IR CO2 Research Articles

Design and fabrication of poly-Si/SiO2 Fabry–Perot filter for nondispersive IR CO2 sensors

The relationship between the transmittance and FWHM of a Fabry–Perot filter for a nondispersive carbon dioxide (CO2) sensor was investigated as a function of the number of distributed Bragg reflector (DBR) pairs consisting poly-Si and SiO2 thin films. Given the significant prior research on the fabrication of high-performance Fabry–Perot filters, this study is focused on the relationship between the transmittance and FWHM that can be achieved by controlling the reflectance of the DBR pairs. Each layer of the filter was simulated adequately as the poly-Si and SiO2-based DBR pairs, and poly-Si and SiO2 were deposited on the soda–lime substrate by RF sputtering and low-pressure chemical vapor deposition based on the simulation results. The fabricated filter showed a transmittance of 43.7% and FWHM of 125 nm at 4.26 μm. The NDIR CO2 sensor with Fabry–Perot filter showed enhanced selectivity to CH4 and CO compared with normalized CO2 response.

A direct relationship between the sensitivity of the sensors and the intensity of IR CO2 peak in in situ FTIR-LCR meter chemi-impedance SnO2–carbon nanoparticles polymer-based sensors in the detection of organic compounds vapor

Three sensors were prepared with SnO2, carbon nanoparticles (CNPs), and cellulose acetate (CA) composites, and each sensor containing different amounts of SnO2 powder were prepared for the detection of n-dodecane, 2-hexanone, and 3-methylcyclopentanone vapor at room temperature. Sensors with a combination of CNP:CA, SnO2:CA, SnO2:CNPs, and SnO2 composites were used as control, and their performance was compared with that of the sensor based on SnO2:CNPs:CA toward a wide range of 2-hexanone and 3-methylcyclopentanone vapor concentrations. Sensors based on CNPs:CA and SnO2:CNPs:CA selectively responded very well to 3-methylcyclopentanone and 2-hexanone, respectively. The in situ FTIR study revealed that both sensors undergo a deep oxidation process during sensing and the sensitivity of the sensors directly relates to the IR intensity of the CO2 peak at 668 cm−1, and for highly sensitive sensors, the CO2 peak at 668 cm−1 is found to be very intense. The gradient area under the curve of the IR CO2 band at 668 cm−1 against time for more sensitive sensors toward the analyte is larger than that for less sensitive ones. The effect of the amount of SnO2 in the composites indicated that the sensors based on three sensing materials combined at a mass ratio of 1:1:3 were highly selective toward 3-methylcyclopentanone and less selective toward the other two analytes. Sensors based on the composition of SnO2:CNPs:CA at a mass ratio of 1.5:1:3 and those based on the composition of SnO2:CNPs:CA at a mass ratio of 2:1:3 were selective toward 2-hexanone and n-dodecane, respectively. All the fabricated sensors were found to have their sensing ability regenerated after the analytes were removed from the system without losing their sensing and recovery abilities.

Liquid crystal aligning using different approaches

In the current paper the classical and new relief at the interface: solid substrate-liquid crystal mesophase is presented in order to orient the liquid crystal molecules with good advantage. Rubbing technique, some geometric construction at the interface, UV and VIS treatment of the polymers, and laser oriented method are shown. The last one is connected with the materials surface relief modification using the laser-matter interaction process by the application of the IR CO2–laser at the wavelength of 10.6 micrometers. As the efficient nano-objects applied for the relief improvement the carbon nanotubes with the small refractive index close to 1.1 and the large Young’s modulus are used. As an additional, the varied electric field of 100-600 V/cm is applied in order to deposit the carbon nanotubes at the materials surfaces in the vertical position and to form the covalent bonding between the carbon atoms and the model matrix materials surface atoms. The novel results are shown in comparison with that obtained before for the classical orienting liquid crystal molecules methods. It extends dramatically the area of the liquid crystal cells use.

