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Thermally excited oxygen activation is the key to realize gas sensing by semiconductor. However, the relevant strategies and mechanisms are rarely studied. Herewith, the model material of highly oxygen catalytic active Ir doped WO 3 (Ir-WO 3 ) is prepared to elucidate the impact of enhanced oxygen activation on sensing performance. Interestingly, the 0.5 wt% Ir doped WO 3 successfully reduced the working temperature of WO 3 from 370 to 260 ℃ and significantly enhanced the response from 25.1 to 127.9 (at 50 ppm) for acetone. Meanwhile, the sensor also has fast response/recovery times (∼8.3/3.8 s), long-term stability, low detection limit (19 ppb) and high selectivity. Gas sensitive performance tests, in situ -DRIFTS and DFT calculations reveal that the Ir doping facilitates the oxygen adsorption and activation, which can significantly weaken the activation energy of acetone at low temperatures and contribute to enhance sensing performance. Our work paves a new pathway to improving metal oxide-based gas sensors at lower operating temperatures.
Polycrystalline MgF 2 is an attractive mid-infrared laser host material, yet its widespread application in high-power systems is limited by its inferior thermal conductivity compared to single-crystal materials, resulting in inefficient heat dissipation. To address this challenge, we successfully designed and synthesized Fe 2+ : MgF 2 transparent ceramics using a strategic wet chemical coprecipitation method combined with hot-press sintering. This method enables precise Fe 2+ doping within the MgF 2 lattice (Fe x Mg 1-x F 2 , 0.0002≤x ≤ 0.05), with doping effects clearly confirmed by XRD, XPS, and TEM analyses. The resulting ceramics exhibit outstanding mid-infrared transmission properties, with 1-mm-thick samples achieving 90% linear transmittance at 5.7 μm wavelength. More importantly, Fe 2+ incorporation significantly enhances thermal conductivity—peaking at 20.3 W/(m·K), a substantial increase over the baseline value of 11.6 W/(m·K)—while simultaneously raising Vickers hardness to 5.49 ± 0.54 GPa, fulfilling the core design objective. This simultaneous achievement of high optical quality and exceptional thermal management demonstrates that Fe 2+ : MgF 2 transparent ceramics represent a highly promising and reliable candidate material for high-power mid-infrared laser applications.
Alkaline water electrolysis offers a promising route for large-scale hydrogen production, but its efficiency is limited by the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we designed a hierarchical composite electrocatalyst comprising iridium-doped nickel-cobalt phosphide nanoparticles (Ir-NiCoP/Ni5P4) encapsulated within nickel-iron layered double hydroxide nanosheets (NiFe-LDH). Oxygen vacancies (OV) were engineered on the surface via sodium borohydride reduction, yielding an optimized catalyst denoted as Ir-NiCoP/Ni5P4@NiFe-LDH-1-OV. The optimized catalyst delivers low overpotentials of 52.7 mV for HER and 197.3 mV for OER at 10 mA cm-2 and maintains remarkable stability over 100 h for overall water splitting. Moreover, the Ir-NiCoP/Ni5P4@NiFe-LDH catalyst exhibits overpotentials of 76.7 and 101.3 mV for HER and the ammonia oxidation reaction A in 1 M KOH + NH3·H2O, respectively.
Proton exchange membrane (PEM) water electrolysis has broad application prospects for clean hydrogen production owing to its high efficiency, compact structure, rapid response, and flexible load regulation. However, the sluggish kinetics of the oxygen evolution reaction (OER) under strongly acidic conditions still poses a major challenge to the development of efficient and stable acidic OER electrocatalysts. In this work, a low-crystallinity IrO x /Ir catalyst with a gradient-distributed IrO x coating was successfully prepared by a hydrothermal method. In acidic OER tests, the catalyst exhibited excellent electrocatalytic performance, delivering a mass activity 218 times higher than that of commercial IrO 2 at 1.55 V vs. RHE, and requiring an overpotential of only 231 mV to reach 10 mA·cm −2 . The incorporation of non-crystalline metallic Ir 0 significantly improves the electrical conductivity and intrinsic catalytic activity of the catalyst. Meanwhile, the outer layer of more crystalline iridium oxide effectively protects the highly active low-crystallinity iridium oxide in the interior from dissolution and corrosion, so that the catalyst shows no obvious activity decay after 300 h of continuous operation, indicating good stability.
