FTIR studies of plasticized poly(vinyl alcohol)-chitosan blend doped with NH4NO3 polymer electrolyte membrane

Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH(4)NO(3)) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer-solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm(-1) and the amine band at 1591 cm(-1) to 1650 and 1557 cm(-1) respectively and the shift of the hydroxyl band from 3377 to 3354 cm(-1). The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm(-1) and is observed at 3343 cm(-1) in the spectrum of the PVA film. On addition of NH(4)NO(3) up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm(-1) to 1642, 1541 and 3348 cm(-1) indicating that the chitosan has complexed with the salt. In the PVA-NH(4)NO(3) spectrum, the hydroxyl band has shifted from 3343 to 3272 cm(-1) on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA-chitosan-EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA-chitosan-NH(4)NO(3) systems. In the spectrum of PVA-chitosan-NH(4)NO(3)-EC complex, the doublet CO stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.     

共聚焦拉曼光谱研究过饱和硝酸铵液滴中NH4+, NO3- 和H2O之间的相互作用

将硝酸铵液滴沉积在石英基底上,通过降低该液滴周围环境的相对湿度,测定了该液滴由低浓度直至过饱和状态下高信噪比的拉曼光谱.其中,相对湿度的变化可以精确控制液滴浓度的改变.在相对湿度(RH)由72.1%降低至37.9%的过程中,硝酸铵液滴v1-NO-3峰位保持在1048cm-1,半峰宽为10cm-1.该现象表明NO-3周围的水分子被NH4+取代后不会对v1-NO-3造成影响,说明水分子和NH4+所形成的氢键具有相同的强度.对2500-4000cm-1范围内的拉曼光谱进行成分分析,2890、3090、3140、3220、3402及3507cm-1分别被指认为NH+4伞状弯曲振动的泛频、NH+4伞状弯曲振动与摇摆振动的组合谱带、NH+4的对称伸缩振动、NH+4的反对称伸缩振动、水峰中强氢键成分和弱氢键成分.从拟合结果得出:强氢键在氢键结构中所占百分含量随液滴相对湿度的降低而减少,弱氢键所占百分含量随液滴相对湿度的降低而增加.该变化趋势是NO-3和NH+4之间复杂相互作用的结果.     

Raman spectra of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 between 295 and 60 K

Raman spectra from polycrystalline samples of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 have been studied in the temperature range 60-295 K. Internal modes of both nitrate and tetrachlorozincate ions show expected band narrowing and intensification at lower temperature but no significant changes in frequency. Two bands in the lattice region of both compounds, assigned to nitrate ion libration and rocking, show linear increases in frequency with lowering temperature. The intensity of the libration mode shows a linear decrease with lowering temperature, but the intensity of the rocking mode is relatively insensitive to temperature change. Ammonium ion bands show greater structure at low temperature, suggesting differentiation between the two crystallographically distinct types of cation. The observed spectral changes are interpreted on the basis of increasing ordering and effectiveness of hydrogen bonds between ammonium ions and nitrate ions at low temperatures. The Raman spectra give no evidence of discontinuous changes in frequency or intensity, which would signal temperature-dependent transitions of the crystal structure. Unlike the related single-anion compounds NH4NO3 and (NH4)2ZnCl4, the room-temperature structure of (NH4)3ZnCl4NO3 and (ND4)3ZnCl4NO3 appears to persist at least to 60 K, being stabilized by increasingly ordered hydrogen bonding.     

Adsorption-energetic and IR spectroscopic studies of NH4 natrolite

The ammonium form of natural zeolite, natrolite, obtained by vapor phase ion exchange is similar to calcium-containing zeolites of the natrolite group in its de- and rehydration characteristics and the heats of immersion in water. The adsorption capacity and the heat of immersion in water are maximum after evacuation of the zeolite at 200 °C. The irreversible sintering of NH₄ natrolite occurs above 200 °C (up to 45% at 500 °C), accompanied by the formation of hydroxyl groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 359–361, February, 1998.     