Amine-based carbon dioxide absorption: evaluation of kinetic and mass transfer parameters

Global emission of carbon dioxide (CO2), a major contributor to the climate change, has increased annually and it reached over 37 Gt in 2017. An effort to reduce the emission, therefore, needs to be conducted, e.g. post-combustion capture by use of amine-based absorption. The objective of this study is to evaluate the kinetic and mass transfer parameters in a CO2 absorption process using monoethanolamine (MEA), 2-(methylamino)ethanol (MMEA), and 2-(ethylamino)ethanol (EMEA) as absorbents. The experiments were conducted in a bubble reactor at atmospheric pressure and 40 °C with 10-vol% CO2 flowrate of 5 NL/men. The CO2 concentration leaving the reactor was measured by an IR CO2 analyzer. The results obtained from this experiment were the overall absorption rates consisting of both chemical reaction and mass transfer. Analysis result shows that the reaction between CO2 and amines takes place fast, therefore the mass transfer of CO2 from the gas into the liquid through the gas film would control the overall absorption rate.

CO2 methanation over Fe- and Mn-promoted co-precipitated Ni-Al catalysts: Synthesis, characterization and catalysis study

The methanation reaction of CO2 is in discussion to be a sustainable pathway to address future questions arising from limited primary energy feedstock and the accumulation of CO2 in the atmosphere. Therefore, the development of highly active and thermostable catalysts for this reaction is an indispensable matter of research. For this reason, an equimolar NiAlOx benchmark catalyst (44 wt.% Ni loading) was synthesized and modified by doping with Fe or Mn up to 10 wt.% of promoter by co-precipitation at constant pH 9. Their activity and stability performances in the CO2 methanation reaction were evaluated by comparing the conversion versus temperature characteristics before and after an aging period of 32 h at 500 °C. Material characterization studies comprising BET, XRD, in situ IR spectroscopy, XPS, H2 and CO2 chemisorption, and EPR/FMR contributed to derive structure-activity relationships and to obtain a deeper understanding of the catalytic behavior. Promotion with Mn led to a significant enhancement of the catalytic activity. This is assumed to be caused by a higher density of medium basic sites and an enhanced CO2 adsorption capacity on the activated catalyst related to interactions between Mn oxide species and the mixed oxide phase, in combination with a stabilization of the Ni surface area at moderate Mn loadings. Promotion with Fe increased the thermal stability of the catalyst, which is attributed to the formation of a Ni-Fe alloy during catalyst activation. For both phenomena, the optimum molar Ni to promoter ratio for co-precipitated catalysts was found to be around 5.

Insight into catalytic reduction of CO2 to methane with silanes using Brookhart's cationic Ir(iii) pincer complex.

Using density functional theory computations, we investigated in detail the underlying reaction mechanism and crucial intermediates present during the reduction of carbon dioxide to methane with silanes, catalyzed by the cationic Ir-pincer complex ((POCOP)Ir(H)(acetone)+, POCOP = 2,6-bis(dibutylphosphinito)phenyl). Our study postulates a plausible catalytic cycle, which involves four stages, by sequentially transferring silane hydrogen to the CO2 molecule to give silylformate, bis(silyl)acetal, methoxysilane and the final product, methane. The first stage of reducing carbon dioxide to silylformate is the rate-determining step in the overall conversion, which occurs via the direct dissociation of the silane Si–H bond to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O bond of a weakly coordinated Ir–CO2 moiety, with a free energy barrier of 29.5 kcal mol−1. The ionic SN2 outer-sphere pathway in which the CO2 molecule nucleophilically attacks at the η1-silane iridium complex to cleave the η1-Si–H bond, followed by the hydride transferring from iridium dihydride [(POCOP)IrH2] to the cation [OC–OSiMe3]+, is a slightly less favorable pathway, with a free energy barrier of 33.0 kcal mol−1 in solvent. The subsequent three reducing steps follow similar pathways: the ionic SN2 outer-sphere process with silylformate, bis(silyl)acetal and methoxysilane substrates nucleophilically attacking the η1-silane iridium complex to give the ion pairs [(POCOP)IrH2] [HC(OSiMe3)2]+, [(POCOP)IrH2] [CH2(OSiMe3)2(SiMe3)]+, and [(POCOP)IrH2] [CH3O(SiMe3)2]+, respectively, followed by the hydride transfer process. The rate-limiting steps of the three reducing stages are calculated to possess free energy barriers of 12.2, 16.4 and 22.9 kcal mol−1, respectively. Furthermore, our study indicates that the natural iridium dihydride [(POCOP)IrH2] generated along the ionic SN2 outer-sphere pathway could greatly facilitate the silylation of CO2, with a potential energy barrier calculated at a low value of 16.7 kcal mol−1.

