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1.
    
Raman spectroscopy has been used to characterise synthetic mixed carbonate and molybdate hydrotalcites of formula Mg6Al2(OH)16((CO3)2−,(MoO4)2−)·4H2O. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features on the basis of the carbonate anion, the molybdate anion, the hydroxyl units and water units. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions are identified: (1) carbonate hydrogen‐bonded to water in the interlayer, (2) carbonate hydrogen‐bonded to the hydrotalcite hydroxyl surface, (3) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite, as it is hydrogen bonded to both the carbonate and the hydroxyl surface. The spectra have been used to assess the contamination of carbonate in an open reaction vessel in the synthesis of a molybdate hydrotalcite of formula Mg6Al2(OH)16((CO3)2−, (MoO4)2−)·4H2O. Bands are assigned to carbonate and molybdate anions in the Raman spectra. Importantly, the synthesis of hydrotalcites from solutions containing molybdate provides a mechanism for the removal of this oxy‐anion. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

2.
    
Hydrotalcites have been synthesised using solutions of three different pH values to assess the effect of pH on the uptake of arsenate and vanadate. The ability of these hydrotalcites to remove vanadate and arsenate from solution has been determined by inductively coupled optical emission spectroscopy. Raman spectroscopy was used to monitor changes in the anionic species for hydrotalcites synthesised at different pH values. The results show a reduction in the concentration of arsenate and vanadate anions that are removed in extremely alkaline solutions. Hydrotalcites containing arsenate and vanadate are stable in solutions up to pH 10. Exposure of these hydrotalcites to higher pH values results in the removal of large percentages of arsenate and vanadate from the hydrotalcite interlayer. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

3.
    
Raman spectroscopy, complemented with infrared spectroscopy, was used to study the uranyl carbonate mineral voglite. The mineral has the formula Ca2Cu2+ [(UO2)(CO3)3](CO3)•6H2O, and bands attributed to these vibrating units are readily identified in the Raman spectrum. Symmetric stretching modes at 836 and 1094 cm−1 are assigned to ν1(UO2)2+ and ν1(CO3)2− units, respectively. The ν3 antisymmetric stretching modes of (UO2)2+ are not observed in the Raman spectrum but may be readily observed in the infrared spectrum at 898 cm−1. The ν3 antisymmetric stretching mode of (CO3)2− is observed in the Raman spectrum at 1369 cm−1 as a low intensity band as is also the ν3(CO3)2− infrared modes at 1362, 1425, 1509 and 1566 cm−1. No ν2(CO3)2− Raman bending modes are observed for voglite. The Raman band at 749 cm−1 and the two infrared bands at 747 and 709 cm−1 are assigned to the ν4(CO3)2− bending modes. U O bond and O H…O bond lengths in the structure of voglite were inferred from the infrared and Raman spectra. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

4.
    
Hydrotalcites of formula Mg6(Al,Fe)2(OH)16(CO3)·4H2O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d‐spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (1) brucite layer OH stretching vibrations, (2) water stretching bands and (3) water strongly hydrogen bonded to the carbonate anion. Multiple (CO3)2− symmetric stretching bands suggest that different types of (CO3)2− exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the two Raman bands at around 3600 cm−1, attributed to Mg OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm−1, indicating that water is strongly hydrogen bonded to both interlayer anions and the brucite‐like surface. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

5.
    
Burkeite formation is important in saline evaporites and in pipe scales. Burkeite is an anhydrous sulphate-carbonate with an apparent variable anion ratio. Such a formula with two oxyanions lends itself to vibrational spectroscopy. Two symmetric sulphate stretching modes are observed, indicating at least at the molecular level the nonequivalence of the sulphate ions in the burkeite structure. The strong Raman band at 1065 cm?1 is assigned to the carbonate symmetric stretching vibration. The series of Raman bands at 622, 635, 645, and 704 cm?1 are assigned to the ν4 sulphate bending modes. The observation of multiple bands supports the concept of a reduction in symmetry of the sulphate anion from T d to C 3v or even C 2v.  相似文献   

6.
    
