Showing papers on "Infrared spectroscopy published in 2011"
TL;DR: In this article, the role of trapped water and the evolution of oxygen during annealing of reduced graphene oxide (GO) is investigated, and the interactions between randomly arranged nearby oxygen species are found to affect the spectral response (red and blue shifts) and the overall chemistry during the reduction process.
Abstract: Understanding the thermal reduction of graphene oxide (GO) is important for graphene exfoliation, and chemical and morphological modifications. In this process, the role of trapped water and the evolution of oxygen during annealing are still not well-understood. To unravel the complex mechanisms leading to the removal of oxygen in reduced GO, we have performed in situ transmission infrared absorption spectroscopy measurements of GO films upon thermal annealing at 60–850 °C in vacuum (10–3–10–4 Torr). Using cluster-based first-principles calculations, epoxides, ethers (pyrans and furans), hydroxyls, carboxyls, lactols, and various types of ketones and their possible derivatives have been identified from the spectroscopic data. Furthermore, the interactions between randomly arranged nearby oxygen species are found to affect the spectral response (red and blue shifts) and the overall chemistry during annealing. For instance, the initial composition of oxygen species (relative amounts and types of species, su...
767 citations
TL;DR: In this article, six commonly used wet chemical oxidants were evaluated in terms of their effects on the surface chemistry and structure of MWCNTs using a combination of analytical techniques, including X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrograph (EDX).
627 citations
01 Jan 2011
TL;DR: In this paper, the authors introduce how both mid-infrared (mid-IR) and Raman spectroscopy provide characteristic fundamental vibrations that are employed for the elucidation of molecular structure.
Abstract: This chapter introduces how both mid-infrared (mid-IR) and Raman spectroscopy provide characteristic fundamental vibrations that are employed for the elucidation of molecular structure. Mid-IR, near-IR, and Raman spectroscopy are part of vibrational spectroscopy. Raman spectroscopy is best at symmetric vibrations of nonpolar groups while IR spectroscopy is best at the asymmetric vibrations of polar groups. Infrared and Raman spectroscopy involve the study of the interaction of radiation with molecular vibrations but differ in the manner in which photon energy is transferred to the molecule by changing its vibrational state. IR spectroscopy measures transitions between molecular vibrational energy levels as a result of the absorption of mid-IR radiation. The IR and Raman vibrational bands are characterized by their frequency (energy), intensity, and band shape (environment of bonds). The frequencies of these molecular vibrations depend on the masses of the atoms, their geometric arrangement, and the strength of their chemical bonds. Two different approaches are used for the interpretation of vibrational spectroscopy and elucidation of molecular structure. The first approach is the use of group theory with mathematical calculations of the forms and frequencies of the molecular vibrations, and the second approach is the use of empirical characteristic frequencies for chemical functional groups. IR spectroscopy was the first structural spectroscopic technique widely used by organic chemists. An extensive user base resulted in a great increase in available IR interpretation tools and the eventual development of FT-IR instrumentation.
600 citations
TL;DR: In this article, a group of par- ticipants from 11 institutions in different countries recorded the FTIR spectra of PANI bases prepared from the samples obtained in the solutions of strong and weak acids and in alkaline medium within the framework of an IUPAC project.
Abstract: Polyaniline (PANI), a conducting polymer, was prepared by the oxidation of ani- line with ammonium peroxydisulfate in various aqueous media When the polymerization was carried out in the solution of strong (sulfuric) acid, a granular morphology of PANI was obtained In the solutions of weak (acetic or succinic) acids or in water, PANI nanotubes were produced The oxidation of aniline under alkaline conditions yielded aniline oligomers Fourier transform infrared (FTIR) spectra of the oxidation products differ A group of par- ticipants from 11 institutions in different countries recorded the FTIR spectra of PANI bases prepared from the samples obtained in the solutions of strong and weak acids and in alkaline medium within the framework of an IUPAC project The aim of the project was to identify the differences in molecular structure of PANI and aniline oligomers and to relate them to supramolecular morphology, viz the nanotube formation The assignment of FTIR bands of aniline oxidation products is reported
491 citations
TL;DR: In this article, the effect of treatment temperatures on the acidity of multi-walled carbon nanotubes (MWCNTs) was studied and Fourier transform infrared absorption spectroscopy (FTIR) was used for qualitative characterization.
