Fourier Transform Infrared Studies Research Articles

Cyanamide as an Infrared Reporter: Comparison of Vibrational Properties between Nitriles Bonded to N and C Atoms.

Infrared (IR) probes based on terminally blocked β-cyanamidoalanine (AlaNHCN) 1 and p-cyanamidophenylalanine (PheNHCN) 2 were synthesized, and the vibrational properties of their CN stretch modes were studied using Fourier transform infrared (FTIR) and femtosecond IR pump-probe spectroscopies in combination with quantum chemical calculations. From FTIR studies, it is found that the transition dipole strengths of the cyanamide (NHCN) group in 1 and 2 are much larger than those of the nitrile (CN) group but comparable to those of the isonitrile (NC) and azido (N3) groups in their previously studied analogs. The CN stretch frequencies in 1 and 2 are red-shifted from those in their nitrile analogs but more blue-shifted from the NC and N3 stretch frequencies in their isonitrile and azido analogs. The much larger transition dipole strength and the red-shifted frequency of the cyanamide relative to nitrile group originates from the n → π* interaction between the N atom's nonbonding (n) and CN group's antibonding (π*) orbitals of the NHCN group. Unlike aliphatic cyanamide 1, aromatic cyanamide 2 shows a complicated line shape of the CN stretch spectra. Such a complicated line shape arises from the Fermi resonance between the CN stretch mode of the NHCN group and one of the overtones of the phenyl ring vibrations and can be substantially simplified by deuteration of the NHCN into NDCN group. From IR pump-probe experiments, the vibrational lifetimes of the CN stretch mode in 1 were determined to be 0.58 ± 0.04 ps in D2O and 0.89 ± 0.09 ps in H2O and those in 2 were determined to be 1.64 ± 0.13 ps in CH3OD/dimethyl sulfoxide and 0.30 ± 0.05 and 2.62 ± 0.26 ps in CH3OH. The short time component (0.30 ± 0.05 ps) observed for 2 in CH3OH is attributed to the vibrational relaxation through Fermi resonance. These vibrational lifetimes are close to those of the nitrile and azido groups but shorter than those of the isonitrile group. Consequently, cyanamide behaves like an apparent vibrational hybrid of nitrile and isonitrile in that cyanamide is similar to nitrile in vibrational frequency and lifetime but to isonitrile in transition dipole strength. It is believed that cyanamide has the potential to be a strongly absorbing IR reporter of the conformational and environmental structure and dynamics of biomolecules in comparison to nitrile, a weak absorber.

Studies on Conducting Polymer Blends: Synthesis and Characterizations of PVA/PVP Doped with CaCl₂.

Calcium ion conducting polymer blend electrolyte films based on PVA/PVP complexed with CaCl2 have been prepared by solution casting technique. The structural changes of the polymer blends have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. XRD and FT-IR studies confirmed the complex formation of polymer blends. Electrical conductivity was calculated with impedance analyzer within the frequency range 42 Hz-1 MHz and in the temperature range 303 K-340 K. The higher electrical conductivity value of 1.704 × 10-4 Scm-1 was observed for 50PVA:50PVP:15 wt% CaCl2 concentration at room temperature. The magnitude of electrical conductivity was increased with the increase in the salt concentration as well as temperature. The electrical permittivity of the polymer films have been studied for various temperatures.

EVALUATION OF THE ANTIBACTERIAL ACTIVITY OF CALCIUM ALGINATE BEADS MODIFIED WITH ETHANOLIC EXTRACT OF ADHATODA VASICA LEAF EXTRACT ON STAPHYLOCOCCUS AUREUS AND ESCHERICHIA COLI

Objective: The objective of the present study was to investigate the antibacterial activity of calcium alginate (Ca-ALG) loaded with ethanolic extract of Adhatoda vasica (A. vasica) leaves against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).Methods: Ca-ALG beads containing ethanolic extract of A. vasica leaves were developed by ionic gelation technique. The prepared Ca-ALG beads were characterized by Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The antibacterial effect of A. vasica leaf extract loaded Ca-ALG beads was examined against S. aureus and E. coli. Results: FT-IR studies revealed the cross-linking of ALG and calcium ions. The spherical morphology of the beads was designated by SEM. The prepared beads were found to display distinctive growth inhibition against S. aureus and E. coli.Conclusion: The antibacterial activity analysis indicated that the prepared beads have good activity against S. aureus and E. coli. The present study proposes a strategy to enhance antibacterial properties of ALG which are widely used in biomedical applications.

