High Performance IR Research Articles

The Tobin Coefficient: A Relevant Photodetector Performance Metric for IR Imaging

The well-known Rule07 is a simple thus efficient way to compare available technologies for IR imaging detectors in terms of dark current. The noise is then often estimated using a shot noise approximation on the dark current. Both II–VI and III–V communities use this rule of thumb as a reference for well-performing IR photodiodes. For HOT applications, a dark current close to this rule07 is considered a necessary condition but not a sufficient one to obtain a high-performance IR imager. Indeed, when limited by shot noise, rule07 describes well the noise behavior of the considered device. However, when considering low-frequency noise, it fails to describe the expected performances. In this paper, we focus on another figure-of-merit, dedicated to detector low-frequency noise rather than dark current. Systemic 1/f noise investigation in an IR detector was first reported by Tobin et al. in 1980. There is today a relative consensus on the fact that measured 1/f noise is proportional to the dark current. The ratio between the amplitude of the 1/f noise and the dark current of the same devices may therefore be used as a figure-of-merit for a given technology. This ratio (called the Tobin factor αT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}$$\\end{document}) therefore appears adequate to compare different technologies as a figure-of-merit qualifying 1/f noise properties. This dimensionless ratio can also be very useful for optimizing a particular technology or process. However, in order to be relevant, this figure-of-merit must be estimated carefully as it appears, for instance, pixel pitch-dependent. Different examples of Tobin coefficient extraction are presented in this paper. We show that, depending on the technologies, the values of the Tobin coefficient can spread over several orders of magnitude. However, only low values result in high-quality IR imagers. Today, the best results we obtained show that αT=10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}={10}^{-5}$$\\end{document} is a state-of-art value to be compared with.

High performance iridium loaded on natural halloysite nanotubes for CO-SCR reaction

Iridium nanocatalysts are ideal candidates for the selective catalytic reduction of NOx by CO (CO-SCR) in excess oxygen. Here, a high-performance Ir nanocatalyst supported on natural halloysite nanotubes (HNTs) was applied for the CO-SCR. The HNTs loaded with only 0.5 wt% Ir achieved 78 % NOx conversion at 250 °C in the presence of 5 % O2, which was the highest among catalysts with varied Ir loadings or reduction temperatures. It also possessed an excellent SO2 and H2O tolerance during longevity tests. An interesting SO2-enhanced CO-SCR long-term stability was observed, which was ascribed to the inhibitory effects of SO2 on the side reaction between CO and O2. The loading amount and the reduction temperature could modulate the size of Ir nanoparticles and the percent of Ir0, which were two key factors determining the CO-SCR activity. DRIFTS characterizations and DFT calculations coherently revealed the favorable adsorption sites of CO (top) and NO (hcp) on Ir nanoparticles. The Ir atoms served as a charge transfer bridge from the C atom of CO to the N atom of NO, leading to the enhanced breakage of N-O bonds. This work provides Ir/HNT as a promising CO-SCR material with high performance and robustness to tackle NOx pollution.

Mechanochemistry Enabled Inverse Vulcanization of Norbornadiene for Optical Polymers and Elastomeric Materials

The emergence of polymeric materials derived from elemental sulfur through inverse vulcanization has recently provoked great interest. Particularly, norbornadiene derived sulfur polymers are predicted to have high transmittance in the long-wave infrared region that can be an excellent candidate for polymeric IR optics. Moreover, owing to the unique cyclic structures of the norbornadiene moiety, it tends to form elastic material upon copolymerization with soft segments which has not been attained for elemental sulfur derived polymers. However, because of the volatility of norbornadiene (NBD) (boiling point is 89 °C), the chemicals could not bear the thermally induced inverse vulcanization process (T > 110 °C). Hence, in this work, for the first time, NBD is subjected to ball milling with elemental sulfur via solid mechanochemical induced inverse vulcanization, which successively affords poly(Sn-r-NBD) with a wide spectrum of sulfur content from 40 to 80 wt %. The synthesis is a green process that is solvent free and releases a traceless side product of H2S without heating. More importantly, the as-fabricated poly(Sn-r-NBD) displays superior transmittance (T > 40%) within the long-wave infrared region, which is obviously better than the most investigated poly(Sn-r-DIB). Furthermore, poly(Sn-r-NBD) derived polymeric material exhibits good elasticity. The present work not only demonstrates a facile and green methodology in fabricating norbornadiene derived sulfur polymers but also promotes the application of the sulfur polymer in high-performance IR optics and elastomeric materials.

