Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.saa.2024.124052

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Raman spectra of water and supercooled water were measured in the temperature range of −6 to 18°C with every 2°C step. The obtained spectra were analyzed for the 3750–2850 and 400–100 cm⁻¹ regions by two‐dimensional correlation (2D‐COS) Raman spectroscopy. As previously reported, there are three bands at around 3620, 3420, and 3200 cm⁻¹ in the OH‐stretching region. These bands were assigned to the OH‐stretching modes of dangling (Dang) bonds of water, destructured, and structured water species, respectively. A pair of clear peaks appear in asynchronous 2D‐COS maps in the 3750–2850 cm⁻¹ region of Raman spectra of water developed using the spectra measured in the temperature ranges of −6 to 2°C, 0 to 8°C, and 8 to 18°C, and they are similar to each other, suggesting nonlinear (convex) temperature‐dependent increase and decrease of the two kinds of water species. A power spectrum calculated along the diagonal line in the synchronous spectrum in the −6 to 18°C range has a peak at 3171 cm⁻¹ with a broad shoulder at around 3400 cm⁻¹. These peaks at 3171 and 3400 cm⁻¹ may be assigned to the collective mode and its local mode of structured water, respectively. In the 400–100 cm⁻¹ region, there is a broad feature centered at 185 cm⁻¹ assigned to the intermolecular stretching mode of water molecule. Close inspection of the low‐frequency region by the baseline corrected spectra and the second derivative spectra shows that the broad feature consists of a major band at around 185 cm⁻¹ and a weak shoulder at around 150 cm⁻¹. We have assigned these two peaks at 185 and 150 cm⁻¹ to the structured and destructured water, respectively, based on the results of 2D‐COS and the comparison with the results of multivariate curve resolution‐alternative least squares reported by Hamaguchi et al. A hetero 2D correlation synchronous map between the 3750–3000 and 400–100 cm⁻¹ regions reveals that there is a cross peak between the structured water band at around 3200 cm⁻¹ and the 185 cm⁻¹ band, confirming that the 185 cm⁻¹ band comes from the structured water.

DOI： 10.1002/jrs.6444

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jrs.6444

Publisher：AIP Publishing  

DOI： 10.1063/5.0071893

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21K05013/

Language：English   Publisher：The Japan Society for Analytical Chemistry  

Attenuated total reflectance–far ultraviolet (ATR-FUV) spectra of Li⁺ and polyether ligands, such as glymes and poly (ethylene glycol) (PEG), in solution give information about changes in the electronic states of the ligands. From the ATR-FUV spectra, the coordination numbers between Li⁺ and monoglyme, diglyme, triglyme, and PEG400 were determined to be 4, 5, 6, and 5, respectively. Our results indicate that Li⁺ is coordinated only by the ligands rather than its counter-ions.

DOI： 10.2116/analsci.19c011

DOI： 10.1039/d0cp03865b_references_DOI_Fow4PRZmf8rygqweelJLkFZIpO6

PubMed

CiNii Article

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Other Link： https://link.springer.com/article/10.2116/analsci.19C011/fulltext.html

Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.9b09274

DOI： 10.3175/molsci.14.a0114_references_DOI_JD6ZusM7OHffgvMiPGH0tTpY9ZB

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Event date： 2020 - 2020

Language：Japanese  

FT-NIR spectroscopy has the potential to be an index for the degree of the formation of BICs using the changes in the hydrogen bonding or CH stretching vibration in terminal groups between the materials (reagents such as cellulose and cellobiose, botanical wastes from coffee beans and tealeaves) and various processing conditions of BICs. FT-NIR spectroscopy is a grate method for the BICs analysis because it is able to measure the vibrational spectra without destruction and pre-preparation for the spectroscopic measurement. The other reason why NIR is that this spectroscopy is hard to include noises from some contained materials in BICs. In the other hand, NIR spectra need the statistics analysis called “chemometrics” because these spectra show very broad and overlapped band. Changes of these overlapped bands are easier to interpret than MIR regions because MIR region has larger amount of information from many kinds of vibrations. Results of the chemometrics need the careful consideration for the changes between analytical results and intentionally perturbations because sometimes chemometrics results do not have the chemical meaning. Raman and THz spectroscopy are used to understand the actual chemical changes with perturbations by comparing with the results of statistical analysis.

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