Vibrational heavy atom effect controls relaxation and spectral diffusion in triphenyl hydride complexes

A series of three triphenyl hydride compounds was investigated in a range of solvents by Fourier transform infrared (FTIR), IR pump-probe, and two-dimensional IR (2D-IR) spectroscopies. The mass of the central atom of the three compounds was varied systematically down the group 14 elements of silicon, germanium, and tin. FTIR studies provided evidence that the solvent perturbs the three hydride modes in a similar manner, as indicated by identical solvatochromic and broadening trends. IR pump-probe measurements showed that the vibrational lifetime of the hydride stretch increased when the mass of the central atom increased. Density functional theory calculations asserted that the vibrational modes of the three compounds are nearly identical except for the hydride stretching and wagging modes. Interestingly, frequency-frequency correlation functions obtained from 2D-IR spectra indicated that an increasingly large central atom produces small, but measurable changes in the dynamics of the solvation shell surrounding each compound.

Preparation of hydroxyapatite-titanium particle hierarchical filled polyetheretherketone functional gradient biocomposites

Abstract Functional gradient biomaterials have been widely applied in the biomedical field due to their designable structure and performance. In this paper, hydroxyapatite-titanium particles hierarchical filled polyetheretherketone functional gradient biocomposites [(HA-Ti)/PEEK FGBm] were successfully fabricated through combination of a layer-by-layer casting method and hot pressing technology. The microstructure and morphology of the FGBm were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive X-ray analysis spectrometry (EDS) and scanning electron microscopy (SEM). The results of XRD and EDS verified that the components of the FGBm consist of HA, Ti and PEEK. FTIR and SEM studies showed that the existence of TiO2 thin film on the surface of Ti particles was beneficial to improve the wettability of Ti particles to the PEEK matrix, thus increasing the interfacial bonding strength between Ti particles and PEEK matrix. The SEM observation revealed that the size of HA particles in (HA-Ti)/PEEK FGBm was on the nano-scale and that of Ti particles was on the micron-scale. Furthermore, several typical microstructures such as micro-pores, dimple-like, and encapsulated-like morphologies in (HA-Ti)/PEEK FGBm were observed by SEM. With the rise of Ti and HA particle content in PEEK matrix, the distribution of them in PEEK matrix becomes more and more inhomogeneous and they tend to agglomerate.

PSIDIUM GUAJAVA: A NOVEL PLANT IN THE SYNTHESIS OF SILVER NANOPARTICLES FOR BIOMEDICAL APPLICATIONS.

Objective: Synthesis of silver nanoparticles (AgNPs) using a simple, cost-effective and environmentally friendly green route approach and to study the antibacterial activity of AgNPs against human pathogens.Methods: Green route approach is used to synthesize AgNPs using Psidium guajava leaf extract. Fourier transform infrared (FTIR) was used to identify the presence of the functional group. X-ray diffraction (XRD) was used to analyze the structure of prepared AgNPs. Energy dispersive X-ray was used to the characteristic to the composition of the prepared nanoparticles. Size and morphology of the prepared AgNPs were investigated using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Antibacterials efficiency of prepared AgNPs was tested against Escherichia coli and Staphylococcus aureus by well diffusion methods.Results: FTIR study shows the presence of different functional groups present in the leaves mediated AgNPs. The XRD studies yield diffraction peaks corresponding to face-centered cubic structure of Ag crystals. Spherical shaped AgNPs with a particle size of about ~55 nm were evidenced using FESEM and TEM analysis. Energy dispersive spectrum of the synthesized AgNPs confirms the presence of silver in the prepared nanoparticles. From UV-VIS analysis it is shown that the absorption band was red-shifted from 430 nm to 456 nm. The prepared AgNPs shows good antibacterial activity against E. coli and S. aureus.Conclusions: P. guajava leaf extract is a potential reducing agent to synthesize AgNPs. The green synthesis approach provides cost-effective and eco-friendly nanoparticles, which could be used in biomedical applications.

