Search Results (382)

The present paper reports the preparation of a nanocomposite thin film consisting of calcium itaconate and graphene oxide (GO). The composite is a black powder consisting of individual shiny prismatic crystals at varying degrees of maturity. The crystal size distribution is quite narrow: from 3.6 to 6.2 μm in length and from 0.7 to 1.1 μm in width. Thin-film-based acetone sensor made of a nanocomposite was fabricated by spin coating of calcium itaconate–GO nanoparticles on glass plates. The thin-film acetone sensor was characterized using FTIR, XRD, SEM, TEM, and the low-temperature nitrogen sorption–desorption method. The sensor response time is 7.66 ± 0.07 s (s_r = 0.92%), and the relaxation time when blowing the surface with clean air or inert gas (nitrogen, argon) is 9.26 ± 0.12 s (s_r = 1.28%). The sensing mechanism of the sensor for detecting acetone at room temperature was also is proposed based on phenomenological understanding due to the absence of direct electronic/charge-transport evidence. Full article

Metal oxide semiconductor (MOS)-based chemiresistive gas sensors, attributable to their low cost, compact structure, and long operational lifetime, have been widely employed for the detection and monitoring of trace ozone (O₃) in environmental air. Moreover, as ozone is a highly reactive oxidizing species extensively used in medical device sterilization, hospital disinfection, and food processing and preservation, accurate monitoring of ozone concentration is also essential in medical sanitation and food safety inspection. However, their practical applications are often limited by insufficient sensitivity and the requirement for elevated operating temperatures. In this study, Au-modified indium oxide (Au-In₂O₃) nanocomposite sensing materials were synthesized via a hydrothermal route followed by surface modification. Structural and morphological characterizations confirmed the uniform dispersion of Au nanoparticles on the In₂O₃ surface, which is expected to enhance the interaction between the sensor and target gas molecules. The resulting Au-In₂O₃ sensor exhibited excellent O₃ sensing performance under room-temperature conditions. Compared with pristine In₂O₃, the Au-In₂O₃ sensor with 1.0 wt% Au modification demonstrated a remarkably enhanced response of 1398.4 toward 1 ppm O₃ at room temperature. Moreover, the corresponding response/recovery times were shortened to 102/358 s for Au-In₂O₃. The outstanding O₃ sensing performance can be attributed to the synergistic effects of Au nanoparticles, including the spillover effect and the formation of a Schottky junction at the Au-In₂O₃ interface. These results suggest that Au-modified In₂O₃ cauliflower represents a highly promising candidate material for high performance O₃ sensing at low operating temperatures. Full article

Efficient synthesis routes for zinc oxide nanoparticles (ZnO NPs) that are rapid and non-toxic and operate at room temperature (RT) are essential to expand accessibility, minimize environmental impact, and enable integration with temperature-sensitive substrates. In this work, ZnO NPs were synthesized by probe ultrasonication at RT for durations from 30 s to 10 min and benchmarked against our previously reported water bath sonication method. A 10-min probe treatment yielded highly uniform ZnO NPs with particle sizes of 60–550 nm and a specific surface area of up to 75 m² g⁻¹, compared to ~38 m² g⁻¹ for bath sonication. These features were largely preserved after calcination at 500 °C. When integrated into chemiresistive devices, the resulting ZnO (P(10))-based sensors exhibited pronounced selectivity toward styrene, showing reversible responses at low concentrations (10–50 ppm) and stronger signals at higher levels (up to 200 ppm, with resistance changes reaching 2930%). The sensors demonstrated stable operation across 10–90% relative humidity, and consistent performance from −20 °C to 180 °C. Flexibility tests confirmed reliable sensing after 100 bending cycles at 30°. Overall, RT-probe ultrasonication offers a rapid, scalable, and eco-friendly route to ZnO NPs with tunable properties, opening new opportunities for flexible gas sensing. Full article

