IR Absorption Research Articles

Synthesis and Characterization of Bulky Substituted Hemihexaphyrazines Bearing 2,6-Diisopropylphenoxy Groups.

New substituted [30]trithiadodecaazahexaphyrines (hemihexaphyrazines) were synthesized by a crossover condensation of 2,5-diamino-1,3,4-thiadiazole with 4-chloro-5-(2,6-diisopropylphenoxy)- or 4,5-bis-(2,6-diisopropylphenoxy)phthalonitriles. The compounds were characterized by 1H-, 13C-NMR, including COSY, HMBC, and HSQC spectroscopy, MALDI TOF spectrometry, elemental analysis, IR and UV-Vis absorbance and fluorescence techniques.

IRMPD spectroscopy and quantum-chemical simulations of the reaction products of cisplatin with the dipeptide CysGly

The inorganic antineoplastic drug cisplatin was made to react in solution with the dipeptide cysteinylglycine (CysGly), chosen as a functional model of glutathione, and the reaction products were analyzed using electrospray ionization mass spectrometry (ESI-MS). Selected complexes, i.e., the primary substitution product cis-[PtCl(NH3)2(CysGly)]+ and the chelate cis-[PtCl(NH3)(CysGly)]+, were submitted to IR multiple photon dissociation (IRMPD) spectroscopy obtaining their vibrational features. The experimental IR ion spectra were compared with the calculated IR absorptions of different plausible isomeric families, finding CysGly to bind preferentially platinum(II) via its deprotonated thiolic group in the monovalent complex, cis-[PtCl(NH3)2(CysGly)]+, and to evolve in the S,N-bound chelate structure cis-[PtCl(NH3)(CysGly)]+ through the SH and NH2 functionality of the cysteine residue. Moreover, our findings indicate that the platination reaction does not affect the CysGly peptide bond, which remains in its trans configuration.These results provide additional insights into the reactivity of Pt(II)-complexes with glutathione which is involved in cellular cisplatin resistance.

Protonation of Asp116 and distortion of the all-trans retinal chromophore in Krokinobacter eikastus rhodopsin 2 causes a redshift in absorption maximum upon dehydration.

Water is usually indispensable for protein function. For ion-pumping rhodopsins, water molecules inside the proteins play an important role in ion transportation. In addition to amino acid residues, water molecules regulate the colors of retinal proteins. It was reported that a sodium-pumping rhodopsin, Krokinobacter eikastus rhodopsin 2 (KR2), showed a color change from red to purple upon dehydration under crystalline conditions. Here, we applied comprehensive visible and IR absorption spectroscopy and resonance Raman spectroscopy to KR2 in liposomes under hydration-controlled conditions. A large increase in the hydrogen-out-of-plane (HOOP) vibration at 947 (H-C11=C12-H Au mode) and moderate increases at 893 (C7-H and C10-H) and 808 (C14-H) cm-1 were observed under dehydrated conditions, which were assigned by using systematically deuterated retinal. Moreover, the Asn variant at Asp116, which functions as a counter ion for the protonated retinal Schiff base (PRSB), caused a large redshift in the absorption maximum and constitutive increase in the HOOP modes under hydrated and dehydrated conditions. The protonation of a counter ion at Asp116 clearly causes a redshift in the absorption maximum as the all-trans retinal chromophore twists upon dehydration. Namely, the results strongly suggested that water molecules are important for maintaining the hydrogen-bonding network at the PRSB and deprotonation state of Asp116 in KR2.

In situ infrared absorption spectroscopy of cryogenic-specific reddish coloration produced by cryoplasma irradiation on an ice surface

Recently, cryoplasma has been demonstrated to form reddish coloration on methanol- and water-containing ice surfaces below 150 K. This cryogenic-temperature-only reddish coloration could provide a clue for understanding the composition of the red organic materials observed in the outer solar system. In this study, ice with reddish coloration was analyzed by IR absorption spectroscopy (2500–1700 cm−1) during cryoplasma irradiation at 85 K and subsequent increase of the temperature from 85 to 200 K without cryoplasma. The intensities of the IR peaks, differing from those of the raw materials, increased with the irradiation time during reddish coloration. When the reddish coloration disappeared at 120–150 K, the IR peak intensities at 2170 and 1790 cm−1 decreased. These peaks are thought to originate from C- and/or N-containing triple bonds or cumulative double bonds and carbonyl groups. Therefore, the reddish materials are considered to contain these functional groups.