Raman spectroscopy complemented with infrared (IR) spectroscopy has been used to study the mineral schroeckingerite. The mineral is a multi‐anion mineral and has (UO2)2+, (SO4)2− and (CO3)2− units in its structure, and bands attributed to these vibrating units are readily identified in the Raman spectra. Symmetric stretching modes at 815, 983 and 1092 cm−1 are assigned to (UO2)2+, (SO4)2− and (CO3)2− units, respectively. The antisymmetric stretching modes of (UO2)2+, (SO4)2− are not observed in the Raman spectra but may be readily observed in the IR spectrum at 898 and 1180 cm−1. The antisymmetric stretching mode of (CO3)2− is observed in the Raman spectrum at 1374 cm−1, as is also the ν4 (CO3)2− bending modes at 742 and 707 cm−1. No ν2 (CO3)2− bending modes are observed in the Raman spectrum of schroeckingerite. All the spectroscopic evidence points to a highly ordered structure of this mineral. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

7.
    
Insight into the unique structure of hydrotalcites has been obtained using Raman spectroscopy. Gallium‐containing hydrotalcites of formula Mg4Ga2(CO3)(OH)12· 4H2O (2:1 Ga‐HT) to Mg8Ga2(CO3)(OH)20· 4H2O (4:1 Ga‐HT) have been successfully synthesized and characterized by X‐ray diffraction and Raman spectroscopy. The d(003) spacing varied from 7.83 Å for the 2:1 hydrotalcite to 8.15 Å for the 3:1 gallium‐containing hydrotalcite. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized gallium‐containing hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O. Raman bands observed at around 1046, 1048 and 1058 cm−1 are attributed to the symmetric stretching modes of the CO32− units. Multiple ν3 CO32− antisymmetric stretching modes are found at around 1346, 1378, 1446, 1464 and 1494 cm−1. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

8.
    
Various barium strontium titanate borosilicate glasses were prepared by a rapid melt-quench technique. Spectroscopic studies have been carried out on investigated glasses for their structural information. Infrared and Raman spectroscopic studies showed that these glasses are formed by glass-forming network of borate and silicate as well as network modifiers in the form of cations of alkaline earth atoms. The borate and silicate networks are modified by barium, strontium, titanium, and iron cations in glass matrix. The network of triborate unit is modified in tetraborate unit by adding ferric oxide in a glassy matrix. The optical studies are performed by ultraviolet-visible spectroscopy and it confirms that the band gap decreases with increase in the concentration of ferric oxide.  相似文献   

9.
ABSTRACT

The adsorption of benzoic acid on both sodium and calcium montmorillonites has been studied by near infrared spectroscopy complimented with infrared spectroscopy. Upon adsorption of benzoic acid, additional near-infrared bands are observed at 8665 cm?1 and assigned to an interaction of benzoic acid with the water of hydration. Upon adsorption of the benzoic acid on Na-Mt, the NIR bands are now observed at 5877, 5951, 6028, and 6128 cm?1 and are assigned to the overtone and combination bands of the CH fundamentals. Additional bands at 4074, 4205, 4654, and 4678 cm?1 are attributed to CH combination bands resulting from the adsorption of the benzoic acid. Benzoic acid is used as a model molecule for adsorption studies. The application of near-infrared spectroscopy to the study of adsorption has the potential for the removal of acids from polluted aqueous systems.  相似文献   

10.
    
