Superior acetone sensor based on hetero-interface of SnSe2/SnO2 quasi core shell nanoparticles for previewing diabetes

Excellent acetone sensing enabled by tunable metal organic framework derived TiO2 nanodisks

Annealing plays a crucial role for in enhancing the gas sensing properties of MOF-derived TiO2 (MIL-125). Generally, TiO2 transforms into different polymorphs (anatase, rutile, and brookite) during annealing, each with unique crystal structures and gas sensing properties. The aim of this research was to investigate the impact of annealing (500-650 °C) on the properties of MIL-125, which had not been previously studied. Through precise control, a 3D nanodisk morphology was obtained, where the MIL-125 surface gradually becomes rough at 600 °C (MT600). At 650 °C (MT650), anatase transforms completely into rutile, resulting in significant collapse and a decrease in diameter size from 700 nm to 300 nm. The XPS and EPR study showed that the MIL-125 nanodisks contain high amount of oxygen vacancies, thus giving higher response to various gases, specifically to acetone. The MT600 sensor maintained a good sensor response (for instance SR∼21 toward 500 ppm acetone) at 250 °C for isntance SR. Even at 1 ppm, it exhibited an SR value of ∼6.7. A fast response (TRes ∼13 s) and recovery time (TRec ∼12 s) of MT600 sensor at 100 ppm acetone was obtained. The gas sensing mechanism is thoroughly discussed, and the electron migration process in acetone detection is analyzed, offering new sensitive materials and insights for improving metal-oxide-semiconductor gas sensors.

Enhanced oxygen anions generation on Bi2S3/Sb2S3 heterostructure by visible light for trace H2S detection at room temperature

Bismuth sulfide (Bi2S3) possesses unique properties that make it a promising material for effective hydrogen sulfide (H2S) detection at room temperature. However, when exposed to light, the oxygen anions (O2-(ads)) adsorbed on the surface of Bi2S3 can react with photoinduced holes, ultimately reducing the ability to respond to H2S. In this study, Bi2S3/Sb2S3 heterostructures were synthesized, producing photoinduced oxygen anions (O2-(hv)) under visible light conditions, resulting in enhanced H2S sensing capability. The Bi2S3/Sb2S3 heterostructure sensor exhibits a two-fold increase in sensing response to 500 ppb H2S under in door light conditions relative to its performance in darkness. Additionally, the sensing response of the Bi2S3/Sb2S3 sensor (Ra/Rg= 23.3) was approximately five times higher than pure Bi2S3. The improved sensing performance of the Bi2S3/Sb2S3 heterostructures is attributable to the synergistic influence of the heterostructure configuration and light modulation, which enhances the H2S sensing performance by facilitating rapid charge transfer and increasing active sites (O2-(hv)) when exposed to visible light.

Electronic structure analysis of NiO quantum dot-modified jackfruit-shaped ZnO sensors and sensing properties investigation of their highly sensitive and selective for butyl acetate

Detection of flammable, explosive and toxic butyl acetate helps to avoid accidents and protect health in industrial production. However, there are few reports on butyl acetate sensors, especially highly sensitive, low detection limit and highly selective ones. In this work, density functional theory (DFT) analyzes the electronic structure of sensing materials and the adsorption energy of butyl acetate. The effects of Ni element doping, oxygen vacancy constructions, and NiO quantum dot modifications on the modulation of the electronic structure of ZnO and on the adsorption energy of butyl acetate are investigated in detail. Based on the DFT analysis, the NiO quantum dot modified jackfruit-shaped ZnO is synthesized via thermal solvent method reduction. The NiO/ZnO sensor has a response 502.5 for 100 ppm butyl acetate with 100 ppb detection limit, and the response for 100 ppm butyl acetate is at least 6.2 times higher than 100 ppm methanol, 100 ppm benzene, 100 ppm triethylamine, 100 ppm isopropanol, 100 ppm ethyl acetate and 100 ppm formic acid. X-ray photoelectron spectroscopy (XPS) explores the change of oxygen vacancies in sensor accompanied with the addition of Ni element and reveales the reason for the change of oxygen vacancies.