PSIDIUM GUAJAVA: A NOVEL PLANT IN THE SYNTHESIS OF SILVER NANOPARTICLES FOR BIOMEDICAL APPLICATIONS.

Objective: Synthesis of silver nanoparticles (AgNPs) using a simple, cost-effective and environmentally friendly green route approach and to study the antibacterial activity of AgNPs against human pathogens.Methods: Green route approach is used to synthesize AgNPs using Psidium guajava leaf extract. Fourier transform infrared (FTIR) was used to identify the presence of the functional group. X-ray diffraction (XRD) was used to analyze the structure of prepared AgNPs. Energy dispersive X-ray was used to the characteristic to the composition of the prepared nanoparticles. Size and morphology of the prepared AgNPs were investigated using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Antibacterials efficiency of prepared AgNPs was tested against Escherichia coli and Staphylococcus aureus by well diffusion methods.Results: FTIR study shows the presence of different functional groups present in the leaves mediated AgNPs. The XRD studies yield diffraction peaks corresponding to face-centered cubic structure of Ag crystals. Spherical shaped AgNPs with a particle size of about ~55 nm were evidenced using FESEM and TEM analysis. Energy dispersive spectrum of the synthesized AgNPs confirms the presence of silver in the prepared nanoparticles. From UV-VIS analysis it is shown that the absorption band was red-shifted from 430 nm to 456 nm. The prepared AgNPs shows good antibacterial activity against E. coli and S. aureus.Conclusions: P. guajava leaf extract is a potential reducing agent to synthesize AgNPs. The green synthesis approach provides cost-effective and eco-friendly nanoparticles, which could be used in biomedical applications.

Role of Temperature on the Phase Modification of TiO2 Nanoparticles Synthesized by the Precipitation Method

Nanostructured TiO2 samples have been synthesized successfully by a simple precipitation method. The prepared samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), photoluminescence (PL) spectroscopy, ultra violet (UV) spectroscopy and Raman spectroscopy respectively. The as-prepared TiO2 nanoparticls appear to be a single anatase phase with average crystalline size 37.68 nm at 150 ∘C and found to be transformed from anatase to rutile phase during the annealing of samples in the temperature range from 150 ∘C to 600 ∘C. The TEM images indicate the particle sizes are in the range between 12 and 25 nm for anatase phase TiO2 at 400 ∘C and 30–45 nm for rutile phase TiO2 at 600 ∘C. The luminescence property of the TiO2 nanoparticles studied by the emission properties confirms the presence of defect levels caused by the oxygen vacancies. Raman spectroscopy was used to identify and quantity the amorphous and crystalline TiO2 phases. FTIR studies reveal weak complex vibrations between the titanium and oxygen species and also additional unsaturated sites (Ti3+) through incorporation of (OH) groups, not otherwise seen in bulk TiO2.

FTIR and Raman spectroscopic studies of selenium nanoparticles synthesised by the bacterium Azospirillum thiophilum

Vibrational (Fourier transform infrared (FTIR) and Raman) spectroscopic techniques can provide unique molecular-level information on the structural and compositional characteristics of complicated biological objects. Thus, their applications in microbiology and related fields are steadily increasing. In this communication, biogenic selenium nanoparticles (Se NPs) were obtained via selenite (SeO32−) reduction by the bacterium Azospirillum thiophilum (strain VKM B-2513) for the first time, using an original methodology for obtaining extracellular NPs. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed the Se NPs to have average diameters within 160–250nm; their zeta potential was measured to be minus 18.5mV. Transmission FTIR spectra of the Se NPs separated from bacterial cells showed typical proteinacious, polysaccharide and lipid-related bands, in line with TEM data showing a thin layer covering the Se NPs surface. Raman spectra of dried Se NPs layer in the low-frequency region (under 500cm−1 down to 150cm−1) showed a single very strong band with a maximum at 250cm−1 which, in line with its increased width (ca. 30cm−1 at half intensity), can be attributed to amorphous elementary Se. Thus, a combination of FTIR and Raman spectroscopic approaches is highly informative in non-destructive analysis of structural and compositional properties of biogenic Se NPs.