Exhaled breath analysis has gained considerable interest as a noninvasive diagnostic tool capable of detecting volatile organic compounds (VOCs) and inorganic gases that serve as biomarkers for various diseases. Polymer-based gas sensors have garnered significant attention due to their high sensitivity, room-temperature operation, excellent flexibility, and tunable chemical properties. This review comprehensively summarized recent advancements in polymer-based gas sensors for the detection of disease biomarkers in exhaled breath. The gas-sensing mechanism of polymers, along with novel gas-sensitive materials such as conductive polymers, polymer composites, and functionalized polymers was examined in detail. Moreover, key applications in diagnosing diseases, including asthma, chronic kidney disease, lung cancer, and diabetes, were highlighted through detecting specific biomarkers. Furthermore, current challenges related to sensor selectivity, stability, and interference from environmental humidity were discussed, and potential solutions were proposed. Future perspectives were offered on the development of next-generation polymer-based sensors, including the integration of machine learning for data analysis and the design of electronic-nose (e-nose) sensor arrays. Full article

Octachlorinated metal phthalocyanines (MPcCl₈, M = Co, Zn, VO) represent an underexplored class of functional materials with promising potential for chemiresistive sensing applications. This work is the first to determine the structure of single crystals of CoPcCl₈, revealing a triclinic (P-1) packing motif with cofacial molecular stacks and an interplanar distance of 3.381 Å. Powder XRD, vibrational spectroscopy, and elemental analysis confirm phase purity and isostructurality between CoPcCl₈ and ZnPcCl₈, while VOPcCl₈ adopts a tetragonal arrangement similar to its tetrachlorinated analogue. Thin films were fabricated via physical vapor deposition (PVD) and spin-coating (SC), with SC yielding highly crystalline films and PVD resulting in poorly crystalline or amorphous layers. Electrical measurements demonstrate that SC films exhibit n-type semiconducting behavior with conductivities 2–3 orders of magnitude higher than PVD films. Density functional theory (DFT) calculations corroborate the experimental findings, predicting band gaps of 1.19 eV (Co), 1.11 eV (Zn), and 0.78 eV (VO), with Fermi levels positioned near the conduction band, which is consistent with n-type character. Chemiresistive sensing tests reveal that SC-deposited MPcCl₈ films respond reversibly and selectively to ammonia (NH₃) and hydrogen sulfide (H₂S) at room temperature. ZnPcCl₈ shows the highest NH₃ response (45.3% to 10 ppm), while CoPcCl₈ exhibits superior sensitivity to H₂S (LOD = 0.3 ppm). These results suggest that the films of octachlorinated phthalocyanines produced by the SC method are highly sensitive materials for gas sensors designed to detect toxic and corrosive gases. Full article

DFT study of graphene functionalized via carbene was performed to identify the preferred –OH adsorption sites and to assess how hydroxylation affects adsorption of NH₃ gas. The carbene attaches to the graphene basal plane through a [2+1] cycloaddition, producing a local cyclopropane-like motif with a C–C bond. This modification introduces localized mid-gap states and asymmetric charge redistribution that create chemically active anchoring sites for –OH groups. We systematically scanned possible –OH adsorption sites and identified site-dependent binding energies. NH₃ preferentially anchors at the carbene center and is further stabilized by multidentate hydrogen bonding with neighboring –OH groups. Calculated NH₃ adsorption energies range from moderate values (single –OH and some two –OH symmetric sites, E_ads ≈ −0.64 to −0.75 eV) to strong interaction for selected through-plane two –OH pairs (E_ads ≈ −1.78 to −1.83 eV), where synergistic hydrogen bonding amplifies the NH₃ interaction. Charge density difference and Bader analyses indicate polarization-dominated binding with minimal net charge transfer, consistent with hydrogen bonding rather than covalent bond formation. Desorption time estimation shows that moderate binding motifs provide rapid recovery at room temperature. We conclude that targeted placement of paired –OH groups on carbene-functionalized graphene offers a tunable route to balance sensitivity and reusability for NH₃ sensing. Full article

