Fourier Transform Infrared Absorption Bands Research Articles

Conformation-dependent molecular association and spectral properties of 4-pentyl-4′-cyanobiphenyl liquid crystal in different phases

The 4-pentyl-4′-cyanobiphenyl (5CB) molecule conformation and structure alignment have been investigated by means of temperature variable Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy in a wide temperature range (from −90 to 50 °C) covering the 5CB glass-like, metastable and stable crystalline, nematic and isotropic phases defined by differential scanning calorimetry measurements. The corresponding FTIR absorption and PL emission bands reflect a strong dipolar association and a formation of at least two types of 5CB dimeric structures with antiparallel or parallel orientation in the planar configuration. No formation of hydrogen bonds between the cyano groups and hydrogen atoms of the adjacent benzene ring has been found. Besides, a small amount of the 5CB monomer structure has been shown to be present in all phases. The observed temperature-induced changes in the IR and PL spectra can be used as an independent source of experimental information on conformational equilibria and structure alignment of 5CB in different states under the phase transitions.

Weighted LASSO variable selection for the analysis of FTIR spectra applied to the prediction of engine oil degradation

The aim of this work is to quantify the relationship between different methods of artificial oil alteration as well as engine oils collected from a passenger car using FTIR (Fourier-transform infrared) spectroscopic data and chemometric methods. We propose a comprehensive procedure for the analysis of FTIR spectra: First, a reconstruction error based pre-processing to filter non-informative variables is introduced, then simultaneous variable selection and parameter estimation using the (weighted) LASSO is performed. Eventually, post-selection inference is applied to derive confidence intervals for the selected model coefficients. The proposed pre-processing methods do not rely on manual selection of FTIR absorption bands suitable for analysis but perform filtering of non-informative variables objectively. With weighted LASSO, experts’ knowledge can be integrated with the model. This pipeline for the analysis of FTIR spectroscopic data is demonstrated and validated on a real-world dataset including series of FTIR spectra of used and artificially altered engine oils.

Removal of Fe (II) ions from Aqueous solution using Rice-husk Adsorbents in fixed-bed column

Rice husk has been converted into activated carbon for the adsorbent to remove the heavy metal from the aqueous solution. This study aimed to convert rice husk to activated carbon (AC) for use in the adsorption of Fe ions in a fixed-bed column. Rice husk was first pyrolyzed in an atmosphere of nitrogen gas at 400 oC, then a chemical activation method using sodium hydroxide. The rice husk activated carbon (RH-AC) was characterized using Fourier transform infrared (FTIR) and Scanning electron microscope (SEM) to identify the functional group and microstructure of carbon. The performance of the carbon was tested on the Fe removal from an aqueous solution in a continuous column. The adsorption process was carried out using Fe solution with an initial concentration of 3 mg/L as an artificial sample. The amount of carbon is 25, and 50 g were filled in an adsorber column with a diameter of 5.4 cm and height of 40 cm. SEM images revealed that the activated carbons shown with well-developed pore sizes and pore structure were produced after the chemical activation. The FTIR absorption bands observed in the RH-AC sample confirmed the presence of hydroxyl (-OH), carbonyl, and carboxylic (-COOH) groups of RH-AC adsorbent. The highest Fe removal efficiencies were 91.9% on chemically activated carbon and column mass 50 g at 400 minutes. The overall study revealed the potential value of chemically activated RH-AC as a possible commercial adsorbent in a continuous column wastewater treatment strategy.

FTIR spectral band shifts explained by OM–cation interactions

AbstractBackground: The organic matter (OM) in soils interacts with polyvalent cations such as Ca2+ through hydroxyl (OH), carboxylic acid, ester, keto, aldehyde (summarized as C=O), and carboxylate (COO−) functional groups. Such interactions affect the bonding strength of the double bond between the C and the O atom in the functional groups, which is assumed to shift the wavenumber (WN) region of O–H (hydroxyl), C=O, COO−, and OMcat (i.e., C=O interacting with cations plus O–H groups) absorption band maxima in the Fourier transform infrared (FTIR) spectra. Such band shifts limit the evaluation of spectral information on OM in soil samples.Aims: The objective of this study was to analyze the extent of band shifts and the changes in absorption band intensities for relations with cation concentrations, and to estimate effects of band shifts on OM properties such as potential wettability of OM evaluated from FTIR absorption band ratios.Methods: Polygalacturonic acid (PGA) solutions were mixed with a CaCl2 solution at different relations. The freeze‐dried mixtures were analyzed with FTIR spectroscopy in the mid‐infrared spectral range by using KBr‐technique. The FTIR spectra were interpreted with respect to O–H, C=O, COO−, and OMcat bands, the latter reflecting the formation of PGA‐Ca2+ complexes.Results: The FTIR spectra of the PGA–Ca mixtures compared to that of pure PGA indicate band shift effects by CaCl2 addition on both, intensity and WN value of the OMcat, C=O and COO− absorption band maxima. The COO−/C–O–C ratio increased with Ca2+ concentration while the C–H/C–O–C ratio decreased. Furthermore, the C=O and COO− absorption band maxima were shifted towards lower WN values, while the OMcat absorption band was shifted towards higher WN values. The shift of OMcat band maxima was two times higher than that of the C=O band maximum and increased with Ca2+ concentration.Conclusion: Spectral band shifts depend on polyvalent cation concentration and limit automated interpretations of FTIR spectra without prior soil‐specific spectral corrections.

