A spectroscopic study of the mineral paceite (calcium acetate)

A comprehensive spectroscopic analysis consisting of Raman, infrared (IR) and near-infrared (NIR) spectroscopy was undertaken on two forms of calcium acetate with differing degrees of hydration. Monohydrate (Ca(CH(3)COO)(2).H(2)O) and half-hydrate (Ca(CH(3)COO)(2).0.5H(2)O) species were analysed. Assignments of vibrational bands due to the acetate anion have been made in all three forms of spectroscopy. Thermal analysis of the mineral was undertaken to follow its decomposition under a nitrogen atmosphere. Three major mass loss steps at approximately 120, 400 and 600 degrees C were revealed. These mass losses correspond very well to firstly, the loss of co-ordinated water molecules, and then the loss of water from the acetate anion, followed by finally the loss of carbon dioxide from the carbonate mineral to form a stable calcium oxide.     

Raman spectroscopy of stercorite H(NH4)Na(PO4)·4H2O--a cave mineral from Petrogale Cave, Madura, Eucla, Western Australia

Raman spectroscopy complimented with infrared spectroscopy has been used to characterise the mineral stercorite H(NH4)Na(PO4)·4H2O. The mineral stercorite originated from the Petrogale Cave, Madura, Eucla, Western Australia. This cave is one of many caves in the Nullarbor Plain in the South of Western Australia. These caves have been in existence for eons of time and have been dated at more than 550 million years old. The mineral is formed by the reaction of bat guano chemicals on calcite substrates. A single Raman band at 920 cm(-1) defines the presence of phosphate in the mineral. Antisymmetric stretching bands are observed in the infrared spectrum at 1052, 1097, 1135 and 1173 cm(-1). Raman spectroscopy shows the mineral is based upon the phosphate anion and not the hydrogen phosphate anion. Raman and infrared bands are found and assigned to PO4(3-), H2O, OH and NH stretching vibrations. The detection of stercorite by Raman spectroscopy shows that the mineral can be readily determined; as such the application of a portable Raman spectrometer in a 'cave' situation enables the detection of minerals, some of which may remain to be identified.     

A Raman spectroscopic study of thermally treated glushinskite--the natural magnesium oxalate dihydrate

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG-MS identified two mass loss steps at 146 and 397 degrees C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 degrees C. Above 397 degrees C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 degrees C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.     

Variable denticity in carboxylate binding to the uranyl coordination complexes

Tris-carboxylate complexes of uranyl [UO₂]²⁺ with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetato uranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric −CO₂ stretches of the monodentate and bidentate acetate, CH₃ bending and umbrella vibrations, and a uranyl O—U—O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the predominant conformer of the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate and two bidentate benzoate ligands.     

Mechanism of dehydroxylation temperature decrease and high temperature phase transition of coal-bearing strata kaolinite intercalated by potassium acetate

The thermal decomposition and dehydroxylation process of coal-bearing strata kaolinite-potassium acetate intercalation complex (CSKK) has been studied using X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis, mass spectrometric analysis and infrared emission spectroscopy. The XRD results showed that the potassium acetate (KAc) have been successfully intercalated into coal-bearing strata kaolinite with an obvious basal distance increase of the first basal peak, and the positive correlation was found between the concentration of intercalation regent KAc and the degree of intercalation. As the temperature of the system is raised, the formation of KHCO(3), KCO(3) and KAlSiO(4), which is derived from the thermal decomposition or phase transition of CSKK, is observed in sequence. The IR results showed that new bands appeared, the position and intensities shift can also be found when the concentration of intercalation agent is raised. The thermal analysis and mass spectrometric analysis results revealed that CSKK is stable below 300°C, and the thermal decomposition products (H(2)O and CO(2)) were further proved by the mass spectrometric analysis. A comparison of thermal analysis results of original coal-bearing strata kaolinite and its intercalation complex gives new discovery that not only a new mass loss peak is observed at 285 °C, but also the temperature of dehydroxylation and dehydration of coal bearing strata kaolinite is decreased about 100 °C. This is explained on the basis of the interlayer space of the kaolinite increased obviously after being intercalated by KAc, which led to the interlayer hydrogen bonds weakened, enables the dehydroxylation from kaolinite surface more easily. Furthermore, the possible structural model for CSKK has been proposed, with further analysis required in order to prove the most possible structures.     

