Multishelled Hollow Structures of Yttrium Oxide for the Highly Selective and Ultrasensitive Detection of Methanol

Recent progress of cataluminescence sensing based on gas-solid interfaces

Cataluminescence (CTL) has emerged as a sensing transduction principle of gas-solid interface for constructing gas sensors that present fast response, high sensitivity, and online monitoring. It has thus been widely associated with the field of chemical analysis and catalytic science. Herein, the latest developments in CTL sensors are reviewed, and the status quo of CTL-based gas sensing systems is discussed. In particular, the basic principles and sensing systems of CTL are outlined, including performance enhancement strategies for specific targets and recognition methods for multiple targets. Moreover, the important applications of CTL sensors are listed and classified, including environmental pollutant monitoring, product quality control, clinical diagnosis, and evaluation of catalyst performance. Finally, based on abundant case reports, the current conundrums of CTL sensors are summarized and their future development trends are also put forward.

A novel flexible CO2 gas sensor based on polyvinyl alcohol/yttrium oxide nanocomposite films

Polyvinyl alcohol/yttrium oxide (PVA/Y2O3) nanocomposite films with five different weight ratios of PVA and Y2O3 nanoparticles (NPs) were prepared using a simple solution casting method. The prepared polymer nanocomposite (PNC) films were examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). FTIR spectra exhibited a strong interaction between the PVA matrix and Y2O3 NPs. SEM results indicated that Y2O3 NPs were properly dispersed in the PVA matrix. The thermal stability of the PVA/Y2O3 nanocomposite films was found to be dependent on Y2O3 NP loading (wt%) in the nanocomposite films. Furthermore, chemiresistive gas sensing properties of the PVA/Y2O3 nanocomposite films were evaluated and the sensing parameters including sensing response, operating temperature, selectivity, stability, response/recovery time, and repeatability were systematically investigated based on the change in electrical resistance of the nanocomposite film in the presence of carbon dioxide (CO2) gas. The maximum sensing response (S) of 92.72% at a concentration of 100 ppm under an optimized operating temperature of 100 °C with a fast response/recovery time of ∼15/11 s towards CO2 gas detection was observed for the PVA/Y2O3 nanocomposite film with 5 wt% loading of Y2O3 NPs in the PVA matrix. The finding in this work suggest that Y2O3 NPs are sufficiently fast as a CO2 gas sensing material at a relatively low operating temperature. Moreover, the key role of the Y2O3 NPs in modulating the electrical and gas sensing properties of the PVA matrix is discussed here.

Kinetics-Driven Dual Hydrogen Spillover Effects for Ultrasensitive Hydrogen Sensing

Palladium (Pd)-modified metal oxide semiconductors (MOSs) gas sensors often exhibit unexpected hydrogen (H2 ) sensing activity through a spillover effect. However, sluggish kinetics over a limited Pd-MOS surface seriously restrict the sensing process. Here, a hollow Pd-NiO/SnO2 buffered nanocavity is engineered to kinetically drive the H2 spillover over dual yolk-shell surface for the ultrasensitive H2 sensing. This unique nanocavity is found and can induce more H2 absorption and markedly improve kinetical H2 ab/desorption rates. Meanwhile, the limited buffer-room allows the H2 molecules to adequately spillover in the inside-layer surface and thus realize dual H2 spillover effect. Ex situ XPS, in situ Raman, and density functional theory (DFT) analysis further confirm that the Pd species can effectively combine H2 to form Pd-H bonds and then dissociate the hydrogen species to NiO/SnO2 surface. The final Pd-NiO/SnO2 sensors exhibit an ultrasensitive response (0.1-1000 ppm H2 ) and low actual detection limit (100 ppb) at the operating temperature of 230 °C, which surpass that of most reported H2 sensors.