Molecular characteristics and antioxidant activity of laminarin extracted from the seaweed species Laminaria hyperborea, using hydrothermal-assisted extraction and a multi-step purification procedure

The objective of this study was to determine the effect of hydrothermal-assisted extraction (HAE) and a multi-step purification process on the molecular characteristics and antioxidant activity of extracts of laminarin from the brown seaweed Laminaria hyperborea. The HAE with optimised extraction conditions (time - 30 min; temperature - 99.3 °C; sample to solvent ratio - 1:21.3 (w/v)) resulted in 368 mg/g laminarin in the Crude Extract. Purification using solvents, molecular weight cut-off filter (MWCO; 10 kDa) and solid-phase extraction (SPE) improved the concentration to 542.6 mg/g, 906.6 mg/g and 862.5 mg/g on dry weight extract basis, respectively (p < 0.05). The crude HAE extract had greater antioxidant activity, as determined by 1,1-diphenyl-2-picryl-hydrazyl radical scavenging and ferric reducing antioxidant power assays, than the purified fractions (p > 0.05). The identification of a chromatographic peak at 17.66 min (retention time) and FT-IR (Fourier transform infrared) absorption bands at 1420 cm−1 (carboxyl groups), 2950 cm−1 (C-H stretch) and at 2410 cm−1 (transmitting angle peak) was similar between the purified samples and a laminarin standard that was used as a control, confirming the presence of laminarin. The quadruple time of flight mass spectrometry (Q-ToF-MS) confirmed the molecular weight of purified laminarin was in the range of 5.7 kDa–6.2 kDa. HAE under optimised conditions was an effective method to recover biologically active laminarin from L. hyperborea. A multi-step purification, involving solvents and MWCO filters in a sequence could improve the purity of laminarin, however, purification reduced the antioxidant activity compared to the crude HAE extract.

Surface modification of MWCNT and its influence on properties of paraffin/MWCNT nanocomposites as phase change material

ABSTRACTMultiwalled carbon nanotubes (MWCNTs) were modified by an organo‐silane in order to improve their dispersion state and stability in paraffin wax. A family of paraffin‐based phase change material (PCM) composites filled with MWCNTs was prepared with different loadings (0, 0.1, 0.5, and 1 wt%) of pristine MWCNTs and organo‐silane modified MWCNTs (Si‐MWCNT). Structural analyses were performed by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and rheological studies using temperature sweeps. Moreover, phase change transition temperatures and heat of fusion as well as thermal and electrical conductivities of the developed PCM nanocomposites were determined. The SEM micrographs and FTIR absorption bands appearing at approximately 1038 and 1112 cm−1 confirmed the silane modification. Differential scanning calorimetery (DSC) results indicate that the presence of Si‐MWCNTs leads to slightly favorable enhancement in the energy storage capacity at the maximum loading. It was also shown that the thermal conductivity of the PCM nanocomposites, in both solid and liquid phases, increased with increasing the MWCNT content independent of the kind of MWCNTs by up to about 30% at the maximum loading of MWCNTs. In addition, the modification of MWCNTs made the samples completely electrically nonconductive, and the electrical surface resistivity of the PCMs containing pristine MWCNTs decreased with increasing MWCNTs loading. Furthermore, the rheological assessment under consecutive cyclic phase change demonstrated that the samples containing modified MWCNTs are more stable compared to the PCM containing pristine MWCNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48428.

