IR Transmission Research Articles

Abnormal negative thermal quenching of photoluminescence in CdMnTe:In crystals

Temperature-dependent photoluminescence (PL) properties of indium-doped CdMnTe (CMT:In) crystals were investigated. Four emission peaks of the tip crystal and three emission peaks of the tail crystal from as-grown CMT:In ingot were observed at low-temperature (10 K) PL spectra, respectively. From 20 K to 40 K, PL intensity of the deep defect-related emission peak ( D complex ) increased with temperature, showing a negative thermal quenching effect for the tip crystal. Interestingly, from 60 K to 80 K, negative thermal quenching phenomena were found for three emission peaks, the neutral donor–bound exciton ( D 0 , X ), the donor–acceptor pair DAP and D complex , in PL spectra of the tail crystal. ICP-MS test, IR transmittance, I–V measurement and IR microscope revealed that the CMT:In crystals with many impurities and defects tended to cause abnormal photoluminescence. Specially, impurities mainly resulted in the formation of intermediate states and were responsible for the negative thermal quenching behavior. The abnormal PL behavior can be explained by intermediate states. • Temperature-dependent photoluminescence properties of indium-doped CdMnTe crystals were investigated. • Negative thermal quenching behavior existed in the range of 20~40 K and 60~80 K for tip and tail crystals, respectively. • Impurities and lattice defects related to intermediate states were responsible for the negative thermal quenching behavior.

Impact of deposition temperature on microstructure and properties of erbium oxide antireflective films deposited on CVD diamond substrates

To improve the transmittance of chemical vapor deposition (CVD) diamond, erbium(III) oxide (Er2O3) antireflective films were deposited on CVD diamond substrates by radio frequency (RF) magnetron sputtering. Effects of deposition temperature on structure, chemical composition and properties of the samples were investigated. A strong correlation was observed between the deposition temperature and crystalline structure evolution of the Er2O3 antireflective films. With rising deposition temperature, the deposition rate, grain size and surface roughness of the Er2O3 antireflective films increased. Changes of composition and chemical bonding of the films were analyzed. Results showed that the amount of bonding between Er and O atoms surface as the temperature increased. The films were structured by amorphous, monoclinic and cubic phase, with preferential orientations of C-Er2O3 {222} at deposition temperature increased to 400 °C. A thickness of 10 nm transition layer was observed between the Er2O3 antireflective films and the CVD diamond substrates by transmission electron microscopy (TEM). Moreover, the transition layer feature primarily consisted of Er, O and C. The hardness and modulus of Er2O3 antireflective films were increased for higher deposition temperature, which positively affects the IR transmittance and adhesion strength of the Er2O3 antireflective films on CVD diamond substrates.

SPECTROSCOPIC STUDY OF SALT MELTS OF THE SmF3-CeF3-NaCl-KCl SYSTEM

Redox interactions between the components of the SmF3-CeF3 and SmF3-CeF3-NaCl-KCl systems have been established by IR transmission spectroscopy, diffuse reflectance electron spectroscopy and luminescence spectroscopy. A significant decrease in the transparency in the IR range of the spectrum was found when passing from the first of the systems to the second, which is explained by an increase in scattering by ultramicrodispersed particles of fluorides in the salt melt. In both systems, the formation of a significant amount of Sm (II) and a decrease in the content of Sm (III) are observed. The change in the valence state of Samarium both during solid-phase heat treatment (1100 °C) and during holding in a salt melt at 700 °C is manifested in the disappearance of some absorption bands, the appearance of new bands, and a gypsochromic shift of the remaining bands. The luminescence spectra exhibit high-intensity emission bands in the 640–740 nm range, which correspond to 5d‑4f electronic transitions in Sm2+ ions. At the same time, the highest intensity is observed in the band corresponding to intracenter 5d‑4f electronic transitions in Ce3+ ions. Apparently, the Ce(IV) compound, formed as a result of the exchange reaction of complex fluoride with a salt melt, volatilizes with subsequent decomposition and does not affect the character of luminescence. On the whole, the luminescence intensity after treatment in the molten salt increases by several tens of times, which indicates a significant change in the radiation mechanism. The mechanism of redox reactions in the solid-phase state, as well as exchange processes in the salt melt and after its crystallization, is discussed. A significant role of solvation shells around particles of lanthanide fluorides in luminescence processes is assumed.