Construction of Robust Iridium(III) Complex-Based Photosensitizer for Boosting Hydrogen Evolution.

Developing a photosensitizer with high efficiency and long-term stability for photocatalytic hydrogen evolution is highly desirable yet remains a challenge. Herein, a novel Ir(III) complex-based photosensitizer (Ir3) bearing coumarin and triphenylamine groups is designed. Ir3 exhibits record activity and durability among reported transition metal complexes for photocatalytic hydrogen evolution, with a TON of 198,363 and a duration of 214 h. The excellent photocatalytic performance of Ir3 can be attributed to the synergistic effect of coumarin and triphenylamine, which improves the visible light absorption, charge separation, and electron transfer capacity of photosensitizers. This is an efficient and long-lived Ir(III) photosensitizer constructed on the basis of a synergistic approach, which could provide a new insight for the development of high-performance Ir(III) photosensitizers at the molecular level.

Biologically active compounds in Scutellaria baicalensis L. callus extract: Phytochemical analysis and isolation

Plant cells and tissue cultures are sources of secondary plant metabolites. Substances produced by callus cultures can expand the raw material base in pharmacy and food production. However, isolating biologically active substances from medicinal plants is a labor- and time-consuming process. As a result, new and efficient technological processes adapted for extraction from callus cultures are in high demand, and new algorithms of isolation and purification of biologically active substances remain a relevant task.
 This research featured callus cultures of Scutellaria baicalensis. The procedures for phytochemical analysis and isolation of biologically active substances involved such physicochemical research methods as high-performance chromatography (HPLC), thin-layer chromatography (TLC), UV spectrometry, and IR spectrometry.
 The high performance liquid chromatography confirmed the presence of flavonoids represented by baicalein (5,6,7-trioxyflavone), baicalin (baicalein 7-O-glucuronide), scutellarein (5,6,7,4-tetraoxyflavone), scutellarin (7-O-glucuronide scutellarein), vagonin, and oroxylin. The spectral analyses also detected skutebaicalin. The highest total content of diterpene belonged to the samples extracted with 70% ethanol at 70°C. The content of diterpene was 0.09 mg/cm3 in terms of betulin. The biologically active substances were isolated from the callus extracts of S. baicalensis with a recovery rate of ≥ 80%. The purification scheme made it possible to obtain highly-pure individual biologically active compounds: trans-cinnamic acid, baicalin, and oroxylin A had a purity of ≥ 95%; baicalein had a purity of ≥ 97%; scutellarin and luteolin reached ≥ 96%.
 The new technological extraction method made it possible to obtain extracts from S. baicalensis callus cultures, which were tested for the component composition. The developed isolation algorithm and purification scheme yielded biologically active substances with a purification degree of ≥ 95%.

Oxychalcogenides: A Promising Class of Materials for Nonlinear Optical Crystals with Mixed-Anion Groups.

Infrared nonlinear optical (IR NLO) materials are of great significance in the development of IR laser technology. But rationally designing high-performance IR NLO materials remains a huge challenge due to the conflict between the necessary properties required for NLO materials. Notably, oxychalcogenides with mixed-anion groups have drawn extensive interest as a family of important IR NLO candidates because they integrate the property advantages of oxides and chalcogenides by chemical substitution engineering. In this review, we provide a survey of reported oxychalcogenides and aim to present the development of NLO oxychalcogenides from the perspective of rational design of their structural chemistry. Furthermore, we focus on the relationships between partial substitution and structural symmetry as well as optical properties. These provide some helpful guidance for the further exploration and design of novel oxychalcogenide materials with excellent NLO performance in the future.

