## 3 Discussion  
The relationship between the surface tension and the mole ratio were shown in Figure 1. The surface tension of the solutions decreases significantly with the increase of amount of acetone. Interestingly, the reduction of surface tension becomes obvious until the molar ratio is about 1:1. However, the surface tension decreases gentleylor the gradient of tension changes is small as the molar ratio is greater than 1:1. It was found that the changes on surface tension of the solutions were affected by two pure solutions, which are directly conductive to the content of it. As shown in Figure 1, the two pure solutions-dominated regions exhibitwhile it is near the two pure solutions. Meanwhile, the surface tension of the solutions does not vary linearly with the molar ratios of the two solutions, and there showed the great difference of trend at the scale of molar ratio. It can be concluded that the change of surface tension is affected by the microscopic interaction. Otherwise, maybe it was limited by the changes of microstructure of mixture solutions. Figures 2 and 3 show the Raman spectra of C=O bond and OH bond stretching vibration in different molar ratio acetone aqueous solutions at normal temperature, respectively. In order to understand the interaction and microstructure changes in the mixed solutions, the Raman spectra of different solutions were measured, and the trend of the Raman peaks of the C=O stretching bond and the OH bond in solutions with different molar ratios was obtained. Apparently with the addition of acetone, the stretching vibration peak of the C=O bond moves toward the high wavenumber. It is confirmed that hydrogen bond is formed between the O atom in acetone and the H atom of OH in H\({}_{2}\)O. In the range of low concentration which is less than 1:1 for the molar ratio, the vibration peak moves toward a high wavenumber with the addition of acetone, indicating that the number of hydrogen bonds in the solutions increases and the hydrogen bonding is strengthened, which promotes the long elongation of the C=O bond. At the same time, the vibration force constant becomes small. The molecular structure in pure water is divided into three categories: free water molecule, partially hydrogen-bonded water structure in which hydrogen bond with one or more surrounding molecules was formed, and a tetrahedral hydrogen-bonded structure in which hydrogen bonding with one and three surrounding water molecules are connected [28,29]. The vibrational band of the OH bond is considered as the characteristic band of H\({}_{2}\)O. As shown in Figure 3, the shoulder peak near 3240 cm\({}^{-1}\) is identified as the Raman spectrum peak of the fully hydrogen-bonded tetrahedral structure water in the solutions, and the peaks around 3420 cm\({}^{-1}\) and 3550 cm\({}^{-1}\) are assigned to the Raman peak of the partially hydrogen-bonded structure water. It was revealed that the peak intensity of the fully hydrogen-bonded gradually weakened with the increasing content of acetone in the solutions system. Nevertheless, there was hardly changed in the shift of peak position significantly. In addition, the peak of partially hydrogen-bonded water moves toward high wavenumbers, and the relative peak intensity  
Figure 1: The relationship between surface tension and mole ratio of acetone aqueous solutions. Figure 2: Raman spectra for C=O stretching bond of pure acetone and acetone aqueous solutions with different moral ratios (nCH\({}_{3}\)COCH\({}_{3}\):nH\({}_{2}\)O). a to o respectively correspond to pure acetone, 20:1, 10:1, 9:1, 5:1, 3:1, 3:2, 1:1, 1:2, 1:3, 1:4, 1:5, 1:10, 1:20 and water as a comparison. of the component increase gradually. As a result, due to the content of acetone increases, the hydrogen bonding between acetone and water enforce the broken of fully hydrogen-bonded structure, and the amount of partially hydrogen-bonded structures increase. Besides, the addition of acetone will reduce the polarity of water.