Granulated sugar, soft sugar and crystal sugar purchased from supermarket were used in the sample analysis. Sample solution was prepared by dissolving 5.0 g of sugar in deionized water and diluting to 10 mL.Aliquots ofthe sugar solution were added directly to the PBS buffer (pH = 7.4, 10 mM) containing 1 (10 M), and the emission intensity at 465 nm were recorded.