Electrospun Fibrous Nanocomposite Sensing Materials for Monitoring Biomarkers in Exhaled Breath

Human-exhaled breath mainly contains water, oxygen, carbon dioxide, and endogenous gases closely related to human metabolism. The linear relationship between breath acetone and blood glucose concentration has been revealed when monitoring diabetes patients. Considerable attention has been directed toward developing a highly sensitive volatile organic compounds (VOCs) sensing material that can detect breath acetone. In this study, we propose a tungsten oxide/tin oxide/silver/poly (methyl methacrylate) (WO₃/SnO₂/Ag/PMMA) sensing material fabricated using the electrospinning technique. By monitoring the evolution of sensing materials' extinction spectra, low concentrations of acetone vapor can be detected. Moreover, the interfaces between SnO₂ and WO₃ nanocrystals construct n-n junctions, which generate more electron-hole pairs than those without such structure when the light strikes. This helps to improve the sensitivity of sensing materials when they are subjected to acetone surroundings. The established sensing materials (WO₃/SnO₂/Ag/PMMA) exhibit a sensing limit of 20 ppm for acetone vapor and show specificity for acetone even in ambient humidity.

Experimental and density functional study of the light-assisted gas-sensing performance of a TiO2-CoFe2O4 heterojunction

Toluene gas as a solvent is widely present in industrial production and indoor decoration, and can seriously harm human health even at low concentrations. Furthermore, toluene can be used as a typical biomarker for disease diagnosis. Therefore, the detection of toluene gas is very important. Herein, a hydrothermal method was used to successfully prepare a TiO₂-CoFe₂O₄ heterostructure for detecting toluene gas. The ultraviolet (UV)-visible diffuse reflectance spectra and photoluminescence spectra showed that the bandgap of the heterojunction was considerably shorter than those of pure TiO₂ and CoFe₂O₄, and the recombination of electron-hole pairs was inhibited. At the same time, the response value of the TiO₂-CoFe₂O₄ heterojunction was 10.5 for 20 ppm toluene at 219 °C, which was much better than those of pure TiO₂ and CoFe₂O₄. Moreover, its response value further increased under UV irradiation. In addition, density functional theory (DFT) was innovatively employed in this study to explain in detail how the heterojunction and UV irradiation can improve gas sensitivity through the calculation of the material energy band, adsorption energy, etc. This work provides a good reference for the preparation of high-efficiency and high-sensitivity gas sensors.

WS2 Nanorod as a Remarkable Acetone Sensor for Monitoring Work/Public Places

Here, we report the synthesis of the WS₂ nanorods (NRs) using an eco-friendly and facile hydrothermal method for an acetone-sensing application. This study explores the acetone gas-sensing characteristics of the WS₂ nanorod sensor for 5, 10, and 15 ppm concentrations at 25 °C, 50 °C, 75 °C, and 100 °C. The WS₂ nanorod sensor shows the highest sensitivity of 94.5% at 100 °C for the 15 ppm acetone concentration. The WS₂ nanorod sensor also reveals the outstanding selectivity of acetone compared to other gases, such as ammonia, ethanol, acetaldehyde, methanol, and xylene at 100 °C with a 15 ppm concentration. The estimated selectivity coefficient indicates that the selectivity of the WS₂ nanorod acetone sensor is 7.1, 4.5, 3.7, 2.9, and 2.0 times higher than xylene, acetaldehyde, ammonia, methanol, and ethanol, respectively. In addition, the WS₂ nanorod sensor also divulges remarkable stability of 98.5% during the 20 days of study. Therefore, it is concluded that the WS₂ nanorod can be an excellent nanomaterial for developing acetone sensors for monitoring work/public places.