Optimization of Fe/Ni organic frameworks with core-shell structures for efficient visible-light-driven reduction of carbon dioxide to carbon monoxide

To address CO₂ emissions caused by the overuse of fossil fuels, photocatalytic CO₂ reduction from metal-organic frameworks (MOFs) to valuable chemicals is critical for energy conversion and storage. Core-shell MOFs improve interfacial interactions, increasing the number of active sites in the catalyst, thereby improving the photocatalytic reduction. In this work, the catalytic performance of Fe/Ni-MOFs toward photocatalytic CO₂ reduction was improved using a bimetallic strategy. We successfully synthesized a series of Fe/Ni-MOFs with a core-shell structure using a single-step approach combined with hydrothermal synthesis. By altering the synthesis conditions of the bimetallic organic skeleton and contrasting it with a single MOF, we successfully synthesized Fe/Ni-T120 through an efficient photocatalytic reduction of CO₂. The results of photocatalytic CO₂ reduction experiments indicated that upon using [Ru(bpy)₃]Cl₂·6H₂O as a photosensitizer and triethanolamine (TEOA) and acetonitrile (MeCN) as sacrificial agents, the CO evolution rate of Fe/Ni-T120 reached 9.74 mmol g^-1 h^-1 and the CO₂ to CO selectivity reached up to 92.1%. Additionally, Fe/Ni-T120 has a broad response range to visible light, a high photocurrent intensity, good chemical stability, and strong photocatalytic efficiency, even after repeated cycles. This study proposes a straightforward method for producing adaptable and stable MOFs for effective photocatalytic CO₂ reduction that is driven by visible light.

Efficient Photoinduced Thermocatalytic Chemiluminescence System Based on the Z-Scheme Heterojunction Ag3PO4/Ag/Bi4Ti3O12 for H2S Sensing

Cataluminescence as a highly efficient gas transduction principle has attracted wide attention among research in environmental monitoring and clinical diagnosis with increasing awareness of human safety. Nowadays, the development of innovation sensing systems and the construction of the sensing mechanism to improve the analytical performance of compounds remain a major challenge. Herein, we construct an advanced photoinduced thermocatalytic chemiluminescence (PI-TC-CL) gas-sensing system via the introduction of a Z-scheme heterojunction Ag₃PO₄/Ag/Bi₄Ti₃O₁₂ to achieve higher efficient detection of H₂S. The unique electron transport path of the Z-scheme heterojunction and the LSPR effect of Ag nanoparticles fascinate the generation of the photoinduced electron-hole pair on the surface of catalysts when stimulated by LED lamps and slow down the recombination of electron-hole pairs under thermal conditions. Thus, based on the cooperative effect of the Z-scheme heterojunction AgPO/Ag/BTO and PI-TC-CL system, we have successfully established an efficient H₂S CTL detection system, which has a response three times higher than that on the traditional CTL system and even 45 times higher than that on BTO and ranges among the best of the state-of-the-art CTL performance in H₂S detection with the linear range of 0.095-8.87 μg mL^-1 and a limit of detection of 0.0065 μg mL^-1. Besides, to explore the gas-sensing mechanism, the synergetic effects of photoinduction and thermal catalysis are investigated thoroughly via conductivity and electrochemical experiments. This research provides a new perspective of engineering highly efficient catalysts and ingenious sensor systems through designing the nanostructure of materials and synergism catalytic mechanism.

Multishell SnO2 Hollow Microspheres Loaded with Bimetal PdPt Nanoparticles for Ultrasensitive and Rapid Formaldehyde MEMS Sensors

