It was found that API can form diazo salt with nitrite in acidic medium and then it would form hydroxydiazene in alkaline medium, leading the significant increase in the fluorescence.

• 发现API在酸性介质中与亚硝酸根生成重氮盐化合物，进一步在碱性介质中生成相应的羟基二氮烯，使荧光强度明显增强。