Showing papers on "Infrared spectroscopy published in 2009"
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16 Mar 2009TL;DR: In this paper, the authors present a combination table of C NMR Spectroscopy, H NMR and Heteronuclear NMR spectroscopy with IR and Mass Spectrometry.
Abstract: Summary Tables.- Combination Tables.- C NMR Spectroscopy.- H NMR Spectroscopy.- Heteronuclear NMR Spectroscopy.- IR Spectroscopy.- Mass Spectrometry.- UV/Vis Spectroscopy.
2,180 citations
TL;DR: In this article, the results of the elemental analysis with that obtained by different spectroscopic techniques (infrared and Raman spectroscopy, and XPS) have been inferred that, from a chemical point of view, the solid product consists of small clusters of condensed benzene rings that form stable groups with oxygen in the core.
1,526 citations
TL;DR: In this article, the synthesis and Fourier Transform Infrared spectroscopy characterization results dealing with the surface modification of silica aerogels obtained via a two-step sol-gel process where various silicon precursors and co-precursors were used.
715 citations
TL;DR: In this article, a study of the structure and bonding configuration of sol-gel silicate glasses by Raman and infrared spectroscopies is presented, and a review of the Raman lines and infrared bands assignment, the identification of the non-bridging silicon-oxygen groups and the ring structures are also demonstrated.
Abstract: A study of the structure and bonding configuration of sol–gel silicate glasses by Raman and infrared spectroscopies is presented. Moreover, a review of the Raman lines and infrared bands assignment, the identification of the non-bridging silicon–oxygen groups and the ring structures are also demonstrated. The evolution of the changes of the bonding configuration in the composition and the stabilization temperature of the bioactive glasses is discussed in terms of the structural and textural characteristics of the glasses. Raman and infrared analyses contribute to the improvement in understanding of the local symmetry for sol–gel silicate glasses. infrared spectroscopy has allowed to identify the vibration bands of the hydroxyl groups associated with various configurations of the terminal silanol bonds on the glass surface and the free molecular water in the glass matrix. Raman analysis has provided an alternative method of quantifying the network connectivity grade and predicting the textural properties of the sol–gel silicate glasses.
495 citations
TL;DR: New spectroscopic and microscopic techniques have been developed that operate under reaction conditions and reveal the dynamic change of molecular structure of catalysts and adsorbed molecules as the reactions proceed with changes in reaction intermediates, catalyst composition, and oxidation states.
Abstract: The challenge of chemistry in the 21st century is to achieve 100% selectivity of the desired product molecule in multipath reactions (“green chemistry”) and develop renewable energy based processes. Surface chemistry and catalysis play key roles in this enterprise. Development of in situ surface techniques such as high-pressure scanning tunneling microscopy, sum frequency generation (SFG) vibrational spectroscopy, time-resolved Fourier transform infrared methods, and ambient pressure X-ray photoelectron spectroscopy enabled the rapid advancement of three fields: nanocatalysts, biointerfaces, and renewable energy conversion chemistry. In materials nanoscience, synthetic methods have been developed to produce monodisperse metal and oxide nanoparticles (NPs) in the 0.8−10 nm range with controlled shape, oxidation states, and composition; these NPs can be used as selective catalysts since chemical selectivity appears to be dependent on all of these experimental parameters. New spectroscopic and microscopic te...
479 citations
TL;DR: In this article, the gamma, delta, theta and alpha-Al{sub 2}O{sub 3} phases, prepared by dehydration of aluminium oxihydroxide AlOOH (boehmite), were measured by XRD and IR spectroscopy on all samples.
428 citations
TL;DR: In this paper, the thermal stability of graphite oxides to heat treatment under ambient argon gas was investigated using X-ray diffraction, and it was found that the interlayer distances dropped off in a stepwise manner by approximately 0.1nm in relation to the annealing time.
416 citations
TL;DR: It will be shown that IR spectroscopy of mass-selected (bio)molecular systems is now well-placed to address specific questions on the individual effect of charge carriers (protons and metal ions), as well as solvent molecules on the overall structure.