LnLiSiS4 (Ln = La and Ce): Promising infrared nonlinear optical materials designed by aliovalent substitution from SrCdSiS4

Aliovalent substitution is an effective route to design new nonlinear optical (NLO) crystals. Using SrCdSiS4 as a parent compound, two new infrared NLO lanthanide thiosilicates, namely LnLiSiS4 (Ln = La and Ce), have been successfully obtained through aliovalent substitution. Interestingly, these compounds exhibit [LiSiS4]3- layers composed of vertex- and edge-shared LiS4 and SiS4 tetrahedra that significantly different from the [LnSiS4]3- layers composed of edge-shared LnS6 trigonal prisms (or LnS7 monocapped trigonal prisms) and SiS4 tetrahedra in other ALnSiS4 (A = K, Rb, Cs, Ln = lanthanide) compounds with larger sized alkali cations. LnLiSiS4 (Ln = La and Ce) also achieve balanced properties for good infrared NLO materials: largest SHG response among all known thiosilicates (2.0 and 2.1 × AgGaS2 @ 2 μm for LaLiSiS4 and CeLiSiS4 respectively) with phase matching ability, high laser induced damage threshold (14 and 9 times of AgGaS2), wide bandgap (3.71 and 2.92 eV), wide infrared transmission range (0.35–18 μm) and good thermal stability above 700 °C. This work not only enriches the structure chemistry of lanthanide thiosilicates, but also provides an efficient route to design new high performance IR NLO materials.

Transferability of Diffractive Structure in the Compression Molding of Chalcogenide Glass

This study investigates the use of Ge28Sb12Se60 chalcogenide glass for the compression molding of an infrared optical lens with a diffractive structure. Firstly, a mold core was prepared through ultra-precision grinding of tungsten carbide, and a chalcogenide glass preform was crafted through a polishing process and designed with a radius that would prevent gas isolation during the molding process. The test lens was then molded at various temperature conditions using the prepared mold core and preform. The diffractive structures of both the mold core and the resulting molded lens were analyzed using a microscope and white light interferometer. The comparison of these diffractive structures revealed that the molding temperature had an effect on the transferability of the diffractive structure during the molding of the chalcogenide glass lens. Furthermore, it was determined that, when the molding temperature was properly adjusted, the diffractive structure of the core could be fully transferred to the surface of the chalcogenide lens. Optimized chalcogenide glass-based lenses have the potential to serve as cost-effective yet high-performance IR optics.

Na2Ba[Na2Sn2S7]: Structural Tolerance Factor-guided NLO Performance Improvement.

The strong mutual coupling of and even the opposite change in the key parameters, such as the band gap (Eg) and second-order harmonic generation (SHG), leads to the extreme scarcity in high-performance IR nonlinear optical (NLO) chalcogenides. Herein, we report 8 new sulfides, Na2Ba[(AgxNa1-x)2Sn2S7] (1, x = 0; 1 series, x = 0.1-0.6; Na2Ba[(Li0.58Na0.42)2Sn2S7], 1-0.6Li); Na2Sr[Cu2Sn2S7] (2); and Na2Ba[Cu2Sn2S7] (3). We use the structural tolerance factor ( [[EQUATION]] ) to connect the chemical composition, crystal structure, and NLO properties. Guided by these correlations, a better balance between Eg and SHG is realized in 1, which exhibits a large Eg of 3.42 eV and excellent NLO properties (SHG: 1.5 × AGS; laser-induced damage threshold: 12 × AGS), representing the best performance among the known Hg- or As-free sulfides to date.

The Antiperovskite-Type Oxychalcogenides Ae3 Q[GeOQ3 ] (Ae = Ba, Sr; Q = S, Se) with Large Second Harmonic Generation Responses and Wide Band Gaps.

