The structure of an intercalated ordered kaolinite — a Raman microscopy study

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 587-596 ◽  
Author(s):  
R. L. Frost ◽  
T. H. Tran ◽  
J. Kristof
Keyword(s):  
Raman Band ◽  
Low Frequency ◽  
Potassium Acetate ◽  
Microscopy Study ◽  
Raman Microscopy ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Inner Surface ◽  
Order Of Magnitude

AbstractChanges in the molecular structure of a highly ordered kaolinite, intercalated with urea and potassium acetate, have been studied using Raman microscopy. A new Raman band, attributed to the inner surface hydroxyl groups strongly hydrogen bound to the acetate, is observed at 3605 cm-1 for the potassium acetate intercalate with the consequential loss of intensity in the bands at 3652, 3670, 3684 and 3693 cm-1. Remarkable changes in intensity of the Raman spectral bands of the low-frequency region of the kaolinite occurred upon intercalation. In particular, the 144 and 935 cm-1 bands increased by an order of magnitude and were found to be polarized. These spectroscopic changes provide evidence for the inner surface hydroxyl group-acetate bond being at an angle approaching 90° to the 001 face. Decreases in intensity of the bands at 243, 271 and 336 cm-1 were observed. The urea intercalate shows additional Raman bands at 3387, 3408 and 3500 cm-1 which are attributed to N-H vibrations after formation of the urea-kaolinite complex. Changes in the spectra of the inserting molecules were also observed.

Kaolinite hydroxyls – a Raman microscopy study

Clay Minerals ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 471-484 ◽  
Author(s):  
R. L. Frost ◽  
S. J. van der Gaast
Keyword(s):  
Hydrogen Bonding ◽  
Domain Size ◽  
Microscopy Study ◽  
Raman Microscopy ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Inner Surface ◽  
Relationship Of ◽  
Spectral Intensities

AbstractRaman microscopy of the kaolinite polymorphs was used to study single crystals and bundles of aligned crystals of kaolinite. The spectra of the hydroxyl stretching region were both sample and orientation dependent. Kaolinites can be classified into two groups according to the ratio of the intensities of the 3685 and 3695 cm−1 bands. No relationship was found between the d-spacing and the crystal domain size measurement from the 001 reflection and the Raman spectral intensities indicating the Raman spectra are independent of d-spacing and crystallinity. However, a relationship of the crystallinity in the a-b direction and intensities of the 3685 and 3695 cm−1 bands indicate that the relative position of one layer to the other determines the position of the inner surface hydroxyl groups and the hydrogen bonding with the oxygen of the opposite layer. A new hypothesis based on symmetric and non-symmetric hydrogen bonding of the inner surface hydroxyl groups is proposed to explain the two inner surface hydroxyl bands centred at 3685 and 3695 cm−1. The bands at 3670 and 3650 cm−1 are described in terms of the out-of-phase vibrations of the in-phase vibrations at 3695 and 3685 cm−1.

Biocompatibility and Functional Performance of a Polyethylene Glycol Acid-Grafted Cellulosic Membrane for Hemodialysis

2000 ◽  
Vol 23 (6) ◽  
pp. 356-364 ◽  
Author(s):  
V. Sirolli ◽  
S. Di Stante ◽  
S. Stuard ◽  
L. Di Liberato ◽  
L. Amoroso ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Functional Performance ◽  
Sialyl Lewis X ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Dialysis Session ◽  
Cellulose Diacetate ◽  
Activation Markers ◽  
Surface Hydroxyl ◽  
Cellular Expression

