Fluorescent probe, preparation method therefor and use thereof

A fluorescent probe, the fluorescent probe is a compound having a structure represented by formula (I-a) or (I-b), or a salt thereof,

• wherein,
• A is a structure of the following formula:
• X—CH2—CH2--
• wherein, X is chlorine;
• in formula (I-a), B is
• in formula (I-b), B is
• D is —NX1—X2, wherein in formula (I-a), D is —NX1(X2), wherein, X1 and X2 is independently selected from hydrogen, an alkyl group, or
• in formula (I-b), D is —X2—NX1, wherein, X1 is selected from hydrogen, an alkyl group,
• X2 is
• E is selected from structures of the following:
• in formula (I-b),
• is one selected from the following formulae (I-2-1) to (I-2-28):
• in formula (I-a),
• is one selected from the following formulae (I-2-29) to (I-2-38):
• wherein the “alkyl” in formula (I-a) or formula (I-b) is a C1-C10 linear or branched alkyl.