We present an experimental study on the influence of sub-stoichiometric WO_3−x phase upon gas sensing performance. Our work shows that the sub-stoichiometric WO_3−x can be used to enhance the low temperature sensing performance.

In this work, the high crystalline copper oxide (CuO) nanoparticles were fabricated by a hydrothermal method, and their structural properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The sensing results show that CuO nanoparticles exhibit enhanced sensitivity and good selectivity for hydrogen sulfide (H₂S) gas at a low temperature. There are two working mechanisms involved in the H₂S sensing based on CuO nanoparticle sensors. They are the H₂S oxidation mechanism and the copper sulphide (CuS) formation mechanism, respectively. The two sensing mechanisms collectively enhance the sensor’s response in the H₂S sensing process. The Cu–S bonding is stable and cannot break spontaneously at a low temperature. Therefore, the CuS formation inhibits the sensor’s recovery process. Such inhibition gradually enhances as the gas concentration increases from 0.2 ppm to 5 ppm, and it becomes weaker as the operating temperature rises from 40 °C to 250 °C. The XPS results confirmed the CuS formation phenomenon, and the micro Raman spectra demonstrated that the formation of CuS bonding and its decomposition can be effectively triggered by a thermal effect. Gas-sensing mechanism analysis supplied abundant cognition for the H₂S sensing phenomena based on CuO materials.

High performance broadband absorbers in the midinfrared atmospheric transparency windows are of great importance in various applications, such as energy harvesting, photodetection, radiative cooling, and stray light elimination. In recent years, great efforts have been made to develop absorbers using plasmonic nanostructured resonators in the infrared regime. Although these approaches promise distinct advantages in performance enhancement, they still suffer several obstacles, e.g., limitations on sample size, bandwidth, and fabrication throughput. Here, a large‐area broadband wide‐angle plasmonic metasurface absorber with nearly perfect absorption over the range of midwavelength infrared atmospheric transparent window (3–6 µm) is proposed and experimentally demonstrated. The metasurface absorber is basically comprised of a monolayer of sub‐micrometer‐sized polystyrene spheres self‐assembled on an opaque metallic substrate and coated with metal–insulator–metal three‐layer thin film, and fabricated by using simple, low‐cost self‐assembly techniques. Numerical simulation analyses not only corroborate the experimental observations, but also discover that such broadband absorption effect is attributed to hybrid plasmonic multiple resonances. The combination of the significant light absorption effect, compact design, and high‐yield self‐assembly fabrication process suggests that the proposed absorber has wide prospect application in integrated optical and optoelectronic systems.

Recently, CsPbX₃ (X = Cl, Br, and I) perovskite quantum dots (QDs) have exhibited significant potential for application in the field of lighting. However, their self-absorption and agglomeration significantly decrease their photoluminescence when their solution is centrifuged to form a powder; this hinders their applications in the field of solid-state lighting. Currently, there is lack of efficient solutions to overcome the self-absorption issue for CsPbX₃ QDs. Thus, herein, an effective strategy is proposed via the in situ growth of CsPbBr₃ (CPB) QDs in a mesoporous silica (m-SiO₂) matrix, where self-absorption originating from the agglomeration of the QD powder is distinctly suppressed in the m-SiO₂ matrix. Furthermore, due to its higher transmissivity, some photons can transport along the channels of m-SiO₂ with less light loss. As a result, the photoluminescence quantum yield (PLQY) of 68% for the CsPbBr₃/m-SiO₂ (CPB/MS) powder is distinctly higher than that of the discrete CPB powder (36%). In addition, the chemical stability, thermal quenching and luminous decay were evidently improved for the CPB/MS nanocomposite. Finally, a remote flexible light-emitting diode with ultrahigh stability and arbitrary bending angle was achieved, which presented a pathway for the application of CPB QDs in solid-state lighting.

Titanium dioxide (TiO2) ultrathin films with different thicknesses below 20 nm were grown by atomic layer deposition (ALD) on silicon substrates at 300 °C. Spectroscopic ellipsometry (SE) measurements were operated to investigate the effect of thickness on the optical properties of ultrathin films in the spectra range from 200 to 1000 nm with Forouhi–Bloomer (F-B) dispersion relation. It has been found that the refractive index and extinction coefficient of the investigated TiO2 ultrathin film increase while the band gap of TiO2 ultrathin film decreases monotonically with an increase in film thickness. Furthermore, with the purpose of studying the temperature dependence of optical properties of TiO2 ultrathin film, the samples were annealed at temperature from 400 to 900 °C in N2 atmosphere. The crystalline structure of deposited and annealed films was deduced by SE and supported by X-ray diffraction (XRD). It was revealed that the anatase TiO2 film started to transform into rutile phase when the annealing temperature was up to 800 °C. In this paper, a constructive and effective method of monitoring the phase transition in ultrathin films by SE has been proposed when the phase transition is not so obvious analyzed by XRD.

CeO₂ nanoparticles modified WO₃ nanocube materials were prepared. CeO₂ nanoparticles endowed the WO₃ with good hydrophobic properties and dissociative oxygen adsorption. The response and moisture resistance were synchronized.