Interfacial Inversion, Interference, and IR Absorption in Vibrational Sum Frequency Scattering Experiments.

Molecular interfacial structure greatly determines the properties of nano- and microscale systems. Vibrational sum frequency scattering (SFS) spectroscopy is a unique interface-selective tool to measure the interfacial vibrational spectrum of sub-micron to micron-scale objects dispersed in liquid and solid media. The interfacial structure is extracted from the interfacial susceptibility, a physical property derived from the intensity. Here, we describe the effect of infrared absorption that occurs in a bulk medium that is spectroscopically complex and use the results to investigate the effects of interfacial inversion, interfacial interference, and interfacial interference combined with absorption. We use the same three chemicals to do so, hexadecane oil, water, and a neutral Span80 surfactant. For all cases, the effective surface susceptibility can be retrieved from the intensity. We further find that inverting the phases results in different interfacial structures, even though they are composed of the same three chemicals, and explain this in terms of the different interactions that are necessary to stabilize the drops: steric stabilization for water drops in oil vs. charge stabilization for oil drops in water. Interfacial interference can be used to estimate the surface density of different compounds.

Bioremediation of Oil-contaminated Sand

The energy demand is set to grow very rapidly and the potential demand for oil around the world is at its highest level. Apart from indigenous oil sources, crude oil is imported by water transportation to fulfill local demand. The occurrence of oil leakage during drilling and transportation in pipelines is a major concern. As a result of this, soil is getting polluted and its geotechnical properties are altered. In this study, the effect of engine oil and diesel contamination on the geotechnical parameters of sea sand has been studied. Further, to enhance the properties of oil-contaminated sand, the bioremediation method was adopted. Sea sand from Ganagalla Peta beach, Andhra Pradesh state, India was taken up for the study. In the laboratory, 4%, 8%, 12% and 16% of engine oil and diesel were used to artificially contaminate the sea sand and geotechnical parameters; namely, compaction, shear strength and permeability, were studied for oil-contaminated sand and compared with those of virgin sea sand. In the next stage, bioremediation of engine oil-and diesel-contaminated sand was carried out to improve the geotechnical properties. It has been found that the geotechnical properties had improved after three days of bioremediation. Fourier transform infrared spectroscopy (FTIR) analysis showed that the contaminated sand is of a lipopeptide nature and showed the presence of carboxyl groups, whereas the IR absorption pattern of the treated sand matches with N-Methyl-N-Vinyl Acetamide. KEYWORDS: Engine-oil contamination, Diesel contamination, Bioremediation, Bacillus subtilis, Geotechnical properties, Compaction characteristics, Shear-strength characteristics, Permeability, FTIR analysis.

Productivity of Concentration-Dependent Conversion of Substitutional Nitrogen Atoms into Nitrogen-Vacancy Quantum Emitters in Synthetic-Diamond by Ultrashort Laser Pulses.

Tightly focused 515-nm, 0.3-ps laser pulses modify in a laser filamentation regime the crystalline structure of an Ib-type high-pressure, high-temperature (HPHT) synthesized diamond in a thin-plate form. The modified microregions (micromarks) in the yellow and colorless crystal zones, possessing different concentrations of elementary substitutional nitrogen (N) impurity atoms (C-centers), exhibit their strongly diminished local IR absorption (upon correction to the thickness scaling factor). Simultaneously, local visible-range (400-550 nm) absorption coefficients were increased, and photoluminescence (PL) yield was strongly enhanced in the broad range of 450-800 nm. The strong yellow-red PL enhancement saturates with laser exposure, implying the complete conversion of C-centers into nitrogen-vacancy (NV0,-) ones due to the laser-induced generation of Frenkel "interstitial-vacancy" I-V carbon pairs. The other emerging blue-green (>470 nm) and green-yellow (>500 nm) PL bands were also simultaneously saturated versus the laser exposure. The observed IR/optical absorption and PL spectral changes enlighten the ultrashort pulse laser inscription of NV0--based quantum-emitter centers in synthetic diamonds and enable the evaluation of the productivity of their inscription along with the corresponding I-V generation rates.