Abstract: The low density of ions in mass spectrometers generally precludes direct infrared (IR) absorption measurements. The IR spectrum of an ion can nonetheless be obtained by inducing photodissociation of the ion using a high-intensity tunable laser. The emergence of free electron lasers (FELs) and recent breakthroughs in bench-top lasers based on nonlinear optics have now made it possible to routinely record IR spectra of gas-phase ions. As the energy of one IR photon is insufficient to cause dissociation of molecules and strongly bound complexes, two main experimental strategies have been developed to effect photodissociation. In infrared multiple-photon dissociation (IR-MPD) many photons are absorbed resonantly and their energy is stored in the bath of vibrational modes, leading to dissociation. In the "messenger" technique a weakly bound van der Waals atom is detached upon absorption of a single photon. Fundamental, historical, and practical aspects of these methods will be presented. Both of these approaches make use of very different methods of ion preparation and manipulation. While in IR-MPD ions are irradiated in trapping mass spectrometers, the "messenger" technique is generally carried out in molecular beam instruments. The main focus of this review is the application of IR spectroscopy to biologically relevant molecular systems (amino acids, peptides, proteins). Particular issues that will be addressed here include gas-phase zwitterions, the (chemical) structures of peptides and their collision-induced dissociation (CID) products, IR spectra of gas-phase proteins, and the chelation of metal-ligand complexes. Another growing area of research is IR spectroscopy on solvated clusters, which offer a bridge between the gas-phase and solution environments. The development of state-of-the-art computational approaches has gone hand-in-hand with advances in experimental techniques. The main advantage of gas-phase cluster research, as opposed to condensed-phase experiments, is that the systems of interest can be understood in detail and structural effects can be studied in isolation. It will be shown that IR spectroscopy of mass-selected (bio)molecular systems is now well-placed to address specific questions on the individual effect of charge carriers (protons and metal ions), as well as solvent molecules on the overall structure.
395 citations
TL;DR: All conditions seem joined to make FTIR spectroscopy and imaging major tools for implementing innovative methods in the field of molecular histology, which would be very helpful for the diagnosis of a wide range of pathologies.
Abstract: Abnormal formation and organization of collagen network is commonly observed in many organ pathologies, but analytical techniques able to reveal the collagen biodistribution are still lacking. In this study, Fourier-transform infrared (FTIR) spectroscopy has been used to analyze type I, III, IV, V, and VI collagens, the most important compounds of connective tissues. A robust classification of 30 FTIR spectra per collagen type could be obtained by using a combination of four spectral intervals [nu(C=O) absorption of amide I (1,700-1,600 cm(-1)), delta(CH(2)), and delta(CH(3)) absorptions (1,480-1,350 cm(-1)), nu(C-N), and delta(N-H) absorptions of amide III (1,300-1,180 cm(-1)), and nu(C-O) and nu(C-O-C) absorptions of carbohydrate moieties (1,100-1,005 cm(-1))]. Then, a submolecular justification of this classification model was sought using a curve fitting analysis of the four spectral intervals. Results demonstrated that every spectral interval used for the classification contained highly discriminant absorption bands between all collagen types (multivariate analysis of variance, p < 0.01; Dunnett's T3 post hoc test, p < 0.05). All conditions seem thus joined to make FTIR spectroscopy and imaging major tools for implementing innovative methods in the field of molecular histology, which would be very helpful for the diagnosis of a wide range of pathologies.
384 citations
TL;DR: The aim of this paper is to provide an overview of the methods for collecting 2D spectra so that an outsider considering using2D spectroscopy in their own research can judge which approach would be most suitable for their research aims.
Abstract: We have recently developed a new and simple way of collecting 2D infrared and visible spectra that utilizes a pulse shaper and a partly collinear beam geometry. 2D IR and Vis spectroscopies are powerful tools for studying molecular structures and their dynamics. They can be used to correlate vibrational or electronic eigenstates, measure energy transfer rates, and quantify the dynamics of lineshapes, for instance, all with femtosecond time-resolution. As a result, they are finding use in systems that exhibit fast dynamics, such as sub-millisecond chemical and biological dynamics, and in hard-to-study environments, such as in membranes. While powerful, these techniques have been difficult to implement because they require a series of femtosecond pulses to be spatially and temporally overlapped with precise time-resolution and interferometric phase stability. However, many of the difficulties associated with implementing 2D spectroscopies are eliminated by using a pulse shaper and a simple beam geometry, which substantially lowers the technical barriers required for researchers to enter this exciting field while simultaneously providing many new capabilities. The aim of this paper is to provide an overview of the methods for collecting 2D spectra so that an outsider considering using 2D spectroscopy in their own research can judge which approach would be most suitable for their research aims. This paper focuses primarily on 2D IR spectroscopy, but also includes our recent work on adapting this technology to collecting 2D Vis spectra. We review work that has already been published as well as cover several topics that we have not reported previously, including phase cycling methods to remove background signals, eliminate unwanted scatter, and shift data collection into the rotating frame.
