Which substance generates the light signal in electrochemiluminescence?

In electrochemiluminescence, the substance that generates the light signal is ruthenium. This metal complex plays a crucial role in the detection mechanisms used in various analytical techniques, particularly in immunoassays and biosensors. When an electric potential is applied to the ruthenium complex, it undergoes an electrochemical reaction, leading to the generation of excited states that emit light upon returning to the ground state. This property makes ruthenium valuable for sensitive detection, as the emitted light can be quantitatively measured to determine the concentration of analytes.

Other substances listed have distinct properties and applications but do not serve as the primary light-generating species in electrochemiluminescence. For instance, acridinium is typically used in chemiluminescence, while luminol is known for its reactions in chemiluminescence and fluorescence but not specifically in the electrochemiluminescence context. Dioxetane phosphate is often associated with chemiluminescent reactions in enzyme assays, but it doesn't participate in the electrochemical generation of light as ruthenium does. Thus, in the specific context of electrochemiluminescence, ruthenium stands out as the correct answer due to its unique electrochemical