Infrared spectroscopic study of the phase transitions in CsNO3, RbNO3 and NH4NO3

Phase transitions of CsNO₃ (II-I), RbNO₃ (IV-III-II) and NH₄NO₃ (V-IV-III-II-I) have been studied by i.r. spectroscopy. The study has provided useful information on the changes in the dispositions of the ions during the phase transitions.     

Laser Raman and FTIR studies on Li+ interaction in PVAc-LiClO4 polymer electrolytes

The polymer electrolytes composed of poly(vinyl acetate) (PVAc) with various stoichiometric ratios of lithium perchlorate (LiClO(4)) salt have been prepared by solution casting method. The techniques Fourier transform infra-red (FTIR) and Laser Raman spectroscopy have been used to monitor polymer-salt complex formation, ion-ion and ion-polymer interactions as a function of salt concentration. Significant changes in both Laser Raman and FTIR spectra are observed which reveals an interaction between ester oxygens with lithium cation coordination. These results strongly suggest the interaction of lithium cation and network polymer chains. When the salt content is increased, the intensity of the internal Raman modes of the ClO(4)(-) increases. The ClO(4)(-) stretching mode observed at 934 cm(-1) in Laser Raman shows some additional shoulder peaks with increase in salt concentration. This reveals the presence of free anions, ion contact pairs and higher order ionic clusters. From the FTIR and Laser Raman results the transport mechanism of ions in PVAc:LiClO(4) polymer electrolytes has been discussed.     

Raman spectroscopic study of (CH3NH3)2HgCl4 in the high-temperature range

A Raman spectroscopic study of (CH₃NH₃)₂HgCl₄ is reported in the temperature range 299–373 K. Discontinuities in the HgCl symmetric stretching mode and in the frequency shift of the CN stretching mode indicate a new phase above 330 K. A non-linear increment of the widths of these bands confirms the transition. Arrhenius behaviour of the CN stretching mode indicates a barrier of 1234 cm⁻¹.     

Raman spectroscopic study of aqueous (NH4)2SO4 and ZnSO4 solutions

The Raman spectra of the v₁-SO ₄ ^2– band in 0.5–2.5 molar aqueous (NH₄)₂SO₄ and ZnSO₄ solutions in the temperature range 25–85°C were studied. The molar scattering coefficient of the v₁ band is the same for all forms of sulfate in (NH₄)₂SO₄ and ZnSO₄ solutions and is independent of temperature up to 85°C. The v₁ band profile is symmetrical in (NH₄)₂SO₄ solutions. In ZnSO₄ solutions, a shoulder appears on the high frequency side which increases slightly in intensity with increasing concentration and temperature. This high frequency component is attributed to the formation of the contact ion pair (Zn²⁺·SO ₄ ^2– ). The enthalpy of formation for the contact ion pair is estimated from the Raman data to be approximately 3 kJ-mol^–1 which is in reasonable agreement with measurements by other methods.     

Positron annihilation lifetime studies of free volume in a polymer electrolyte PEO complexed with NH4I

Positron lifetime spectroscopy has been applied to study the temperature dependence of free-volume properties in a solvent-free polymer–salt complex polyethylene oxide (PEO) doped with ammonium iodide (NH₄I, with NH ≈ 0.076) in the temperature range of 298–353 K. The observed lifetime spectra were resolved into three components and the longest lifetime, τ₃, was associated with the pick-off annihilation of ortho-positronium (o-Ps) trapped by the free volume. The lifetime component, τ₃, and its intensity, I₃, both showed a significant variation with temperature, which followed a different course in the heating and cooling cycle. Changes in the temperature coefficient of τ₃ and I₃ were observed at T ≈ 328 K, the melting point of the sample. This behaviour is correlated to the temperature variation of the electrical conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 969–976, 1998     

