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.

In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe₃O₄-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe₃O₄ hollow microspheres and Fe₃O₄-Au magnetic nanocomposite synthesis via a seed deposition process. Complementary structural, chemical composition and valence state studies validate that the as-obtained samples are formed in a pure magnetite phase. A series of characterizations including conventional scanning/transmission electron microscopy (SEM/TEM), Mössbauer spectroscopy, magnetic testing and elemental mapping is conducted to unveil the structural and physical characteristics of the developed Fe₃O₄-Au magnetic nanocomposites. By adjusting the quantity of Au seeds coating on the polyethyleneimine-dithiocarbamates (PEI-DTC)-modified surfaces of Fe₃O₄ hollow microspheres, the correlation between the amount of Au seeds and the catalytic ability of Fe₃O₄-Au magnetic nanocomposites for 4-nitrophenol (4-NP) is investigated systematically. Importantly, bearing remarkable recyclable features, our developed Fe₃O₄-Au magnetic nanocomposites can be readily separated with a magnet. Such Fe₃O₄-Au magnetic nanocomposites shine the light on highly efficient catalysts for 4-NP reduction at the mass production level.

This study introduces a multifunctional device based on Cu₂O/g-C₃N₄ monitoring and purification p–n heterojunctions (MPHs), seamlessly integrating surface-enhanced Raman scattering (SERS) detection with photocatalytic degradation capabilities. The SERS and photocatalytic performances of the Cu₂O in various morphologies, g-C₃N₄ nanosheets (NSs) and Cu₂O/g-C₃N₄ MPHs with different g-C₃N₄ mass ratios were systematically evaluated, with a particular emphasis on the Cu₂O/g-C₃N₄-0.2 MPH, where g-C₃N₄ constituted 20% of the total mass. Multiple optical and electrochemical tests revealed that the Cu₂O/g-C₃N₄-0.2 MPH effectively enhances charge separation and reduces charge transfer resistance. The Cu₂O/g-C₃N₄-0.2 SERS sensor exhibited a relative standard deviation (RSD) below 15% and achieved an enhancement factor (EF) of 2.43 × 10⁶ for 4-ATP detection, demonstrating its high sensitivity and consistency. Additionally, it demonstrated a 98.3% degradation efficiency for methyl orange (MO) under visible light within 90 min. Remarkably, even after 216 days, its photocatalytic efficiency remained at 93.7%, and it retained an 84.0% efficiency after four cycles. XRD and SEM analyses before and after cycling, as well as after 216 days, confirmed the structural and morphological stability of the composite, demonstrating its cyclic and long-term stability. The excellent performance of the Cu₂O/g-C₃N₄ MPH is attributed to its Z-type mechanism, as verified by radical trapping experiments. The evaluation of the self-cleaning performance of the Cu₂O/g-C₃N₄-0.2 SERS sensor demonstrated that its Z-scheme structure not only provides excellent self-cleaning capability but also enables the detection of both individual and mixed pollutants, while significantly enhancing the SERS signal response through an effective charge transfer enhancement mechanism.