Surface-enhanced Raman scattering (SERS) and photoluminescence (PL) are important photoexcitation spectroscopy techniques; however, understanding how to analyze and modulate the relationship between SERS and PL is rather important for enhancing SERS, having a great effect on practical applications. In this work, a charge-transfer (CT) mechanism is proposed to investigate the change and relationships between SERS and PL. Analyzing the change in PL and SERS before and after the adsorption of the probe molecules on Nd-doped ZnO indicates that the unique optical characteristics of Nd³⁺ ions increase the SERS signal. On the other hand, the observed SERS can be used to explain the cause of PL background reduction. This study demonstrates that modulating the interaction between the probe molecules and the substrate can not only enhance Raman scattering but also reduce the SERS background. Our work also provides a guideline for the investigation of CT as well as a new method for exploring fluorescence quenching.

Ternary noble metal–semiconductor nanocomposites (NCs) with core–shell–satellite nanostructures have received widespread attention due to their outstanding performance in detecting pollutants through surface-enhanced Raman scattering (SERS) and photodegradation of organic pollutants. In this work, ternary Au@Cu₂O–Ag NCs were designed and prepared by a galvanic replacement method. The effect of different amounts of Ag nanocrystals adsorbed on the surfaces of Au@Cu₂O on the SERS activity was investigated based on the SERS detection of 4-mercaptobenzoic acid (4-MBA) reporter molecules. Based on electromagnetic field simulations and photoluminescence (PL) results, a possible SERS enhancement mechanism was proposed and discussed. Moreover, Au@Cu₂O–Ag NCs served as SERS substrates, and highly sensitive SERS detection of malachite green (MG) with a detection limit as low as 10⁻⁹ M was achieved. In addition, Au@Cu₂O–Ag NCs were recycled due to their superior self-cleaning ability and could catalyze the degradation of MG driven by visible light. This work demonstrates a wide range of possibilities for the integration of recyclable SERS detection and photodegradation of organic dyes and promotes the development of green testing techniques.

The improvement of ferromagnetic properties is critical for the practical application of multiferroic materials, to be exact, BiFeO₃ (BFO). Herein, we have investigated the evolution in the structure and morphology of Ho or/and Mn-doped thin films and the related diversification in ferromagnetic behavior. BFO, Bi_0.95Ho_0.05FeO₃ (BHFO), BiFe_0.95Mn_0.05O₃ (BFMO) and Bi_0.95Ho_0.05Fe_0.95Mn_0.05O₃ (BHFMO) thin films are synthesized via the conventional sol-gel method. Density, size and phase structure are crucial to optimize the ferromagnetic properties. Specifically, under the applied magnetic field of 10 kOe, BHFO and BFMO thin films can produce obvious magnetic properties during magnetization and, additionally, doping with Ho and Mn (BHFMO) can achieve better magnetic properties. This enhancement is attributed to the lattice distortions caused by the ionic sizes difference between the doping agent and the host, the generation of the new exchange interactions and the inhibition of the antiferromagnetic spiral modulated spin structure. This study provides key insights of understanding the tunable ferromagnetic properties of co-doped BFO.