Photothermal AFM-IR spectroscopy and imaging: Status, challenges, and trends

<div><div>Scattering-mode Scanning Near-Field Optical Microscopy (sSNOM) allows one to obtain absorption spectra in the mid-IR region for samples as small as 20 nm in size. This configuration has made it possible to measure FTIR spectra of the protein complement of membranes. (Amenabar 2013) We now show that mid-IR sSNOM has the sensitivity required to measure spectra of phospholipids in individual bilayers in the spectral range 800 cm-1–1400 cm-1. We have observed the main absorption bands of the dipalmitoylphosphatidylcholine headgroups in this spectral region above noise level. We have also mapped the phosphate absorption band at 1070 cm-1 simultaneously with the AFM topography. We have shown that we could achieve sufficient contrast to discriminate between single and multiple phospholipid bilayers and other structures, such as liposomes. This work opens the way to further research that uses nano-IR spectroscopy to describe the biochemistry of cell membranes and model systems.</div></div><div></div>

Download Full-text

The Nature of Chemisorbed CO2 in Zeolite A

10.26434/chemrxiv.7422815 ◽

2019 ◽

Author(s):

Przemyslaw Rzepka ◽

Zoltán Bacsik ◽

Andrew J. Pell ◽

Niklas Hedin ◽

Aleksander Jaworski

Keyword(s):

Solid State ◽

Ir Spectroscopy ◽

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Surface Coverage ◽

Gas Mixtures ◽

Mas Nmr ◽

Significant Fraction ◽

Zeolite A

Formation of CO32- and HCO3- species without participation of the framework oxygen atoms upon chemisorption of CO2 in zeolite |Na12|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H2O or acid groups. A combined study by solid-state 13C MAS NMR, quantum chemical calculations, and in situ IR spectroscopy showed that the chemisorption mainly occurred by the formation of HCO3-. However, at a low surface coverage of physisorbed and acidic CO2, a significant fraction of the HCO3- was deprotonated and transformed into CO32-. We expect that similar chemisorption of CO2 would occur for low-silica zeolites and other basic silicates of interest for the capture of CO2 from gas mixtures.

Download Full-text

APPLICATION OF IR SPECTROSCOPY IN THE STUDY OF MINERAL OIL

Oil and Gas Studies ◽

10.31660/0445-0108-2017-1-91-95 ◽

2017 ◽

pp. 91-95

Author(s):

E. I. Grushova ◽

A. .. Al Razuqi ◽

E. S. Chaiko ◽

O. A. Miloserdova

Keyword(s):

Ir Spectroscopy ◽

Group Composition ◽

Mineral Oil ◽

Vacuum Distillate ◽

Methyl Tertiary Butyl Ether ◽

Butyl Ether ◽

Tertiary Butyl ◽

Mineral Oils ◽

Modifying Additive

IR spectroscopy investigated structural and group composition of base mineral oils isolated from the vacuum distillate by selective purification of N-methylpyrrolidone and the low temperature dewaxing in the presence of a solvent. The role of the latter was carried out by the systems acetone - toluene, acetone - methyl tertiary butyl ether, methyl ethyl ketone - toluene, acetone - toluene - modifying additive. It was shown that the chemical composition of the group of base oils and slack waxes is defined as the nature of the solvent to the dewaxing, and oils sequence of purification steps.

Download Full-text