Active Vibrational Bands Research Articles

Enhancing metronidazole photodegradation through the application of dysprosium vanadate/oxidized carbon nanofiber composite

The widespread usage of nitroimidazole antibiotics, including metronidazole (MD), and the improper disposal of pharmaceutical residues in groundwater samples pose a significant health risk due to the potential carcinogenic and mutagenic toxicity. Our research engineered a nanocomposite by combining dysprosium vanadate with oxidized carbon nanofibers (DyVO4/O-CNF) through coprecipitation, acid treatment, and ultrasonication methods. We meticulously examined these prepared nanocomposites using various spectroscopic and microscopic techniques, revealing enhanced characteristics in crystallinity, active vibrational bands, valence states, band gap, and structural morphology. To assess the photocatalytic efficacy of DyVO4/O-CNF nanocomposite for degrading MD, we performed a series of photocatalytic experiments. These included optimizing the dosage, analyzing MD concentration, studying the influence of radical scavengers, and examining the mineralization process along with the potential photodegradation mechanism. Our findings demonstrated that the DyVO4/O-CNF nanocomposite (98.7 % within 40 min) surpassed other catalysts such as TiO2 (26.1 %), pristine CNF (40.3 %), and DyVO4 (59.6 %). Furthermore, we evaluated the nanocomposite's stability and reusability, revealing a consistent photodegradation efficiency of 94.7 % even after five consecutive cycles. These findings highlight the efficacy of the DyVO4/O-CNF nanocomposite as a highly effective catalyst for the photodegradation of MD.

Structural, magnetic and optical properties of diluted magnetic semiconductor (DMS) phase of Ni modified CuO nanoparticles

Control on the size of copper oxide (CuO) in the nano range is a highly motivating approach to study its multifunctional nature. The present investigation reports a sol-gel derived Ni doped CuO nanoparticles (Cu1-xNixO). Rietveld refinement of the XRD spectra confirms the formation of single monoclinic phase of Cu1-xNixO nanoparticles having crystallite size within the range of 19–21 nm. Raman spectra show the presence of characteristics Raman active modes and vibrational bands in the Cu1-xNixO samples that corroborate the monoclinic phase of the samples as revealed by refinement of XRD data. The estimated band gap of pure CuO is found to be ∼1.43 eV, which decreases with the increase of dopant concentration into CuO matrix. This result is in line with estimated crystallite size. Magnetization curves confirm the weak ferromagnetic nature of Cu1-xNixO nanoparticles which reveal the DMS phase. This weak magnetic nature may be induced in the samples due to the exchange interaction between the localized magnetic d-spins of Ni ions and carriers (holes or electrons) from the valence band of pristine CuO lattice. Replacement of Cu+2 by Ni+2 ions into the host CuO lattice induces the magnetization. The quantified value of squareness ratio (S < 0.5) confirms the inter-grain magnetic interactions in the Cu1-xNixO nanoparticles which is also the reason of weak induced magnetization.

Symmetry in magnetic and vibrational spectra of multi-element spinel ferrite

We fabricated by solid-state ceramic technique single-phase mixed spinel ZnxMg0.3−xCu0.7Al0.3Fe1.7O4 with x index from 0.05 to 0.25, step 0.05 for the first time. The goal was to study the effect of cation doping on internal structure and magnetic properties of the material. The ferrites werefirst characterized by X-ray diffraction to confirm their purity. Magnesium and Zinc cations showed tetrahedral site preference, while Aluminum cations preferred the octahedral site. The effective magnetic moment and exchange interaction increased with the Zinc content. The pure single phase structures allowed us to investigate the vibrational spectra based on the symmetry conditions. We found only two infrared bands, while based on symmetry calculation of the factor group, four bands are predicted. The number of atoms and their relative arrangement in the crystal are the main criteria to define the active vibrational bands as predicted by factor group theory and the magnetic response of the material.

