Infrared Absorption Characteristics Research Articles

Artificial electron snorkels reduce CH4 emissions in paddy soil: Regulation of the electron transfer pathway and microbial community ecology

Climate science has focused on reducing emissions of atmospheric CH4 from paddy soils, as CH4 has stronger infrared absorption characteristics than CO2. Like cable bacteria, artificial electron snorkels (made of solid graphite rods) have been proposed in this study to provide potential remote electron acceptors for soil anaerobic metabolism to compete with methanogenic processes. A systematic investigation was conducted on the modulation of the CH4 emission dynamics by electron snorkels at different densities, as well as the associated metabolism of C/N/Fe in paddy soil. During 124 days of operation, the electron snorkels suppressed CH4 emissions by 7–31% over ten sampling periods, and the high-density setting exhibited stronger performance. The electron snorkels accelerated the early mineralization of soil organic matter, increasing the content of dissolved organic matter by 20–236%. These organics were utilized by microorganisms, where O2, NO3−, and Fe3+ acted as electron acceptors, enhancing soil alternative respiration and producing CO2. Metagenomic and 16S rRNA gene sequencing revealed that microbial abundance and diversity were increased by 4–71% in the soil bottom layer (7 cm–8 cm depth) driven by electron snorkels. Moreover, electron snorkels potentially prevented CH4 escape by either improving soil permeability or electrically stimulating the abundance of methanotrophs (e.g., Methylocystis). The ratio of methanogenic to methane-oxidizing gene abundances was reduced by 22–66% under the electron snorkels. Our results indicate that the applied electron snorkels have significant potential in enriching the soil microbial community involved in methane cycling to mitigate CH4 emissions from paddy fields.

The enhancement of infrared characterization of passivated InAs nanowires

Indium arsenide (InAs) nanowires (NWs) show significant advantages in optoelectronic devices due to their excellent electronic and optical properties. While the surface states affect such outstanding properties, and the performance of optoelectronic devices can be further optimized by modulating the surface state. Herein, the adsorption and substitution properties and the optoelectronics response of passivated InAs NWs are studied using first-principles calculations combined with nonequilibrium Green's function (NEGF). The results show that O atom adsorption can reduce the band gap and improve infrared absorption of InAs NWs. Meanwhile, for the O atom substitution model, the impurity energy level appears near the Fermi level of InAs NWs, and for a higher concentration O atoms substitution, the semiconduction properties of the InAs NWs are destroyed. We also choose the Au, Cs, Bi, Sn, and Y atoms as decoration atoms to passivate InAs NWs, and compared with the intrinsic InAs NW surface model, the energy bands gap of the metal-atoms adsorption models all show a decreasing trend in addition to Au-atom adsorption, and the absorption coefficients of InAs NWs adsorbed by several atoms such as Cs, Sn, Bi, and Y in the infrared region have redshifts in different degrees. The absorption coefficients of InAs NWs adsorbed by several metal atoms, Sn, Bi, and Y, are higher in the infrared region compared to that of InAs NW adsorbed by O atom. After the screening of materials, we select InAs NWs adsorbed with Cs, Bi, Sn, and Y atoms with good infrared absorption characteristics for the performance study of optoelectronic devices and it is shown that the InAs NW devices with adsorbed Bi and Sn atoms have the optimal performance with low dark current and high photocurrent.

Characterizing the Thickness Distribution of Donor and Acceptor in Organic Photovoltaics via Quasi‐Monochromatic Light Transmittance

AbstractThe performance of organic solar cells is sensitive to the film thickness and the uniformity of the donor and acceptor distribution in the photoactive layer. Especially, in the quasi‐planar heterojunction fabricated by layer‐by‐layer process, the donor and acceptor materials may be non‐homogeneously distributed across the entire photoactive layer. Visualization of the spatial distributions of donor and acceptor components sheds light on the relationship between nanostructures and device performances. Based on the distinct infrared absorption characteristics of the organic donor and acceptor, a quasi‐monochromatic light transmittance (QMLT) technique is proposed to quantify the donor and/or acceptor thickness in the photoactive layer blend across the entire device area with nanometer precision. The variation in thickness of donor and acceptor can be clearly and separately revealed. Accordingly, the impacts of spin coating techniques (such as dynamic or static dispensing, and on‐center or off‐center spin coating), as well as solvent choices, on film morphology and device performance can be correlated by the noncontact, nondestructive, and convenient QMLT method.