Evaluation of photosynthetic activities in thylakoid membranes by means of Fourier transform infrared spectroscopy

Light-induced Fourier transformed infrared (FTIR) difference spectroscopy is a powerful method to study the structures and reactions of redox cofactors involved in the photosynthetic electron transport chain. So far, most of the FTIR studies of the reactions of oxygenic photosynthesis have been performed using isolated photosystem I (PSI) and photosystem II (PSII) preparations, which, however, could be modified during isolation procedures. In this study, we developed a methodology to evaluate the photosynthetic activities of thylakoids using FTIR spectroscopy. FTIR difference spectra upon successive flashes using thylakoids from spinach exhibited signals typical of the S-state cycle at the Mn4CaO5 cluster and QB reactions in PSII with period-four and -two oscillations, respectively. Similar measurement in the presence of an artificial quinone as an exogenous electron acceptor showed features specific to the S-state cycle. Simulations of the oscillation patterns provided the quantum efficiencies of the S-state cycle and electron transfer in PSII. Moreover, FTIR measurement under continuous illumination on thylakoids in the presence of DCMU showed signals due to QA reduction and P700 oxidation simultaneously. From the relative amplitudes of marker bands of QA− and P700+, the molar ratio of photoactive PSII and PSI centers in thylakoids was estimated. FTIR analyses of the photo-reactions in thylakoids, which are more intact than isolated photosystems, will be useful in investigations of the photosynthetic mechanism especially by genetic modification of photosystem proteins.

Silver-controlled evolution of morphological, structural, and optical properties of three-dimensional hierarchical WO3 structures synthesized from hydrothermal method

Hierarchical structures of self-assembled three-dimensional (3D) WO3–Ag were synthesized via hydrothermal growth using precursor solutions of peroxopolytungstic acid with different amounts of Ag. The as-grown samples were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. The XRD and Raman studies showed that as the amount of Ag was varied from 0 to 10 wt% in the hydrothermal growth solution, the crystal phase gradually changed from orthorhombic WO3·0.33H2O to hexagonal WO3. The FTIR and TGA studies revealed different hydration levels, supporting the XRD and Raman results. By controlling the amount of Ag in the precursor solution, platelet-like building blocks and hexagonal building blocks were obtained, highlighting the role of Ag in the hydrothermal growth of 3D WO3·0.33H2O and WO3 microcrystals. In addition, high-magnification FESEM images showed that the Ag nanoparticles were anchored on the surface of the 3D hierarchical WO3–Ag structures, and the UV–vis measurements demonstrated that the 3D hierarchical structures gradually absorbed more light when the Ag content was increased. Moreover, the band-gap energy decreased when the Ag content was increased from 0 wt% (Eg = 2.65 eV) to 10 wt% (Eg = 2.26 eV). These experimental results demonstrate that the amount of Ag played a crucial role in determining the building blocks' morphology, and the hydration level, optical properties, and crystal phase of the WO3·nH2O microcrystals.

Synthesis and characterization of biogenic metal nanoparticles and its cytotoxicity and anti-neoplasticity through the induction of oxidative stress, mitochondrial dysfunction and apoptosis