Infrared spectroscopic study of natural hydrotalcites carrboydite and hydrohonessite

Infrared spectroscopy has proven most useful for the study of anions in the interlayer of natural hydrotalcites. A suite of naturally occurring hydrotalcites including carrboydite, hydrohonessite, reevesite, motukoreaite and takovite were analysed. Variation in the hydroxyl stretching region was observed and the band profile is a continuum of states resulting from the OH stretching of the hydroxyl and water units. Infrared spectroscopy identifies some isomorphic substitution of sulphate for carbonate through an anion exchange mechanism for the minerals carrboydite and hydrohonessite. The infrared spectra of the CO3 and SO4 stretching region of takovite is complex because of band overlap. For this mineral some sulphate has replaced the carbonate in the structure. In the spectra of takovites, a band is observed at 1346 cm(-1) and is attributed to the carbonate anion hydrogen bonded to water in the interlayer. Infrared spectroscopy has proven most useful for the study of the interlayer structure of these natural hydrotalcites.     

Moving-window two-dimensional correlation infrared spectroscopy study on structural variations of partially hydrolyzed poly(vinyl alcohol)

In the present study, the molecular chain changes and structural transitions of partially hydrolyzed poly(vinyl alcohol) (PVA) having a 12 mol% acetate unit were analyzed by moving-window two-dimensional (MW2D) correlation infrared spectroscopy combined with differential scanning calorimetry and thermogravimetric analysis. The results show the glass-transition temperature (T _g ) of PVA is clearly distinguished by MW2D correlation infrared spectroscopy, and the acetate groups start to be eliminated around the melting temperature, whereas the free water molecules in PVA are eliminated above T _g. The correlation movements of the O–H stretching modes, including the free hydroxyl groups and the hydrogen bonds, are clearly determined using MW2D correlation infrared spectroscopy. The spectral variations in the C=O stretching region caused by the elimination of the acetate unit from polymer chains are also discussed on the basis of the results of the MW2D correlation analysis. Such results cannot be obtained by traditional infrared spectroscopy owing to the complex overlapping peaks.

Vibrational spectroscopy of synthetic stercorite H(NH4)Na(PO4)·4H2O--a comparison with the natural cave mineral

In order to mimic the chemical reactions in cave systems, the analogue of the mineral stercorite H(NH(4))Na(PO(4))·4H(2)O has been synthesised. X-ray diffraction of the stercorite analogue matches the stercorite reference pattern. A comparison is made with the vibrational spectra of synthetic stercorite analogue and the natural Cave mineral. The mineral in nature is formed by the reaction of bat guano chemicals on calcite substrates. A single Raman band at 920 cm(-1) (Cave) and 922 cm(-1) (synthesised) defines the presence of hydrogen phosphate in the mineral. In the synthetic stercorite analogue, additional bands are observed and are attributed to the dihydrogen and phosphate anions. The vibrational spectra of synthetic stercorite only partly match that of the natural stercorite. It is suggested that natural stercorite is more pure than that of synthesised stercorite. Antisymmetric stretching bands are observed in the infrared spectrum at 1052, 1097, 1135 and 1173 cm(-1). Raman spectroscopy shows the stercorite mineral is based upon the hydrogen phosphate anion and not the phosphate anion. Raman and infrared bands are found and assigned to PO(4)(3-), H(2)O, OH and NH stretching vibrations. Raman spectroscopy shows the synthetic analogue is similar to the natural mineral. A mechanism for the formation of stercorite is provided.     

Insight into the thermal decomposition of kaolinite intercalated with potassium acetate: an evolved gas analysis

The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.     