Correlation between Te inclusions and the opto-electrical properties of CdMnTe and CdMgTe single crystals

In this paper, the effects of Te inclusions on the optical and electrical properties of CdMnTe and CdMgTe crystals grown by the modified vertical Bridgman method were investigated. For CdMnTe ingot, the average size and density distribution of Te inclusions along axial direction were in the range of 12 ~ 29 μm and 1.53 × 104 cm−2 ~ 2.81 × 105 cm−2, respectively. For CdMgTe ingot, the average size and density distribution of Te inclusions were in the range of 6 ~ 20 μm and 8.17 × 103 cm−2 ~ 2.42 × 104 cm−2, respectively. The density and size of Te inclusions increased gradually from the first-to-freeze part to the last-to-freeze part for CdMnTe ingot, while that of CdMgTe ingot first decreased and then increased. For both CdMnTe and CdMgTe ingots, the resistivity, IR transmittance and FWHM of (D0, X) peak first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The middle-to-freeze parts of both ingots had the best crystal quality. For both CdMnTe and CdMgTe detectors, the energy resolution and (μτ)e value were first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The detectors fabricated by the middle-to-freeze parts of both crystals had the best performance and can could meet the requirements of room temperature radiation detection.PACS: 78.30.Fs; 78.55.Et; 81.40.Ef.

The Investigation on Mid-Far Infrared Nonlinear Crystal AgGaGe5Se12 (AGGSe)

3–5, 8–14 μm mid-far infrared (MF-IR) coherent lights generated by nonlinear optical (NLO) crystals are crucial for many industrial and military applications. AgGaGe5Se12 (AGGSe) is a promising NLO candidate because of its good optical performance. In this paper, the large AGGSe single crystal of 35 mm diameter and 80 mm length was obtained by the seed-aided Bridgman method. The crystalline quality was characterized with X-ray diffraction, rocking curve, transmission spectrum. The FWHM of the (210) peak was about 0.05° and the IR transmission was about 60% (1–10 μm, 6 mm thick). Additionally, it performed well in 8 μm frequency doubling, with a maximum output power of about 41 mW, corresponding to an optical-to-optical conversion efficiency of 3.2%. The laser induced damage threshold (LIDT) value was about 200 MW/cm2 (1.06 μm, 20 ns, 1 Hz).

Fatty Acid Prediction in Bovine Milk by Attenuated Total Reflection Infrared Spectroscopy after Solvent-Free Lipid Separation.

In the present study, a novel approach for mid-infrared (IR)-based prediction of bovine milk fatty acid composition is introduced. A rapid, solvent-free, two-step centrifugation method was applied in order to obtain representative milk fat fractions. IR spectra of pure milk lipids were recorded with attenuated total reflection Fourier-transform infrared (ATR-FT-IR) spectroscopy. Comparison to the IR transmission spectra of whole milk revealed a higher amount of significant spectral information for fatty acid analysis. Partial least squares (PLS) regression models were calculated to relate the IR spectra to gas chromatography/mass spectrometry (GC/MS) reference values, providing particularly good predictions for fatty acid sum parameters as well as for the following individual fatty acids: C10:0 (R2P = 0.99), C12:0 (R2P = 0.97), C14:0 (R2P = 0.88), C16:0 (R2P = 0.81), C18:0 (R2P = 0.93), and C18:1cis (R2P = 0.95). The IR wavenumber ranges for the individual regression models were optimized and validated by calculation of the PLS selectivity ratio. Based on a set of 45 milk samples, the obtained PLS figures of merit are significantly better than those reported in literature using whole milk transmission spectra and larger datasets. In this context, direct IR measurement of the milk fat fraction inherently eliminates covariation structures between fatty acids and total fat content, which poses a common problem in IR-based milk fat profiling. The combination of solvent-free lipid separation and ATR-FT-IR spectroscopy represents a novel approach for fast fatty acid prediction, with the potential for high-throughput application in routine lab operation.

18‐2: Invited Paper: LCD Enhancement Films Enabling High‐Performance Near‐IR Transparent LCDs

The conventional light management films used to enhance display performance of a conventional edge‐lit LCD reflect, scatter, and refract both visible and near infrared light and therefore do not allow imaging though LCDs. We have developed an entirely new class of display enhancement films and coatings that enable imaging through LCDs in near IR wavelengths while maintaining high display quality. Using this Near IR Transmission System (NITS) we demonstrate under display fingerprint sensing for LCD‐based smart phones.