Thallium indium germanium sulphide (TlInGe2S6) as efficient material for nonlinear optical application

Article reports design and synthesis, technology, crystal structure determination and results of photoinduced nonlinear optical investigations of novel TlInGe2S6 crystals. We have discovered TlInGe2S6 as a new type of laser induced nonlinear optical materials. Following the performed measurements we can use the titled crystals for laser operated coherent wavelength transformations. It was shown, that thin, photoinduced nanolayers formed by laser energies above the energy gap as well a near the phonon resonances possess promising nonlinear optical properties. Different types of cw lasers with the same powers of the photoinduced beams were used: SHG of the Nd:YAG laser (532 nm), fundamental Nd:YAG laser (1064 nm), and IR CO2 laser with wavelength of 9400 nm.The crystal structure of novel quaternary thallium indium germanium sulphide TlInGe2S6 determined by X-ray powder method possesses trigonal space group R3. The as-derived TlInGe2S6 crystalline alloy was probed employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. Particularly, for the TlInGe2S6 alloy surface, both pristine and 3.0 keV Ar+ ion-irradiated, we have monitored the XPS valence-band and core-level spectra. These measurements indicate that the TlInGe2S6 surface is rather stable with respect to Ar+ ion-irradiation, which does not induce significantly near the surface layers sub-stoichiometry. Matching on a common energy scale of the XPS valence-band spectrum and the XES S Kβ1,3 and Ge Kβ2 bands indicates that main contributions of the S 3p and Ge 4p states are located in the upper and central portions of the valence band of TlInGe2S6, respectively, with significant contributions of these states in other valence-band parts as well.

Designing of optimised rescue robot using fuzzy inference system

The objective of this work is two-fold. First, this work focuses on detection of alive Homo sapiens. Second, it focuses on obstacle detection and collision avoidance. The main aim of this work is to maintain both needs simultaneously. To define the path more precisely, fuzzy set theory is used which tackle with the intermediate values of direction. A Sugeno fuzzy controller algorithm is used which takes three inputs labelled as obstacle position obtained through ultrasonic sensor, obstacle distance through IR sensor and CO2 sensor for finding presence of carbon-dioxide. The work is evaluated on different parameters. As compare to other rescue robots, the number of passes used by our proposed rescue robot is comparatively lesser. The other parameter is wheel computation which is used for measuring the motion. The proposed rescue robot is more flexible while determining its optimising path.

Designing of optimised rescue robot using fuzzy inference system

The objective of this work is two-fold. First, this work focuses on detection of alive Homo sapiens. Second, it focuses on obstacle detection and collision avoidance. The main aim of this work is to maintain both needs simultaneously. To define the path more precisely, fuzzy set theory is used which tackle with the intermediate values of direction. A Sugeno fuzzy controller algorithm is used which takes three inputs labelled as obstacle position obtained through ultrasonic sensor, obstacle distance through IR sensor and CO2 sensor for finding presence of carbon-dioxide. The work is evaluated on different parameters. As compare to other rescue robots, the number of passes used by our proposed rescue robot is comparatively lesser. The other parameter is wheel computation which is used for measuring the motion. The proposed rescue robot is more flexible while determining its optimising path.

