Au@Cu₂O core-shell nanocomposites (NCs) were synthesized by reducing copper nitrate on Au colloids with hydrazine. The thickness of the Cu₂O shells could be varied by adjusting the molar ratios of Au: Cu. The results showed that the thickness of Cu₂O shells played a crucial role in the catalytic activity of Au@Cu₂O NCs under dark condition. The Au@Cu₂O-Ag ternary NCs were further prepared by a simple galvanic replacement reaction method. Moreover, the surface features were revealed by TEM, XRD, XPS, and UV–Vis techniques. Compared with Au@Cu₂O NCs, the ternary Au@Cu₂O-Ag NCs had an excellent catalytic performance. The degradation of methyl orange (MO) catalyzed by Au@Cu₂O-Ag NCs was achieved within 4 min. The mechanism study proved that the synergistic effects of Au@Cu₂O-Ag NCs and sodium borohydride facilitated the degradation of MO. Hence, the designed Au@Cu₂O-Ag NCs with high catalytic efficiency and good stability are expected to be the ideal environmental nanocatalysts for the degradation of dye pollutants in wastewater.

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.

Equipped with staggered gap p-n heterojunctions, a new paradigm of photocatalysts based on hierarchically structured nano-match-shaped heterojunctions (NMSHs) Cu₂S quantum dots (QDs)@ZnO nanoneedles (NNs) are successfully developed via engineering the successive ionic layer adsorption and reaction (SILAR). Under UV and visible light illumination, the photocatalytic characteristics of Cu₂S@ZnO heterojunctions with different loading amounts of Cu₂S QDs are evaluated by the corresponding photocatalytic degradation of rhodamine B (RhB) aqueous solution. The results elaborate that the optimized samples (S3 serial specimens with six cycles of SILAR reaction) by means of tailored the band diagram exhibit appreciable improvement of photocatalytic activities among all synthesized samples, attributing to the sensitization of a proper amount of Cu₂S QDs. Such developed architecture not only could form p–n junctions with ZnO nanoneedles to facilitate the separation of photo-generated carries but also interact with the surface defects of ZnO NNs to reduce the electron and hole recombination probability. Moreover, the existence of Cu₂S QDs could also extend the light absorption to improve the utilization rate of sunlight. Importantly, under UV light S3 samples demonstrate the remarkably enhanced RhB degradation efficiency, which is clearly testified upon the charge transfer mechanism discussions and evaluations in the present work. Further supplementary investigations illustrate that the developed nanoscale Cu₂S@ZnO heterostructures also possess an excellent photo-stability during our extensive recycling photocatalytic experiments, promising for a wide range of highly efficient and sustainably recyclable photocatalysts applications.

Facile and efficient photocatalysts using sunlight, as well as fast and sensitive surface-enhanced Raman spectroscopy (SERS) substrates, are urgently needed for practical degradation of tetracycline (TC). To meet these requirements, a new paradigm for PI/TiO₂/Ag organic‒inorganic ternary flexible microfibers based on semiconducting titanium dioxide (TiO₂), the noble metal silver (Ag) and the conjugated polymer polyimide (PI) was developed by engineering a simple method. Under sunlight, the photocatalytic characteristics of the PI/TiO₂/Ag flexible microfibers containing varying amounts of Ag quantum dots (QDs) were evaluated with photocatalytic degradation of TC in aqueous solution. The results demonstrated that the amount of Ag affected the photocatalytic activity. Among the tested samples, PI/TiO₂/Ag-0.07 (93.1%) exhibited a higher photocatalytic degradation rate than PI/TiO₂ (25.7%), PI/TiO₂/Ag-0.05 (77.7%), and PI/TiO₂/Ag-0.09 (63.3%). This observation and evaluation conducted in the present work strongly indicated a charge transfer mechanism. Moreover, the PI/TiO₂/Ag-0.07 flexible microfibers exhibited highly sensitive SERS detection, as demonstrated by the observation of the Raman peaks for TC even at an extremely low concentration of 10^–10 moles per liter. The excellent photocatalytic performance and SERS detection capability of the PI/TiO₂/Ag flexible microfibers arose from the Schottky barrier formed between Ag and TiO₂ and also from the outstanding plasmonic resonance and visible light absorptivity of Ag, along with immobilization by the PI. The successful synthesis of PI/TiO₂/Ag flexible microfibers holds significant promise for sensitive detection and efficient photocatalytic degradation of antibiotics.