To develop long-lifetime luminescent Iridium(III) [Ir(III)] complexes, two novel series ( a1 – a4 and b1 – b4) were designed and synthesized, and their structure-photophysical property relationships were systematically investigated. Notably, introducing a sulfur (S) atom simultaneously extends the luminescence lifetime and enhances the quantum yield of these complexes. Among them, b3 stands out as an exceptional time-resolved emission spectroscopy (TRES) probe due to its prolonged lifetime and high quenching efficiency by polydopamine (PDA). By leveraging dual mechanisms, PDA-mediated quenching of b3 and thiocholine (TCh)-inhibited dopamine (DA) polymerization, a sensitive luminescent platform for malathion (MAL) detection was developed. The resulting detection platform achieves an ultra-low limit of detection (LOD) 0.32 nM within a linear range of 0.001–15.0 μM. Notably, the long-lived b3 (τ = 1.665 μs) permits effective MAL detection even in a highly fluorescent RhB matrix using TRES (LOD = 13.2 nM), whereas steady-state emission spectra (SSES)-based detections fail under such conditions. The successful application of b3 in real-sample analysis demonstrates the great potential of Ir(III) complexes in TRES-based detection. This work not only expands the repertoire of TRES probes but also presents a highly effective luminescent platform for pesticide detection.
Precious metals (like Ir, Ru, and Pt) and their derivatives are the benchmark catalysts for water splitting in acidic media due to their high stability and activity. However, the high cost and scarcity of these materials hamper the large-scale applications. To solve this issue, construction of catalysts containing low content of precious metals with high intrinsic activity can be an efficient strategy, which expectedly can decrease the cost but meanwhile preserve the activity. Herein, we synthesized an IrW/WO3 array catalyst by in situ formation of IrW alloy on hierarchical WO3 nanosheet arrays. With extremely low Ir content of 1.25 wt % in 0.5 M H2SO4, this composite catalyst not only shows superior water oxidation activity (the overpotential at 10 mA cm–2 is only 229 mV, significantly lower than that of the commercial IrO2 (358 mV)) but also exhibits excellent proton reduction performance (the overpotential at −10 mA cm–2 is 49 mV, close to that of commercial Pt/C catalyst (42 mV)), showing promising bifunctionality for the overall water splitting. As a result, only 1.5 V is needed to drive the overall water splitting at 10 mA cm–2 with a good long-term stability under acidic conditions. These remarkable features can be ascribed to the abundant active sites exposed by the three-dimensional nanostructure, and the high intrinsic activity per Ir site. The theoretical calculation verifies that Ir sites in IrW surface after oxidation have a higher intrinsic activity than IrO2 for water oxidation. We believe this research can supply a strategy to design highly active and stable catalysts with low loading of noble metals for acidic water splitting.
Water-soluble amino acids have been confirmed as effective cloud condensation nuclei (CCN) materials. While their influence on the hygroscopicity of nitrates is still scarcely known. In this work, ammonium nitrate (AN) was mixed with glycine and alanine at various mole ratios to form internally mixed particles deposited onto a solid substrate, whose hygroscopic properties and phase states of ingredients were investigated using microscope and attenuated total reflection-Fourier transformed infrared spectroscopy (ATR-FTIR). For mixed AN/amino acid particles with abundant inorganic, AN crystallizes at lower RH than that of pure AN, while deliquescence relative humidities (DRHs) were close to pure AN. On hydration, the mixture composed of bis(amino acid) nitrates and mono(amino acid) nitrates formed at 14.6–60.8% RH and 23.6%–60.0% RH for AN/glycine and AN/alanine particles, respectively. When the inorganic and organic components were mixed with equal mole ratio, gradual water uptake and release took place due to the hygroscopic interplay between components. In the mixed particles with abundant amino acids, glycine and alanine still kept solid at highest RH on hydration. Hydrogen bonding interaction should account for the mutual suppression on individual crystal formation. The present hygroscopic study would help people understanding cloud condensation nuclei (CCN) ability of amino acids in atmosphere.
The TeO 2 -ZnO-Na 2 O glass system demonstrates significant promise for mid-infrared laser applications due to its high refractive index and low phonon energy, although it is inherently limited by poor thermal stability. Traditional methods aimed at enhancing thermal stability, such as the incorporation of intermediates, typically result in compromised optical performance. However, this study introduces a synergistic optimization strategy through strategic Ta 2 O 5 doping. A systematic analysis utilizing Differential Scanning Calorimetry (DSC), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and photoluminescence (PL) spectroscopy has uncovered a novel correlation between optical performance and average rather than maximum phonon energy. This discovery provides a refined theoretical framework for the design of tellurite glasses. The optimized Tm 3 -doped TZNT4 glass, with a glass transition temperature ( T g ) of 388 °C and a thermal stability range ( ΔT ) of 137 °C, demonstrates excellent absorption (9.1 ×10 −21 cm 2 ) and emission cross-sections (7.1 ×10 −21 cm 2 ) at 2 μm. This work establishes a structure-property-performance paradigm for tellurite glasses, effectively addressing the critical trade-off between thermal robustness and mid-infrared emission performance through rational composition engineering.