CoFe@[CoFe2O4/Fe(Co)Nx-C] nanoparticles prepared via an ultrasonic atomization coupling pyrolysis process and their magnetic and optical properties

Due to their special qualities, core-shell nanomaterials with two or more functionalities have drawn a lot of attention. Core-shell materials exhibit stronger combined electrical, optical, magnetic, and electronic characteristics than single-component nanomaterials thanks to the creation of the core-shell structure and the synergistic interaction between components. However, the formation of core-shell structures is often difficult due to the incompatibility between components, especially for lattice-mismatched core-shell structures. In this study, CoFe@CoFe2O4-N-C nanoparticles (∼150 nm) were successfully prepared via an ultrasonic atomization coupling pyrolysis process. This exhibits higher coercivity (108 Oe), saturation magnetization (52.3 emu/g) and Curie temperature (>400 K) than CoFe nanoparticles. At the same time, it exhibits high UV–Vis and infrared absorption characteristics and has good electronic properties as a direct band gap semiconductor material (bandgap of 2.87 eV). These characteristics suggest that CoFe@CoFe2O4-N-C NPs have a lot of potential in sectors like magneto-optics and absorbent materials.

Porous Si loaded with Ag nanoparticles for ultra-broadband infrared absorption and detection

With the rapid development of semiconductor technology, silicon based infrared detector chips have been greatly optimized with the help of MEMS process. The infrared absorber, as the core part of thermal detector, requires infrared absorption characteristics such as wide spectrum and high absorption. In this paper, two kinds of porous silicon materials loaded with Ag nanoparticles (Si@AgNPs), honeycomb-like and forest-like, were constructed by chemical etching method. The experimental results and corresponding analyses illustrated that micro- and nano-porous structures of silicon with arbitrary sizes and random spatial positions can have a great guiding effect on the light waves, providing multiple reflections and scattering, allowing increased light propagation paths and generating light trapping effect, leading to enhanced infrared absorption in a wide spectral range. AgNPs are loaded, and the collective oscillation of free electrons resonates with incident photons, thereby exciting plasmon resonance effect, which can further improve the infrared absorption properties of the material. Benefiting from the synergistic effect of light trapping and plasmon resonance, the porous Si@AgNPs with honeycomb-like or forest-like structure both exhibited high absorption properties at 2.5–20 μm. Moreover, the honeycomb-like Si@AgNPs also possessed optical interference effect, which can further enhance the absorption, compared with the forest-like Si@AgNPs.

Graphene-based H-shaped biosensor with high sensitivity and optimization using ML-based algorithm

In this paper, a biosensing absorber based on phase transition material is presented. Different phases of the Ge2Sb2Te5 (GST) substrate have been studied for the suggested absorber with controllable characteristics. The structure has been examined to determine the infrared absorption characteristics. The detection of varying volumes of hemoglobin and urine biomolecules is studied. The graphene-GST material is utilized for spectrum tuning. The tuning for two distinct phases of GST material, amorphous GST and crystalline GST is examined. The results for aGST and cGST are reported in the form of absorption. Different amounts of hemoglobin and urine biomolecules are used to tune these two GST stages. Based on the wavelength shifts at these various concentrations, the sensitivity is computed. The highest achievable sensitivity for hemoglobin and urine biomolecules is 1500 nm/RIU and 1667 nm/RIU. The developed model is observed for various geometrical parameters and incidence angles, from which it is determined that the suggested structure is insensitive to wide angles between 0° and 60°. For urine biomolecules, the aGST design is more sensitive than the cGST design, but similar results are achieved for hemoglobin biomolecules. Experiments are conducted with Machine Learning-based regression models to minimize the simulation time and resource requirements of biosensor design. The findings of the trials indicate that a regression model can accurately estimate the absorption values for intermediate wavelengths with an R2 score of 0.9999.