Drawing out the structural information of the first layer of hydrated ions: ATR-FTIR spectroscopic studies on aqueous NH4NO3, NaNO3, and Mg(NO3)2 solutions

ATR-FTIR technique was used to obtain the difference spectra of aqueous NH4NO3 NaNO3, and Mg(NO3)2 solutions, with NO3- concentrations ranging from 0 to 4.00 mol dm(-3). The water monomers weakly hydrogen bonded with NO3- ions showed a positive peak near at 3565 cm(-1) for both Mg(NO3)2 and NH4NO3 solutions. The positive peak was shift to approximately 3543 cm(-1) for NaNO3 solutions due to the total contributions of the hydrated NO3- (approximately 3565 cm(-1)) and the hydrated Na+ (approximately 3440 cm(-1)). Compared with perchlorate solutions, the positive peak of nitrate solutions has a red shift of about 20 cm(-1) and the peak area is about half of that of perchlorate solutions with the same concentrations, indicating that the hydrogen bonding between NO3- and water monomers is relative stronger than that between ClO4- and water monomers, and NO3- has a strict requirement on the orientation of water molecules when hydrogen bonded with water monomers due to its planar structure. The ab initio calculations were used to understand the splitting of the nu3 band and hydration effect on the infrared activation of the nu1. The absorbance of nu3b, nu1 and nu2 bands, dependent on the type of cations, was observed to departed from Beer low with increasing concentrations, which is considered as the results of the interactions between cations and nitrate ions.     

FT-IR spectroscopic investigation of ionic interactions in PPG 4000: AgCF3SO3 polymer electrolyte

The effect of salt concentration on the ubiquitous ionic interactions observed in the case of the silver ion conducting polymer electrolyte system poly(propylene glycol) (PPG)-silver triflate has been investigated using Fourier transform infrared (FT-IR) spectroscopy as a probe for the characterization of the local environment of the triflate ion in PPG-based polymer electrolytes. The maximum free anion concentrations of symmetric and asymmetric SO(3) stretching modes in the case of poly(propylene glycol) complexed with silver triflate (AgCF(3)SO(3)) corresponding to the ether oxygen metal cation ratios from 2:1 to 6:1 have been investigated in detail. The present Fourier transform infrared spectral studies of the C-O-C stretching mode have shown reduction in the intensity, due to the decrease of salt concentration. The splitting of vibrational modes has been analyzed in terms of free ions, ion pairs and aggregates. The bands of SO(3) symmetric stretching mode appearing at 1032 and 1038 cm(-1) in the chosen polymer electrolyte material have been assigned to free ions and ion pairs respectively.     

Electrochromic NiOxHy,hydrated films: cyclic voltammetry and ac impedance spectroscopy in aqueous electrolyte

The characteristics of the electrochromic process of sputtered hydrated nickel oxide films have been investigated by cyclic voltainmetry, in situ optical transmittance and ac impedance spectroscopy. The results indicate that the state of coloration of these films is related to the conditions used to drive the electrochromic process, whose kinetics at high positive potentials become controlled by ion diffusion into and from the nickel oxide structure.     

Raman spectra of the double-anion salts M3ZnCl4NO3 (M+ = K+, Rb+, NH4)