The Surface acidity of freshly synthesized microplastics particles in simple electrolyte

The surface chemistry of sub-micron microplastics (MP) particles, specifically, the pH-dependent surface charge (or surface acidity), plays a role on the transport, transformation, and effect of contaminants in the aquatic environment. Little is known on the origin of surface charge and the quantification of surface acidity of MP. In this study, the surface charge of submicron particles of six major polymers, including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET), was characterized in inert electrolytes, namely, NaClO4, NaCl, and NaNO3 for the elucidation of surface acidity. IR absorbance revealed that oxygen-rich functional groups were introduced during the resynthesis of MP particles, whose surface chemical structure consists of three main functional groups, i.e., carboxylic/ester, ether/alcohol, and aliphatic. Results show clearly that the zeta potential of MP particles was negatively charged in simple electrolytes at pH greater than ca. 2.0. Hydroxide ions adsorption on the non-polar aliphatic sites, and deprotonation of surface hydroxy group on the polar carboxylic/ester and ether/alcohol sites, contributed to the negative charges on MP surface. The surface acidity of selected MP particles was established in terms of acid strength (intrinsic acidity constants) and capacity (total surface site concentration) for the three distinct surface sites. Results also show the surface acid site density increases with hydration/hydrolysis time with rate constants of the polar surface sites, i.e., carboxylic/ester and ether/alcohol being 2.3 times greater than that of the non-polar aliphatic group.

Detection of germanium isotopes in biosynthesized Ge nanocrystals through different optical spectroscopy techniques

The current work aims to investigate the isotopic effect in biosynthesized Germanium nanocrystals (Ge NCs) through Raman and IR absorption spectra. By treating bulk germanium crystal with microorganisms in a weak magnetic field, Ge NCs with great chemical and isotopic purity are produced on its surface. Using various techniques, including X-ray diffraction, photoluminescence spectroscopy, micro-Raman spectroscopy, and FTIR spectroscopy, the structural and optical characteristics of the synthesized Ge NCs are studied. The PL, Raman, and IR peaks of synthesized material, which are recorded at various time intervals, are seen to have shifted. The PL peak shift of fabricated material is seen as a result of the quantum confinement effect. Raman and IR absorption spectra analysis, which are conducted at room temperature reveals the possible presence of germanium isotopes. It is observed that the phonon absorption peaks of synthesized germanium NC material shift to longer wavelengths with increasing average atomic mass of germanium. The observed optical properties of the synthesized Ge NCs have provided great help to study the change in structural and optical properties of the synthesized Ge crystal.

Natural iron-aluminosilicate as potential solid precursor for supplementary cementitious materials: A comparative study with other aluminosilicates

The objective of this study was to investigate the impact of the geographic and climatic conditions on laterites properties and on geopolymerization based-laterite. Four different laterite deposits in the four geographical zones of Cameroon were studied. This included the center, north, south and west corners of Cameroon, having chemical composition of SiO2 + Al2O3 + Fe2O3 = 88.94, 87.6, 89.13 and 78.97%, respectively. The center and south laterites from the black forest, with high pluviometry and relative humidity, show significant amounts of Fe2O3. While the west laterite from grass field - mountainous areas and the north-laterite from plain arid and semi-arid climate still show lower iron concentrations. The IR absorption bands of the different laterites appear between 1007 and 1047 cm−1; characteristic bands of aluminosilicate. The BET (Brunauer-Emmett-Teller) Specific surface area values are comprised in the range of [21.9, 24.1 m2/g] for non-calcined laterite and between [45.6 and 123.5 m2/g] for laterites calcined at 550 °C and 575 °C. The main particle size values are 5.71, 6.37, 7.43 and 8.45 μm for center-laterite, west-laterite, north laterite and south-laterite, respectively. Although, they differ in the degree of laterization, all the laterites present almost total conversion to geopolymers, due to the presence of amorphous kaolinite and reactive goethite. However, the iron content has significant impact on the globular microstructure. The particle size of laterites, their high values of BET surface area and their significant reactivity make them promising substitutes to metakaolin and other supplementary cementitious materials.