The development of highly sensitive gas sensors for toxic industrial gases (TIGs) is paramount for environmental monitoring and public safety. Here, the first-principles calculations were employed to systematically investigate the potential of Pt- and Rh-decorated InS (Pt-InS and Rh-InS) monolayers as advanced gas sensing materials for the five TIGs (SO₂, NH₃, NO, CO, and NO₂). The results reveal that Pt and Rh atoms can be stably anchored at the InS monolayer, inducing significant modulation of its electronic properties. The Pt-InS system exhibits strong chemisorption of NH₃ and CO, while the other TIGs interact via physisorption. In contrast, the Rh-InS monolayer demonstrates strong chemisorption and distinct electronic responses to all five gases, driven by robust hybridization between the Rh-d and TIG-p orbitals. Based on comprehensive analyses of sensitivity and recovery time, Rh-InS is identified as a theoretically promising candidate for a reusable SO₂ sensor at room temperature, boasting a calculated rapid theoretical recovery time of 2.20 s. The Pt-InS system, conversely, shows potential for high-temperature NH₃ sensing. Our findings highlight the exceptional and tunable gas sensing capabilities of Pt- and Rh-decorated InS monolayers, offering a theoretical foundation for designing InS-based sensing devices. Full article

This study is devoted to the determination of the role of aerosol spraying in the formation of NO₂ sensor properties of carbon nanofiber (CNF)-based films. This is the first paper to systematically apply the aerosol spraying technique to CNF-based films and link the spraying parameters directly to sensor performance metrics (response, signal-to-noise ratio, response times, etc.). Chemiresistive gas sensors were created based on CNFs and tested at room temperature (25 ± 1 °C). It has been shown that the increase in the concentration of the CNF/ethanol mixture used for spraying from 3 to 30 mg/mL led to a growth in sensor response from 1.2% to 12.0% at 2 ppm NO₂. The increase in the thickness of the CNF film of the sensor induced a growth in ΔR/R₀ to NO₂ that is attributed to the formation of a porous film. With increased film thickness, the response improves (from 7.0% to 10.6% at 2 ppm NO₂) as does the signal-to-noise ratio (from 735:1 to 1892:1). The creation of hybrid all-carbon composites based on CNFs and multi-walled carbon nanotubes (MWCNTs) resulted in a decrease in both sensor response and signal-to-noise ratio; however, the response time and recovery degree improved. Two types of hybrid materials based on CNFs and MWCNTs were created using aerosol spraying to enhance the sensor behavior of CNFs. The obtained data confirm the dominant role of the thickness of CNF-based films and their density (in terms of distance between nearest carbon inclusions within the film) in sensor characteristics. The machine learning data used to describe the sensing behavior of two gases with opposite resistance changes when in contact with CNFs, namely NO₂ and NH₃, showed final accuracies of 92.13% on training data and 91.98% on validation data. Full article

Ethylene glycol (EG) is a vital industrial raw material. However, it has the potential to be hazardous to the environment and human health. High operating temperatures and long response/recovery times limit the wide application of EG sensors. Thus, we need to develop high-performance room-temperature EG-sensing materials. This paper proposes the direct hydrothermal carbonization of magnolia hair to prepare porous microtubular carbon (CMH) for room-temperature EG sensing. SEM, TEM, and XPS characterization showed that the CMH exhibited a porous microtubular structure and contained Na, which enhanced the adsorption capacity of the CMH for ethylene glycol gas. The CMH sensor exhibits a high response (156.4) to 500 ppm ethylene glycol gas at room temperature with moderate response/recovery time (14.2/37.3 s). It exhibits good linearity in measuring EG gases in the 10–100 ppm range, with a 0.292 ppm theoretical detection limit. Additionally, CMH sensors provide excellent repeatability and long-term stability. The synergistic effect of microtubule porous structure and Na doping is the main reason for enhancing the response of the sensor to EG gas. On this basis, the gas-sensitive enhancement mechanism of CMH was analyzed. The results show that biomass carbon materials provide a new method to prepare high-performance EG gas sensors. Full article

