phenomena, resulting from the presence of an ultrathin surface layer with different band structures and thus varying degrees of band bending for the {100}, {110}, and {111} faces of Cu₂O to absorb light of somewhat different wavelengths. Recently, it is shown that the light absorption and photoluminescence properties of pure Cu₂O cubes, octahedra, and rhombic dodecahedra also display size and facet effects because of their tunable band gaps. A modified band diagram of Cu₂O can be constructed to incorporate these optical effects. Literature also provides examples of facet‐dependent optical behaviors of semiconductor nanostructures, indicating that optical properties of nanoscale semiconductor materials are intrinsically facet‐dependent. Some applications of semiconductor optical size and facet effects are considered.     

Ordered Arrangement and Optical Properties of Silica‐Stabilized Gold Nanoparticle–PNIPAM Core–Satellite Clusters for Sensitive Raman Detection

Gold–polymer hybrid nanoparticles attract wide interest as building blocks for the engineering of photonic materials and plasmonic (active) metamaterials with unique optical properties. In particular, the coupling of the localized surface plasmon resonances of individual metal nanostructures in the presence of nanometric gaps can generate highly enhanced and confined electromagnetic fields, which are frequently exploited for metal‐enhanced light–matter interactions. The optical properties of plasmonic structures can be tuned over a wide range of properties by means of their geometry and the size of the inserted nanoparticles as well as by the degree of order upon assembly into 1D, 2D, or 3D structures. Here, the synthesis of silica‐stabilized gold–poly(N‐isopropylacrylamide) (SiO₂‐Au‐PNIPAM) core–satellite superclusters with a narrow size distribution and their incorporation into ordered self‐organized 3D assemblies are reported. Significant alterations of the plasmon resonance are found for different assembled structures as well as strongly enhanced Raman signatures are observed. In a series of experiments, the origin of the highly enhanced signals can be assigned to the interlock areas of adjacent SiO₂‐Au‐PNIPAM core–satellite clusters and their application for highly sensitive nanoparticle‐enhanced Raman spectroscopy is demonstrated.     

Seed‐Induced Growth of Flower‐Like Au–Ni–ZnO Metal–Semiconductor Hybrid Nanocrystals for Photocatalytic Applications

The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au–Ni–ZnO metal–semiconductor hybrid nanocrystals with a flower‐like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room‐temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as‐prepared Au–Ni–ZnO nanocrystals are strongly photocatalytic and can be separated and re‐cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications.     

Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong,Stable, and Tunable Surface Plasmon Resonances

Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field‐enhanced spectroscopies, plasmon‐mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well‐mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag‐coated Au NRs (AuNR@Ag) and Au‐coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface‐enhanced Raman spectroscopy that are some 30‐fold higher than that of AuNR@Au. When incubated with a H₂O₂ solution (0.5 m ), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.     

Engineering Gold Nanorod–Copper Sulfide Heterostructures with Enhanced Photothermal Conversion Efficiency and Photostability

Plasmonic gold nanorods (Au NRs)–copper sulfide heterostructures have recently attracted much attention owing to the synergistically enhanced photothermal properties. However, the facile synthesis and interface tailoring of Au NRs–copper sulfide heterostructures remain a formidable challenge. In this study, the rational design and synthesis of Au NRs–Cu₇S₄ heterostructures via a one‐pot hydrothermal process is reported. Specifically, core–shell and dumbbell‐like Au NRs–Cu₇S₄ heterostructures are obtained with well‐controlled interfaces by employing the Au NRs with different aspect ratios. Both core–shell and dumbbell‐like Au NRs–Cu₇S₄ have proven effective as photothermal therapy agents, which offer both high photothermal stability and significant photothermal conversion efficiency up to 62%. The finite‐difference time domain simulation results confirm the coupling effect that leads to the enhanced local field as well as the optical absorption at the heterostructure interface. Importantly, these Au NRs–Cu₇S₄ heterostructures can be compatibly used as an 808 nm laser‐driven photothermal therapy agents for the efficient photothermal therapy of cancer cells in vitro. This study will provide new insight into the design of other noble metal–semiconductor heterostructures for a broad range of applications utilizing surface plasmon resonance enhancement phenomena.     