Raman spectra of brandholzite Mg[Sb2(OH)12]·6H2O were studied, complemented with infrared spectra, and related to the structure of the mineral. An intense Raman sharp band at 618 cm−1 is attributed to the SbO symmetric stretching mode. The low‐intensity band at 730 cm−1 is ascribed to the SbO antisymmetric stretching vibration. Low‐intensity Raman bands were found at 503, 526 and 578 cm−1. Corresponding infrared bands were observed at 527, 600, 637, 693, 741 and 788 cm−1. Four Raman bands observed at 1043, 1092, 1160 and 1189 cm−1 and eight infrared bands at 963, 1027, 1055, 1075, 1108, 1128, 1156 and 1196 cm−1 are assigned to δ SbOH deformation modes. A complex pattern resulting from the overlapping band of the water and hydroxyl units is observed. Raman bands are observed at 3240, 3383, 3466, 3483 and 3552 cm−1; infrared bands at 3248, 3434 and 3565 cm−1. The Raman bands at 3240 and 3383 cm−1 and the infrared band at 3248 cm−1 are assigned to water‐stretching vibrations. The two higher wavenumber Raman bands observed at 3466 and 3552 cm−1 and two infrared bands at 3434 and 3565 cm−1 are assigned to the stretching vibrations of the hydroxyl units. Observed Raman and infrared bands in the OH stretching region are associated with O‐H···O hydrogen bonds and their lengths 2.72, 2.79, 2.86, 2.88 and 3.0 Å (Raman) and 2.73, 2.83 and 3.07 Å (infrared). Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

11.
    
Insight into the unique structure of hydrotalcites (HTs) has been obtained using Raman spectroscopy. Gallium‐containing HTs of formula Zn4 Ga2(CO3)(OH)12 · xH2O (2:1 ZnGa‐HT), Zn6 Ga2(CO3)(OH)16 · xH2O (3:1 ZnGa‐HT) and Zn8 Ga2(CO3)(OH)18 · xH2O (4:1 ZnGa‐HT) have been successfully synthesised and characterised by X‐ray diffraction (XRD) and Raman spectroscopy. The d(003) spacing varies from 7.62 Å for the 2:1 ZnGa‐HT to 7.64 Å for the 3:1 ZnGa‐HT. The 4:1 ZnGa‐HT showed a decrease in the d(003) spacing, compared to the 2:1 and 3:1 compounds. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised gallium‐containing HTs. Raman bands observed at around 1050, 1060 and 1067 cm−1 are attributed to the symmetric stretching modes of the (CO32−) units. Multiple ν3 (CO32−) antisymmetric stretching modes are found between 1350 and 1520 cm−1, confirming multiple carbonate species in the HT structure. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 and assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

12.
    
We have successfully synthesised hydrotalcites (HTs) containing calcium, which are naturally occurring minerals. Insight into the unique structure of HTs has been obtained using a combination of X‐ray diffraction (XRD) as well as infrared and Raman spectroscopies. Calcium‐containing hydrotalcites (Ca‐HTs) of the formula Ca4Al2(CO3)(OH)12·4H2O (2:1 Ca‐HT) to Ca8Al2(CO3)(OH)20· 4H2O (4:1 Ca‐HT) have been successfully synthesised and characterised by XRD and Raman spectroscopy. XRD has shown that 3:1 calcium HTs have the largest interlayer distance. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised Ca‐HTs. The Raman bands observed at around 1086 and 1077 cm−1 were attributed to the ν1 symmetric stretching modes of the (CO32−) units of calcite and carbonate intercalated into the HT interlayer. The corresponding ν3 CO32− antisymmetric stretching modes are found at around 1410 and 1475 cm−1. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

13.
    
