In the present study we explored metal enhanced bioluminescence in luciferase enzymes for the first time. For this purpose a simple and reproducible one pot synthesis of gold–silver alloy nanoparticles was developed. By changing the molar ratio of tri-sodium citrate and silver nitrate we could synthesize spherical Au–Ag colloids of sizes ranging from 10 to 50 nm with a wide range of localized surface plasmon resonance (LSPR) peaks (450–550 nm). The optical tunability of the Au–Ag colloids enabled their effective use in enhancement of bioluminescence in a luminescent bacterium Photobacterium leiognathi and in luciferase enzyme systems from fireflies and bacteria. Enhancement of bioluminescence was 250% for bacterial cells, 95% for bacterial luciferase and 52% for firefly luciferase enzyme. The enhancement may be a result of energy transfer or plasmon induced enhancement. Such an increase can lead to higher sensitivity in detection of bioluminescent signals with potential applications in bio-analysis.

The first report of individual and synergistic roles of alkali metal ions and gold nanoparticles in the enhancement of luminol-Urea–H₂O₂ chemiluminescence. A maximum of 600% increase over control was evident for NaCl in synergy with gold nanoparticles.