Bismuth-Based Metal-Organic Framework as a Chemiresistive Sensor for Acetone Gas Detection.

Analyzing acetone in the exhaled breath as a biomarker has proved to be a non-invasive method to detect diabetes in humans with good accuracy. In this work, a Bi-gallate MOF doped into a chitosan (CS) matrix containing an ionic liquid (IL) was fabricated to detect acetone gas with a low detection limit of 10 ppm at an operating temperature of 60 °C and 5 V operating bias. The sensor recorded the highest response to acetone in comparison to other test gases, proving its high selectivity along with long-term stability and repeatability. The sensor also exhibited ultra-fast response and recovery times of 15 ± 0.25 s and 3 ± 0.1 s, respectively. Moreover, the sensor membrane also exhibited flexibility and ease of fabrication, making it ideal to be employed as a real-time breath analyzer.

Ag Nanocluster Production through DC Magnetron Sputtering and Inert Gas Condensation: A Study of Structural, Kelvin Probe Force Microscopy, and Optical Properties.

Silver nanoclusters are valuable for a variety of applications. A combination of direct current (DC) magnetron sputtering and inert gas condensation methods, employed within an ultra-high vacuum (UHV) system, was used to generate Ag nanoclusters with an average size of 4 nm. Various analytical techniques, including Scanning Probe Microscopy (SPM), X-ray Diffraction (XRD), Kelvin Probe Force Microscopy (KPFM), UV-visible absorption, and Photoluminescence, were employed to characterize the produced Ag nanoclusters. AFM topographic imaging revealed spherical nanoparticles with sizes ranging from 3 to 6 nm, corroborating data from a quadrupole mass filter (QMF). The XRD analysis verified the simple cubic structure of the Ag nanoclusters. The surface potential was assessed using KPFM, from which the work function was calculated with a reference highly ordered pyrolytic graphite (HOPG). The UV-visible absorption spectra displayed peaks within the 350-750 nm wavelength range, with a strong absorption feature at 475 nm. Additionally, lower excitation wavelengths resulted in a sharp peak emission at 370 nm, which became weaker and broader when higher excitation wavelengths were used.

Enhancing Hydrogen Sulfide Detection at Room Temperature Using ZIF-67-Chitosan Membrane.

Developing new materials for energy and environment-related applications is a critical research field. In this context, organic and metal-organic framework (MOF) materials are a promising solution for sensing hazardous gases and saving energy. Herein, a flexible membrane of the zeolitic imidazole framework (ZIF-67) mixed with a conductivity-controlled chitosan polymer was fabricated for detecting hydrogen sulfide (H2S) gas at room temperature (RT). The developed sensing device remarkably enhances the detection signal of 15 ppm of H2S gas at RT (23 °C). The response recorded is significantly higher than previously reported values. The optimization of the membrane doping percentage achieved exemplary results with respect to long-term stability, repeatability, and selectivity of the target gas among an array of several gases. The fabricated gas sensor has a fast response and a recovery time of 39 s and 142 s, respectively, for 15 ppm of H2S gas at RT. While the developed sensing device operates at RT and uses low bias voltage (0.5 V), the requirement for an additional heating element has been eliminated and the necessity for external energy is minimized. These novel features of the developed sensing device could be utilized for the real-time detection of harmful gases for a healthy and clean environment.

V2CTX MXene-based hybrid sensor with high selectivity and ppb-level detection for acetone at room temperature.

High-performance, room temperature-based novel sensing materials are one of the frontier research topics in the gas sensing field, and MXenes, a family of emerging 2D layered materials, has gained widespread attention due to their distinctive properties. In this work, we propose a chemiresistive gas sensor made from V2CTx MXene-derived, urchin-like V2O5 hybrid materials (V2C/V2O5 MXene) for gas sensing applications at room temperature. The as-prepared sensor exhibited high performance when used as the sensing material for acetone detection at room temperature. Furthermore, the V2C/V2O5 MXene-based sensor exhibited a higher response (S% = 11.9%) toward 15 ppm acetone than pristine multilayer V2CTx MXenes (S% = 4.6%). Additionally, the composite sensor demonstrated a low detection level at ppb levels (250 ppb) at room temperature, as well as high selectivity among different interfering gases, fast response-recovery time, good repeatability with minimal amplitude fluctuation, and excellent long-term stability. These improved sensing properties can be attributed to the possible formation of H-bonds in multilayer V2C MXenes, the synergistic effect of the newly formed composite of urchin-like V2C/V2O5 MXene sensor, and high charge carrier transport at the interface of V2O5 and V2C MXene.

