Two types of water-soluble multicolor carbon dots(CDs) were prepared through the reactions of egg white or milk with glucose by hydrothermal method.The CDs derived from egg white/glucose(E-CDs) and milk/glucose(M-CDs) were purified by filtering membrane and column chromatography.Particle sizes,UV-vis absorption and emission spectra and surface groups of the two types of CDs were characterized using transmission electron microscopy(TEM),ultraviolet spectrometry(UV),fluorescence spectroscopy(FL),Fourier transform infrared spectroscopy(FTIR) techniques,and their multicolor cell imaging were evaluated by incubation with mouse melanoma cells.The results showed that the two types of multicolor CDs prepared by hydrothermal method were highly water-soluble with particles sizes of 2.5 nm and 4.9 nm,respectively,which could emit bright multicolor fluorescence under the excitation of UV-vis light.Their maximum absorption wavelength was 250 nm,whereas the maximum fluorescence emission wavelengths were located at 410 nm and 400 nm for E-CDs and M-CDs,respectively.Meanwhile,the obtained CDs exhibited upconversion fluorescence properties in the excitation wavelength range of 660- 800 nm.The emission peak positions from both CDs shifted to longer wavelengths,and the intensity gradually decreased with the increase of excitation wavelengths.FTIR spectra analysis revealed the presence of —COOH,—NH2 and —OH on both of CDs’ surface.Cell imaging results demonstrated that fluorescence in the cells cultured with CDs was clearly visible under 405 nm and 488 nm laser irradiation,respectively,and both of the CDs showed very low cytotoxicity when the CDs’ concentration was less than 2.5 mg/mL.