Development of triboelectric-enabled tunable Fabry-Pérot photonic-crystal-slab filter towards wearable mid-infrared computational spectrometer

Miniaturized optical spectrometers have been realized by exploiting conventional working principles and advanced nanofabrication technology. Especially in the mid-infrared (MIR) range, chip-scale optical spectrometers enable fast and on-site detection of molecular fingerprints for selective chemical sensing in healthcare and environmental monitoring. This miniaturization is also highly desirable for the wearable devices where the tiny functional parts remain on rigid substrates but the electronics are flexible. In the last decade, the triboelectric nanogenerator (TENG) technology has been proven as an indispensable and enabling technology for wearable self-powered sensors, energy harvesters and voltage sources, etc. Although a few TENG based gas sensors have been demonstrated, each of these sensors can detect a particular gas other than diversified gases. Infrared spectrometer is known as an instrument which can investigate the infrared absorption characteristics of gas molecules. It is the best generic technology to sense multiple gases on the same instrument, or device. In this study, we demonstrate a TENG enabled tunable Fabry-Pérot (FP) photonic-crystal-slab filter aiming for the computational spectrometer in the MIR range. The textile-triboelectric nanogenerator (T-TENG) provides high open-circuit voltage to shift the resonance wavelengths of the electrostatically actuated FP-filter, where this feature provides the sampling bases required for the computational spectrometer. Furthermore, the FP-filter is fabricated by a new transfer-printing method and shows a large wavelength tunability. As a proof of concept, the transmission spectrum of acetone vapor is reconstructed from 5 to 6.5 µm using this TENG enabled FP-filter. The molecular fingerprint of acetone is identified at 5.75 µm. This work paves the way towards the wearable MIR miniaturized optical spectrometer. • A MEMS tunable Fabry-Perot (FP) photonic-crystal-slab filter is fabricated by transfer-printing method. • The computational optical spectrometer is demonstrated for the first time with a single MEMS tunable device. • A textile-TENG is incorporated to tune the resonance of FP filter, forming the sampling bases for computational spectrometer. • The transmission spectra of CO 2 and acetone are reconstructed with their molecular fingerprints identified.

Standoff Detection of Plastics

Rapid identification of different plastics for recycling is very important in overcoming the plastic waste challenge our society is facing today. An ideal plastic detector should be able to discern different plastics at the molecular level in a standoff fashion where the detector does not come in contact with the target plastic. We have demonstrated a standoff technique for the rapid identification of plastics based on their mid-IR absorption spectra. Since mid-IR region is free of overtones, this region is known as molecular finger print regime This technique is based on a variation of photoacoustic spectroscopy (PAS), where the light from a tunable infrared source, a quantum cascade laser (QCL), is scattered/reflected off the target plastic object. The returning scattered light is collected and made to create acoustic waves on a microfabricated cantilever sensor. Our experimental results show that the cantilever response, resonance frequency, amplitude, and bending, changes with infrared absorption characteristics of the target. A plot of cantilever response as a function of illuminating wavelength mimic the infrared absorption peaks of the plastics material producing a mechanical spectrum. The generated spectrum obtained for different plastics is then compared with that conventional spectrum for polymer identification.

Activation of the Cyano Group at Imidazole via Copper Stimulated Alcoholysis

Reactions of 4,5-dicyano-1-methylimidazole with CuX2 (X = Cl, Br) in alcohol solvents (ethanol and methanol) resulted in the formation of Cu(II) carboximidate complexes [CuCl2(5- cyano-4-C(OEt)N-1-methylimidazole)(EtOH)] (1), [Cu2(µ-Cl)2Cl2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (2), [Cu2(µ-Br)2Br2(5-cyano-4-C(OMe)N-1-methylimidazole)2] (3), and [Cu2(µ-Br)2Br2(5-cyano-4-C(OEt)N-1-methylimidazole)2] (4). The structures were determined by the X-ray crystallographic method, and further spectroscopic and computational methods were employed to explain the structural features. The solvent contributed to the alcoholysis reaction of the cyano group, as the result of which the ligand coordinated to the metal center in bidentate mode forming a five-membered chelating ring. In 1, the solvent also acts as an additional ligand, which coordinates to the metal center of a monomeric complex. In compounds 2–4, two halogen ligands link the metal atoms forming dihalo-bridged copper dimers. The infrared absorption characteristics were verified by simulation of the infrared spectra at the density functional theory level. In addition, the electronic absorption characteristics were explained by simulation of the UV–Vis spectra using the TD-DFT method. Molecular modelling at the DFT level was performed to study the effects of halogen type and steric hindrance of the alkoxy groups in forming the copper(II) complexes.