Metal-organic frameworks for advanced transducer based gas sensors: review and perspectives.

The development of gas sensing devices to detect environmentally toxic, hazardous, and volatile organic compounds (VOCs) has witnessed a surge of immense interest over the past few decades, motivated mainly by the significant progress in technological advancements in the gas sensing field. A great deal of research has been dedicated to developing robust, cost-effective, and miniaturized gas sensing platforms with high efficiency. Compared to conventional metal-oxide based gas sensing materials, metal-organic frameworks (MOFs) have garnered tremendous attention in a variety of fields, including the gas sensing field, due to their fascinating features such as high adsorption sites for gas molecules, high porosity, tunable morphologies, structural diversities, and ability of room temperature (RT) sensing. This review summarizes the current advancement in various pristine MOF materials and their composites for different electrical transducer-based gas sensing applications. The review begins with a discussion on the overview of gas sensors, the significance of MOFs, and their scope in the gas sensing field. Next, gas sensing applications are divided into four categories based on different advanced transducers: chemiresistive, capacitive, quartz crystal microbalance (QCM), and organic field-effect transistor (OFET) based gas sensors. Their fundamental concepts, gas sensing ability towards various gases, sensing mechanisms, and their advantages and disadvantages are discussed. Finally, this review is concluded with a summary, existing challenges, and future perspectives.

Organic/Inorganic-Based Flexible Membrane for a Room-Temperature Electronic Gas Sensor.

A room temperature (RT) H2S gas sensor based on organic-inorganic nanocomposites has been developed by incorporating zinc oxide (ZnO) nanoparticles (NPs) into a conductivity-controlled organic polymer matrix. A homogeneous solution containing poly (vinyl alcohol) (PVA) and ionic liquid (IL) and further doped with ZnO NPs was used for the fabrication of a flexible membrane (approx. 200 µm in thickness). The sensor was assessed for its performance against hazardous gases at RT (23 °C). The obtained sensor exhibited good sensitivity, with a detection limit of 15 ppm, and a fast time response (24 ± 3 s) toward H2S gas. The sensor also showed excellent repeatability, long-term stability and selectivity toward H2S gas among other test gases. Furthermore, the sensor depicted a high flexibility, low cost, easy fabrication and low power consumption, thus holding great promise for flexible electronic gas sensors.

Flexible Cu3(HHTP)2 MOF Membranes for Gas Sensing Application at Room Temperature.

Mixed matrix membranes (MMMs), possessing high porosity, have received extensive attention for gas sensing applications. However, those with high flexibility and significant sensitivity are rare. In this work, we report on the fabrication of a novel membrane, using Cu3(HHTP)2 MOF (Cu-MOF) embedded in a polymer matrix. A solution comprising a homogenous suspension of poly-vinyl alcohol (PVA) and ionic liquid (IL), and Cu-MOF solid particles, was cast onto a petri dish to obtain a flexible membrane (215 µm in thickness). The sensor membrane (Cu-MOF/PVA/IL), characterized for its structure and morphology, was assessed for its performance in sensing against various test gases. A detection limit of 1 ppm at 23 °C (room temperature) for H2S was achieved, with a response time of 12 s. Moreover, (Cu-MOF/PVA/IL) sensor exhibited excellent repeatability, long-term stability, and selectivity towards H2S gas. The other characteristics of the (Cu-MOF/PVA/IL) sensor include high flexibility, low cost, low-power consumption, and easy fabrication technique, which nominate this sensor as a potential candidate for use in practical industrial applications.