In the present study, we demonstrate a simple, cost-effective and eco-friendly method for biogenic synthesis of silver nanoparticles (AgNPCGs) using ethanolic extract of Calotropis gigantea latex. Attempts were made to characterize these biogenic silver nanoparticles AgNPCGs and also to test its cytotoxic, anti-neoplastic and apoptotic potential through the induction of oxidative stress, mitochondrial dysfunction. AgNPCGs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS) and surface zeta potential measurement, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectrometry (EDX). UV visible spectroscopy showed an intense surface plasmon resonance band at 431nm which clearly reflected the formation of silver nanoparticles. FTIR study revealed that latex extract acted as reducing and stabilizing agent for the synthesis of AgNPCGs. Energy dispersive X-ray spectroscopy confirmed the presence of silver as a major component of synthesized AgNPCGs. SEM and TEM studies showed that the synthesized AgNPCGs were nearly spherical in shape with an average size of 2.338nm. The selected area electron diffraction pattern and XRD studies confirmed the crystalline nature of AgNPCGs. AgNPCGs exhibited in-vitro cytotoxic activity against Ehrlich’s ascites carcinoma (EAC), Jurkat and MCF-7 cells at respective IC50 doses without producing cytotoxicity to mice and human lymphocytes. Significant chromatin condensation, DNA fragmentation, cell cycle arrest at G2/M phase, up-regulation of Bax and caspase-3 and down-regulation of Bcl-2 were observed in AgNPCGs treated EAC cells. The results suggest that biogenic silver nanoparticles AgNPCGs could be a potential chemotherapeutic formulation for cancer therapy.

FT-IR studies of factors affecting the diffusivity of oligo (oxyethylene) fatty acid ester in PE films: Effect of temperature, ethylene oxide chain length and base resin type

A migration kinetics study of a series of oligo (oxyethylene) fatty acid esters of various chain lengths in polyethylene film was studied using Fourier transform infrared (FT-IR) spectroscopy. Diffusion coefficients (D) were determined as a function of temperature, ethylene oxide (EO) chain length and base resin type. The activation energy of diffusion (Ea) for each oligo (oxyethylene) fatty acid ester was determined using the Arrhenius plot of D dependence on inverse temperature. The correlation between obtained D and the number-averaged molecular weight Mn of oligo (oxyethylene) fatty acid ester was described well by a power law expression (D=bMn−a), and the parameters a and b were determined from experimental data. Two other models, which have the form of an Eyring expression, were derived to express the effects of temperature and EO chain length on the diffusion process of oligo (oxyethylene) fatty acid esters. Diffusivity of oligo (oxyethylene) fatty acid ester in linear low density polyethylene (LLDPE) was higher than in high density polyethylene (HDPE) and low density polyethylene (LDPE).

Fast and easy synthesis of novel Strontium apatite nanostructured phase: Structure, spectroscopy, and dielectric analysis

A simple and fast synthesis method of hydroxyapatite (Ca10(PO4)6(OH)2 (HAp) is presented in this study. By using fast microwave/hydrothermal synthesis technique, different concentrations of strontium doped HAp nanorods titled as (0.03, 0.06, 12, 0.24, 0.48) were prepared. The as-prepared Sr-doped HAp was characterized for its structure and morphology using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Spectroscopic properties were also enquired through Raman and Fourier transform infrared (FTIR) spectroscopy. The morphological studies by scanning electron microscopy showed the effective synthesis of HAp nanorods with different sizes. In addition, the dielectric properties of Sr-doped HAp were also studied by using dielectric impedance spectroscopy technique. Raman and FTIR study show an agreement with no shift in the peaks at the increasing concentrations of Sr in all Sr-HAp samples. PO4 peak was clearly seen in Raman and the basic HAp structure was revealed in all FTIR results at various concentrations of Sr. The study has been proved that mixing of diverse concentrations of Sr to the HAp matrix, can affect the degree of crystallinity of the synthesized samples. The crystallite sizes of pure HAp and with different concentrations of Sr dopped HAp were found to be 12 and 27nm. Moreover, doping of HAp with different concentration of Sr also affect the dielectric properties of the studied samples. This newly synthesized Sr-doped HAp can be applied in different biological applications such as bone and teeth cement engineering.