363 citations
TL;DR: Solid-state NMR spectra unequivocally demonstrate the presence of the guest species, as well as the successful postsynthetic functionalization of the MIL-53, which leads to a porous compound that exhibits hysteresis behavior in the N(2) sorption experiments.
Abstract: Aluminum aminoterephthalate Al(OH)[H2N−BDC]·0.3(H2N−H2BDC (denoted MIL-53−NH2(as)) was synthesized under hydrothermal conditions. The activation of the compound can be achieved in two steps. The treatment with DMF at 150 °C leads to Al(OH)[H2N−BDC]·0.95DMF (MIL-53−NH2(DMF)). In the second step, DMF is thermally removed at 130 °C. Upon cooling in air, the hydrated form Al(OH)[H2N−BDC]·0.9H2O (MIL-53−NH2(lt)) is obtained. The dehydration leads to a porous compound that exhibits hysteresis behavior in the N2 sorption experiments. The MIL-53−NH2(lt) can be modified by postsynthetic functionalization using formic acid, and the corresponding amide Al(OH)[HC(O)N(H)−BDC]·H2O (MIL-53−NHCHO) is formed. All four phases were thoroughly characterized by X-ray powder diffraction, solid-state NMR and IR spectroscopy, and sorption measurements, as well as thermogravimetric and elemental analysis. Based on the refined lattice parameter similar breathing behavior of the framework as found in the unfunctionalized MIL-53 can...
TL;DR: In this paper, the adsorption and inhibition effect of 6-benzylaminopurine (BAP) on cold rolled steel (CRS) was studied by weight loss and potentiodynamic polarization methods.
TL;DR: In this paper, a nonlinear optical (NLO) crystal BaGa4S7 for the mid-infrared (IR) has been grown by a Bridgman-Stockbarger technique.
Abstract: The new nonlinear optical (NLO) crystal BaGa4S7 for the mid-infrared (IR) has been grown by a Bridgman-Stockbarger technique. Polycrystalline materials with stoichiometric composition were synthesized from BaS, Ga, and S as the initial materials by solid-state reactions. The ultraviolet (UV) and IR transmittance of the crystal was determined with polished crystal pieces. The UV and IR optical absorption edges were found to be at 350 nm and 13.7 μm, respectively. From optical measurements of second harmonic generation on powders, the NLO coefficient d33 was determined to be 12.6 pm/V. The laser damage threshold of a single crystal reached about 1.2 J/cm2 at 1.064 μm. The Vickers-hardness value of the crystal is 327.5 HV5, which is equivalent to Mohs’ hardness of about 5.
TL;DR: In this paper, a review presents a number of techniques employed in our laboratory and in others for measuring the spectroscopy of cold, gas-phase protonated peptides.
Abstract: While the marriage of mass spectrometry and laser spectroscopy is not new, developments over the last few years in this relationship have opened up new horizons for the spectroscopic study of biological molecules. The combination of electrospray ionisation for producing large biological molecules in the gas phase together with cooled ion traps and multiple-resonance laser schemes are allowing spectroscopic investigation of individual conformations of peptides with more than a dozen amino acids. Highly resolved infrared spectra of single conformations of such species provide important benchmarks for testing the accuracy of theoretical calculations. This review presents a number of techniques employed in our laboratory and in others for measuring the spectroscopy of cold, gas-phase protonated peptides. We show examples that demonstrate the power of these techniques and evaluate their extension to still larger biological molecules.
TL;DR: In this article, the authors used laser frequency combs as the light source of Fourier transform spectroscopy (FTS) to record well-resolved broadband absorption and dispersion spectra in a single experiment.