Classification of gallstones using Fourier-transform infrared spectroscopy and photography

BackgroundGallstones have conventionally been classified by gross inspection into 4 categories: cholesterol gallstones, black pigment (calcium bilirubinate) gallstones, brown gallstones, and mixed gallstones that contain both cholesterol and calcium bilirubinate. Classification using Fourier-transform infrared (FT-IR) spectroscopy supplements gross inspection; however, the issue of ambiguity in gallstone classification has not been fully addressed to date.MethodsTwenty-six gallstones obtained after surgical gallbladder removal were examined using FT-IR spectroscopy and digital photography, and classified into 6 gallstone groups according to characteristic FT-IR absorption bands.ResultsFT-IR spectra of nine gallstones matched well with that of pure cholesterol, and the gallstones were thus classified as cholesterol stones. Twelve gallstones were classified as calcium bilirubinate stones as they showed characteristic absorption bands of calcium bilirubinate. However, the FT-IR spectra of these gallstones always showed a broad absorption band of bound water at 3600–2400 cm− 1. The other five gallstones were classified as mixed stones with combinations of cholesterol, calcium bilirubinate, and calcium carbonate.ConclusionFT-IR spectroscopy is a powerful and convenient method for gallstone classification. Nevertheless, one should take serious note of the superposition of FT-IR absorption bands of different chemical components of gallstones including that of bound water.

Preparation and characterization of nanocarbons from &lt;i&gt;Nicotiana tabacum stems&lt;/i&gt;

Nanocarbon materials can improve adsoption capacity if the nano size range is optimized during production. In this study, nanocarbons were prepared from green recyclable waste N. tabacum stem using carbonization process and KOH as the activating agent, thus potentially unclocking value in the otherwise waste material. The formation of nanocarbons was investigated at different KOH concentration, activation temperature and carbonization time. Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques were used to characterise the nanocarbon material. The results showed that nanocarbons with high specific surface areas in excess of 950 m 2 /g and nanostructured morphologies characterized by pore width averages ranging from 3.33–8.87 nm, pore diameter 10.59–45.30 nm and particle size 25.34–54.88 nm could be formed. Optimum nanocarbon production was achieved when the precursor was activated using 10% KOH and carbonized at a temperature of 400 ℃ for 4 h. Characteristic FT-IR absorption bands were observed in all carbonized samples. SEM images revealed a dense irregular material with cavities and protuberances. XRD patterns showed that crystallinity of the nanocarbons decreased with increase in carbonization time. The properties reported for the nanocarbons are ideal for adsoption of analytes from complex matrices, hence presenting N. tabacum as a promising low-cost and green alternative precursor for nanocarbon production targeting analytical fields such as solid-phase extraction and solid phase microextraction. The produced nanocarbons appear to be carbon nanoparticles comprising nearly spherical particles.

EVALUATION OF CALLINECTES CHITOSAN AS A SUPERDISINTEGRANT IN METRONIDAZOLE TABLET

Objective: The objective of this study is to evaluate callinectes chitosan as a superdisintegrant in tablet formulation; superdisintegrants are incorporated into tablets at concentrations below 5% of tablet weight to effect prompt break-up of tablets after administration.Methods: Chitosan was extracted from shells of Callinectes gladiator. The polymer was characterized and then used as a disintegrant (in comparison with Ac-Di-Sol® and corn starch) at concentrations of 2, 4 and 8% for the formulation of metronidazole tablets. The micromeritic properties of granules; and mechanical and release properties of the tablets were studied.Results: A yield of 36.7% chitosan having degree of deacetylation of 62.7% was obtained from the crab shell. Fourier Transform Infrared absorption bands at 1495 and 3240 cm-1 typical of N-H bending and stretching respectively; and endothermic peak of 159 °C typical of melting of chitosan were obtained. No adverse interaction between the chitosan and metronidazole was observed. The disintegration times of tablets containing 2, 4 and 8% chitosan were 12.2, 10.4 and 9.3 min respectively.Conclusion: Callinectes chitosan is suitable for use as a superdisintegrant in tablets. It appears to be superior to corn starch as disintegrant although less effective compared to Ac-Di-Sol®. However, the relative cheapness and ready availability of chitosan would make it to be preferred to Ac-Di-Sol®.