An FTIR Study of Kyanite in the Maobei Kyanite-Bearing Eclogites from the Sulu Orogenic Belt, Eastern China

As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure (UHP) metamorphism together with its host eclogites. Thus, it could play some role in transporting water into the deep earth. Here we present a detailed investigation of water concentrations of kyanite, and for reference, of garnet and omphacite from four Maobei eclogites in the Sulu orogenic belt, eastern China. Fourier transform infrared (FTIR) measurements show that kyanites, garnets, and omphacites all have distinct hydroxyl absorption bands due to OH groups bound in their crystal structure. The FTIR profile analyses on ten grains from different samples reveal a homogeneous distribution of water across kyanite, suggesting insignificant water loss during exhumation. The calculated water concentrations in kyanite (21 wt ppm–41 wt ppm) are comparable to those reported previously for kyanite from various geological occurrences when using the most recent calibration. They are however much lower compared with those in garnet (46 wt ppm–83 wt ppm) and omphacite (302 wt ppm–548 wt ppm) from the Maobei eclogites. This implies that kyanite is not a major water carrier in eclogites considering its low volume fraction and contributes negligibly to transport water into the deep mantle accompanying subducted oceanic crust until its possible transformation to AlSiO3OH.

Fe-MoS4: An Effective and Stable LDH-Based Adsorbent for Selective Removal of Heavy Metals.

It has always been a serious challenge to design efficient, selective, and stable absorbents for heavy-metal removal. Herein, we design layered double hydroxide (LDH)-based Fe-MoS4, a highly efficient adsorbent, for selective removal of heavy metals. We initially synthesized FeMgAl-LDH and then enriched its protective layers with MoS42- anions as efficient binding sites for heavy metals. Various characterization tools, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray, X-ray photoelectron spectroscopy (XPS), CHN analysis, and inductively coupled plasma analysis, were applied to confirm structural and compositional changes during the synthesis of Fe-MoS4 as final product. The prepared Fe-MoS4 offered excellent attraction for heavy metals, such as Hg2+, Ag+, Pb2+, and Cu2+, and displayed selectivity in the order Hg2+ ∼ Ag+ > Pb2+ > Cu2+ > Cr6+ > As3+ > Ni2+ ∼ Zn2+ ∼ Co2+. The immense capacities of Hg2+, Ag+, and Pb2+ (583, 565, and 346 mg/g, respectively), high distribution coefficient (Kd ∼ 107-108), and fast kinetics place Fe-MoS4 on the top of materials list known for removal of such metals. The sorption kinetics and isothermal studies conducted on Hg2+, Ag+, Pb2+, and Cu2+ suit well pseudo-second-order kinetics and Langmuir model, suggesting monolayer chemisorption mechanism through M-S linkages. XRD and FTIR studies suggested that adsorbed metals could result as coordinated complexes in LDH interlayer region. More interestingly, LDH structure offers protective space for MoS42- anions to avoid oxidation under ambient environments, as confirmed by XPS studies. These features provide Fe-MoS4 with enormous capacity, good reusability, and excellent selectivity even in the presence of huge concentration of common cations.

Study of CuO content on physical and structural properties of Li2O-B2O3-CuO glasses using electron paramagnetic resonance

Spectroscopic studies based on optical absorption, electron paramagnetic resonance (EPR), and Fourier transform infrared (FTIR) spectroscopy were performed to understand the effects of modifier oxides and CuO dopants in glass matrices. Glass with a composition of xLi2O-B2O3-yCuO was prepared with x fixed at 0.1 and y varied from 0.005 to 0.05. The optical absorption spectra were used to determine the absorption band, which was attributed to the 2B1g→2B2g characteristic transition of Cu2+ ions in the distorted octahedral sites. The values of the spin-Hamiltonian parameters determined by the EPR studies indicated that the site symmetry around the Cu2+ ions was a tetragonally distorted octahedral. The glasses for which y was greater than 0.02 exhibited bands caused by the Cu+ ions in the UV region. The EPR and optical absorption data were used to calculate the molecular orbital coefficients α2 and β12, and the FTIR studies showed that these glasses consisted of BO3 and BO4 units.

