Intermolecular Interaction of Tetrabutylammonium and Tetrabutylphosphonium Salt Hydrates by Low-Frequency Raman Observation

Abstract

Semi-clathrate hydrates are attractive heat storage materials because the equilibrium temperatures, located above 0 °C in most cases, can be changed by selecting guest cations and anions. The equilibrium temperatures are influenced by the size and hydrophilicity of guest ions, hydration number, crystal structure, and so on. This indicates that intermolecular and/or interionic interaction in the semi-clathrate hydrates may be related to the variation of the equilibrium temperatures. Therefore, intermolecular and/or interionic interaction in semi-clathrate hydrates with quaternary onium salts was directly observed using low-frequency Raman spectroscopy, a type of terahertz spectroscopy. The results show that Raman peak positions were mostly correlated with the equilibrium temperatures: in the semi-clathrate hydrates with higher equilibrium temperatures, Raman peaks around 65 cm−1 appeared at a higher wavenumber and the other Raman peaks at around 200 cm−1 appeared at a lower wavenumber. Low-frequency Raman observation is a valuable tool with which to study the equilibrium temperatures in semi-clathrate hydrates.

Additive engineering by tetrabutylammonium iodide for antimony selenosulfide solar cells

“…The peak at around 216 cm −1 corresponds to the Sb-Se complex vibration, whereas the peaks at 280 and 314 cm −1 are ascribed to Sb-S vibration [18,29]. For comparison, figure 3(c) also includes the typical Raman peak of tetrabutylammonium cations at 261 cm −1 obtained from TBAI precursor powder [30]. Similar to XRD and XPS results, there is no clear evidence of Raman peaks corresponding to the presence of TBAI in the thermally treated Sb 2 (S,Se) 3 film, whereas in the as-deposited Sb 2 (S,Se) 3 film before annealing shows the main peak of TBAI (figure S6).…”

Aquaphotomics—Exploring Water Molecular Systems in Nature

“…Out of the 21 published articles, 3 were reviews [ 2 , 3 , 4 ] and 18 were original research papers [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], that can be roughly separated into 6 categories ( Figure 3 ).…”

“…The majority of the articles, approximately one third, belongs to the field of applications in agriculture and food science [ 8 , 9 , 12 , 13 , 14 , 21 , 22 ], a field from which aquaphotomics originated, and probably the reason why this category is still at the forefront of aquaphotomics development. Following this category are the preprocessing and chemometrics [ 2 , 4 , 15 , 18 ] and fundamental studies [ 5 , 6 , 10 , 17 ]. The former category reflects an important issue that aquaphotomics is trying to resolve, namely, the necessity of developing appropriate tools for dealing with the spectra of highly aqueous samples, and that significant efforts are being invested in resolving the issues of extracting the information from very subtle spectral signals.…”

“…It is especially encouraging to witness that the light–water interaction over the whole electromagnetic spectrum is a source of valuable information, as stated in aquaphotomics. One paper reported the results in the mid-infrared region [ 7 ], and two used Raman spectroscopy [ 10 , 17 ]. There were also two papers reporting on the exploration of a newly developed measurement technique that employs GHz sensors [ 20 ], and also perturbation by polarization filters [ 13 ], for the first time in aquaphotomics.…”

“…The study by Miwa et al [ 17 ] used a similar technique: low-frequency Raman spectroscopy (which is a type of Terahertz spectroscopy) to study the phenomena of semi-clathrate hydrates, which are very popular materials with a wide range of applications due to their ability to store heat. The temperature at which they can store heat can be changed depending on the selection of certain guest-ions, and it is influenced by their size, hydrophilicity, crystal structure, and other properties.…”