This work comparably investigates the gas sensing potential of noble metal (Pd and Ru)-doped GeS₂ monolayers upon three C₄F₇N decomposed species (FCN, CF₃CN, and C₂F₄) using the first-principles theory, for operation status evaluation in C₄F₇N-insulated devices. The Pd- and Ru-doping effects on the pristine GeS₂ monolayer are analyzed, followed by the adsorption mechanism and sensing performance of two doped monolayers. Our results demonstrate that while Ru doping induces stronger surface interactions with the GeS₂ substrate and consequently exhibits superior adsorption strengths upon the three gases, the Pd-doped monolayer shows remarkable advantages in charge transfer capability that leads to exceptional room-temperature sensitivity responses of −99.6% (FCN), −95.0% (CF₃CN), and −88.0% (C₂F₄), thus significantly outperforming the Ru-doped system. Combined with the instantaneous recovery for gas desorption, the Pd-GeS₂ monolayer holds significance as an ideal room-temperature sensor to monitor the operation status of C₄F₇N-insulated devices in power systems. This research provides promising insights into the application of GeS₂-based materials for gas sensing in power systems and emphasizes the importance of dopant selection in designing high-performance gas sensing materials, especially for developing advanced electrical equipment monitoring technologies. Full article

Metal oxide semiconductor (MOS) gas sensors offer several advantages, including low cost, high accuracy, and ease of miniaturization. Thus, they are excellent candidates for environmental monitoring and food spoilage detection applications, particularly in the safe Internet of Things field or for portable instruments. Typically, there are two general routes for realizing low-power-consumption MOS gas sensors: room-temperature MOS gas sensors or MEMS MOS gas sensors. The review focuses on the detection of four typical gases, namely methane, hydrogen, carbon monoxide, and nitrogen dioxide, systematically summarizing and analyzing the most recent results of low-power-consumption MOS gas sensors. The 2D materials, MOS composites, and 3D structured composites exhibit excellent room-temperature gas detection capabilities. The mechanism of the room-temperature gas sensors is also discussed in detail. Another route is MEMS MOS gas sensors. First, the progress of the micro-hotplate research is introduced. Then, several of the latest reported MEMS MOS gas sensors are shown and compared. The gas sensing mechanism of these MEMS MOS gas sensors is also given. The paper will provide a valuable guide for researchers in the MOS gas sensor field, particularly for those working towards low-power-consumption MOS gas sensors. Full article

Zinc oxide (ZnO) nanomaterials have emerged as promising candidates for gas sensing applications due to their high sensitivity, fast response–recovery cycles, thermal and chemical stability, and low fabrication cost. However, the performance of pristine ZnO remains limited by high operating temperatures, poor selectivity, and suboptimal detection at low gas concentrations. To address these limitations, significant research efforts have focused on dopant incorporation and polymer hybridization. This review summarizes recent advances in dopant engineering using elements such as Al, Ga, Mg, In, Sn, and transition metals (Co, Ni, Cu), which modulate ZnO’s crystal structure, defect density, carrier concentration, and surface activity—resulting in enhanced gas adsorption and electron transport. Furthermore, ZnO–polymer nanocomposites (e.g., with polyaniline, polypyrrole, PEG, and chitosan) exhibit improved flexibility, surface functionality, and room-temperature responsiveness due to the presence of active functional groups and tunable porosity. The synergistic combination of dopants and polymers facilitates enhanced charge transfer, increased surface area, and stronger gas–molecule interactions. Where applicable, sol–gel-based studies are explicitly highlighted and contrasted with non-sol–gel routes to show how synthesis controls defect chemistry, morphology, and sensing metrics. This review provides a comprehensive understanding of the structure–function relationships in doped ZnO and ZnO–polymer hybrids and offers guidelines for the rational design of next-generation, low-power, and selective gas sensors for environmental and industrial applications. Full article