Crystal-Chemical Regularities and Identification Criteria in Fe-Bearing, K-Dioctahedral 1M Micas from X-ray Diffraction and Infrared Spectroscopy Data

AbstractIron-bearing K-dioctahedral 1M and 1Md micas are abundant in diverse geological environments and vary in composition from illite to celadonite through Fe-illite, Al-glauconite, and glauconite. The chemistry and structural features of these micas are complex and heterogeneous, reliable diagnostic criteria are lacking, and the conventional mineralogical nomenclature is ambiguous, which complicate the identification of these mica varieties. The objectives of the present study were to reveal the structural and crystal-chemical variability in Fe-bearing, K-dioctahedral 1M micas and to define composition ranges and identification criteria for the mica varieties in the series. A collection of samples of various compositions was studied using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Analysis of the relationships between unit-cell parameters and cation composition showed that the series included four groups, namely, Fe-bearing illites, Al-glauconites, glauconites, and celadonites and each group was characterized by a specific combination of unit-cell parameters and variation ranges. The illite group contained two distinct subgroups; Fe-bearing, Mg-rich illites and Feillites; which differ in the range of cation compositions and in FTIR characteristics. The boundary between Fe-illites and Al-glauconites occurs at a unit cell b value of ~9.05 Å and at ratios of octahedral Al to total trivalent octahedral cations that range between 0.60 and 0.65. The partially overlapping cation composition and cell parameter ranges may complicate the distinction between Al-glauconites and glauconites, which can still be unambiguously differentiated using FTIR data. The dramatically different XRD and FTIR characteristics confirmed that glauconite and celadonite should be treated as separate mineral species. The distinctive features of celadonite are relatively low csinβ values and reduced |ccosβ/a| values combined with b parameters lower than glauconites, but similar to Fe-illites. Celadonites also have distinct and sharp FTIR absorption bands at specific positions in the Si-O and OH stretching regions.

One-pot and green synthesis of Mn3O4 nanoparticles using an all-in-one system (solvent, reactant and template) based on ethaline deep eutectic solvent

Mn3O4 nanoparticles have been synthesized using a facile and sustainable method using ethaline (ethylene glycol–choline chloride) deep eutectic solvent (DES). The as-synthesized nanoparticles have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, UV/vis absorption spectroscopy, and vibrating sample magnetometry (VSM). The XRD results point to crystallization of hausmannite Mn3O4 in tetragonal crystal structure with average crystallite size of 18 nm. The microscopy-elemental investigations suggest the synthesis of spherical nanoparticles with average particle size of 25 nm and high elemental purity. The obtained band gap of 3.4 eV for the as–synthesized Mn3O4 nanoparticles indicates the semiconductor nature of nanoparticles. FTIR absorption bands further confirm the formation of pure Mn3O4 nanoparticles. The magnetic characterization of as-synthesized Mn3O4 nanoparticles clearly reveals their paramagnetic behavior at room temperature. Based on our proposed mechanism the ethaline plays a triple role (solvent, reactant, and template) during the synthesis thereby it provides a green all-in-one system for synthesis, stabilization and better control over growth of Mn3O4 nanoparticles.

English

The surface composition and surface properties of water hyacinth (Eichhornia crassipes) root biomass were studied before and after extraction with dilute nitric acid and toluene/ethanol (2/1, v/v) followed by ethanol, using Fourier Transform Infra-red (FT-IR) spectroscopy, thermogravimetric analysis, x-ray diffraction, scanning electron microscopy. FT-IR absorption bands were obtained at 3421, 2855, 1457 and 1035 cm-1 (O-H stretch, C-H vibration, C-H asymmetric deformation, and C-O stretch, respectively) and 1508, 1541 and 1559 cm-1 (all aromatic skeletal vibrations characteristic of lignin), as well as a C=O carboxylate stretch vibrational band at 1654 cm-1. Scanning electron microscopy confirmed the root biomass to be amorphous and not to have a strongly structured surface. The dilute mineral acid and organic solvent treatment increased crystallinity. Thermogravimetric analysis Studies show that the treated biomass are more thermally stable than the untreated biomass. Data are presented showing that dilute mineral acid and organic solvent treatment resulted in a decrease in the amount of lignin in the biomass. The implications of the decrease in the percentage of lignin on the adsorption of volatile polar organic solvents and non-polar n-alkane hydrocarbons is discussed. Key words: Water hyacinth, biomass, surface composition, Fourier Transform Infra-red (FT-IR) spectroscopy, scanning electron microscopy, x-ray diffraction spectroscopy, thermo gravimetric analysis.

