Wetting effect on optical sum frequency generation (SFG) spectra of d-glucose, d-fructose, and sucrose

• SFG spectra of dry and wet d-glucose, d-fructose and sucrose were obtained.
• By wetting α-d-glucose changed into α-d-glucose monohydrate in SFG spectra.
• Change of β-d-fructopyranose into other anomers by wetting was detected.
• Assignments of SFG peaks were done for dry sucrose.
• SFG spectra of sucrose did not change by wetting.

We report a sum frequency generation (SFG) spectroscopy study of d-glucose, d-fructose and sucrose in the CH stretching vibration regime. Wetting effect on the SFG spectra was investigated. The SFG spectrum of d-glucose changed from that of α-d-glucose into those of α-d-glucose monohydrate by wetting. The SFG spectra showed evidence of a small change of β-d-fructopyranose into other anomers by wetting. SFG spectra of sucrose did not change by wetting. Assignments of the vibrational peaks in the SFG spectra of the three sugars in the dry and wet states were performed in the CH stretching vibration region near 3000 cm−1.

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