C70 Fullerene Cage as a Novel Catalyst for Efficient Proton Transfer Reactions between Small Molecules: A Theoretical study

When acids are supplied with an excess electron (or placed in an Ar or the more polarizable N2 matrix) in the presence of species such as NH3, the formation of ion-pairs is a likely outcome. Using density functional theory and first-principles calculations, however, we show that, without supplying an external electron or an electric field, or introducing photo-excitation and -ionization, a single molecule of HCl or HBr in the presence of a single molecule of water inside a C70 fullerene cage is susceptible to cleavage of the σ-bond of the Brønsted-Lowry acid into X− and H+ ions, with concomitant transfer of the proton along the reaction coordinate. This leads to the formation of an X−···+HOH2 (X = Cl, Br) conjugate acid-base ion-pair, similar to the structure in water of a Zundel ion. This process is unlikely to occur in other fullerene derivatives in the presence of H2O without significantly affecting the geometry of the carbon cage, suggesting that the interior of C70 is an ideal catalytic platform for proton transfer reactions and the design of related novel materials. By contrast, when a single molecule of HF is reacted with a single molecule of H2O inside the C70 cage, partial proton transfers from HF to H2O is an immediate consequence, as recently observed experimentally. The geometrical, energetic, electron density, orbital, optoelectronic and vibrational characteristics supporting these observations are presented. In contrast with the views that have been advanced in several recent studies, we show that the encaged species experiences significant non-covalent interaction with the interior of the cage. We also show that the inability of current experiments to detect many infrared active vibrational bands of the endo species in these systems is likely to be a consequence of the substantial electrostatic screening effect of the cage.

3D Raman Spectroscopy of Large Zeolite ZSM-5 Crystals.

Hydrothermal treatment is a common method used to modify the physicochemical properties of zeolite‐based catalyst materials. It alters the number and type of acid sites through dealumination and increases molecular diffusion by mesopore formation. Steaming also reduces the structural integrity of zeolite frameworks. In this study, Raman microscopy has been used to map large zeolite ZSM‐5 crystals before and after steaming. 3D elemental maps of T−O (T: Al or Si) sites of the zeolite were obtained. The Raman active vibrational bands were determined, which are indicative of (non‐) framework Al, as well as of structural integrity. Zeolite steaming caused the introduction of additional heterogeneities within the zeolite framework. Al migration and the formation of extra‐framework Al species were observed. The described experiments demonstrate the capability of 3D Raman spectroscopy as a valuable tool to obtain information on the spatial distributions of framework elements as well as defects within a zeolite‐based material.

Analysis of Zn substitution on structure, optical absorption, magnetization, and high temperature specific heat anomaly of the nano-crystalline LaFeO3

Nano-crystalline LaFe1−xZnxO3 (0 ≤ x ≤ 0.3) samples synthesized through the sol-gel auto-combustion technique have been studied. X-ray diffraction patterns reveal that all the samples have an orthorhombic crystal structure and exist in a single phase. Bond lengths and bond angles determined using Rietveld refinement change with the concentration, leading to the modification of the parent structure. The change in the structure is reflected in the thermal measurements too. The morphological studies reveal a wide-range of particle size distribution, consisting of nanometer-sized particles to macro-agglomerations. FTIR spectra show two strong active vibrational bands present at 564 cm−1 and 410 cm−1, which are related to the functional groups present in the material. The optical bandgap has been determined and is found to decrease with the increase in the concentration of Zn. Raman spectroscopy rules out the symmetry breaking or any other structural phase transition in the system. The Raman spectra reveal the strain present in the samples on increasing the concentration of Zn doping. The doping of Zn in place of Fe produces distortion mainly in the oxygen bending and stretching vibrations. Specific heat as a function of temperature has been studied and found to be sensitive to magnetic ordering. The Neel temperature decreases from 411 °C to 377 °C with the increase in the Zn concentration, which is concomitant with the Rietveld analysis. The density of our system decreases with Zn doping and leads to the increased value of specific heat. Hysteresis loops indicate that Zn doping increases the magnetic moment and decreases the coercivity.

Characterisation of the Chemical Composition and Structural Features of Novel Antimicrobial Nanoparticles.