A LabVIEW based virtual instrument system for mid infrared laser spectroscopy measurements

The development of a virtual instrument (VI) interface to acquire spectroscopic measurements using a quantum cascade laser-based on LabVIEWTM is presented. The interface can enable mid-infrared laser spectroscopic data acquisition using a fast response mercury-cadmium-telluride (MCT) detector. The MCT is connected to an analog/digital converter card, and the data is displayed in a virtual high-speed oscilloscope. The VI processes the acquired data, displays the information, and saves it to a file through several operations using a “state machine” architecture. Transmission measurements of a polystyrene film were used to calibrate the system. They were compared to the National Institute of Standards and Technology-based FT-IR reference spectrum, showing excellent agreement. The system was tested with four different optical setups for IR Transmission, Diffuse Reflectance Infrared Spectroscopy, Reflection Absorption Infrared Spectroscopy, and Attenuated Total Reflection. The VI can be easily customized, allowing users to adapt it according to their specific laboratory needs.

Silica-Supported PdGa Nanoparticles: Metal Synergy for Highly Active and Selective CO2-to-CH3OH Hydrogenation.

The direct conversion of CO2 to CH3OH represents an appealing strategy for the mitigation of anthropogenic CO2 emissions. Here, we report that small, narrowly distributed alloyed PdGa nanoparticles, prepared via surface organometallic chemistry from silica-supported GaIII isolated sites, selectively catalyze the hydrogenation of CO2 to CH3OH. At 230 °C and 25 bar, high activity (22.3 molMeOH molPd–1 h–1) and selectivity for CH3OH/DME (81%) are observed, while the corresponding silica-supported Pd nanoparticles show low activity and selectivity. X-ray absorption spectroscopy (XAS), IR, NMR, and scanning transmission electron microscopy–energy-dispersive X-ray provide evidence for alloying in the as-synthesized material. In situ XAS reveals that there is a dynamic dealloying/realloying process, through Ga redox, while operando diffuse reflectance infrared Fourier transform spectroscopy demonstrates that, while both methoxy and formate species are observed in reaction conditions, the relative concentrations are inversely proportional, as the chemical potential of the gas phase is modulated. High CH3OH selectivities, across a broad range of conversions, are observed, showing that CO formation is suppressed for this catalyst, in contrast to reported Pd catalysts.

A flexible film to block solar radiation for daytime radiative cooling

Passive radiative cooling without external energy input or environmental pollution is promising to be a serviceable strategy for energy saving. However, intense solar radiation seriously limits the performance of daytime radiative cooling. Here, a flexible and practical approach to reducing solar absorption of the emitters with a spectrally selective film (SSF) was proposed. The solar reflectivity of the SSF is 93%, while the IR transmissivity in the atmospheric window is 87%. Particularly, the SSF is hydrophobic, providing the film with resistance to the potential condensation problems. By covering with the SSF, black emitters achieved a consecutive 24-h sub-ambient radiative cooling. The temperature of the emitter surface decreased by 21.4 °C comparing to the bare ones at noon, with an average temperature drop of 3.1 °C below the ambient temperature. And higher average sub-ambient temperature drop of 4.8 °C was achieved by the improved experiment with convection shield. Additionally, the cooling performance for SSF with various emitters was also discussed. Commercial ESR film can achieve a cooling power of ~100 W/m2 with the SSF in arid areas. And the national-scale modeling in China showed that 85% of China's areas can achieve daytime sub-ambient radiative cooling by integrating with the proposed film. Thus, the scalable SSF can relax the requirements of solar reflection for emitters, providing a viable solution for daytime radiative cooling with simpler and cheaper emitters.

Thermal performance improvement for the ceiling radiant cooling panel with an inbuilt air gap by the convection shield

Thermal resistances of the ceiling radiant cooling panels with an inbuilt air gap (AGP) are large, which are mainly contributed by the air gap and the radiation shield. Replacing the radiation shield (metal plate) with the convection shield (IR semi-transparent film), thermal resistances can be reduced. In this study, thermal resistances of previous AGPs are analyzed using the experimental data from published literature, and validated lumped parameter thermal models are used to compare thermal performance of the previous and improved AGPs. The results show that the improved AGP with 6 mm air gap can provide 124.2 W/m2 cooling capacity when the cold surface temperature is 7 ℃. Under the same steady-state condition, cooling capacities are increased by 48.1% and 18.5% when compared with the previous AGPs with 6 mm air gap and 1 mm air gap, respectively. Meanwhile, the temperature of the IR semi-transparent film is 1.18 ℃ higher than the dew point temperature. The improved AGP has a better synergy in improving cooling capacity and anti-condensation ability. It is recommended that future research pay more attention to the convection shield with high IR transmissivity and excellent mechanical properties rather than the air gap.

