Hydrothermal Synthesis of SnO2 with Different Morphologies as Sensing Materials for HCHO Detection.

Morphology regulation is an effective strategy for improving the sensor sensitivity of transition metal oxide nanostructures. In this work, SnO2 with three different morphologies (nanorods, nanoparticles, and nanopillars) has been synthesized by a simple one-step solvothermal process with the addition of various solute ratios at 180 °C for 6 h for detecting formaldehyde (HCHO) at the optimum working temperature of 320 °C. Compared to nanorods and nanopillars, the created SnO2 nanoparticles exhibit a much faster response time and sensitivity than other samples, showing the fastest recovery time (18 s) with the highest sensitivity of 6-100 ppm of the HCHO gas. The sensing mechanism of the sensors is investigated by Brunauer-Emmett-Teller (BET) methods and X-ray photoelectron spectroscopy (XPS) analysis, revealing that the pore size distribution and amount of OV and OC improve the charge transfer and HCHO adsorption of nanoparticle sensors. Such an effect of morphology control on sensing performance paves an idea for the development of different structure-based HCHO sensors.

Recent Progress in Spinel Ferrite (MFe2O4) Chemiresistive Based Gas Sensors.

Gas-sensing technology has gained significant attention in recent years due to the increasing concern for environmental safety and human health caused by reactive gases. In particular, spinel ferrite (MFe2O4), a metal oxide semiconductor with a spinel structure, has emerged as a promising material for gas-sensing applications. This review article aims to provide an overview of the latest developments in spinel-ferrite-based gas sensors. It begins by discussing the gas-sensing mechanism of spinel ferrite sensors, which involves the interaction between the target gas molecules and the surface of the sensor material. The unique properties of spinel ferrite, such as its high surface area, tunable bandgap, and excellent stability, contribute to its gas-sensing capabilities. The article then delves into recent advancements in gas sensors based on spinel ferrite, focusing on various aspects such as microstructures, element doping, and heterostructure materials. The microstructure of spinel ferrite can be tailored to enhance the gas-sensing performance by controlling factors such as the grain size, porosity, and surface area. Element doping, such as incorporating transition metal ions, can further enhance the gas-sensing properties by modifying the electronic structure and surface chemistry of the sensor material. Additionally, the integration of spinel ferrite with other semiconductors in heterostructure configurations has shown potential for improving the selectivity and overall sensing performance. Furthermore, the article suggests that the combination of spinel ferrite and semiconductors can enhance the selectivity, stability, and sensing performance of gas sensors at room or low temperatures. This is particularly important for practical applications where real-time and accurate gas detection is crucial. In conclusion, this review highlights the potential of spinel-ferrite-based gas sensors and provides insights into the latest advancements in this field. The combination of spinel ferrite with other materials and the optimization of sensor parameters offer opportunities for the development of highly efficient and reliable gas-sensing devices for early detection and warning systems.

High efficiency and stable dye-sensitized solar cells with an organic chromophore featuring a binary pi-conjugated spacer.

We employed a binary spacer of orderly conjugated 3,4-ethyldioxythiophene and thienothiophene to construct a wide-spectral response organic chromophore for dye-sensitized solar cells, exhibiting a high power conversion efficiency of 9.8% measured under irradiation of 100 mW cm(-2) air mass 1.5 global (AM1.5G) sunlight and an excellent stability.

Enhanced Methane Sensing Properties of WO3 Nanosheets with Dominant Exposed (200) Facet via Loading of SnO2 Nanoparticles.

Methane detection is extremely difficult, especially at low temperatures, due to its high chemical stability. Here, WO3 nanosheets loaded with SnO2 nanoparticles with a particle size of about 2 nm were prepared by simple impregnation and subsequent calcination using SnO2 and WO3·H2O as precursors. The response of SnO2-loaded WO3 nanosheet composites to methane is about 1.4 times higher than that of pure WO3 at the low optimum operating temperature (90 °C). Satisfying repeatability and long-term stability are ensured. The dominant exposed (200) crystal plane of WO3 nanosheets has a good balance between easy oxygen chemisorption and high reactivity at the dangling bonds of W atoms, beneficial for gas-sensing properties. Moreover, the formation of a n⁻n type heterojunction at the SnO2-WO3 interface and additionally the increase of specific surface area and defect density via SnO2 loading enhance the response further. Therefore, the SnO2-WO3 composite is promising for the development of sensor devices to methane.

Highly stable hole-conductor-free perovskite solar cells based upon ammonium chloride and a carbon electrode.

Organic-inorganic hybrid perovskite solar cells (PSCs) have become a research hotspot due to the impressive photovoltaic performance. The perovskite film plays an extremely important role in the light-to-electricity conversion, meanwhile, the stability of PSCs is also an important factor affecting the application of devices. Here we demonstrate a kind of stable PSCs by using simple solution-process in an air enviroment with about 45% relative humidity. Firstly, the NH4Cl was added to the perovskite precursor solution to adjust the kinetics of crystallization and growth of active layer, and then obtain high-quality CH3NH3PbI3 perovskite films. Hydrophobic carbon electrode was used to protect the perovskite active layers and further improve the stability of PSCs, which optimized the structure of the devices at the same time. We adjusted the amount of NH4Cl in the perovskite precursor solution (PbI2: CH3NH3I: NH4Cl = 1: 1: x (x = 0 ∼ 1), and investigated the effect of that on the properties of perovskite active layers and PSCs. The above results showed that the devices achieved fully covered perovskite thin films and improved the photovoltaic performance of PSCs when the NH4Cl additive was x  = 0.8. The short-circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) were significantly enhenced. Under the condition of ambient air and no encapsulation, the PSCs exhibited good stability after 576 h test, and the PCE was still about 96% of the initial efficiency.

Calcination Method Synthesis of SnO2/g-C3N4 Composites for a High-Performance Ethanol Gas Sensing Application.

The SnO2/g-C3N4 composites were synthesized via a facile calcination method by using SnCl4·5H2O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), the field-emission scanning electron microscopy and transmission electron microscopy (FESEM and TEM), energy dispersive spectrometry (EDS), thermal gravity and differential thermal analysis (TG-DTA), and N2-sorption. The analysis results indicated that the as-synthesized samples possess the two dimensional structure. Additionally, the SnO2 nanoparticles were highly dispersed on the surface of the g-C3N4 nanosheets. The gas-sensing performance of the as-synthesized composites for different gases was tested. Moreover, the composite with 7 wt % g-C3N4 content (SnO2/g-C3N4-7) exhibits an admirable gas-sensing property to ethanol, which possesses a higher response and better selectivity than that of the pure SnO2-based sensor. The high surface area of the SnO2/g-C3N4 composite and the good electronic characteristics of the two dimensional graphitic carbon nitride are in favor of the elevated gas-sensing property.