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Tuning the electrical properties of graphene oxide by nitrogen ion implantation: Implication for gas sensing
摘要： Tailoring the electrical properties of graphene oxide (GO) is one of the important requirements for its application in future electronic devices. A modified Hummer’s method was employed in the preparation of GO and spray coated on glass substrates, subsequently drying at 60 °C for 6 h. The as prepared samples were implanted with 100 keV nitrogen ions at the fluences of 1E15, 5E15 and 1E16 ions/cm2. A peak shift to higher 2θ in XRD pattern indicates the reduction of GO to rGO after N ion implantation. The intensity ratio of G and D bands (IG/ID) for GO derived from the Raman analysis increased from 0.97 to 1.02 after implantation (1E16 ions/cm2). The EDS analysis confirms the implantation of N ions in GO. The electrical conductivity improved as a function of fluence, and observed to be high for the sample of 1E16 ions/cm2, and is tested for methanol sensing. Concentration dependent methanol sensing shows 5.9% response for 300 ppm. Above results show that ion implantation is a promising method for controlled reduction of GO for tuning the electrical properties.
关键词： Ion implantation,Gas sensing,Graphene oxide,Reduced graphene oxide
更新于2025-09-23 15:23:52
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Influence of Synthesis Conditions on Microstructure and NO2 Sensing Properties of WO3 Porous Films Synthesized by Non-Hydrolytic Sol–Gel Method
摘要： Nanostructured tungsten trioxide porous films were prepared by a non-hydrolytic sol–gel method following the inorganic route in which ethanol and PEG were used as the oxygen-donor and structure-directing reagent, respectively. The effects of aging time of the precursor solution, PEG content, and calcination temperature on the structure, morphology, and NO2 sensing properties of WO3 films were systematically investigated by using the techniques of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and gas sensing measurements. The results demonstrated that a series of WO3 films with different microstructures could be obtained by manipulating the synthesis parameters. Furthermore, a suitable synthesis condition of WO3 films for NO2 sensing application was determined.
关键词： NO2,non-hydrolytic sol–gel,WO3,gas sensing,porous films
更新于2025-09-23 15:23:52
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Influence of precursor solution concentration on the structural, optical and humidity sensing properties of spray-deposited TiO <sub/>2</sub> thin films
摘要： In the present paper, the influence of precursor concentration on the structural, optical, and humidity sensing properties of spray-deposited titanium dioxide (TiO2) films are investigated. The TiO2 thin films were successfully deposited by spraying different precursor concentrations such as 0.075 M, 0.1 M, and 0.125 M of titanium trichloride solution onto glass substrates. X-ray diffractometry (XRD) studies confirmed the polycrystalline anatase phase of TiO2 with dominant (101) plane. The crystallite size was found to increase with the increase in precursor concentration. The micro-strain and dislocation density in the film was observed to decrease as the crystallite size increased. The UV–vis spectra confirmed the optical absorbance edge of the samples shifted toward lower wavelengths with increased precursor concentration. The humidity sensing properties of the synthesized material were measured by monitoring the change in resistance of the sample with the change in relative humidity. The material synthesized with 0.1 M precursor concentration, by using the spray pyrolysis method, shows good sensitivity and has a response time of 77.5 s and fast recovery time of 3 s.
关键词： electrical,titanium dioxide,structural,gas sensing,spray pyrolysis
更新于2025-09-23 15:23:52
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Effect of defects in TiO2 nanoplates with exposed {001} facets on the gas sensing properties
摘要： The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy {001} crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective {001} facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete {001} facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete {001} facets is 70% higher than that of defective TiO2 nanoplates, which proves that the {001} facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 can be contributed to fewer adsorption sites and blocked electron transfer. This work presents a more direct evidence for explaining the important role of the complete {001} crystal facets in high sensitivity of TiO2 and also provides a new insight for preparing high sensitivity sensing materials.
关键词： TiO2 nanoplates,Defective,Acetone,{001} facets,Gas sensing
更新于2025-09-23 15:22:29
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Enabling selective absorption in perovskite solar cells for refractometric sensing of gases
摘要： perovskite solar cells are currently considered a promising technology for solar energy harvesting. their capability to deliver an electrical signal when illuminated can sense changes in environmental parameters. We have numerically analyzed the variation of the current delivered by a perovskite cell as a function of the index of refraction of air, that is in contact with the front surface of the cell. This calculation identifies which geometrical and material structures enhance this behavior. After replacing the top transparent electrode of a solar cell by an optimized subwavelength metallic grating, we find a large variation in the responsivity of the cell with respect to the change in the index of refraction of the surrounding medium. Such a refractometric sensor can be interrogated electronically, avoiding the cumbersome set-ups of spectral or angular interrogation methods. We present an adaptation of the performance parameters of refractometric sensors (sensitivity and figure of merit) to the case of opto-electronic interrogation methods. the values of sensitivity and figure of Merit are promising for the development of refractometric perovskite-based sensors.
