IR Emitter Research Articles

Phenyl- and Pyrazolyl-Functionalized Pyrimidine: Versatile Chromophore of Bis-Tridentate Ir(III) Phosphors for Organic Light-Emitting Diodes

There is growing interest in the bis-tridentate Ir(III) emitters as they are expected to display both improved emission efficiency and improved photostability. Herein, we turned to the new emitters m2h-1–3 and m6h-1–3, bearing a pincer carbene ancillary and a chromophoric chelate derived from judiciously selected phenyl-pyrimidine-pyrazole entities (pzm2hF)H2 and (pzm6hF)H2, which differ in terms of the location of phenyl and pyrazole substituents on the central pyrimidine. Density functional theory calculations revealed a notable change in the spin density distribution from the pyrimidine-pyrazolate entity in m2h to the pyrimidine-phenyl fragment in m6h. As a consequence, the m6h emitters exhibited both shortened emission lifetimes and improved stabilities during extensive photolysis in solution, while corresponding organic light-emitting diodes (OLEDs) doped with green-emitting m6h-1 and sky-blue-emitting m6h-2 and m6h-3 exhibited external quantum efficiencies of 17.6, 15.9, and 17.6%, respectively, sup...

CN-carbazole modified diphenylsilane-type high triplet energy hosts for blue phosphorescent organic light-emitting diodes

Abstract Diphenylsilane-derived high triplet energy host materials were developed by coupling diphenylsilane with CN-modified carbazoles. Two host materials with two CN-modified carbazoles or one CN-modified carbazole were synthesized, and their photophysical and device behavior were investigated. The host materials delivered a high triplet energy over 3.00 eV, a high glass transition temperature over 130 °C, ambipolar charge transport, and high external quantum efficiency over 20% as hosts of deep blue-emitting Ir emitters.

Unstrained PbSe/CdSe core shell nanostructures for broad band absorber and narrow band IR emitters

The purpose of this work is to establish structural, morphological and optical properties of PbSe quantum dots (QDs) and PbSe/CdSe core/shell nanostructures (C/S NSs) for application as broad band absorber and narrow band emitters. These NSs were synthesized using chemical bath deposition technique. The structural properties were studied using X-ray diffraction technique with Rietveld refinement and transmission electron microscopy (TEM). The surface morphology of synthesized thin film was established using atomic force microscopy (AFM) and scanning electron microscope (SEM). The optical properties were explained using UV–Vis absorption and photoluminescence (PL) spectroscopy with electron–hole recombination process. A comparison of estimated crystallite size from XRD, high resolution AFM and TEM images was resulted in good agreement as ~ 6.2 ± 0.5 and ~ 6.5 ± 0.5 nm for PbSe QDs and PbSe/CdSe C/S NSs respectively.These obtained properties of self-assembled PbSe/CdSe C/S NSs are expected to be useful in the development of broad band absorber and narrowband IR emitters and solar cells.

Molecular Design of Blue Phosphorescent Host Materials for Phenylimidazole‐Type Blue Triplet Emitters to Extend Operational Lifetime

AbstractHerein, a molecular design to improve the quantum efficiency and lifetime of blue phosphorescent devices by managing the lowest unoccupied molecular orbital is developed. This is accomplished by introducing a strong electron‐withdrawing cyano (CN) moiety into the chemical structure, which is made up of carbazolylcarbazole and dibenzothiophene. The CN moiety is selectively introduced into the dibenzothiophene unit or carbazolylcarbazole unit to investigate the effect of the CN position on the device performance of blue phosphorescent organic light‐emitting diodes (OLEDs). It is demonstrated that substituting CN into dibenzothiophene effectively facilitates electron injection and enhances the quantum efficiency of the blue OLEDs. A high external quantum efficiency of 26.8% is achieved in the blue phosphorescent devices using an imidazole ligand‐derived Ir emitter based on the molecular design to modify dibenzothiophene with the CN moiety. This also extends the lifetime of the blue phosphorescent device doped with the CN‐modified, imidazole ligand‐derived Ir emitter.