Quantitative evaluation of low-concentration OH impurities in quartz glass by infrared photothermal deflection spectroscopy

.Impurity control in materials is of great importance to achieve excellent performance, yet the quantitative determination of trace impurities, especially OH, is extremely difficult using today’s characterization techniques. Here we report the determination of trace amounts of OH in quartz glass plates by photothermal deflection spectroscopy (PDS) extended to the IR region. PDS detects trace OH based on the amount of heat generated during non-radiative processes during light irradiation. IR absorption spectra of quartz glasses with five different OH concentrations were investigated. In addition to the standard OH band around 3640 cm−1, we find that there are combination modes, overtones, and water-induced IR features. The presence and OH concentration dependence of these species reveal the role of impurities in quartz glass. The PDS is effective in quantifying OH concentrations below 1 ppmw (parts per million weight) in quartz glass plates.

Methods to characterize the crystal polymorphs of polyvinylidene fluoride using Fourier transform infrared spectroscopy

AbstractPolyvinylidene fluoride (PVDF), a polymer with three common crystal polymorphs (α, β, γ), has several practically useful properties, including piezoelectric properties. Accurate measurement of its crystalline polymorphs is important since only the β phase has the desired piezo properties. PVDF was processed into isotropic samples having predominantly α, β, and γ crystalline phases. These samples were analyzed with Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and differential scanning calorimetry (DSC). FTIR spectra were fitted with the Gaussian peaks for quantitative analysis of the phases. Peaks exclusive to the amorphous phase were identified and used for the amorphous phase quantification, leading to the accurate determination of the crystalline fraction. IR absorption coefficients for their respective peaks were calculated to quantify individual crystalline polymorphs in the sample. Pure phase spectra were extracted, and a linear combination of the pure phase spectra was fitted to the spectrum of a sample with different phases to accurately obtain the values of the phase fraction and the thickness of the sample.

Synthesis, physicochemical properties, and antitumor cytotoxic activity of the Mg(II) coordination complex containing 1,10-phenanthroline and sulfate ligands

The complex mer-triaqua-(1,10-phenanthroline)-(sulfate-O)-magnesium(II) was synthesized by the solvent slow evaporation method from the crystallization of an equimolar saturated solution of 1,10-phenanthroline and magnesium sulfate heptahydrate in a mixed solution of deionized water and DMF. The structural, vibrational, and thermal properties were studied by X-ray powder diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FT-IR), and thermoanalytical analyses. Calculations based on density functional theory (DFT) were also applied to the system for an accurate analysis of vibrational modes and to obtain theoretical data on the nature of bonds, chemical reactivity descriptors, electrostatic potential map, and electronic properties. XRPD results showed that the coordination compound in the study has monoclinic symmetry (space group P21/c) and contains four molecules per unit cell (Z = 4). The thermal measurements revealed that the material presents a thermodynamically irreversible process around 303 K, arising from the evaporation of three coordination water molecules. In addition, all IR absorption bands were assigned, with contributions from the DFT calculations. Finally, cell viability assays were conducted, confirming the antitumor activity of the complex in MCF-7 (breast) and SiHa (cervical) cancer cells, exhibiting a considerable selective cytotoxic effect.

Judd–Ofelt and photoluminescence analysis of Nd2O3-doped within host fluoroborate glass from the system B2O3–NaF–La2O3

Undoped glass of chemical composition 70B2O3–25NaF–5La2O3 together with Nd2O3-doped samples were prepared via conventional melt and annealing procedure. The prepared glasses were investigated through photoluminescence measurements to find out their extent for the lasing application. The undoped sample reveals two UV absorption peaks while Nd2O3-doped samples show 10 well-characterized peaks in the UV–Visible range that are correlated to different transition states of Nd3+ ions. Three different bands are detected in the emission spectra at 875 nm (4F3/2 → 4I9/2), 1056 nm (4F3/2 → 4I11/2), and 1326 nm (4F3/2 → 4I13/2). The Judd–Ofelt parameters (Ω2, Ω4, Ω6) and radiative properties were estimated using the Judd–Ofelt theory. The represented data indicated that the transition line 4F3/2 → 4I11/2 is the sharpest and lowest bandwidth value than other detected transitions. The structural analysis by FTIR vibrational modes suggested that the IR absorption bands within the range 800–1200 cm−1 originate from both combined vibrations of tetrahedral (BO4) and (BO3F) groups together with (NaF4) groups beside triangular BO3 groups which are vibrating within the range 1200–1600 cm−1. The addition of Nd2O3 is assumed to cause the possible transformation of some structural B–O bonds within the range of triangular borate units referring to the possible formation of pyroborate units or similar structural groups.