In order to improve the biochemical reactivity of the cellulose polymer, which is mainly attributed to the presence of surface hydroxyl groups, derivatized cellulosic membranes have been engineered replacing or masking some or all of the hydroxyl groups in the manufacturing process of the membrane. The present study was set up to analyze both biocompatibility and functional performance of two different derivatized cellulosic membranes (cellulose diacetate; polyethylene glycol, PEG, acid-grafted cellulose) as compared to a synthetic membrane (polymethylmethacrylate, PMMA). Cellulose diacetate is prepared by substituting hydroxyl groups with acetyl groups; PEG cellulose is obtained by grafting PEG chains onto the cellulosic polymer with a smaller amount of substitution than cellulose diacetate. While the three dialyzers provided similar urea and creatinine removal, the dialyzer containing cellulose diacetate showed a reduced ability to remove β2-microglobulin compared to that containing PEG cellulose or PMMA. A transient reduction in leukocyte count was observed for both derivatized cellulosic membranes. The neutrophil and monocyte counts throughout the entire dialysis session showed a closer parallelism with the cellular expression of the adhesive receptor CD15s (sialyl-Lewis x molecole) than with CD11b/CD18 expression. Platelet activation, as indicated by the percentage of cells expressing the activation markers CD62P (P-selectin) and CD63 (gp53), occurred with all membranes at 15 min of dialysis and also with PMMA at 30 min. An increased formation of platelet-neutrophil and platelet-monocyte coaggregates was found at 15 and 30 min during dialysis with cellulose diacetate and PMMA but not with PEG cellulose. Generally in concomitance with the increase in platelet-neutrophil coaggregates, an increased hydrogen peroxide production by neutrophils occurred. Our results indicate that derivatizing cellulose may represent a useful approach to improve the biocompatibility of the cellulose polymer, though some homeostatic reactions remain activated. Our results also indicate that there may be a great variability in the biocompatibility profile of derivatized cellulosic membranes which most likely stem from the different type of structural modification rather than from the degree of hydroxyl group replacement.

Kaolinite hydroxyls in dimethylsulphoxide-intercalated kaolinites at 77 K – a Raman spectroscopic study

Clay Minerals ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 443-454 ◽  
Author(s):  
R. L. Frost ◽  
J. Kristof ◽  
E. Horvath ◽  
J. T. Kloprogge
Keyword(s):  
Raman Spectroscopy ◽  
Spectroscopic Study ◽  
Dmso Molecule ◽  
Molecular Forms ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Raman Spectroscopic ◽  
Raman Spectroscopic Study ◽  
Surface Hydroxyl Groups ◽  
Inner Surface

AbstractKaolinite hydroxyls in dimethylsulphoxide-intercalated (DMSO-intercalated) kaolinites have been determined using Raman spectroscopy at 298 and 77 K. The inner surface hydroxyl frequencies at 3650, 3670, 3684 and 3693 cm-1 move to higher wavenumbers upon cooling to 77 K and are observed at 3659, 3676, 3692 and 3702 cm-1. The inner hydroxyl frequency is at 3620 cm-1 at 298 K and is at 3615 cm-1 at 77 K. Upon intercalation with DMSO, additional bands are found at 3660, 3536 and 3501 cm-1 for the low-defect kaolinite and at 3664, 3543 and 3509 cm-1 for the high-defect kaolinite at 298 K. The 3660 cm-1 band at 298 K is resolved into two bands at 3658 and 3663 cm-1 at 77 K for the low-defect kaolinite and these bands are assigned to the inner surface hydroxyl groups, hydrogen-bonded to the DMSO molecule. It is proposed that the DMSO molecule exists with two different orientations in the intercalate and these two molecular forms are differentiated by the OH-stretching bands of the inner surface hydroxyl groups. This band for the high-defect kaolinite is found at 3664 cm-1 at 298 K and resolves into two bands at 3664 and 3673 cm-1 at 77 K.

AN INFRARED STUDY OF THE ADSORPTION OF AMMONIA ON POROUS VYCOR GLASS

1964 ◽  
Vol 42 (4) ◽  
pp. 802-809 ◽  
Author(s):  
N. W. Cant ◽  
L. H. Little
Keyword(s):  
Hydrogen Exchange ◽  
Lone Pair ◽  
Acid Sites ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Infrared Study ◽  
Vycor Glass ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Adsorption Sites