Synthesis and spectral properties of non-symmetrical red and near IR emitter dibenzoBODIPYs

New symmetrical and non-symmetrical benzoBODIPYs have been synthesized from diketones. For the two series the 3 and 5 positions have been substituted by different aromatic rings and onto benzo sub-units different groups have been introduced. The methodology of diketones self-condensation provides symmetrical dyes. By cross-condensation reaction, these positions can be differentiated and specific functions connected to the desired positions. These molecules have been fully characterized and their optical properties analyzed by both experimental and theoretical means. They are red to NIR emitters with a range of emission from 679 to 780 nm in CH2Cl2. They show maxima of absorption between 651 nm and 732 nm, strong ε of around 100,000 M−1 cm−1 and quite good quantum yields from 16% to 75%. The thienyl moiety on α-positions of the nitrogens generates the highest red shifts. Meanwhile dimethylamino groups in the same positions bring, besides chemical properties, proton sensitive dyes. The bromine atom onto the dibenzo sub-units exhibits good reactivity through Sonogashira coupling reactions. This approach provides multifunctional red to NIR dyes with endless possibilities of combination of chemical properties.

An Evaluation of Graphene as a Multi-Functional Heating Element for Biomedical Applications.

Graphene has been found to be an excellent heat-conductor due to the high speed of acoustic phonons in its lattice. In this work, we examine in depth a commercial graphene-based waist protector which uses graphene as a heating element. By employing thermal imaging in tandem with Raman microscopy, the thermal characteristics and performance of this device is fully assessed. It will be shown that no pronounced variation in its function is observed up to 3 hours of continuous operation and that the device seems to work effectively as an IR emitter at low power consumption. Temperature fluctuations, associated with a decrease of its electrical resistance are observed after 12 hours uptime and a temperature difference of 15 °C was recorded after 5 days of uninterrupted operation. These effects are thought to be due to the loss of graphene/polymer adhesion resulting from thermal fatigue. Overall, it is demonstrated that graphene can indeed be incorporated as an effective and operational thermal heating system in similar biomedical devices.

Blue-emitting bis-tridentate Ir(iii) phosphors: OLED performances vs. substituent effects

Dependence of external quantum efficiency (EQE) and radiative decay lifetime of blue-emitting OLED is established with photostable, bis-tridentate Ir(iii) emitters, giving max. EQE and luminescence of 12.2% and 18 980 cd m−2, and with CIEx,y coordinates between (0.16, 0.22) and (0.17, 0.27).

A panchromatic, near infrared Ir(III) emitter bearing a tripodal C^N^C ligand as a dye for dye-sensitized solar cells

The synthesis of a new complex of the form [Ir(C^N^C)(N^N)Cl] [where C^N^C = 2-(bis(4-(tert-butyl)phenyl)methyl)pyridinato (dtBubnpy, L1) and N^N is diethyl [2,2′-bipyridine-4,4′-dicarboxylate (deeb)] is reported. The crystal structure reveals an unusual tripodal tridentate C^N^C ligand forming three six-membered rings around the iridium center. The photophysical and electrochemical properties suggest the use of this complex as a dye in dye-sensitized solar cells. Time-Dependent Density Functional Theory (TD-DFT) calculations have been used to reveal the nature of the excited-states.

Implementation of Mobile Robot’s Navigation using SLAM based on Cloud Computing

This paper is concerned with the implementation of EKF-SLAM (Extended Kalman Filter- Simultaneous Localization and Mapping) algorithm using a cloud computing architecture based on ROS (Robot Operating System). The localization and mapping is essential step to navigate a mobile robot in unknown environment. The implemented EKF-SLAM has used a landmark that sensed using IR Emitter sensor provided by the Kinect camera to update a map of the environment and simultaneously estimate the robot’s position and orientation within the map. The implementation was done using three parts. The first one was the TurleBot Mobile robot with the Kinect camera, which was simulated in Gazebo environment. The second part was the EKF-SLAM running under the MATLAB to generate the Map and Location data. The third part was the ROS Master node, which runs on the cloud to enable part one and two to communicate using topics. The scan data from Kinect camera and the location data from the odometer is transferred from the first part to the second part through ROS Master node after impaired with zero mean Gaussian noise . Then the second part performs EKF-SLAM and transmit the corrections to the first part through the ROS Master node as well.