In this study, two types of gas sensors—silicone-based interdigital electrode and silicon micropillar sensors based on rGO and rGO/SnO₂—were fabricated. Their gas-sensing performance was investigated at room temperature. First, interdigital electrodes of different channel widths were fabricated to investigate the impact of the channel width parameter. Subsequently, the rGO/SnO₂ doping ratio in the composite material was varied to identify the optimal composition for gas sensitivity. Additionally, triangular and square-arrayed silicon micropillar substrates were fabricated via photolithography and inductively coupled plasma etching. The rGO/SnO₂-based gas sensor on a silicon micropillar substrate exhibited an ultra-high specific surface area. The triangular micropillar arrangement of rGO/SnO₂-160 demonstrates the best performance, showing approximately 14% higher response and a 106 s reduction in response time compared with interdigital electrode sensors spray-coated with the same concentration of rGO/SnO₂ when tested at room temperature under 250 ppm NO₂. The optimized sensor achieves a detection limit as low as 5 ppm and maintains high responsiveness, even in conditions of 60% relative humidity (RH). Additionally, the repeatability, selectivity, and stability of the sensor were evaluated. Finally, structural and morphological characterization was conducted using XRD, SEM, TEM, and Raman spectroscopy, which confirmed the successful modification of rGO with SnO₂. Full article

As industrial waste gas, nitrogen dioxide (NO₂) is a serious hazard to air pollution and human health, and there is a pressing demand for developing high-performance NO₂ gas sensors. Tin disulfide (SnS₂), a representative two-dimensional metal sulfide characterized by a significant specific surface area, a suitable electron band gap, and an easily tunable layered structure, shows a broad application prospect in gas sensing applications. Nevertheless, SnS₂-based gas sensors suffer from poor sensitivity, which seriously hinders their application in room temperature gas sensing. In this study, Ag/SnS₂ heterojunction nanomaterials were synthesized by an in situ reduction approach. The findings reveals that the gas-sensitive response of the Ag/SnS₂ nanocomposites at room temperature under visible light irradiation can achieve 10.5 to 1 ppm NO₂, with a detection limit as low as 200 ppb, which realizes the room-temperature detection of Sub-ppm NO₂. Meanwhile, the sensor exhibits good selectivity, reproducibility (cyclic stability > 95%). The improved gas sensitivity of the Ag/SnS₂ sensor can be due to the synergistic effect of the carrier separation at the Ag/SnS₂ Schottky junction and the localized surface plasmon resonance (LSPR) of Ag nanoparticles. The LSPR effect significantly enhances light absorption and surface-active site density, facilitating trace NO₂ detection at room temperature. This study provides the foundation for the subsequent development of room temperature layered metal sulfide gas sensors. Full article

The prompt and reliable detection of NH₃ leakage at room temperature (RT) is considered important for safety assurance and sustainable production. Although chemiresistive NH₃ sensors feature low cost and structural simplicity, their practical application is hindered by high operating temperatures and inadequate selectivity. Metal–organic frameworks (MOFs) and their derivatives offer a promising approach to address these limitations. In this work, Ce-BDC precursors with tunable particle sizes and crystallinity were synthesized by adjusting the raw material concentration. Controlled pyrolysis yielded a series of CeO₂-C-X (X = 0.5, 1, 1.5, 2) materials with nanosized particles. Among them, the CeO₂-C-1 sensor delivered a high response of 82% toward NH₃ under 40% relative humidity at RT. Moreover, it possessed excellent selectivity, repeatability, and rapid response-recovery behavior compared with the other samples. CeO₂-C-1 also remained stable under varying oxygen and humidity conditions, demonstrating high applicability. The superior sensing properties may be attributed to its high specific surface area and optimized mesoporous structure, which facilitated efficient gas adsorption and reaction. These findings demonstrated that precise control of MOF precursors and the structure in CeO₂ nanomaterials was critical for achieving high-performance gas sensing and established Ce-MOF-derived CeO₂ as a promising sensing material for NH₃ detection at RT. Full article