Oxidative methane coupling over Mg, Al, Ca, Ba, Pb-promoted SrTiO3 and Sr2TiO4: Influence of surface composition and microstructure

Mg, Al, Ca, Ba, Pb-substituted titanates SrTi1−xAxO3 (A=Mg, Al, Ca, Ba, Pb, x=0.1) and Sr2Ti1−xAxO4 (A=Mg, Al, x=0.1) were synthesized using mechanochemical method (sintering at 1100°C in air for 4h) and tested in oxidative coupling of methane (OCM) at 850 and 900°C. The obtained samples were double-phase samples consisting of Mg, Ca, Ba substituted perovskite (SrTiO3) and “layered” perovskite – (Sr2TiO4 or Sr3Ti2O7). In case of Al and Pb, it was shown that these cations most probably did not replace Ti in the perovskite structure and formed the Sr3Al2O6 and SrPbO3 individual phases. The most active samples were Mg- and Al-doped SrTiO3 and Sr2TiO4, which in their mixture with inert quartz particles showed C2 yield up to 25% and C2 selectivity around 66%. Microstructure analysis of Mg-substituted titanates revealed that under reaction conditions the “layered” perovskite decomposed releasing (Sr, Mg)O mixed oxide segregated to the surface. The samples characterized by the highest surface content of the (Sr, Mg)O oxide, which was estimated by IR CO2 adsorption, demonstrated both the highest activity in methane activation and the highest rate of methyl radical generation to the gas phase. The influence of the (Sr, Mg)O segregation on the formation of active oxygen species is discussed.

Cloud Remote Sensing Using Midwave IR CO2 and N2O Slicing Channels near 4.5 μm

Narrow channels located in the longwave IR CO2 absorption region between approximately 13.2 and 14.5 μm, the well known CO2 slicing channels, have been proven to be quite effective for the estimates of cloud heights and effective cloud amounts as well as atmospheric temperature profiles. The designs of some of the near-future multi-channel earth observing satellite sensors cannot accommodate these longwave IR channels. Based on the analysis of the multi-channel imaging data collected with the NASA Moderate Resolution Imaging SpectroRadiometer (MODIS) instrument and on theoretical cloud radiative transfer modeling, we have found that narrow channels located at the midwave IR region between approximately 4.2 and 4.55 μm, where the combined CO2 and N2O absorption effects decrease rapidly with increasing wavelength, have similar properties as the longwave IR CO2 slicing channels. The scattering of solar radiation by clouds on the long wavelength side of the 4.3 μm CO2 absorption makes only a small contribution to the upwelling radiances. In order to retain the crucial cloud and temperature sensing capabilities, future satellite sensors should consider including midwave IR CO2 and N2O slicing channels if the longwave IR channels cannot be implemented on the sensors. The hyperspectral data covering the 3.7-15.5 mm wavelength range and measured with the Infrared Atmospheric Sounding Interferometer (IASI) can be used to further assess the utility of midwave IR channels for satellite remote sensing.

Spectroscopy study of air plasma induced by IR CO2 laser pulses

A spectroscopic study of ambient air plasma, initially at room temperature and pressures ranging from 32 to 101 kPa, produced by high-power transverse excitation atmospheric (TEA) CO2 laser (λ=9.621 and 10.591 μm; τ FWHM≈64 ns; power densities ranging from 0.29 to 6.31 GW cm−2) has been carried out in an attempt to clarify the processes involved in laser-induced breakdown (LIB) air plasma. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited N, O and ionic fragments N+. The medium-weak emission is due to excited species O+, N2+, O2+, C, C+, C2+, H, Ar and molecular band systems of N $_{2}^{+}($ B $^{2}\varSigma _{\mathrm{u}}^{+}$ –X $^{2}\varSigma _{\mathrm{g}}^{+})$ , N2(C3 Π u–B3 Π g), N $_{2}^{+}($ D2 Π g–A2 Π u) and OH(A2 Σ +–X2 Π). Excitation temperatures of 23400±700 K and 26600±1400 K were estimated by means of N+ and O+ ionic lines, respectively. Electron number densities of the order of (0.5–2.4)×1017 cm−3 and (0.6–7.5)×1017 cm−3 were deduced from the Stark broadening of several ionic N+ and O+ lines, respectively. Estimates of vibrational and rotational temperatures of N $_{2}^{+}$ electronically excited species are reported. The characteristics of the spectral emission intensities from different species have been investigated as functions of the air pressure and laser irradiance. Optical breakdown threshold intensities in air at 10.591 μm have been measured.

