Dynamic registration of the absorption spectrum of water in the SiO(2) nanopores in high-frequency range.
The high-frequency region was used to record the absorption spectrum of water in nanoscale pores during vacuum pumping or injection of water. The wide spectral range, which included the vibration overtones, allowed to resolve the structure of the absorption bands with variation of water concentration in the pores of SiO(2). The absorption bands of water clusters in the 4570-5400 cm(-1) range consist of well-resolved sub-bands with interpeak intervals of up to 580 cm(-1). When the pore diameter is decreased from 11.8 to 2.6 nm, the absorption bands of clusters in this frequency range are shifted by 530 cm(-1) in the direction of the water monomer which indicates an increase of hydrogen bond strength in confined water with an increase of the pore diameter. The spectrum recorded during water pumping is extremely variable in time, and the cluster dynamics in large pores (11.8 nm) differs greatly from the dynamics in small pores (2.6 nm). While all types of water clusters are removed from small pores uniformly, in the case of large pores, the water clusters relating to strong hydrogen bonds are removed from the sample at the beginning of the vacuum pumping and the loosely coupled clusters are removed later. The rate of this process is not steady and varies throughout pumping.
Institute of Atmospheric Optics, Academician Zuev Square 1, Tomsk 634021, Russia. sln@asd.iao.ru
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Sinitsa
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Lugovskoy
D058608:Nanopores; D012822:Silicon Dioxide / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods; D014867:Water / Q000737:chemistry*
D014867:Water; D012822:Silicon Dioxide