Provided is a phosphonium compound represented by Formula (I): in Formula (I), R1, R2, and R3 are independently from each other, an alkyl group or an aryl group, the alkyl group is a substituted or unsubstituted, linear or branched alkyl group having 1 to 20 carbon atoms or a substituted or unsubstituted cyclic alkyl group having 5 to 20 carbon atoms, the aryl group is a substituted or unsubstituted aryl group having 6 to 20 carbon atoms; X is a reactive group having a hydrazide group, a halide group, a pseudohalide group, or a thioester group; and Y− is an anion having a total charge of −1, or Y− is absence.