Band optimization of passive methane gas leak detection based on uncooled infrared focal plane array.

Current methane gas leak detection technology uses infrared imaging in the medium wave (MW) or long wave (LW) bands, essentially applying cooled infrared detectors. In this study, a simplified three-layer radiative transfer model is adopted based on methane gas detection theory, considering background radiation, atmospheric infrared absorption, gas absorption, and emission characteristics to analyze the contrast of methane gas thermography in different infrared bands. The analysis results suggest that under certain conditions, the 6.6-8.6μm LW band provides higher contrast compared to the 3-5μm MW band. The optimal imaging wavelength band is selected according to imaging contrast advantages and disadvantages, and infrared optical systems and infrared filters are designed and optimized. We build a passive methane gas leak detection system based on uncooled infrared focal plane array detectors. By collecting gas images under different conditions, the imaging detection capabilities for methane gas leaks in the MW and LW bands in a laboratory environment are compared. Finally, the developing trends in methane gas detection technology are analyzed.

Development and integration of near atmospheric N2 ambient sputtered Au thin film for enhanced infrared absorption

The exceedingly fragile nature of thermally grown Au-black coating makes handling and patterning a critical issue. Infrared absorption characteristics of near atmospheric, N2 ambient DC sputtered Au thin films are studied for this purpose. The thin Au films are sputtered at different chamber pressures in Ar and N2/Ar gas ambient from 4.5 to 8.0mbar and optimized for enhanced infrared absorption. The absorber film sputtered in N2/Ar ambient at 8.0mbar chamber pressure offers significant absorption of medium to long wave infrared radiations. The micro-patterning of sputtered Au thin film is carried out by using conventional photolithography and metal lift off methods on a prefabricated µ-infrared detector array on Si (100) substrate. The steady state temperature response of sputtered film has been examined using nondestructive thermal imaging method under external heating of the detector array.

All-Semiconductor Plasmonic Resonator for Surface-Enhanced Infrared Absorption Spectroscopy

Infrared absorption spectroscopy remains a challenge due to the weak light-matter interaction between micron-wavelengthed infrared light and nano-sized molecules. A highly doped semiconductor supports intrinsic plasmon modes at infrared frequencies, and is compatible with the current epitaxial growth processing, which makes it promising for various applications. Here, we propose an all-semiconductor plasmonic resonator to enhance the infrared absorption of the adsorbed molecules. An optical model is employed to investigate the effect of structural parameters on the spectral features of the resonator and the enhanced infrared absorption characteristics are further discussed. When a molecular layer is deposited upon the resonator, the weak molecular absorption signal can be significantly enhanced. A high enhancement factor of 470 can be achieved once the resonance wavelength of the resonator is overlapped with the desired vibrational mode of the molecules. Our study offers a promising approach to engineering semiconductor optics devices for mid-infrared sensing applications.

基于甲烷气体红外吸收特性窄带滤波器的研究

基于甲烷气体红外吸收特性窄带滤波器的研究

PDielec: The calculation of infrared and terahertz absorption for powdered crystals.

The Python package PDielec is described, which calculates the infrared absorption characteristics of a crystalline material supported in a non‐absorbing medium. PDielec post processes solid‐state quantum mechanical and molecular mechanical calculations of the phonons and dielectric response of the crystalline material. Using an effective medium method, the package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. The theory of the approach is described, followed by a description of the implementation within PDielec. Finally, a section providing several examples of its application is given. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

Nanoforest of black silicon fabricated by AIC and RIE method

A nanoforest of black silicon was prepared using a method combining aluminum-induced crystallization (AIC) and reactive-ion etching (RIE). During the AIC period, a rough layer, incorporating AlSix intermetallics, was formed. This layer acted as an etch mask for the RIE step. X-ray photoelectron spectroscopic (XPS) measurements were performed to further analyze the formation of black silicon. Compared to Si3N4 and polysilicon, the black silicon exhibits a high degree of infrared absorption for wavelengths of about 3 to 5μm and 8 to 14μm, respectively. In addition, black platinum overlaid on the base of black silicon further improves the infrared absorption. This nanostructure forests of black silicon could be incorporated into the fabrication process for gas detectors, photovoltaic devices, and imaging applications to improve the infrared absorption characteristics.