Accounting for the species-dependence of the 3500 cm−1H2Otinfrared molar absorptivity coefficient: Implications for hydrated volcanic glasses

Fourier transform infrared (FTIR) spectroscopy can be used to determine the concentration and speciation of dissolved water in silicate glasses if the molar absorptivity coefficients (e) are known. Samples that are thin and/or water-poor typically require the use of the mid-IR 3500 cm–1 total water (H2Ot) and 1630 cm–1 molecular water (H2Om) absorbance bands, from which hydroxyl water (OH) must be determined by difference; however, accurate determination of H2Ot and OH is complicated because e3500 varies with water speciation, which is not usually known a priori. We derive an equation that uses end-member e3500 values to find accurate H2Ot and OH concentrations from the 3500 cm–1 absorbance for samples where only the H2Om concentration need be known (e.g., from the 1630 cm–1 band). We validate this new species-dependent e3500 method against published data sets and new analyses of glass standards. We use published data to calculate new end-member e3500 values of e3500OH = 79 ± 11 and e3500H2Om = 49 ± 6 L/mol∙cm for Fe-bearing andesite and e3500OH = 76 ± 12 and e3500H2Om = 62 ± 7 L/mol∙cm for Fe-free andesite. These supplement existing end-member values for rhyolite and albite compositions. We demonstrate that accounting for the species-dependence of e3500 is especially important for hydrated samples, which contain excess H2Om, and that accurate measurement of OH concentration, in conjunction with published speciation models, enables reconstruction of original pre-hydration water contents. Although previous studies of hydrous silicate glasses have suggested that values of e decrease with decreasing tetrahedral cation fraction of the glass, this trend is not seen in the four sets of end-member e3500 values presented here. We expect that future FTIR studies that derive end-member e3500 values for additional compositions will therefore not only enable the species-dependent e3500 method to be applied more widely, but will also offer additional insights into the relationship between values of e and glass composition.

FTIR Analysis of a Light-driven Inward Proton-pumping Rhodopsin at 77 K.

Parvularcula oceani xenorhodopsin (PoXeR) is a light-driven inward proton pump that was discovered from deep ocean marine bacteria. PoXeR is categorized into the same family of Anabaena sensory rhodopsin (ASR) that functions as a photochromic sensor. In this study, we applied light-induced difference Fourier-transform infrared (FTIR) spectroscopy to PoXeR at 77 K, and the obtained spectra were compared with those of ASR. The structure and structural changes in the primary processes of PoXeR are common to all microbial rhodopsins. The red-shifted K formation (PoXeRK ) was accompanied by retinal photoisomerization from the all-trans to 13-cis form resulting in a distorted structure of the retinal. The observed hydrogen out-of-plane (HOOP) vibrations were sensitive to H/D exchange, indicating that the chromophore distortion by retinal isomerization is located near the Schiff base region in PoXeR. The hydrogen-bonding strength of the protonated Schiff base is similar between PoXeR and ASR, whose acceptor is presumably a water molecule. Unlike ASR, however, PoXeR contains strongly hydrogen-bonded water (O-D stretch at 2277 cm-1 in D2 O), which is also the case for outward proton pumps. The detailed structure, structural changes upon retinal photoisomerization, as well as functional correlation in PoXeR are discussed based on the present FTIR study.

‘Click’ polymer of carbon nanotubes for superhydrophobic glass and leather

Copper (I)-catalyzed 1,3-dipolar cycloaddition reaction of azide–alkyne is called a ‘click’ reaction. It is an adaptable tool for preparing multifunctional materials. In this paper, the authors report click polymerization of single-walled carbon nanotubes (SWCNTs) with thiophene/aryl compounds and their electronic/spectroscopic properties and applications. The various spectroscopic and microscopic studies (Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, nuclear magnetic resonance and ultraviolet–visible) confirmed the success of the polymerization. The superhydrophobicity of the materials was studied by contact angle measurement. The FT-IR studies indicated the disappearance of azide residues in the polymeric products, and the Raman studies exhibited a high degree of covalent functionalization of SWCNTs. The XPS data show the presence of polymeric elements in the click copolymer of SWCNTs. Dynamic light scattering studies confirmed the broad size distribution of the materials. Moreover, the thermogravimetric analysis revealed the high thermal stability of the polymer. Finally, wettability measurements of leather and glass surfaces after coating with the copolymer of SWCNTs show high water contact angles of 155 and 163°, respectively. The results were well reproduced, and these superhydrophobic characteristics indicate the material’s efficiency for designing various superhydrophobic surfaces.