A novel optical nanoprobe based on silicon quantum dots (SiQDs) has been assembled through a one-pot low-temperature (40 degrees C) treatment by using 3-(aminopropyl)-trimethoxysilane (APTMS) and ascorbic acid (AA) as two precursors. The water-soluble SiQDs demonstrate intense green luminescence in aqueous environment and the excitation-dependent feature has been explored. Meanwhile, the incorporation of salicylaldehyde (SA) serves to suppress the emission of SiQDs effectively via nucleophilic reaction and an HN SA "on-off" change is observed. Furthermore, the addition of Zn2+. can lead to evolution of emission peaks, and the green band at SOO nm gradually shifts toward the blue side at 455 nm. The corresponding ratiometric signal changes (I-455/I-500) can accurately determine the Zn2+ concentration and the limit of detection is calculated to be 0.17 mu M in the linear range between 1 and 100 mu M. In this research, a molecular logic gate (AND) system has been well established by using SA and Zn2+ as two inputs. The fluorescence emission changes based on SiQDs will shed new light on the development of functional sensors at the nanoscale level.