Selenocysteine (Sec) is known as the 21st amino acid that is incorporated into selenoproteins (SePs) and plays vital roles in living systems. Accordingly, development of fluorescent detection method for Sec is of significance. Herein, a readily available fluorescent Sec probe is reported. Although this probe has been reported before for detection of biothiols, the studies in this work show that it can be used for rapid, high selective and sensitive detection of Sec over biothiols and many other analytes with dual colorimetric and fluorescent tu...