455 citations
TL;DR: In this article, a novel hydrothermal approach is developed for the first time to synthesize hierarchical BiVO4/Bi2O2CO3 nanocomposites with reactive crystalline facets using urea as a morphology mediator.
Abstract: A novel hydrothermal approach is developed for the first time to synthesize hierarchical BiVO4/Bi2O2CO3 nanocomposites with reactive crystalline facets using urea as a morphology mediator. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, N2 absorption–desorption isotherms and UV–visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated towards degradation of Rhodomine B (RhB) by visible-light. Our results indicate that both physical parameters and associated photocatalytic activity of BiVO4/Bi2O2CO3 nanocomposites can be tuned by urea concentration and reaction time in the synthesis process. With increasing urea concentration, the specific surface area, pore volume and average pore size increase. Compared to BiVO4 and Bi2O2CO3 bulk counterpart, BiVO4/Bi2O2CO3 nanocomposites show enhanced photocatalytic degradation activity of RhB. The mechanisms for the formation of BiVO4/Bi2O2CO3 nanocomposites and enhanced photoreactivity are discussed.
396 citations
TL;DR: In this article, plate-shaped zinc oxide nanoparticles (ZnO-NPs) were successfully synthesized by a modified sol-gel combustion method, where zinc acetate, pure water and isopropanol were used as the starting materials.
390 citations
TL;DR: In this article, the authors synthesize high stable dispersions of nanosized copper particles with an average particle size less than 2 nm using a straightforward, cost-effective, and green method.
381 citations
TL;DR: In this paper, the oxidation properties of manganese oxides with adsorption features of multiwall carbon nanotubes (MWCNTs) have been combined in a composite of MWCNT/MnO2.
Abstract: It is well known that arsenite [As(III)] is less effectively removed than arsenate [As(V)] by most treatment technologies Thus, pre-oxidation of As(III) to As(V) is required prior to adsorption Here, the oxidation properties of manganese oxides with adsorption features of multiwall carbon nanotubes (MWCNTs) have been combined in a composite of MWCNT/MnO2 The composite was characterized by Fourier transform infrared absorption spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX) and X-ray diffraction (XRD) In batch culture experiments, MWCNTs and the MWCNT/MnO2 composite were examined for As(III) and As(V) The results reveal that MnO2 in the composite plays a key role in enhancing As(III) removal and As(III) removal is not as effective as As(V) removal for MWCNTs The retention of arsenite and arsenate is slightly pH dependent The reported composite can be regenerated as it was confirmed by SEM and EDX analysis The study could be considered as a model of preparation and investigation of a multifunctional material that can be used in wastewater treatment for removal of arsenic
339 citations
TL;DR: In this paper, a modified Hummers−Offeman method was used as an adsorbent for the removal of dyes in aqueous solution, and the amount of the dyes, methylene blue and malachite green, adsorbed on the GO was much higher than that on graphite.
Abstract: Graphite oxide (GO) was prepared by a modified Hummers−Offeman method and was tested as an adsorbent for the removal of dyes in aqueous solution. The structure of GO was characterized by N2 adsorption, X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. It is found that GO does not show a significant change in surface area, but the layered graphene structure was expanded, and several surface oxygen functional groups were formed, which play a significant role in adsorption. The amount of the dyes, methylene blue and malachite green, adsorbed on the GO was much higher than that on graphite, and the adsorption capacity based on the Langmuir isotherm is (351 and 248) mg·g−1, respectively, much higher than activated carbon. The adsorption mechanism was proposed as electrostatic attraction.