Three antimicrobial nanoparticle types (AMNP0, AMNP1, and AMNP2) produced using the TesimaTM thermal plasma technology were investigated and their compositions were determined using a combination of analytical methods. Scanning electron micrographs provided the morphology of these particles with observed sizes ranging from 10 to 50 nm, whilst FTIR spectra confirmed the absence of polar bonds and organic impurities, and strong Raman active vibrational bands at ca. 1604 and 1311 cm−1 ascribed to C–C vibrational motions were observed. Carbon signals that resonated at δC 126 ppm in the solid state NMR spectra confirmed that sp2 hybridised carbons were present in high concentration in two of the nanoparticle types (AMNP1 and AMNP2). X-ray powder diffraction suggested that AMNP0 contains single phase Tungsten carbide (WC) in a high state of purity and multiple phases of WC/WC1-x were identified in both AMNP1 and AMNP2. Finally, X-ray photoelectron spectral (XPS) analyses revealed and quantified the elemental ratios in these composite formulations.

Infrared spectroscopy of secondary organic aerosol precursors and investigation of the hygroscopicity of SOA formed from the OH reaction with guaiacol and syringol.

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) synchrotron analyses supplemented by density functional theory (DFT) anharmonic calculations have been undertaken to study the fundamental vibrational signatures of guaiacol and syringol, two methoxyphenol compounds found at the highest concentrations in fresh wood smoke and precursors of secondary organic aerosols (SOA) affecting the radiative balance and chemistry of the atmosphere. Nitroderivatives of these two compounds have also been studied experimentally for nitroguaiacol and theoretically for nitrosyringol. All the active fundamental vibrational bands have been assigned and compared to available gas phase measurements, providing a vibrational database of the main precursors for the analysis of SOA produced by atmospheric oxidation of methoxyphenols. In addition, the SOA formed in an atmospheric simulation chamber from the OH reaction with guaiacol and syringol were analyzed using the ATR-FTIR synchrotron spectroscopy and their hygroscopic properties were also investigated. The vibrational study confirms that nitroguaiacol and nitrosyringol are the main oxidation products of methoxyphenols by OH and are key intermediates in SOA production. The hydration experiments highlight the hydrophilic and hydrophobic characters of nitrosyringol and nitroguaiacol, respectively.

Cryo Kinetics and Spectroscopy of Cationic Nickel Clusters: Rough and Smooth Surfaces

The stepwise N2 adsorption on size selected Ni9+ and Ni13+ clusters at 26 K is studied in a hybrid tandem ion trap instrument. Adsorption kinetics of these clusters in conjunction with infrared photon dissociation (IR-PD) spectroscopy of their cluster adsorbate complexes allows for the elucidation of various N2 coverage and cluster size dependent effects, which are related to the rough Ni9+ and smooth Ni13+ cluster surface morphologies. Pseudo-first-order kinetic fits confirm consecutive adsorption steps by single exponential decays exclusively. The recorded IR-PD spectra of all observed cluster adsorbate complexes reveal IR active vibrational bands at frequencies of 2170–2260 cm–1, which coincides with the range of metal head-on coordinated N–N stretching modes. Density functional theory (DFT) calculations confirm the experiments and reinforce a possible isomerization with low N2 coverage in the case of Ni9+.

Magnetically roll-oriented LaFeO3 nanospheres prepared using oxalic acid precursor method

Roll-oriented lanthanum orthoferrite LaFeO3 powders have been successfully synthesized using oxalic acid precursor method. Well crystalline LaFeO3 phase was obtained at different annealing temperatures from 600 to 1,000 °C for 2 h. FT-IR spectrum indicated that two active vibrational bands were assigned at 555 and 400 cm−1 imputed the formation of lanthanum orthoferrite. The average particle size of LaFeO3 powders were ranged from 50 to 150 nm. The magnetic properties of LaFeO3 samples exhibited a weak ferromagnetic behavior at the room temperature. The shape and surface interface anisotropy were so far strong forming a roll-orientation of particles. The interplay between magnetic properties and annealing temperature showed that the low magnetic interactions between particles were observed as the result of large particles size produced and low surface–interface anisotropy occurred. Hence, microstructures were gradually transformed to tube- and then fibrous-like structures with increasing the annealing temperature. Results are explained in basis of spin–orbit interactions between particles. Furthermore, analysis of the AC electrical data in impedance and dielectric permittivity formalisms revealed the presence of three relaxation processes in LaFeO3, with sufficiently different relaxation times.