Low-cost and real-time formaldehyde (HCHO) monitoring is of great importance due to its volatility, extreme toxicity, and ready accessibility. In this work, a low-cost and integrated microelectromechanical system (MEMS) HCHO sensor is developed based on SnO₂ multishell hollow microspheres loaded with a bimetallic PdPt (PdPt/SnO₂-M) sensitizer. The MEMS sensor exhibits a high sensitivity to HCHO ((R_a/R_g - 1) % = 83.7 @ 1 ppm), ultralow detection limit of 50 ppb, and ultrashort response/recovery time (5.0/7.0 s @ 1 ppm). These excellent HCHO sensing properties are attributed to its unique multishell hollow structure with a large and accessible surface, abundant interfaces, suitable mesoporous structure, and synergistic catalytic effects of bimetal PdPt. The well-defined multishell hollow structure also shows fascinating capacities as good hosts for noble metal loading. Therefore, PdPt bimetallic nanoparticles can be employed to construct a synergistic sensitizer with a high content and good dispersity on this multishell hollow structure, further exhibiting a reduced working temperature and ultrasensitive detection of HCHO. This PdPt/SnO₂-M-based MEMS sensor presents a unique and highly sensitive means to detect HCHO, establishing its great promise for potential application in environmental monitoring.

Superlattice films of semiconducting oxide and rare-earth hydroxide nanosheets for tunable and efficient photoluminescent energy transfer

Europium and terbium doped layered gadolinium hydroxides were prepared by microwave assisted hydrothermal precipitation. They were subsequently exfoliated into nanosheets by sonication treatment in formamide. The thickness of the nanosheets (LGdH:Eu and LGdH:Tb) was found to be approximately 1 nm, exemplifying a single-layer feature. Multilayer and superlattice films were prepared through layer-by-layer (LbL) deposition of exfoliated hydroxide nanosheets with a polyanionic electrolyte (polystyrene sulfonate, PSS) and heteroassembly with semiconducting oxide nanosheets (Ti0.87O20.52- and TaO3-), respectively. Compared to the multilayers of (LGdH:Eu/PSS)n and (LGdH:Tb/PSS)n, the superlattices of (LGdH:Eu/Ti0.87O20.52-)n and (LGdH:Tb/TaO3-)n exhibited significantly enhanced photoluminescence intensity, ∼14 times and ∼5 times, respectively. The photoenergy absorbed by the semiconducting nanosheets can be transferred to the excited states of rare-earth hydroxide nanosheets for enhanced photoluminescence emission. Further investigation on the stacking sequence of the nanosheets revealed that direct neighboring and energy level matching with semiconducting nanosheets was essential for realizing efficient energy transfer across the nanosheet interface. Annealing at 600 °C could further enhance the emission intensity of the superlattice structured films. The current work demonstrates an important strategy for hetero-assembling nanosheets at the molecular level with a carefully designed interface for tunable and enhanced functionalities.

A study on the cataluminescence of propylene oxide on FeNi layered double hydroxides/graphene oxide

In this work, FeNi layered double hydroxides/graphene oxide (FeNi LDH/GO) was prepared, which exhibits excellent selective cataluminescent performance towards propylene oxide.

High-Performance Cataluminescence Sensor Based on Nanosized V2O5 for 2-Butanone Detection

The development of high-performance sensors is of great significance for the control of the volatile organic compounds (VOCs) pollution and their potential hazard. In this paper, high crystalline V₂O₅ nanoparticles were successfully synthesized by a simple hydrothermal method. The structure and morphology of the prepared nanoparticles were characterized by TEM and XRD, and the cataluminescence (CTL) sensing performance was also investigated. Experiments found that the as-prepared V₂O₅ not only shows sensitive CTL response and good selectivity to 2-butanone, but also exhibits rapid response and recovery speed. The limit of detection was found to be 0.2 mg/m³ (0.07 ppm) at a signal to noise ratio of 3. In addition, the linear range exceeds two orders of magnitude, which points to the promising application of the sensor in monitoring of 2-butanone over a wide concentration range. The mechanism of the sensor exhibiting selectivity to different gas molecules were probed by quantum chemistry calculation. Results showed that the highest partial charge distribution, lowest HOMO-LUMO energy gap and largest dipole moment of 2-butanone among the tested gases result in it having the most sensitive response amongst other VOCs.