Methane, as an abundant resource, serves not only as an excellent fossil fuel but also as a pivotal feedstock for synthesizing high-value-added chemical products. Solar-driven methane conversion offers a highly promising pathway for the direct production of high-value chemicals such as methanol (CH 3 OH) and formaldehyde (HCHO) under mild conditions. However, the core challenge of this conversion process lies in the tendency of target products to undergo over-oxidation, resulting in low selectivity—a critical bottleneck that urgently requires breakthrough in this field. Herein, we constructed an Ir-modified CdS (Ir x /CdS) photocatalytic system and proposed that regulating the generation types of key reaction intermediates via metallic Ir is an effective strategy to enhance the selectivity of target products and suppress over-oxidation. In situ diffuse reflectance infrared Fourier transform spectroscopy ( in situ DRIFTS) confirmed that the types of key intermediates generated during methane activation differ, which decisively influences the product distribution. On pure CdS surfaces, the key intermediate *CH 3 O tends to participate in subsequent deep oxidation reactions via its O atom, ultimately leading to over-oxidized products like CO 2 . In contrast, after Ir loading, the key reaction intermediate shifts to *CH 3 . The Ir sites facilitate the conversion of *CH 3 to ‧CH 3 radicals through localized electron transfer, and the generated ‧CH 3 radicals rapidly combine with ‧OH radicals to selectively form CH 3 OH. The performance evaluation of photocatalytic methane conversion demonstrated that under conditions of 60 °C, 0.1 MPa, and molecular oxygen as the oxidant, the 0.50 wt% Ir-loaded Ir 0.50 /CdS sample exhibited optimal performance: the yield of oxygenated liquid products (CH 3 OH and HCHO) reached 509.2 μmol g −1 h −1 , with overall selectivity enhanced to 88 %. Characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) revealed the coexistence of two valence states of Ir on the catalyst surface (metallic Ir 0 and oxidized Ir 4+ ), with the metallic state being dominant. The strategy proposed in this work—regulating intermediate species generation via metal modification to inhibit over-oxidation—provides a novel approach for the efficient conversion of methane into high-value oxygenated chemicals.
Bifunctional Ir catalysts for proton exchange membrane (PEM) water electrolysis offer transformative potential by streamlining electrolyzer while achieving efficient performance remains challenging due to the distinct conditions required for oxygen and hydrogen evolution reaction (OER and HER). Herein, we propose a theory-directed design of Ir-based bifunctional catalysts, Ir nanoparticles supported on mesoporous carbon spheres embedded with MoSe 2 (Ir/MoSe 2 @MCS), leveraging a work function (WF)-induced spontaneous built-in electric field to enhance catalytic performance. They demonstrate exceptional kinetics for both OER and HER, and potential application in the practical PEM electrolyzer, showcasing the effectiveness of this innovative approach. Low overpotentials of 252 mV for OER and 28 mV for HER to drive 10 mA cm –2 were observed, and the PEM electrolyzer showed the current density of 2 A cm –2 at 1.87 V and maintained stable activity at 1.65 V for over 30 h to deliver 1 A cm –2 . Density functional theory calculations reveal that the WF difference at Ir/MoSe 2 interface induces a spontaneous built-in electric field with asymmetric charge distributions, that modulate the electronic environment and d -band center of Ir promoting bifunctional active phase formation. This significantly lowers reaction barriers for water splitting by balancing intermediate adsorption, endowing the bifunctional activity.
Visible light-harvesting cyclometalated Ir(III) complexes with 3-(2-benzothiazoly)-7-diethylaminocoumarin as the C^N cyclometalation ligands were prepared. The ancillary N^N ligand is either 6-piperidine naphthalimide-phenanthroline (Ir-1) or 9-aminophenanthroline (Ir-3). Ir(ppy)2(Phen) was prepared as model complex (Ir-2). Ir-1 and Ir-3 show strong absorption of visible light (ε = 109 000 M−1 cm−1 or 112 000 M−1 cm−1 at 486 or 484 nm, respectively). All the complexes show room temperature phosphorescence with drastically different phosphorescence quantum yields (ΦP = 4.3%, 44.3% and 46.0% for Ir-1, Ir-2 and Ir-3, respectively). With steady state and time-resolved spectra, as well as DFT calculations, the T1 excited states of Ir-1 and Ir-3 were proposed to be the 3IL state, whereas the 3MLCT state was proposed for Ir-2. Long-lived emissive triplet excited states (7.6 μs and 54.5 μs) were observed for Ir-1 and Ir-3, compared to the short T1 excited state lifetime of Ir-2 (1.2 μs). The complexes were used as triplet photosensitizers for triplet–triplet annihilation upconversion and upconversion quantum yields (ΦUC) of 19.3% and 12.7% were observed for Ir-1 and Ir-3, respectively. No upconversion was observed for Ir-2 under the same experimental conditions.
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