Abstract: Molecular fingerprinting using absorption spectroscopy is a powerful analytical method, particularly in the infrared, the region of intense spectral signatures Fourier transform spectroscopy—the widely used and essential tool for broadband spectroscopy—enables the recording of multi-octave-spanning spectra, exhibiting 100 MHz resolution with an accuracy of 1 × 10−9 and 1 × 10−2 in wavenumber and intensity determination, respectively Typically, 1 × 106 independent spectral elements may be measured simultaneously within a few hours, with only average sensitivity Here, we show that by using laser frequency combs as the light source of Fourier transform spectroscopy it is possible to record well-resolved broadband absorption and dispersion spectra in a single experiment, from the beating signatures of neighbouring comb lines in the interferogram The sensitivity is thus expected to increase by several orders of magnitude Experimental proof of principle is here carried out on the 15-µm overtone bands of acetylene, spanning 80 nm with a resolution of 15 GHz Consequently, without any optical modification, the performance of Fourier spectrometers may be drastically boosted By using an optical frequency comb as the light source for Fourier transform spectroscopy, scientists show that well-resolved broadband absorption and dispersion spectra can be recorded in a single experiment, providing sensitive detection of multiple molecular species over a broad spectral window
TL;DR: This review summarises recent advances in vibrational spectroscopy and their impact on the diagnosis of cancer and illustrates the complementary advantage of using Raman and FTIR spectroscopic technologies together.
Abstract: Vibrational spectroscopy techniques have demonstrated potential to provide non-destructive, rapid, clinically relevant diagnostic information. Early detection is the most important factor in the prevention of cancer. Raman and infrared spectroscopy enable the biochemical signatures from biological tissues to be extracted and analysed. In conjunction with advanced chemometrics such measurements can contribute to the diagnostic assessment of biological material. This paper also illustrates the complementary advantage of using Raman and FTIR spectroscopy technologies together. Clinical requirements are increasingly met by technological developments which show promise to become a clinical reality. This review summarises recent advances in vibrational spectroscopy and their impact on the diagnosis of cancer.
TL;DR: In this article, the effect of oxygen mobility on the bio-ethanol steam reforming of ZrO2-supported cobalt catalysts was investigated, and it was found that the addition of ceria was found to improve the catalytic stability as well as activity.
TL;DR: Graphene nanoplatelets were self-assembled through the layer-by-layer (LBL) method through electrostatic interaction and Ultraviolet-visible spectroscopy confirmed that the adsorption technique resulted in uniform film growth.
Abstract: In this report, graphene nanoplatelets were self-assembled through the layer-by-layer (LBL) method The graphene surface was modified with poly(acrylic acid) and poly(acryl amide) by covalent bonding, which introduced negative and positive charge on the surface of graphene, respectively Through electrostatic interaction, the positively and negatively charged graphene nanoplatelets assembled together to form a multilayer structure Thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy were used to demonstrate the modification of graphene nanoplatelets Fourier transform infrared spectroscopy and SEM proved this method is feasible for preparing graphene-containing films Ultraviolet−visible spectroscopy confirmed that the adsorption technique resulted in uniform film growth
01 Jan 2009
TL;DR: F Fourier transform infrared spectroscopy (FTIR) and ellipsometry have shown that the structure and thickness of APTES films are governed by the deposition time and reaction solution, and films prepared in toluene solutions contain more reactive surface amino groups.
Abstract: Amino-functionalized organic films were prepared by self-assembling 3-aminopropyltriethoxysilane (APTES) on silicon wafers in either anhydrous toluene or phosphate-buffered saline (PBS) for varied deposition times. Fourier transform infrared spectroscopy (FTIR) and ellipsometry have shown that the structure and thickness of APTES films are governed by the deposition time and reaction solution. Deposition from an anhydrous toluene solution produces APTES films ranging from 10 to 144 A in thickness, depending on the reaction time. FTIR spectra indicate that film growth initially proceeds by adsorption of APTES to the silicon surface followed by siloxane condensation, and after an extended period of time APTES molecules accumulate on the underlying APTES film by either covalent or noncovalent interactions. In contrast, spectroscopically indistinguishable APTES films in thickness ranging from 8 to 13 A were formed when deposition was conducted in aqueous solutions. Measured water contact angles indicate that APTES films deposited in aqueous solutions are more hydrophilic compared to those prepared in toluene solutions. Fluorescence measurements revealed that APTES films prepared in toluene solutions contain more reactive surface amino groups by ca. 3 to 10 times than those prepared in aqueous solutions for the identical reaction time.