Vibrational spectroscopy of stichtite

Raman spectroscopy complimented with infrared spectroscopy has been used to study the mineral stitchtite, a hydrotalcite of formula Mg6Cr2(CO3)(OH)16.4H2O. Two bands are observed at 1087 and 1067 cm(-1) with an intensity ratio of approximately 2.5/1 and are attributed to the symmetric stretching vibrations of the carbonate anion. The observation of two bands is attributed to two species of carbonate in the interlayer, namely weakly hydrogen bonded and strongly hydrogen bonded. Two infrared bands are found at 1457 and 1381 cm(-1) and are assigned to the antisymmetric stretching modes. These bands were not observed in the Raman spectrum. Two infrared bands are observed at 744 and 685 cm(-1) and are assigned to the nu4 bending modes. Two Raman bands were observed at 539 and 531 cm(-1) attributed to the nu2 bending modes. Importantly the band positions of the paragenically related hydrotalcites stitchtite, iowaite, pyroaurite and reevesite all of which contain the carbonate anion occur at different wavenumbers. Consequently, Raman spectroscopy can be used to distinguish these minerals, particularly in the field where many of these hydrotalcites occur simultaneously in ore zones.     

Ligand exchange upon oxidation of a dinuclear Mn complex--detection of structural changes by FT-IR spectroscopy and ESI-MS

The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn(2)(bpmp)(mu-OAc)2]+(bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD(3)CN-D(2)O mixtures following the v(as(C-O)) bands of bound acetate at 1594.4 cm(-1)(II,II), 1592.0 cm(-1)(II,III) and 1586.5 cm(-1)(III,III). Substantial loss of bound acetate occurs at much lower water content (< 0.5% v/v) in the III,III state than in the II,II and II,III states (> or = 10%). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, approximately 1725 cm(-1), v(C-O)) from the released acetate (1573.6 cm(-1), v(as(C-O))). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-mu-oxo bridged III,IV dimer [Mn(2)(bpmp)(mu-O)(2)](2+)(m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-mu-acetato complex (0.61 V vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru[bpy)(3)](3+) in previous EPR studies.     

高性能氢化星型聚(苯乙烯-b-丁二烯-b-苯乙烯)嵌段共聚物阴离子交换膜的制备、结构与性能

利用常压催化加氢法合成氢化星型聚(苯乙烯-b-丁二烯-b-苯乙烯)嵌段共聚物(HSBS),依次通过氯甲基化、季铵化和碱化反应,制备两种综合性能良好的碱性阴离子交换膜(AEMs),HSBS4303-OH和HSBS4402-OH(二者制备原料中苯乙烯质量分数分别为30%和40%)。 采用傅里叶变换红外光谱(FTIR)对AEMs的结构和制备过程进行表征,并对膜的离子电导率、吸水率、溶胀度、机械性能、微相结构和耐碱稳定性等进行系统地研究。 结果表明,HSBS在90 ℃左右出现了对应于结晶结构的特征熔融峰,相较于SBS,其机械性能及尺寸稳定性显著提高。 两种AEMs中,HSBS4402-OH的性能最佳,该膜的离子交换容量为1.99 mmol/g,30 ℃时的吸水率和溶胀度分别为27.65%和5.12%,80 ℃下的离子电导率高达86.8 mS/cm。 在60 ℃下,采用2 mol/L NaOH溶液浸泡432 h后,该膜的离子电导率损失仅为8.3%。 显而易见,本文方法能为碱性阴离子交换膜燃料电池提供很有前途的AEMs。     

Analytical strategy for rapid identification and quantification of lubricant additives in mineral oil by high-performance thin-layer chromatography with UV absorption and fluorescence detection combined with mass spectrometry and infrared spectroscopy