Oxychalcogenides capable of exhibiting excellent balance among large second-harmonic generation (SHG) response, wide band gap (Eg ), and suitable birefringence (Δn) are ideal materials class for infrared nonlinear optical (IR NLO) crystals. However, rationally designing a new high-performance oxychalcogenide IR NLO crystal still faces a huge challenge because it requires the optimal orientations of the heteroanionic groups in oxychalcogenide. Herein, a series of antiperovskite-type oxychalcogenides, Ae3 Q[GeOQ3 ] (Ae = Ba, Sr; Q = S, Se), which were synthesized by employing the antiperovskite-type Ba3 S[GeS4 ] as the structure template. Their structures feature novel three-dimensinoal frameworks constructed by distorted [QAe6 ] octahedra, which are further filled by [GeOQ3 ] tetrahedra to form antiperovskite-type structures. Based on the unique antiperovskite-type structures, the favorable alignment of the polarizable [GeOQ3 ] tetrahedra and distorted [QAe6 ] octahedra have been achieved. These contribute the ideal combination of large SHG response (0.7-1.5 times that of AgGaS2 ), wide Eg (3.52-4.10eV), and appropriate Δn (0.017-0.035) in Ae3 Q[GeOQ3 ]. Theoretical calculations and crystal structure analyses revealed that the strong SHG and wide Eg could be attributed to the polarizable [GeOQ3 ] tetrahedra and distorted [QAe6 ] octahedra. This research provides a new exemplification for the design of high-performance IR NLO materials.

Graphene nanoribbon/graphene hybrid broadband infrared photodetectors

Graphene nanoribbons (GNRs) and graphene hybrid photodetectors were demonstrated in the middle- and long-wavelength infrared (MWIR and LWIR, respectively) regions. Graphene transistors were prepared using Si substrates with an SiO2 layer and source and drain electrodes. Single-layer graphene fabricated by chemical vapor deposition was transferred onto the substrates to form a channel; the GNR was formed on this channel by solution dispersion. The formation of graphene and the GNR was confirmed by position mapping of the Raman spectra. The photoresponse was measured in the MWIR and LWIR regions, and was found to be drastically enhanced for devices with the GNR when compared with those without it. Although the devices without the GNR could not respond at temperatures higher than 15 K, those with the GNR could be operated at temperatures up to 150 K. This was attributed to photogating by the GNR layers that absorbed the MWIR and LWIR radiation, leading to a significant temperature change. These results can potentially contribute toward developing high-performance and broadband IR graphene-based photodetectors.

Antioxidant, Anti-Tumour, and Anticoagulant Activities of Polysaccharide from Calocybe indica (APK2).

The initial structural features and in vitro biological study of crude polysaccharides from Calocybe indica (CICP) extracted by hot water followed by ethanol precipitation was investigated. High-performance gel permeation chromatography, HPLC-DAD, UV, IR and NMR spectroscopy, X-ray diffraction, scanning electron microscopy, and Congo red methods were used to determine structural features. The results revealed that CICP is a hetero-polysaccharide with a molecular weight of 9.371 × 104 Da and 2.457 × 103 Da which is composed of xylose, mannose, fucose, rhamnose, arabinose, galactose, and glucose. The antioxidant activity of CICP was evaluated using radical scavenging activity (three methods), reducing ability (three methods), metal chelating activity, and lipid peroxidation inhibition activity (two methods). It was found that the antioxidant capacity is concentration-dependent and EC50 values were found to be 1.99–3.82 mg/mL (radical scavenging activities), 0.78–2.78 mg/mL (reducing ability), 4.11 mg/mL (metal chelating activity), and 0.56–4.18 mg/mL (lipid peroxidation inhibition activity). In vitro anticoagulant assay revealed that CICP could prolong activated partial thromboplastin time (APTT), thrombin time (TT), but not prothrombin time (PT). CICP exhibited antiproliferative activity on HeLa, PC3, HT29, HepG2, and Jurkat cell lines with IC50 (μg/mL) values of 148.40, 143.60,151.00, 168.30, and 156.30, respectively. The above findings suggested that CICP could be considered a natural antioxidant and cancer preventative.