Plasmon Modes Induced by Anisotropic Gap Opening in Au@Cu2O Nanorods

Integration of semiconductors with noble metals to form heteronanostructures can give rise to many interesting plasmonic and electronic properties. A number of such heteronanostructures have been demonstrated comprising noble metals and n‐type semiconductors, such as TiO₂, ZnO, SnO₂, Fe₃O₄, and CuO. In contrast, reports on heteronanostructures made of noble metals and p‐type semiconductors are scarce. Cu₂O is an unintentional p‐type semiconductor with unique properties. Here, the uniform coating of Cu₂O on two types of Au nanorods and systematic studies of the plasmonic properties of the resultant core–shell heteronanostructures are reported. One type of Au nanorods is prepared by seed‐mediated growth, and the other is obtained by oxidation of the as‐prepared Au nanorods. The (Au nanorod)@Cu₂O nanostructures produced from the as‐prepared nanorods exhibit two transverse plasmon peaks, whereas those derived from the oxidized nanorods display only one transverse plasmon peak. Through electrodynamic simulations the additional transverse plasmon peak is found to originate from a discontinuous gap formed at the side of the as‐prepared nanorods. The existence of the gap is verified and its formation mechanism is unraveled with additional experiments. The results will be useful for designing metal–semiconductor heteronanostructures with desired plasmonic properties and therefore also for exploring plasmon‐enhanced applications in photocatalysis, solar‐energy harvesting, and biotechnologies.     

pH‐Dependent Galvanic Replacement of Supported and Colloidal Cu2O Nanocrystals with Gold and Palladium

Galvanic replacement reactions (GRRs) on nanoparticles (NPs) are typically performed between two metals, i.e., a solid metal NP and a replacing salt solution of a more noble metal. The solution pH in GRRs is commonly considered an irrelevant parameter. Yet, the solution pH plays a major role in GRRs involving metal oxide NPs. Here, Cu₂O nanocrystals (NCs) are studied as galvanic replacement (GR) precursors, undergoing replacement by gold and palladium, with the resulting nanostructures showing a strong dependence on the pH of the replacing metal salt solution. GRRs are reported for the first time on supported (chemically deposited) oxide NCs and the results are compared with those obtained with corresponding colloidal systems. Control of the pH enables production of different nanostructures, from metal‐decorated Cu₂O NCs to uniformly coated Cu₂O‐in‐metal (Cu₂O@Me) core–shell nanoarchitectures. Improved metal nucleation efficiencies at low pHs are attributed to changes in the Cu₂O surface charge resulting from protonation of the oxide surface. GR followed by etching of the Cu₂O cores provides metal nanocages that collapse upon drying; the latter is prevented using a sol–gel silica overlayer stabilizing the metal nanocages. Metal‐replaced Cu₂O NCs and their corresponding stabilized nanostructures may be useful as photocatalysts, electrocatalysts, and nanosensors.     

Yolk–Shell Nanostructure: An Ideal Architecture to Achieve Harmonious Integration of Magnetic–Plasmonic Hybrid Theranostic Platform

Magnetic–plasmonic hybrid nanoparticles (MPHNs) have attracted great interest in cancer theranostics. However, the relaxivity of the magnetic component is typically reduced by the plasmonic component in conventional core–shell structured MPHNs, due to the presence of a water‐impenetrable coating which severely restricts the proximity of protons to the magnetic portion. To circumvent this issue, yolk–shell structured MPHNs comprising a Fe₃O₄ core within a hollow cavity encircled by a porous Au outer shell are designed. As expected, the introduction of hollow cavity between the magnetic and plasmonic portions significantly prevents the decline in relaxivity of the Fe₃O₄ core caused by the Au layer. Moreover, in addition to conferring high near‐infrared absorption to plasmonic component, the hollow cavity and the pores in the outer shell can also provide a large storage space and release channels for anticancer drugs. Furthermore, the multicomponent nanoparticles (NPs) still have a compact size of less than 100 nm to ensure efficient tumor accumulation. Taken together, the yolk–shell Fe₃O₄@Au NPs can be regarded as an ideal magnetic–plasmonic theranostic platform for magnetic resonance/photoacoustic/positron emission tomography multimodal imaging and light‐activated chemothermal synergistic therapy.     