Temporal evolution of the laser-induced plasma generated by IR CO2 pulsed laser on carbon targets

Time-resolved optical emission analysis was carried out for the plasma plume, produced by high-power tunable IR CO2 pulsed laser ablation of graphite, at λ=10.591 μm and in a regime of relatively high laser fluences (123–402 J/cm2). Wavelength-dispersed spectra of the plasma plume, at medium-vacuum conditions (4 Pa) and at 9.0 mm from the target, show ionized species (C+, C2+, C3+, C4+, N2+ , N+, and O+), neutral atoms (C, H, N, and O), and neutral diatomic molecules (C2, CN, OH, CH, and N2). In this work, we focus our attention on the temporal evolution of different atomic/ionic and molecular species over a broad spectral range from 190 to 1000 nm. The results show a faster decay for ionic fragments than for neutral atomic and molecular species. The velocity and kinetic energy distributions for different species were obtained from time-of-flight measurements using time-resolved optical emission spectroscopy. Possible mechanisms for the production of these distributions are discussed. Excitation temperature, electron density, and vibrational temperature in the laser-induced plasma were estimated from the analysis of spectral data at various times from the laser pulse incidence.

Optical emission spectroscopy of oxygen plasma induced by IR CO2 pulsed laser

Laser-induced breakdown (LIB) spectroscopy in oxygen at room temperature and pressures ranging from 4.6 to 75 kPa was studied using a high-power transverse excitation atmospheric CO2 laser (λ = 9.621 and 10.591 µm; τFWHM = 64 ns; power densities ranging from 0.87 to 6.31 GW cm−2). The spectrum of the generated plasma is dominated by emission of strong O, O+ and weak O2+ atomic lines. Excitation temperatures of 31 500 ± 1600 K and 23 000 ± 3000 K were estimated by means of O2+ and O+ ionic lines, respectively. Electron number densities of the order of (3.5–16.5) × 1016 cm−3 were deduced from the Stark broadening of several ionic O+ lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the oxygen pressure and laser irradiance. Optical breakdown threshold intensities in O2 at 10.591 µm have been determined. The physical processes leading to LIB of oxygen have been analysed.

Spatial characterization of the laser-induced plasma plumes generated by IR CO2 pulsed laser on carbon targets

Spatially resolved optical emission analysis was carried out for the plasma plume, produced by high-power tunable IR CO2 pulsed laser ablation of graphite, at λ=9.621 μm and with laser fluence of 342 J cm−2. Wavelength-dispersed spectra of the plume, at medium vacuum conditions (Pair=4 Pa) and concentrated close to the target, reveal C, C+, C2+, C3+, C4+, N, H, O, and molecular emissions between different electronic states of C2, CN, OH, CH, and NH. The characteristics of the spectral emission intensities from different species have been investigated as functions of the distance (up to 20 cm) from the sample surface. Vibrational temperatures in the laser-induced plasma have been estimated at various distances from the target surface.

Optical emission spectroscopic study of plasma plumes generated by IR CO2 pulsed laser on carbon targets

Optical emission spectroscopy studies, in the spectral range ultraviolet–visible–near infrared (UV–Vis–NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm−2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C+, C2+ and C3+ and molecular features of C2(d 3Πg–a 3Πu; Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C4+ and molecular features of C2(; Freymark system), C2(; Mulliken system), CN(D 2Π–A 2Π), C2(e 3Πg–a 3Πu; Fox–Herzberg system), C2(C 1Πg–A 1Πu; Deslandres–d'Azambuja system), OH(A 2Σ+–X 2Π), CH(C 2Σ+–X 2Π), NH(A 3Π–X 3Σ−), CN(B 2Σ+–X 2Σ+; violet system), CH(B 2Σ+–X 2Π), CH(A 2Δ–X 2Π), C2(; Phillips system) and CN(A 2Π–X 2Σ+; red system). An excitation temperature Texc = 23 000 ± 1900 K and electron densities in the range (0.6–5.6) × 1016 cm−3 were estimated by means of C+ ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C2 and CN electronically excited species under various laser irradiance conditions are made.