305 citations
TL;DR: Infrared (IR) spectroscopic studies of mineral and synthetic phosphates have been presented and the influence of non-tetrahedral cations on the shape of the spectra and the positions of bands has been analysed and the crystalline field splitting effect has been discussed.
TL;DR: This is the first report on using this type of ionic liquids based on the bis imide anion and different cations of 1-alkyl-3-methyl-imidazolium in ceria nanoparticle synthesis.
TL;DR: In this paper, a combination of state-of-the-art computational modeling and Fourier transform infrared (FTIR) spectroscopy study of the surface species formed during interaction of CO2 or CO with activated (stoichiometric), reduced, and hydroxylated ceria, CeO2, assigned various experimentally observed vibrational modes to individual types of surface species.
Abstract: Using a combination of state-of-the-art computational modeling and Fourier transform infrared (FTIR) spectroscopy study of the surface species formed during interaction of CO2 or CO with activated (stoichiometric), reduced, and hydroxylated ceria, CeO2, we assigned various experimentally observed vibrational modes to individual types of surface species. We considered carbonates CO32–, formates HCO2–, and hydrogen carbonates CO2(OH)− bound in various ways to the surface of a ceria nanoparticle. Since the structure of the surface carbonate species is particularly versatile, we introduced a notation of different types of such species and computationally determined the regions where the characteristic vibrational frequencies of each type of species can be found. The complementary FTIR measurements of the surface species produced under different conditions revealed the actual experimental vibrational peaks and allowed estimation of the accuracy of the computational method to reproduce the frequencies of differ...
TL;DR: The use of mid-infrared spectroscopy to predict the total antioxidant capacity of vegetables provides a rapid and precise alternative to traditional wet chemistry analysis.
TL;DR: In this paper, a vanadium redox flow battery with GONP-50 and 120 degrees C (GNOP-120) treated at different temperatures was investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopic analysis.
TL;DR: CeO₂ nanoparticles were synthesized hydrothermally and utilized as redox mediator for the fabrication of efficient ethanol chemi-sensor and performed well as a photo-catalyst by degrading amido black and acridine orange.
TL;DR: The ease of synthesis of the nanomaterial by wet chemistry, capability to load on suitable substrates to create stable materials and affordable cost will make it possible to use this approach in field applications, especially for the treatment of Hg(2+) contaminated waters.
TL;DR: In this article, the size of the NiO nanoparticles was estimated by X-ray powder diffraction (XRD) pattern, which was in good agreement with the particle size calculated by transmission electron microscopy (TEM).
TL;DR: The relationships between gas composition/char properties and pyrolysis temperature under high heating rate conditions were revealed and carbon skeleton shrinkage increased by more than 23% when the temperature increased from 600 to 1000°C.
TL;DR: In this article, a nonstoichiometric TiO2-graphene nanocomposite was prepared by thermal hydrolysis of suspension with graphene nanosheets and titania-peroxo complex.
Abstract: Nonstoichiometric TiO2–graphene nanocomposite was prepared by thermal hydrolysis of suspension with graphene nanosheets and titania–peroxo complex. The characterization of graphene nanosheets was provided by using an atomic force microscope (AFM). The prepared samples were characterized by Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy (RS), and transmission electron microscopy (TEM). UV/vis diffuse reflectance spectroscopy was employed to estimate band gap energies. From the titania/graphene samples, a 300 μm thin layer on a piece of glass 10 × 15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. With regard to the degree of mineralization of butane, the sample labeled TiPC0100 and containing 0.1 g of graphene nanosheets then can be considered as the most active sample.
TL;DR: In this paper, a simple approach to reduce graphene oxide (GO) solution by pulsed laser irradiation was reported, which was rapidly carried out at room temperature in only 5min.
TL;DR: Vibrational spectroscopy, unlike other techniques used in microbiology, is a relatively simple method for studying structural changes occurring within a microbial cell following environmental stress and applications of food processing treatments.