A simple strategy for identification and quantification of lubricant additives in mineral oil was demonstrated by high-performance thin-layer chromatography with UV absorption and fluorescence detection using various coupling options, e.g., with attenuated total reflectance infrared (ATR-IR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and direct analysis in real-time mass spectrometry (DART-MS). For the additives zinc bis(O,O'-diisobutyl dithiophosphate), zinc bis(O,O'-didodecyl dithiophosphate), and Anglamol 99, 2 chromatographic systems were developed, i.e., a reversed-phase (RP) system on RP2 plates using an acetonitrile-based mobile phase and a normal-phase system on silica gel 60 plates using a toluene-based gradient. Densitometry was performed by absorption measurement at 220 nm. Repeatabilities (relative standard deviation, n = 6) between 2.2 and 5.5% and correlation coefficients >0.9973 were highly satisfactory for the analysis of these additives in the mineral oil. Primuline reagent was used to improve the detection limit of the lipophilic additives by a factor of 2, followed by fluorescence measurement at UV 366/>400 nm. For rapid identification by ATR-IR and FTIR, the respective additive zones on the plate were online extracted by an interface called ChromeXtract, concentrated, and directly applied for measurements in the wave number range of 4000-400 cm(-1). Identification was confirmed by online ESI-MS within a minute using ChromeXtract and by DART-MS within seconds.     

IR laser-induced decomposition of poly(vinyl chloride-co-vinyl acetate): Control of products by irradiation conditions

IR laser-induced, ablative decomposition of poly(vinyl chloride-co-vinyl acetate) was examined under different irradiation conditions and its volatile and solid products were characterized by mass spectroscopy, infrared spectroscopy, Raman spectroscopy and UV spectroscopy and EDX-measurements. The laser decomposition of the copolymer, compared with that of poly(vinyl acetate) and poly(vinyl chloride), is revealed to be a more efficient process leading to solid films with the proportion of Cl- and CH₃C(O)O-groups controlled by irradiation conditions.     

Radiation induced graft polymerization of multi-walled carbon nanotubes for superhydrophobic composite membrane preparation

Highly soluble multi-walled carbon nanotubes (MWNTs) were prepared by radiation-induced free radical graft polymerization of vinyl acetate (VAc) onto pristine MWNT surfaces. High resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, and micro-Raman spectroscopy were used to confirm that poly(vinyl acetate) (PVAc) had been successfully grafted onto the surface of the MWNTs. The effects of experimental parameters on the degree of grafting (DG) of PVAc were also investigated, including adsorbed dose, dose rate, initial monomer concentration, and solvents. The grafted MWNTs (MWNTs-g-PVAc) exhibited good solubility in common organic solvents at high mass fraction. In addition, a superhydrophobic composite membrane could be readily fabricated by vacuum filtration of MWNTs-g-PVAc onto a supporting membrane, as was confirmed by water contact angle testing and visualization by scanning electron microscopy.     

Microhydration of the magnesium(II) acetate cation in the gas phase

Electrospray ionization of aqueous solutions of magnesium(II) acetate leads to microhydrated magnesium acetate cations of the type [(CH(3)COO)(2m-1)Mg(m)(H(2)O)(n)](+) with m = 1-4 and n = 0-4, which are characterized by mass spectrometry and, for the cluster with three water molecules, also by infrared multiphoton dissociation spectroscopy. Density functional theory is used to determine the energies of microhydration for the mononuclear species [(CH(3)COO)Mg(H(2)O)(n)](+) with n = 0-6 and the associated changes in molecular structure. While bidentate coordination of the acetato ligand is generally preferred, at higher values of n, a switch to a monodentate coordination becomes energetically competitive.     

A vibrational spectroscopic study of the mixed anion mineral sanjuanite Al2(PO4)(SO4)(OH)·9H2O

The mineral sanjuanite Al2(PO4)(SO4)(OH)·9H2O has been characterised by Raman spectroscopy complimented by infrared spectroscopy. The mineral is characterised by an intense Raman band at 984 cm(-1), assigned to the (PO4)3- ν1 symmetric stretching mode. A shoulder band at 1037 cm(-1) is attributed to the (SO4)2- ν1 symmetric stretching mode. Two Raman bands observed at 1102 and 1148 cm(-1) are assigned to (PO4)3- and (SO4)2- ν3 antisymmetric stretching modes. Multiple bands provide evidence for the reduction in symmetry of both anions. This concept is supported by the multiple sulphate and phosphate bending modes. Raman spectroscopy shows that there are more than one non-equivalent water molecules in the sanjuanite structure. There is evidence that structural disorder exists, shown by the complex set of overlapping bands in the Raman and infrared spectra. At least two types of water are identified with different hydrogen bond strengths. The involvement of water in the sanjuanite structure is essential for the mineral stability.     