The Infrared Spectra of Customized Magnesium/Teflon/Viton (MTV) Decoy Flares to Thermal Signature of Jet Engine

Decoy flares are customized materials, which are capable of yielding thermal signature to interfere with IR guided missile seekers. In this study, different decoy flares compositions based on Magnesium/Teflon/Viton (MTV) (with fuel percentage ranging from 40:70 wt %) were developed by granulation and subsequent pressing. The spectral performance of developed decoy flare formulations was measured to thermal signature of jet engine nozzle using (FT-MIR 2-6) spectrophotometer. The jet engine thermal signature was characterized with two characteristic peaks over α band (2-3μm) and β band (3-5μm); this signature was correlated to black body emission by the nozzle at 690 0C. Absorption of the IR emission by air could attenuate the signal over the band 3-4 μm due to CO2 and H2O IR absorption. The characteristic intensity ratio of jet engine nozzle (α/ β) = 0.26 . The developed decoy flares offered similar thermal signature but with higher intensity due to the formation carbon soot and MgF2 as black body and active IR emitter respectively. Quantification of these emitting species in the combustion flame was performed using the ICT thermodynamic code. MTV decoy flare with 65 wt % Mg offered an increase in the intensity of α band and β by 21 and 4 times respectively. This customized formulation offered the formation of MgF2 (molecular emitter) and C soot (grey emitter) at 42.4, and 8.8 wt % respectively. It is also offered 48 wt % Mg fuel which would be oxidized in the flame and add much more heat with the formation of MgO (grey body). The characteristic intensity ratio Ɵ was found to be 0.96. This is manuscript would open the route for the development of customized decoy flares with tailored spectral performance.

Degradation mechanism study and electron scattering device structure for long lifetime in blue phosphorescent organic light-emitting diodes

Degradation of Ir based blue phosphorescent emitters was analyzed from the viewpoint of triplet-polaron annihilation (TPA) of the emitters. Two different classes of Ir emitters, F substituted phenylpyridine type Ir emitter and F substituted phenylimidazole type Ir emitter, were compared as the blue emitters. Aging test of singlet carrier devices of the Ir emitters under polaron, exciton, and exciton-polaron revealed that the phenylimidazole type Ir emitter was relatively more resistant to the TPA degradation than the phenylpyridine type Ir emitter and extended the lifetime of blue phosphorescent organic light-emitting diodes. In addition, the lifetime and degradation of the short-living blue phosphorescent devices were improved by the host material suppressing the TPA under negative polaron using an electron scattering emitting layer structure.

Evaluation of a newly developed mid-infrared sensor for real-time monitoring of yeast fermentations

A mid-infrared (MIR) sensor using the attenuated total reflection (ATR) technique has been developed for real-time monitoring in biotechnology. The MIR-ATR sensor consists of an IR emitter as light source, a zinc selenide ATR prism as boundary to the process, and four thermopile detectors, each equipped with an optical bandpass filter. The suitability of the sensor for practical application was tested during aerobic batch-fermentations of Saccharomyces cerevisiae by simultaneous monitoring of glucose and ethanol. The performance of the sensor was compared to a commercial Fourier transform mid-infrared (FT-MIR) spectrometer by on-line measurements in a bypass loop. Sensor and spectrometer were calibrated by multiple linear regression (MLR) in order to link the measured absorbance in the transmission ranges of the four optical sensor channels to the analyte concentrations. For reference analysis, high-performance liquid chromatography (HPLC) was applied. Process monitoring using the sensor yielded in standard errors of prediction (SEP) of 6.15g/L and 1.36g/L for glucose and ethanol. In the case of the FT-MIR spectrometer the corresponding SEP values were 4.34g/L and 0.61g/L, respectively. The advantages of optical multi-channel mid-infrared sensors in comparison to FT-MIR spectrometer setups are the compactness, easy process implementation and lower price.

Simple design to achieve red-to-near-infrared emissive cationic Ir(iii) emitters and their use in light emitting electrochemical cells

Two cationic Ir(iii) complexes bearing bithiazole-type ancillary ligands have been synthesised and tested as deep red-to-near-infrared emitters in solution-processed electroluminescent devices.