A Highly Sensitive and Flexible Metal-Organic Framework Polymer-Based H2S Gas Sensor.

We report the fabrication of a novel metal-organic framework (MOF)-polymer mixed-matrix flexible membrane for the detection of hydrogen sulfide (H2S) gas at room temperature. This high-performance gas sensor is based on MOF-5 microparticles embedded on a conductivity-controlled chitosan (CS) organic membrane. The conductivity of the organic membrane is controlled by blending it with a glycerol ionic liquid (IL) at different concentrations. The sensor showed a remarkable detection sensitivity for H2S gas at a concentrations level as low as 1 ppm at room temperature. The MOF-5/CS/IL gas sensor demonstrates a highly desirable detection selectivity, fast response time (<8 s), recovery time of less than 30 s, and outstanding sensing stability averaging at 97% detection with 50 ppm of H2S gas. This composite having high sensitivity, low-power consumption, and flexibility holds great promise for addressing current challenges pertinent to environmental sustainability.

Fabrication and characterization of cellulose acetate-based nanofibers and nanofilms for H2S gas sensing application.

Electrospun nanofibers and solution-casting nanofilms were produced from an environmentally friendly cellulose acetate (CA) blended with glycerol (as an ionic liquid (IL)), mixed with polypyrrole (PPy, a conducting polymer) and doped with tungsten oxide (WO3) nanoparticles. The sensing membranes fabricated were used to detect H2S gas at room temperature and shown to exhibit high performance. The results revealed that the lowest operating temperature of both nanofiber and nanofilm sensors was 20 °C, with a minimum gas detection limit of 1 ppm. Moreover, the sensor exhibits a reasonably fast response, with a minimum average response time of 22.8 and 31.7 s for the proposed nanofiber and nanofilm based sensors, respectively. Furthermore, the results obtained indicated an excellent reproducibility, long-term stability, and low humidity dependence. Such distinctive properties coupled with an easy fabrication technique provide a promising potential to achieve a precise monitoring of harmful H2S gas in both indoor and outdoor atmospheres.

Sm3+-doped strontium barium borate phosphor for white light emission: Spectroscopic properties and Judd-Ofelt analysis.

This study aims to explore the spectroscopic properties of a Sr1.0Ba2.0B6O12:0.5Sm3+ phosphor synthesized using the solid-state reaction method. The morphology and elemental composition of the phosphor were determined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Phase changes and crystallite phases in the phosphor were studied using differential-scanning calorimetry and X-ray diffraction, respectively. Raman and Fourier-transform infrared spectra were used to identify the molecular vibrations in the phosphor. The energy bandgap and bonding nature of the phosphor were analyzed using the absorption spectrum. The nephelauxetic ratios determined from the absorption peaks revealed the presence of both ionic and covalent bonding in the phosphor. Judd-Ofelt parameters, along with radiative properties of the phosphor, were evaluated using the peaks in the absorption spectrum. Colorimetric analysis using the photoluminescence spectrum showed that the Sr1.0Ba2.0B6O12:0.5Sm3+ phosphor emits a cool-white light. The higher values of the spectroscopic quality factor, stimulated-emission cross-section, quantum efficiency, and the white-light emission of the phosphor suggest that Sr1.0Ba2.0B6O12:0.5Sm3+ is useful for display and lighting applications.

Low power consumption and fast response H2S gas sensor based on a chitosan-CuO hybrid nanocomposite thin film.

In this work, a novel selective and low temperature H2S gas sensor was fabricated based on copper (II) oxide nanoparticles (CuO NPs) in different concentrations, embedded in a conductivity-engineered organic (glycerol ionic liquid-doped chitosan) membrane/film. The sensing membranes of organic-inorganic nanocomposites (CS-IL-CuO) were prepared by casting method and were tested against H2S gas with reference to time at different temperatures and H2S gas concentrations. The fabricated sensor showed a fast response (14 s) and good sensitivity (15 ppm) towards H2S gas at a low temperature of 40 °C. Moreover, the sensor showed a high reversibility and less humidity dependence at 40 °C. Moreover, this type of hybrid nanocomposites sensor is easy and inexpensive to manufacture and is energy efficient. Thus, it has potential to be used for industrial applications in harsh environments.