The evolution of dehydration and thermal decomposition of nanocrystalline and amorphous chromium hydroxide

Chromic oxide was synthesized through the dehydration and thermal decomposition of nanocrystalline and amorphous chromium hydroxide. The dehydration of amorphous chromium hydroxide had been researched clearly over the past few decades. Here, we mainly explored the different dehydration process between crystalline and amorphous chromium. The two samples were prepared by a simple one-step precipitation at 5°C and 25°C, and characterized using X-ray diffraction and high resolution transmission electron microscopy. The evolution of dehydration and thermal decomposition behaviors of the two samples were measured by derivative thermogravimetry and Fourier transform infrared (FT-IR) spectrometry. The dehydration of nanocrystalline chromium hydroxide occurred at 105°C, 289°C, and 409°C, whereas that of amorphous chromium hydroxide occurred at 70°C, 289°C, 406°C, and 443°C. At approximately 289°C, the actual quality of dehydration was only one water molecule, which was in agreement with the theoretical result (expressed as CrOOH). The FT-IR absorption bands at 3370 and 1620cm⿿1 gradually decreased in intensity with increasing annealing temperature and then finally disappeared at 600°C to become α-Cr2O3.

Interactions of the Anticancer Drug Tamoxifen with Lipid Membranes

Interactions of the hydrophobic anticancer drug tamoxifen (TAM) with lipid model membranes were studied using calcein-encapsulated vesicle leakage, attenuated total reflection Fourier transform infrared (FTIR) spectroscopy, small-angle neutron scattering (SANS), atomic force microscopy (AFM) based force spectroscopy, and all-atom molecular dynamics (MD) simulations. The addition of TAM enhances membrane permeability, inducing calcein to translocate from the interior to the exterior of lipid vesicles. A large decrease in the FTIR absorption band’s magnitude was observed in the hydrocarbon chain region, suggesting suppressed bond vibrational dynamics. Bilayer thickening was determined from SANS data. Force spectroscopy measurements indicate that the lipid bilayer area compressibility modulus KA is increased by a large amount after the incorporation of TAM. MD simulations show that TAM decreases the lipid area and increases chain order parameters. Moreover, orientational and positional analyses show that TAM exhibits a highly dynamic conformation within the lipid bilayer. Our detailed experimental and computational studies of TAM interacting with model lipid membranes shed new light on membrane modulation by TAM.

X-Ray Diffraction and Vibrational Spectroscopic Characteristics of Hydroxylclinohumite from Ruby-Bearing Marbles (Luc Yen District, Vietnam)

A honey-yellow hydroxylclinohumite from ruby-bearing marbles of the Luc Yen district in northern Vietnam was characterized by electron microprobe (EPMA), single-crystal X-ray diffraction (XRD), micro-Raman, and Fourier-transform infrared (FTIR) spectroscopy. The studied crystals correspond to nearly ideal clinohumite with the structural formula 4[Mg2SiO4]·[(Mg,Fe,Ti)(OH,F)2] and roughly equal F and OH proportions. Crystal structure analysis showed Ti substitution for Mg only at the Mg3 site. A Fourier-difference map revealed one hydrogen site associated with ninth oxygen atom. The calculated O–H bond distance was shorter than that in other natural clinohumites. FTIR revealed bands corresponding to combination of OH-stretching with Mg–OH and/or Fe–OH bending modes, combinations of OH−and Fe–OH vibrations, combination of fundamental bands of the Si–OH bonding, combination of OH−and Si–OH vibrations, and first (2νOH) and the second (3νOH) overtones of the OH-stretching vibration mode. Two groups of OH-stretching vibration and FTIR absorption bands at 3390–3420 cm−1and 3560–3580 cm−1show reversible temperature-dependent shift. The low-frequency bands absent in pure synthetic hydroxylclinohumites are assigned to OH-planar defects caused by Ti-for-Mg substitution.

Transesterification of Palm Oil Catalyzed by Fresh Water Bivalve Mollusk (Margaritifera falcata) Shell as Heterogeneous Catalyst

A heterogeneous catalyst has been derived from a waste material of fresh water bivalve mollusk (i.e., Margaritifera falcata outer shell) for the transesterification of palm oil. The shell was washed, crushed, ground, and calcined at 850 °C to derive active CaO catalyst. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), and differential thermal analysis/thermogravimetric (DT/TG) analysis. The DT/TG analysis showed the decomposition of calcium carbonate present in the shell at 780 °C. The XRD peaks for calcined shell were observed at 2θ = 32.22°, 53.53°, and 64.03° characteristics of CaO and showed high crystallinity. The textural structure of shell can be observed from the SEM images indicated that the structure of shell changed with calcination temperature. The FTIR absorption bands of the calcined shell were observed at 1471, 1090, and 874 cm–1, which are attributed...