Wheat germ stabilization by infrared radiation.

Wheat germ has an important enzymatic activity, being lipases the enzymes which cause the highest impact in the reduction of shelf life. The objective of this study was to evaluate the effects of infrared radiation on wheat germ stabilization in an attempt to extend the shelf life. The effects of treatment time, gap (sample distance to IR emitters) and infrared radiation intensity on wheat germ were analyzed through response surface methodology. Final moisture content, final temperature, color of germ and germ oil quality parameters: free fatty acid content changes and total tocopherol content were the responses evaluated using a Box-Behnken design. A combination of an infrared radiation intensity of 4800W/m2, a 3min treatment and 0.2m emitter-sample distance were the best processing condition to stabilize the wheat germ without significantly reduction of the tocopherol content. A confirmatory experiment was conducted with these optimal conditions, and the heat-treated and raw germ samples were stored for 90days at room temperature in three layer packages to protect them against light and oxygen. The oil quality parameters indicated that the raw germ had a shelf-life of about 15days, with the heat-treated wheat germ maintaining its quality for at least 90days under these stored conditions.

Simultaneous rough rice drying and rice bran stabilization using infrared radiation heating

The objective of this study was to develop a new rice drying method using IR heating followed by tempering. Freshly harvested medium grain rice (M206) samples with different initial moisture contents (IMCs) were used in this study. The samples were dried for one- and two-passes using a catalytic IR emitter to reach rice surface temperature of 60 °C. After IR heating, the samples were tempered in an incubator at 60 °C for different durations ranging from 1 to 5 h. The effects of new drying method on moisture removal, milling quality, and shelf life of rice bran were evaluated. High heating and drying rates and good milling quality of rough rice were achieved. It took only 55 s to heat the rice samples to 60 °C. For one-pass drying and 4 h tempering treatment, the total moisture removals were 3.33, 3.78 and 5.89 g moisture/100 g dry solid for samples with initial moisture contents of 20.06, 25.53 and 32.50 g moisture/100 g dry solid, respectively. IR heating did not generate adverse effects on milling quality of rough rice. Importantly, the storage stability of rice bran from the new drying method was extended to 38 days compared 7 days from current drying practice.

An IR emitter patterned at the nanoscale

An IR emitter patterned at the nanoscale

Performance assessment of thermophotovoltaic application in steel industry

The potential for using Thermophotovoltaic (TPV) generators as an alternative for recovering energy losses in steel production industry is assessed. A mathematical model for the assessment of the performance of TPV application in the iron and steel industry has been developed. In order to support the mathematical model, a sample TPV apparatus in laboratory scale based on an IR emitter has been designed and assembled. The key modeling parameters of TPV generator include: the open circuit voltage, the short circuit current density and fill factor of the TPV cell. These parameters have been considered in the model as functions of several variables such as: the emitter (hot steel slab) temperature, the cell temperature, the distance between the cells and emitter, the spectral response and the cell energy gap. The External Quantum Efficiency (EQE) as an important indicator of the cell׳s spectral response is included in the model. Moreover, the variation of the emitter temperature has been considered. Several tests have been carried out for different values of the cell-emitter gap. It has been found that when the GaSb cells are used for energy recovery, a minimum temperature of 873°C is required. The upper limit of the emitter temperature is usually determined in steel production process associated with hot rolling process which has a temperature around 1250°C. Finally, the total efficiency of the system was obtained to 4.12%, when GaSb cell with temperature of 27°C and slab emitters with temperature of 1257°C are used. The results of the simulation of the model in a casting process at the Mobarakeh Steel Complex have shown a potential of energy recovery of 26.987MJ per year.