Metastable Monoclinic ZnMoO4: Hydrothermal Synthesis, Optical Properties and Photocatalytic Performance

Metastable monoclinic ZnMoO4 was successfully synthesized via a hydrothermal route with variation of reaction temperatures and time at pH value of 5.7. Systematic sample characterizations were carried out, including X-ray powder diffraction, scanning electron microscopy, Fourier transformed infrared spectra, UV-visible diffuse reflectance spectra, and photoluminescence spectra. The results show that all as-prepared ZnMoO4 samples were demonstrated to crystallize in a pure-phase of monoclinic wolframite structure. All samples were formed in plate-like morphology. Six IR active vibrational bands were observed in the wave number range of 400-900 cm(-1). The band gap of as-prepared ZnMoO4 was estimated to be 2.86 eV by Tauc equation. Photoluminescence measurement indicates that as-prepared ZnMoO4 exhibits a broad blue-green emission under excitation wavelength of 280 nm at room temperature. Photocatalytic activity of as-prepared ZnMoO4 was examined by monitoring the degradation of methyl orange dye in an aqueous solution under UV radiation of 365 nm. The as-prepared ZnMoO4 obtained at 180 degrees C for 40 h showed the best photocatalytic activity with completing degradation of MO in irradiation time of 120 min. Consequently, monoclinic ZnMoO4 proved to be an efficient near visible light photocatalyst.

Infrared spectroelectrochemical investigations on the doping of soluble poly(isothianaphthene methine) (PIM)

Attenuated total reflection Fourier transform infrared (ATR-FTIR) investigations on the doping processes in substituted poly(isothianaphtene methine) (PIM), a new low band-gap conjugated polymer, are reported. The doping was studied in situ during chemical p-doping (oxidation) by iodine and during electrochemical p-doping (oxidation) and n-doping (reduction). During both signs of doping, infrared active vibrational (IRAV) bands due to strong coupling of the electrons to lattice vibrations are observed. The results are compared to FT-Raman spectra. Electrochemical p-doping shows two different doping regimes depending on the electrochemical potential. The narrow linewidth and low absorption intensities of the IRAV bands indicate a strong localization of the doping induced charge carriers, which is ascribed to a tilted geometry of the conjugated backbone due to steric repulsion effects.

Spectroscopic and Electrical Conductivity Studies of SomeSemicarbazide Hydrochloride Complexes

The infrared and electronic absorption spectra of semicarbazidehydrochloride and its complexes with anthracene,tetracyanoquinodimethane TCNQ, Na-fluorescein and cupferron wererecorded in the regions 200–4000cm-1 and200–400nm. The new bands that appeared in the complex spectrawere assigned. The effect of the complex formation on the frequencyand intensity of the active vibrational bands was also studied. Theinternal energy changes of the complexes were calculated in a new lineof calculation to give a clear insight about the stability of theinvestigated complexes.The electrical conductivity of the complexes was measured in the temperature range 25–130°C. The activation energy E was calculated and discussed on the basis of the spectroscopic information.

In situ FTIR-ATR spectroscopic investigations on the redox behavior of poly(thienylpyrrole) thin film electrodes in non-aqueous solutions

Using in situ FTIR attenuated total reflection (ATR) spectroscopy, the electrochemical redox processes of poly(thienylpyrrole) (FTP) in acetonitrile (AN) solutions containing Bu 4NClO 4 or Bu 4NPF 6 were investigated. The spectra of PTP based on electrochemically induced structural changes are presented. At higher oxidation levels, a delocalization of the positive charge along the polymer chain is induced to a significant content and the intensities of IR active vibrational (IRAV) bands are dramatically increased. The relations of the intensities of IRAV bands to the oxidation potential show that at lower anodic potentials the initial charge-carrier species are polarons, while at higher potentials (>300 mV), bipolarons are also formed coexisting with the polarons. At potentials >500 mV only bipolarons exist. By comparing the intensity ratios of some characteristic bands, different conductivities of the films were observed in situ.

SPECTROSCOPIC AND ELECTRICAL CONDUCTIVITY STUDIES OF SOME SEMICARBAZIDE HYDROCHLORIDE COMPLEXES

The infrared and electronic absorption spectra of semicarbazide hydrochloride and its complexes with anthracene, tetracyanoquinodimethane TCNQ, Na fluorescein and cupferron was recorded in the regions 200-4000 cm and 200 -400 nm. The new bands that appeared in the complex spectra were assigned. The effect of the complex formation on the frequency and intensity of the active vibrational bands was also studied. The internal energy changes of the complexes were calculated in a new line of calculation spectrophotometrically to give a clear insight about the stability of the investigated complexes. The electrical conductivity of the complexes was measured in the temperature range of 25 C to 130°C. The activation energy was calculated and discussed on the basis of the spectroscopic information.