Optical emission studies of nitrogen plasma generated by IR CO2 laser pulses**In Memoriam: Professor Antonio Pardo Martinez.

Large-scale plasma produced in nitrogen gas at room temperature and pressures ranging from 4 × 103 to 1.2 × 105 Pa by high-power laser-induced dielectric breakdown (LIDB) has been investigated. Time-integrated optical nitrogen gas spectra excited from a CO2 laser have been measured and analysed. The spectrum of the generated plasma is dominated by the emission of strong N+ and N and very weak N2+ atomic lines and molecular features of N+2(B2Σ+u–X2Σ+g), N+2(D2Πg–A2Πu), N2(C3Πu–B3Πg) and very weak N2(B3Πg–A3Σ+u). The relative intensities of the 0–0 band heads in the N2(C–B) and N+2(B–X) systems are very weak as compared with the chemiluminescence spectrum of nitrogen formed in a glow discharge. An excitation temperature Texc = 21 000 ± 1300 K was calculated by means of the relative intensity of ionized nitrogen atomic lines assuming local thermodynamic equilibrium. Optical breakdown threshold intensities in N2 at 9.621 µm have been determined. The physical processes leading to the LIDB of nitrogen in the power density range 0.4 < J < 4.5 GW cm−2 have been analysed. From our experimental observations we can suggest that, although the first electrons must appear via multiphoton ionization or natural ionization, electron cascade is the main mechanism responsible for the LIDB in nitrogen.

Laser-induced breakdown spectroscopy of trisilane using infrared CO2 laser pulses

The plasma produced in trisilane (Si3H8) at room temperature and pressures ranging from 50to103Pa by laser-induced breakdown (LIB) has been investigated. The ultraviolet-visible-near infrared emission generated by high-power IR CO2 laser pulses in Si3H8 has been studied by means of optical emission spectroscopy. Optical breakdown threshold intensities in trisilane at 10.591μm for laser pulse lengths of 100ns have been measured as a function of gas pressure. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited atomic H and Si and ionic fragments Si+, Si2+, and Si3+. An excitation temperature Texc=5600±300K was calculated by means of H atomic lines assuming local thermodynamic equilibrium. The physical processes leading to LIB of trisilane in the power density range 0.28GWcm−2&amp;lt;J&amp;lt;3.99GWcm−2 have been analyzed. From our experimental observations we can propose that, although the first electrons must appear via multiphoton ionization, electron cascade is the main mechanism responsible for the breakdown in trisilane.

Simple System for Rapid Determination of Carbon Dioxide Evolution Rates

abstract Measurement of CO2 evolution rates is important and necessary for many biological investigations because the rate is a common indicator of biological activity. The CO2 evolution rate of a sample can be determined quickly and sensitively with an IR CO2 analyzer. Many existing systems for determining CO2 evolution rates are quite complicated and expensive. They usually require removal of moisture in the testing air stream and a special gas mixture for calibration. The switching devices that allow analysis of multiple samples sequentially also further complicate the system. We present here a simple system—constructed from a commercially available CO2 analyzer and simple laboratory supplies— that analyzes CO2 evolution rates of multiple samples sequentially without special calibration gas mixtures or preremoval of moisture in the testing gas. The sensitivity and measuring range of the system can be conveniently adjusted by varying the sizes of the sample and the sample bottle. The lower detection limit of the system is 1.5 μl_/h, and the testing range is from 2 to 500 μL/h. The system is also portable for field applications.

Atmospheric refractive turbulence effect on diffraction-limited infrared coherent lidar

This paper, based on the Kavaya-Suni format, discusses the signal-to-noise ratio equation of the diffraction-limited coherent CO2 lidar in detail, which is applied to atmospheric turbulence. The cumulative SNR and relative SNR, which are all affected by the nonlinear effects of the diffraction-limited Gaussian beam, atmospheric molecule and atmospheric turbulence, are simulated by microcomputer. Six instructions for the optimal design of IR CO2 Coherent Lidar System, are provided.