Improving All‐Inorganic Perovskite Photodetectors by Preferred Orientation and Plasmonic Effect

All‐inorganic perovskites have high carrier mobility, long carrier diffusion length, excellent visible light absorption, and well overlapping with localized surface plasmon resonance (LSPR) of noble metal nanocrystals (NCs). The high‐performance photodetectors can be constructed by means of the intrinsic outstanding photoelectric properties, especially plasma coupling. Here, for the first time, inorganic perovskite photodetectors are demonstrated with synergetic effect of preferred‐orientation film and plasmonic with both high performance and solution process virtues, evidenced by 238% plasmonic enhancement factor and 10⁶ on/off ratio. The CsPbBr₃ and Au NC inks are assembled into high‐quality films by centrifugal‐casting and spin‐coating, respectively, which lead to the low cost and solution‐processed photodetectors. The remarkable near‐field enhancement effect induced by the coupling between Au LSPR and CsPbBr₃ photogenerated carriers is revealed by finite‐difference time‐domain simulations. The photodetector exhibits a light on/off ratio of more than 10⁶ under 532 nm laser illumination of 4.65 mW cm^?2. The photocurrent increases from 0.67 to 2.77 μA with centrifugal‐casting. Moreover, the photocurrent rises from 245.6 to 831.1 μA with Au NCs plasma enhancement, leading to an enhancement factor of 238%, which is the most optimal report among the LSPR‐enhanced photodetectors, to the best of our knowledge. The results of this study suggest that all‐inorganic perovskites are promising semiconductors for high‐performance solution‐processed photodetectors, which can be further enhanced by Au plasmonic effect, and hence have huge potentials in optical communication, safety monitoring, and biological sensing.     

Macroscale Colloidal Noble Metal Nanocrystal Arrays and Their Refractive Index‐Based Sensing Characteristics

Colloidal noble metal nanocrystals are promising for a large number of optical and biotechnological applications. Many practical applications require the formation of large‐area, high‐density, and uniformly distributed metal nanocrystal arrays on various substrates, to overcome the limitations brought by the instability of colloidal metal nanocrystal solutions and the high cost of single‐particle spectroscopy characterizations. A method is developed for directly depositing colloidal metal nanocrystals, including Au nanospheres, Au nanorods, Au nanobipyramids, and (Au core)/(Ag shell) nanorods, from their solutions onto different substrates. The resultant nanocrystal arrays are relatively uniform and dense, with the peak extinction value of a single layer reaching 0.3. Their areas are up to 10 cm by 10 cm and can be further increased if larger‐size containers are utilized. The refractive index sensitivities are studied for Au nanorod arrays supported on glass slides, mesoporous silica and titania films, and capped with different molecules. Au nanorods deposited on mesoporous titania films are found to exhibit the highest index sensitivities, comparable to those of the same nanorod sample in solutions. It is expected that this approach will greatly facilitate plasmonic applications that require large‐area arrays of noble metal nanocrystals.     

Self‐Aligned Anisotropic Plasmonic Nanostructures

Great opportunities emerge not only in the generation of anisotropic plasmonic nanostructures but also in controlling their orientation relative to incident light. Herein, a stepwise seeded growth method is reported for the synthesis of rod‐shaped plasmon nanostructures which are vertically self‐aligned with respect to the surface of colloidal substrates. Anisotropic growth of metal nanostructure is achieved by depositing metal seeds onto the surface of colloidal substrates and then selectively passivating the seed surface to induce symmetry breaking in the subsequent seed‐mediated growth process. The versatility of this method is demonstrated by producing nanoparticle dimers and linear trimers of Au, Au–Ag, Au–Pd, and Au–Cu₂O. Further, this unique method enables the automatic vertical alignment of the resulting plasmonic nanostructures to the surface of the colloidal substrate, thereby making it possible to design magnetic/plasmonic nanocomposites that allow the dynamic tuning of the plasmon excitation by controlling their orientation using an external magnetic field. The controlled anisotropic growth of colloidal plasmonic nanostructures and their dynamic modulation of plasmon excitation further allow them to be conveniently fixed in a thin polymer film with a well‐controlled orientation to display polarization‐dependent patterns that may find important applications in information encryption.     