Infrared spectroscopy and Mie scattering of acetylene aerosols formed in a low temperature diffusion cell

A method is described for forming and spectroscopically characterizing cryogenic aerosols formed in a low temperature gas cell. By adjusting the cell pressure, gas composition and flow rate, the size distribution of aerosol particles can be varied over a wide range. The combination of pressure and flow rate determine the residence time of the aerosols in the cell and hence the time available for the particles to grow. FTIR spectroscopy, over the range from 600 to 6000 cm−1, is used to characterize the aerosols. The particle size distribution can be varied so that, at one extreme, the spectra show only absorption features associated with the infrared active vibrational bands and, at the other, they display both absorption and Mie scattering. In the latter case, Mie scattering theory is used to obtain semiquantitative aerosol size distributions, which can be understood in terms of the interplay between nucleation and condensation. In the case of acetylene aerosols, the infrared spectra suggest that the particles exist in the high temperature cubic phase of the solid.

Infrared spectroscopy of the electrochemical double layer via electrode emersion

AbstractInfrared reflection Spectroscopy was used via electrode emersion to study both adsorbed and non‐specifically adsorbing species within the electrochemical interphase on gold, ex situ. A cell was designed which allowed the electrode to rotate and continuously emerse from solution. The parallel‐polarized IR beam was reflected from the rotating surface above the solution at approximately 80°. FTIR spectra were taken of gold electrodes emersing from aqueous solutions of crystal violet, HCIO4, and D2SO4 at various electrode potentials, and ratioed as a function of potential. Active vibrational bands of crystal violet which strongly adsorbs to the gold, and of ClO4− and SO42− ions within the more ideally‐polarizable double layer, are easily seen. Changes in band intensities as a function of potential are, to first order, as expected.

Raman-spectrophotometric determination of the tungstate anion and its isopolyanions in aqueous systems

The tungstate and some isopolyanions were determined by Raman spectrophotometry. Using the more intensive Raman active vibrational bands of these species and the bending vibration of water at 1,650 cm−1 as an internal standard the linear ranges for the measurement of concentrations were elucidated. The detection limits for tungstate, paratungstate-A, ψ-metatungstate and metatungstate are 4×10−3 M, 9×10−3 M, 10−2 M and 10−2 M, respectively. This technique was used to examine a mixture of tungstate and paratungstate-A.

Complex refractive index in the infrared for NaCl, NaNO_3, and NaHCO_3 in water*

Relative specular reflectances of individual 0.5M aqueous solutions of NaNO3, NaHCO3, NaCl, and of 0.25M NaCl were measured in the 500–5000 cm−1(2–20 μm) region of the infrared for linearly polarized radiant flux having the electric field vector perpendicular to the plane of incidence. Distilled water was the reflectance standard. The angle of incidence was 70.03° ± 0.23°. Kramers-Kronig analysis of the relative reflectance spectra provided phase-difference spectra for the aqueous solutions and a tabulation of spectral values for the complex refractive index n + ik. The strengths of selected infrared active vibrational bands of the molecular anions NO3− and HCO3− were determined by integrating values for their molecular extinction coefficients over spectral regions of the bands.

Utilisation des isotopes D, 15N, 26Mg pour l'étude vibrationnelle de Mg(NH 3) 6Cl 2.

The following substituted magnesium chloride hexa-ammines: 24Mg( 14NH 3) 6Cl 2; 26Mg( 14NH 3) 6Cl 2; 24Mg( 15NH 3) 6Cl 2; 24Mg( 14ND 3) 6Cl 2; 24Mg( 14ND 3) 6Cl 2 have been studied by i.r. and Raman spectroscopy. The frequency shifts have been measured for all active vibrational bands predicted by group theory analysis. The results show that measurements made on isotopically substituted compounds can provide confirmation of assignments of vibrational bands previously proposed [2].