Infrared absorption characteristics of solid nitrogen at near-triple point temperatures

The smooth, uniform, and transparent solid nitrogen-molecular film was grown by applying the slow thermal cycles near the triple-point temperature to the growth process in our home-made liquid/solid preparation apparatus. The infrared absorption spectra of solid nitrogen at near-triple point temperature are measured by the infrared spectroscopy system. A broad absorption band can be observed from 2222 to 2439 cm-1 with the strongest peak at 2288 cm-1. This has been well explained theoretically on the basis of the ground-state vibration and the coupling between the ground-state vibration and rotation at low temperatures within the framework of anharmonic approximation.

Lanthanide cation-induced tuning of surface capping properties in zinc sulfide nanoparticles: an infrared absorption study

Lanthanide cations tune the infrared absorption characteristics of the capping ligands in Zn(Ln)S [Ln = Sm, Eu, Tb, Dy] nanoparticles.

Mass transfer caused by gravitational instability at reactive solid–liquid interfaces

Mass transfer in porous media has been investigated experimentally. In this paper, we present a visualization technique and discuss the behavior of a substance which transfers under the influence of gravity and reacts with the surface of porous media. Mass transfer by the reaction with porous media was demonstrated by means of electrochemical deposition experiment on particulate beds with complex structures. A copper plate (anode) and a stainless steel particulate bed (cathode) were, respectively, placed at the upper and bottom side of a thin vertical cell which was filled with copper sulfate solution. After the application of electricity, cupric ion which is provided from the copper plate to the solution transfers under the influence of gravity and it is consumed by deposition at the particulate bed. The behavior of ions between the electrodes was visualized by utilizing the infrared absorption characteristics of cupric ion. We observed gravitational instability and convection flow due to concentration gradient of ions in opposite direction to that of gravity, which is formed by reaction at solid–liquid interfaces. While downward flow caused by Rayleigh–Taylor instability was observed in the case of flat interfaces, upward flow generated from complex-shaped interfaces was greatly dependent on their geometry. The interaction of these flows resulted in the convection throughout the cell. Consequently, it is found from the results that the gravitational instability significantly varies the transport characteristics and that the reactive interface geometry greatly affects the overall mass transfer.

Study on Infrared Absorption Characteristics of Ti and TiNx Nanofilms

Infrared detector has a wide range of applications. To fabricate an IR detector with good sensitivity, an efficient IR absorber is needed. In this paper, we theoretically and experimentally investigated the absorption characteristics of Ti, multi-layer structured Ti-SiO2 and TiNx-SiNx nano films. The multi-layer structured TiNx-SiNx films with different nitrogen contents and Ti nano films with different thicknesses were deposited by e-beam sputtering. For single nano Ti film, 35% absorptivity was obtained at a wavelength of 1.67μm when the film thickness was 15.3nm. A better IR absorption characteristic was achieved for multi-layer structured Ti-SiO2 nano film. In this structure, an absorption peak of appears at a wavelength of 9.5μm. Compared with the absorption behavior of single SiNx film, an additional nano TiNx film obviously improved IR absorption at a wider band. And a maximum IR absorptivity of 27% was obtained at the wavelength of 14μm.

Investigation of the extinction coefficient of PECVD hydrogenated amorphous silicon nitride films

In order to study the infrared absorption characteristics of hydrogenated amorphous silicon nitride (a-SiNx:H) films prepared by plasma-enhanced chemical vapor deposition (PECVD), the influence of process parameters on the extinction coefficient (EC) of a-SiNx:H films is investigated in the spectrum from 714 to 1250 cm−1. In our experiments, the EC at Si–N stretching frequency ranges from 1.32 to 2.27 and the corresponding peak wave number shifts from 828 to 890 cm−1 by adjusting process parameters. The results show that the enhanced HF power and substrate temperature are the most important parameters for increasing the EC of the film, and increased NH3/SiH4 gas flow ratio is the key to the blueshift of peak wave number. Finally, the adjusted process parameters of a-SiNx:H film for application in an infrared focal plane array are selected: SiH4:NH3:N2 = 2:3:100, HF power: 45 W, LF power: 35 W, pulse time: HF/LF pulse time = 0.6, temperature: 350 and pressure: 650 mTorr.