Understanding the water structures by near‐infrared and Raman spectroscopy

Abstract The structure of water in different systems has been extensively studied due to the complexity and flexibility of the hydrogen‐bonded network and the important role in chemical and biological processes. Near‐infrared (NIR) and Raman spectroscopy has been used to investigate the structures of water and the interactions in aqueous systems. In this review, works for structural analysis of water by NIR and Raman spectroscopy were summarized. From resolution‐enhanced spectra, the spectral components of water were obtained. The spectral features correspond to the structures of water with different hydrogen bonds and the interactions of water and solutes. Following the concept of aquaphotomics, the changes of the spectral pattern of water with different perturbations, such as the variation of composition and temperature, were studied. The spectral pattern was found to be related to the analytes in the analyzing system and can be used to reflect the properties of the solutes and even disease diagnosis. Furthermore, water structures in the conformational change of macromolecules such as proteins and polymers were analyzed. Water was proved to be an indicator of the changes, and the water structures with two or three hydrogen bonds (S 2 or S 3 ) were found to have an important role in the phase transition of the proteins and polymers.