Quantitative analysis of polar crystalline fractions in poly(vinylidene fluoride) electrospun fibers and electrosprayed films

We have used a novel technique, Fourier self-deconvolution (FSD) of the infrared spectrum, to quantify the relative fractions of the electro-active (EA) crystal phases in poly(vinylidene fluoride), PVDF. Electrospinning and electrospraying are effective methods to obtain the EA phases which include the polar β (chain conformation, TTTT) and γ (TTTGTTTG’) crystallographic phases. In this work we studied electrospun fiber mats and electrosprayed non-fibrous mats of PVDF obtained from solutions of N,N-dimethylacetamide and acetone. Wide-angle X-ray scattering (WAXS) and Fourier-transform infrared (FTIR) spectra show that samples prepared by electrospinning/electrospraying contained only polar crystal phases, and no non-polar alpha phase crystals were present. Fourier Self Deconvolution is a method used to synthetically narrow broad and complex infrared absorbance spectra. Here we demonstrate this technique to determine the relative fractions of β- and γ-phase crystals by resolving the peak at 840 cm−1 in the IR absorbance spectra. When the overall level of crystallinity is known, as it is here from X-ray analysis, then FSD allows determination of the absolute content of the polar β and γ phases. Comparing results from wide-angle X-ray scattering and FTIR/FSD, we show that γ-phase dominates over β-phase in both electrospun and electrosprayed materials, with relative γ to β ratios of 55/45 and 81/19, respectively.

Pseudoheterodyne interferometry for multicolor near-field imaging.

We report the development and characterization of a detection technique for scattering-type scanning near-field optical microscopy (s-SNOM) that enables near-field amplitude and phase imaging at two or more wavelengths simultaneously. To this end, we introduce multispectral pseudoheterodyne (PSH) interferometry, where infrared lasers are combined to form a beam with a discrete spectrum of laser lines and a time-multiplexing scheme is employed to allow for the use of a single infrared detector. We first describe and validate the implementation of multispectral PSH into a commercial s-SNOM instrument. We then demonstrate its application for the real-time correction of the negative phase contrast (NPC), which provides reliable imaging of weak IR absorption at the nanoscale. We anticipate that multispectral PSH could improve data throughput, reduce effects of sample and interferometer drift, and help to establish multicolor s-SNOM imaging as a regular imaging modality, which could be particularly interesting as new infrared light sources become available.

IR Spectroscopy of Vacancy Clusters (Amber Centers) in CVD Diamonds Nanostructured by Fast Neutron Irradiation

We investigated the IR absorption spectra of CVD diamond damaged by fast neutrons (>0.1 MeV) with high fluences ranging from 1 × 1018 to 2 × 1019 cm−2 and annealed at temperatures of 200 °C to 1680 °C. After annealing above 1000 °C, the formation of “amber-centers” (ACs), associated with multivacancy clusters, is detected as deduced from the appearance of a strong absorption line at 4100 cm−1. Moreover, the concentration of the ACs in the irradiated diamond can be an order of magnitude higher than that observed previously in the darkest brown natural diamonds. A number of other absorption lines, including the H1b center at 4936 cm−1 (0.612 eV) and new lines at ~5700 cm−1 (0.706 eV) and 9320 cm−1 (1.155 eV) not reported before in the literature, are observed, and their intensity evolutions at annealing temperatures are documented. At the highest fluences, all the lines show reduced intensities and broadening and spectral shifts due to a very high defect concentration and partial amorphization. The obtained experimental data can be used for the analysis of defect generation, transformations and healing in irradiated synthetic and natural diamonds.