Ba2F2][Ge2O3S2]: An Unprecedented Heteroanionic Infrared Nonlinear Optical Material Containing Three Typical Anions

Metal chalcogenides, oxides, and halides are the three most typical materials classes for mid-infrared nonlinear optical (mid-IR NLO) crystals that can expand the spectral ranges of solid-state lasers to the mid-IR region. However, it is difficult for each of them to satisfy all the property requirements of mid-IR NLO crystals owing to their own defects. On the contrary, combining multiple anionic units as much as possible to construct heteroanionic compounds is an effective strategy for the design of new high-performance IR NLO crystals. Although in recent research, a series of heteroanionic materials containing two types of anions (i.e., chalcogenides-halides, oxychalcogenides, and oxyhalides) have been reported, the compounds that contain all three types of anions have still been unexplored. Herein, we report the first IR NLO crystal [Ba2F2][Ge2O3S2], which contains all three typical anions (O2–, S2–, and F–) and satisfies the key property requirements as a promising IR NLO candidate, including a strong SHG response (∼1.4× AgGaS2), a large band gap (Eg = 4.45 eV), and wide IR transmission (0.24–9.0 μm). This research indicates that coupling different types of anions in one compound is a more attractive strategy to explore new IR NLO materials with excellent properties.

High Performance Ternary Organic Phototransistors with Photoresponse up to 2600 nm at Room Temperature

AbstractInfrared (IR) photodetection is important for light communications, military, agriculture, and related fields. Organic transistors are investigated as photodetectors. However, due to their large band gap, most organic transistors can only respond to ultraviolet and visible light. Here high performance IR phototransistors with ternary semiconductors of organic donor/acceptor complex and semiconducting single‐walled carbon nanotubes (SWCNTs), without deep cooling requirements are developed. Due to both the ultralow intermolecular electronic transition energy of the complex and charge transport properties of SWCNTs, the phototransistor realizes broadband photodetection with photoresponse up to 2600 nm. Moreover, it exhibits outstanding performance under 2000 nm light with photoresponsivity of 2.75 × 106 A W−1, detectivity of 3.12 × 1014 Jones, external quantum efficiency over 108%, and high Iphoto/Idark ratio of 6.8 × 105. The device exhibits decent photoresponse to IR light even under ultra‐weak light intensity of 100 nW cm−2. The response of the phototransistor to blackbody irradiation is demonstrated, which is rarely reported for organic phototransistors. Interestingly, under visible light, the device can also be employed as synaptic devices, and important basic functions are realized. This strategy provides a new guide for developing high performance IR optoelectronics based on organic transistors.

High-performance visible-near IR photodetectors based on high-quality Sn2+-sensitized PbS films

High-quality Sn2+-sensitized PbS films were deposited via a cost‐effective chemical route. The results demonstrate that the Sn2+-sensitized PbS thin films have better crystallinity and larger grain size. Photoelectric performance of Sn2+-sensitized PbS films has been improved greatly in the visible and near-infrared range. With Sn2+ sensibilization, photoresponsivity is more than 9 times higher, and detectivity is as high as ~1010 cm2 Hz1/2 W−1. Notably, the response speed of the Sn2+-sensitized PbS films reaches a magnitude of microseconds, which is over 105 times improvements compared with the pure PbS film devices. Additionally, high-frequency switching behavior at 4 kHz shows excellent stability. Based on the feasible method and excellent photoelectric performance of the devices, it has been demonstrated that Sn2+ sensibilization is of viability to improve the detection performance of commercial photodetectors.

Stable and high-performance Ir electrocatalyst with boosted utilization efficiency in acidic overall water splitting

The industrialization of solid polymer electrolyte water electrolysis (SPEWE) dominantly relies on electrocatalyst with high stability and efficiency for oxygen evolution reaction (OER) catalysis. In this work, we report a facile method to construct α-Ni(OH)2@Ir core–shell nanoparticles as bifunctional electrocatalyst for acidic overall water splitting application. α-Ni(OH)2@Ir requires lower overpotentials (238 mV and 20 mV) to achieve 10 mA cm−2 in acidic OER and HER catalysis compared to benchmarked IrO2 (332 mV) and Pt/C (36 mV); meanwhile, the OER mass activity at 1.55 V vs. RHE was 92 fold higher than IrO2; HER mass activity at overpotential of 80 mV was 5 fold better than Pt/C. The boosted catalytic activity is due to the enhanced utilization efficiency of Ir stemmed from the ultrathin Ir shell (~1 nm). Moreover, 1.49 V is demanded for α-Ni(OH)2@Ir to attain 10 mA cm−2 in acidic overall water splitting, 110 mV lower than benchmarked Pt/C-IrO2 system. Meanwhile, stable catalytic performance is recorded for 20 h.