X-RAY EMISSION FROM THE TAFFY (VV254) GALAXIES AND BRIDGE

We present the first X-ray observations of the Taffy galaxies (UGC 12914/5) with the Chandra observatory, and detect soft X-ray emission in the region of the gas-rich, radio-continuum-emitting Taffy bridge. The results are compared to Herschel observations of dust and diffuse [CII] line-emitting gas. The diffuse component of the Taffy bridge has an X-ray luminosity of L(X) (0.5-8keV) =5.4 x 10^39 erg s^-1, which accounts for 19% of the luminosity of the sum for the two galaxies. The total mass in hot gas is (0.8--1.3) x 10^8 M_sun, which is approximately 1% of the total (HI~+~H2) gas mass in the bridge, and ~11% of the mass of warm molecular hydrogen discovered by Spitzer. The soft X-ray and dense CO-emitting gas in the bridge have offset distributions, with the X-rays peaking along the north-western side of the bridge in the region where stronger far-IR dust and diffuse [CII] gas is observed by Herschel. We detect nine Ultra Luminous X-ray sources (ULXs) in the system, the brightest of which is found in the bridge, associated with an extragalactic HII region. We suggest that the X-ray--emitting gas has been shocked--heated to high temperatures and "splashed" into the bridge by the collision. The large amount of gas stripped from the galaxies into the bridge and its very long gas depletion timescale (>10 Gyr) may explain why this system, unlike most major mergers, is not a powerful IR emitter.

Radiant Heating and Tempering Treatmentsfor Improving Rate of Moisture Removalduring Drying of Shelled Corn

<abstract> <b><i>Abstract. </i></b> Radiant heating holds great potential to improve the drying rate of freshly-harvested, high moisture content (MC) grain. The effectiveness of the process when combined with tempering steps for drying corn has not been elucidated. This study evaluated the effects of various process parameters during radiant heating and tempering treatment of corn to determine the percentage point of moisture removed and relative energy requirements. Freshly-harvested corn at initial moisture contents (IMCs) of 20%, 24% and 28% wet basis (w.b.) were used in the study. The corn was heated using an IR energy source equipped with catalytic IR emitters to surface temperatures of 50°C, 70°C, and 90°C. The IR treatments were performed with the corn kernels at product-to-emitter-gap (PEG) sizes of 110, 240, and 430 mm which corresponded to measured IR intensities of 10.84, 2.83 and 2.15 kW m^-2. Following the IR treatments, the samples were tempered for 2, 4, and 6 hours at 50°C, 70°C, and 90°C. The study evaluated the implications of one- and two-pass IR heating and tempering treatments. The rate of corn kernel surface temperature rise depended on the PEG size and IMC. The longest duration corresponded to the largest PEG (430 mm) size and IMC (28%), and vice versa. At a PEG size of 430 mm, IR heating durations of 110, 122, and 140 s were required to raise the surface temperature of the corn kernels at IMCs of 20%, 24%, and 28% (w.b.) and ambient conditions (26°C) to 90°C, respectively. IR heating of corn at IMC range of 20% to 28% and at PEG size of 430 mm to surface temperatures ranging from 50°C to 90°C resulted in 0.9 to 3.2 and 1.5 to 5.2 percentage point reduction in MC, for one- and two-pass treatments, respectively. The longer the tempering duration the more moisture was removed from the corn kernels. One-pass IR heating of corn kernel at IMC of 28% and PEG size of 430 mm to surface temperature of 90°C, and tempering at 50°C, 70°C, and 90°C for 6 h, resulted in 4.2, 4.7 and 5.2 percentage points and 7.2, 8.7, and 8.6 percentage points of moisture removed for one- and two-pass treatments, respectively. The significant and rapid moisture removals by the IR and tempering treatments provide for justification to optimize and scale-up the practices for corn drying.

Acridine modified dibenzothiophene derivatives as high triplet energy host materials for blue phosphorescent organic light-emitting diodes

Acridine modified dibenzothiophene derivatives were synthesized as host materials of imidazole ligand based Ir emitters for blue phosphorescent devices. The shallow energy levels of the acridine based host materials by the strong electron donating acridine moiety were well matched with the energy levels of Ir blue triplet emitter derived from imidazole. Additionally, strong electron transporting character of the acridine moiety could increase hole density in the emitting layer and balance holes and electrons. The energy level matching between the host and dopant materials and increased hole density in the emitting layer provided a very high external quantum efficiency of 27.8% in the blue phosphorescent organic light-emitting diodes.