Core-shell metallic alloy nanopillars-in-dielectric hybrid metamaterials with magneto-plasmonic coupling

Combining plasmonic and magnetic properties, namely magneto-plasmonic coupling, inspires great research interest and the search for magneto-plasmonic nanostructure becomes considerably critical. Here we designed a nanopillar-in-matrix structure with core–shell alloyed nanopillars for both BaTiO₃ (BTO)-Au_0.5Co_0.5 (AuCo) and BTO-Au_0.25Cu_0.25Co_0.25Ni_0.25 (AuCuCoNi) hybrid systems, i.e., ferromagnetic alloy cores (e.g., Co or CoNi) with plasmonic shells (e.g., Au or Au/Cu). These core–shell alloy nanopillars are uniformly embedded into a dielectric BTO matrix to form a vertically aligned nanocomposite (VAN) structure. Both hybrid systems present excellent epitaxial quality and interesting multi-functionality, e.g., high magnetic anisotropy, magneto-optical coupling response, tailorable plasmonic resonance wavelength, tunable hyperbolic properties and strong optical anisotropy. These alloyed nanopillars-in-matrix designs provide enormous potential for complex hybrid material designs with multi-functionality and demonstrate strong interface enabled magneto-plasmonic coupling along with plasmonic and magnetic performance.     

Au–ZnO Nanocomposite Films for Plasmonic Photocatalysis

Nanocomposites based on plasmonic nanoparticles and metal‐oxide semiconductors are emerging as promising materials for conversion of solar energy into chemical energy. In this work, a Au–ZnO nanocomposite film with notably enhanced photocatalytic activity is successfully prepared by a single‐step process. Both ZnO and Au nanoparticles are synthesized in situ during baking of the film spin‐coated from a solution of Zn(CH₃COO)₂ and HAuCl₄. Furthermore, it is shown that this precursor solution can be formulated as a nanoink for the generation of micropatterns by microplotter printing, opening the way for the miniaturization of devices with enhanced properties for photocatalysis, optoelectronics, and sensing. The study demonstrates that Au–ZnO films exhibit 4.5‐fold enhanced photocatalytic properties for the decomposition of methyl orange upon sunlight exposure in comparison with ZnO films. Au nanoparticles improve significantly the photocatalytic activity of ZnO because they act as photosensitizers, absorbing photons at the localized surface plasmon resonance range (500–600 nm) and transferring electrons to the nearby ZnO semiconductor. XPS analysis of the Au–ZnO nanocomposite supports this explanation, indicating strong interactions between Au and ZnO.     

Colloidal Gold Nanorings and Their Plasmon Coupling with Gold Nanospheres

Gold nanorings are attractive as plasmonic metal nanocrystals because they have a hollow inner cavity. Their enhanced electric field inside the ring cavity is accessible, which is highly desirable for assembling with other optical components and studying their plasmon‐coupling behaviors. However, the lack of robust methods for synthesizing size‐controllable and uniform Au nanorings severely impedes the study of their attractive plasmonic properties and plasmon‐driven applications. Herein, an improved wet‐chemistry method is reported for the synthesis of monodisperse colloidal Au nanorings. Using circular Au nanodisks with different thicknesses and diameters as templates, Au nanorings are synthesized with thicknesses varied from ≈30 to ≈50 nm and cavity sizes varied from ≈90 to ≈40 nm. The produced Au nanorings are assembled with colloidal Au nanospheres to yield Au nanoring–nanosphere heterodimers in sphere‐in‐ring and sphere‐on‐ring configurations on substrates. The sphere‐in‐ring heterodimers exhibit the interesting feature of plasmonic Fano resonance upon the excitation of the dark quadrupolar plasmon mode of the Au nanorings. The open cavity in a nanoring holds a great promise for studying plasmon‐coupled systems, which will facilitate the construction of advanced metamaterials and high‐performance Fano‐based devices.     

Epitaxial Growth of Lattice‐Mismatched Core–Shell TiO2@MoS2 for Enhanced Lithium‐Ion Storage

Core–shell structured nanohybrids are currently of significant interest due to their synergetic properties and enhanced performances. However, the restriction of lattice mismatch remains a severe obstacle for heterogrowth of various core–shells with two distinct crystal structures. Herein, a controlled synthesis of lattice‐mismatched core–shell TiO₂@MoS₂ nano‐onion heterostructures is successfully developed, using unilamellar Ti_0.87O₂ nanosheets as the starting material and the subsequent epitaxial growth of MoS₂ on TiO₂. The formation of these core–shell nano‐onions is attributed to an amorphous layer‐induced heterogrowth mechanism. The number of MoS₂ layers can be well tuned from few to over ten layers, enabling layer‐dependent synergistic effects. The core–shell TiO₂@MoS₂ nano‐onion heterostructures exhibit significantly enhanced energy storage performance as lithium‐ion battery anodes. The approach has also been extended to other lattice‐mismatched systems such as TiO₂@MoSe₂, thus suggesting a new strategy for the growth of well‐designed lattice‐mismatched core–shell structures.     

