Premium
Probing the phase transition behavior of acetonitrile confined in mesoporous silica by FT Raman spectroscopy
Author(s) -
Li Dongxu,
Huang Yining
Publication year - 2011
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2866
Subject(s) - acetonitrile , raman spectroscopy , mesoporous material , mesoporous silica , materials science , phase transition , nanopore , phase (matter) , analytical chemistry (journal) , spectroscopy , chemical engineering , chemistry , nanotechnology , chromatography , organic chemistry , thermodynamics , catalysis , optics , physics , engineering , quantum mechanics
Phase transitions of acetonitrile confined in mesoporous silica SBA‐15 and mesocellular silica foam (MCF) having different pore diameters of 39.0, 39.9, 28.4, 8.7, and 4.6 nm with corresponding pore openings of 20.9, 12.1, 10.0, 8.7, and 4.6 nm were investigated by FT Raman spectroscopy. Melting and freezing temperature depressions were found for acetonitrile confined in mesoporous silica with pore opening sizes of 20.9, 12.1, 10.0 and 8.7 nm. A thermal hysteresis between the cooling and heating cycles was also observed. It appears that the smaller the pore opening, the larger the depression of melting or freezing temperature. Although two solid ( ${\bf \alpha}$ and ${\bf \beta}$ ) phases exist in bulk acetonitrile, only the liquid →β phase transition was detected for acetonitrile confined in the nanopores of mesoporous silica. The ${\bf \beta} \rightarrow {\bf \alpha}$ solid‐to‐solid phase transition was not observed. For the mesoporous silica with the smallest pore size of 4.6 nm, neither the liquid $\rightarrow {\bf \beta}$ nor the ${\bf \beta} \rightarrow {\bf \alpha}$ transition was observed for the confined acetonitrile. The results demonstrate that FT Raman spectroscopy is a useful technique for studying the phase transition behavior of organic compounds confined in silica‐based hosts. Copyright © 2011 John Wiley & Sons, Ltd.