Tuning electronic structure and chemical reactivity via oxidation state in molybdenum oxide

Molybdenum oxide has a broad range of applications in areas such as catalysis, antimicrobial coatings, medicine, and sensors. In this study, we have investigated the geometric and electronic structure, thermal stability, and chemical reactivity of molybdenum oxide at different oxidation and electronic charge states using cluster models of Mo7On with density functional theory calculations. A decrease in the energy of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) has been identified as n increases from 0 to 21. Ionization potential and electron affinity of Mo7On correlate strongly with the energies of HOMO and LUMO, and both increase with increasing n. We have identified the most stable CO binding sites on Mo7On, calculated CO binding energy and simulated IR absorption spectrum of COMo7On. An n-dependent increase in CO stretching frequencies and decrease in CO binding energies indicate that electron backdonation from Mo7On to CO governs the changes in CO binding energy as a function of oxide composition. CO stretching frequency in COMo7O21 is 2197 cm−1, which is 55 cm−1 higher than in the gas phase CO molecule, indicating that CO is an electron density donor and the oxide acts as an electron acceptor at this stoichiometric composition. Comparing CO binding energies in neutral and ionic (q=+/-1) COMo7On, there is, in average, a stabilizing effect of excess (missing) charge on CO binding energy at low (high) n.

Alternative raw material research for decarbonization of UK glass manufacture

AbstractBased on the current UK decarbonization policy, a general outlook on potential routes for the glass industry to achieve net‐zero is discussed and the differentiation during decarbonization is specified. Biomass ash is considered a potential alternative raw material for low‐carbon glass manufacture as it is rich in certain advantageous components, chiefly network modifiers. Simple sieving processes were shown to effectively separate impurities such as S, Cl, and C from some biomass ashes according to particle size distribution. The concentration of undesirable impurities decreased with increasing particle size. Morphologies and X‐ray diffraction patterns of larger washed biomass ash particles indicated liquid/amorphous phase formation during biomass combustion. The washing of ashes was also shown to be a potential route to purification. A washed bracken ash relevant to both modern and ancient glass production was characterized for comparison. Ultraviolet‐visible near‐infrared (UV‐Vis‐near IR) absorption spectra of representative green container glasses produced using biomass ash confirmed that ∼5 wt.% ash in representative glass batches has little impact on the color and redox state of glasses; the redox status of glass produced using >2 mm biomass ash after washing was less reduced than that of glass produced using high levels (>∼9 wt.%) of >2 mm biomass ash after sieving alone, observed via the redox couple Cr3+/Cr6+ by UV‐Vis‐near IR absorption spectroscopy.

A disparity in solvatochromism of C[dbnd]O and S[dbnd]O vibrational probe: A study of structurally similar acetone and dimethyl sulfoxide

Solvatochromic studies of small IR probes are beneficialto study the structural dynamics of biomolecules as well as measuring the strength of surrounding electric fields in condensed phases.Herein, we have investigated the CO and SO vibrational probes of structurally similar acetone and dimethyl sulfoxide respectively to compare the solvatochromism. Interestingly in water CO formed both one hydrogen bond and two hydrogen bond complexes wherein SO formed only two hydrogen bond complexes.Not only this, but we have also investigated how different solvents alter the IR spectra of the CO and SO vibrating modes during the interaction with α CH of acetone and DMSO respectively.The IR absorption spectra of CO of acetone altered after αdeuteration(acetoned6) in aprotic organic solvents as well as aqueous solvents. But, surprisingly for DMSO and DMSOd6, the IR spectra of SO mode remain intact during α isotopic exchange (CH3to CD3) in organic aprotic solvents but in strong coordinating polar protic solvents (D2O) it is altered remarkably. The equivalent frequency gap of CO of acetone and acetoned6 in organic solvents and water represent the no interaction of α CH/D with solvent molecules. Parallelly unaltered IR spectral signature of SO of both DMSO and DMSOd6 in aprotic organic solvent represents the stationary state of the ‘S’ atom and altered SO IR absorption in water signifies the different α CH and α C-D interaction with the surrounding water molecules. These results are the cautionary of perturbation on IR probe during α CH interaction with solvents as well as guest molecules.