Infrared photodissociation spectroscopy of mononuclear iron carbonyl anions

The infrared photodissociation spectroscopy of mass-selected mononuclear iron carbonyl anions Fe(CO)(n)(-) (n = 2-8) were studied in the carbonyl stretching frequency region. The FeCO(-) anion does not fragment when excited with infrared light. Only a single IR active band was observed for the Fe(CO)(2)(-) and Fe(CO)(3)(-) anions, consistent with theoretical predictions that these complexes have linear D(∞h) and planar D(3h) symmetry, respectively. The Fe(CO)(4)(-) anion is the most intense peak in the mass spectra and was characterized to have a completed coordination sphere with high stability. Anion clusters larger than n = 4 were determined to involve a Fe(CO)(4)(-) core anion that is progressively solvated by external CO molecules. Three CO stretching vibrational fundamentals were observed for the Fe(CO)(4)(-) core anion, indicating that the Fe(CO)(4)(-) anion has a C(3v) structure. All the carbonyl stretching frequencies of the Fe(CO)(n)(-) anion complexes are red-shifted with respect to those of the corresponding neutrals.     

A Raman and infrared spectroscopic study of the mineral delvauxite CaFe4(3+)(PO4,SO4)2(OH)8·4-6H2O--a 'colloidal' mineral

The mineral delvauxite CaFe(4)(3+)(PO(4),SO(4))(2)(OH)(8)·4-6H(2)O has been characterised by Raman spectroscopy and infrared spectroscopy. The mineral is associated with the minerals diadochite and destinezite. Delvauxite appears to vary in crystallinity from amorphous to semi-crystalline. The mineral is often X-ray non-diffracting. The minerals are found in soils and may be described as 'colloidal' minerals. Vibrational spectroscopy enables determination of the molecular structure of delvauxite. Bands are assigned to phosphate and sulphate stretching and bending modes. Two symmetric stretching modes for both the phosphate and sulphate symmetric stretching modes support the concept of non-equivalent phosphate and sulphate units in the mineral structure. Multiple water bending and stretching modes imply that non-equivalent water molecules in the structure exist with different hydrogen bond strengths.     

Novel ferrocene-based ionic liquid supported on silica nanoparticles as efficient catalyst for synthesis of naphthopyran derivatives

We report synthesis of silica nanospheres containing ferrocene-tagged imidazolium acetate (SiO₂@Im-Fc[OAc]) as efficient heterogeneous nanocatalyst for synthesis of naphthopyran derivatives under solvent-free conditions, based on modification of nano SiO₂ by ionic liquid with ferrocene tags and subsequent anion metathesis reaction. The synthesized novel nanocatalyst (SiO₂@Im-Fc[OAc]) was systematically characterized using Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, and field-emission scanning electron microscopy. The catalytic activity of (SiO₂@Im-Fc[OAc]) was tested in one-pot three-component reaction of aromatic aldehydes, malononitrile, and 2-naphthol for facile synthesis of naphthopyran derivatives. To achieve high catalytic efficacy, the effects of various reaction parameters such as temperature, amount of catalyst, type of solvent, etc. were investigated. Furthermore, recovery and reuse of the nanocatalyst several times was demonstrated without appreciable loss in catalytic activity. The presented protocol offers several advantages, including green and ecofriendly nature, operational simplicity, higher yield, and easy recovery and reuse of the nanostructured catalyst. The workup of these very clean reactions involves only recrystallization of the product from ethanol and recovery of the catalyst by filtration.