Metastable growth and infrared spectra of CuB2O4:Ni single crystals

The formation of CuB2O4:Ni crystals in fluxes based on Li2WO4–Bi2O3–WO3 has been studied. A distinctive feature of the used flux growing mode is the metastable nature of nucleation. IR reflection and transmission spectra are presented.

Influence of magnetic nanoparticles on cells of Ehrlich ascites carcinoma

The effect of magnetic nanoparticles coated with arabinogalactan on the viability of Ehrlich ascites carcinoma (EAC) cells was studied. The nanoparticles were studied by transmission electron microscopy, Mössbauer spectroscopy, IR spectroscopy, and ferromagnetic resonance. A correlation between the proportion of dead EAC cells in suspension and the intensity of the EPR signal of dinitrosyl iron complexes was found. This result may be due to the presence of NO molecules.

Characterization of Philippine natural bentonite

Abstract Philippine natural bentonite is characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM), chemical analysis, thermogravimetric-differential scanning calorimetry (TG-DSC), and Fourier transform infrared (FTIR) analysis. The cation exchange capacity (CEC) was also measured. XRD shows that the mineral is composed primarily of mordenite, hectorite, and montmorillonite. SEM shows the flaky and porous structure of the bentonite powder. Chemical analyses show that SiO2 (47.90 wt%) and Al2O3 (14.02 wt%) are the major components of the clay. TG-DSC shows that the mineral contains 15.55% moisture. IR transmittance spectrum shows the common vibration bands present in the sample which include O–H stretching of inter-porous water, symmetric and asymmetric stretching of hydroxyl functional groups, asymmetrical stretching of internal tetrahedra (O–Si–O and O–Al–O), symmetrical stretching of external linkages, and so on. The measured CEC were found to be 91.37 and 43.01 meq/100 g according to the ammonium acetate method and barium acetate method, respectively.

IR Based Auto-Recharging System for Autonomous Mobile Robot

As autonomous mobile robots are progressively utilized for appropriated missions, a significant issue that should be tackled is the autonomous recharging problem. The robots can be recharged by planning and arranging effectively to maximize its working efficiency. This paper presents the implementation of automatic docking robot with docking strategy and recharging capabilities. The robot is programmed using an algorithm which will guide the robot to move around in a square path of 30 inch by 30 inch continuously. While the robot is performing its assigned task, the battery remaining voltage is monitored by voltage detection module. When the battery voltage reaches threshold value of less than 12V, the microcontroller commands the robot to go back to the docking station for recharging autonomously. This system uses IR receiver sensor in front of the robot and IR transmitter sensor near docking station. The active IR transmitter sensor which transmit infrared signal located near docking area serves as landmark in guiding robot towards docking area. The robot scans the transmitted IR signal from the sensor transmitter only when it needs to charge its battery, if detected it will take the path of charging station. Once the robot approaches the charging station with the required orientation, it connects to the supply terminals for charging. The data related to battery charging voltage is transmitted by microcontroller through Bluetooth HC-05 to PLX DAQ software tool in PC stores it in the Excel sheet as the data arrive. Once the battery is fully charged the robot moves back to continue its original task.

Synthesis and Investigation of Magnesium–Aluminum Nanopowders and Ceramics Activated by Copper

Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt %), and cuprite (2 wt %) have been obtained by laser evaporation of a solid target, which is a mechanical mixture of simple oxides (MgO, Al2O3, CuO). These nanopowders have been used to prepare test samples of transparent Cu:MgAl2O4 ceramics, the IR transmission spectra of which revealed two new strong absorption bands at λ1 ≈ 1.55 (1.45) μm and λ2 ≈ 3.45 (3.03) μm, corresponding to transitions between the Stark levels 2E( $${\text{t}}_{2}^{6}$$ e3) and 2T2 ( $${\text{t}}_{2}^{5}$$ e4) of Cu2+ ions in octahedral and tetrahedral positions, respectively.

Aqueous Polymer Modification of Cellulose Nanofibrils by Grafting-Through a Reactive Methacrylate Group.

Modifying the surface of cellulose nanofibrils (CNFs) produced by mechanical refinement with a variety of polymer functional groups in an entirely water-based system is challenging because only surface hydroxyl groups are accessible. To address this limitation, an entirely water-based, polymer modification scheme is developed. CNFs are functionalized with a reactive methacrylate functional group followed by subsequent grafting-through polymerization. This modification worked with a variety of water-soluble and water-insoluble (meth)acrylates and (meth)acrylamides, grafting up to 45wt% polymer on to the CNFs. The reaction conditions introducing the methacrylate functional group are adjusted to vary the degree of functionality. Soxhlet extraction of modified samples demonstrates that the reactive methacrylate group is necessary to facilitate polymer grafting. The degree of functionalization of the polymers is studied via quantitative transmission IR spectroscopy and the morphology of the resulting cellulose nanofibrils is studied via a combination of optical, scanning electron, and atomic force microscopy. High levels of polymer modification do not significantly affect the micrometer-scale fibril morphology.

