The development of advanced optical probes for point-of-care testing holds great importance in the field of diagnostic technologies. This study focused on the synthesis of a probe featuring both fluorescent and photothermal responses with single excitation wavelength, which was achieved through the combination of oxidized camellia oleifera shell powder (OC) and Prussian blue nanoparticles (PBNPs). Notably, OC derived from the direct processing of raw material showed fluorescent and phosphorescent emissions simultaneously, and the positions of the two peaks overlapped with the absorbance range of PBNPs, making the fluorescent and phosphorescent emissions of OC effectively quenched by PBNPs. Meanwhile, the photothermal property of PBNPs was activated by the phosphorescent emission of OC through photoinduced energy transfer. As a proof of concept, OC@PBNPs was applied in the dual-channel immunoassay, in which illegal addictive aminopyrine (AP) was chosen as the detection target. Furthermore, a portable device was developed to capture the fluorescent and photothermal signals of OC@PBNPs, rendering the detection method based on OC@PBNPs suitable for point-of-care testing (POCT).