Life systems can utilize energy with a high efficiency. Biophotons were proposed to modulate biological functions with such efficiency, however the underlying mechanism remains unexplored, especially due to the challenge in ultraweak mid-infrared (MIR) light detection and the theoretical perturbation from spontaneous MIR emission. Here, we proposed an optimized system to detect MIR biophotons generated in the hydrolysis of deoxynucleotide triphosphate (dNTP, an energy-storing molecule similar to ATP). The system used quantitative polymerase chain reaction (qPCR) that was modulated by gold nanoparticle (AuNP) concentration and thus by the inter-AuNP distance which depends on the concentration above. The measurements indicate that 33-THz and 84-THz photons are released by dNTP hydrolyses, which can drive DNA replication. Our findings provide a chain reaction-based novel method for detecting MIR photons in solution, and a pave way for photon-based insights to understand the high-efficiency energy utilization of biology.