Recently characterized K3ZnCl4NO3 and (NH4)3ZnCl4NO3, and newly prepared Rb3ZnCl4NO3 constitute a limited series of isomorphous double-anion salts (space group Pnma, Z = 4). Room-temperature (295 K) Raman spectra from polycrystalline samples of the compounds are reported and interpreted on the basis of the Cs site symmetry of the ZnCl4(2-) and NO3- ions with reference to the D2h factor group of the unit cell. The spectra are compared with Raman spectra of the corresponding M2ZnCl4 and MNO3 single-anion salts. Relative positions and frequencies of the ZnCl4(2-) modes vary considerably among the M3ZnCl4NO3 compounds, despite the isomorphism. The NO3- modes are more similar in all three compounds. The NO3- doubly degenerate v3 and V4 modes are split into two distinct bands as a result of the decent in symmetry from D3h for the free ion to Cs at the crystallographic site. The unequal intensities of the v3 bands observed for K3ZnCl4NO3 and Rb3ZnCl4NO3 and the equal intensities of the v4 bands observed for all three compounds suggest the same factor-group assignments as the high-temperature phase NH4NO3(III). The free-ion Raman-inactive planar deformation mode, v2, is evident in all three compounds, but with lesser intensity than its overtone 2v2. In K3ZnCl4NO3 and Rb3ZnCl4NO3, the symmetric stretching band, in addition to the very strong component for v1, shows a weak, low-frequency band found in many ionic nitrates, which has been attributed to thermally disordered nitrate ions or hot bands. This feature is not found in the spectrum of (NH4)3ZnCl4NO3. The 12 NH4+ ions in the unit cell of (NH4)3ZnCl4NO3, which occupy C1 and Cs sites in a 2:1 ratio, give rise to extremely broad bands that show no evidence of the individual symmetry distinctions of the cations. The broad band from NH4+ v4 obscures the region in which NO3- v3 bands are expected, but the NO3- overtone 2v2 is evident as a sharp peak above a similarly broad band from NH4+ v2.     

四氯合锌酸烷基铵层形结构配合物的Raman光谱研究

测定了[n-CnH2n+1NH3]2ZnCl(n=7～12, 16)配合物在碳氢伸缩、碳氢弯曲、碳碳伸缩和低频区的Raman光谱。发现它们的频率和相对强度与分子中烷基链的链长有关, 并且表现出碳原子数的奇偶效应。从不同的分子堆积结构和分子间相互作用的角度讨论了光谱变化。     

Laser spectroscopic studies of Tb3+-doped oxyfluoroborate glass

Tb3+-doped oxyfluoroborate glasses have been prepared for different concentrations of Tb. The absorption, fluorescence and photoacoustic spectra of these have been recorded and studied. It is marked that the fluorescence intensity of different fluorescence transitions decreases with the increase of Tb ion concentration in the glass. This quenching at higher concentration is due to the energy transfer among the excited and nearest neighbor unexcited Tb ions in the glass. The lifetime measurement confirms it, as the lifetime of a particular state was found to decrease with the increase of Tb ion concentration in the glass. The mechanism of the energy transfer process was determined to involve quadrupole quadrupole interaction. We have also studied the energy transfer from Tb3+-->Pr3+ when both the rare earths are doped together in the glass. A decrease in the lifetime of the 5D4 level of Tb3+ with the increase of Pr3+ concentration confirms this.     

Raman spectroscopic determination of oxoanions in aqueous polysulfide electrolyte solutions

The equilibrium distribution of aqueous sodium polysulfide solutions is investigated over a wide concentration range using Raman spectroscopy technique. A total of eighteen bands were determined in the spectra recorded for aqueous electrolyte solutions of different S:Na ratios. Beyond the presence of four polysulfide (S_n²⁻) species, where “n” varied between 2 and 5 as reported in previous literature, the originality of this study is to show the presence of oxidised sulfur species in these aqueous polysulfide solutions. A detailed comparison of all the bands for polysulfide and oxoanion species determined in this study with those cited in literature is summarised.     

Characterization of biodegradable solid polymer electrolyte system based on agar-NH4Br and its comparison with NH4I

Journal of Solid State Electrochemistry - Concerning the pollution-free and eco-friendly materials, the prospect of using biopolymer as ion conducting matrix has been investigated in this study....     

Raman and infrared spectra of phase transition in CH3NH3ClO4

Studies on the temperature variation of infrared and Raman spectra in the range 298 to 460K have shown the presence of two structural phase transitions at 321 and 451K. Phase III

transition is of first order. Phase I exhibits isotropic reorientational motion of the cations and anions.