Spectroscopic Studies of Synthetic and Natural Saponites: A Review

Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4−xO10(OH,F)2.nH2O (M = interlayer cation). Both the success of the saponite synthesis and the determination of its applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques, spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponites with focus on the extensive work by one of the authors (JTK). The Infrared (IR) and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a possible crystallization model is provided. Infrared emission spectroscopy has been used to study the thermal changes of saponite in situ including the dehydration and (partial) dehydroxylation up to 750 °C. 27Al and 29Si magic-angle-spinning nuclear magnetic resonance spectroscopy is discussed (as well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray photoelectron spectroscopy provides chemical information as well as some information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.

Структура и динамика решетки тетрагональных германатов R-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- (R=Tb-Lu, Y): ab initio расчет

Within the framework of density functional theory, an ab initio calculation was carried out to study the crystal structure, phonon spectrum and elastic constants of a series of rare-earth germanates, including yttrium germanate R2Ge2O7 (R = Tb-Lu, Y) with tetragonal structure. The frequencies and types of fundamental vibrations as well as the intensities of the IR and Raman modes were determined. The degree of participation of ions in each mode was determined from the analysis of the displacement vectors obtained from the ab initio calculation. The calculations were performed for the first time. The corresponding experimental data for the entire series, with the exception of the IR and Raman spectra of yttrium germanate, are absent. The calculations made it possible to interpret and supplement available in the scientific articles results of measurements of the IR and Raman spectra of yttrium germanate Y2Ge2O7.

Spectroscopic Studies of Synthetic and Natural Saponites: A Review

Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4-xO10(OH,F)2.nH2O (M = interlayer cation). Both the success of the saponite synthesis and the determination of its applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponite with focus on the extensive work by one of the authors (JTK). The IR and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a possible crystallization model is provided. Infrared emission spectroscopy has been used to study the thermal changes of saponite in-situ including the dehydration and (partial) dehydroxylation up to 750˚C. 27Al and 29Si Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy is discussed (as well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray Photoelectron Spectroscopy provides besides chemical information also some information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.

Molecular structure analysis of ascending aorta aneurysm upon atherosclerosis

Background The atherosclerotic ascending aorta could represent a potential source of emboli or could be an indicator of atherosclerosis in general with high mortality. The mechanism of aneurysm formation and atherosclerosis of the ascending aorta at the molecular level has not yet been clarified. To approach the mechanism of ascending aortic lesions and mineralization at a molecular level, we used the non-destructive FT-IR, Raman spectroscopy, SEM and Hypermicroscope. Methods Six ascending aorta biopsies were obtained from patients who underwent aortic valve replacement (AVR) cardiac surgery. CytoViva (einst inc) hyperspectral microscope was used to obtain the images of ascending aorta. The samples were dissolved in hexane on a microscope glass plate. The FT-IR and Raman spectra were recorded with Nicolet 6700 thermoshintific and micro-Raman Reinshaw (785nm, 145 mwatt), respectively. The architecture of ascending aorta biopsies was obtained by using scanning electron microscope (SEM of Fei Co) without any coating. Results FT-IR and Raman spectra showed changes arising from the increasing of lipophilic environment and aggregate formation (Fig. 1). The band at 1744 cm–1 is attributed to aldehyde CHO mode due to oxidation of lipids. The shifts of the bands of the amide I and amide II bands to lower are associated with protein damage, in agreement with SEM data. The bands at about 1170–1000 cm–1 resulted from the C-O-C of advanced glycation products as result of connecting tissues fragmentations and polymerization. The spectroscopic data were analogous with the lesions observed with SEM and hypermicroscopic images. Conclusions The present innovate molecular structure analysis showed that upon ascending aorta aneurysm development an excess of lipophilic aggregate formation and protein lesions, changing the elasticity of the aorta's wall. The released Ca2+ interacted mostly with carbonate-terminal of cellular protein chains accelerated the ascending aorta calcifications. Figure 1. FT-IR and Raman spectra Funding Acknowledgement Type of funding source: None