A fluorescence sensing compound for separately detecting and visualizing one or more monoamine neurotransmitters in cells, the fluorescence sensing compound having the following formula: wherein R1 and R2 are each independently selected from the group consisting of hydrogen, alkyl, alkylene, aryl, cycloalkyl; wherein R3 is selected from the group consisting of hydrogen, alkyl, alkylene, aryl, cycloalkyl, cyano, azido; and wherein R4 is selected from the group consisting of (CH3)2Si, O, N, S, and CH2.