*3.5. The 3D Fluorescence Spectra of the Wolfberry Honey Samples and Syrups*

The 3D fluorescence spectroscopy is a matrix spectrum characterized by excitation wavelength (*Y*-axis), emission wavelength (*X*-axis), and fluorescence intensity (*Z*-axis), which is able to obtain the information of the excitation wavelength and emission wavelength as well as the information of fluorescence intensity. Therefore, 3D fluorescence spectroscopy is also called total luminescence spectra.

The 3D fluorescence spectra of the wolfberry honey, corn syrup, and corn maltose syrup at an excitation wavelength from 200 to 450 nm and an emission wavelength from 260 to 560 nm were obviously different and could easily be distinguished (Figure 4a–c). From the 3D contour map, we can obviously see that there were two peak values at the excitation wavelength of 280 nm and 230 nm and the corresponding emission wavelength at about 340 nm, which indicated the fluorophores might be aromatic amino acids and non-flavonoid phenolic compounds in the honey sample [28,29]. The 3D fluorescence spectra of two different corn syrups were totally different compared with the wolfberry honey sample without significant peak values and peak positions, which is consistent with the results from 280 nm excitation wavelength, and the 3D contour maps can visually distinguish honey from syrups.

**Figure 3.** The fluorescence spectra of the adulterated wolfberry honey. (**a**) The fluorescence spectra of wolfberry honey adulterated with different proportions of corn syrup (0–100%). (**b**) The fluorescence spectra of wolfberry honey adulterated with different proportions of corn maltose syrup (0–100%). (**c**) The fluorescence spectra of wolfberry honey adulterated with different proportions of acacia honey (0–100%). (**d**) The change trends in emission wavelengths and fluorescence intensities of wolfberry honey adulterated with different proportions of syrups and acacia honey (0–100%). GA: wolfberry honey adulterated with different proportions of acacia honey; GH: wolfberry honey adulterated with different proportions of corn syrup; GZ: wolfberry honey adulterated with different proportions of corn maltose syrup.

**Figure 4.** The three-dimensional (3D) fluorescence spectra of the wolfberry honey and syrups. (**a**) The 3D fluorescence spectra of wolfberry honey. (**b**) The 3D fluorescence spectra of corn syrup. (**c**) The 3D fluorescence spectra of corn maltose syrup. (**d**) The 3D fluorescence spectra of acacia honey.

Similarly, it was difficult to distinguish the wolfberry honey from the acacia honey by the 3D fluorescence spectra (Figure 4d), for two kinds of monofloral honey had similar 3D fluorescence spectra with similar two peak values and peak positions. The peak positions and the maximum fluorescence intensities of the wolfberry honey, corn syrup, corn maltose syrup, and acacia honey can be found in Supplementary Table S2.