SPECTROSCOPIC PROPERTIES OF SOLIDIFIED MELTS OF THE EuF3-CeF3-NaCl-KCl SYSTEM

The nature of the interaction in the EuF3-CeF3 system in the process of high-temperature (1050 °C) oxidation - reduction reaction was established by the methods of IR transmission spectroscopy, diffuse reflection spectroscopy and fluorescence spectroscopy. Here is a significant bathochromic shift to 480-485 nm band of blue luminescence of Eu(II) - containing phases, due to the 5d–4f electronic transitions, as well as the manifestation of orange-red luminescence of Eu(III) - containing phases due to 4f–4f electronic transitions in the range of 590–690 nm. There is a bathochromic shift of the IR bandwidth in the spectrum of the solidified salt melt as a result of dissolution of the fluoride system. Diffuse reflection spectra reveal changes in the composition of the phases that dissolve in the salt melt due to exchange reactions. The wide absorption band in the UV range gives way to a negative absorption band consisting of two peaks due to luminescence. The almost complete disappearance of the band of 4f–4f transitions in Eu(III) in the near-IR range of the spectrum is evidence of its entire reduction in the chloride melt to Eu(II). The character of the luminescence spectra of solidified salt melts also changes in comparison with the initial sample of the EuF3-CeF3 system, namely, the luminescence band of Ce3+ ions disappears, and the luminescence band of Eu2+ ions at 430–440 nm becomes narrow and highly intensive. The luminescence band of Eu3+ ions in the orange-red region of the spectrum disappears completely. Thus, Eu2+ ions become dominant in the formation of the spectral picture of the solidified salt melt, which is evidence of the completion of the redox process in the system.

Origin of ultra-wide IR transmission and ultra-large birefringence of mercurous halide series with one dimensional chain-like structure: An ab initio study

Mercurous halide single crystals with one-dimensional chain-like structure exhibit great potential as polarizers or acousto-optic devices in infrared range based on the ultra-large birefringence and ultra-wide infrared transmission range. However, the origin of these two unique properties of mercurous halide families are unclear. Herein, we theoretically investigate the electronic and vibrational properties of these analogues through first principle calculation to explore the origin of these two distinct properties. The short cut-on wavelength is due to the large bandgap stemming from the ability of halogen to bind valence electrons tightly, while the long wavelength infrared cut-off originates from low phonon frequency caused by the high atomic weight of Hg and halogen atoms. Attributed to the high covalent characteristic between Hg and halogen atoms along c orientation and the very weak van der Waals force between X-Hg-Hg-X (X = Cl, Br, I) molecules perpendicular to c orientation, mercurous halide crystals exhibit large anisotropy of polarization leading to the large birefringence. Our analysis reveals that both one-dimensional chain structure and high atomic number elements contribute to the large birefringence and wide infrared transparent range, which would inspire a direction for designing new high-performance infrared polarizing materials.

IR Imaging of Solid Lubricant Coatings on Concealed/Disjointed Surfaces for Transparent Polymer Delivery Device Applications.

Transparent polymer delivery devices often contain a solid lubricant coating on a stronger bulk polymer. The distribution of lubricant coating must be monitored for device optimisation appraisals and to ensure consistency during mass production. However, coating evaluation is difficult to perform as surfaces are often concealed and/or disjointed. Dye stain analysis, which is destructive and time-consuming, is the current industry standard. We present a prototype IR transmission microscope to evaluate micron-level coating coverage of polyurethane and/or polyvinylpyrrolidone on a poly(propylene)-based delivery device. The device has a common industrial configuration, containing a duct and bevel. Inferred absorption of the coating was used to identify coating coverage and a multivariate analysis was used to remove the effects of absorption and scattering by the bulk. Coverage on concealed and disjointed surfaces was imaged and evaluated from a single camera viewpoint and ≈50 m defects were detectable. The industrial applicability of the prototype was demonstrated using comparisons with dye stain analysis by estimating water dilution of coating and identifying artifacts in coating, which may indicate machine malfunction. The sensitivity and speed of the IR technique makes it a favourable alternative to the current industry standard.