The invention discloses fluorescent 
viologen derivatives, application and a preparation method thereof. A series of novel 
viologen derivatives with fast and visual 
solvent recognition and fast and sensitive color-
change detection for the pH value at the alkaline range, the temperature and alkaline gases such as NH3 are prepared by utilizing a solvothermal method. Simultaneously, the series of fluorescent 
viologen derivatives are simple in synthesis method, high in yield, low in cost and strong in 
fluorescence. A viologen electrochromic device is good in color-change property and 
cyclic stability, low in color-change 
voltage, fast in color change and convenient in 
assembly. The fluorescent viologen derivatives can display the distinguished colors and the 
fluorescence emitting change in different organic solvents, so that the effect of detecting and distinguishing the organic solvents is achieved; after the novel viologen is used for preparing into test paper for detection, the detectioncapability in a 
solution state is retained, and the test paper can display different 
color changes so as to achieve the effect of sensing detection and recognition. The test of the viologen electrochromic device shows that the fluorescent viologen derivatives have good potential application value in the fields of electrochromic glass and displays and the like.