TL;DR: This short review of vibrational spectroscopic advances in microbial identification of yeast and bacterial cells for bulk environment and single‐cell analysis is discussed.
Abstract: Rapid microbial detection and identification with a high grade of sensitivity and selectivity is a great and challenging issue in many fields, primarily in clinical diagnosis, pharmaceutical, or food processing technology. The tedious and time-consuming processes of current microbiological approaches call for faster ideally on-line identification techniques. The vibrational spectroscopic techniques IR absorption and Raman spectroscopy are noninvasive methods yielding molecular fingerprint information; thus, allowing for a fast and reliable analysis of complex biological systems such as bacterial or yeast cells. In this short review, we discuss recent vibrational spectroscopic advances in microbial identification of yeast and bacterial cells for bulk environment and single-cell analysis. IR absorption spectroscopy enables a bulk analysis whereas micro-Raman-spectroscopy with excitation in the near infrared or visible range has the potential for the analysis of single bacterial and yeast cells. The inherently weak Raman signal can be increased up to several orders of magnitude by applying Raman signal enhancement methods such as UV-resonance Raman spectroscopy with excitation in the deep UV region, surface enhanced Raman scattering, or tip-enhanced Raman scattering. © 2008 International Society for Advancement of Cytometry
TL;DR: The infrared spectra (IR) of pure liquid light and heavy water were obtained with attenuated total reflection (ATR) and transmission measurements in the mid-IR and far-IR with new optical properties (n and k) that can now be used as standards for liquid H(2)O and D( 2)O.
Abstract: The infrared spectra (IR) of pure liquid light (H(2)O) and heavy (D(2)O) water were obtained with attenuated total reflection (ATR) and transmission measurements in the mid-IR and far-IR. With these and with other values obtained from the literature, the real (n) and imaginary parts (k) of the refractive index were meticulously derived in the complete IR region from 6000 to 0 cm(-1). The reliability of the results resides in the critical comparison of our experimental data with that obtained from other laboratories and between calculated and experimental spectra, obtained by ATR and transmission techniques. The new optical properties (n and k) can now be used as standards for liquid H(2)O and D(2)O. To these we have added the water (H and D) absorption coefficients (K) that are derived from the k values. These can be used as references for spectra obtained by transmission with an absorbance intensity scale because they are almost the same.
TL;DR: In this paper, the catalytic properties of Au nanoclusters deposited on a 1-D nanorod and CeO2-nanoparticles have been investigated during CO oxidation at ambient temperatures.
Abstract: Catalytic properties of Au nanoclusters deposited on a one-dimensional CeO2 (1-D) nanorod and CeO2-nanoparticles have been investigated during CO oxidation at ambient temperatures. The kinetic data showed that the activity of Au catalysts could be remarkably improved by using CeO2-nanorods as support compared to the CeO2-nanoparticles. The measured specific rate and apparent activation energy (Ea) at 278 K were 4.02 molCO gAu−1 h−1 and 15.9 kJ mol−1, respectively, for the Au/CeO2-nanorods (Au-CR) catalyst, while those for the Au/CeO2-nanoparticles (Au-CP) catalyst were 0.15 molCO gAu−1 h−1 and 28.4 kJ mol−1, respectively. Characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–Vis spectroscopy (DR UV–Vis) and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) of CO adsorption reveal that the predominantly exposed {1 0 0}/{1 1 0}-dominated surface structures of ceria nanorods show great superiority for anchoring and dispersing of gold nanoclusters, which in turn leads to a higher reducibility and activity of the Au-CeO2 surface for CO oxidation. It is also confirmed that, arising from the strong metal–support interaction (SMSI), the presence of gold nanoclusters has a strong influence on the electronic state of the CeO2 substrates.
TL;DR: In this article, the structure of the organic capping layers of platinum colloid nanoparticles and their removal by UV-ozone exposure were reported, and the overall shape of the nanoparticles was preserved after the removal of capping layer.