Wrap‐Around Core–Shell Heterostructures of Layered Crystals

Engineered heterostructures create new functionality by integrating dissimilar materials. Combining different 2D crystals naturally produces two distinct classes of heterostructures, vertical van der Waals (vdW) stacks or 2D sheets bonded laterally by covalent line interfaces. When joining thicker layered crystals, the arising structural and topological conflicts can result in more complex geometries. Phase separation during one‐pot synthesis of layered tin chalcogenides spontaneously creates core–shell structures in which large orthorhombic SnS crystals are enclosed in a wrap‐around shell of trigonal SnS₂, forcing the coexistence of parallel vdW layering along with unconventional, orthogonally layered core–shell interfaces. Measurements of the optoelectronic properties establish anisotropic carrier separation near type II core–shell interfaces and extended long‐wavelength light harvesting via spatially indirect interfacial absorption, making multifunctional layered core–shell structures attractive for energy‐conversion applications.     

Structural verification and optical characterization of SiO2–Au–Cu2O nanoparticles

In this paper, SiO₂–Au–Cu₂O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu₂O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method Then, they were clung to the surface of Au seeds. The morphology of the resultant particles was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Transmission electron microscopy images demonstrate growth of monodispersed gold seeds and Cu₂O nanoparticles in narrow size up to 10 nm and 5 nm, respectively. The presence of gold and Cu₂O coating was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Absorption spectroscopy shows considerably 40 nm blue shift in absorption edge for SiO₂–Au–Cu₂O nanostructure rather than SiO₂–Au core/shell nanoparticles.     

Tunable Fano Resonance and Plasmon–Exciton Coupling in Single Au Nanotriangles on Monolayer WS2 at Room Temperature

Tunable Fano resonances and plasmon–exciton coupling are demonstrated at room temperature in hybrid systems consisting of single plasmonic nanoparticles deposited on top of the transition metal dichalcogenide monolayers. By using single Au nanotriangles (AuNTs) on monolayer WS₂ as model systems, Fano resonances are observed from the interference between a discrete exciton band of monolayer WS₂ and a broadband plasmonic mode of single AuNTs. The Fano lineshape depends on the exciton binding energy and the localized surface plasmon resonance strength, which can be tuned by the dielectric constant of surrounding solvents and AuNT size, respectively. Moreover, a transition from weak to strong plasmon–exciton coupling with Rabi splitting energies of 100–340 meV is observed by rationally changing the surrounding solvents. With their tunable plasmon–exciton interactions, the proposed WS₂–AuNT hybrids can open new pathways to develop active nanophotonic devices.     

Transition‐Metal‐Ions‐Induced Coalescence: Stitching Au Nanoclusters into Tubular Au‐Based Nanocomposites

Rod‐shaped assemblages of Au nanoclusters (AuNCs) can serve as self‐templating solid precursors to produce tubular Au‐based nanocomposites via the coalescence induced by transition metal ions. Specifically, when the AuNC assemblages react with transition metal ions with relatively high standard oxidation potentials such as Cu(II), Ag(I), Pd(II), and Au(III), a series of polycrystalline and ultrathin Au and Au_xM_y (where M = Cu, Ag, and Pd) alloy hollow nanorods (HNRs) can be obtained with further reduction; these metallic products are evaluated for electrooxidation of methanol. Alternatively, the above transition metal ions‐induced transformations can also be carried out after coating the AuNC assemblages with a layer of mesoporous SiO₂ (mSiO₂), giving rise to many mSiO₂‐coated Au‐based HNRs. Onto the formed AuPd_0.18 alloy HNRs, furthermore, a range of transition metal oxides such as TiO₂, Co₃O_4, and Cu₂O nanocrystals can be deposited easily to prepare metal oxide–AuPd_0.18 HNRs nanocomposites, which can be used as photocatalysts. Compared with those conventional galvanic replacement reactions, the controlled coalescence of AuNCs induced by transition metal ions provides a novel and efficient chemical approach with improved element efficiency to tubular Au‐based nanocomposites.     

Engineering the Au-Cu2O Crystalline Interfaces for Structural and Catalytic Integration

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.