关键词： gas sensing,optical sensor,perovskite solar cells,nanophotonic structures,refractometric sensing
更新于2025-09-23 15:21:01
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[Energy, Environment, and Sustainability] Sensors for Automotive and Aerospace Applications || Functional Films for Gas Sensing Applications: A Review
摘要： There are enormous functional materials which have been explored for gas sensing applications due to the fact that when a particular gas interacts with their surfaces, some alteration in their properties (optical, electrical, etc.) is observed. These functional materials are also termed as sensing ?lms, to be utilized as one of the essential components in a gas sensor. Other components include electrodes connected with sensing ?lm and data acquisition system coupled with it. During the past several decades, various metals, semiconductors, ceramics, and hybrid materials have been extensively explored for gas sensing applications. Selection of functional ?lm is dependent on the gas to be detected. A gas sensor should have some characteristics, viz., higher sensitivity, selectivity for target gas, least response and recovery time, higher reproducibility, and stability. Therefore, selection of appropriate sensing ?lm is highly required for a well-ef?cient gas sensor development. This article reviews the various kinds of sensing ?lms, their fundamental aspects along with the sensing mechanisms. Morphological changes in the materials and doping of other functional materials also affect the performance of a gas sensor. Hence, issues related to the ef?cient gas sensing are also covered in this article.
关键词： Nanomaterials,Sensing ?lms,Gas sensing,Functionalized ?lms
更新于2025-09-23 15:21:01
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A Novel Nanorod Self-Assembled WO <sub/>3</sub> ?· H <sub/>2</sub> O Spherical Structure: Preparation and Flexible Gas Sensor
摘要： In this work, a novel WO3·H2O spherical structure which was self-assembled by nanorods was achieved by using hydrothermal method. A comprehensive growth mechanism was proposed to explain the formation of three different type nanostructures. Flexible gas sensors were successfully fabricated based on such unique nanostructures. We found that these nanorods and nanoparticle’s self-assembled spherical structure showed excellent gas response to ammonia. This result may provide great benefit potential to further study for the preparation and gas performance of such self-assembled structure of WO3·H2O.
关键词： WO3·H2O,Nanostructures,Self-Assembly,Hydrothermal Process,Gas-Sensing
更新于2025-09-23 15:21:01
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Controlled synthesis of ultrathin MoS <sub/>2</sub> nanoflowers for highly enhanced NO <sub/>2</sub> sensing at room temperature
摘要： Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO2 gas sensor based on ultrathin MoS2 nanoflowers with high sensitivity at RT. The MoS2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm?1 and crystallisation in the hexagonal phase. The specific surface areas of the MoS2 grown at different times were measured by using the Brunauer–Emmett–Teller method. The largest specific surface area of 56.57 m2 g?1 was obtained for the MoS2 nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS2 nanostructures were investigated using oxidising and reducing gases, such as NO2, SO2, H2, CH4, CO and NH3, at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS2 nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO2 at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS2-48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices.
关键词： gas sensing,room temperature,hydrothermal synthesis,MoS2 nanoflowers,NO2 gas sensor
更新于2025-09-23 15:19:57
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Self-Assembled Nanostructured Tin Oxide Thin Films at the Air-Water Interface for Selective H <sub/>2</sub> S Detection
摘要： Simple, inexpensive and scalable strategies for metal oxide thin film growth are critical for potential applications in the field of gas sensing. Here, we report a general method for the synthesis of free-standing oxide thin films via a one-step, surfactant-free hydrothermal reaction wherein the oxide film forms at the air-water interface. Using SnO2 and PdO as model systems, we show that the thin films, thus formed, have lateral dimensions of the order of centimeters and thickness of the order of tens of nanometers. Transmission Electron Microscopy (TEM) has been used to understand the growth mechanism of the films. Based on these studies, we propose that the metal oxide particles formed in the bulk of the solution move to the interface and get trapped to form a continuous, polycrystalline film. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) measurements have been carried out to understand the structure, morphology and thickness of the films. Thickness tunability by varying the precursor concentration has been explored which in turn affects optical and gas sensing properties. Thin SnO2 films (30nm) revealed ultrasensitive response (R) of 25,000% to 6 ppm H2S at 150oC while demonstrating 25 ppb (R = 19.3%) as the experimental lowest limit of detection. The selectivity of these nanostructured films towards H2S stands tall among the other interfering gases, by exhibiting approximately two orders higher response magnitude. Furthermore, these thin films are highly stable at elevated temperatures.
关键词： Air-water interface,Gas sensing,SnO2,Metal oxides,Self-assembly
更新于2025-09-23 15:19:57
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State-of-the-Art Laser Gas Sensing Technologies
摘要： The increasing desire to detect and monitor in different fields such as in environmental air, life sciences, medical diagnostics, and planetary exploration demand the development of innovative sensing systems. Laser spectroscopy-based techniques have the advantages of high sensitivity, non-invasiveness and in situ, real-time observation. Because of these merits, we introduced state-of-the-art laser gas sensing technologies in this Special Issue. A total of 30 papers was received for consideration of publication. Among them, six manuscripts were rejected by the editor in the initial check process without peer review. The remaining manuscripts were all reviewed by at least two reputed reviewers in related fields from the USA, France, Italy, Germany, Russia, and so on. Finally, 16 manuscripts were accepted for publication in Applied Sciences-Basel. We would like to thank all of these numerous reviewers for their effort.
关键词： laser gas sensing,environmental monitoring,spectroscopy,medical diagnostics,planetary exploration
更新于2025-09-23 15:19:57