Abstract: We report the structure of the organic capping layers of platinum colloid nanoparticles and their removal by UV-ozone exposure. Sum frequency generation vibrational spectroscopy (SFGVS) studies identify the carbon-hydrogen stretching modes on poly(vinylpyrrolidone) (PVP) and tetradecyl tributylammonium bromide (TTAB)-capped platinum nanoparticles. We found that the UV-ozone treatment technique effectively removes the capping layer on the basis of several analytical measurements including SFGVS, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The overall shape of the nanoparticles was preserved after the removal of capping layers, as confirmed by transmission electron microscopy (TEM). SFGVS of ethylene hydrogenation on the clean platinum nanoparticles demonstrates the existence of ethylidyne and di-σ-bonded species, indicating the similarity between single-crystal and nanoparticle systems.
TL;DR: This compound is isostructural to the MIL-53 type, previously observed with the trivalent cations Cr, Fe, Al, In and exhibits a three-dimensional metal-organic framework built up from infinite chains of trans corner-sharing GaO(4)(OH)(2) octahedra (viamu(2)-hydroxo bonds) linked to each other through the terephthalate linkers.
Abstract: The gallium terephthalate Ga(OH)[O2C-C6H4-CO2]·xA (A = HO2C–C6H4–CO2H) was hydrothermally synthesized in water under mild conditions (210 °C, 3½ h) in the presence of terephthalic acid. The compound was characterized by powder X-ray diffraction, TGA, IR and BET method. This compound is isostructural to the MIL-53 type, previously observed with the trivalent cations Cr, Fe, Al, In. It exhibits a three-dimensional metal–organic framework built up from infinite chains of trans corner-sharing GaO4(OH)2 octahedra (viaμ2-hydroxo bonds) linked to each other through the terephthalate linkers. It results in the formation of lozenge-shape channels structure running parallel to the infinite files of gallium-centered octahedra. After activation, the compound is able to adsorb one molar equivalent of water at room temperature under ambient air (MIL-53(Ga){H2O}). Different hydrogen bond interactions are observed for the encapsulated water within the channels. In one tunnel, pairs of water species with strong hydrogen-bond interactions were observed whereas in the adjacent tunnel, only a continuous linear and weakly hydrogen bonded network occurs. The dehydrated form is obtained upon heating the MIL-53(Ga) solid at 80 °C together with the shrinkage of the channels (MIL-53(Ga)_lt. This form is stable up to 220 °C and then the open structure MIL-53(Ga)_ht is visible, but starts to decompose from 350 °C. Such a breathing effect was previously reported with cations such as Cr or Al but in the case of Ga, the stability domain of the narrow pore structure MIL-53(Ga)_lt is larger (160 °C instead of 20–30 °C for Al, for instance). The BET surface area was 1140 ± 114 m2.g−1. The phase transitions were characterized by IR spectroscopy at different temperatures, which confirms the stability domain of the narrow close form (specific band at 1016 cm−1) of MIL-53(Ga) and then the pore opening (shifted band toward 1024 cm−1) together with the structure collapse. An identical behaviour is also discussed for the aluminum MIL-53 analogue. A comparison between the behaviour of the Al, Ga and Fe samples is presented.
TL;DR: A network of hydrogen bonds involving O6 is proposed that can explain the main features of the polarized FTIR spectra of alpha- chitin and sheds some light on the origin of splitting of the amide I band observed on alpha-chitin IR spectra.
TL;DR: In this article, the role of divalent cations in the structure of B2O3 glasses has been investigated using sound velocity measurements at 4 MHz and IR spectroscopic analysis of IR spectra.
Abstract: Studies on xRO · 30Bi2O3 · (70−x)B2O3 glasses have been carried out (0 ⩽ x ⩽ 30 mol%, R = Zn, Ba). Elastic properties and Debye temperature have been investigated using sound velocity measurements at 4 MHz. The ultrasonic parameters along with the IR spectroscopic studies have been employed to explore the role of divalent cations in the structure of the studied glasses. Analysis of infrared spectra indicates that RO is preferentially incorporated into the borate network, forming BO4 units. It is assumed that Bi2O3 enters the structure in the form of BiO6 only. The change of density and molar volume with RO content reveals that BO4 units linked to R2+ cations are denser than those linked to positive sites in the Bi2O3 network. Predicted values of four co-ordinated boron put forward questions about the reliability of assignment of structural units that Bi2O3 may form.
TL;DR: In this paper, the degree of substitution (DS) was determined by a colorimetric method using the Raman and Fourier transform infrared spectra of the native and modified polysaccharides of cellulose, guar gum, locust bean gum and xanthan gum.
