In recent years, cadmium sulfide (CdS) has been widely investigated due to its excellent photocatalytic performance. However, its practical application in pollutant treatment is limited by its narrow photoresponse range and susceptibility to photocorrosion. Herein, we design a unique four-layer core–shell structure NaYF₄:Yb³⁺,Er³⁺@NaYF₄@CdS@Au (CSNPs@CdS@Au), with an inert NaYF₄ shell coating on NaYF₄:Yb³⁺,Er³⁺ (CNPs) to form NaYF₄:Yb³⁺,Er³⁺@NaYF₄ (CSNPs) and CdS depositing on CSNPs (CSNPs@CdS); Au nanoparticles are loaded on CdS (CSNPs@CdS@Au). Compared with CdS (9.81%), CSNPs (5.0%), CSNPs/CdS (6.9%), and CSNPs@CdS (81.0%), CSNPs@CdS@Au degrades 97.7% Rhodamine B (RhB) within 15 min, exhibiting superior photocatalytic performance, attributable to two key factors: (1) the NaYF₄ inert shell encapsulation amplifies upconversion (UC) luminescence intensity by suppressing surface quenching; and (2) the electron transfer between Au nanoparticles and CdS effectively promotes spatial separation of photogenerated charge carriers and increases reactive active sites. Additionally, after five degradation cycles, CSNPs@CdS@Au still maintains a 93.25% degradation rate for RhB, confirming its excellent stability. This remarkable stability is attributed to the uniquely designed multilayer core–shell architecture, which significantly enhances structural integrity through physical isolation effects. This study establishes a material preparation strategy for efficient photocatalytic pollutant degradation.

Dopamine (DA) is an important catecholamine neurotransmitter in human metabolism that is associated with various critical diseases. Accurate detection of DA is of great significance for the diagnosis of these diseases. Here, we constructed a sensitive electrochemical sensor, S, N co-doped multi-walled carbon nanotubes (MWCNTs-N-S) loaded with Pd nanoparticles (Pd/MWCNTs-N-S). The linear range of the Pd/MWCNTs-N-S sensor is from 0.0001 to 2.0 mM, and the limit of detection (LOD) is 4.37 nM (S/N = 3) for DA detection. The improved detection performance of this sensor is attributed to the optimization of MWCNTs carrier structure and surface properties by N, S co-doping, as well as the significant improvement of electrochemical surface area (ECSA) for the commendable dispersion of Pd nanoparticles (3.79 nm). What is more, the Pd/MWCNTs-N-S sensor also exhibits good reproducibility, stability, and anti-interference ability. Overall, this study presents a straightforward strategy for the potential applications of Pd-based double co-doped MWCNTs sensors.

Dopamine (DA) plays an extremely crucial role in the metabolic processes of the human body. Accurate detection of DA is of great significance for many major diseases. This study reports an innovative synthesis method for composite material in which sulfur (S) and nitrogen (N) are incorporated into multi-walled carbon nanotubes (MWCNTs), and platinum (Pt) nanoparticle sensors (Pt/CNTs-N-S) are loaded for the highly sensitive and selective electrochemical detection of DA. The linear range of this sensor is from 0.0078 to 2 mM, and the limit of detection (LOD) is 0.73 μM (S/N = 3) for DA detection. The outstanding detection performance exhibited by Pt/CNTs-N-S is mainly attributed to the co-doping of N and S, which improves the surface properties of MWCNTs, and the dispersion of Pt nanoparticles (5.22 nm), which significantly increases the electrochemically active surface area (ESCA). In addition, the Pt/CNTs-N-S sensor also exhibits excellent stability and anti-interference performance. Overall, this study provides a simple and practical strategy for the potential application of Pt-based sensors in the detection of DA.