Magnetic dilution effect of nano-crystalline NiFe2O4 synthesized via sucrose-assisted combustion route

Sucrose assisted combustion route was utilized to synthesize nano-crystalline Cr-substituted nickel ferrites, NiFe2−xCrxO4 (x=0.0–1.0). The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) techniques to investigate the effect of Cr-substitution on the structural and magnetic properties of the entire system. Single-phase formation was checked using XRD and a proper cation distribution was estimated depending on the related structural parameters. FT-IR absorption bands were found to be in the expected range, which fortifies the spinel formation. The change in the structural properties by the addition of Cr3+ ions was discussed from the view point of ionic radii of the entire ions. TEM revealed the agglomeration nature of the synthesized powders. The magnetic properties were strongly affected by Cr-substitution. The decrease in the saturation magnetization and coercivity with increasing Cr-content was attributed to magnetic moments and magneto-crystalline anisotropy of the entire ions, respectively.

Exoskeleton of a Mollusk (Pila globosa) As a Heterogeneous Catalyst for Synthesis of Biodiesel Using Used Frying Oil

A heterogeneous catalyst has been derived from a waste material (i.e., exoskeleton of mollusk) for transesterification of a waste feedstock (i.e., used frying oil (UFO)) for synthesis of biodiesel. The exoskeleton of mollusk shell was crushed, ground, and calcined at 900 °C to derive CaO as a heterogeneous catalyst. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray fluorescence spectroscopy (XRF), and differential thermal analysis/thermogravimetric (DT/TG) analysis. The XRD peaks observed at 2θ = 31.80, 36.93, and 53.37° were characteristic of CaO and showed high crystallinity. The FTIR absorption bands of the calcined shell were observed at 1474, 870, and 502 cm–1, which are attributed to the vibration of CO32– molecules, and a sharp peak at 3640 cm–1 indicated the presence of OH– stretching due to Ca(OH)2. The XRF analysis demonstrated the Pila globosa shell to comprise 79.86% of calcium along with few minor elements (viz. Pd, I, Te, Sb, Sn,...

Highly efficient and selective infrared absorption material based on layered double hydroxides for use in agricultural plastic film

An aminotrimethylenephosphonic acid (ATMP, C 3H 12NO 9P 3) with strong IR absorption in the range from ca. 7.7 to 11 μm was intercalated into layered double hydroxides (LDH) host by anion-exchange method using Mg 2Al–NO 3 LDH as the precursor. The prepared product was characterized using inductively coupled plasma emission spectrometer (ICP), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM) as well as thermogravimetry and differential thermal analysis (TG–DTA). The observed expansion of interlayer spacing of the LDH in the XRD pattern and the disappearance of the FT-IR absorption band for NO 3 – anions found in the precursor suggest that the guest anions have been successfully intercalated into the LDH interlayer spacing to form organic–inorganic composite. Intercalation in the LDH host improves the thermal stability of the ATMP. When it is incorporated in low density polyethylene (LDPE) film, furthermore, the ATMP intercalated LDH significantly enhances the IR absorption ability of the LDPE film, in particular, the IR selectivity in the range 9–11 μm, which is the main wavelength range of IR irradiation from the earth's surface to the atmosphere at night. In addition, the composite aids to enhance the thermal stability of the LDPE film without negative influence on visible light transmittance and mechanical properties. The intercalated LDH is therefore expected to have practical applications as heat retention additives in agricultural plastic films.

Electrical properties and reactivity under air–CO flows of composite systems based on ceria coated carbon nanotubes

Nanocomposite systems of ceria nanoparticles and Double Walled Carbon Nanotubes (DWNTs) coated with nano-ceria (n-CeO 2) were elaborated using a classical sol gel method. Three samples noted as [n-CeO 2 + xDWNTs] with variable weight fractions x = 0, 5 and 15 wt.% of DWNTs were obtained. The samples were characterized by X-ray diffraction and electron microscopy. The electrical conductivity of [n-CeO 2 + xDWNTs] compacted pellets systems was determined from electrical impedance spectrometry, under air, between 120 and 400 °C. In this temperature range, all samples were semi-conducting with a weak variation of activation energy. However, the conductivity strongly increased with the weight fraction of ceria coated carbon nanotubes. Finally, the solid–gas interactions between air–CO flows and these systems were studied as a function of time and temperature, by means of Fourier transform infrared (FTIR) spectroscopy. The oxidation kinetics of CO into CO 2 was analyzed from the evolutions of FTIR absorption band intensities. As the carbon nanotube fraction x increased, the conversion efficiency was strongly improved.