TL;DR: In this paper, the mechanism of hydrogen evolution by a core/shell noble-metal/Cr2O3 particulate as a highly efficient cocatalyst for overall water splitting under visible light using the photocatalyst (Ga1−xZnx)(N 1−xOx) is investigated by electrochemical and in situ spectroscopic measurements of model electrodes.
Abstract: The mechanism of hydrogen evolution by a core/shell noble-metal/Cr2O3 particulate as a highly efficient cocatalyst for overall water splitting under visible light using the photocatalyst (Ga1−xZnx)(N1−xOx) is investigated by electrochemical and in situ spectroscopic measurements of model electrodes. The electrodes are prepared by electrochemical deposition of 1.8−3.5 nm thick Cr2O3 films on Rh and Pt plates and are evaluated as model systems of Rh/Cr2O3 and Pt/Cr2O3 core/shell particulates, which have previously been applied effectively as cocatalysts for hydrogen evolution in this system. Proton adsorption/desorption and H2 evolution currents are observed for both the Cr2O3-coated and the bare electrodes, and the infrared absorption band due to Pt−H stretching (2039 cm−1) is apparent for both the coated and the bare electrodes. These observations indicate that the Cr2O3 layer does not interfere with proton reduction or hydrogen evolution and that proton reduction takes place at the Cr2O3/Pt interface. Ho...
TL;DR: An effort has been made to review the available literature information on the DA determination for chitin and chitosan using IR and NMR spectroscopy methods, which provide a number of advantages.
Abstract: Chitin, chitosan, and their derivatives have been identified as versatile biopolymers for a broad range of agriculture and food applications. Up to now, several methods have been developed to determine degree of N-acetylation, DA, for chitin and chitosan. In this article, an effort has been made to review the available literature information on the DA determination. These methods are classified into three categories: (1) spectroscopy (IR, (1)H NMR, (13)C NMR, (15)N NMR, and UV); (2) conventional (various types of titration, conductometry, potentiometry, ninhydrin assay, adsorption of free amino groups of chitosan by pictric acid); (3) destructive (elemental analysis, acid or enzymatic hydrolysis of chitin/chitosan and followed by the DA measurement by colorimetry or high performance liquid chromatography, pyrolysis-gas chromatography, and thermal analysis using differential scanning calorimetry) methods. These methods have been compared for their performances and limitations as well as their advantages and disadvantages. The use of IR and NMR spectroscopy methods provides a number of advantages. They do not need long-term procedures to prepare samples, and they provide information on the chemical structure. (1)H NMR and UV techniques are more sensitive than IR, (13)C NMR, and (15)N NMR spectroscopy. The IR technique is mostly used for a qualitative evaluation and comparison studies. Conventional methods are not applicable for highly acetylated chitin. The results of the latter methods are affected by ionic strength of the solvent, pH, and temperature of solution. In destructive methods, longer times are needed for the measurements compared to spectroscopy and conventional methods, but they are applicable for the entire range of the DA.
TL;DR: The new and exciting techniques of infrared consequence spectroscopy of gaseous ions are reviewed and this review mainly covers the topics with which the author has been directly involved in research: structures of proton-bound dimers, protonated amino acids and DNA bases, amino acid andDNA bases bound to metal ions and, more recently, solvated ionic complexes.
Abstract: In this article, the new and exciting techniques of infrared consequence spectroscopy (sometimes called action spectroscopy) of gaseous ions are reviewed. These techniques include vibrational predissociation spectroscopy and infrared multiple photon dissociation spectroscopy and they typically complement one another in the systems studied and the information gained. In recent years infrared consequence spectroscopy has provided long-awaited direct evidence into the structures of gaseous ions from organometallic species to strong ionic hydrogen bonded structures to large biomolecules. Much is being learned with respect to the structures of ions without their stabilizing solvent which can be used to better understand the effect of solvent on their structures. This review mainly covers the topics with which the author has been directly involved in research: structures of proton-bound dimers, protonated amino acids and DNA bases, amino acid and DNA bases bound to metal ions and, more recently, solvated ionic complexes. It is hoped that this review reveals the impact that infrared consequence spectroscopy has had on the field of gaseous ion chemistry.