The infrared spectrum of ammonia adsorbed on porous glass at 20 °C and 150 °C has been studied in the region 1450–4000 cm−1. No absorption band due to the asymmetric bending mode of ammonia was observed but in the NH stretching region, bands occurred at 3280 cm−1, 3320 cm−1, 3365 cm−1, and 3400 cm−1. The bands at 3320 cm−1 and 3400 cm−1 were easily removed by evacuation and are due to ammonia molecules hydrogen bonded through the nitrogen atom to surface hydroxyl groups. The bands at 3280 cm−1 and 3365 cm−1 were not removed by evacuation even at 150 °C and are due to ammonia molecules held to surface Lewis acid sites by the nitrogen lone-pair electrons. The site for this adsorption is not a surface hydroxyl group. These results are further evidence for the existence of the two adsorption sites proposed by Folman and Yates. Deuteration of the surface OH groups was easily accomplished with D2O vapor at 300 °C and the rate of hydrogen exchange between adsorbed ammonia molecules and surface OD groups was found to be rapid.

scholarly journals The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1988
Author(s):  
Davide Barreca ◽  
Ettore Fois ◽  
Alberto Gasparotto ◽  
Chiara Maccato ◽  
Mario Oriani ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Density Functional ◽  
Chemical Vapor ◽  
Molecular Geometry ◽  
Ab Initio Molecular Dynamics ◽  
Growth Surface ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Order Of Magnitude

Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond dissociation mechanism on the growth surface is not yet clarified in detail. We address this question by density functional theory (DFT) and ab initio molecular dynamics (AIMD) in combination with the Blue Moon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine), an amenable precursor for the CVD of ZnO nanosystems, show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of magnitude of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyl groups plays a key role in aiding the dissociation of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures.

Chemical Stability of 2D-Nanostructured WO3 in Hydrogen Sensing Under Varied Operation Temperature

NANO ◽  
2016 ◽  
Vol 11 (08) ◽  
pp. 1650092 ◽  
Author(s):  
Taisheng Yang ◽  
Hui Tian ◽  
Yue Zhang ◽  
Chen Li
Keyword(s):  
Water Molecule ◽  
Chemical Stability ◽  
Density Functional ◽  
Stable State ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Hydrogen Sensing ◽  
Operation Temperature ◽  
Surface Hydroxyl Groups

Nanostructured metal oxide-based resistive-type gas sensors are of high research interest. Chemical stability is the most critical issue due to the surface electron species and density. In the present paper, 2D-nanostructured WO3 was prepared and characterized, and a WO3-based sensor was fabricated and analyzed. The results showed that the synthesized WO3 material exhibited nanosheet structure, and during hydrogen sensing testing, the current baseline shifted with various tendencies, even completely opposite directions under different operation temperatures. The chemistry analysis results indicated that water molecule and hydroxyl group were formed under low operation temperature but further oxidation occurred at higher temperatures. The adsorption of H2 on oxygen terminated WO3(0 0 1) surfaces by density functional theory (DFT) method indicated that a water molecule formed by adsorption of a hydrogen molecule at the O site with the most thermodynamically stable state, and two surface hydroxyl groups formed by dissociative adsorption with a thermodynamically less stable state. The water molecule and surface hydroxyl groups increased the conductivity of the WO3 film while that was decreased as the oxidation occurred.

Hydroxyl Stretching Bands in Micas: A Quantitative Interpretation

Clay Minerals ◽  
1970 ◽  
Vol 8 (4) ◽  
pp. 375-388 ◽  
Author(s):  
Paul G. Rouxhet
Keyword(s):  
Chemical Composition ◽  
Absorption Coefficient ◽  
Frequency Band ◽  
Low Frequency ◽  
Orientation Distribution ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Quantitative Interpretation ◽  
Oh Content

AbstractMethods are described for estimating a valuable absorption coefficient for OH stretching bands of micas: the integrated parallel absorption coefficient K.From a correlation between this coefficient and the OH content of biotites and phlogopites, it was found that the parallel absorption coefficient per hydroxyl group in these trioctahedral micas is not appreciably influenced by the chemical composition and the direction of the OH bond. A clear deviation was observed for the low frequency band of a biotite characterized by a well-ordered orientation distribution for the corresponding hydroxyl groups.The integrated parallel absorption coefficient of muscovite is proportionally 2·5 to 3 times larger than that of trioctahedral micas.

