Engineered CeO₂@Ru Nanospheres via Size‐Metal‐Loading Synergy to Enhance Chemiluminescence Efficiency for Sensitive Immunochromatographic Assay

Abstract Exploring chemiluminescence‐based immunochromatographic assay (CLICA) is favorable for sensitive point‐of‐care testing, yet inefficient CL efficiency (Φ_CL) and poor visualization hinder the progress of CLICA. Herein, CeO₂@Ru nanospheres (CeO₂@RuNSs) are engineered through a “Size‐Metal‐Loading” synergistic tactic to significantly enhance Φ_CL in luminol‐H₂O₂‐based CLICA for sensitive ochratoxin A (OTA) detection. As the core of the sensor, the structure‐Φ_CL relationship of CeO₂@RuNSs is systematically explored through size regulation, metal deposition, and loading optimization. Systematic studies reveal that large‐sized CeO₂ exhibits superior peroxidase‐like activity among three particle sizes, and subsequent Ru doping coupled with loading regulation synergistically boost catalytic performance, achieving an 8.3‐fold higher Φ_CL (10.59×10⁻³ einsteins/mol) compared to small‐sized CeO₂. Furthermore, the CeO₂@RuNSs‐labeled antibodies serve as probes to construct CLICA with preeminent intensity, while the CL system components are carefully optimized for effective visualization. Impressively, a portable detection device is designed by the integration of CeO₂@RuNSs‐CLICA with a smartphone‐based readout. After optimization, the detection limit of this CLICA can reach as low as 0.06 ng mL⁻¹, which is much lower than that of traditional gold nanoparticle‐based ICA (0.23 ng mL⁻¹), with admirable specificity and reproducibility. Ultimately, the sensor performs well in wheat and barley samples with satisfactory recovery rates (92.1%–114.9%).