Abstract: Infrared spectroscopy and Raman spectroscopy provide complementary technologies for rapid and precise detection of microorganisms and are emerging methods in food analysis. It is possible to use either of these techniques to differentiate and quantify microorganisms in relatively simple matrices such as liquid media and simple solutions with determinations taking less than an hour. Vibrational spectroscopy, unlike other techniques used in microbiology, is a relatively simple method for studying structural changes occurring within a microbial cell following environmental stress and applications of food processing treatments. Vibrational spectroscopy provides a wide range of biochemical properties about bacteria in a single spectrum, most importantly characteristics of the cell membrane. These techniques are especially useful for studying properties of bacterial biofilms on contact surfaces, the presence and viability of bacterial vegetative cells and spores, the type and degree of bacterial injury, and assessment of antibiotic susceptibility. Future trends in food analysis will involve combining vibrational spectroscopy with microscopy, mass spectroscopy, or DNA-based methods to comprehensively study bacterial stress. Further advances in selectivity, sensitivity, and improved chemometric methods, along with reduction in the cost of instrumentation, may lead to the development of field-ready and real-time analytical systems.
TL;DR: In this paper, a simple deposition-precipitation method was used for the gas-phase degradation of volatile organic pollutants of aromatic benzene and non-aromatic acetone that are notorious volatile organic compounds (VOCs) present in indoor and outdoor air.
Abstract: The nanocomposites of Ag–AgBr–TiO 2 photocatalyst have been prepared by a simple deposition–precipitation method, which is used for the gas-phase degradation of volatile organic pollutants of aromatic benzene and non-aromatic acetone that are notorious volatile organic compounds (VOCs) present in indoor and outdoor air. A collection of joint techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet/visible diffuse reflectance spectra (UV/vis DRS) have been employed to determine the structure, morphology and optical properties of the as-prepared Ag–AgBr–TiO 2 nanocomposite. The presence of surface Ag species existed as Ag (0) and Ag (I) in Ag–AgBr–TiO 2 is confirmed by the analysis of X-ray photoelectron spectroscopy (XPS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O–Ti and O–Ti–O after the deposition of AgBr and Ag species onto the surface of TiO 2 . It is found that the Ag–AgBr–TiO 2 nanocomposite exhibits much higher photocatalytic activity and stability under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the gas-phase degradation of both aromatic benzene and non-aromatic acetone. The active radical species involved for degradation reactions over the Ag–AgBr–TiO 2 photocatalyst have been investigated by the spin-trapping electron paramagnetic resonance (EPR) spectra and the OH-trapping photoluminescence (PL) spectra. Synergetic effects between Ag–AgBr and TiO 2 have been observed and discussed for the gas-phase degradation of volatile organic compounds on the basis of joint results of characterization and photocatalytic activity.
TL;DR: In this paper, the thermal degradation pathway of poly(N-vinyl pyrrolidone) using Thermogravimetry coupled with Fourier Transform Infrared Spectroscopy (TG-FTIR) in addition to IR and 1H NMR spectroscopic studies of the partially degraded samples was investigated.
Abstract: The aim of this study was to gain some fundamental knowledge on the thermal degradation pathways of poly(N-vinyl pyrrolidone) using Thermogravimetry coupled with Fourier Transform Infrared Spectroscopy (TG–FTIR) in addition to IR and 1H NMR spectroscopic studies of the partially degraded samples. It was found that the vinyl pyrrolidone is the main volatile products of the thermal degradation of PVP which implies that the predominant mechanism during thermal degradation of this polymer is the depolymerization to monomer of the polymeric main chain; however, it is evident that simultaneous reactions may be involved yielding oligomers. FTIR and 1H NMR spectra of partially degraded samples of PVP exhibited very similar characteristics to that observed for undegraded samples although the 1H NMR spectra suggest the presence of simultaneous reactions as the fragmentation of polymeric main chain.