Raman Spectroscopy of the Kaolinite Hydroxyls at 77 K

1998 ◽  
Vol 52 (10) ◽  
pp. 1277-1282 ◽  
Author(s):  
Ursula Johansson ◽  
Ray L. Frost ◽  
Willis Forsling ◽  
J. Theo Kloprogge
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Low Temperature ◽  
Liquid Nitrogen Temperature ◽  
Hydroxyl Groups ◽  
Frequency Shifts ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Inner Surface ◽  
Raman Microprobe

Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the inner hydroxyl and the inner surface hydroxyl groups. The inner hydroxyl frequency is reduced, and the outer hydroxyl frequencies move to higher frequencies upon cooling to 77 K. The inner hydroxyl frequency shifts from 3620 cm−1 at 298 K to 3615 cm−1 at 77 K. The two in-phase inner surface hydroxyl frequencies move from 3684 and 3689 cm−1 at 298 K to 3690 and 3699 cm−1 at 77 K. The two out-of-phase vibrations shift from 3650 and 3668 cm−1 to 3656 and 3675 cm−1. The bandwidth of the inner hydroxyl frequency decreases from 3.7 to 2.1 cm−1 at 77 K. The bandwidth of the inner surface hydroxyl frequency ( v1) increases upon cooling from 17.4 to 19.2 cm−1. It is proposed that the increased resolution at low temperature enabled an additional inner surface hydroxyl frequency to be observed.

scholarly journals Tailoring the component of protein corona via simple chemistry

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiang Lu ◽  
Peipei Xu ◽  
Hong-Ming Ding ◽  
You-Sheng Yu ◽  
Da Huo ◽  
...  
Keyword(s):  
Surface Properties ◽  
Blood Circulation ◽  
Molecular Simulations ◽  
Protein Corona ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
In Vitro Measurements

Abstract Control over the protein corona of nanomaterials allows them to function better. Here, by taking graphene/gold as examples, we comprehensively assessed the association of surface properties with the protein corona. As revealed by in vitro measurements and computations, the interaction between graphene/gold and HSA/IgE was inversely correlated with the hydroxyl group availability, whereas the interaction between that and ApoE was comparatively less relevant. Molecular simulations revealed that the number and the distribution of surface hydroxyl groups could regulate the manner in which nanomaterials interact with proteins. Moreover, we validated that ApoE pre-adsorption before injection enhances the blood circulation of nanomaterials relative to their pristine and IgE-coated counterparts. This benefit can be attributed to the invulnerability of the complementary system provided by ApoE, whose encasement does not increase cytotoxicity. Overall, this study offers a robust yet simple way to create protein corona enriched in dysopsonins to realize better delivery efficacy.

scholarly journals Defluoridation performance comparison of aluminum hydroxides with different crystalline phases

2022 ◽  
Author(s):  
Wei-Zhuo Gai ◽  
Shi-Hu Zhang ◽  
Yang Yang ◽  
Kexi Sun ◽  
Hong Jia ◽  
...  
Keyword(s):  
Aluminum Hydroxide ◽  
Performance Comparison ◽  
Hydroxyl Group ◽  
Fluoride Removal ◽  
Hydroxyl Groups ◽  
Order Kinetic ◽  
Crystalline Phases ◽  
Surface Hydroxyl ◽  
Ph Values ◽  
Aluminum Hydroxides

Abstract Aluminum hydroxide is an eye catching and extensively researched adsorbent for fluoride removal and its defluoridation performance is closely related to the preparation method and crystalline phase. In this research, the defluoridation performances of aluminum hydroxides with different crystalline phases are compared and evaluated in terms of fluoride removal capacity, sensitivity to pH values and residual Al contents after defluoridation. It is found that the defluoridation performance of different aluminum hydroxides follows the order of boehmite > bayerite > gibbsite. The fluoride adsorption on aluminum hydroxides follows pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum defluoridation capacities of boehmite, bayerite and gibbsite are 42.08, 2.97 and 2.74 mg m−2, respectively. The pH values and FTIR analyses reveal that the ligand exchange between fluoride and surface hydroxyl groups is the fluoride removal mechanism. Different aluminum hydroxides have different surface hydroxyl group densities, which results in the different defluoridation capacities. This work provides a new idea to prepare aluminum hydroxide with outstanding defluoridation performance.

Sign in / Sign up

Export Citation Format

Share Document