The molecular structure of the uranyl mineral rutherfordine has been investigated by the measurement of its Raman spectra at 298 and 77 K and complemented with infrared spectra. The infrared spectra of the (CO3)2− units in the anti‐symmetric stretching region show complexity with three sets of carbonate bands observed. This, combined with the observation of multiple bands in the (CO3)2− bending region in both Raman and IR spectra, suggests that both monodentate and bidentate (CO3)2− units are present in the structure in accordance with the X‐ray crystallographic studies. Complexity is also observed in the IR spectra of (UO2)2+ anti‐symmetric stretching region and is attributed to non‐identical UO bonds. Both Raman and infrared spectra of the rutherfordine show the presence of both water and hydroxyl units in the structure, as evidenced by IR bands at 3562 and 3465 cm−1 (OH) and 3343, 3185 and 2980 cm−1 (H2O). Raman spectra show the presence of four sharp bands at 3511, 3460, 3329 and 3151 cm−1. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
    
Raman spectroscopy both at 298 and 77 K complemented with infrared spectroscopy was used to study the structure of dawsonite. Previous crystallographic studies concluded that the structure of dawsonite was a simple one; however, both Raman and infrared spectroscopy show that this conclusion is incorrect. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions, showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred around 950 cm−1 in both Raman and infrared spectra show that the OH units in the dawsonite structure are non‐equivalent. Calculations using the position of the Raman and infrared OH stretching vibrations enabled estimates of the hydrogen‐bond distances of 0.2735 and 0.27219 pm at 298 K, and 0.27315 and 0.2713 pm at 77 K to be made. This indicates strong hydrogen bonding of the OH units in the dawsonite structure. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
Gilalite is a copper silicate mineral with a general formula of Cu5Si6O17 · 7H2O. The mineral is often found in association with another copper silicate mineral, apachite, Cu9Si10O29 · 11H2O. Raman and infrared spectroscopy have been used to characterize the molecular structure of gilalite. The structure of the mineral shows disorder, which is reflected in the difficulty of obtaining quality Raman spectra. Raman spectroscopy clearly shows the absence of OH units in the gilalite structure. Intense Raman bands are observed at 1066, 1083, and 1160 cm?1.

The Raman band at 853 cm?1 is assigned to the –SiO3 symmetrical stretching vibration and the low-intensity Raman bands at 914, 953, and 964 cm?1 may be ascribed to the antisymmetric SiO stretching vibrations. An intense Raman band at 673 cm?1 with a shoulder at 663 cm?1 is assigned to the ν4 Si-O-Si bending modes. Raman spectroscopy complemented with infrared spectroscopy enabled a better understanding of the molecular structure of gilalite.  相似文献   

16.
    
Raman spectra of natrouranospinite complemented with infrared spectra were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (AsO4)3− units and of water molecules. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

17.
    
The substituent effect on structure and surface activity of mono‐ and disubstituted N‐methylpyridinium salts was investigated by means of Raman, infrared and surface‐enhanced Raman spectroscopy (SERS). The significant differences observed in Raman and infrared spectra have been correlated with marker bands assigned to in‐plane and out‐of‐plane vibrations, respectively. This vibrational analysis, complemented by quantum chemical calculations (B3LYP/6‐311++G(d,p)) was a basis for investigation of the surface activity of the studied compounds. Significant differences in their SERS spectra related to the enhancement mechanism and adsorbate orientation have been observed and analyzed. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

18.
    
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19.
    
We report the synthesis and characterization of C60@SWCNT peapods and double‐walled carbon nanotubes (DWCNTs) derived from the peapods. Single‐walled carbon nanotubes (SWCNTs), C60@SWCNT peapods, and DWCNTs were characterized by Raman and optical spectroscopy. The radial breathing modes (RBMs) of the tubes in C60@SWCNT peapods are shifted to higher energies compared to the RBMs in SWCNTs, while in the case of DWCNTs the RBMs related to the outer tubes are shifted to lower energies compared to SWCNTs. A similar trend is observed for the absorption bands. These results suggest that the filling of the SWCNTs with C60 molecules decreases the average diameter of the electron cloud around the tubes, whereas the filling with an inner tube increases it.  相似文献   

20.
    
Raman spectra of metauranospinite Ca[(UO2)(AsO4)]2·8H2O complemented with infrared spectra were studied. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (AsO4)3− units and of water molecules. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

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