TL;DR: The decomposition of HCOOH on Pd surfaces over a potential range of practical relevance to hydrogen production and fuel cell anode operation was probed by combining high-sensitivity in situ surface-enhanced IR spectroscopy with attenuated total reflection and thin-layer flow cell configurations.
Abstract: The decomposition of HCOOH on Pd surfaces over a potential range of practical relevance to hydrogen production and fuel cell anode operation was probed by combining high-sensitivity in situ surface-enhanced IR spectroscopy with attenuated total reflection and thin-layer flow cell configurations. For the first time, concrete spectral evidence of COad formation has been obtained, and a new main pathway from HCOOH to COad involving the reduction of the dehydrogenation product of HCOOH (i.e., CO2) is proposed.
TL;DR: In this paper, the chitosan-PVA-NH 4 I electrolytes were analyzed using Fourier transform infrared (FTIR) spectroscopy in order to determine the interaction between salt and the polymer blend hosts.
Abstract: The (chitosan–PVA)–NH 4 I electrolytes have been prepared by the solution casting method. The prepared electrolytes are analyzed using Fourier transform infrared (FTIR) spectroscopy in order to determine the interaction between salt and the polymer blend hosts which can be deduced from the band shifting. From infrared spectra, shifts are observed at the amine, carboxamide, carbonyl and hydroxyl bands of chitosan and PVA. These shifts indicate that complexation has occurred. The crystallinity/amorphousness of the blended electrolytes has been examined by X-ray diffraction (XRD). XRD pattern shows that the crystallinity of chitosan–NH 4 I electrolyte increases with PVA concentration. Impedance of the electrolytes has been measured using electrochemical impedance spectroscopy (EIS) over the frequency range from 50 Hz to 1 MHz. The highest conducting sample 55 wt.% (chitosan–PVA)–45 wt.% NH 4 I has conductivity of 1.77 × 10 − 6 S cm − 1 . The chitosan:PVA ratio is 1:1. This is higher than the conductivity for the unblended electrolyte 55 wt.% chitosan–45 wt.% NH 4 I which is 3.73 × 10 − 7 S cm − 1 . From ln τ versus 10 3 / T plot, the activation energy for relaxation process is 0.87 eV. This is different from activation energy for dc conductivity which is 0.38 eV. Ion conduction is by hopping.
TL;DR: The ultimate sensitivity limits of molecular trace gas sensing are pushed down to attobar pressures using a comb-assisted absorption spectroscopy setup, and this result represents the lowest pressure ever detected for a gas of simple molecules.
Abstract: Radiocarbon ($^{14}\mathrm{C}$) concentrations at a 43 parts-per-quadrillion level are measured by using saturated-absorption cavity ringdown spectroscopy by exciting radiocarbon-dioxide ($^{14}\mathrm{C}^{16}\mathrm{O}_{2}$) molecules at the $4.5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ wavelength. The ultimate sensitivity limits of molecular trace gas sensing are pushed down to attobar pressures using a comb-assisted absorption spectroscopy setup. Such a result represents the lowest pressure ever detected for a gas of simple molecules. The unique sensitivity, the wide dynamic range, the compactness, and the relatively low cost of this table-top setup open new perspectives for $^{14}\mathrm{C}$-tracing applications, such as radiocarbon dating, biomedicine, or environmental and earth sciences. The detection of other very rare molecules can be pursued as well thanks to the wide and continuous mid-IR spectral coverage of the described setup.
TL;DR: In this article, the formation of single phase structure of all samples was further supported by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-Ray analysis (EDAX), UV-Visible absorption spectroscopy and Fourier transform infrared spectroscope (FTIR).
TL;DR: In this paper, a super-hydrophobic film on the surface of metallic zinc was examined by field emission scanning electron microscopy, and the results showed that the air trapped among the sheets of zinc tetradecanoate acted as a dielectric for a pure parallel plate capacitor.
TL;DR: The hydrogen storage properties of Mg(2)(dobDC) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) have been examined through low- and high-pressure adsorption experiments, infrared spectroscopy, and neutron scattering studies.