Structural Modulation from Cu3PS4 to Cu5Zn0.5P2S8: Single-Site Aliovalent-Substitution-Driven Second-Harmonic-Generation Enhancement.

Diamond-like (DL) chalcophosphates, which possess the merits of impressive second-harmonic-generation (SHG) responses, strong laser-induced damage thresholds, and low melting points, are highly desirable for IR nonlinear-optical (NLO) applications. Herein, a new quaternary DL chalcophosphate, Cu5Zn0.5P2S8, is successfully discovered, taking known Cu3PS4 as the template via a single-site aliovalent-substitution strategy. It crystallizes in the orthorhombic system with noncentrosymmetric space group Pmn21, and the 3D DL structure is built by corner-shared [(Cu/Zn)S4], [CuS4], and [PS4] tetrahedra. Compared with its parent Cu3PS4, Cu5Zn0.5P2S8 exhibits a good phase-matching capability and a sharply enhanced SHG effect (10Cu3PS4) benefiting from partial Zn substitution. Moreover, the structure-performance relationships have been illustrated by means of theoretical investigations. Such an aliovalent-substitution strategy based on known DL semiconductors might be widely applied for the discovery of high-performance IR NLO crystals.

Aliovalent-cation-substitution-induced structure transformation: a new path toward high-performance IR nonlinear optical materials

A quaternary IR-NLO thioantimonate, K2Ag3Sb3S7, designed using an aliovalent-cation-substitution-induced (ACSI) strategy based on the centrosymmetric K2Sb4S7 is reported.

Physical and Chemical Properties and Quality Control Methods of Hyaluronic Acid (Review)

Introduction. This review describes the physicochemical properties that determine the use of hyaluronic acid in ophthalmology. We have studied methods for determining hyaluronic acid using various analytical methods.Text. Hyaluronic acid is a high molecular weight glycosaminoglycan that consists of repeating disaccharides of N-acetylglucosamine and D-glucuronic acid. Carboxyl, hydroxyl and acetoamide groups give hydrophilic properties to the molecule of this anionic heteropolysaccharide. Depending on how the hyaluronic acid is obtained, its molecular weight varies over a wide range. Researchers developed methods for controlling hyaluronic acid, which include the turbidimetric titration method, the method of high-performance capillary electrophoresis and high-performance liquid chromatography and IR spectroscopic method.Conclusion. Due to its properties, hyaluronic acid is widely used as an active ingredient in pharmaceutical preparations. Today, there are a number of methods for the determination of hyaluronic acid, including the method of turbidimetric titration, the method of capillary electrophoresis. High performance liquid chromatography (HPLC) and IR spectroscopy methods are presented in the Japanese Pharmacopoeia and the European Pharmacopoeia. These techniques are widely used due to their high reproducibility, accuracy, and relative simplicity.

Carrier density modulation and photocarrier transportation of graphene/InSb heterojunction middle-wavelength infrared photodetectors

The photoresponse mechanism of graphene/InSb heterojunction middle-wavelength infrared (MWIR) photodetectors was investigated. The devices comprised a graphene/InSb heterojunction as a carrier-injection region and an insulator region of graphene on tetraethyl orthosilicate (TEOS) for photogating. The MWIR photoresponse was significantly amplified with an increase in the graphene/TEOS cross-sectional area by covering the entire detector with graphene. The graphene-channel dependence of the MWIR photoresponse indicated that the graphene carrier density was modulated by photocarrier accumulation at the TEOS/InSb boundary, resulting in photogating. The dark current of the devices was suppressed by a decrease in the graphene/InSb carrier-injection region and the formation of the heterojunction using an n-type InSb substrate. The results indicate that photocarrier transportation was dominated by the formation of a Schottky barrier at the interface of the graphene/InSb heterojunction and a Fermi-level shift under bias application. The high-responsivity and low-dark-current photoresponse mechanism was attributed to the graphene/InSb heterojunction diode behavior and the photogating effect. The devices combining the aforementioned features had a noise equivalent power of 0.43 pW / Hz1/2. The results obtained in our study will contribute to the development of high-performance graphene-based IR image sensors.