1. A stilbazolium derivative of formula (I):
wherein R1, R2, R3, and R4 independently represent hydrogen, halogen, unsubstituted or substituted alkyl, hydroxyl, carboxyl, or amino;
R5 represents hydrogen or unsubstituted or substituted alkyl;
X represents oxygen or NR6 (R6 is hydrogen or unsubstituted or substituted alkyl);
Y? represents an anion selected from the group consisting of sulfonic acid anions, carboxylic acid anions, hydrogen sulfate
ions, nitrate ions, tetrafluoroborate ions, perchlorate ions, perbromate ions, and periodate ions; and
in the general formula (I), some or all of hydrogens maybe deuterium wherein said substituted alkyl has a substituent selected
from the group consisting of halogen, hydroxyl, ether, carboxyl, nitro, amino, and sulfone.