Cellulose-Copper Oxide hybrid nanocomposites membranes for H2S gas detection at low temperatures.

We report on novel, sensitive, selective and low-temperature hydrogen sulfide (H2S) gas sensors based on metal-oxide nanoparticles incorporated within polymeric matrix composites. The Copper-Oxide (CuO) nanoparticles were prepared by a colloid microwave-assisted hydrothermal method that enables precise control of nanoparticle size. The sodium carboxymethyl cellulose (CMC) powder with 5% glycerol ionic liquid (IL) was prepared and mixed with different concentrations of CuO NPs (2.5-7.5 wt.%) to produce flexible and semi-conductive polymeric matrix membranes. Each membrane was then sandwiched between a pair of electrodes to produce an H2S gas sensor. The temperature-dependent gas sensing characteristics of the prepared sensors were investigated over the temperature ranges from 40 °C to 80 °C. The sensors exhibited high sensitivity and reasonably fast responses to H2S gas at low working temperatures and at a low gas concentration of 15 ppm. Moreover, the sensors were highly selective to H2S gas, and they showed low humidity dependence, which indicates reliable functioning in humid atmospheres. This organic-inorganic hybrid-materials gas sensor is flexible, with good sensitivity and low power consumption has the potential to be used in harsh environments.

Twofold Porosity and Surface Functionalization Effect on Pt-Porous GaN for High-Performance H2-Gas Sensors at Room Temperature.

The achievement of H2 detection, up to 25 ppm, at room temperature using sulfur-treated, platinum (Pt)-decorated porous GaN is reported in this study. This achievement is attributed to the large lateral pore size, Pt catalyst, and surface treatment using organic sulfide. The performance of H2-gas sensors is studied as a function of the operating temperature by providing an adsorption activation energy of 22 meV at 30 ppm H2, confirming the higher sensitivity of the sulfide-treated Pt-porous GaN sensor. Furthermore, the sensing response of the sulfide-treated Pt-porous GaN gas sensor increases with the increase in porosity (surface-to-volume ratio) and pore radii. Using the Knudsen diffusion-surface reaction equation, the H2 gas concentration profile is simulated and fitted within the porous GaN layer, revealing that H2 diffusion is limited by small pore radii because of its low diffusion rate. The simulated gas sensor responses to H2 versus the pore diameter show the same trend as observed for the experimental data. The sulfide-treated Pt-porous GaN sensor achieves ultrasensitive H2 detection at room temperature for 125 nm pore radii.

Use of light traps and differing light color to investigate seasonal abundance of the date palm pest, Oryctes agamemnon arabicus (Coleoptera: Scarabaeidae).

Oryctes agamemnon arabicus (Fairmaire) (Coleoptera: Scarabaeidae) is a date palm insect pest that causes damage to trunk and roots and can damage grass lawns in the United Arab Emirates (UAE) and other countries such as Oman, Saudi Arabia, and Tunisia. The goal of this study was to monitor population dynamics and to evaluate six light colors (white, green, red, yellow, blue, and infrared) and two lamp types (mercury and energy-saving) in light traps. Experiments were performed on a date palm farm during a 2 yr period (2010 and 2011). It was found that this insect is a univoltine pest with a single population peak. Adults appeared in the field around middle of April and early May and the population continued to build until maximum numbers were reached in mid June. No adults were found after the end of September. Photoperiod showed a significant correlation with the changes in adult population size. White light emitted from mercury lamps attracted significantly more O. agamemnon arabicus adults compared with the other tested light colors. Increasing the wattage of mercury lamps from 160 to 250 watt did not significantly increase the number of collected insects. The results demonstrated that light traps equipped with 160-watt mercury lamps emitting white light collected significantly the highest number of this insect among the other tested lamps.