摘要： Low-toxicity gold nanoclusters-decorated Ag@SiO2 (Au NCs-Ag@SiO2) nanocomposites modified plasmonic photoelectrodes were firstly fabricated to improve the photoelectric properties of Au NCs and practical application in biological detection. Through adjusting distance between Au NCs and plasmonic silver nanoparticles (Ag NPs), the photocurrent intensity of Au NCs enhanced by 3.8 times attributed to strong competition between enhancement functions of hot electron transfer, local electric field, light scattering effects and quenching functions of nonradiative energy transfer. Further comparison between experimental results and theoretical simulations were conducted to gain a deeper understanding toward the photoelectric enhancement mechanism. Moreover, Au NCs-Ag@SiO2 nanocomposites was successfully applied to the construction of photoelectrochemical (PEC) biosensors for sensitively detecting alkaline phosphatase activity. This proposed PEC biosensor showed a wide linear range from 0.04 to 400 U·L-1, and a low detection limit of 0.022 U·L-1.