A facile one-step strategy is explored to achieve uniform luminescent Au nanoparticles (AuNPs) in a two-dimensional ultrathin silica matrix based on simultaneous reaction and assembly at the liquid-liquid interface. The as-prepared AuNPs/silica nanocomposites can be further employed to fabricate micrometer-thick films with bifunctional luminescent and superhydrophobic properties. Such a versatile concept is ideal for the development of multifunctional devices.