Emerging opportunities based on two-dimensional (2D) layered structures can utilize a variety of complex geometric architectures. Herein, we report the synthesis and properties of a 2D+0D unique ternary platform-core-shell nanostructure, termed Ag@Cu₂O-rGO, where the reduced graphene oxide (rGO) 2D acting as a platform is uniformly decorated by Ag@Cu₂O core-shell nanoparticles. Cu₂O nanoparticles occupy the defect positions on the surface of the rGO platform and restore the conjugation of the rGO structure, which contributes to the significant decrease of the I_D/I_G intensity ratio. The rGO platform can not only bridge the isolated nanoparticles together but also can quickly transfer the free electrons arising from the Ag core to the Cu₂O shell to improve the utilization efficiency of photogenerated electrons, as is verified by high efficient photocatalytic activity of Methyl Orange (MO). The multi-interface coupling of the Ag@Cu₂O-rGO platform-core-shell nanostructure leads to the decrease of the bandgap with an increase of the Cu₂O shell thickness, which broadens the absorption range of the visible light spectrum.

A trilayer SiO₂/Ag/SiO₂ nanocap array was prepared on a two-dimensional template. When annealed at different temperatures, the curvature of the SiO₂/Ag/SiO₂ nanocap arrays increased, which led to Ag nanocap shrinkage. The stress provided by the curved SiO₂ layer induced the formation of Ag nanotwins. Ag nanotwins assisted the growth of nanoparticles when the neighboring nanotwins changed the local misorientations. Nanocap shrinkage reduced the surface plasmon resonance (SPR) coupling between neighboring nanocaps; concurrently, grain growth decreased the SPR coupling between the particles in each nanocap, which led to a red shift of the localized surface plasmon resonance (LSPR) bands and decreased the surface-enhanced Raman scattering (SERS) signals.

Ag–SiO₂ nanomace arrays were prepared on a two-dimensional ordered colloidal (2D) polystyrene sphere template by co-sputtering Ag and SiO₂ in a magnetron sputtering system. The lateral size of the nanomaces and the distance between the neighbor nanomaces were controlled by adjusting the etching time of the 2D template. The nanomaces were composed of SiO₂-isolated Ag nanoparticles, which produced surface-enhanced Raman scattering (SERS) enhancement, and 3D hot spots were created between the neighbor nanomaces. When the distance between the nanomaces was sufficiently large, triangle-shaped nanostructures on silicon substrate were observed, which also contributed to the enhancement of the SERS signals. The finite-difference time-domain (FDTD) method was used to calculate the electromagnetic field distributions in the Ag–SiO₂ nanomace arrays, which generated physical reasons for the change of the SERS signals.

Fluoride ferroelectrics containing 3d transition metal ions are potential multiferroic candidates due to their ionic bonds rather than the covalent bonds in oxide ferroelectrics. In this work, Pb3Fe2F12 ceramics are prepared by solid-state reaction. Rietveld refinement of the x-ray diffraction pattern suggests that Pb3Fe2F12 adopts a crystalline structure similar to that of Pb5Fe3F19, containing FeF6 octahedra chains and isolated FeF6 octahedra. The deficiency of Pb content leads to the mixed valence states of Fe ions and strong distortion among the octahedra, thus, complicating exchange interactions between Fe ions. The antiferromagnetic transition temperature TN1 is observed at 160 K, which is significantly higher than that of stoichiometric Pb5Fe3F19. Various magnetic anomalies are observed at low temperatures due to the onset of different antiferromagnetic exchange interactions between Fe ions of different strengths with TN2 (∼45 K), TN3 (∼37 K), and TN4 (∼10 K). Weak ferromagnetism can be observed below TN2, and significant exchange bias is observed below TN4. Dielectric peaks, together with a magnetic field tunable pyroelectric current peak, are observed at around TN1, suggesting the multiferroic nature and magnetoelectric coupling in Pb3Fe2F12.

SrFeF₅ is a typical spin-chain compound with strong intrachain and moderate interchain interactions. It has been predicted to be multiferroic due to the cycloidal spin structure. Herein, we provide clear experimental evidence of multiferroicity of SrFeF₅ by a systematic investigation of its magnetic, dielectric, and pyroelectric properties. The complicated interactions between neighboring Fe ions lead to the following three magnetic transitions. The divergence between field cooling (FC) and zero field cooling (ZFC) M(T) curves at T_N1∼ 80 K originates from the antiparallel alignment of neighboring spins along the chains due to the strong intrachain interactions. The sudden increase in magnetization with further divergence between the FC and ZFC M(T) curves is observed at T_N2 ∼ 42 K, which originates from the formation of cycloidal spin structure due to the contribution from moderate interchain interactions. An upturn of magnetization with further decreasing temperature at T_N3 ∼ 6 K is due to the contribution from the much weaker interchain interactions. Exchange bias starts to emerge at around 30 K, reaches a maximum at 20 K, and further increases below 10 K. A frequency independent peak of dielectric constant is observed at around T_N2, due to the cycloidal spin structure induced spontaneous polarization. This work helps to understand the multiferroic properties in the spin-chain fluorides.